Preparation and application of lanthanum-cobalt bimetallic modified composite ZSM-5/MCM-41 zeolite: Enhancing the stability of aromatic compounds produced by lignin cracking in catalytic pyrolysis of pine sawdust

Bimetallic modified (lanthanum and cobalt) micro-mesoporous composite ZSM-5/MCM-41 zeolite was prepared by recrystallization and impregnation to improve the aromatic compound yield during in-situ catalytic pyrolysis of pine sawdust. Monometallic modified catalysts were prepared for comparison. Catalytic pyrolysis was conducted in a fixed bed reactor at 550 °C for 15 min. The structure-function relationship of the catalysts was studied based on SEM, TEM, BET, XRD, XPS, H2-TPR, NH3-TPD, and Py-IR. The results showed that under the premise of ensuring the bio-oil yield, the catalyst simultaneously doped with lanthanum (16 wt%, La2O3) and cobalt (4 wt%, Co3O4) had the highest aromatic compound yield (79.92%), which was 23.79% higher than that of non-catalytic pyrolysis. In addition, the adjustment of pore structure and acid sites caused by modification and the interaction between doped metal atoms enhanced the aromatic compound stability during pyrolysis, thus leading to a high yield of phenols from lignin cracking.