Origin of the High Performance of GaZrOx/SAPO-34 Bifunctional OXZEO Catalyst for the Methanol-Mediated CO Hydrogenation to Light Olefins

Abstract

Gallium-based catalysts have recently gained strong interest for (de)hydrogenation reactions. In this work, we evaluated GaZr mixed oxides associated with SAPO-34 for the methanol-mediated syngas conversion to light olefins and confirmed high performance of the mixture. A fundamental approach based on H₂-TPD and in situ DRIFTS techniques were followed to decipher the origin of its high performance and provide insights on the still debated redox mechanism of CO hydrogenation to methanol. A pronounced lability and easy regeneration of OH groups on GaZr oxides were shown to facilitate CO conversion to HCOO* intermediate. Concomitantly, surface reduction under hydrogen leads to formation of oxygen vacancies favoring H₂ dissociation and formation of highly reactive Ga-H hydrides which further readily hydrogenate HCOO* intermediate to CH₃O*. The particular property of GaZr oxides making them an optimal component for OXZEO process is its low activity for olefins hydrogenation combined with high ability to generate methanol intermediate.