GAS-PHASE OXIDIZATION PROCESS AND PROCESS FOR THE PREPARATION OF PHTHALIC ANHYDRIDE

摘要

A gas-phase oxidization process which comprises passing a gaseous feed mixture comprising a gas containing molecular oxygen and an optionally substituted hydrocarbon through a fixed-bed catalyst layer to oxidize the hydrocarbon, wherein the porosity of the catalyst layer increases gradually along at least one stage when the mixture flows down from the upstream side. This process enables high-yield and high-productivity gas-phase oxidization of various hydrocarbons such as naphthalene, xylene, benzene, toluene, durene, butene, acenaphthene, anthracene and indene and substituted derivatives thereof. Further, the process can give phthalic anhydride through gas-phase oxidization of naphthalene or xylene in a high yield and at high productivity.