Vapor Phase Catalytic Deoxygenation of Model Pyrolysis Compounds

Abstract

Vapor Phase Catalytic Deoxygenation of Model Pyrolysis Compounds

Catalytic vapor phase upgrading of biomass pyrolysis products has the potential to create a liquid product that is compatible with existing petroleum refining infrastructure or could be used directly as a fuel. In order to improve the economics of upgrading, it would be desirable to develop a catalyst that selectively rejects oxygen from pyrolysis vapors and minimizes coking. During catalytic cracking, there are at least three reactions that may occur to remove oxygen: i) decarboxylation, ii) decarbonylation, and iii) dehydration. To improve understanding of how catalyst composition affects reactivity and selectivity for deoxygenation reactions, a series of Ni, Cu, W, Ni-Cu, and Ni-W catalysts supported on Al₂O₃ were synthesized. Acetic acid was used as a model compound representing a major type of oxygenate found in biomass pyrolysis vapors, carboxylic acids. Several of the catalysts had similar yield for overall CO₂ production, but the Ni-Cu(1:1)/Al₂O₃ catalyst was found to have the highest selectivity for CO₂ formation (>40%).  Additionally, a bimetallic effect was observed when either Cu or W was added to Ni, which resulted in a significantly enhanced decarbonylation pathway. This preliminary study demonstrates that the biomass deoxygenation pathways can be significantly altered using multi-component catalysts to create new reaction behavior and there is the potential to develop new materials that are selective for a desired reaction.