Catalytic pyrolysis of corn stalks over nitrogen-doped coal gasification fine slag: tar composition refining and...

The resource utilization of coal gasification fine slag (CGFS) is a key step toward achieving clean and efficient operation of entrained-flow gasification. In this study, three distinct N-doping routes were employed. CGFS was employed as a raw material to prepare a series of nitrogen-doped slag-based catalysts through alkali treatment, steam activation, and nitrogen doping, which were then applied to the catalytic pyrolysis of corn stalks (CS) for the selective production of phenolic compounds. Characterization results revealed that alkali treatment and steam activation optimized the surface chemistry and pore structure, providing catalysts with hierarchical porosity and abundant, accessible surface sites, while nitrogen doping introduced pyridinic N and pyrrolic N active sites. Catalytic pyrolysis experiments demonstrated that NHY-HS exhibited the most pronounced enhancement in phenolic formation, increasing the phenolic yield in tar by approximately 1.35 times compared with direct pyrolysis, while effectively suppressing unstable oxygenated species such as acids and aldehydes. Model compound studies further elucidated the reaction mechanism: nitrogen-derived basic sites promoted cleavage of C-O and C-C bonds and facilitated demethoxylation and decarbonylation, while radical stabilization by the nitrogen-doped carbon framework and the mass-transfer advantages of the hierarchical pore structure jointly suppressed secondary polymerization and coking, enabling highly selective production of phenolic compounds. This study provides a new pathway for the high-value utilization of coal gasification fine slag and offers theoretical guidance for the design and application of biomass pyrolysis catalysts.