Tuning redox and chemical characteristics of Mo-based catalysts for bioenergy applications – The case of catalysts supported on TiO2 or ZrO2

Abstract A series of MoO 3 -MoS 2 catalysts supported on TiO 2 or ZrO 2 were synthesized and studied. The aim of this work is to understand the main aspects that influence the catalytic performance of Mo-based catalysts in bioenergy applications. We used two sulfidation temperatures for changing the Mo species in both supports. The catalysts were characterized by N 2 physisorption, XRD, SEM, H 2 -TPR, Raman spectroscopy and XPS. We found important changes in the chemical species of Mo, S and O atoms present in the catalytic materials at 200 or 400 °C of sulfidation temperature. The materials were tested in the hydrodeoxygenation (HDO) of palmitic acid as a model compound of fatty acids. We found some structure-activity relationships of these materials. For instance, the promotion of mixtures of Mo 6+ , Mo 5+ and Mo 4+ species increased the catalytic activity for all the materials. MoO 3 /TiO 2 catalyst exhibits higher activity than its counterpart supported on ZrO 2 . However, the sulfidation of these materials resulted in highly active catalysts, specially using ZrO 2 . Oxygen vacancies are formed for the catalysts supported on ZrO 2 upon sulfidation. Molecular models were employed for a better understanding of the interaction between palmitic acid and the catalytic surfaces. We found that a combination of Mo n+ species with S-containing compounds and oxygen vacancies in the catalytic materials is key to develop new highly active catalytic materials for HDO of fatty acids.