THE CARBON-STEAM REACTION AT ELEVATED PRESSURE - FORMATIONS OF PRODUCT GASES AND HYDROGEN INHIBITIONS

The reaction between carbon and steam was studied at a temperature of 1000-degrees-C, a total pres-sure of 10 bar and various partial pressures of steam and hydrogen. The concentrations and stabilities of the intermediate surface complexes were measured with the aid of temperature-programmed desorption and transient kinetic experiments. Possible homogeneous formations of carbon dioxide and methane were studied separately. Hydrogen inhibition results from an irreversible reaction: C( ) + 1/2H-2 --> C(H), and two reversible reactions: C( ) + H2O half arrow right over half arrow left C(O) + H-2 and C( ) + H-2 half arrow right over half arrow left C(H)2. Carbon monoxide is formed from a C(O) surface complex: C(O) --> CO + C( ) + approximately approximately C( ), where approximately approximately ( ) represents a dangling carbon atom. Carbon dioxide clearly is a consecutive product of carbon monoxide and thus is not formed at the carbon surface. Methane is formed at the carbon surface, but only from dangling carbon atoms approximately approximately C( ): approximately approximately C( ) H-2 under arrow pointing right approximately approximately CH2 H-2 under arrow pointing right CH4 + C( ).