RU2485092C1 - Method of producing nitroesters of monoatomic alcohols - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing nitroethers of monoatomic alcohols which can be used as efficient cetane number-increasing additives for diesel fuel. Disclosed is a method of producing esters of monoatomic alcohols by treatment thereof with a sulphuric acid and nitric acid mixture in the presence of a carbamide, separating the acidic nitroester and washing thereof, wherein the monoatomic alcohol used is 2-ethylhexanol and/or isoamyl alcohol, the sulphuric acid and nitric acid mixture has the composition, wt %: HNO₃ - 18.0-21.0 H₂SO₄ -62.0-65.0, water - the balance up to 100, and is prepared from 99.8% HNO₃, 93.4% H₂SO₄ and spend acid obtained during the nitration process; the sulphuric acid and nitric acid mixture is treated at temperature not higher than 25-30°C for 25-30 minutes, and the acidic nitroester is washed first with flush water with the ratio of the product to flush water equal to 1:0.5, and then with 2% sodium hydroxide solution in ratio of 1:0.3.

EFFECT: method of producing nitroesters of monoatomic alcohols enables to obtain an end product with output of not less than 98,5% with content of the basic substance of 99,5-99,8%, with short duration of the method and number of flushing cycles; the method enables to use up to 50% spent acids in the process and considerably reduces the amount of flush water.

Description

The invention relates to a method for producing nitroesters of monohydric alcohols, which are used as effective cetane-raising additives for diesel fuels.

For many years, nitric esters of monohydric alcohols, such as, for example, amyl nitrate, hexyl nitrate, octyl nitrate, etc., have been used as agents that increase the cetane number of diesel fuels.

However, only nitrates of aliphatic and alicyclic alcohols, such as 2-ethylhexyl nitrate and cyclohexyl nitrate and some organic peroxides, found practical application from them (Danilov A.M. Handbook. Use of additives in fuels for automobiles. M: Chemistry, 2000, 227 pp.).

Any technological process for producing nitroesters includes the following stages: - preparation of nitrating mixtures; preparation of starting alcohols and their mixtures; preparation of washing liquids; nitration of alcohols; separation of acid nitroester from spent acid; washing the acid nitroester with washing liquids; waste acid recycling.

Although nitroesters of monohydric alcohols as such do not belong to explosive substances and have a fairly high stability, nevertheless, their production is associated with certain risks. Acids worked out in the nitration process partially lose stability and can decompose in an uncontrolled manner. In addition, during the nitration process, intense oxidative decomposition reactions of the product can occur, accompanied by smoke or even explosion.

A known method of producing 2-ethylhexyl nitrate by the continuous method (RU 2259348 C1, publ. 08/27/2005), which consists in treating 2-ethylhexanol with sulfur-nitrogen mixtures of the composition (wt.%) H ₂ SO ₄ - 60-45, HNO ₃ - 10- 25; nitrogen oxides - 0.0001-0.1; water is the rest. Nitration is carried out in an ideal displacement reactor at a temperature of 15-40 ° C, a residence time of 2-5 minutes and a volume module of the acid mixture / 2-ethylhexanol 1.6 / 1-2.3 / 1. The yield of 2-ethylhexyl nitrate is not lower than 99.5%. The content of the basic substance is not less than 99.5%, the content of 2-ethylhexanol is not more than 0.5%.

The disadvantage of this method of obtaining 2-ethylhexyl nitrate is:

- a complex, dangerous process of industrial production, great difficulties in implementation on an industrial scale due to complex hardware design, an increased amount of waste acid formed.

The prior art also knows a method for producing alkyl nitrate, specifically 2-ethylhexyl nitrate (US 5162568) by nitration of 2-ethylhexanol with a nitrating mixture containing (wt.%) Nitric acid - 20-30, sulfuric acid - 55-60. water - 15-20, the process is carried out using a stabilizer, in this case urea (urea) - 2.0-5.0. The reaction is carried out at a temperature of 15 ° -45 ° C with continuous stirring and cooling of the reaction mass. After separation of the target product from the spent acids, it is washed successively twice with an aqueous solution of sodium sulfate and once with a solution of a mixture of sulfate and sodium carbonate in a ratio of 1: 1. using at each washing 2 parts of 2-ethylhexyl nitrate 1 part of a solution of salts.

The disadvantage of this method is the high consumption of washing solutions of salts, which leads to large losses of the target product, low stability and stability of the nitration process, which requires continuous cooling of the reaction mass. For cooling, a specially prepared composition (brine) is required, which complicates the method.

The closest analogue of the claimed technical solution is a method for producing a cetane-raising additive based on 2-ethylhexanol (RU 2235118 C1, publ. 08/27/2004), nitration with a mixture of nitric and sulfuric acids at a temperature of 8-18 ° C for 2.5-1.5 hours . In this case, the supply of reagents and raw materials to the reactor is carried out in a certain order - first, urea is loaded into the cooled reactor, then, with constant cooling and stirring, a previously prepared mixture of sulfur and nitrogen is metered separately at a speed of 0.30-0.60 g / min acids and a fraction isolated from the bottom residue of the production of butyl alcohols. The obtained target product is separated from the spent acid and washed twice with a solution of salts obtained by neutralization of the spent acid and once with the same solution with the addition of sodium hydroxide solution, with 3 wt. parts of a solution of salts are added per 10 wt. parts of the target product.

The disadvantage of this method is its increased danger, firstly, because of the need to strictly maintain the ratio when dosing the two main components in time, because if the dosage is violated, the risk of self-decomposition of the nitro ester increases, which is accelerated by the released nitrogen oxides, and secondly, due to the duration of the nitration process itself.

In addition, the disadvantages of the process are the use of inaccessible raw materials, the use of a large amount of washing water, as well as the presence of additional stages - cooling the reaction mass and neutralizing the spent acids to obtain salts used for washing the acid nitroester.

The technical task of the invention is to simplify the method and reduce its danger by reducing the residence time of the reaction mixture, reducing the amount of wash water, involving waste acids in the production process, as well as the availability of raw materials and the expansion of the raw material base.

The stated technical problem is solved by the fact that a method for producing esters of monohydric alcohols is proposed by treating them with a sulfuric-nitric acid mixture in the presence of urea, separating the acid nitroester and then washing it, in which 2-ethylhexanol and / or isoamyl alcohol are used as the monohydric alcohol, as a sulfuric-nitric acid mixture using a mixture of the composition, wt.% HNO ₃ - 18,0-21,0; H ₂ SO ₄ - 62.0-65.0; water - the rest is up to 100, which is prepared from 99.8% HNO ₃ , 93.4% H ₂ SO ₄ and spent acid obtained in the nitration process. In this case, the treatment with sulfuric-nitric acid mixture is carried out at a temperature not exceeding 25-30 ° C for 25-30 minutes, and the washing of the acid nitroester is carried out first with washing water at a ratio of: product: washing water 1: 0.5, and then 2% sodium hydroxide solution in a ratio of 1: 0.3.

Thus, common with the closest analogue is the use of 2-ethylhexanol-containing raw materials, the process of nitration with a sulfuric-nitric acid mixture in the presence of urea, the presence of stages of separation of the organic layer - the product of nitration from spent acids, and washing the acid nitroester.

Distinctive features of the proposed technical solution is the use of other, more affordable, raw materials, the use in the process of sulfur-nitrogen nitrating mixtures of a certain composition, which are prepared using waste acids, the nitration process in other modes.

The use in the method for producing nitroesters of sulfuric acid nitrating mixtures of the claimed composition, which are prepared using spent acid, allows the nitration process to be carried out at a temperature of 25-30 ° C. and a time of 25-30 minutes, which reduces the risk of the process by reducing the residence time of the nitromass in the reactor and simplifies the process by eliminating the stages of neutralization of spent acids, preparing a cooling brine and a sharp decrease in the number of washes. The use of washing water allows you to speed up the separation process due to the difference in the densities of the target product and water.

The invention is illustrated by examples of specific implementation, which should not serve as the basis for limiting the claims of the applicant, but should be considered solely as examples confirming the possibility of carrying out the invention with the achievement of the specified technical result.

Example 1

Obtaining isoamyl nitrate is carried out by nitration of isoamyl alcohol with sulfuric-nitric acid mixture composition, wt.%: HNO ₃ - 18.6; H ₂ SO ₄ - 62.2; H ₂ O - 19.2, urea - 1.5% by weight of the acid mixture.

In a reactor equipped with a stirrer, a coil and a thermometer, an acid mixture of a given composition is prepared from 0.94 kg of water, 12.5 kg of spent acid (composition, wt.%: НNО ₃ - 3.4; H ₂ SO ₄ - 69.4; H ₂ O - 27.2), 4.26 kg of nitric acid with a concentration of 99.8%, 7.49 kg of sulfuric acid with a concentration of 93.4%. 0.375 kg of urea are loaded into the prepared acid mixture with stirring and at a temperature not exceeding 30 ° C, after dissolution of which 5.0 kg of isoamyl alcohol is dosed.

The reaction mixture was kept at 25-30 ° C for 30 minutes, after which the organic layer was separated from spent acids. The acidic organic layer is washed with wash water (0.5 parts by weight of water per 1 part of the product), separated, followed by repeated washing with a 2% sodium hydroxide solution (0.3 wt. Per 1 part of the product). parts of the solution) are separated. Dried at 60 ° C. The yield of the finished product was 98.5% with a basic substance content of 98.4%.

Example 2

Obtaining 2-ethylhexyl nitrate.

Obtaining 2-ethylhexyl nitrate is carried out by nitration of 2-ethylhexanol with a sulfuric-nitric acid mixture with the composition, wt.%: НNО ₃ - 20.6; H ₂ SO ₄ - 62.7; H ₂ O — 16.7; carbamide - 1.5% by weight of the acid mixture.

In a reactor equipped with a stirrer, a coil and a thermometer, an acid mixture is prepared in an amount of 190 kg from - 99.8% HNO ₃ - 91 kg, 93.4% H ₂ SO ₄ - 99.0 kg. The mixture is stirred for 10 min, cooled to 30 ° C and a pre-prepared solution of 10 kg of urea in 300 kg of spent acid is metered (spent acid composition, wt.%: НNO ₃ - 3.4; H ₂ SO ₄ - 69.4; H ₂ O - 27.2) . The contents of the reactor are stirred for 10 minutes and 160 kg of 2-ethylhexanol are metered at a temperature not exceeding 30 ° C. To complete the nitration reaction, an exposure time of 30 minutes is given, after which the organic layer is separated from the spent acid. The acidic product is washed with washing water in a mass ratio: product: water 1: 0.5, separated. Then washed repeatedly with a 2% sodium hydroxide solution; for 1 wt. part of the product take 0.3 wt. parts of the solution are separated. The target product is dried by heating to 60 ° C. The yield of the target product is 98.8% with a basic substance content of 99.8%.

Example 3

Obtaining a mixed nitroether.

Obtaining a mixed nitroether is carried out by nitration of a mixture of isoamyl alcohol and 2-ethylhexanol in a mass ratio of 1: 1 sulfuric-nitric acid mixture composition, wt.%: HNO ₃ - 19.4; H ₂ SO ₄ - 62.0; H ₂ O — 18.6, urea — 1.5% by weight of the acid mixture.

An acid mixture of 99.8% HNO ₃ - 34.2 kg and 93.4% H ₂ SO ₄ - 39.5 kg is prepared in a reactor equipped with a thermometer, a coil and a stirrer. At a temperature not exceeding 30 ° C, a solution of urea in spent acid is dosed to the acid mixture (3 kg of urea in 120 kg of spent acid of the composition, wt.%: НNO ₃ - 2.8; N ₂ SO ₄ - 67.2; H ₂ SO ₄ - 67.2; H ₂ O - 30.0). After mixing the mass for 15 minutes at a temperature not exceeding 30 ° C, 55 kg of pre-mixed alcohols are metered, after which an additional 15 minutes are allowed to complete the nitration reaction. Then, the organic layer is separated from the spent acid. The acidic product is washed similarly to examples 1 and 2. The washed target product is dried at 60 ° C. The total yield of the target product is 98.5% (50.8% of 2-ethylhexyl nitrate and 48.7% of isoamyl nitrate).

Thus, the proposed method for the production of monohydric alcohol nitroesters is safe, it allows to obtain the target product with a yield of at least 98.5% with a basic substance content of 99.5-99.8%, while reducing the time of the method and the number of washes. Moreover, the method allows to involve up to 50% of the spent acids in the technological process, and to drastically reduce the amount of wash water.

Claims (1)

A method of producing monohydric alcohol nitroesters by treating a monohydric alcohol with a sulfuric-nitric acid mixture in the presence of urea, separating an acidic nitroester and then washing it, characterized in that 2-ethylhexanol and / or isoamyl alcohol are used as the monohydric alcohol, as sulfuric nitric acid mixtures use a mixture of the composition, wt.%: HNO ₃ - 18.0-21.0 H ₂ SO ₄ - 62.0-65.0 water - the rest is up to 100, which is prepared from 99.8% HNO ₃ , 93 , a 4% H ₂ SO ₄ and the waste acid produced during the nitration, the processing The sulfuric-nitric acid mixture is carried out at a temperature not exceeding 25-30 ° C for 25-30 minutes, and the acidic nitroester obtained is washed first with washing water at a mass ratio of product: washing water 1: 0.5, and then with a 2% solution sodium hydroxide in a mass ratio of 1: 0.3.