The Catalytic Pyrolysis Performance of Waste Plastics Enhanced by Different Modified Zeolite Molecular Sieves

The catalytic pyrolysis of waste plastics into valuable products is a promising approach for waste management and resource recovery. This study investigated the impact of different modified zeolite molecular sieves (HZSM-5 and USY) on the catalytic pyrolysis performance of low-density polyethylene (LDPE). The zeolites were modified using alkali treatment, alkali-acid combined treatment, citric acid treatment, and EDTA-2Na treatment to manipulate their pore structure and acidity. The modified zeolites were evaluated based on their catalytic activity, product selectivity, and pyrolysis oil characteristics. The results indicated that the modified USY zeolites (S-USY and E-USY) exhibited superior catalytic performance compared to HZSM-5 zeolites, with higher conversion rates and bio-oil yields. The S-USY zeolite, in particular, demonstrated the highest bio-oil yield of over 64% at a pyrolysis temperature of 380°C and a catalyst-to-raw material ratio of 1:2. The pyrolysis oil produced using S-USY as a catalyst contained a high proportion of alkanes, with a lower C/H ratio and higher calorific value compared to HZSM-5 catalysts. The study also explored the effects of catalyst dosage and pyrolysis temperature on the product distribution and characteristics. Overall, the findings highlight the potential of modified USY zeolites for enhancing the catalytic pyrolysis of LDPE and producing high-quality pyrolysis oil with improved resource utilization.