The Performance of Catalytic Conversion of ZSM-5 Comodified with Gold and Lanthanum for Increasing Propylene Production

Thermochemical Conversion of Plastic Waste into Fuels, Chemicals, and Value-Added Materials: A Critical Review and Outlooks

Plastic waste is an emerging environmental issue for our society. Critical action to tackle this problem is to upcycle plastic waste as valuable feedstock. Thermochemical conversion of plastic waste has received growing attention. Although thermochemical conversion is promising for handling mixed plastic waste, it typically occurs at high temperatures (300-800 °C). Catalysts can play a critical role in improving the energy efficiency of thermochemical conversion, promoting targeted reactions, and improving product selectivity. This Review aims to summarize the state-of-the-art of catalytic thermochemical conversions of various types of plastic waste. First, general trends and recent development of catalytic thermochemical conversions including pyrolysis, gasification, hydrothermal processes, and chemolysis of plastic waste into fuels, chemicals, and value-added materials were reviewed. Second, the status quo for the commercial implementation of thermochemical conversion of plastic waste was summarized. Finally, the current challenges and future perspectives of catalytic thermochemical conversion of plastic waste including the design of sustainable and robust catalysts were discussed.

Catalytic Cracking for Propylene Production over Au Catalyst Supported by External Surface-Modified ZSM-5 Zeolite

To improve the yield of propylene in fluidized catalytic cracking, a series of different Au/ZSM-5-TOS catalysts were prepared by modifying ZSM-5, using an external surface modification method and Au nanoparticles. The modified catalyst maintained the MFI structure of ZSM-5, whereas the pore-opening size of the zeolite relatively decreased, without affecting its internal structure. The acidity of ZSM-5, especially the Brønsted acidity, reduced. Among the studied catalysts, the 0.2 wt% Au/ZSM-5-1%TOS catalyst exhibited the best feedstock conversion and propylene selectivity, along with a significant increase in propylene selectivity and a slight decrease in the conversion of light diesel oil, even after water vapor treatment at 800 °C for 4 h. Its catalytic activity at 360 °C exceeded that of ZSM-5 at 460 °C, showing great application potential in petrochemical processes.

Understanding the Catalytic Activity of Microporous and Mesoporous Zeolites in Cracking by Experiments and Simulations

Porous zeolite catalysts have been widely used in the industry for the conversion of fuel-range molecules for decades. They have the advantages of higher surface area, better hydrothermal stability, and superior shape selectivity, which make them ideal catalysts for hydrocarbon cracking in the petrochemical industry. However, the catalytic activity and selectivity of zeolites for hydrocarbon cracking are significantly affected by the zeolite topology and composition. The aim of this review is to survey recent investigations on hydrocarbon cracking and secondary reactions in micro- and mesoporous zeolites, with the emphasis on the studies of the effects of different porous environments and active site structures on alkane adsorption and activation at the molecular level. The pros and cons of different computational methods used for zeolite simulations are also discussed in this review.