Insight on product regulation and catalysts deactivation during catalytic fast pyrolysis of lignite over micro/mesoporous catalysts synthesized by ZSM-5 seed

We have created a self-assembly method to synthesize the mesoporous structure (SBA-15 and MCM-48) in micro-ZSM-5 by a seed induced crystallization. The micro/mesoporous MCM-48@Z5 composite display the complement effect of micro/mesopores structure in the aromatic yield and coke deposits during catalytic fast pyrolysis of lignite towards aromatics, compared to SBA-15@Z5. Impressively, the mesoporous MCM-48 from the epitaxial growth of ZSM-5 crystal achieved the high alkyl-substituted aromatics in the upgraded tar. By contrast, the developed mesopores in SBA-15@Z5 composites presented the low content of aromatics owing to insufficient acidity. Moreover, from the analysis of the coke nature and composition deposited on the spent zeolites, it can be found that the coke species possessed the light species ( i.e. , benzene, naphthalene and it’s derivatives) and heavy species ( i.e. , long-chain aliphatics), similarly to the coke species on ZSM-5. The coke growth strongly depends on the polymerization on the surface area during catalytic fast pyrolysis of lignite towards aromatics, despite more mesopores on catalysts.