High yields of synthesis gas by millisecond partial oxidation of higher hydrocarbons

Cyclohexane, n-hexane, and isooctane were reacted with air in a Rh-monolith reactor and converted into synthesis gas (H2+CO) in yields exceeding 90%, with >95% conversion of fuels and 100% conversion of oxygen. The best catalyst was an 80 ppi washcoated alumina monolith containing 5 wt% Rh. There was a small effect of catalyst contact time on syngas selectivity and conversions for gas space velocities from 3×105 to 3×106 h−1. Preheating the feed enhances syngas selectivities slightly, but no reactor preheat is necessary provided the fuel remains vaporized. Addition of 25 mol% toluene to isooctane also produces syngas, olefins, and methane with 90% yield, including ∼70% yield to syngas. Partial oxidation of gasoline–air mixtures was attempted but the catalysts were poisoned after several hours, probably by sulfur and/or metals.