Hydrogenation of olefins. Part 4.—Reaction of n-butenes with hydrogen catalyzed by alumina-supported ruthenium and osmium

Abstract

The ruthenium and osmium-catalyzed hydrogenation and isomerization of but-1-ene, cis- and trans-but-2-ene has been studied in a static system in the temperature range 0–70 °C (Ru) and 60–140 °C (Os). Product distributions, orders of reaction and activation energies for hydrogenation and isomerization have been determined. Under all conditions, ruthenium gives more isomerization than does osmium.

The results are interpreted in terms of a mechanism in which isomerization occurs by loss of a hydrogen atom from adsorbed C₄H₉ to yield adsorbed butene and hydrogen. For hydrogenation, the rate-determining step is the addition of a hydrogen atom to adsorbed C₄H₉ for each butene. For cis-trans isomerization the rate-determining step is the reaction between adsorbed but-2-yl and a hydrogen atom yielding adsorbed but-2-ene and gas-phase hydrogen whilst for double-bond migration the reaction of adsorbed but-1-ene with a hydrogen atom to form adsorbed but-2-yl is rate-determining.