Review of Reactor and Catalyst in the Pyrolysis of Biomass for Liquid Fuels

Abstract

Due to the rapid growth of energy consumption, fossil-based fuel is at the verge of extinction. Hence, the world needs new energy to substitute for the non-renewable energy resources. Various biomass resources have been discussed by virtue of the ability of generating alternative fuels, chemicals and energy-related products. To date, the utilization of biomass is mainly thermochemical conversion which involves combustion, gasification and pyrolysis. The focus, currently, is on the catalytic pyrolysis of biomass. A variety of reactors are designed and many new catalysts for the yields of liquid products and upgrading of bio-oil are investigated. Different reactors have their own unique characteristics, and fixed bed reactor is not complicated and can be controlled easily but is difficult to upsize. Fluidized bed has a good suitability for different kinds of biomass but is more complex in structure and more difficult to control. Compared with non-catalytic pyrolysis, the quality of bio-oil improves considerably in the presence of a catalyst. Different catalysts exert different effects on the upgrading of bio-oil. HZSM-5 can reduce a vast output of acid compounds and increases hydrocarbon yields. Au/Al2O3 catalyst leads to an increase of H2 yield. All the catalysts can promote the upgrading of pyrolysis products. Optimal yields and the best quality of bio-oil can be obtained by an appropriate reactor with a proper catalyst.