Oxidn. of hydrocarbons to anhydrides with vanadium catalyst - contg. tantalum and opt. molybdenum, esp. for conversion of benzene to maleic anhydride

摘要

Prepn. of carboxylic anhydrides by passing a gaseous mixt. of hydrocarbons and air through a bed of catalyst in a reaction tube, the catalyst being obtd. by impregnation of an inert support of low specific surface with a soln. contg. dissolved salts of V and opt. Mo as well as a known activator and 0.01-6 wt. % af Ti based on the wt. of V in the catalyst. The hydrocarbon is pref. benzene and the known activators are Na, K, Li, Ag, Cu, Fe, Ni, Co, Zn, Cd, Ge, Sn, Cr, Sb, Bi, U, W, P and Ti. The oxidn. is pref. conducted at 370-390 degrees C with the concn. of hydrocarbons in the air mixt. below the explosive limit, i.e. 43g/l for benzene. The Tl is pref. introduced into the catalyst as an anhydrous EtOH or MeOH soln. Used esp. for prodn. of maleic anhydride. The addn. of Tl improves the catalytic activity greatly so that the oxidn. temp. is lowered, the degree of conversion is increased and by-prod. formation is lessened. The risk is of explosions is also reduced.