Effect of Ni-Fe/CaO-Al2O3 catalysts on products distribution in in-situ and ex-situ catalytic pyrolysis of Chinese herb residue

It is necessary to investigate the differences between in-situ and ex-situ methods of bimetallic supported catalysts for biomass catalytic pyrolysis. In this paper, the Ni–Fe/CaO–Al2O3 catalysts with different Ni/Fe ratios have been synthesized by coprecipitation method, and it was explored that the effect of products distribution about Chinese herb residue(CHR) catalytic pyrolysis by in-situ and ex-situ methods. The results showed that in-situ NiFe-3 group had the highest content of aromatic compounds (59.68%) and the lowest content of aliphatic compounds (17.67%). This was beneficial to the utilization of chemical raw materials extracted from pyrolysis oil. Meanwhile, the CaO in the catalyst effectively reduces the acid content and corrosion of pyrolysis oil. The results showed that higher Ni and CaO content has the synergistic catalytic action in ex-situ catalytic experiments. It could promote water-gas shift reaction, which is conducive to the generation of H2. In-situ catalysis is mainly used for the upgrading of pyrolysis oil, while ex-situ catalysis is mainly used to promote secondary pyrolysis of pyrolysis products and improve the quality of pyrolysis oil. This work provides reference for the difference and high value utilization of biomass pyrolysis by different catalytic methods.