In-situ reaction strengthening mechanism of the pyrolysis water and bio-oil during the biomass pyrolysis over CaO and Ni-char dual catalytic system

In this work, the dual catalytic system of CaO and Ni-char catalyst (Ca-Ni dual catalytic system) was constructed to enhance the reforming reaction between pyrolysis water and bio-oil, and the reaction strengthening mechanism was also revealed using isotope tracer technology. The results showed that CaO could adsorb the water vapor released at low temperatures and promote the reforming reaction between water and bio-oil strengthened by the Ni-Char catalyst. The yield of pyrolysis water was heavily declined by the dual catalytic system from 9.3 % to 5.4 %, companying with the decrease of bio-oil yield to 12.4 %, and the content of light oil (substances with a boiling point below 170 °C) in bio-oil increased by 5.4 %. The results of isotope tracer experiments showed that CaO and Ni-char catalysts had a synergistic effect on the limitation of water production and the bio-oil reforming. D2O was captured by CaO and formed D· and ·OD radicals with the effect of Ni-char, which were inserted into the aliphatic side chain rather than the benzene ring of pyrolysis products through reforming reaction. Meanwhile, with the intensification of the reforming reaction, the CO2 content in pyrolysis gas decreased from 48 % to 33 %.