| 摘要 |
1,137,303. Catalytic fluid bed oxidation of o-xylene to phthalic anhydride. CHEMICAL PROCESS CORP. 10 June, 1966 [28 June, 1965], No. 25943/66. Heading C2C. Phthalic anhydride is prepared by reacting o-xylene in the vapour phase with an oxygen containing gas, in the presence of Br 2 , HBr, or a compound capable of dissociation into Br 2 or HBr, as a promoter, in a fluidized bed of a supported catalyst, said catalyst comprising vanadium oxides fluxed with a compound of SO 3 and an alkali metal oxide supported on highly porous silica gel which has a surface area greater than 450 sq. metres/gm. and a mean pore diameter of between 25 and 100 Š. The silica gel preferably has a surface area between 450 and 800 sq. metres/gm., a mean pore diameter between 30 and 90 Š and a bulk density between 0À3 and 0À6 gms./c.c. The supported catalyst may be formed either by applying the catalyst to solid particles of silica, in which case at equilibrium the supported catalyst has a surface area greater than 100 sq. metres/gm. and a pore volume greater than 0À3 c.c./gm., or by adding the catalyst to the silica prior to the formation of solid particles, in which case at equilibrium, the supported catalyst has a surface area greater than 45 sq. metres/gm. and a pore volume greater than 0À25 c.c./gm. In the former case, the weight of catalyst present should not be greater than 45% of the combined weight of catalyst and support; in the latter, not greater than 55%. The reaction temperature is preferably less than 750‹ F.; the ratio of air to o-xylene in the feed should preferably lie between 7: 1 and 20: 1; the amount of promoter (bromine) should preferably be between 0À1 and 5% by weight based on the o-xylene, and the rate of o-xylene feed should preferably exceed 0À025 pounds per pound of supported catalyst. In the catalyst, the molar ratio of SO 3 to alkali metal, preferably potassium, oxide should be greater than 2À2: 1 at equilibrium, the vanadium may be in penta- or tetra-valent forms, between 20 and 60% by weight being penta-valent, and the molar ratio of the alkali metal oxide to said vanadium oxides plus any other oxides to metals which may also be present should preferably lie between 3À3 and 5À2. (Metals exemplified are molybdenum, chromium, tungsten, tantalum, columbium or uranium.) Reference has been directed by the Comptroller to Specification 961,470. |
