Hydrogenolysis of hydroxymatairesinol on Y derived catalysts: a computational study

Abstract

Hydrogenolysis of 7-hydroxymatairesinol (HMR) to matairesinol (MAT) occurs on palladium supported acidic catalysts. HMR has three stereochemical centres and naturally exists as a mixture of two diastereoisomers, namely RRR-HMR and SRR-HMR. The latter is significantly more reactive than the former, in the reaction above. In order to elucidate the hydrogenolysis mechanism, simple surface events involving HMR derivatives on aluminated faujasite (H-Y) fragments were simulated by quantum chemical calculations. The metallic function of a Pd/H-Y acidic catalyst was also mimicked by a minimal palladium cluster. Stereochemical evidences pointed already out that water β-elimination on the epimeric centre, leading to an olefinic intermediate, should mainly occur for the adsorbed SRR-HMR stereoisomer. As a consequence, it was hypothesized that this feature could explain the different reactivity of the RRR-HMR and SRR-HMR hydrogenolysis, occurring on metal supported bi-functional zeolite catalysts. The significance of this inference is decreased by the here study. Finally, it is demonstrated that several HMR to MAT reaction paths may coexist and that the metal component of the Pd/H-Y bi-functional catalyst cannot be involved in steps discriminating for the whole reaction rate and selectivity.