Liquid- and vapor-phase hydrogenation of 1-epoxy-3-butene using self-assembled monolayer coated palladium and platinum catalysts

Alkanethiol self-assembled monolayers (SAMs) have recently been shown to be effective catalyst modifiers for increasing the selectivity of the hydrogenation of 1-epoxy-3-butene (EpB) to 1-epoxybutane in the gas phase. In the results reported here, we demonstrate that SAM coatings can similarly be applied to other supported metals (Pt) and in liquid-phase reaction environments. Coating a Pt/Al2O3 catalyst with n-octadecanethiol resulted in a large improvement in selectivity during vapor-phase EpB hydrogenation, similar to that observed for supported Pd. The liquid phase hydrogenation of EpB using SAM-coated catalysts showed similar selectivity trends in some cases, but interactions of the solvent with the SAM were also important in controlling selectivity. In particular, using a heptane solvent, epoxybutane selectivity increased from 36% with an uncoated Pd/Al2O3 catalyst to 74% with a thioglycerol SAM-coated catalyst. SAM quality was shown to have a strong impact on the rate of reaction but little effect on selectivity. The results generally indicated that selectivity modification with thiol SAMs is extendable to other supported metals and a variety of reaction environments.

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► Thiol SAM coatings alter selectivity on supported Pt and Pd catalysts.
► Thiol SAMs can be used to enhance liquid phase hydrogenation selectivity.
► Solvent–SAM interactions have a strong effect on selectivity.
► More crystalline SAMs are associated with higher catalyst activity.