THE EFFECTS OF STEAM ON N-BUTANE OXIDATION OVER VPO AS STUDIED IN A RISER REACTOR

The effects of steam, fed to the riser section of a laboratory recircu lating solids reactor, on butane oxidation over a vanadyl pyrophosphat e catalyst are reported. Gas fed to the riser was either butane in ine rt or butane co-fed with oxygen in inert. The catalyst regenerator-ves sel was fluidized with air in all cases. It was observed that steam ad ded to the riser competes for sites required for gas-phase oxygen acti vation, while catalyst lattice oxygen utilization is not affected. The competition for sites with oxygen causes a decrease in butane convers ion and a corresponding increase in selectivity to maleic anhydride. T he improvement in selectivity is more pronounced under anaerobic condi tions, and an explanation for this result is offered. This study demon strates the opportunity offered by a recirculating solids reactor to s tudy various aspects of selective oxidation catalysis independent of t he complicating effects of simultaneous catalyst reduction and oxidati on reactions.