Lignin and spent bleaching clay into mono-aromatic hydrocarbons by a cascade dual catalytic pyrolysis system: Critical role of spent bleaching clay

In the present study, a cascade dual catalytic system was used for the co-pyrolysis of lignin with spent bleaching clay (SBC) to efficiently produce mono-aromatic hydrocarbon (MAHs). The cascade dual catalytic system is composed of calcined SBC (CSBC) and HZSM-5. In this system, SBC not only acts as a hydrogen donor and catalyst in the co-pyrolysis process, but is also used as a primary catalyst in the cascade dual catalytic system after recycling the pyrolysis residues. The effects of different influencing factors (i.e., temperature, CSBC-toHZSM-5 ratio, and raw materials-to-catalyst ratio) on the system were explored. It was observed that, when the temperature was 550 C, the CSBC-to-HZSM-5 ratio was 1:1, and when the raw materials-to-catalyst ratio was 1:2, the highest bio-oil yield was 21.35 wt%. The relative MAHs content in bio-oil was 73.34 %, whereas the relative polycyclic aromatic hydrocarbons (PAHs) content was 23.01 %. Meanwhile, the introduction of CSBC inhibited the generation of graphite-like coke as indicated by HZSM-5. This study realizes the full resource utilization of spent bleaching clay and reveals the environmental hazards caused by spent bleaching clay and lignin waste.

Automated summary

To efficiently produce mono-aromatic hydrocarbon (MAHs), a cascade dual catalytic system composed of calcined spent bleaching clay (CSBC) and HZSM-5 was used for co-pyrolysis of lignin with spent bleaching clay (SBC). The effects of temperature, CSBC-to-HZSM-5 ratio, and raw materials-to-catalyst ratio were explored, and the highest bio-oil yield of 21.35 wt% was achieved at a temperature of 550°C, CSBC-to-HZSM-5 ratio of 1:1, and raw materials-to-catalyst ratio of 1:2. The introduction of CSBC inhibited the generation of graphite-like coke by HZSM-5. This study realizes the full resource utilization of SBC and reveals the environmental hazards caused by SBC and lignin waste.