Dehydrogenation versus dehydration of aliphatic alcohols on metal oxides

Abstract

Dehydrogenation (—H₂) of propan-2-ol and butan-2-ol to the corresponding ketones and/or their dehydration (—H₂O) to alkenes have been compared over high purity powdered oxides of the fourth row transition metals. Activities of commercially available Al₂O₃, SiO₂ and TiO₂ catalyst supports were also determined. Quartz microcatalytic reactions with gas chromatographic analysis were used in both continuous-flow and pulsed-reactant model to study the dependence of sample activity to (—H₂) and (—H₂O) processes upon the state of oxidation–reduction of the surface, upon temperature and upon preadsorption of selective acidic or basic poisons. Sealed reactors with mass spectrometric analysis were also employed to monitor the growth of hydrogen product and its relationship to other products. Results are considered in the light of various two-electron and one-electron models for the selectivity and activity of metal oxide surfaces.