OBTAINING ANTI-SMOKE INSTALLATIONS FOR DIESEL FUEL

ABSTRACT

The main method for obtaining ethers is the esterification of alcohols with organic acids in the presence of acid catalysts, and esterification without catalysts usually proceeds very slowly. Therefore, in most cases, the reaction of carboxylic acids with alcohols is carried out in the presence of substances that accelerate the reaction.

The article considers the process of synthesis of esters of isobutane and oxalic acid. The IQ spectra of the samples were studied and the results analyzed. Synthesized esters were analyzed, as well as Euro V low sulfur diesel fuel, and conclusions were drawn from the results of the study.

АННОТАЦИЯ

Основным методом получения сложных эфиров является этерификация спиртов органическими кислотами в присутствии кислых катализаторов, а без катализаторов этерификация обычно протекает очень медленно. Поэтому в большинстве случаев реакцию карбоновых кислот со спиртами проводят в присутствии веществ, ускоряющих реакцию.

В статье рассмотрен процесс синтеза эфиров изобутана и щавелевой кислот. Исследованы ИК-спектры образцов и проведен анализ результатов. Проведены анализы синтезированных сложных эфиров, а также дизельное топливо с низким содержанием серы класса Евро-V и по результатам исследования даны выводы.

Keywords: Compound ether, carbonic acid, diesel fuel, viscosity, density.

Ключевые слова: сложный эфир, углекислота, дизельное топливо, вязкость, плотность.

Introduction

The method of improving fuel quality by introducing effective additives is usually very economical; much cheaper than any other fuel processing process for the same purpose. The difficulty lies in choosing additives with sufficient efficiency for fuels of different chemical compositions. It is important that additives while improving some qualities, do not worsen other qualities of fuel and their properties in general. It is better to use multifunctional additives. When adding several additives to fuel, their effectiveness should be maintained independently of each other and unwanted interaction should be excluded [1].

Recently, diesel car engines have become widespread and successfully compete with gasoline engines, which is helped by the high efficiency of the diesel engine compared to the gasoline engine [6].

Diesel fuel is more environmentally friendly than gasoline. The high reliability and efficiency of diesel engines justify their widespread use, and this leads to the demand for diesel fuel in the world market reaching millions of tons per year.

Modern requirements for the quality of diesel fuel depend, first of all, on the environmental characteristics of the fuel itself and its combustion products. In addition to reducing harmful emissions in exhaust gases, the use of diesel fuels with improved environmental performance has caused several problems: fuel pump failures due to a decrease in the level of lubrication of diesel fuel and increased corrosion. Diesel fuel is associated with the removal of surface hydraulics - active substances capable of forming a protective film [2].

Therefore, the production of fuel with improved environmental performance is impossible without additives for various functional purposes: anti-wear, cetane-increasing and winter depressant-dispersant additives [3].

The main manufacturers and suppliers of anti-soaking additives belong to foreign companies such as BASF, Lubrizol, Infineum, Clariant and others. "Baykat", "Alta", "Cascade-5", "Mixent-2030" are suggested anti-organism supplements with a similar effect. It is known from the literature that the active ingredient of these supplements is mainly refined oils or carboxylic acids of plant origin [4].

Along with these anti-organism additives, so-called "biodiesel" products, which esterify vegetable oils with methanol, are widely used. The practice of using additives containing organic acids and "biodiesel" has shown that they lead to carbon formation and clogging of nozzles for spraying diesel fuel in the combustion chambers [5].

The lubricity of diesel fuel depends on the total sulfur content, polycyclic aromatic hydrocarbon content, fractional content and viscosity. The lubricity of low-sulfur diesel fuels deteriorates with a decrease in the content of polycyclic aromatic hydrocarbons, fractional composition and viscosity. That is why the diameter of the body of winter and arctic diesel fuels is much larger than that of summer diesel fuels with the same sulfur content [1].

Object and methods of research

The synthesis of esters was carried out by carrying out the etherification reaction of carboxylic acids with alcohols. As carboxylic acids, we chose: oxalate (GOST 22180-76) and isobutyric acids (TU 6-09-1653-87). The purity of acids is at least 98%. Used alcohols are n-heptanol (TU 6-09-2649-78), n-nonanol (TU 6-09-3331-78), n-butanol (GOST 5208-81), n-pentanol (GOST 5830-79), 2-ethyl hexanol (GOST 26624-85) and ethylene glycol (GOST 19710-83). All alcohol has a purity of at least 96%. Below we consider the process of etherification of isobutyric acid and 2-ethyl hexanol.

The process proceeds according to the following reaction:

Results and discussion

In the synthesis of isobutyric acid esters, an aqueous hydrocarbon carrier was used, which was obtained as an acid catalyst - sulfuric acid (2 ml) and cyclohexane. A mixture of isobutyric acid (1 mol), 2-ethyl hexanol (1.5 mol) and cyclohexane is poured into a round bottom flask. The flask was fitted with a Dean-Stark trap, a reflux condenser, and a thermometer, and the empty neck of the flask was closed with a stopper. The process was carried out at a temperature of 97-112 ℃.  When the temperature is 12 An acid catalyst - sulfuric acid (2 ml) and a hydrocarbon water carrier obtained as cyclohexane was used in the synthesis of isobutyric acid esters. A mixture of isobutyric acid (1 mol), 2-ethyl hexanol (1.5 mol) and cyclohexane is poured into a round bottom flask. The flask was fitted with a Dean-Stark trap, a reflux condenser, and a thermometer, and the empty neck of the flask was closed with a stopper. The process was carried out at a temperature of 97-112 °С. When the temperature is 12°C lower than the target, the metered catalyst is poured through the empty neck of the flask. When the boiling point of the solvent was reached, vapours of an azeotropic mixture of water and cyclohexane rose. The cyclohexane condensate and water formed during the reaction flow from the reflux condenser to the Dean-Stark trap, and this mixture is separated into a solvent and water layer. After the water flow is stopped, the etherification product is cooled and washed with an aqueous solution of NaHCO₃, and the organic and aqueous layers are separated in a separatory funnel. The organic layer is dried with CaCl₂ and distilled under a gentle vacuum to remove the solvent and excess alcohol.

An acid catalyst was not used in the synthesis of oxalic acid esters, since in this case, the esterification process took place in the presence of the original acid with sufficient catalytic power. In these syntheses, 1 mol of acid, 3 mol of alcohol and cyclohexane were obtained.

Otherwise, the synthesis process was carried out as described above, but with a sampling of the reaction, and mass to determine its acid number. At acid number values of 0.3 - 0.5 mg NaOH, the experiments were stopped and the reaction mass was isolated first under atmospheric conditions, then under vacuum, first by solvent and then alcohol distillation.

The results of the analysis of the synthesized ethers are presented in Tables 1 and 2. The obtained ethers boiled in the range of 207-362 ℃, which corresponds well with the boiling range of diesel fuels. To compare the properties of samples of esters with different structures, oleic acid, a light distillation of refined oil and n-butyl ester of rapeseed oil acids were taken as standards. Their properties are also listed in Table 1.

Table 1.

Physico-chemical parameters of synthesized samples

Table 2 summarizes the results of spectral analyzes of 5% solutions of synthesized samples of complex esters and standard products in highly refined diesel fuel (sample A) obtained by IR-spectroscopy.

Table 2.

Results of IR-spectra analysis of synthesized samples

IR spectra were obtained on a Specord - 75 IR IR spectrophotometer with a KBr cuvette thickness of 0.067 mm. The specific absorption coefficients of the carboxyl group (Ether group (K₁₇₀₀), aliphatic hydrocarbon fragments connected with complex ether groups (K₁₇₃₅) (K₁₁₆₅) and hydrocarbon fragments with unsaturated bonds (K₁₆₄₀) are calculated by the equation K= D/dK. Here D is the optical density, and dK is the cuvette thickness.

Absorption bands at 1165 nm and 1735 nm are observed in the IR spectra of all synthesized ethers (1-7), which are characteristic of ethers. The IR spectra of tall oil and oleic acid show absorption bands at 1700 nm, which are characteristic of the carboxyl group. In addition, a band is observed at 1640 nm, which is associated with the presence of unsaturated bonds for oleic acid. In the spectrum of the n-butyl ether of rapeseed oil acids, bands at 1165 nm, 1735 nm (ether) and 1640 nm (unsaturated bonds) are clearly distinguished.

Low-sulfur diesel fuel whose properties are listed in Table 3 was used to obtain diesel fuel containing ether additives synthesized by us. Sample A corresponds to "winter" diesel fuel of the Euro-4 class, sample B corresponds to "summer" diesel fuel of the Euro-4 class.

Table 3.

Characteristics of diesel fuel samples

The results of the analysis of the lubricity properties of the fuels determined by measuring the diameter of the bottom point show that despite the full compliance with the requirements of the standard for other quality parameters, the lubricity properties of diesel fuels (622-673 μm) do not meet the requirements of EN-590 (DPI value is at most 460 μm).

Therefore, it is necessary to correct the lubricating properties of diesel fuels by adding additives of the opposite type to them.

Conclusion

Esters of isobutane and oxalic acids were synthesized and their IR spectra were studied. Analyzes of synthesized esters, as well as low-sulfur diesel fuel of the Euro-5 class, were carried out. The results of the analysis show that Euro-5 diesel fuel has low lubricity, which requires the addition of anti-smoke additives.

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