RU2371469C2 - Fuel composition for spark-ignition internal combustion engine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to fuel which is used in spark-ignition internal combustion engines. Proposed fuel composition for spark-ignition internal combustion engines contains 50 to 90 vol % absolute ethanol, 10 to 30 vol % liquid mixture of hydrocarbons, 5 to 15 vol % ether and 1 vol % combustion promoter. The combustion promoter used in each version can be cyclohexylnitrate or 2-ethylhexylnitrate. The combustion promoter used in the second version nitrites of C₄-C₆ alcohols. The combustion promoter used in the third version is a mixture of cyclohexylnitrate or 2-ethylhexylnitrate with nitrites of C₁-C₆ alcohols.

EFFECT: improved combustion and shorter burning time, which allows for eliminating the main disadvantage of fuel containing over 50% ethanol, and, as a result, increasing power of an engine running on this fuel.

4 cl, 7 ex

Description

The invention relates to the field of fuels, which are used in internal combustion engines with spark ignition.

Today, the main varieties of motor fuel are diesel fuel (diesel fuel) and gasoline (a liquid mixture of hydrocarbons) produced from oil, the deposits of which are limited. In engines with spark ignition, gasoline is used, the vapor of which in a mixture with air forms a fuel mixture, the detonation resistance of which to compression in the cylinder is characterized by an octane number. The higher this indicator, the higher the knock resistance, and the higher the compression ratio the engine can have. To date, the vast majority of engines in cars that use gasoline as fuel are designed to use fuel with an octane rating of 80-85 to 95-98 units (according to the research method). To achieve such indicators in gasoline, which is produced from oil, there is a cumbersome and energy-intensive secondary processing of oil. Even under conditions of a high degree of development of the petrochemical industry, achieving high octane numbers is a complex problem, which is partially solved by using high-octane additives. On the other hand, in conditions of oil shortages, the development of new types of alternative fuels, using ethyl alcohol as the main component, which is produced from renewable plant materials, encounters great difficulties. The parameters of ethyl alcohol are so different from similar parameters of gasolines that for fuels with its high content (for example, E85), the development of a special engine is needed.

A known fuel composition (patent DE 3033220, IPC C10L 1/18, publ. 1.04.1980), in which to create a stable mixture of gasoline (liquid mixture of hydrocarbons) with 10-40% lower alcohols, propylene glycol monooleate mixed with alcohols (10 -15% isobutyl and isopropyl alcohols) and ketones (4% acetone). Moreover, the authors of the patent use 10-30% of carcinogenic aromatic hydrocarbons and 10-30% of toxic methanol, which is unacceptable today because of the high content of carcinogenic condensed aromatic hydrocarbons and toxic formaldehyde in the exhaust gases. All components of this fuel composition are products of the chemical industry, which uses oil and natural gas as raw materials, that is, such a fuel composition does not apply to alternative compositions - those that are produced from renewable raw materials.

Known fuel composition (patent US 3822119, CL 44/451, publ. 2.07.1974), in which 5-40% of a mixture of synthetic higher alcohols C ₄ -C ₈ and up to 25% water are added to gasoline, which reduces the toxicity of waste gases. However, such a fuel cannot be attributed to alternative, since gasoline remains the main component of fuel.

A known fuel composition (patent RU 2044033, IPC C10L 1/18, publ. 09/20/1995), in which gasoline compound 5-20% of waste from the production of isopropyl alcohol, namely a mixture of 70-80% diisopropyl ether, 10-15% isopropyl alcohol , 8-10% of propylene polymerization products and up to 3% of water. As in the fuel composition described above, gasoline remains the main component of this fuel. In addition, propylene, which is the starting material for the production of isopropyl alcohol, is obtained by cracking or pyrolysis of petroleum products.

Known fuel composition (patent EP 0064253, IPC С10L 1/02, publ. 04/27/1982), in which ethers (methyl tert-butyl, isopropyl tert-butyl, sec-butyl tert-butyl) are used to increase the octane number of gasoline in the amount of 5-40% and alcohols (methyl - up to 15%, isopropyl - up to 20%, sec-butyl - up to 20%, tert-butyl - up to 85%), except ethyl alcohol. All of the above components are synthetic products of the chemical industry.

Thus, since gasoline remains the main component in all of the known fuels discussed above, none of them can be classified as alternative, that is, those that are produced by more than 50% from renewable (plant) raw materials. The alcohols and esters used are synthetic products, the feedstock for the synthesis of which remains oil and natural gas.

Closest to the proposed fuel composition is a fuel composition for internal combustion engines with spark ignition (utility model patent UA 13086, IPC C10L 1/00, published March 15, 2006), containing 50-90 vol.% Absolute ethanol, 5- 15 vol.% Ether and 10-30 vol.% A mixture of hydrocarbons. Any ether can be used as an ether: tert-C ₄ -C ₅ OC ₁ -C ₂ , i.e. methyl tert-butyl, ethyl tert-butyl, ethyl tert-amyl and others, and as a mixture of hydrocarbons, stable gas or direct distillation gas with any octane rating. Such a fuel composition was developed for use in conventional large-volume internal combustion engines (3 liters or more) without modification. It refers to alternative types of motor fuel, since more than 50% of it is ethyl alcohol, which is produced from renewable plant materials. Extremely high, as for gasoline, the octane number of this fuel composition - 130-132 according to the cold-plasma method - is not an obstacle, since the combustion temperature of the mixture is lower than the combustion temperature of gasoline (360 ° C in the exhaust manifold of the engine that runs on this fuel, in comparison with 500-550 ° C - on gasoline).

The main disadvantage is the loss of engine power when operating on fuel with a high content of ethyl alcohol due to the low heat of combustion and the relatively high heat of vaporization of it as the main component, which significantly affects the dynamics of acceleration of a car, especially equipped with a small engine.

The basis of the proposed solution is the task of increasing engine power when operating on a fuel composition that contains more than 50 vol.% Ethyl alcohol, both due to the most complete combustion of the fuel, and due to the reduction of the combustion time, which allows the use of the specified alternative fuel in conventional spark ignition internal combustion engines without any modifications.

The problem is solved in that the fuel composition for internal combustion engines with spark ignition, containing 50-90 vol.% Absolute ethyl alcohol, 10-30 vol.% Liquid mixture of hydrocarbons and 5-15 vol.% Ether, according to the proposed solution, additionally contains up to 1 vol.% of the combustion promoter. Moreover, in one embodiment, cyclohexyl nitrate or 2-ethylhexyl nitrate can be used as a combustion promoter. In the second embodiment, nitrites of С ₄ -С ₆ alcohols are used as a combustion promoter. In the third embodiment, a mixture of cyclohexyl nitrate or 2-ethylhexyl nitrate with nitrites of C ₄ -C ₆ alcohols is used as a combustion promoter.

It is known that nitro derivatives of hydrocarbons are effective promoters for diesel fuel, where they are used as additives in small quantities to increase the cetane number of diesel fuel. But since the mechanism of influence of the ignition promoters, which are used to increase the cetane number of diesel fuel by lowering the ignition threshold of the fuel mixture during compression, and the mechanism of influence of the combustion promoters, which are proposed for use in motor fuels with a high content of ethyl alcohol, are significantly different, the ignition promoters cannot be effective in high-octane motor fuel, which is made on the basis of renewable raw materials. In addition, it is known to use a mixture of nitromethane, nitroethane and nitropropanes in an amount of up to 15-20%, which was proposed for motor fuels with a high content of aromatic hydrocarbons (US 2004 | 0148849, US 6319294 B1). Nitro derivatives of hydrocarbons have high heat of combustion, and the use of them as components in large quantities significantly increases the heat of combustion of the fuel, which leads to an increase in the power of the engine running on this fuel. However, with so many nitro derivatives in the fuel, they should not be attributed to additives, which, in essence, are promoters, but to fuel components. It was found that the addition of 2-nitropropane in an amount of up to 2 vol.% To the above alternative fuel composition, with a high content of ethyl alcohol, is ineffective, that is, nitropropane cannot be used as a combustion promoter for such fuel.

In the proposed fuel composition due to the use of additives, up to 1% vol. Combustion promoters, the types of which are established experimentally, provide a more complete combustion of the fuel and shorten the combustion time, which eliminates the main disadvantage of fuel with an ethyl alcohol content of more than 50% and, as a result increase engine power when operating on this fuel.

It has been experimentally established that there are combustion promoters that do not affect the octane number, and promoters that reduce the octane number of ethanol-based fuel. The existence of combustion promoters that do not affect the octane number confirms that the mechanism of influence of ignition promoters for diesel fuel and the mechanism of influence of combustion promoters in high-octane fuel are significantly different. Engine power when running on fuel promoted by either the first type of promoter or the second type of promoter, or a mixture thereof, increases to a certain limit, which may even exceed the power when working on gasoline. Small concentrations of combustion promoters, namely, less than 1 vol.%, In which they are used in the proposed fuel composition, cannot significantly affect the heat of combustion of the fuel composition as a whole, but increase the completeness of combustion of fuel, reduce the time of combustion of fuel and, as a result, increase engine power.

As mentioned above, the proposed combustion promoters are divided into two types: almost not affecting the octane number of fuel based on ethyl alcohol (see paragraph 2 of the utility model formula - the first type) and lowering the octane number (see paragraph 3 of the utility model formula - second type). The first type of promoters (Clause 2 of the utility model formula) that increase engine power when running on fuel with their addition, but having little effect on the octane number, include high-boiling nitrates (esters of nitric acid and C ₆ -C ₈ alcohols) or dialkyl peroxides, the boiling point of which exceeds the upper limit of the boiling range of the main components of the fuel. If the substance decomposes before boiling, it is estimated from the distillation temperature in vacuum what the boiling point would be at a pressure of 1 atm. For example, cyclohexyl nitrate has a boiling point of 80 ° C at 20 mm Hg, which corresponds to approximately 180 ° C at 760 mm Hg.

The second type of promoters (Clause 3 of the utility model formula), which reduce the octane number with increasing power, includes nitrites (esters of nitrous acid) of C ₃ -C ₆ alcohols, provided that the boiling point is in the middle of the fuel boiling range. For example, amyl nitrite has a boiling point of 104 ° C, and the main components of the fuel composition boil in the range from 54 ° C (methyl tert-butyl ether) to 150 ° C (the end of boiling gasoline).

Using a mixture of promoters of the first and second type allows you to select the necessary parameters of the fuel depending on the requirements.

The proposed fuel composition is made by direct mixing. The sequence of adding components does not matter.

The following are examples of compositions that are made according to the proposed solution.

Variants of different composition, in which the first type of promoters were used, have little effect on the octane number of the fuel (claim 2 of the utility model formula), are given in examples No. 1-2.

Example 1:

absolute ethyl alcohol (0.2% water) - 54.67 vol.% methyl tert-butyl ether - 14.91 vol.% stable gasoline - 29.82 vol.% cyclohexyl nitrate - 0.60 vol.%

The octane number according to the motor method is 91.2. The octane number of the initial mixture containing 55 vol.% Ethyl alcohol, 15 vol.% MTBE (methyl tert-butyl ether) and 30 vol.% Gas stable gasoline by the motor method exceeds 100 units.

Example 2:

absolute ethyl alcohol (0.2% water) - 54.46 vol.% methyl tert-butyl ether - 14.85 vol.% stable gasoline - 29.70 vol.% 2-ethylhexyl nitrate - 0.99 vol.%

The octane number by the motor method is 90.7. The octane number of the initial mixture containing 55 vol.% Ethyl alcohol, 15 vol.% MTBE and 30 vol.% Gas stable gasoline by the motor method exceeds 100 units.

Thus, the addition of cyclohexyl nitrate or 2-ethylhexyl nitrate within 1% almost does not reduce the octane number of the fuel, leaving it at least 100 units according to the research method, but the engine power when working on promoted fuel increases significantly and reaches the optimum power at approximately a 0.5- 0.6% vol.

The dependence of the octane number by the motor method on the concentration and properties of the promoter of the second type (claim 3 of the utility model formula) can be traced on the examples:

Example 3:

absolute ethyl alcohol (0.2% water) - 54.78 vol.% methyl tert-butyl ether - 14.94 vol.% stable gasoline - 29.88 vol.% amyl nitrite - 0.40 vol.%

The octane number according to the motor method is 87.7. The octane number of the initial mixture, which contains 55 vol.% Ethyl alcohol, 15 vol.% MTBE and 30 vol.% Gas stable gasoline by the motor method, exceeds 100 units.

Example 4:

absolute ethyl alcohol (0.2% water) - 54.67 vol.% methyl tert-butyl ether - 14.91 vol.% stable gasoline - 29.82 vol.% isoamyl nitrite - 0.60 vol.%

The octane number according to the motor method is 85.6. The octane number of the initial mixture containing 55 vol.% Ethyl alcohol, 15 vol.% MTBE and 30 vol.% Gas stable gasoline by the motor method exceeds 100 units.

Example 5:

absolute ethyl alcohol (0.2% water) - 54.56 vol.% methyl tert-butyl ether - 14.88 vol.% stable gasoline - 29.76 vol.% butyl nitrite - 0.80 vol.%

The octane number according to the motor method is 84.3. The octane number of the initial mixture, which contains 55 vol.% Ethyl alcohol, 15 vol.% MTBE and 30 vol.% Gas stable gasoline by the motor method, exceeds 100 units.

The use of a mixture of combustion promoters of both types allows you to adjust the octane number and engine power when working on alternative alcohol-containing fuel in a wide range, reaching indicators that are as close as possible to similar indicators of combustion of commercial gasolines.

Below are examples of the proposed fuel compositions in which mixtures of promoters of the first and second types are used as a combustion promoter.

Example 6:

absolute ethyl alcohol (0.2% water)  - 54.56 vol.% methyl tert-butyl ether - 14.88 vol.% stable gasoline - 29.76 vol.% cyclohexyl nitrate - 0.40 vol.% isoamyl nitrite - 0.40 vol.%

The octane number according to the motor method is 86.2, which according to the research method is approximately 95-96 units and corresponds to the performance of A95 gasoline.

Example 7

absolute ethyl alcohol (0.2% water) - 54.61 vol.% methyl tert-butyl ether - 14.90 vol.% stable gasoline - 29.79 vol.% cyclohexyl nitrate - 0.50 vol.% butyl nitrite - 0.20 vol.%

The octane number according to the motor method is 90.1, which corresponds to the performance of A98 gasoline.

The CO content decreases to 0.2% at idle and to 1.5% in acceleration mode, while the CO ₂ content increases to 14-18%, which directly indicates an increase in the completeness of fuel combustion. The same indicator for gasoline is 1.5-2% СО at idle and 6-8% СО in acceleration mode. Under conditions of low combustion temperature, the content of NO, in comparison with work on gasoline, also decreases by 3-10 times.

Claims (4)

1. The fuel composition for internal combustion engines with spark ignition, containing 50-90 vol.% Absolute ethyl alcohol, 5-15 vol.% Ether and 10-30 vol.% Liquid mixture of hydrocarbons, characterized in that it additionally contains up to 1% vol. Combustion promoter. 2. The fuel composition for internal combustion engines with spark ignition according to claim 1, characterized in that cyclohexyl nitrate or 2-ethylhexyl nitrate is used as a combustion promoter. 3. The fuel composition for internal combustion engines with spark ignition according to claim 1, characterized in that nitrites of C ₄ -C ₆ alcohols are used as a combustion promoter. 4. A fuel composition for spark ignition internal combustion engines according to any one of claims 1 to 3, characterized in that a mixture of cyclohexyl nitrate or 2-ethylhexyl nitrate with nitrites of C ₄ -C ₆ alcohols is used as a combustion promoter.