Improvements in or relating to catalyst recovery process

摘要

In the liquid phase air oxidation of xylenes to produce toluic acids in the presence of a cobalt, manganese, or cerium salt catalyst, the mixture of reaction products is maintained at 120-200 DEG C. while saturated with water and in contact with a gas containing no more than about 4 per cent by volume of oxygen, in order to precipitate the catalyst. Precipitation may take place in 1-15 minutes, and the catalyst is then filtered off and used again in the process. When a cobalt salt is used, e.g. cobaltous toluate, the cobaltic salts formed during the reaction are reduced to insoluble hydrated cobaltous salts. After separation of the catalyst, purified toluic acids may be obtained as described in Speci738,801. In examples, the reaction is carried out (1) in a stirred autoclave at 160 DEG C. and 200 p.s.i.g. pressure, the catalyst being precipitated in 10 minutes after stopping the air flow; (2) by countercurrent contact of air with a xylene fraction containing the catalyst in an oxidation tower at 153 DEG C. and 200 p.s.i.g. pressure, the product being withdrawn to a surge tank where it is blanketed by the effluent gas stream, and then filtered to remove precipitated catalyst. The xylenes may be prepared by hydroforming petroleum naphtha, and may contain ethyl benzene which is oxidized to acetophenone.ALSO:Catalyst is recovered from the reaction mixture produced by the liquid phase air oxidation of xylenes to produce toluic acids in the presence of a cobalt, manganese or cerium salt catalyst, by maintaining the mixture of reaction products at 120 DEG -200 DEG C while saturated with water and in contact with a gas containing no more than about 4 per cent by volume of oxygen, in order to precipitate the catalyst. Precipitation may take place in 1-15 minutes, and the catalyst is then filtered off and used again in the process. When a cobalt salt is used, e.g., cobaltous toluate, the cobaltic salts formed during the reaction are reduced to insoluble hydrated cobaltous salts. In examples the reaction is carried out (1) in a stirred autoclave at 160 DEG C and 200 p.s.i.g. pressure, the catalyst being precipitated in 10 minutes after stopping the air flow; (2) by countercurrent contact of air with a xylene fraction containing the catalyst in an oxidation tower at 153 DEG C and 200 p.s.i.g. pressure, the product being withdrawn to a surge tank where it is blanketed by the effluent gas stream, and then filtered to remove precipitated catalyst. Specification 738,801, [Group IV(b)] is referred to.