Synergy of molecular sieve catalysis and staged nitrogen-rich pyrolysis: a decoupling strategy for temperature-dependent selective enrichment of characteristic nitrogenous compounds from biomass

Addressing the problem of difficulty in achieving highly selective production of nitrogenous compounds in traditional one-step nitrogen-rich pyrolysis due to the complex composition of biomass, the paper developed a synergistic strategy combining molecular sieve catalysis with staged nitrogen-rich pyrolysis. This strategy aims to achieve the directed conversion of cellulose-lignin into specific nitrogenous compounds and their selective enrichment in specific temperature zones. A systematic investigation was conducted on the catalytic effects of microporous (SSZ-13, HZSM-5) and mesoporous (SBA-15, MCM-41) molecular sieves. The results revealed that mesoporous catalysts exhibited excellent enrichment capabilities, owing to their greater pore size and specific surface area. Among these, MCM-41 enabled the proportion of nitrogenous components to reach as high as 83.0%–94.0% at different temperature stages. More importantly, this temperature-staged nitrogen-rich catalytic pyrolysis strategy realized the temperature-dependent enrichment of various nitrogenous products. Pyrroles (59.0%) and pyrazines (73.5%) were primarily enriched between 250–300 °C. Anilines (76.0%) and azoles (56.5%) were produced in the 300–400 °C range, while pyridines (91.4%) and indoles (∼100%) were selectively formed at 400–600 °C. The EPR analysis revealed the formation of additional oxygen vacancies in MCM-41 post-reaction. The overlap of N and O elemental distributions in EDS mapping suggested a potential interaction between NH 3 and the active sites. Reaction pathway analysis further demonstrated that the cooperative role of catalyst pore structure and acidic sites was vital for product selectivity. This research elucidates the structure–activity relationship of product distribution and catalyst, providing theoretical and technical support for the effective targeted synthesis of biomass-derived nitrogenous chemicals.