Daniel A. Hickman

Production of Syngas by Direct Catalytic Oxidation of Methane

The reaction between methane and oxygen over platinum and rhodium surfaces in metalcoated ceramic monoliths can be made to produce mostly hydrogen and carbon monoxide (greater than 90% selectivity for both) with almost complete conversion of methane and oxygen at reaction times as short as 10–3 seconds. This process has great promise for conversion of abundant natural gas into liquid products such as methanol and hydrocarbons, which can be easily transported from remote locations. Rhodium was considerably superior to platinum in producing more H2 and less H2O, which can be explained by the known chemistry and kinetics of reactants, intermediates, and products on these surfaces.

Partial Oxidation of CH4, C2H6, and C3H8 on Monoliths at Short Contact Times†

The autothermal production of partial oxidation products including synthesis gas (CO and H2) and C2H4 from CH4, C2H6, and C3H8 in the presence of air or O2 at atmospheric pressure has been examined over monoliths coated with various metals at residence times between 10-4 and 10-2 seconds. Experiments are carried out in an autothermal reactor operating between 800 and 1200°C Rh gives the highest selectivity to syngas; while Pt forms more H2O, Pd forms solid carbon, Ir sinters, and Ni volatilizes. Carbon formation is suppressed under conditions where graphite formation is predicted on some metals, but forms readily on others. Ethylene production is also observed under fuel rich conditions for reactions of C2H6 and C3H8. Pt gives the highest selectivity to C2H4; while Rh and Pd form solid carbon. Causes of selectivity variations and coke formation will be discussed.