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 diff erent 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 react ant 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 tha t differences in heat transfer within the two support geometries may play a major role in the different results between spheres and monoliths. A conve ctive heat transfer model suggests that higher rates of convection in a mon olith will lead to lower front temperatures than in a sphere bed, a trend t hat becomes important at high space velocities in leading to blowout and lo wer syngas selectivities. (C) 2001 Elsevier Science B.V. All rights reserve d.