High productivity process for the production of maleic anhydride

Abstract

An improved process for the manufacture of maleic anhydride by catalytic oxidation of a nonaromatic hydrocarbon having at least four carbon atoms in a straight chain, in which a gas containing oxygen and hydrocarbon is passed through a fixed catalyst bed in a tubular reactor. The activity of the catalyst bed is graded in such manner that the reactor can be operated at an initial (feed gas) hydrocarbon concentration of over 1.5% by volume, an integrated average temperature difference between gas and cooling fluid of at least about 15.degree. C. over that portion of the bed in which the gas temperature exceeds the cooling fluid temperature, and a productivity of at least about 5.0 lbs. maleic anhydride per hour, without the temperature difference between the gas and the cooling fluid exceeding 80.degree. C. at any point in the catalyst bed during the course of the reaction. Preferably, the catalyst activity and the gas permeability of the bed vary in the direction of gas flow so that both the catalyst activity and the pressure drop per unit distance are lower in a critical region, where the combination of temperature and hydrocarbon concentration could otherwise cause the reaction to proceed at an excessive rate, than they are in a region of low temperature and low hydrocarbon concentration. Significant and unexpected improvement in reactor performance is achieved by the combination of a graded catalyst charge and incorporation of a catalyst modifying organophosphorus compound in the hydrocarbon feed.