KINETICS OF THE CATALYTIC HYDROGENOLYSIS OF ETHANE OVER NI-SIO2

The rate of hydrogenolysis of ethane over a Ni/SiO2 catalyst, studied over a large range of pressure and of temperature, is shown to be related to the degree of hydrogen coverage θH, by the equation: r = k0Pce -E(1 - θH) with K0 nearly equal to the number of ethane molecules colliding with the Ni surface, E0 = 14 ∓ 1 kcal/mole, Y = -1 ∓ 2 and X = 15 ∓ 2. The rate-limiting step is believed to be the irreversible, dissociative adsorption of ethane on an ensemble of at least 12 adjacent Ni atoms, free from adsorbed hydrogen, resulting in the complete cracking of C2H6: C2H6 + 12Ni → 2 {A figure is presented} Irreversible adsorption of ethane is assumed to compete with the reversible adsorption of hydrogen. This mechanism, which is compared with those proposed earlier, is in good agreement with data on ethane adsorption studied by magnetic methods, and with a study of ethane hydrogenolysis over NiCu/SiO2 catalysts. © 1979.