Catalytic co-pyrolysis of lignin and spent bleaching clay via binder-modified HZSM-5: Evolution of coke composition

In this present study, the composite catalysts were synthesized by agglomeration method using HZSM-5 and calcined spent bleaching clay (CSBC) for lignin with spent bleaching clay (SBC) co-pyrolysis vapors upgrading. The coke characteristics were investigated by NH3-TPD, FTIR, N2 adsorption-desorption, XRD, TGA, Raman, and UV-vis. The results showed that the addition of CSBC could convert the graphite-like coke of HZSM-5 into oxygenated coke, which was beneficial to the regeneration of the catalysts. The skeletal structure of the catalysts was not severely broken by the coke, but there were different degrees of deterioration of the pore structure and acidity (mainly strong acids). The composition of soluble coke (coke precursors) was analyzed by FTIR, GC-MS and HPLC. The soluble coke adsorbed on the catalyst was dominated by long-chain alkanes and oxygenated aromatic compounds. These compounds would continuously polymerize on the acidic sites of HZSM-5 to produce graphite-like coke. The modulation of HZSM-5 by CSBC could inhibit this process. This result explained the binder modification to improve the MAHs selectivity and catalyst stability from the side. This study provides a feasible direction for the modification of zeolite catalysts in the future.

Automated summary

In this study, composite catalysts were synthesized using HZSM-5 and calcined spent bleaching clay (CSBC) for upgrading lignin with spent bleaching clay (SBC) co-pyrolysis vapors. The addition of CSBC converted the coke of HZSM-5 into oxygenated coke, benefiting the catalysts regeneration. The pore structure and acidity of the catalysts were affected by the coke, and soluble coke on the catalyst was mainly composed of long-chain alkanes and oxygenated aromatic compounds. The modulation of HZSM-5 by CSBC inhibited the polymerization of these compounds, improving the selectivity and stability of the catalyst.