An unexpected phenomenon in heterogeneous catalysis: oxidative addition of hydrogen to the sulfide catalysts

Abstract

The paper summarizes experimental and theoretical evidence of an oxidative addition of hydrogen to the active metal (Ni or Co) in the active component of the sulfide HDS catalysts—a new phenomenon unknown to date in heterogeneous catalysis. Several aspects are discussed: thermodynamics of the oxidative addition of hydrogen; possible mechanism of dihydrogen activation by sulfide catalysts; electronic state of the active metals Ni(IV) and Co(III) with d 6-electron configuration; reversibility of the oxidative addition and reductive elimination of hydrogen at high temperature; sites of hydrogen localization inside the active component matrix; spectroscopic evidence on the existence of “occluded” hydrogen; a strong interaction of the occluded hydrogen with the active component matrix; a new version of the catalytic cycle of thiophene hydrogenolysis.