PL165707B1 - Method of obtaining acetic acid - Google Patents

Abstract

Method for the production of acetic acid by carbonylation of methanol in the presence of rhodium complex in which the mixture is reaction with a mole ratio of methanol / oxide carbon / methyl iodide of 5-10: 18 35: 0.5-2 is contacted with catalyst at temperature 360-450K, under pressure 1 4 MPa, characterized in that it is used as the catalyst the R-Rh (CO) P rhodium complex emerges (C6H5) 3 of the formula in which R. represents the rest of the organic acid possessing from 4 to 18 carbon atoms in the molecule, r an amount such that the converted catalyst concentration per rhodium was 200-1500 ppm.

Description

The present invention relates to a process for the production of acetic acid by carbonylation of methanol using a rhodium complex as a process catalyst.

Rhodium complexes are catalysts for many chemical reactions involving synthesis gas (CO + H 2), but only in the last 15 years they have found wider application in industrial processes, of which the oxo process and methanol carbonylation are among the most important and the largest in terms of tonnage. Despite the high price of rhodium, it is increasingly used due to its high activity and selectivity, and requires mild pressures and low temperatures compared to other catalysts, e.g. cobalt.

The methanol carbonylation reaction in the presence of rhodium complexes is carried out on an industrial scale at a pressure of 2-4 MPa at a temperature of 400-480K with a catalyst concentration of 10 moles, obtaining acetic acid or its methyl ester with selectivity over 99% in terms of methanol and 90% in terms of WHAT. However, in processes where catalysts used are cobalt carbonyls are used much harsher conditions: pressure 30-70 MPa, temperature of 500-590K, the catalyst concentration of 10 ^-1 mole, and the product contains a number of by-products. The synthesis of acetic acid from methanol and carbon monoxide is carried out in the liquid phase in the presence of a rhodium complex with the addition of methyl iodide, by passing carbon monoxide through methanol. Rhodium catalysts supported on various solid supports are also known.

The method of methanol carbonylation in the liquid phase is known from the British Patent No. 1,362,997, where the reaction is carried out in the presence of rhodium complexes of the formula {Rh P [OPh / a] r} KA, {Rh [PPh3] r} KA, where r = 2,4 or 5, K-integer, A is PO 4 3, HPO 4 ', 2 H2PO4 ^{-1, 2} SO4, CIO4 or HSO4- ^{1 "1-Ph} phenyl radical. Using this complex, 95% conversion of methanol into acetic acid was obtained at a temperature of 323-573K and a pressure of several MPa.

According to USSR Patent No. 1 108088-A, in the carbonylation of methanol, a rhodium catalyst is used, obtained from rhodium chloride, bromide or nitrate and a carbon monoxide polymer with a molecular weight of 10,000-60,000, and the carbonylation process takes place at a temperature of 453-483K under a pressure of 10 MPa. . The Polish patent description 153,615 describes the carbonylation of methanol to acetic acid at the temperature of 380-460K under the pressure of 1-5 MPa, in the presence of the Rh [CO] [CsH7O2] P [CsH5] 3 rhodium complex, achieving process selectivity of 80%.

The essential aspect of the present invention is that the methanol carbonylation process is carried out at a pressure of 1-4 MPa at a temperature of 360-450K with the molar composition of the reaction mixture methanol: carbon monoxide: methyl iodide being 5-10: 18-35: 0.5-2 in the presence of the rhodium R-Rh [CO] P [CeHs] 3 complex of the formula in which R is an organic acid residue with 4 to 18 carbon atoms at a catalyst concentration based on rhodium 200-1500 ppm. The carbonylation process carried out in this way ensures high methanol conversion and high process selectivity. The process conditions and product yield are shown in the examples below.

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Example I. Methanol was introduced into a reactor with an internal diameter of 14 mm and a length of 5500 mm, placed in a liquid bath at the desired process temperature, and after filling the reactor, the rhodium complex CH 3 [CH2] 2 COORh [CO] P [CeH 5) 3 dissolved in methyl iodide and from the bottom carbon monoxide was introduced through a brass sinter. The process was carried out at a pressure of 4 MPa and a temperature of 350K with a methanol / CO / CH 3 J molar ratio of 5/18/2 / at a catalyst concentration calculated as Rh 1500 ppm. The test results are presented in Table 1.

Example II. Into the reactor as in example I, at a temperature of 450K, the reaction mixture was introduced at a pressure of 2 MPa, with a molar ratio of methanol (CO) CHsJ equal to 10/35/05, with the catalyst concentration CH3 [CH2] e COORh [CO] P [CeHa] 3, calculated as on Rh 200 ppm. The results obtained are given in Table 1.

Example III. To the reactor as in example I, at the temperature of 430K, the reaction mixture was introduced at a pressure of 4 MPa with a molar ratio of methanol CO (CH3OH) CH3J of 25/7/1 in the presence of the rhodium complex CH3 [CH] 4 COORh [CO] P [CeHs] 3 in rhodium concentration of 1000 ppm. The results are given in Table 1.

Example IV (comparative). To the reactor as in example 1, at the temperature of 430K, the reaction mixture with the composition as in example 3 was introduced at a pressure of 4 MPa in the presence of the RhCl3 catalyst (from Monsanto) with a concentration calculated as Rh of 1000 ppm. The results are given in Table 1.

Example 5 (comparative). To the reactor as in example I, in the parameters as in example III, the reaction mixture with the composition as in example III was introduced in the presence of the catalyst Rh [CO] [C5H7O2] P [CeH5) 3 (according to the Polish patent 153615) with a concentration calculated as Rh 1000 ppm. The results of the carbonylation processes carried out are given in Table 1.

Table 1

No. Catalyst Pressure- no MPa Tempe- rature K. Molar ratio Yield mole% CH3OH WHAT CH3J CH3 COOH CH3 COO CH3 CH3 CH2 COOH 1. CH 3 [CH _{2] 2} COORh [CO] P [C6H5] 3 1500 ppm Rh 4 360 5 18 2 70.1 8.8 3.5 2. CH ₃ [CH ₂ ], 6 COORh [CO] P [C6H5] 3 200 ppm Rh 2 450 10 35 0.5 71.3 7.2 2.4 3. CH ₃ [CH2] - COORh [CO] P [C6H5] 3 1000 ppm Rh 4 430 25 7 1 89.4 5.1 1.8 4. RhClo · 3H2O 1000 ppm Rh 4 430 25 7 1 70.2 14.4 4.8 5. Rh [CO] [C5H7O2] P [C6H5] 3 1000 ppm Rh 4 430 25 7 1 77.1 11.3 5.0

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Publishing Department of the UP RP. Circulation of 90 copies

Price: PLN 10,000

Claims (1)

Patent claim A method for the production of acetic acid by carbonylation of methanol in the presence of a rhodium complex, in which the reaction mixture with a molar ratio of methanol / carbon monoxide / methyl iodide of 5-10: 18-35: 0.5-2 is contacted with the catalyst at a temperature of 360-450K, at a pressure of 1-4 MPa, characterized in that the catalyst is the R-Rh (CO) P (CsHs) 3 rhodium complex of the formula in the figure, in which R is the rest of an organic acid having from 4 to 18 carbon atoms in the molecule, in such an amount that the concentration of the catalyst, calculated as rhodium, is 200-1500 ppm.