The method of producing acetate and the catalyst for its implementation

 

(57) Abstract:

The invention relates to a method of producing acetate. The method is carried out by carbonylation of dimethyl ether in the gas phase at elevated pressure, at a temperature of 200 - 250oC, in the presence of a catalyst, which is used as an acidic cesium salt fosfornomolibdenovoi heteroalicyclic composition CsxHyPW12O40where 1.5 x 2, y = 3 - x, with the addition of rhodium in an amount of from 0.1 to 2.5 wt.%. The technical result is an increase in the yield of methyl acetate in the reaction carbonyliron dimethyl ether without using a halogen-containing promoters. 2 S. and 1 C.p. f-crystals, 1 table.

The invention relates to methods for ester acetic acid (acetate) by carbonylation of dimethyl ether in the gas phase in the presence of a catalyst.

Acetic acid and its esters are large-tonnage products basic organic chemistry and are widely used in industrial syntheses and processes. World production of acetic acid is 7.0 million tons per year.

Prior to 1995, more than 60% acetic acid in the world were received by known techniques of liquid-phase carbonylation of methanol on the>to Acetyls: Catalysis and Process, Catal. Today, 18 (1993) 325].

This process is carried out only in the presence of halogen promoters, mainly under the conditions that require the use of special alloys due to their high corrosivity. You also need a thorough separation of the catalyst and iodide from the target product, which is an intermediate for many organic syntheses.

The advantage of gas-phase carbonylation is that the separation of products from catalyst is easy, but the main problems associated with the use of iodide-containing promoters, remain [M. J. Howard, G. J. Sunley, A. D. Poole, R. J. Watt, B. K. Sharma, New Acetyls Technologies from BP Chemicals, Science and Technology in Catalysis (1998) 61.].

In recent years, for halogen-free gas-phase carbonylation proposed several catalytic systems, the major disadvantages which are very low selectivity and low activity. In the patent [US 4612387, C 07 C 1/20, 16.09.86] the copper-containing zeolite catalysts Cu/H-ZSM-5. Performance acetates for this catalyst was 0.03 g/g cat h and a selectivity of less than 30%.

Higher productivity observed for cobalt-zeolite catalyst, but the reactions of the catalyst synthesis of acetates with selectivity up to 70%, but time stable operation of such a catalyst does not exceed 10 hours, and then changed the direction of reaction, the major product was dimethyl ether [B. Ellis, M. J. Howard, R. W. Joyner, K. N. Reddy, M. B. Padley, W. J. Smith, Heterogeneous Catalysts for the Direct, Halide-free Carbonilation of Methanol, Stud. Sur. Sci. Catal. 101 (1996) 771].

A sufficiently high selectivity, but low activity showed rhodium and iridium salts fosfornomolibdenovoi heteroalicyclic deposited on the silicon oxide [EP 0353722, C 07 C 67/36, 01.08.89]. The performance of the catalysts did not exceed 50-60 g/l h in the carbonylation reaction of methanol and 15-20 g/l h in the reaction, carbonylation of dimethyl ether (prototype).

The problem solved by this invention is an increase in the yield of methyl acetate in the reaction, carbonylation of dimethyl ether without using a halogen-containing promoters.

The task is solved by a method of producing methyl acetate by the carbonylation of dimethyl ether in the gas phase at a temperature of 200-250oC in the presence of a catalyst comprising an acidic cesium salt fosfornomolibdenovoi heteroalicyclic composition CsxHyPW12O40where 1.5 x 2, y = 3-x, with the addition of rhodium, the rhodium content in the catalyst is not lower than 0.1 wt.%. The process is carried out at Yes is carbonyliron dimethyl ether at a temperature of 200-250oC, represents an acidic cesium salt fosfornomolibdenovoi heteroalicyclic composition CsxHyPW12O40where 1.5 x 2, y = 3-x, with the addition of rhodium, the rhodium content not less than 0.1 wt.%.

The proposed method of synthesis of acetate is as follows: dimethyl ether is mixed with carbon monoxide in a desired ratio and passed through the catalyst layers at a pressure of not lower than 5 MPa and a temperature of 180-250oC. the reaction Products are cooled and separated into gaseous and liquid. The condensate is a target product - acetate. Gas mixture of unreacted dimethyl ether and carbon monoxide) is recycled to the reactor.

The proposed method of synthesis differs in that the catalyst to obtain the acetate is an acid cesium salt fosfornomolibdenovoi heterophilically with the addition of rhodium, the rhodium content not less than 0.1 wt.%.

The composition of the catalyst CsxHyPW12O40where 1.5 x 2, y = 3-x. The catalyst produced by the method of deposition, the cesium salt solution is poured under stirring to the mixture of solutions fosfornomolibdenovoi heteroalicyclic and salts of rhodium, combined in a desired ratio. The precipitate of n is i.i.d. samples is 57-100 m2/,

The invention is illustrated by the following examples.

Example 1. Process for the carbonylation of dimethyl ether to methyl acetate is carried out by passing a mixture of dimethyl ether with carbon monoxide through the catalyst bed at a temperature of 200oC and a pressure of 10 ATM, the ratio of DME: CO = 1:10, the gas flow rate 3000 h-1the conversion of dimethyl ether is 22%.

The process is performed on the catalyst comprising an acidic cesium salt fosfornomolibdenovoi heteroalicyclic composition Cs2HPW12O40the rhodium content is 0.1 wt%. The catalyst was prepared by precipitation, the salt solution of cesium nitrate (0.1 M) is poured dropwise with constant stirring to the mixture of solutions fosfornomolibdenovoi heteroalicyclic (0.1 M) and rhodium chloride (0.1 M), combined in a desired ratio. The resulting suspension is stirred for 24 hours, then the precipitate is evaporated, tabletirujut and milled. The fraction of catalyst size 0.5-1 mm is loaded into the reactor. Surface activity and selectivity of the catalyst shown in the table.

Example 2. Analogously to example 1, but the rhodium content is 0.5 wt. %.

Example 3. Similarly, five is 2.5 wt%.

Example 5. Analogously to example 1, but the cesium salt fosfornomolibdenovoi heteroalicyclic has a composition Cs1.5H1.5PW12O40the rhodium content is 1.0 wt.%.

As can be seen from the table, this method ensures that the output acetate 6-9 times higher than the known reaction carbonylation of dimethyl ether without using an iodide promoter.

1. The method of producing methyl acetate by the carbonylation of dimethyl ether in the gas phase at elevated pressure, at a temperature of 200 - 250oC in the presence of a catalyst consisting of salts of heteropolyacids, wherein the carbonylation process to produce a catalyst comprising an acidic cesium salt fosfornomolibdenovoi heteroalicyclic composition CsxHyPW12O40where 1.5 x 2, y = 3 - x, with the addition of rhodium in an amount of from 0.1 to 2.5 wt.%

2. The method according to p. 1, wherein the process is carried out at a pressure below 5 atmospheres.

3. The catalyst of the process of obtaining methyl acetate by the carbonylation of dimethyl ether at elevated pressure, at a temperature of 200 - 250oC, includes salts of heteropolyacids, characterized in that the catalyst PR is SUB>O40where 1.5 x 2, y = 3 - x, with the addition of rhodium in an amount of from 0.1 to 2.5 wt.%.

 

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