Maleic anhydride from mixtures of n-butenes and n-butane:: Effective reaction kinetics

The conversion of mixtures of n-butane and n-butenes to maleic anhydride over an industrial vanadium-phosphorus oxide (VPO) catalyst was experimentally investigated. Specifically, the conversion of a synthetic raffinate II mixture was studied. The reaction kinetics were modeled on the basis of a reaction network consisting of eight individual reactions and by using hyperbolic rate equations. Calculations and experimental results are shown for a temperature range from 400 to 450 degrees C and for molar fractions of the synthetic raffinate II in the feed that were varied from 1% to 2%. The kinetic model shows good agreement with the experimental results. The value of the maximum yield of maleic anhydride is insensitive to changes in temperature and hydrocarbon feed fractions and amounts to similar to 48%. Increases in temperature, however, reduce the amount of catalyst required to reach the maximum yield. The conversions of pure 1-butene and pure n-butane lead to maximum yields of similar to 53% and 56%, respectively. The efficiency of a maleic anhydride process will, therefore, strongly depend on the choice of feedstock and, in particular, on the availability of n-butane at the designated production site.