Nanocatalysis in the Fast Pyrolysis of Lignocellulosic Biomass

The recent developments in biomass fast pyrolysis (BFP) have rendered this process one of the most promising candidate technologies for the sustainable valorization of biomass toward fuels and chemicals. The main aim is to be able to improve the properties of pyrolysis oil (bio-oil) via tuning its composition, paying at the same time a relatively small penalty in the overall yield of liquid pyrolysis products. Although progress in reactor design and process optimization can contribute toward this target, the design of new active, selective, and stable catalysts for biomass pyrolysis, or also termed the in situ upgrading of biomass pyrolysis vapors (without any external hydrogen addition as in hydrodeoxygenation) to aliphatic hydrocarbon or aromatic nonoxygenated type of molecules, is equally or even more important. In this chapter, we review the different types of acidic nanoporous catalysts that have been used till now, which comprise mainly of conventional microporous zeolites and hybrid micro/mesoporous zeolitic materials, ordered mesoporous aluminosilicates, and their metal-promoted counterparts. In addition to acidic aluminosilicates, various metal (nano)oxide catalysts with Lewis acidity, basic properties, or (de)hydrogenation functions are also presented. Catalysts’ activity, selectivity, and stability, as well as reaction mechanisms, in biomass fast pyrolysis have been discussed in the light of the different composition, morphology, nanoporous structure, and surface functionality of the various catalysts.