Promoting hydrogenation without side reactions over Pd nanoparticles uniformly dispersed in MFI zeolite

Zeolites have been widely applied as support materials for metal nanoparticles. However, when developing a metal/zeolite catalyst for hydrogenation reactions, the Brønsted acid sites of zeolites can promote side reactions and the zeolite structure can inhibit the access of reactants to the metal, resulting in low activity and selectivity. In this study, these challenges are addressed by preparing a metal/zeolite catalyst via a modified ion-exchange followed by reduction method, and subjecting the catalysts to two test reactions, hydrogenation of vanillin and fatty acid methyl esters (FAMEs). After forming Pd nanoparticles within ZSM-5, it was treated with a NaOH solution in a controlled manner to form mesopores around Pd and replace hydronium ions with sodium ions to remove Brønsted acid sites. Pd/ZSM-5 catalysts prepared with controlled NaOH treatment showed higher hydrogenation reactivity and improved selectivity toward the desired hydrogenation products than those prepared without NaOH treatment. This study presents a simple strategy to prepare metal/zeolite catalysts to promote hydrogenation without side reactions.