Partial oxidation of methane to syngas at high space velocities over Rh-coated spheres

The effect of space velocity on the partial oxidation of methane using different support geometries has been studied. While on a foam alumina monolith syngas selectivity drops as space velocity is increased above 4 x 10(5) h(-1), the use of non-porous alumina spheres as the support allows high reactant conversions and syngas selectivities even at space velocities of 1.8 x 10(6) h(-1). The differences between monoliths and spheres are discussed in order to understand why spheres give superior results. It is suggested that differences in heat transfer within the two support geometries may play a major role in the different results between spheres and monoliths. A convective heat transfer model suggests that higher rates of convection in a monolith will lead to lower front temperatures than in a sphere bed, a trend that becomes important at high space velocities in leading to blowout and lower syngas selectivities. (C) 2001 Elsevier Science B.V. All rights reserved.