STUDY OF ANTI-KNOCK CHARACTERISTICS OF LOW-OCTANE GASOLINE WITH THE ADDITATION OF OCTANE BOOSTING ADDITIVES

ABSTRACT

The number of high-octane gasoline fractions required by the market is constantly growing. The constant increase in gasoline consumption entails consideration as a possible option for the creation of a complete set of processes for the production of high-octane gasoline fractions in refineries. This path requires significant investment in the modernization of technological processes. In order to obtain high-octane gasoline based on low - octane gasoline and octane-boosting sitting about to, studies of degrees and influence me octane boosting them additive for anti-knock characteristics of low-octane gasoline

АННОТАЦИЯ

Количество высокооктановых фракций бензина, необходимых рынку постоянно растёт. Постоянное увеличение потребления бензинов влечёт за собой рассмотрение, как возможного варианта, создания полного набора процессов производства высокооктановых бензиновых фракций на нефтеперерабатывающих заводах. Этот путь требует значительных инвестиций в модернизацию технологических процессов. С целью получения высокооктанового бензина на основе низкооктанового бензина и октаноповышающих присадок, проведены исследования степени влияния октаноповышающих присадок на антидетонационные характеристики низкооктанового бензина. 

Keywords: gasoline, isopropanol, methyl tert-butyl ether, sec-Butanol, N - methylaniline , octane number.

Ключевые слова: бензин, изопропанол, метил-трет-бутиловый эфир, втор-Бутанол, N-метиланилин, октановое число.

Introduction. The oil refining and petrochemical industry produces a wide range of gaseous, liquid and solid petroleum products. In the consumption of petroleum products, motor fuels account for more than 50%. Different types of engines have different requirements for them. The desire to improve the knock resistance of gasolines, the chemical and thermal stability of jet fuels, the cetane number of diesel fuels, to improve their low-temperature properties, fractional composition and volatility is a constant stimulus for the development of oil refining and petrochemistry [1].

Petroleum fuels, in particular motor gasolines, are among the main sources of environmental pollution. Thus, with the combustion products of fuels, the following are annually emitted into the atmosphere (million tons): about 80 - sulfur oxides, 30-50 - nitrogen oxides, 300 - carbon oxides, 10-15 billion tons - carbon dioxide. The adoption of new environmental standards has such an impact on the state of many industries that it requires significant changes in the technology for the production of motor fuels [2].

Of particular danger to humans are particles of toxic aerosol emissions with a radius of less than 20 microns, which linger in the atmosphere for a long time and enter the respiratory tract with air.

When in contact with carcinogenic substances, aerosol particles adsorb them on their surface. Carcinogens, getting inside the body, cause the formation of malignant tumors [3].

There is only one way to solve the environmental problem - the car must become environmentally friendly. An important place is given here to the quality of gasoline and the exhaust gas after treatment system, the use of which makes it possible to reduce the toxicity of exhaust gases.

Some information about the composition of the exhaust gases of vehicles with internal combustion engines running on gasoline is given in Table. 1 [3,4] .

Table 1.

The average composition of the exhaust gases of automobile gasoline engines

The toxicity of automobile gasolines and their combustion products is mainly determined by the content of aromatic hydrocarbons, benzene, olefinic hydrocarbons and sulfur in them. Aromatic hydrocarbons are more toxic than paraffinic ones. If paraffins, in accordance with GOST 12.1.005588, belong to the 4th hazard class, then benzene to the 2nd, and toluene to the 3rd. When they are burned, polycyclic aromatic hydrocarbons are formed, including benzpyrenes , which have carcinogenic properties. The higher the content of aromatic hydrocarbons in gasoline, the higher the temperature of its combustion and the content of nitrogen oxide in the exhaust gases [3,5].

According to the nature of the impact on the human body, two groups of hydrocarbons are distinguished: irritating and carcinogenic.

Irritant hydrocarbons have a narcotic effect on the central nervous system and affect the mucous membranes. These include aldehydes, all unsaturated and saturated compounds of carbon with hydrogen, not related to aromatic compounds [6].

The greatest danger to humans are hydrocarbon compounds of the carcinogenic group: 1,2-benzanthracene (C₁₈H₁₂), 3,4-benzpyrene (C₂₀H₁₂), 1,2-benzpyrene (C₂₀H₁₂), 3,4-benzfluoranthene (C₂₀H₁₄). Especially dangerous is 3,4-benzpyrene, which is a kind of indicator of the presence of other carcinogens in the mixture.

Once in the human respiratory tract, polycyclic aromatic hydrocarbons gradually accumulate to critical concentrations and stimulate the formation of malignant tumors. The concentrations of polycyclic aromatic hydrocarbons in the air have not been studied enough, but, apparently, they do not exceed 10–12–10–14 g/m ³ [6].

As for hydrocarbons, especially olefins, they are involved in the formation of smog, which causes irritation of the eyes, throat and nose.

Currently, in order to reduce the toxicity of vehicle exhausts, many countries have set limits on the content of benzene (up to 1%) and total aromatic hydrocarbons (30–35%) in gasoline (Table 2). MPC for benzene in the atmosphere of settlements is 1.5 mg/m³. In the total composition of the organic components of toxic vehicle emissions, saturated hydrocarbons account for over 32%, unsaturated hydrocarbons for about 27%, and aromatic hydrocarbons for about 4%.

Table 2.

Modern requirements for the quality of gasoline

For each percentage increase in the benzene content in the fuel, its content in the exhaust gases increases by 0.7–0.8%; more than 75% of the benzene contained in the air comes from the exhaust gases of vehicles [7]. With a decrease in the benzene content in gasoline, as well as with the help of a fuel afterburning system and the introduction of oxygen-containing compounds, and in the case of replacing aromatic hydrocarbons with oxygen-containing compounds, a cumulative effect is observed, a significant reduction in benzene emissions with exhaust is possible [8].

To bring the quality of motor gasoline to the required requirements and increase their octane number, it is more economically feasible to use octane-boosting additives.

Objects and methods of research. The objects of the study are commercial motor gasoline AI-80 and octane-boosting additives: isopropanol (IP), sec-Butanol, ethyl-tert-butyl ether (ETBE), N-methylaniline. Physico-chemical properties of these additives are given in table 3 [9].

Table 3.

Physical and chemical properties of octane boosters

To determine ON of the obtained new gasolines, a single-cylinder universal unit UIT-85 was used (Fig. 1).

The study was carried out as follows:

First, the barometric pressure of the room was measured using a barometer and it was equal to 95200. This value was converted to mm Hg, as follows: 95200-190 (according to the barometer passport) = 95010. According to the table, it was determined that 95010 corresponds to 712.6 mm Hg. The correction for barometric pressure was determined using the following equation:

K \u003d (760 - P) • 0.03 \u003d (760 - 712.6) • 0.03 \u003d 1.42

With the help of this coefficient, the degree of compression of three samples of motor gasoline with different ON was determined (79, 80, 81):

79 → 15.69 (from the table for ON 79 gasoline) + 1.42 = 17.11

80 → 15.88 + 1.42 = 17.30

81 → 16.05 + 1.42 = 17.47

Before testing, the UIT-85 unit was prepared for operation: first, the circulating oil was heated to 50-60 ° C. After that, the engine was started, which works with the help of an electric generator. After starting the engine, the circulating water was heated to 96 ° C. Then, a reference isooctane with ON is tested at the facility 80 and a compression ratio of 17.30. When testing the standard, the display of the detonometer is set to 55 ± 3.

Results and discussion. And the anti-knock efficiency of IP was evaluated by the increase in the octane number of AI-80 commercial gasoline. In fig. 2 shows the results of IP tests.

As the results of the study show, with the addition of IP, the octane number of commercial gasoline synchronously increases with an increase in IP concentration. At a concentration of IP up to 10% vol. RON rises to 85.7 points. It should be noted that the use of IP in its pure form does not completely solve the problem of converting low-octane gasolines into high-octane ones. Based on this, other octane boosters with higher ON were used in a further study.

Figure 1. Single-cylinder universal unit UIT-85

Figure 2. Influence of IP oxygenate on the detonation resistance of AI-80 commercial gasoline

In a further study, the sec-Butanol was used as oxygenate. This oxygenate has not found wide application due to the insufficiency of its raw material base. The raw material base for the synthesis of sec-Butanol can be expanded through dimerization ethylene to n-butenes or its oligomerization with the formation of butene as a by-product.

The results of the study of the octane-boosting properties of sec-Butanol are shown in Figure 3.

Figure 3. Influence of oxygenate second - Butanol for detonation resistance of commercial gasoline AI-80

As can be seen from Fig. 3, the oxygenate sec-Butanol increases RON motor gasoline to 84.5 points. This additive also failed to achieve high detonation resistance of AI-80 commercial gasoline.

Octane-enhancing additive ETBE was tested. The additive was tested in an amount of 1 to 10% (vol.) in the composition of AI-80 commercial gasoline. The test results with this additive are shown in fig. 4.

Figure 4. Effect of ETBE oxygenate on the detonation resistance of AI-80 commercial gasoline

As the results of the study show, the ETBE additive has the best octane-boosting properties; when using this additive, RON AI-80 rose to 88.7. However, for the widespread use of the ETBE additive, it becomes necessary to establish its large-scale production in the republic.

It should be noted that when C₁-C₃ alcohols and ethers are introduced into the fuel, there is a danger of water release, it is necessary to use anti-corrosion additives to prevent corrosion of metal surfaces, that the main disadvantage of gasoline-alcohol and gasoline-ether fuels is their phase instability, due to the presence of small amounts of water and, as a consequence, limited mutual solubility of the components.

To obtain commercial gasoline with improved anti-knock properties, additives based on aromatic amines were used in further experiments. As we know, N-methylaniline has a high octane number. On the basis of this amine, several types of octane-boosting additives (for example, ADA) are produced in foreign countries .

ADA is a clear, low-viscosity yellow liquid. An additive in low-octane gasoline, 1.5% of this additive increases its ON more than 6 units. ADA in Russia is used at various oil refineries at a concentration of not more than 1.3% (wt.) [9].

Based on the above data, to obtain high-octane motor gasoline from the original low-octane and octane-boosting additives, N-methylaniline was used with concentrations from 0.5 to 3% vol. The research results are shown in fig. 5.

Figure 5. Influence of the octane-boosting additive N-methylaniline on the detonation resistance of commercial gasoline AI-80

As can be seen from fig. 5, the additive based on the aromatic amine N-methylaniline has a high octane-boosting effect.

In order to determine the degree of change in the physicochemical characteristics of AI-80 gasoline when an octane-boosting additive is added, the properties of gasoline and its composition with N-methylaniline additive were investigated and compared (Table 4). The additive was mixed with gasoline at room temperature using a stirrer.

Table 4.

The influence of the MMA additive on physical and chemical properties of gasoline AI-80

As can be seen from Table 4, ON gasoline with the addition of the N-methylaniline additive increased significantly, while the physico-chemical parameters remained almost unchanged.

Conclusion. Thus, the results of the study showed that it is possible to obtain high-octane fuel without changing the component composition of gasoline. With ETBE additive, the octane number of AI-80 gasoline according to RON increased from 80 to 88.7. When adding N-methylaniline in the amount of 3.0% vol. in AI-80 base gasoline, ON increased to 85.8 units according to RON.

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