Oxidative dehydrogenation of alkanes over noble metal coated monoliths at very short contact times

The production of ethylene or syngas from ethane in the presence of air or O{dollar}sb2{dollar} has been examined over ceramic foam monoliths coated with Pt, Rh, and Pd at contact times on the order of milliseconds. In a fuel rich regime (C{dollar}sb2{dollar}H{dollar}sb6{dollar}/O{dollar}sb2{dollar} {dollar}>{dollar} 1.5) on Pt we observe selectivities to ethylene up to 70% with conversions above 80%. On Rh, syngas production dominates. Optimum production of ethylene on Pt is obtained by reacting ethane with a mixture of air and O{dollar}sb2{dollar} at a C{dollar}sb2{dollar}H{dollar}sb6{dollar}/O{dollar}sb2{dollar} ratio of {dollar}sim{dollar}1.7 at contact times {dollar}{dollar}95% conversion of C{dollar}sb2{dollar}H{dollar}sb6{dollar}.; A preliminary elementary step model that simulates the ethane oxidation system has been developed. The model accounts for the different rates of the reactions on Pt and Rh metal surfaces. The model makes several simplifying assumptions in this system of twenty-eight reactions including a plug flow reactor, isothermal operation (at the adiabatic reaction temperature), and rapid mass transfer.; The oxidation experiments are expanded to the autothermal production of olefins from propane or n-butane by oxidative dehydrogenation and cracking. Over the Pt catalyst, olefins are the dominant reaction products at high fuel to oxygen ratios. On Rh, primarily syngas is produced under these conditions. On Pt, we observe up to 65% selectivity to olefins at nearly 100% conversion of propane or n-butane with a catalyst contact time of 5 milliseconds.; The oxidative dehydrogenation of isobutane to isobutylene is an integral step in the production of MTBE. Isobutylene can be produced by oxidative dehydrogenation of isobutane over a ceramic foam monolith coated with Pt. At {dollar}sim{dollar}80% conversion of the isobutane, the dominant products are isobutylene and propylene, each with {dollar}sim{dollar}40% selectivity, or a total olefin selectivity of 80%.; This thesis discusses the combination of reaction kinetics, mass transport, and heat transport over catalytic monoliths that makes the non-equilibrium production of valuable intermediate partial oxidation products (syngas or olefins) possible.