Selective Deoxygenation of Biomass-Derived Bio-oils within Hydrogen-Modest Environments: A Review and New Insights

Research development of processes for refining bio-oils is becoming increasingly popular. One issue that these processes possess is their high requirement for H2 gas. In response, researchers must develop catalysts that perform deoxygenation while minimizing H2 consumption—selective deoxygenation. Unlike traditional deoxygenation processes, selective deoxygenation reactions and catalysts represent an information gap that, prior to this publication, has yet to be reviewed. This review addresses the gap by providing both a summary of recent research developments and insight into future developments of new catalytic materials. Bifunctional catalysts containing a combination of oxophilicity and an active metal phase appear to be the most beneficial for selective deoxygenation processes in a H2-modest environment. It is important that catalysts have a supply of disassociated hydrogen, because without such, activity and stability will suffer. The authors recommend to maximize the use of internally available hydrogen in bio-fuel, which may be the only viable approach for deoxygenation if external H2 gas is limited. This would be possible through the development of catalysts that promote both the water–gas-shift and deoxygenation reactions.