Overview of catalytic upgrading of biomass pyrolysis vapors toward the production of fuels and high‐value chemicals.

The application of heterogeneous catalysis in biomass pyrolysis is considered as one of the most promising methods to improve bio‐oil quality by minimizing its undesirable properties (high viscosity, corrosivity, instability, etc.) and producing renewable fuels and high‐value chemicals. Catalytic fast pyrolysis (CFP) of biomass refers both to the "in situ" and "ex situ or two‐stage" upgrading. A plethora of catalytic materials have been investigated in the literature for both approaches, including conventional microporous zeolites, ordered mesoporous aluminosilicates, promoted or not with several transition metals, as well as various metal (nano)oxide catalysts with Lewis acidity. Recently, hybrid micro/mesoporous and basic materials have been also suggested exhibiting most promising results due to combined micro/mesoporosity and adequate balance of acid and basic sites. Optimum catalysts are required to retain deoxygenation, enhance yields of aromatics, and other valuable compounds (such as phenolics), while limiting coke formation. Coke formation is one of the reasons of catalyst deactivation; a very challenging issue during biomass CFP, especially using zeolites. The deactivation process is affected by many factors, including the composition of the feedstock (inorganic minerals present in the feedstock may also deposit on the catalyst), reaction conditions, and the nature/properties of the catalysts used in CFP. Precoking on the surface of zeolites or MgO deposition are among the proposed effective ways to suppress coke formation and thus, catalyst deactivation. This article is categorized under: Bioenergy > Science and MaterialsEnergy Research & Innovation > Science and MaterialsEnergy and Transport > Science and Materials Schematic description of the "in situ" and "ex situ" upgrading of pyrolysis vapours and catalyst deactivation due to either coke formation or deposition of biomass ash. [ABSTRACT FROM AUTHOR]