The reaction of Carbon with Hydrogen at High Pressure

Abstract

A study has been made of the reactions of a number of carbons with hydrogen at pressures up to 40 atm and in the temperature range 650-870 �C. The effect of total pressure and hydrogen partial pressure has been examined and the rate of methane formation for a given carbon can be expressed as ��������������������� rate= kpH2. Values of log k when plotted against 1/T give a straight line and the "apparent" energy of activation is approximately 30 kcal mole-1. The value of the constant k for a given temperature of reaction is dependent on the oxygen content of the carbon which is, in turn, dependent on the temperature of preparation of the carbon. For carbons containing no oxygen the methane rate is zero, The oxygen appears to be associated with at least two types of active centres. One type, considered to have a lactone structure, is responsible for an initial rapid evolution of methane and water and is destroyed during the first few minutes of hydrogenation. The other centre, responsible for the slow steady evolution of methane, appears to be associated with structures such as chromene or benzpyran which activate certain sites on the carbon crystallite. Neither steam nor carbon dioxide will activate the carbon for the formation of methane.