The interaction of hydrogen with micro-crystalline charcoal II—activated sorption of hydrogen and methane by carbon

At high temperatures the reaction between hydrogen and charcoal is not simple. The work of Kingman, and Burstein and Frumkin suggests that the process is one of activated adsorption. Burstein, Lewin and Petroff regard the process as one involving activated diffusion of atoms from reaction centres. Burstein, Frumkin and Fedotov, in conformity with this idea, considered the sorbed hydrogen atoms as capable of being in equilibrium with protons, which can exchange with cations in solution. On the other hand if activated adsorption were a process of surface hydrogenation the C—H units should not behave in this manner. Broome and Travers suggest the formation of methane, and in fact Randall reported a non-condensible gas which was not hydrogen, on desorption of chemisorbed hydrogen. Kingman (loc. cit.) on the other hand found the gas desorbed at 950° C to be pure hydrogen. On account of the fundamental importance of the hydrogen-carbon and methane-carbon systems in hydrogenation, it seemed desirable to reinvestigate these systems and to obtain quantitative data on energies of activation and heats of reaction. Measurements of the rates of sorption and the amounts of gas taken up, when equilibrium was established with the various charcoals, were conducted in a manner similar to that previously described in low temperature physical adsorption experiments. The process of adsorption was again found to be one involving time; at sufficiently elevated temperatures isothermals could be determined by approach from both sides of the equilibrium pressure.