The reaction of methane and deuterium on evaporated nickel catalysts

Abstract

The production of all four deuteromethanes from the reaction of methane and deuterium on evaporated nickel films in the temperature range 206 to 255° C was followed by means of a mass spectrometer. The compound CD 4 was the most abundant product in the initial reaction, and there was other evidence that the adsorption of deuterium was stronger than the adsorption of methane. The surface areas of the films were found by the adsorption of deuterium at 0° C which was instantaneous and the films were shown by electron diffraction to be unorientated. An activation energy of about 11 kcal./mole was required for the adsorption of methane. Two types of reaction were distinguished: the first produced CH 3 D with an energy of activa­tion of 24 kcal./mole and the initial rate varied as P CH 4 P -1 D 2 ; the second having an energy of activation of 32 kcal./mole, a greater entropy of activation and a rate dependent on P CH 4 P -1 D 2 gave the other three compounds CH 2 D 2 , CHD 3 and CD 4 . Mechanisms for these reactions are formulated. The equilibrium constants for the interconversion of the five methanes were determined at 466° C and compared with calculated values.