Catalytic mechanism of N-containing biochar on volatile-biochar interaction for the same origin pyrolysis.

Nitrogen, as a common element, is widely present in biomass. The effects of nitrogenous substances on the same origin pyrolysis of biomass and the consequences of N-containing biochar on the catalytic process of volatiles are important for further analyzing the pyrolysis mechanism of biomass. In this research, N-containing biochar was prepared under different conditions, and the interaction between N-containing biochar and biomass pyrolysis volatiles at 400-700 °C was studied. The results show that N-containing biochar can simultaneously participate in reactions as adsorbents, catalysts, and reactants. Its catalytic effect is obviously different for various N configurations. Pyridinic N and pyrrolic N can promote the cracking of lignin into methoxy phenol compounds and promote the further cracking of 5-hydroxymethylfurfural. Graphitic N and oxidized N can promote the further decomposition of phenol and the conversion of D-xylose into small-molecule ketones. In addition, oxidized N can also inhibit the cracking of lignin to produce guaiacol. In the long-term interaction, the highly active pyridinic N tends to convert to a more stable graphitic N.