Abstract: The present invention relates to the processing of hydrocarbon-containing feedstreams in the presence of an interstitial metal hydride comprised of at least one chemical element selected from Groups 3-11 (including the lanthanides, atomic numbers 58 to 71), and at least one chemical element selected from Groups 13-15 from the IUPAC Periodic Table of Elements. These interstitial metal hydrides, their catalysts and processes using these interstitial metal hydrides and catalysts of the present invention improve overall hydrogenation, product conversion, as well as sulfur reduction in hydrocarbon feedstreams.