Products Distribution During In-Situ and Ex-Situ Catalytic Fast Pyrolysis of Chinese Herb Residues

Abstract Catalytic fast pyrolysis (CFP) for biomass treatment is a research hotspot but there is little information about the difference between the in-situ and ex-situ methods. In present work, the Ni-Fe/CaO-Al2O3 catalysts with different Ni/Fe ratios have been synthesized by coprecipitation method, and the products distribution about the Chinese herb residues (CHR) catalytic fast pyrolysis in in-situ and ex-situ methods have been investigated. The results shown that CFP pyrolysis would upgrading the quality of bio-oil but decrease the yields, no matter in-situ or ex-situ CFP process. During the in-situ CFP process, heteroatoms may be absorbed by the catalyst support and cannot be transferred to the bio-oil, but the results of ex-situ CFP is the opposite. In addition, ex-situ CFP reaction significantly increases the content of aromatic hydrocarbons. As to the gas products distribution, the effect of Fe in catalysts to promote CH4 formation is reflected in in-situ CFP process, while the promotion effect of H2 generation for Ni added in catalyst is mainly reflected in ex-situ CFP process. However, due to the high reaction temperature (800°C), the adsorption of CO2 by CaO support is not particular significant. The possible mechanism of CHR in CFP process have also be summarized for understanding the process of in-situ and ex-situ CFP, and this study may provide a choice or reference for CHR treatment.