Patent GB-344482-A (GB)
Title: Improved manufacture of acetic anhydride
IPC: C07C51/56
Filed: 1929-11-28
Abstract: Catalysts for the production of acetic anhydride from the vapour of acetic acid consist of copper or silver or their compounds supported upon or mixed with a siliceous carrier such as pumice, asbestos, biscuit porcelain or colloidal silica, or tungstic acid.  The copper or silver compound may be precipitated upon the siliceous carrier or used to impregnate it, or yellow tungstic acid may be mixed with for example copper acetate or basic copper carbonate.  The copper or silver compounds may be such as are at least partially reduced to the metallic state during the process, or the catalyst may be given a preliminary reducing treatment.  Suitable compounds of copper and silver are the oxides, hydroxides, carbonates, chlorides, and phosphates. The following catalysts are mentioned:--asbestos freed from iron, and impregnated with copper chloride, and dried; copper carbonate precipitated on pumice which has been freed from iron by boiling in acids; and silver hydroxide precipitated upon pumice which has been freed from iron.  Specification 314,555, [Class 1 (i), Chemical processes &c.], is referred to.  The Specification as open to inspection under Sect. 91 (3) (a) includes the use of any catalyst which produces too far-reaching an effect, such as siliceous substances above-mentioned and tungstic acid, together with any substance which limits such action to the desired extent.  This subject-matter does not appear in the Specification as accepted.ALSO:Acetic anhydride is obtained by passing the vapour of acetic acid over a catalyst consisting of copper, silver, or a copper or silver compound supported upon or mixed with either a siliceous material such as pumice, asbestos, biscuit porcelain or colloidal silica, or tungstic acid.  The copper or silver compound may be precipitated upon the siliceous carrier or used to impregnate it, p or yellow tungstic acid may be mixed with, for instance, copper acetate or basic copper carbonate.  The copper or silver compounds may be such as are at least partially reduced to the metallic state during the process, or the catalyst may be given a reducing treatment before use.  Suitable compounds of copper and silver are the oxides, hydroxides, carbonates, chlorides and phosphates.  The process may be effected at 650-750 DEG  C.  Examples describe the use of the following catalysts: asbestos freed from iron, impregnated with copper chloride and dried; copper carbonate precipitated on pumice which has been freed from iron by boiling in acids, and silver hydroxide precipitated on pumice which has been freed from iron.  The life of the catalysts can be prolonged by mixing a small proportion of oxygen or air with the acetic acid, and regeneration may be effected by passing gases containing oxygen, such as air, over the catalysts.  Specification 314,555, [Class 2 (iii), Dyes &c.], is referred to.  The Specification as open to inspection under Sect. 91 (3) (a) includes the use of any catalyst which produces too far-reaching an effect, such as siliceous substances above-mentioned and tungstic acid together with any substance which limits such action to the desired extent.  This subject-matter does not appear in the Specification as accepted.