2024 AIChE Annual Meeting
Impact of Pt Encapsulation and Macroporosity in MFI Zeolite on Catalytic Plastic Upcycling
Conventional methods of plastic recycling (e.g. mechanical recycling) typically require high-purity plastic waste and yield recycled polymers of lower quality. Chemical recycling is a promising supplement to the existing waste-processing repertoire, allowing for the conversion of polyolefin chains into value-added hydrocarbon products (e.g. fuels). Within this area, catalytic cracking has been emerging as a lower-temperature alternative to methods like pyrolysis. Previous work has shown that zeolites, with their high thermal stability and well-defined micropore structure, are particularly suited for such cracking reactions. Ongoing efforts seek to probe the impacts of structural modifications (e.g. hierarchical porosity, loading of noble metal nanoparticles) to the catalyst on relevant catalytic mechanisms. As bulkier feed hydrocarbons (i.e. polyethylene) result in highly mass transfer-limited reaction kinetics, hierarchical porosity is particularly interesting as a strategy to improve transport of hydrocarbon chains into the catalyst framework. Beyond porosity, the incorporation of metal nanoparticles has been shown to significantly impact product selectivity and coke formation, but the nature of this influence is not yet completely understood. Here, we show that introducing a macroporous (> 50 nm) structure to a metal-free, microporous MFI catalyst improves its solid conversion rate. Additionally, we provide insights into the synthesis of metal-encapsulated MFI catalysts, which allows for better understanding of the respective roles of acid and metal sites in bifunctional hydrocracking reactions.