Aromatic production from high-density polyethylene over zinc promoted HZSM-5

The nature of Zn species and their roles in catalytic cracking of high-density polyethylene (HDPE) thermal decomposing vapor over Zn-promoted HZSM-5 (Zn/Z5) for aromatics were investigated. The Zn/Z5 zeolites were prepared using ion exchange and impregnation methods followed by H2 reduction. Results indicated that hydrogen reduction of the Zn/Z5 significantly improved the aromatic yield. [ZnOH]+ and bridged Zn2+ species were critical species promoting BTX formation, with the former demonstrating higher activity. Besides, the synergistic effect between the Zn species and Brunsted acid sites on HZSM-5 boosts the aromatic yield. Incorporation of Zn was also found to promote long-chain scission. Among all the Zn/Z5, hydrogen reduced 2 wt% Zn/ Z5 (SAR=25) is most effective in producing BTX, with a maximum yield of BTX (48%) and BTX selectivity (93%); hydrogen reduced 2 wt% Zn/Z5 (SAR=50) produced the highest yield of total aromatics (53%).

Automated summary

The nature and role of Zn species in Zn-promoted HZSM-5 catalyst for catalytic cracking of HDPE thermal decomposing vapor were studied. Hydrogen reduction of Zn/Z5 significantly enhanced the aromatic yield. [ZnOH]+ and bridged Zn2+ species were identified as crucial species promoting BTX formation, with the former showing higher activity. Additionally, the synergy between Zn species and Brunsted acid sites on HZSM-5 increased the aromatic yield. Incorporation of Zn also promoted long-chain scission. Among the Zn/Z5 catalysts, hydrogen reduced 2 wt% Zn/Z5 (SAR=25) exhibited the highest BTX yield (48%) and selectivity (93%), while hydrogen reduced 2 wt% Zn/Z5 (SAR=50) achieved the highest yield of total aromatics (53%).