Hydrocracking of polyethylene to high quality liquid fuels over bimetallic catalyst PdAg/HZSM-5

It is well known that the rapid accumulation of plastics poses a serious environmental pollution problem due to their difficulty in naturally decomposition. Hydrocracking provides an opportunity to convert plastics into value-added chemicals. Herein, the zeolite HZSM-5 supported metal bifunctional catalysts were synthesized for the hydrocracking of polyethylene to obtain high quality liquid hydrocarbon products. Benefiting from the strategy of bimetallic alloying, the second metal was designed to rationally regulate the structure of the active component within the catalyst in order to facilitate the conversion of polyolefin plastics into liquid hydrocarbons. It is found that the introduction of the second metal Ag could affect the electron density on Pd surface, which induced better dispersion of the metal particles. In addition, the metal-zeolite interactions as well as intermetallic interactions between these two metals can modulate the electronic state of Pd, thus improving the selectivity of the target products. The optimum Pd_0.5Ag_1.5/HZSM-5 catalyst was found to exhibit the best catalytic performance by tuning the Pd and Ag loading, with the liquid hydrocarbon yield of 69.18 %. The present work provides a reference for the design and synthesis of catalysts to improve the yield of high-value liquid fuels.