(4hw) Decomposing Polyurethane Foam with 1D and 2D MFI Type Zeolites: A Catalytic Approach.

The continuous increase in plastic production over recent decades has not been matched by the development of effective recycling technologies for plastic waste. Upcycling plastic waste into new, valuable products offers a promising yet challenging alternative to this issue. In the United States, polyurethane is a significant and widely used plastic, primarily produced through the reaction between isocyanates and polyether polyols. However, the long chains of polyurethane can restrict internal diffusion during upcycling reactions. Thus, achieving high reaction rates typically requires materials with high surface areas and large pore sizes.

This study explores the catalytic upcycling of polyurethane using various low-dimensional MFI zeolites. Initially, polyurethane was reacted with monoethanolamine to convert solid foams into a shorter-chain polymer liquid. The resultant liquid product separated into two phases: a top layer rich in polyols, derived from the polyether polyol component, and a bottom layer of methylene diphenyl amine, a reaction product of monoethanolamine and methylene diphenyl diisocyanate from the polyurethane. These phases were then individually reacted over different zeolites at elevated temperatures to produce valuable chemicals.

Commercial H-ZSM-5 zeolites were first utilized as catalysts in these reactions. The study examined product distribution, polymer-to-catalyst ratios, and reaction temperatures. Subsequently, low-dimensional MFI zeolites with significantly higher surface areas and pore sizes were synthesized and employed as catalysts. The reaction products were analyzed using liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, and nuclear magnetic resonance.

The synthesized catalysts were characterized through ammonia temperature-programmed desorption, nitrogen physisorption, X-ray diffraction, magic-angle spinning nuclear magnetic resonance, and scanning electron microscopy. Additionally, the spent catalysts were examined using thermogravimetric analysis. The study compared the advantages of the synthesized catalysts to those of commercial H-ZSM-5 catalysts.

Catalytic decomposition pathways for the polyurethanes were proposed based on experimental results and literature data. The findings indicate that catalytic upcycling of polyurethane waste can significantly enhance plastic recycling, energy security, waste management, and environmental protection.

Research Interests

My research interests lie in the synthesis of zeolites and their application in environmentally sustainable processes. I am particularly focused on utilizing zeolites for green applications, such as the upcycling of polymers. By developing innovative methods to synthesize these versatile materials, I aim to enhance their efficiency and effectiveness in converting waste polymers into valuable resources. This approach not only addresses the pressing issue of plastic pollution but also contributes to the advancement of sustainable technologies, fostering a circular economy.