(95b) Conversion of Waste Plastics to Liquid Fuels over Bi-Functional Hierarchical Zeolites

Conventional methods of waste plastic management such as landfilling and incineration lead to many environmental hazards. Chemical recycling methods are therefore becoming popular all over the world. Among the chemical recycling methods are the cracking and hydrocracking processes that convert waste plastics into liquid fuels of high quality. In the present work, cracking of model municipal waste plastic mixtures is studied in the presence of hydrogen and both cracking and hydrocracking hierarchical zeolite catalysts. Top-down approach was used to produce mesopores in the microporous USY, ZSM-5, and beta zeolites. The impregnation of Pt and other metals was carried out by wet impregnation method and the synthesized catalysts were well characterized using SEM, TEM, XRD, EDX, N₂-BET, FTIR, and py-FTIR techniques. Hydrocracking experiments with the model plastic mixture were conducted in a high-pressure autoclave reactor and in the temperature range of 350‒425°C. The products of the reactions were analyzed for the conversion and the yields of gas, oil (n-heptane soluble portion of the liquid), and total liquid. The oil produced was additionally analyzed with GC-FID and FTIR analyses. On the basis of conversion and selectivity towards liquid enriched with gasoline, the hierarchical catalysts of zeolite ZSM-5 and zeolite beta performed remarkably well in the hydroconversion experiments. The impregnated Pt-beta composite catalyst delivered 90.1wt% conversion and 68.6wt% liquid yield with gasoline content of 65.8wt%. Kinetics of the hydrocracking reaction over composite ZSM-5 catalyst was also studied. The activation energy for the hydrocracking reaction is found to be 236.8 kJ/mol.