Revealing the Potential of Bimetallic Carbide Catalysts for Upgrading Biomass-Derived Bio-Oil: A First Principles-Based Investigation Using Representative Bio-Oil Constituents

Abstract

Bimetallic carbides, especially based on molybdenum carbide, proved to be a promising hydrodeoxygenation (HDO) catalyst, with enhanced selectivity towards C─O bonds cleavage. However, catalysts are generally investigated using limited model components derived from only one of the biopolymers in biomass (either lignin or carbohydrates), therefore, HDO of raw biomass-derived bio-oil still remains a challenge, as it contains molecules of different functionalities. This paper presents a systematic comparison of the monometallic carbide, Mo₂C, with the novel bimetallic carbide incorporating W using representative bio-oil components of different functionalities and derived from different bio-polymers components of biomass. We employed quantum mechanical investigation to reveal that the W-doped Mo₂C carbide (MoWC) catalyst with increased oxophilicity, owing to tungsten incorporation, can perform HDO of real bio-oil more effectively in comparison to its monometallic counterpart (Mo₂C) using six substrates representing different components of bio-oil. We showed MoWC can selectively cleave both single/double (C─O/C═O) bonds with similar barriers in comparison to Mo₂C which can only selectively cleave single C─O bonds. This observation was consistent for 5-HMF, Acetic acid, and Methyl Glyoxal. We also showed that MoWC outperforms its metallic counterpart Mo₂C in the HDO for aromatic and carbohydrates components.