The integrated process for hydrogen production from biomass: Study on the catalytic conversion behavior of pyrolytic vapor in gas–solid simultaneous gasification process

• Biochar enhanced catalytic conversion of biomass pyrolytic vapor (MPV).
• The catalytic conversion of MPV was promoted by the metallic elements in biochar.
• The alkali and alkaline earth metals played dominating catalytic roles.
• Increasing temperature and S/MPV promoted hydrogen production.

The gas–solid simultaneous conversion in the integrated process means the biomass pyrolysis products, pyrolytic vapor and biochar, can be comprehensively converted for hydrogen production from biomass in the presence of steam. In order to study the catalytic conversion behavior of biomass pyrolytic vapor in this gasification process, the influence of bio-char on the conversion of model pyrolytic vapor (MPV) was investigated in a fixed bed reactor. The results showed that biochar enhanced the conversion of MPV, resulting in the increase of carbon conversion and potential hydrogen yield from 68.46% to 86.88% and 42.16% to 82.76% respectively. The catalytic activities of different metal elements in biochar were found with the following sequence: K > Ca > Mg > Fe > Zn > Al. Meanwhile, the alkali and alkaline earth metals (AAEM) like K, Ca, and Mg were found to play the dominating roles in the conversion of MPV, and especially, the catalytic effect of K was the most obvious among the metals in bio-char. Finally, the effects of temperature (750–900 °C) and steam to MPV ratio (2–5 g/g) on the catalytic conversion of MPV in the presence of biochar were investigated. The carbon conversion and potential hydrogen yield of model pyrolytic vapor were improved by increasing temperature and steam to MPV ratio (S/MPV).