Assessment of Catalyst Efficiency in Waste Plastic Recycling Processes

Thesis Abstract

The escalating accumulation of waste plastics and their environmental repercussions underscore the urgent need for effective recycling technologies, with catalytic processes offering promising avenues for enhancing plastic depolymerization efficiency. This study aims to assess the efficiency of various catalysts used in waste plastic recycling processes, focusing on their influence on product yield, quality, and process sustainability. Specific objectives include comparing the catalytic performance of waste-derived zeolites, metal oxides, and heteropoly acids; determining the optimal operational parameters for each catalyst type; and evaluating the economic and environmental implications of catalytic recycling techniques. Employing a mixed-methods research design, the study integrates quantitative experimental analysis with qualitative process evaluations. The quantitative component involves laboratory-scale depolymerization experiments conducted on a representative sample of 150 waste plastic feedstocks, encompassing polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP). Catalysts under investigation are characterized and selected based on prior literature and preliminary screening, with process parameters—temperature, pressure, catalyst loading, and reaction time—systematically varied through a factorial experimental design. Data collection instruments include Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), and Thermogravimetric Analysis (TGA) to quantify product composition and yield. Process performance metrics are computed and analyzed using Analysis of Variance (ANOVA) to determine the significance of factors and interactions. The qualitative evaluation involves semi-structured interviews with process operators and environmental impact assessments to gather insights into operational challenges and sustainability considerations. The data are analyzed via thematic analysis aligned with the Technology Acceptance Model (TAM) and Sustainable Process Frameworks, providing contextual understanding of catalyst performance and scalability prospects. Expected key findings anticipate that catalyst type significantly influences depolymerization efficiency, with waste-derived zeolites exhibiting comparable performance to synthetic counterparts while offering cost advantages. Optimal operational conditions are projected at temperatures between 350°C and 450°C with catalyst loadings of 2–5 wt%, yielding maximum monomer recovery rates of up to 85%. The study also expects to establish correlations between catalyst physicochemical properties—such as acidity, surface area, and pore structure—and process output, contributing to the development of a predictive performance model. Additionally, preliminary economic analysis may reveal that catalyst reuse and regeneration substantially improve process sustainability. This research contributes to the growing body of knowledge by providing empirical evidence on the comparative performance of diverse catalysts in plastic depolymerization, elucidating process-structure-performance relationships, and fostering a deeper understanding of the economic and environmental trade-offs associated with catalytic recycling. The findings aim to inform industrial-scale process optimization and guide policy formulation towards sustainable plastic waste management. The study concludes by recommending the adoption of waste-derived catalysts for cost-effective and environmentally benign recycling systems, emphasizing catalyst regeneration technologies and further pilot-scale validation. Future research directions include exploring nano-engineered catalysts and integrating catalytic processes within circular economy frameworks for plastics. Overall, this investigation offers significant insights into enhancing catalytic recycling efficiency, thus advancing sustainable waste valorization and contributing to global efforts in plastic waste mitigation.