What is gasoline made of, what is the octane number. Boiling, combustion and flash point of gasoline Boiling point of gasoline ai 92

The range and quality of gasoline produced and used is determined by the structure of the country’s automobile fleet (over the last decade, the number of cars has increased 1.7 times, while the share of foreign cars has increased), the technical capabilities of the domestic petrochemical industry, as well as environmental requirements, which have recently become decisive. In order to reduce harmful emissions, cars began to be equipped with catalytic systems for neutralizing exhaust gases, which caused stricter requirements for the quality of gasoline used.

1. Production of motor gasolines and their component composition

The production of fuel for internal combustion engines is a complex process that includes obtaining its primary components, mixing them and improving them with additives to commercial quality in accordance with the requirements of the standards. The mixing of straight-run fractions with components of secondary processes and additives is called compounding.

Motor gasolines of the same brand, produced at different enterprises, have slightly different compositions, which is associated with a different set of technological equipment. However, they must comply with regulatory documentation. The average component composition of gasoline of different brands is given in table. 3.

The basic component for the production of motor gasoline is usually catalytic reforming or catalytic cracking gasoline. Catalytic reforming gasolines are characterized by low sulfur content, they contain virtually no olefins, so they are highly stable during storage. However, the increased content of aromatic hydrocarbons in them is a limiting factor from an environmental point of view. Their disadvantages also include the uneven distribution of detonation resistance among fractions.

In the Russian gasoline stock, the share of the catalytic reforming component exceeds 50%.

Table 3.Average component composition of gasoline of different brands

Catalytic cracking gasolines are characterized by a low mass fraction of sulfur and research octane numbers of 90...93. The content of aromatic hydrocarbons in them is 30...40%, olefinic hydrocarbons - 10...25%. They have relatively high chemical stability (induction period 800...900 min). Compared to catalytic reforming gasolines, catalytic cracking gasolines are characterized by a more uniform distribution of detonation resistance among fractions. Therefore, a mixture of catalytic reforming and catalytic cracking components is used as a base for the production of motor gasoline.

2. Requirements for the quality of motor gasoline

The power of a gasoline engine, its efficiency, operational reliability, fuel and oil consumption, and exhaust gas toxicity largely depend on the quality of the fuel used.

Motor gasolines are mixtures of straight-run gasoline distillates, thermal cracking, platforming and catalytic cracking. As the processes of catalytic cracking and reforming improve, the share of distillates from these processes in motor gasoline increases due to a decrease in the share of straight distillates and thermal cracking.

To ensure reliable operation of automobile engines in all modes, gasoline must meet certain requirements.

The combustion of gasoline mixed with air in the combustion chamber must occur at a normal speed without detonation in all engine operating modes in any climatic conditions. This requirement sets standards for the knock resistance of gasoline. In order to improve anti-knock properties, anti-knock additives - anti-knock agents - are added to some gasolines. In gasolines intended for engines with high degree compression, add various high-octane components.

It is necessary that gasoline has a high calorific value, a minimum likelihood of deposits forming in the fuel and intake systems, as well as carbon deposits in the combustion chamber. Combustion products must not be toxic or corrosive. The volatility of gasoline must ensure the preparation of a combustible mixture at any engine operating temperature. This requirement regulates such properties and quality indicators of gasoline as fractional composition, saturated vapor pressure, and the tendency to form vapor locks. To improve the starting properties of the engine, gas gasoline is added to gasoline.

The production of motor gasoline is associated with a complex set of various technological processes oil refining.

Requirements for the quality of produced gasoline, determined by the technical capabilities of domestic oil refining, impose restrictions on the parameters of fractional and hydrocarbon composition, sulfur content and various anti-knock agents.

Conditions mass production require the possibility of using petroleum feedstocks with the widest variation in hydrocarbon and fractional composition and the content of various sulfur compounds, which in a certain way influences the establishment of standards in specifications for the corresponding quality indicators of gasoline.

In order to increase the yield of gasoline from processed petroleum feedstock, production is interested in increasing the boiling point, and efficient use gasoline in the engine is possible with a certain limitation on the content of high-boiling fractions.

Standards for detonation resistance are set at a level achievable using existing technological processes, components and additives approved for use in gasoline.

The requirements of automobile manufacturers very often conflict with the requirements of oil refiners, and in these cases it is necessary to determine the optimal economically feasible level of these requirements. An example of such a compromise is the octane index, which characterizes the knock resistance of American gasoline.

US automakers proposed to include in the specification an assessment of the octane number of gasoline using the research method, and oil refineries - using the motor method. As a result, an indicator equal to half the sum of octane numbers according to the research and motor methods was entered.

The requirements associated with the transportation and storage of gasoline are determined by the need to maintain their quality for several years.

Motor gasoline is supplied from the manufacturing plant to large regional oil transshipment depots. From these storage bases, gasoline is supplied to oil depots that supply gas stations(gas station), and then by automobile tanks to the gas station.

Transportation, storage and use of gasoline directly on cars are carried out in various climatic conditions at ambient temperatures from –50 to 45 ° C, and it is necessary to ensure normal work engine. Requirements related to transportation and storage regulate such properties of motor gasoline as physical and chemical stability, tendency to losses from evaporation and the formation of vapor locks, water solubility, content of corrosive compounds, etc. As a rule, summer-type gasolines with high chemical stability (induction period of at least 1200 minutes) are supplied for long-term storage.

The impact of gasoline on the environment when used in automotive technology is associated with the toxicity of compounds entering the atmospheric air, water, and soil directly from the fuel (evaporation, leakage) or with its combustion products.

The sources of toxic vehicle emissions are exhaust gases, crankcase gases and fuel vapors from the intake system and fuel tank. Exhaust gases contain carbon monoxide, nitrogen oxides, sulfur oxides, unburned hydrocarbons and products of their partial oxidation, elemental carbon (soot), combustion products of various additives, for example lead oxides and lead halides when using leaded gasoline, as well as nitrogen and oxygen not spent on fuel combustion air.

To reduce emissions of harmful substances, modern cars are equipped with catalytic exhaust gas neutralization systems, which allow unburned hydrocarbons and carbon monoxide to be burned to CO 2, and nitrogen oxides to be reduced to nitrogen.

The environmental properties of gasoline are ensured by restrictions on the content of individual toxic substances, on the group hydrocarbon composition, on the content of low-boiling hydrocarbons, as well as sulfur and benzene. These restrictions ensure reliable operation of the catalytic exhaust gas aftertreatment system and help reduce environmental pollution.

In table Table 4 shows the requirements for motor gasoline in the countries of the European Economic Community (EEC).

In connection with the accession Russian Federation and the Republic of Belarus to European environmental programs, there is an urgent need to organize industrial production motor gasolines that meet European requirements (EN 228). The technology for the production of motor gasoline that meets the requirements of EURO-2, EURO-3, EURO-4, EURO-5 must guarantee the established standards for the content of sulfur, aromatic and olefinic hydrocarbons and benzene.

Table 4Requirements for motor gasolines of the European Union

Thus, gasoline as fuel should:

• have good volatility and form a combustible mixture that is uniform in composition in all cylinders;
• have high detonation resistance, i.e. burn without detonation under various engine operating conditions;
• ensure easy starting and stable operation of the engine in various modes, high efficiency;
• have an optimal fractional composition;
• have a low content of resin- and soot-forming compounds and corrosive substances;
• have high physical and chemical stability during storage, transportation, etc., not cause corrosion of containers, refueling means, engines (gasoline combustion products should also not cause corrosion of engine parts);
• burn completely with minimal formation of toxic and carcinogenic substances;
• have a minimal tendency to form carbon deposits on engine parts;
• provide maximum engine power and minimum consumption oils;
• have good low-temperature properties;
• do not have increased hygroscopicity and a tendency to form ice;
• do not contain mechanical impurities and water.

The properties of gasolines that fully meet all operational requirements include: physical Chemical properties, volatility and fractional composition, detonation resistance, their stability and anti-corrosion properties. Environmental requirements are included in a separate group of gasoline properties.

3. Chemical and hydrocarbon composition of gasoline

The chemical composition of gasoline is characterized by its group hydrocarbon composition, i.e. their content of aromatic, olefinic, naphthenic and paraffin hydrocarbons.

In addition to hydrocarbons, gasoline contains small amounts of heteroatomic hydrocarbon compounds, which include sulfur, oxygen and nitrogen. They enter gasoline from refined oil, and oxygen compounds are formed during the oxidation of hydrocarbons during gasoline storage.

Gasoline components do not contain organometallic compounds of petroleum, which are concentrated, as a rule, in high-boiling fractions. In order to improve the physicochemical and operational properties of motor gasoline, oxygen-containing components (ethers and alcohols), as well as special anti-knock additives, including metal-containing ones, are added to their composition in limited quantities.

To limit the content of anti-knock additives, the specifications for gasoline provide for maximum permissible concentrations of lead, manganese, and iron.

The main restrictions on the chemical and hydrocarbon composition of motor gasoline include: the content of sulfur, aromatic hydrocarbons, and primarily benzene; content of olefin hydrocarbons, oxygenates (total oxygen concentration and individual alcohols and ethers).

With an increase in the content of sulfur compounds in gasoline, increased carbon formation and wear of engine parts and aging of the engine oil occur. In addition, it has a significant negative impact on the environment.

An increase in the content of aromatic hydrocarbons in gasoline contributes to an increase in benzene emissions into the environment. The studies carried out have established that there is a linear relationship between the benzene content in gasoline and its concentration for all types of emissions of unburned hydrocarbons: in exhaust gases; in evaporations from the fuel system; when refueling the car. For vehicles not equipped with a catalytic converter, the main source of benzene emissions into the atmosphere is exhaust gases (about 70%), followed by evaporative emissions (20%) and losses during refueling (10%) to an even lesser extent.

• cutting from catalytic reforming gasoline a fraction of 60...85 °C containing more than 20% benzene, followed by its use to produce benzene. At the same time, the benzene content in commercial gasoline decreases by almost 3 times, and the octane characteristics of reformed gasoline after separation of the 60...85 °C fraction increases by 1...1.5;
• an increase in the proportion of high-octane components that do not contain benzene in the composition of commercial gasoline: alkylate, isomerates, oxygenates (alcohols, ethers, etc.), as well as the use of non-toxic anti-knock agents;
• selection of raw materials and reduction of the severity of the reforming process, extraction, as well as selective hydrogenation of benzene in cyclohexane or alkylation of benzene into alkyl aromatic hydrocarbons.

A combination of several methods is possible based on the characteristics of the oil refinery, the availability of raw materials, the processing concept and integration with chemical production.

The maximum content of olefin hydrocarbons in commercial gasoline should not exceed 18%, since they are the main source of the formation of tarry substances in gasoline. An increase in the content of olefinic hydrocarbons increases emissions of harmful substances into the environment with exhaust gases.

Oxygenates have high detonation resistance, which allows them to replace aromatic hydrocarbons, and they also help reduce the toxicity of vehicle exhaust gases. However, when the content of oxygenates in gasoline is more than 2.7% oxygen, an increase in mass and specific fuel consumption is observed due to their low calorific value, as well as a loss of engine power. Therefore, for environmental reasons, the content of oxygenates in gasoline should be 2.0...2.7% oxygen.

The specifications for motor gasoline also include standards for the maximum content of individual oxygenates.

4. Physico-chemical properties of gasolines

The physicochemical properties of motor gasoline and engine control parameters must be carefully linked to each other.

The physical and chemical properties of motor gasoline are assessed by their appearance, the presence of mechanical impurities, water-soluble acids and alkalis, as well as their density. In the same group of operational requirements for fuels, the low-temperature properties of gasoline are also considered.

By the appearance of gasoline, its color and transparency are assessed. Gasolines are colorless. The possible yellowish tint of gasoline is due to the presence of resinous substances in it.

The transparency of gasoline in accordance with GOST is determined in a glass cylinder. Gasoline poured into the cylinder must be completely transparent and must not contain foreign impurities, including water, suspended and deposited at the bottom of the cylinder. The turbidity of gasoline at room temperature is usually associated with the presence of water (in the form of an emulsion) or mechanical impurities. Such fuel is subjected to sedimentation and filtration before use. The presence of water in gasoline is especially dangerous in winter, when the resulting ice crystals disrupt the dosage of gasoline and can even cause a complete stop in its supply. In addition, water increases the corrosiveness of gasoline towards metal parts of fuel systems.

The specification for gasoline stipulates that it contains no water. However, water in gasoline can be dissolved, and can also enter fuel containers and accumulate in them in a free state. The amount of free water depends on the conditions of transportation and storage. Therefore, for the reliable operation of equipment, storage tanks and means of pumping gasoline, it is important that they not only are not aggressive themselves, but also have the ability to reduce the rate of electrochemical corrosion in the fuel-metal-water system.

Mechanical impurities can get into gasoline when using dirty or faulty (leaky) containers or contaminated refueling equipment. The presence of mechanical impurities is determined by external inspection of a gasoline sample also in a glass container. The presence of even the smallest mechanical impurities in gasoline is not allowed. The use of gasoline containing mechanical impurities causes wear of fuel equipment, clogging of fuel metering systems, and when it enters the engine cylinders, wear of the engine cylinder-piston group.

During use, motor gasoline comes into contact with various metals and alloys, causing their corrosive destruction. Fuel tanks, pipelines, etc. are subject to corrosion.

Water-soluble acids and alkalis, which cause corrosive wear of engine parts, may end up in gasoline due to violations of its purification technology. Thus, after sulfuric acid purification, it is possible that gasoline contains residues of both the acid itself and its derivatives (sulfonic acids and acid esters) due to their incomplete neutralization. Alkali gets into gasoline when it is poorly washed during the cleaning process. Thus, organic acids remain in gasoline after oil refining, and are also formed during the oxidation process during storage, and their content increases from the moment gasoline is produced to its consumption.

Organic acids are especially destructive to non-ferrous metals - lead and zinc. Acids, interacting with metals, form gasoline-insoluble soaps, which precipitate in the form of clots, clogging the engine power system.

Sulfur compounds contained in gasoline are conventionally divided into active and inactive. Active compounds include elemental sulfur, hydrogen sulfide, mercaptans, and inactive compounds include sulfides, disulfides, etc. Active sulfur compounds corrode metal even at low temperatures, so their presence in gasoline is unacceptable.

By themselves, inactive sulfur compounds found in gasoline do not cause corrosion of metals. The combustion products of sulfur compounds - sulfur and sulfur dioxide anhydrides - are highly corrosive. When starting the engine, especially in the cold season, at a relatively low temperature of the combustion products, condensation of water vapor resulting from fuel combustion is possible. Anhydrides dissolve in water, forming sulfuric and sulfurous acids. Under the influence of these acids, low-temperature liquid corrosion of metals occurs. If the temperature of the combustion products is high enough, then water vapor does not condense, but high-temperature gas corrosion occurs. Sulfur oxides in exhaust gases cause corrosion of the exhaust system. Corrosive wear largely depends on its technical condition, oil quality, operating conditions and the amount of sulfur contained in the fuel. When the sulfur content in gasoline increases from 0.05 to 0.1%, corrosive wear of engine parts increases by 1.5–2.0 times, from 0.1 to 0.2% by another 1.5–2.0 times , from 0.2 to 0.3% - 1.3–1.7 times.

The process of removing sulfur from gasoline is very labor-intensive and expensive. Therefore, some of the sulfur compounds, mostly inactive, are usually left in the fuel in an amount that does not affect engine wear.

The maximum sulfur content in domestic motor gasoline is regulated by STB ISO 20846–2005 and should be no more than 50 mg/kg.

5. Fuel stability, tendency to form deposits and carbon deposits

Under fuel stability understand its ability to retain properties in permissible limits for specific operating conditions. The stability of fuels depends on their physicochemical properties, the presence of various impurities, etc. Under operating conditions, when the fuel is exposed to external factors such as atmospheric oxygen, unstable temperature, contamination with moisture and mechanical impurities, its fractional and chemical composition deteriorates. Conventionally, a distinction is made between physical and chemical stability of fuel.

Physical Stability fuel determines its ability to maintain its fractional composition (changes are caused by the loss of the lowest boiling fractions as a result of their evaporation) and homogeneity.

The physical stability of gasoline is assessed by saturated vapor pressure and the presence of light fractions. The lack of physical stability of gasoline causes its high volatility.

The design of fuel tanks must exclude the possibility of free communication of their internal volume with the atmosphere.

To prevent evaporation, fuel tanks are protected from direct sunlight.

The physical stability of the fuel is monitored by periodically determining density, fractional composition, saturated vapor pressure, cloud point and crystallization temperature, and other indicators.

Chemical stability characterizes the ability of gasoline to retain its original chemical composition without changes when long-term storage, pumping and transportation. The chemical stability of gasoline is associated, first of all, with the presence of unsaturated hydrocarbons in their composition, which are characterized by an increased tendency to oxidize. Hydrocarbons that have conjugated double bonds, especially cyclic ones, are most prone to oxidation. Aromatic hydrocarbons with a double bond in the side chain are also poorly resistant to oxidation.

Gasoline produced by thermal and catalytic cracking, coking, pyrolysis and containing a lot of olefin and diolefin hydrocarbons are most prone to oxidation. Gasolines obtained by catalytic reforming and direct distillation, as well as alkyl gasoline, are more chemically stable.

Along the route from the manufacturer to the car tank, auto-oxidation of gasoline occurs, i.e. oxidation of its unstable compounds by oxygen of the surrounding air with the formation of products of complex composition. The longer gasoline is stored, the longer the transportation route and the more transshipment points, the greater the possibility of the formation of oxidation products - resinous substances and various acidic compounds (organic acids, hydroxy acids, etc.). Most of the resulting oxidation products are in a dissolved state in gasoline, and a smaller part precipitates. The oxidation of gasoline is accelerated by various sludges and sediments accumulating in tanks, as well as due to the catalytic effect of metals (for example, copper). The more unsaturated hydrocarbons gasoline contains, the faster it oxidizes. Oxidation changes the color of gasoline. For example, unleaded gasoline takes on a color ranging from light yellow to intense yellow. A pungent odor appears, an oil layer is formed at the bottom of the tank, slightly soluble in gasoline, the acidity of gasoline increases, i.e. its corrosivity increases.

Chemical stability is characterized by the following indicators:

• induction period;
• actual resin content;
• total amount of oxidation products;
• acidity.

The acidity and content of actual resins characterize the content in gasoline final products oxidation at the time of their determination. Based on them, one can judge the quality reserve of gasoline, i.e. about the difference between the permissible and actual content of oxidation products. The induction period and the amount of oxidation products characterize the rate of oxidation of gasoline during storage and use.

Under long-term storage conditions, some of the compounds (sulfur, oxygen, nitrogen and organometallic) may enter into oxidation, polymerization and condensation reactions. Negative phenomena such as oxidation and tarring of gasoline, and the formation of antiknock sediment are caused by insufficient chemical stability of the fuel.

The content of actual resins is an indicator of the level of chemical stability of gasoline and is standardized by standards. To increase the chemical stability of gasolines, antioxidant additives (inhibitors) are introduced into them: wood-resin antioxidant DSA (0.05...0.15%), a mixture of phenols FCh-16 (0.03...0.10%), synthetic inhibitors - ionol (0.03...0.10%), agidol-1, agidol-12 (up to 0.3%).

The hydrocarbon composition of gasoline is one of the main factors determining their tendency to form carbon deposits in the engine. An analysis of the available data shows that the tendency of motor gasoline to form carbon deposits depends mainly on the content of unsaturated and aromatic hydrocarbons in them.

The structure of unsaturated hydrocarbons, their chemical activity and tendency to transform under the influence of high temperatures significantly determine the possibility of carbon formation with motor gasoline. The structure of aromatic

hydrocarbons has a significant impact on carbon formation. As the molecular weight of a hydrocarbon and its boiling point increase, the likelihood of carbon formation generally increases. High-boiling aromatic hydrocarbons undergo oxidative transformations under the influence of high temperatures and, obviously, serve as the main source of soot formation.

Aromatic hydrocarbons are valuable components of motor gasolines, as they have high detonation resistance. However, their content in commercial gasoline should be limited due to increased carbon formation in the engine. A direct comparison of the detonation resistance of gasolines and their tendency to form carbon deposits depending on the content of aromatic hydrocarbons made it possible to propose a standard for the content of aromatic hydrocarbons in commercial motor gasoline. It has been established that the specific increase in the amount of soot in the combustion chamber, i.e. the increase in carbon deposits as a result of adding aromatic hydrocarbons in an amount corresponding to an increase in the detonation resistance of the fuel by 1 octane unit remains practically unchanged for various aromatic hydrocarbons when their content in gasoline varies from 0% to 40...45%. With a higher content of aromatic hydrocarbons, the specific increase in the amount of soot increases sharply. Thus, the content of aromatic hydrocarbons in commercial motor gasoline should not exceed 40%.

Specifications EURO-3 and EURO-4 are also in mandatory determine the presence of detergent additives in motor gasoline that reduce the effects of carbon formation.

6. Compatibility of gasoline with non-metallic materials

Motor gasolines should not have a negative effect on materials with which they come into contact during manufacturing, transportation, storage and use. When rubber, seals and other materials are exposed to gasoline, they can swell, crack, lose their strength characteristics and collapse. The aggressive effect of fuel on rubbers and sealants is mainly associated with the leaching of the antioxidant from them and further destruction caused by the formation of peroxides during oxidative processes occurring in the fuel itself. In this regard, the compatibility of gasoline containing oxygenates with rubber materials is assessed based on the results of their direct impact on rubber. The essence of control comes down to determining the preservation of the properties of samples of rubber materials and the purity of the fuel during testing.

Changes in the physical and chemical properties of rubber under the influence of gasoline are determined by the change in:

• sample volume;
• relative elongation at break;
• sample tensile strength and Shore hardness.

Tests for the compatibility of gasoline with rubber materials are carried out when they are put into production.

7. Gasoline volatility

Gasoline is a complex mixture of a number of individual hydrocarbons that boil at different temperatures, so it does not have a fixed boiling point.

The volatility of gasoline, i.e. the ability to transition from a liquid to a gaseous state lies in the temperature range from 35 to 195 °C.

The volatility of gasoline is assessed by indicators of fractional composition and volatility (saturated vapor pressure, evaporation losses and the tendency to form vapor locks).

The volatility of gasoline must ensure the optimal composition of the air-fuel mixture in all engine operating modes, regardless of the method of its preparation. A homogeneous combustible mixture must be supplied to the engine cylinders, in which the concentration of fuel, in a vapor state and uniformly distributed throughout the volume, is sufficient to ignite it from an electric spark.

The speed and completeness of the transition of fuel from liquid to gaseous state depend on its chemical composition and external conditions, for example temperature, gas flow velocity. Since these conditions are not the same in different engines, the requirements for fuel volatility are related to the design of the engine for which it is intended. Combustion is always preceded by the evaporation of liquid fuel and mixing of its vapors with air (formation of a combustible mixture). With poor evaporation, part of the fuel does not go into a gaseous state and does not burn.

To assess fuel volatility, a conventional indicator is used - fractional composition. Starting, warm-up time, engine response and wear, fuel and oil consumption, and exhaust gas toxicity depend on the fractional composition of gasoline. Since motor gasoline is a complex mixture of various hydrocarbons that boil over a wide temperature range, its volatility is assessed by the boiling temperatures of individual parts - fractions.

In Fig. Figure 1 shows the gasoline distillation curve and indicates the volumes of its main fractions - starting, working and end. The distillation temperature of 10% gasoline characterizes the starting properties of the fuel. If there are not enough low-boiling fractions in gasoline, then when starting a cold engine, some of the gasoline does not have time to evaporate and enters the cylinders in a liquid state. The combustible mixture entering the cylinders turns out to be too lean and does not ignite from an electric spark, and therefore starting the engine sometimes becomes completely impossible.

Rice. 1.

Unevaporated gasoline, remaining in a drop-liquid state, enters the engine cylinders and washes away oil from their surface, and when it enters the crankcase, it dilutes the oil. Therefore, at the moment of start-up and for some time during subsequent warming up, semi-dry friction of the parts of the cylinder-piston group occurs, since there is not enough oil on their surfaces to ensure a strong oil film. This causes intense wear of the rubbing parts of the engine, called starting.

To ensure engine starting, the starting fraction must contain a sufficient amount of low-boiling hydrocarbons, which create a mixture that can ignite from an electric spark. Knowing the boiling point of 10% gasoline t 10%, you can approximately determine the air temperature tb, above which it is possible to start an engine using this fuel, using the formula

tв ≥ 0.5t 10% – 50.5. (8)

The starting properties of gasoline improve as the starting fraction becomes lighter. Winter gasoline makes it possible to start a cold engine at an air temperature of –26…–28 °C.

The starting temperature for distillation of summer grades of motor gasoline must be no lower than 35 °C, and 10% of gasoline must be distilled at a temperature no higher than 75 °C.

The distillation temperature of 50% gasoline characterizes the warm-up speed and throttle response of the engine. Warming up the engine lasts from the moment it is started until the start of uninterrupted, stable operation. At the end of warm-up at idle, almost complete evaporation of gasoline in the intake manifold is achieved. The lighter the fractional composition and the lower the distillation temperature of 50% gasoline, the faster the engine warms up. Gasoline with a low distillation temperature of 50% evaporates faster in the intake manifold, filling the cylinder with the combustible mixture improves, and engine power increases.

Saturated vapor pressure is determined by the presence of light fractions in gasoline. By saturated vapor pressure of liquid fuel we mean the pressure of vapors that are in a state of equilibrium with the liquid at a given temperature and a certain ratio of the volumes of the liquid and vapor phases. The more light fractions in gasoline, the higher the saturated vapor pressure.

The saturated vapor pressure determines the tendency of gasoline to form vapor locks, its possible losses during storage, transportation and refueling of a car, and the ease of starting the engine. The more hydrocarbons with a low boiling point in gasoline, the higher its volatility and saturated vapor pressure, and therefore the tendency to form vapor locks. The higher the saturated vapor pressure of gasoline, the greater the loss during storage, transportation, pumping, refueling and directly from the car tank. Saturated vapor pressure decreases with decreasing temperature and increasing ratio of vapor to liquid phases.

The value of saturated vapor pressure for gasoline of all types (STB EN 13016) should be in the range from 45 to 100 kPa. The reason for limiting the upper level of saturated gasoline vapor pressure is the possibility of formation of vapor locks, and the lower level is the deterioration of its starting properties.

The formation of vapor locks depends on the volatility of gasoline, temperature and engine design. The higher the saturated vapor pressure of gasoline, the lower the distillation temperature of 10% and the greater the volume of the fraction that boils away at temperatures up to 70 ° C, the greater its tendency to form vapor locks. This relationship is linear and can be expressed as follows:

IPP = 10DND + 7V 70°C, (9)

where IPP is the vapor lock index; DNP – saturated vapor pressure of gasoline, kPa; V 70 °C - the volume of gasoline that boils away at temperatures up to 70 °C.

The density and viscosity of gasoline are regulated parameters of its quality. The use of gasoline with a significantly reduced density can lead to an increase in its level in the carburetor float chamber and spontaneous leakage from the nozzle. The volatility of gasoline depends significantly on its density. Distinguish between absolute and relative density of a substance.

Absolute density substance (kg/m3) is the mass contained in a unit volume. The unit of density is taken to be the mass of 1 m3 of distilled water at a temperature of 4 °C.

Relative density a substance is the ratio of its mass to the mass of distilled water at 4 °C, taken in the same volume. Relative density is a dimensionless quantity.

Petroleum products and water have different expansion coefficients. In this regard, it is necessary to indicate the temperatures of the oil product and water at which their density was determined. The relative density of petroleum products is determined at a temperature of 20 °C. The density of a petroleum product can be measured at any temperature, but the result is based on a temperature of 20 or 15 °C. In foreign and some domestic standards, density limits are set at 15 °C.

In accordance with current standard The density of the petroleum product is designated 20. Here, the number 20 indicates that the density of the petroleum product is referred to a normal temperature of 20 °C, and the number 4 means that the density of the petroleum product is referred to the density of water at 4 °C, taken as one.

The relative density of motor gasoline is 0.70...0.78, and the absolute density in the SI system is 700...780 kg/m3 at 20 °C.

Density is not standardized in fuel standards, but it is mandatory to determine it. This is necessary to account for the consumption and movement of petroleum products at oil warehouses and gas stations, since the arrival is recorded in units of mass (kg, t), and the consumption when refueling tractors and cars is taken into account in units of volume (l). Therefore, to convert fuel from units of mass to units of volume and vice versa, you need to know the density of the petroleum products received and released.

The density of gasoline increases by approximately 1% with every 10 °C decrease in temperature.

The density (kg/m3) of gasoline is determined at 15 °C in accordance with STB ISO 3675–2003 and STB ISO 12185–2007.

The low-temperature properties of gasoline should not affect the performance of fuel systems at subzero temperatures. At low temperatures, the supply of gasoline to the engine may be interrupted due to the formation of ice crystals or the formation of ice deposits on parts of the carburetor and intake system (carburetor icing). Since most of the hydrocarbons that make up gasoline solidify at very low temperatures, and the pour point of motor gasoline is below –60 ° C, this indicator is not regulated for them.

The greatest complications when operating an engine at low temperatures are associated with the formation of ice crystals in gasoline. Gasoline may contain only a few hundredths of a percent of water (in a dissolved state). At high humidity and positive temperatures (parking a car in a warm, humid, poorly ventilated garage), the water content even in dehydrated gasoline almost instantly reaches its maximum value. When gasoline is rapidly cooled, the moisture that has not had time to enter the air is released in the form of small droplets, which at subzero temperatures turn into ice crystals. These crystals clog fuel filters and pipes and interfere with the flow of gasoline to the engine. In addition, the water contained in leaded gasoline leads to the decomposition of tetraethyl lead, which significantly increases the corrosiveness of gasoline.

The solubility of water in gasoline improves with an increased content of aromatic hydrocarbons, in particular benzene. Therefore, to reduce the risk of ice crystals forming when cooling gasoline, the content of aromatic hydrocarbons in them, including benzene, is limited.

If you suspect the presence of water in the fuel tank of a car, as well as for preventive purposes, its owner (driver) can add one of the special drugs that “bind” water to gasoline. At the nominal dosage, these drugs, as a rule, do not affect the condition of engine parts and its operation.

8. Anti-knock properties

One of the main indicators of the quality of motor gasoline is their resistance to detonation, on which reliability, increased power, efficiency and service life of a car engine largely depend.

As an indicator of the anti-knock properties of gasoline, called the “octane number,” the content of isooctane in a mixture with normal heptane, which is equivalent in its anti-knock qualities to the tested fuel, is taken.

Different structures of hydrocarbons with close physical properties causes a sharp difference in their detonation resistance. The octane number of isooctane (C 8 H 18) - a paraffin hydrocarbon of isomeric structure, characterized by high detonation resistance (begins to detonate only in engines with a very high compression ratio) - is taken to be 100 units. The octane number of highly detonating heptane C 7 H 16 - a paraffin hydrocarbon of normal structure - is taken as 0 units.

By composing mixtures of isooctane with normal heptane in volume percentages, it is possible to obtain standard mixtures with detonation resistance from 0 to 100 units.

Various domestic and foreign-made octane meters that have appeared recently, operating on the principle of measuring dielectric constant and hydrocarbon composition, have nothing in common with engine installations on which the octane numbers of gasoline are determined.

The detonation resistance of motor gasoline is determined using single-cylinder units. When finding octane numbers using the motor method (GOST 511–82), UIT-85 or IT9-2M units are used, which allow testing with a variable compression ratio (from 4 to 10 units). They compare the detonation resistance of the gasoline under study with a reference fuel, which contains two hydrocarbons: isooctane and normal heptane. A mixture of isooctane and normal heptane has an octane number equal to the percentage (by volume) of isooctane in it.

The intensity of detonation is measured and recorded with a special device - a detonometer.

In practice, it has been found that the octane number, determined by the motor method, correlates with the detonation requirements of full-size engines when operating at maximum power and strain. thermal mode and does not fully reflect the entire characteristics of the detonation resistance of motor gasoline under operating conditions. In this regard, a research method was developed for determining octane numbers, which characterizes the knock resistance of motor gasoline under conditions of engine operation at partial load and lower thermal stress (city driving). Using the research method (GOST 8226–82), the detonation resistance of gasoline is determined using UIT-65 or IT9-6 installations (the IT9-6 installation allows you to determine octane numbers using both methods) of domestic production and installations from Waukesha (USA). Moreover, detonation resistance is determined in the operating mode of a passenger car when driving in a city. In this case, the letter I is included in the brand of gasoline, for example AI-95 - motor gasoline with a research octane number of at least 95.

The difference between the octane numbers according to the research and motor methods of the same gasoline is 7...10 units (with the research method the octane number is higher) and is called sensitivity. The lower the sensitivity, the better the anti-knock properties of gasoline. For example, one gasoline AI-95 has an octane number, according to the research method, equal to 95, and according to the motor method - 86, and the second gasoline - 95.6 and 85, respectively. The sensitivity in the first case is less and, therefore, the anti-knock properties are better.

Octane number (ON), approximately corresponding to the octane number according to the research method, can be determined by the formula

(10)

where t cf is the average fuel acceleration temperature, °C; ρ 4 20 - fuel density at a temperature of 20 °C.

The average fuel acceleration temperature is determined by the formula

(11)

where t n.r - temperature of the start of fuel acceleration, °C; t k.r - temperature of the end of fuel acceleration, °C.

The obtained octane number value is compared with GOST standards for gasoline and a conclusion is drawn whether the octane number determined by a specific test method corresponds to GOST standards for a given brand of gasoline.

High-octane components (isooctane, alkyl gasoline, toluene, isopentane) or anti-knock agents are added to fuels whose anti-knock properties do not meet operational requirements. By adding 15...40% of high-octane components to base grades of fuel, gasoline with high detonation resistance is obtained.

Antiknock agents are called organometallic compounds, the addition of which in small quantities sharply increases the anti-knock properties of gasoline. The cheapest of them are tetraethyl lead (TES) or tetramethyl lead (TMS) in the composition of ethyl liquid. EFT and TMS are poisonous.

As an alternative to TES and TMS, manganese compounds, iron pentacarobonyl, iron dicyclopentadienyl, or ferrocene, and diisobutylene iron pentacarbonyl complex, as well as oxygen-containing compounds, are used to increase the detonation resistance of gasoline. Multifunctional additives and additives contain detergent, antioxidant, anti-corrosion and other components.

In Russia and abroad, methyl tert-butyl ether (MTBE) is widely used in the production of high-octane gasoline.

The anti-knock additive based on MTBE is not toxic, has a higher heat of combustion, mixes well with gasoline in any ratio, and is not aggressive to structural materials. With the addition of 10% MTBE, the octane number of gasoline increases by 2.1...5.8 (according to the research method), with the addition of 20% - by 4.6...12.6. In addition, when MTBE is introduced into gasoline in an amount of 11%, the minimum cold start temperature of the engine is reduced by 10...12 °C. The maximum permissible content of MTBE (TU 103704–90) or its mixture “Feterol” (TU 301-03-130–93) in domestic gasoline is 15%. However, production of MTBE is planned to be reduced, although it does not pose a health threat. The reason is that MTBE easily penetrates into groundwater and has an unpleasant odor. It is found in small quantities in many water supplies.

Compositions containing manganese and iron are also used as anti-knock additives. They have high anti-knock properties and are less toxic compared to thermal power plants. However, gasolines with manganese antiknock agents (MTsTM, MCTM) form deposits on the surfaces of spark plugs and afterburner catalysts, reducing their efficiency. In addition, manganese compounds, when inhaled, have a neurotoxic effect and, when used en masse in places where cars accumulate in closed parking lots or in repair areas, can exceed the maximum permissible concentration.

The standard for motor gasoline GOST R 51105–97 provides for the production of “Normal-80” and “Regular-91” gasoline with a manganese content of 50 and 18 g/dm3, respectively.

Iron-containing additives (ferrocenes) are non-toxic, relatively cheap and effective, but cause increased wear of engine parts, intense carbon formation and deposition of varnish films. At ferrocene concentrations of up to 40 mg/kg, the wear rate of parts decreases, but remains higher than when using gasoline without additives. Ferrocene-based antiknock agents are approved for use if the iron content in gasoline of all brands is no more than 37 mg/dm3.

Based on the ever-increasing requirements for the reliability and environmental characteristics of engines, leaded gasoline is recognized as not meeting the technical level

to the EN 228 standard, therefore its production in Russia and other countries of the world has been discontinued. The use of gasoline with metal additives is considered as a temporary alternative to leaded gasoline.

Appendix 9 lists the most common anti-knock fuel additives.

9. Ecology of motor gasoline

Combustion products of motor fuels are one of the main air pollutants. As fuel consumption increases, the content in the air of the most toxic components of engine exhaust gases, such as lead compounds, nitrogen oxides, carbon monoxide, unburned aromatic hydrocarbons, especially benzene, increases. The solid product of incomplete combustion of fuels - soot - is also dangerous. The harmful effects of soot on humans are associated with the adsorption of many combustion products by its particles, which stimulate the formation of malignant tumors.

When burning gasoline, the most aggressive compounds in the exhaust gases are lead compounds, benzo(α)pyrene and nitrogen oxides. Gasoline vapors also pose a great threat to human health, the content of which in the atmosphere also increases with the increase in the production of petroleum products. Thus, the toxicity of exhaust gases and vapors of motor fuels depends on their hydrocarbon composition and the presence of various additives. It is possible to improve the quality of gasoline in order to increase the environmental safety of their use by optimizing the hydrocarbon and chemical composition of fuels. The guidelines for the development and implementation of gasolines with improved environmental performance are the European standards for gasoline EN 228, as well as the actual quality indicators of European fuels, which, as a rule, are higher than the norms regulated by international standards.

The quality of motor gasoline can be improved through the following measures:

• refusal to use lead compounds in gasoline;
• reducing the sulfur content in gasoline to 0.05%, and in the future - to 0.003%;
• reducing the content of aromatic hydrocarbons in gasoline to 45%, and in the future - to 35%;
• standardization of the concentration of actual tars in gasoline at the point of use at a level of no more than 5 mg per 100 cm3;
• dividing gasoline by fractional composition and saturated vapor pressure into 8 classes, taking into account the operating season of vehicles and the ambient temperature characteristic of a specific climatic zone. The presence of classes allows us to produce gasoline with properties that are optimal for real ambient temperatures, which ensures the operation of engines without the formation of vapor locks at air temperatures up to 60 ° C, and also guarantees high volatility of gasoline and easy engine starting at temperatures below –35 ° C;
• introduction of detergent additives that prevent contamination and tarring of fuel equipment parts.

Appendix 10 shows the requirements for environmental classes of motor gasoline in force in the territory of the Customs Union (TR CU 013/2011).

The concentration of actual tars in domestic gasoline at the place of production should not exceed 5 mg per 100 ml (GOST 31077–2002, STB 1656–2011). The actual tar content in gasoline, especially those supplied after many years of storage from the State Reserve, often exceeds this level, which contributes to the rapid tarring of fuel equipment parts.

The environmental friendliness of the use of automobile fuels is achieved by:

• improving the quality of gasoline to the level of the European standard for sulfur and benzene content. In the absence of lead, the environmental aggressiveness of exhaust gases is reduced by 4%;
• the use of MTBE, which reduces the aggressiveness of exhaust gases by 3% mainly due to the replacement of aromatic components of gasoline with an oxygen-containing additive and more complete combustion of fuel (CO reduction by 12%);
• the use of a detergent additive that reduces the aggressiveness of emissions by 5%.

The total reduction in aggressiveness due to all measures to improve the quality of gasoline is 12%, while the increase in the cost of producing gasoline with improved environmental performance is relatively small and does not exceed 5...8% of the cost of producing gasoline.

In accordance with STB 1656–2011 “Fuel for internal combustion engines. Unleaded Gasolines” in Belarus provides for the production of gasoline that meets the environmental requirements of European standards EN 228:2008.

US legislation has adopted amendments to the Clean Air Act, which, due to changes in environmental requirements for fuels after the ban on lead anti-knock agents, provide for a transition to the use of reformulated gasoline. In accordance with the adopted amendments, more stringent requirements have been put forward for gasoline in terms of the following indicators: saturated vapor pressure; fractional composition; content of aromatic hydrocarbons, benzene, olefins, sulfur. It is mandatory to add oxygen-containing compounds (at least 0.8% oxygen) and detergent additives to reformulated gasoline.

10. Assortment of gasolines

Currently, the following are in effect on the territory of the Republic of Belarus: regulations, which determine the properties of motor gasoline:

• STB 1656–2011 “Fuel for internal combustion engines. Unleaded gasolines";
• GOST 31077–2002 “Fuel for internal combustion engines. Unleaded gasolines";
• technical regulations of the Republic of Belarus TR 2008/011/BY “Motor gasoline and diesel fuel. Safety";
• technical regulations of the Customs Union TR CU 013/2011

“On the requirements for automobile and aviation gasoline, diesel and marine fuel, fuel for jet engines and fuel oil."

On the territory of the Russian Federation, the standard for motor gasoline is GOST R 51313–99 “Automotive gasoline. Are common technical requirements».

Let's consider the basic requirements for motor gasoline according to GOST 31077–2002 (Table 5).

Table 5.Quality indicators of motor gasoline (GOST 31077–2002)

All motor gasoline produced according to technical specifications must be certified for compliance with the general technical requirements of GOST 31077–2002.

In order to improve the quality of gasoline to the level of European standards EN 228:2008, STB 1656–2011 was developed. Motor gasoline must meet the requirements of this standard, according to which it is allowed to use dyes and labeling substances, provided that they do not have any side effects. harmful effects to the engine and fuel supply system. The standard establishes brands of unleaded gasoline and their

kinds. At the same time, the requirements for gasoline grade AI-95-Euro type I and grade AI-98-Euro type I comply with the requirements of the European standard. The requirements for AI-92-Euro, as well as AI-95-Euro and AI-98-Euro type II gasoline are additionally established and take into account the provisions of the technical regulations of the Republic of Belarus TR 2008/011/BY (Table 6).

Table 6Quality indicators of motor gasoline (TR 2008/011/BY)

In the marking of gasoline AI-92, AI-95 and AI-98, the letter A means that the gasoline is for automobiles, the letter I followed by a number is the octane number determined by the research method.

The toxicity of gasoline combustion products is largely determined by their content of sulfur, benzene and aromatic hydrocarbons. The high sulfur content in motor gasoline increases emissions of sulfur oxides, which have a detrimental effect on human health, flora and fauna, and construction materials. Therefore, depending on the content of sulfur and aromatic hydrocarbons, gasolines are divided into two types: I and II (see Table 6).

When benzene is burned, polycyclic aromatic hydrocarbons (benzo(α)pyrenes) are formed, which have carcinogenic properties, i.e. cause cancer. Exhaust gases, which contain more than 300 harmful compounds, also pollute the environment.

To ensure reliable operation of vehicles in various seasonal and climatic conditions, 10 classes of gasoline are distinguished by volatility: A, B, C, C 1, D, D 1, E, E 1, F, F 1. As the class increases, the minimum and maximum pressure saturated vapors, as well as the volume fraction of evaporated gasoline at 70 °C. It is recommended to use the following classes of gasoline on the territory of the Republic of Belarus:

• class B - in the summer (from April 1 to September 30);
• class D 1 - during the transition period (from October 1 to October 30);
• class D - in winter period(from November 1 to March 31). Simultaneous use of summer and winter varieties of gasoline

on or their mixtures when switching engines from summer to winter operation and vice versa is allowed for a month. The rest of the time, gasoline must correspond to climatic conditions. The use of summer grades of gasoline in winter, for example, leads to excessive fuel consumption by 3...5%.

Normal-80 gasoline is used mainly for trucks and outdated engine models with a compression ratio of 6.5...7.

Gasolines with octane numbers of 91, 92, determined by the research method, are intended for medium-boost engines passenger cars with a compression ratio of 8...11 and some trucks. Gasolines AI-95, Premium-95, AI-98, Super-98 are used in passenger car engines with a compression ratio of 8...12. The brands of motor gasoline must comply with the factory instructions for the vehicle.

Let's consider the basic requirements for motor gasoline in accordance with GOST R 51313–99 (Table 7). The requirements established by this standard must be included in all regulatory documents of the Russian Federation for motor gasoline. The standard allows the production of leaded motor gasoline only of grade A-76 (AI-80), which is intended for operation of outdated trucks of the ZIL and GAZ types, the share of which in the vehicle fleet is decreasing, and therefore the need for this gasoline is decreasing.

Table 7.Quality indicators of motor gasoline (GOST R 51313–99)

However, the requirements of GOST R 51313–99 do not comply with accepted international standards, especially environmental requirements. In order to improve the quality of gasoline to the level of European standards, GOST R 51105–97 was developed, which provides for the production of unleaded gasoline of the Normal-80, Regular-91, Premium-95 and Super-98 brands (Table 8) .

Table 8Quality indicators of motor gasoline (GOST R 51105–97)

Note. All gasolines pass the copper plate test.

Premium-95 and Super-98 gasolines fully meet European requirements and are intended mainly for imported cars.

To provide large cities and other regions of Russia with high density road transport environmentally friendly fuel, at the present stage it is planned to produce unleaded gasoline with improved environmental performance (“Urban” AI-80EK, AI-92EK, AI-95EK, AI-98EK; “Yar-Marka 92E” and “Yar-Marka 95E”). Compared to gasoline according to GOST R 51105–97, these gasolines have more stringent standards for benzene content, standardization of aromatic hydrocarbons and the addition of detergent additives.

Also, a number of gasolines in Russia are produced according to technical specifications. According to TU 401-58-220–98, they produce motor unleaded gasolines containing the anti-knock additive APK of the following grades: A-76, Normal-80, Regular-91, AI-92, AI-93, Premium-95 ", "Super-98". According to TU 401-58-235–99

They produce automobile compounded gasoline, obtained by compounding commercial automobile gasolines AI-93 and A-80 with an isopentane-pentane fraction and anti-knock additives “Octane Maximum”, “Super Octane”, etc.

Depending on the ratio of components, two grades of gasoline are produced: AKZ-1 winter (octane number 93 according to the research method) and AKZ-2 summer (octane number 92 according to the research method).

According to TU 401-58-240–99, unleaded motor gasoline is produced, produced from gasoline fractions and gas condensate with the addition of anti-knock additives

“Super Octane”, MTBE, etc. They produce the following brands of gasoline: A-76, “Normal-80”, “Regular-91”, AI-92, AI-93, “Premium-95” (AI-95), “ Super-98" (AI-98).

According to TU 401-58-244–99, unleaded motor gasoline containing ethanol is produced. These gasolines are used for both carburetor and direct injection engines. Gasoline is produced by compounding unleaded gasoline with ethyl dexturated alcohol. Ethanol is used as a high-octane blending component. It can be used as a gasoline substitute. Installed

the following brands of gasoline containing ethanol: AI-92E, AI-93E, AI-95E, AI-98E.

According to TU 401-58-264–00, unleaded motor gasoline (city) is produced, intended for use in densely populated areas of the country. Gasoline contains various additives and additives that increase its performance properties.

According to TU 401-58-95–94, unleaded gasolines with improved environmental and performance properties are produced: AI-80F, AI-91F, AI-92F, AI-93F. They add the anti-knock additive "Ferro 3" and the detergent additive "Afen" or "Avtomag".

According to technical conditions, they produce all-season motor gasolines “Euro-Super-95” and AI-95 “Super Plus”, which contain the oxygen-containing component MTBE.

According to TU 401-58-288–01, four grades of motor unleaded gasoline containing methanol are produced: AI-80M, AI-92M, AI-95M, AI-98M. In these technical specifications standards for cloud point, methanol and iron content are included.

Summer grades of gasoline are used in all regions of Russia, except the northern and northeastern ones, from April 1 to October 1, and in the southern regions - all year round. Winter grades of gasoline are used in the northern and northeastern regions as all-season fuel, and in other regions - from October 1 to April 1.

The priority tasks to be solved in the production of domestic motor gasoline are the following:

• implementation of a complete transition to the production and use of only unleaded gasoline;
• increasing the production of unleaded gasoline with octane numbers over 91 (according to the research method);
• increasing the production of motor gasoline containing various alcohols;
• organizing the supply of gasoline with improved environmental properties to cities and areas with a high density of vehicles.

Automobile gasolines

Gasolines are intended for use in piston internal combustion engines with forced ignition (spark).
Depending on their purpose, they are divided into automobile and aviation.
Despite the differences in application conditions, automobile and aviation gasolines are characterized mainly by general quality indicators that determine their physicochemical and operational properties.
Modern automobile and aviation gasolines must meet a number of requirements to ensure economical and reliable engine operation and operating requirements: have good volatility, allowing to obtain a homogeneous air-fuel mixture of optimal composition at any temperature; have a group hydrocarbon composition, ensuring a stable, detonation-free combustion process in all modes engine operation; do not change its composition and properties during long-term storage and do not have a harmful effect on parts of the fuel system, tanks, rubber products, etc. last years The environmental properties of the fuel are brought to the fore.

Range, quality and composition of motor gasolines

The bulk of motor gasoline in Russia is produced in accordance with GOST 2084-77 and GOST R51105-97 and TU 38.001165-97. Depending on the octane number, GOST 2084-77 provides for five brands of motor gasoline: A-72, A-76, AI-91, AI-93 and AI-95. For the first two brands, the numbers indicate octane numbers determined by the motor method, for the latter - by the research method. Due to the increasing share of passenger vehicles in the total vehicle fleet, there is a noticeable trend towards a decrease in the need for low-octane gasoline and an increase in the consumption of high-octane gasoline. A-72 gasoline is practically not produced due to the lack of equipment operated on it.
The greatest demand exists for gasoline A-92, which is produced according to TU 38.001165-97, although the share of A-76 gasoline in the total production volume remains very high. The specified specifications also provide for gasoline grades A-80 And A-96 with research octane numbers of 80 and 96, respectively. These gasolines are intended mainly for export. Petrol AI-98 with an octane number of 98 according to the research method is produced according to TU 38.401-58-122-95 and TU 38.401-58-127-95. Gasolines A-76, A-80, AI-91, A-92 and A-96 can be produced using ethyl liquid. Low-leaded gasoline AI-91 with a lead content of 0.15 g/dm3 is produced according to separate technical conditions (TU 38.401-58-86-94). In the production of AI-95 and AI-98 gasoline, the use of alkyl lead antiknock agents is not allowed.
The requirements of GOST 2084-77 for the quality of motor gasoline are given in the table. All gasolines produced in accordance with GOST 2084-77, depending on volatility indicators, are divided into summer and winter. Winter gasolines are intended for use in the northern and northeastern regions during all seasons and in other areas from October 1 to April 1. Summer - for use in all areas except the northern and northeastern ones in the period from April 1 to October 1; in the southern regions it is allowed to use summer gasoline during all seasons.
The parameters of motor gasoline produced in accordance with GOST 2084-77 differ significantly from accepted international standards, especially in terms of environmental requirements. In order to increase the competitiveness of Russian gasoline and bring their quality to the level of European standards, GOST R 51105-97 “Fuels for internal combustion engines. Unleaded gasoline. Technical conditions” was developed, which comes into force on January 1, 1999. This standard does not replace GOST 2084 -77, which provides for the production of both leaded and unleaded gasoline. In accordance with GOST R 51105-97, only unleaded gasoline will be produced (maximum lead content no more than 0.01 g/dm3).

Characteristics of motor gasoline (GOST 2084-77)

Depending on the octane number, four brands of gasoline have been established using the research method: "Normal-80", "Regular-91", "Premium-95", "Super-98". Normal-80 gasoline is intended for use in trucks along with A-76 gasoline. Unleaded gasoline "Regular-91" is intended for use in cars instead of leaded A-93. Motor gasolines "Premium-95" and "Super-98" fully meet European requirements, are competitive in the oil market and are intended mainly for foreign cars imported to Russia.
In order to accelerate the transition to the production of unleaded gasoline, instead of ethyl liquid, it is allowed to use a manganese antiknock agent in a concentration of no more than 5 mg Mn/dm3 for the Normal-80 brand and no more than 18 mg Mn/dm3 for the Regular-91 brand. In accordance with European requirements for limiting the content of benzene, the indicator “volume fraction of benzene” has been introduced - no more than 5%. A standard has been established for the indicator “density at 15 °C”. The standard for the mass fraction of sulfur has been tightened to 0.05%. To ensure normal operation of vehicles and rational use Five classes of volatility have been introduced for gasoline for use in various climatic regions according to GOST 16350 - 80. Along with determining the distillation temperature of gasoline at a given volume, it is provided for determining the volume of evaporated gasoline at a given temperature of 70, 100 and 180 ° C. The indicator "volatility index" has been introduced. GOST R 51105-97, along with domestic ones, includes international standards for test methods (ISO, EN, ASTM).
Standards and requirements for the quality of motor gasoline and volatility characteristics in accordance with GOST R 51105-97 are given in the table.

Standards and requirements for the quality of motor gasoline according to GOST R 51105-97

In terms of composition, motor gasoline is a mixture of components obtained as a result of various technological processes: direct distillation of oil, catalytic reforming, catalytic cracking and hydrocracking of vacuum gas oil, isomerization of straight-run fractions, alkylation, aromatization, thermal cracking, visbreaking, delayed coking. The component composition of gasoline depends mainly on its brand and is determined by a set of technological installations at an oil refinery.
The basic component for the production of motor gasoline is usually catalytic reforming or catalytic cracking gasoline. Catalytic reforming gasolines are characterized by low sulfur content, they contain virtually no olefins, so they are highly stable during storage. However, the increased content of aromatic hydrocarbons in them is a limiting factor from an environmental point of view. Their disadvantages also include the uneven distribution of detonation resistance among fractions. In the Russian gasoline stock, the share of the catalytic reforming component exceeds 50%.
Catalytic cracking gasolines are characterized by a low mass fraction of sulfur and research octane numbers of 90-93 units. The content of aromatic hydrocarbons in them is 30-40%, olefinic hydrocarbons - 25-35%. There are practically no diene hydrocarbons in their composition, so they have relatively high chemical stability (induction period 800-900 minutes). Compared to catalytic reforming gasolines, catalytic cracking gasolines are characterized by a more uniform distribution of detonation resistance among fractions. Therefore, it is advisable to use a mixture of catalytic reforming and catalytic cracking components as a base for the production of motor gasoline.
Gasolines from thermal processes such as cracking and delayed coking have low detonation resistance and chemical stability, high sulfur content and are used only to produce low-octane gasoline in limited quantities.
In the production of high-octane gasoline, alkyl gasoline, isooctane, isopentane and toluene are used. Gasolines AI-95 and AI-98 are usually produced with the addition of oxygen-containing components: methyl tert-butyl ether (MTBE) or its mixture with tert-butanol, called faterol. The introduction of MTBE into gasoline makes it possible to increase the completeness of its combustion and the uniform distribution of detonation resistance among fractions. The maximum permissible concentration of MTBE in gasoline is 15% due to its relatively low calorific value and high aggressiveness towards rubber.
To achieve the required level of detonation properties of leaded gasoline, ethyl liquid is added to it (up to 0.15 g of lead/dm3 of gasoline). To gasoline of secondary processes containing unsaturated hydrocarbons, in order to stabilize them and meet the requirements for the induction period, it is allowed to add antioxidants Agidol-1 or Agidol-12. To ensure safe handling and labeling, leaded gasolines must be colored. Gasoline A-76 is colored yellow with fat-soluble yellow dye K, gasoline AI-91 is colored orange-red with fat-soluble dark red dye J. Leaded gasoline intended for export is not colored.
Approximate component compositions of various brands of motor gasoline are given in the table.

Average component compositions of motor gasolines

Recently, the range of motor gasoline has been significantly expanded due to new brands produced according to technical specifications. This is due to a sharp increase in the production of unleaded gasoline and a decrease in the production of leaded gasoline.
In this case, tetraethyl lead is replaced by various non-traditional additives and additives previously produced by chemical and microbiological industry for other purposes.
Such substances include various ethers, alcohols, organometallic compounds, etc. The need to produce such gasoline according to technical specifications is dictated by the fact that all additives and additives can be introduced in strictly defined concentrations. To control the content of these components, the technical specifications provide for special indicators and introduce additional control methods.
All gasolines produced according to technical specifications must comply with the requirements of GOST R 51313-99 "Automotive gasolines. General technical requirements", which will be introduced on July 1, 2000.
The compliance of gasoline produced according to technical specifications with the requirements of GOST R 51313-99 is checked during their certification, which is mandatory.

Automobile gasolines. General technical conditions

Anyone who decides to look for information about the boiling, burning or flash point of gasoline will discover an interesting thing: even in fairly authoritative sources, there is a significant difference between the indicated values ​​of the same parameter. Why does this happen and what are the real values?

What is gasoline?

This point comes first because it is extremely important for understanding the issue. Looking ahead, let's say this: you will never find the chemical formula of gasoline. For example, you can easily find the formula for methane or another one-component petroleum product. Any source that will show you the formula for motor gasoline (no matter whether it is AI-76, which has gone out of circulation, or AI-95, which is the most common now) is clearly mistaken.

The fact is that gasoline is a multicomponent liquid, which contains at least a dozen different substances and even more of their derivatives. And that's just the base. The list of additives used in various gasolines, at different periods of time and for various operating conditions, occupies an impressive list of several dozen items. Therefore, it is impossible to express the composition of gasoline in one chemical formula.

A brief definition of gasoline can be given as follows: a flammable mixture consisting of light fractions of various hydrocarbons.

Gasoline evaporation temperature

The evaporation temperature is the thermal threshold at which spontaneous mixing of gasoline with air begins. This value cannot be unambiguously determined by one figure, since it depends on a large number of factors:

• the basic composition and additive package is the most significant factor, which is regulated during production depending on the operating conditions of the internal combustion engine (climate, power system, compression ratio in the cylinders, etc.);
• atmospheric pressure - with increasing pressure, the evaporation temperature decreases slightly;
• a method for studying this quantity.

For gasoline, the evaporation temperature plays a special role. After all, it is on the principle of evaporation that the operation of carburetor power systems is built. If gasoline stops evaporating, it will not be able to mix with air and enter the combustion chamber. In modern cars with direct injection, this characteristic has become less relevant. However, after a fuel injector injects fuel into the cylinder, it is volatility that determines how quickly and evenly the mist of small droplets mixes with the air. And the efficiency of the motor depends on this (its power and specific consumption fuel).

On average, the evaporation temperature of gasoline ranges from 40 to 50°C. IN southern regions this value is often higher. It is not controlled artificially, since there is no need for it. For the northern regions, on the contrary, it is underestimated. This is usually done not through additives, but through the formation of base gasoline from the lightest and most volatile fractions.

Gasoline boiling point

The boiling point of gasoline is also an interesting value. Today, few young drivers know that at one time, in hot climates, gasoline boiling in the fuel line or carburetor could immobilize the car. This phenomenon simply created traffic jams in the system. The light fractions became excessively heated and began to separate from the heavier ones in the form of bubbles of flammable gas. The car cooled down, the gases became liquid again - and we could continue on our way.

Today, gasoline sold at gas stations will boil (with obvious bubbling with the release of gas) at approximately +80 °C with a difference of +-30% depending on the specific composition of a particular fuel.

Flash point of gasoline

The flash point of gasoline is the thermal threshold at which freely separating, lighter fractions of gasoline ignite from an open flame source when this source is located directly above the test sample.

In practice, the flash point is determined by heating in an open crucible.

The fuel to be tested is poured into a small open container. Next, it is slowly heated without involving an open flame (for example, on an electric stove). At the same time, the temperature is monitored in real time. Each time the temperature of gasoline increases by 1°C, a flame source is used at a small height above its surface (so that an open flame does not come into contact with gasoline). At the moment when fire appears, the flash point is recorded.

Simply put, the flash point marks the threshold at which the concentration of freely evaporating gasoline in the air reaches a value sufficient to ignite under the influence of an open fire source.

Gasoline combustion temperature

This parameter determines the maximum temperature created by burning gasoline. And here, too, you will not find unambiguous information that answers this question with one number.

Oddly enough, but it is for the combustion temperature that the main role is played by the conditions of the process, and not the composition of the fuel. If you look at the calorific value of various gasolines, you will not see the difference between AI-92 and AI-100. In fact, the octane number determines solely the resistance of the fuel to the occurrence of detonation processes. And it does not affect the quality of the fuel itself, much less its combustion temperature. By the way, often simple gasolines, such as the retired AI-76 and AI-80, are cleaner and safer for humans than the same AI-98, modified with an impressive package of additives.

In an engine, the combustion temperature of gasoline ranges from 900 to 1100°C. This is on average, with a proportion of air and fuel close to the stoichiometric ratio. The actual combustion temperature can either drop lower (for example, activating the USR valve slightly reduces the thermal load on the cylinders) or increase under certain conditions.

The combustion temperature is also significantly affected by the degree of compression. The higher it is, the hotter it is in the cylinders.

Gasoline burns with an open flame at lower temperatures. Approximately, about 800-900 °C.

And its characteristics. A mixture, flammable, of light hydrocarbons with a boiling point from 33 to 205 °C. Density about 0.71 g/cm³. Calorific value approximately 10,200 kcal/kg (46 MJ/kg, 32.7 MJ/liter). Freezing point −72 °C when using special additives. Gasoline is a product of oil refining. It is a fuel with low detonation characteristics. There are: natural gasoline, cracked gasoline, polymerization products. Also liquefied petroleum gases and all products used as industrial motor fuels. Gasoline is the most common fuel for most types of transport.

Piston internal combustion engines

Gasolines are intended for use in piston internal combustion engines with forced ignition (spark). Depending on their purpose, they are divided into automobile and aviation. Despite the differences in application conditions, automobile and aviation gasolines are characterized mainly by general quality indicators. Their physicochemical and operational properties are different. Modern automobile and aviation gasolines must satisfy a number of requirements.

They must ensure economical and reliable operation of the engine (Gasoline and its characteristics). Operating requirements: have good volatility, allowing you to obtain a homogeneous air-fuel mixture of optimal composition. At any temperature; have a group hydrocarbon composition that ensures a stable, detonation-free combustion process. Do not change its composition and properties in all engine operating modes. During long-term storage, do not have a harmful effect on parts of the fuel system, tanks, rubber products, etc. In recent years, the environmental properties of fuel have come to the fore.

Composition of gasolines

Gasoline is a mixture of hydrocarbons consisting mainly of saturated 25-61%, unsaturated 13-45%, naphthenic 9-71%, aromatic 4-16% hydrocarbons with a hydrocarbon molecule length from C 5 to C 10 and a number of carbon atoms from 4 -5 to 9-10 with an average molecular weight of about 100D. Gasoline may also contain impurities - sulfur-, nitrogen- and oxygen-containing compounds. Gasoline is the lightest fraction of the liquid fractions of oil (Gasoline and its characteristics). This fraction is obtained in number different processes sublimation of oil. Therefore, the ease and reliability of engine starting, completeness of combustion, warm-up duration, vehicle response and wear rate of engine parts depend on the fractional composition of gasoline. The fractional composition of gasoline is determined according to GOST 2177-99.

Light fractions of gasoline characterize the starting properties of the fuel - the lower the boiling point of the fuel, the better the starting properties. To start a cold engine, it is necessary that 10% of gasoline boils away at a temperature not exceeding 55 degrees (winter grade) and 70 degrees (summer grade) Celsius. Winter grades of gasoline have a lighter (than summer) fractional composition. Light fractions are needed only for the period of starting and warming up the engine. The main part of the fuel is called the working fraction. The following depend on its evaporation: the formation of a flammable mixture during different modes engine operation, warm-up duration (transfer from idle to load), throttle response (the ability to quickly transfer from one mode to another). The content of the working fraction should coincide with 50% of the distillate. The minimum temperature range from 90% to the end of boiling improves the quality of the fuel and reduces its tendency to condense, which increases efficiency and reduces wear of engine parts. The 90% boiling point of a fuel is sometimes called the dew point.

Properties of gasolines

Gasolines are flammable, colorless or slightly yellow (in the absence of special additives) liquids with a density of 700-780 kg/m? Gasolines have high volatility, and a flash point in the range of 20-40 degrees Celsius. The boiling point of gasoline is in the range from 30 to 200 C. The pour point is below minus 60 degrees. When gasoline burns, water is formed and carbon dioxide. At vapor concentrations in the air of 70-120 g/m3, explosive mixtures are formed.
Due to their physical and chemical characteristics, motor gasolines must have the following properties:

• Mixture homogeneity;
• Fuel density - at +20 °C should be 690...750 kg/m2;
• Low viscosity - as it increases, it becomes more difficult for fuel to flow through the nozzles, which leads to a lean mixture. Viscosity is highly dependent on temperature. When the temperature changes from +40 to -40 °C, gasoline consumption through the nozzle changes by 20...30%;
• Volatility - the ability to change from a liquid to a gaseous state. Motor gasoline must have such volatility that it ensures easy engine starting (especially in winter), rapid warming up, complete combustion of fuel, and also eliminates the formation of vapor locks in the fuel system;
• Saturated vapor pressure - the higher the vapor pressure during fuel evaporation in a confined space, the more intense the process of their condensation. The standard limits the upper limit of vapor pressure in summer to 670 GPa and in winter from 670 to 930 GPa. Gasoline with more high pressure prone to the formation of vapor locks; when using them, the filling of the cylinders decreases and engine power is lost; evaporation losses increase when stored in car tanks and warehouses;
• Low temperature properties - the ability of gasoline to withstand low temperatures;
• Combustion of gasoline. “Combustion” in relation to automobile engines is understood as a rapid reaction of the interaction of fuel hydrocarbons with oxygen in the air, releasing a significant amount of heat. The temperature of the vapors during combustion reaches 1500...2400 °C.

Automobile gasolines

In Russia, motor gasolines are produced in accordance with GOST 2084-77, GOST R 51105-97 and GOST R 51866-2002, as well as in accordance with TU 0251-001-12150839-2015 Gasoline AI 92.95 (Alternative).
Motor gasolines are divided into summer and winter (winter gasoline contains more low-boiling hydrocarbons).
Main brands of motor gasoline GOST R 51105-97:
Normal-80 - with a research octane number of at least 80;
Regular-92 - with a research octane number of at least 92;
Premium-95 - with a research octane number of at least 95;
Super-98 - with a research octane number of at least 98

Marking of motor gasoline

In accordance with GOST R 54283-2010, motor gasolines are marked with three groups of signs separated by a hyphen (for example, “AI-92-4”):

• the letters “AI” (motor gasoline with an octane number measured by the research method GOST 8226-82);
• research octane number (for example, 80, 92, 95 or 98);
• number 2, 3, 4 or 5 - gasoline class; the number coincides with the number of the Euro series environmental standard that gasoline must comply with (2 for Euro-2, 3 for Euro-3, etc.).

Example. Brand "AI-92-4" stands for motor gasoline with an octane number of 92, measured by a research method, corresponding to the fourth environmental class(Euro 4 standard). Since the production of harmful leaded gasoline has officially ceased in Russia since 2003, all gasoline is considered unleaded, and this fact is not reflected in the labeling.

Raw materials for gasoline production

The raw material for obtaining gasoline is oil. Oil is a natural liquid mixture of various hydrocarbons with a small amount other organic compounds; a valuable mineral resource, often occurring together with gaseous hydrocarbons (associated gases, natural gas). Crude oil compounds are complex substances consisting of five elements - C, H, S, O and N, and the content of these elements ranges from 82-87% carbon, 11-15% hydrogen, 0.01-6% sulfur, 0–2% oxygen and 0.01–3% nitrogen. Hydrocarbons are the main components of oil and natural gas. (Gasoline and its characteristics) The simplest of them, methane CH4, is the main component of natural gas.

All hydrocarbons can be divided into aliphatic (with an open molecular chain) and cyclic, and according to the degree of unsaturation of carbon bonds - into paraffins and cycloparaffins, olefins, acetylenes and aromatic hydrocarbons. Conventional well crude oil is a greenish-brown, highly flammable, oily liquid with a pungent odor. Chemically, oils are very different and vary from paraffin oils, which consist for the most part from paraffinic hydrocarbons, to naphthenic or asphaltenic hydrocarbons, which contain mainly cycloparaffin hydrocarbons; there are many intermediate or mixed types. Compared to naphthenic or asphaltenic oils, paraffinic oils usually contain more gasoline and less sulfur and are the main raw material for the production of lubricating oils and paraffins. Naphthenic crude oils generally contain less gasoline, but more sulfur and fuel oil and asphalt.

Gasoline is used as fuel for most passenger cars. It is a mixture of hydrocarbons having a boiling point from 30 to 205 degrees Celsius. In addition to hydrocarbons, gasoline contains impurities containing nitrogen, sulfur and oxygen.

Depending on the amount of certain compounds, motor gasoline is divided into different brands, having slightly different operational properties:

• AI-92;
• AI-95;
• AI-98.

With the tightening of environmental requirements, gasolines with a lower octane number, such as A-76 or AI-80, and, therefore, a “dirtier” chemical composition, are currently not produced.

Basic properties

The main properties of gasoline are its chemical composition, ability to evaporate, burn, ignite, form deposits, as well as corrosion activity and resistance to detonation.

The physicochemical properties of gasoline vary depending on what hydrocarbons it contains and in what proportions. The freezing point of gasoline reaches –60 degrees Celsius; if special additives are used, this value can be lowered to –71 degrees. Gasoline actively evaporates at temperatures above 30 degrees, and with increasing temperature, evaporation occurs more intensely. When the concentration of its vapors in the air reaches 74–123 grams per cubic meter, an explosive mixture is formed.

The fractional composition of gasoline directly affects its performance properties. During production, it is important to achieve the correct ratio of light and heavy fractions in order, on the one hand, to ensure sufficiently high volatility at low temperatures, and on the other hand, to prevent interruptions in engine operation due to the formation of vapor locks in the fuel line, which can arise due to intense evaporation a large number of light fractions. In this regard, gasolines used in hot climates and in the Arctic Circle have different chemical compositions in order to provide the necessary performance properties.

Gasoline can be obtained in several ways: by direct distillation of oil and the selection of certain fractions (this method was used at the beginning of the era of motorization); in the middle of the last century, cracking and reforming began to be used. The main components of gasoline obtained by direct distillation are chains of alkanes. During cracking and reforming, they are converted into branched alkanes and aromatic compounds.

The last two methods make it possible to obtain high-octane fuel of grades AI-92, 95 and higher.

Octane number

The name of the gasoline brand consists of an alphanumeric designation. The letters A or AI indicate the method for determining the octane number:

1. motor (A)
2. research (AI)

and the number determines the octane number (92, 95, etc.).

The octane number indicates a property such as gasoline's resistance to detonation. This figure is relative. Iso-octane is taken as a standard, the detonation resistance of which is very high and is taken to be equal to 100. The octane number scale was proposed at the beginning of the last century. It was determined by the content of isooctane in a mixture with normal heptane (its detonation resistance is very low and is accepted equal to zero). Accordingly, AI-92 gasoline is equivalent in its resistance to detonation to a 92% mixture of isooctane and heptane, AI-95 - 95%, and so on. The octane number can be more than 100 if the anti-knock properties of the fuel are even higher than those of pure isooctane.


This value is very important, since detonation leads to rapid destruction of the cylinder-piston group. This is explained by the speed of propagation of the flame front - up to 2.5 km/s, whereas under normal conditions the flame spreads at a speed of no more than 60 m/s.

To increase anti-knock properties, you can either add additives containing lead compounds (tetraethyl lead) or change the fractional composition upon receipt. The first method can be easily obtained from AI-92 gasoline, AI-95, or 98, but has now been abandoned. Because, although such additives significantly increase the performance properties of fuel and have a low cost, they are also very toxic and have a much more detrimental effect on the environment than pure gasoline, and also destroy the car’s catalytic converter (the combustion temperature of leaded gasoline is higher than that of unleaded gasoline, As a result, the ceramic elements of the neutralizer simply sinter, and the device fails).

Other compounds that are less toxic, such as ethyl alcohol or acetone, can also be used as additives. For example, if you add 100 ml of alcohol to a liter of AI-92 gasoline, the octane number will increase to 95. However, the use of such additives is not economically profitable.

Chemical stability

When considering the chemical properties of gasoline, the main emphasis should be on how long the composition of hydrocarbons will remain unchanged, since during long-term storage lighter compounds evaporate and the performance properties are greatly deteriorated. This problem is especially acute if fuel with a lower octane number (for example, AI-92) is converted into gasoline of a higher grade (AI-95) by adding propane or methane to its composition. Their anti-knock properties are higher than those of isooctane, but they also evaporate very quickly.

The state standard requires that the chemical composition of gasoline of any brand, be it AI-92, 95 or 98, remains unchanged for at least five years, subject to storage rules. However, in reality, often even newly purchased fuel already has an octane number lower than declared (for example, not 95, but 92). This is due to the dishonesty of sellers who add liquefied gas into tanks with fuel whose shelf life has expired and the composition does not comply with GOST. As a rule, different amounts of gas are added to the same gasoline to obtain an octane number of 92 or 95. An obvious confirmation of such tricks is the strong smell of gas at the gas station. It is likely that the performance properties of such gasoline will noticeably deteriorate right before our eyes, until the fuel tank is empty.