RU2377232C2 - Method of producing methyl formate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to organic synthesis, specifically to a method of producing methyl formate, which is used as an intermediate product during synthesis of organic acids such as formic acid, acetic acid, propionic acid and esters thereof, as well as an additive to diesel fuel. The method of producing methyl formate from a gas which contains a mixture of carbon oxide and hydrogen involves treating the mixture of hydrogen and carbon oxide with alkali with formation of an alkali metal formate and purified hydrogen. The obtained alkali metal formate is then dissolved in water and treated with sulphuric acid with formation of formic acid, while separating sulphur impurities, and the formic acid is reduced to methanol with hydrogen using a hydrogenation catalyst. The formic acid is reduced until conversion of 50-90 mol %. The cooled mixture of methanol and formic acid is rectified in the presence of an acid catalyst, while esterifying the reaction to methyl formate.

EFFECT: increased output of high-quality end product while using material with various degree of purity.

7 cl, 2 ex

Description

The invention relates to the field of industrial organic synthesis technology, in particular to methods for producing methyl formate used as an intermediate in the production of organic acids - formic, acetic, propionic and their esters and as additives to diesel fuels.

A known method of producing methyl formate / RF Patent No. 2126788, С07С 69/06, С07С 67/36, С07С 51/12, С07С 31/40, 1999 / by carbonylation of methyl alcohol with carbon monoxide using 0.2-6 as a catalyst , 0% sodium or potassium methylate by weight of the reaction mixture, at elevated temperature and pressure, characterized in that 0.005-0.15 mol / L sodium or potassium oxperfluoro-cansulfonate is added to the reaction mixture.

A known method of producing methyl formate / RF Patent No. 2185370, C07C 69/06, C07C 67/00, B01J 23/72, B01J 37/08, B01J 35/00, 2002 /. Methyl formate is obtained by dehydrogenation of methyl alcohol in the gas phase at a temperature of 150-350 ° C and atmospheric pressure in the presence of a copper-containing catalyst, the content of elements in which, in terms of metals, is at.%: Copper 10-30, zinc 10-50, aluminum and / or chromium and / or zirconium or silicon.

A known method of producing methyl formate / Patent Germany N 3221239, C07C 69/06, 1983 /. Methyl formate is obtained by carbonylation of methyl alcohol in the presence of alkaline alcoholates and additives of olefin oxide hydrate oligomers of the general formula HO (CH ₂ CHRO) _n H, where R = H or CH ₃ and n = 2-1000, as well as pyridine additives in the carbonylation reaction mixture. The process is carried out at 60-120 ° C and a pressure of carbon monoxide below 3.0 MPa, the concentration of sodium methylate is 2-6 wt.%. Additives of oligomers of olefin oxide hydrates slow down the precipitation of catalyst decomposition products in the reaction apparatus, thereby eliminating the risk of clogging and it becomes possible to separate the solid precipitate at one point in the technological scheme (on the filter). When using pyridine together with oligomers of olefin oxide hydrates and sodium methylate as a catalytic system for carbonylation of methyl alcohol, there is a slight increase in the process productivity (removal of methyl formate 110-200 g / l per hour).

The closest analogue is a method for producing methyl alcohol and methyl formate / RF Application No. 94038634, С07С 29/156, С07С 31/04, 1996 /. The method is carried out by reacting carbon monoxide and hydrogen at 50-120 ° C and a pressure of 5-100 atm in the presence of a catalytic system comprising an organic acid nickel A salt and an alkali metal B methylate with a molar ratio B: A equal to 5:10, with or without tertiary alcohol and / or D-water, the molar ratio of D: A is up to 2.5.

A disadvantage of the known methods is the insufficiently high yield of the finished product, the use of catalysts not manufactured by the industry, the low quality of the finished product and high requirements for the purity of raw materials (in particular, sulfur content).

The objective of the invention is to provide a method that allows to increase the yield of the finished product with high quality, use industrially produced catalysts.

The problem is achieved in that in the method for producing methyl formate from a gas containing a mixture of carbon monoxide and hydrogen, a mixture of hydrogen and carbon monoxide, is treated with alkali to form alkali metal formate and purified hydrogen, then the obtained alkali metal formate is dissolved in water and treated with sulfuric acid with the formation of formic acid, while separating sulfur impurities, which is reduced to methyl alcohol with hydrogen using a hydrogenation catalyst, where the recovery of ants oh acid is carried out to a conversion of 50-90 mol.%, cooled mixture of formic acid and methyl alcohol rectified in the presence of an acid catalyst to methyl formate by reacting eterifitsiruya.

The resulting mixture in the presence of an acid catalyst is subjected to etherification without separation.

The sulfate obtained by dissolving an alkali metal formate in water and treating with sulfuric acid is regenerated by treating with a constant electric current in a membrane electrolyzer, acid is obtained from the anolyte.

After treatment of the alkali metal formate with an acid, sulfur impurities are separated from formic acid during distillation in the form of hydrogen sulfide.

After treatment of the alkali metal formate with sulfuric acid, the reaction mixture is cooled to crystallize the alkali metal sulfate hydrate, and the liquid formic acid is separated from the solid crystalline hydrate by decantation or filtration.

During the processing of a mixture of methyl alcohol and formic acid on an esterification catalyst, the reaction mixture is repeatedly passed sequentially through a catalyst bed, a desiccant.

During the treatment with formic acid on a hydrogen reduction catalyst, the reaction mixture is repeatedly passed sequentially through a catalyst bed, a desiccant.

The method is as follows.

Solid, liquid or gaseous carbon-containing raw materials are gasified with water vapor at a temperature of 800-1100 ° С, thus obtaining a mixture of carbon monoxide with hydrogen. Below 800 ° С the reaction is too slow, above 1000 ° С ash is sintered and incomplete conversion is observed. The mixture may contain impurities: nitrogen, ammonia, hydrogen sulfide and other impurities. This gas is called water. Water gas can be produced by reacting water vapor with coal, associated gas, natural gas, oil, peat or other carbonaceous material or waste. The gas is treated with an alkali melt under a pressure of 5 atm to form an alkali metal formate (sodium or potassium) according to reaction 1:

Hydrogen sulfide is absorbed by alkali according to the formula 2.

Purified hydrogen under pressure is subsequently used for hydrogenation.

The alkali metal formate in the form of an aqueous solution is treated with sulfuric acid with strong cooling - formula 3.

In this case, the concentration of formate and sulfuric acid (in the form of aqueous solutions) is chosen so that crystalline hydrate Na ₂ SO ₄ · 10H ₂ O (Glauber's salt) and formic acid, or the corresponding analogue with potassium, are formed. After cooling the reaction mass, the crystalline hydrate crystallizes and is separated by decantation or filtration.

Formic acid is reduced with purified hydrogen to methyl alcohol above the catalyst (Raney nickel, platinum, palladium or other industrially produced catalysts) by passing formic acid vapors above its boiling point (100.8 ° C) with hydrogen above the catalyst at a rate that ensures a given conversion ( from 50 to 90%) according to reaction 4.

A mixture of methyl alcohol with formic acid is subjected to rectification in the presence of an acid catalyst, for example, sulfonic cation exchanger KU-2 × 8 KU-23P, and the esterification reaction 5 occurs.

Water is separated on a distillation column, shifting the equilibrium towards the reaction product (methyl formate). A mixture of methyl alcohol with methyl formate (light fraction of distillation) is used as liquid fuel. By changing the conversion through the transmission rate through the column with the catalyst, the quality of the fuel (cetane number) is controlled by the ratio of methyl alcohol to methyl formate in the finished product.

Sodium sulfate (potassium) in the form of a crystalline hydrate is melted by heating to 60 ° C, placed in a membrane electrolyzer. During electrolysis in the anode space, acid formation occurs by reactions 6.

In the cathode space - alkali 7.

After evaporation, alkali is used to absorb carbon monoxide, and acid to produce formic acid.

Example 1

Through a brown quartz tube (12 g). Placed in a tube furnace with a temperature of 1000 ° C, water vapor (18 g) is passed. The resulting water gas is fed into a tube with ground sodium hydroxide (alkali) in an amount (40 g), at a pressure of 5 atm and at a temperature of 100-150 ° C. The white sodium hydroxide powder turns into a light yellow sodium formate. After 1 hour, the tube is weighed, 68 g of sodium formate is obtained. Hydrogen was collected in an aspirator (22.3 L). Sodium formate is dissolved in water and mixed with 40% sulfuric acid (125 g) under strong cooling (0 ° C). During the reaction, heat is generated, which is removed by cooling the reactor with ice. After the reaction, crystalline hydrate precipitates in the form of large white crystals. The mother liquor is decanted. 45 g of formic acid (crude) and 148 g of crystalline hydrate (glauber's salt) are obtained. Formic acid is distilled. During distillation, hydrogen sulfide is released.

Formic acid (45 g) was placed in a flask; the flask was heated to boiling point (100.8 ° С). Hydrogen is passed through the flask by bubbling from an aspirator. The vapors are dried with anhydrous silica gel in a column, then passed through a 5 g quartz tube with Raney nickel at 200 ° C. The vapors are cooled in the refrigerator, collecting the liquid fraction containing 23 g of formic acid and 16 g of methyl alcohol. The mixture was dried with anhydrous silica gel, distilled in a distillation column filled with KU-23P cation exchange resin and silica gel packed in three separate layers each, separating methyl formate from water. A desiccant extracts water from the vapor phase, contributing to the production of methyl formate. Obtain 30 g of methyl formate (light fraction). The content of the basic substance is 99.2 wt.%. Yield from theoretical 99%.

In an electrolyzer with a cation exchange membrane MK, an anionic membrane MA, two electrodes of electrotechnical graphite with an area of 25 cm ^2, Glauber salt is placed in a central chamber. Water in an amount of 100 g is placed in the anode and cathode chambers. They apply a voltage of 44 V. The salt heats up, melts. Electrolysis lasts 18 hours at a current of 3 A. 4 g of potassium sulfate in 100 g of water remain in the central chamber, 38 g of alkali in 100 g of solution in the cathode chamber, 4 g of sulfuric acid in 100 g of solution in the anode chamber. Part of the water evaporates. The alkali is evaporated to dryness and crushed. Silica gel is dried in an oven.

Example 2

In example 1, instead of alkali, caustic potassium (KOH) is used in an amount of 57 g to obtain a mixture containing 27 g of methyl formate and 3 g of methyl alcohol. Product purity 90%. Yield from theoretical 99%.

The proposed method allows due to sequentially conducted reactions to increase the yield of the finished product, as well as to obtain a product with high quality, using raw materials of various degrees of purity.

Claims (7)

1. A method of producing methyl formate from a gas containing a mixture of carbon monoxide and hydrogen, characterized in that the mixture of hydrogen and carbon monoxide is treated with alkali to form alkali metal formate and purified hydrogen, then the obtained alkali metal formate is dissolved in water and treated with sulfuric acid to form formic acid, while separating sulfur impurities, which is reduced to methyl alcohol with hydrogen using a hydrogenation catalyst, where the reduction of formic acid carried out they are found to be 50-90 mol% before conversion, the cooled mixture of methyl alcohol and formic acid is rectified in the presence of an acid catalyst, esterifying the reaction to methyl formate. 2. The method according to claim 1, characterized in that the resulting mixture in the presence of an acid catalyst is subjected to esterification without separation. 3. The method according to claim 1, characterized in that the sulfate is obtained by dissolving an alkali metal formate in water and treating it with sulfuric acid by treating it with direct electric current in a membrane electrolyzer, and an acid is obtained from the anolyte. 4. The method according to claim 1, characterized in that after processing the alkali metal formate with acid, sulfur impurities are separated from formic acid in the process of distillation in the form of hydrogen sulfide. 5. The method according to claim 1, characterized in that after processing the alkali metal formate with sulfuric acid, the reaction mixture is cooled to crystallize the alkali metal sulfate hydrate, and the liquid formic acid is separated from the solid crystalline hydrate by decantation or filtration. 6. The method according to claim 3, characterized in that during the processing of a mixture of methyl alcohol and formic acid on an esterification catalyst, the reaction mixture is repeatedly passed successively through a catalyst bed, a desiccant. 7. The method according to claim 1, characterized in that during the treatment with formic acid on a hydrogen reduction catalyst, the reaction mixture is successively passed through a desiccant layer.