Patent GB-283989-A (GB)
Title: Improvements in or relating to the manufacture of oxygencontaining carbon compounds
IPC: C07C51/12
Filed: 1926-07-20
Abstract: 283,989. British Celanese, Ltd., Dreyfus, H., and Bader, W. July 20, 1926. Acetic and other fatty acids and their esters; ethers; acetone.-Acetic acid is obtained either in the free state or in the form of its methyl ester by heating methyl alcohol with carbon monoxide in the presence of an inorganic acid or an inorganic acid containing an organic group e.g. a sulphonic acid, the acid being present either in the free state or in the form of an acid salt. The! methyl alcohol may be replaced wholly or in part by compounds comprising one or more separable methoxy groups, or by substances capable of generating methyl alcohol, e.g. a methyl ether, or a methyl ester such as methyl formate or acetate. The process may be carried out at atmospheric pressure, but preferably higher pressures, up to 300 atmospheres or more, are employed. The temperatures employed are preferably between 300‹ C. and 400‹ C. The phosphoric acidsortho, pyro, or meta-or mixtures of them are particularly suitable for use as catalysts: boric, arsenic, and phosphomolybdic acids and acid aluminium phosphate are also specified. The catalysts may be used in the liquid or solid state and may be distributed over or supported on an inert solid carrier, e.g. coke or graphite. The catalysts may also be added during the reaction by spraying in the liquid catalyst or by introducing a volatile ester, e.g. a methylester of phosphoric acid, which is decomposed under the conditions of the reaction. The carbon monoxide may be supplied in the, form of industrial or other mixtures, e.g. as water gas, producer gas or coke oven gas, but it is preferable to use carbon monoxide alone. When methyl formate or methyl alcohol are used, the carbon monoxide may be reduced in quantity or even omitted, the carbon monoxide required being formed by decomposition of the formate or alcohol under the conditions of the reaction. The methyl alcohol may be produced synthetically from mixtures of carbon monoxide and hydrogen; thus acetic acid may be obtained by heating a mixture of carbon monoxide first with zinc oxide to form methyl alcohol, and then with an acid catalyst, or it may be formed in a single operation by heating a mixture of carbon monoxide and hydrogen with an acid catalyst. The presence of water in the gaseous mixture favours the production of free acetic acid, while excess of methyl alcohol leads to the production of methyl acetate. The process may be carried on in a continuous manner, the reaction products being cooled and the uncondensed gases recirculated through the reaction chamber. If the acetic acid obtained is intended for the manufacture of acetone, the gases issuing from the reaction chamber may be led directly over acetone-forming catalysts, e.g. manganous oxide at temperature of 400‹- 500‹ C. If methyl acetate is formed by the reaction it may be saponified into acetic acid and methyl alcohol or dimethyl ether, the two latter being returned to the plant for conversion into acetic acid. The different parts of the apparatus are protected against corrosion by acids and carbon monoxide. thus the use of iron, except in the form of alloys that will not form iron carbonyl, should be avoided. The vessels in contact with acetic acid may be made of, or lined with copper, while those containing phosphoric acid may have a lining of graphite or gold, or may be made of or lined with copper. In using copper in contact with phosphoric acid, access of oxygen to the apparatus should be prevented. In examples, (1) carbon monoxide at 100-180 atmospheres is bubbled through methyl alcohol containing water, and the resulting mixture of gases and vapours is passed either (a) through a reaction chamber heated to 300‹-400‹ C. and filled with coke or graphite soaked in phosphoric acid, or with acid aluminium phosphate or (b) through a rotary reaction chamber containing phosphoric acid and graphite pebbles; a mixture of acetic acid and methyl acetate is obtained, (2) anhydrous methyl alcohol is substituted for the methyl alcohol and water, the product obtained being methyl acetate, (3) a mixture of carbon monoxide and hydrogen is passed under a pressure of 150-200 atmospheres through a vessel containing zinc oxide at 300‹-400‹ C.; the resulting mixture is then led, without cooling, over a catalyst as in example (1), a mixture of acetic acid and methyl acetate is obtained, and (4) purified water gas is comprised to 230-300 atmospheres, bubbled through water at 100-150‹ C. and led over an acid catalyst as, in example (1); the acetic acid is condensed from the product, and the uncondensed gases recirculated; nitrogen and other inert gases may be removed from the system either intermittently or continuously and replaced by fresh supplies of water gas. Where methyl acetate is produced; it may be saponified by the method described in Specification 284,582, to form acetic acid and dimethyl ether. Two examples of the saponifying process, agreeing with those of the aforesaid Specification, are given. The saponification of the methyl acetate may be carried out continuously with its production Thus a mixture of carbon monoxide and methyl alcohol vapour may be passed under pressure over phosphoric acid at 300‹-400‹ C., and the products of the reaction, preferably expanded to lower, e.g. atmospheric, pressure passed, together with steam, through a chamber containing phosphoric acid at 180‹-250‹ C. The process may also be extended to higher alcohols, e.g. ethyl alcohol, or their ethers or derivatives to produce the corresponding higher acids, e.g. propionic acid. or their esters. Specification 264,538 also is referred to.