Patent GB-362462-A (GB)
Title: Process for the manufacture of acetic anhydride
Filed: 1930-06-06
Abstract: For the production of acetic anhydride by heating acetic acid vapour there is used a catalytic gel of incomplete surface development prepared by heating the gel to incipient sintering or by treating with a caustic alkali such as ammonia or with an acid such as hydrochloric acid, or by introducing carbon into the pores, and then burning it out by calcination.  Comparative reaction results are given for silica gel precipitated from an acid solution and capable of absorbing 21 per cent of chlorine at 0 DEG  C. as such and also after treatment with ammonia and hydrochloric acid respectively.  The catalysts may be regenerated by heating in air or oxygen or in steam with or without air. Examples are given of the use of silica gel obtained by treating silicon chloride with water and treated with ammonia; a gel from water-glass and hydrochloric acid and treated with hydrochloric acid; an alumina gel as prepared by pouring aluminium sulphate solution into 20 per cent ammonia, and treated with hydrofluoric acid; and platinum precipitated upon a silica gel which has been treated with ammonia as described above. Specification 344,482 is referred to.  The Specification as open to inspection under Sect. 91 (3) (a) includes the use of any catalyst having less than the maximum surface development whether obtained by decreasing the development of a highly developed catalyst or by increasing the development of a less highly-developed form.  Even substances which are thought to be injurious to the reaction may be rendered efficient in this manner.  Substances such as metals may be given a suitable surface development by depositing upon a carrier which already has a suitable form; or the substance may be ground and then formed into tablets.  A mass may be converted from a coarse grained to a fine-grained pore condition, for instance silica gel precipitated from an alkaline medium, may be heated and treated with acids.  Fused alumina may be finely ground and pressed into tablets, which are again ground.  Platinum foil or wire net or platinum precipitated on a gel may also be used.  This subject-matter does not appear in the Specification as accepted.ALSO:Acetic anhydride.--The production of acetic anhydride by heating acetic acid vapour is effected with a catalytic gel of incomplete surface development prepared by heating the gel to incipient sintering, or by treating with a caustic alkali such as ammonia or with an acid such as hydrochloric acid, or by introducing carbon into the pores, and then burning it out by calcination.  Comparative reaction results are given for silica gel precipitated from an acid solution and capable of absorbing 21 per cent of chlorine at 0 DEG  C. as such and also after treatment with ammonia and hydrochloric acid respectively.  The catalysts may be regenerated by heating in air or oxygen or in steam with or without air.  Examples are given of the use of silica gel obtained by treating silicon chloride with water and treated with ammonia; a gel from water-glass and hydrochloric acid and treated with hydrochloric acid; an alumina gel as prepared by pouring aluminium sulphate solution into 20 per cent ammonia, and treated with hydrofluoric acid.  Specification 344,482 is referred to.  The Specification as open to inspection under Sect. 91 (3) (a) includes the use of any catalyst having less than the maximum surface development, whether obtained by decreasing the development of a highly developed catalyst or by increasing the development of a less highly developed form.  Even substances which are thought to be injurious to the reaction may be rendered efficient in this manner. Substances such as metals may be given a suitable surface development by depositing upon a carrier which already has a suitable form; or the substance may be ground and then formed into tablets.  A mass may be converted from a coarse-grained to a fine-grained pore condition, for instance silica gel precipitated from an alkaline medium may be heated and treated with acids.  Fused alumina may be finely ground and pressed into tablets, which are again ground.  Platinum foil or wire net or platinum precipitated on a gel may also be used.  This subject-matter does not appear in the Specification as accepted.