Assessment of Catalyst Efficiency in Waste Plastic Pyrolysis Processes

Thesis Abstract

The escalating accumulation of plastic waste presents a significant environmental challenge, necessitating the development of sustainable recycling methods such as waste plastic pyrolysis. Despite its potential to convert plastic waste into valuable hydrocarbon fuels, the efficiency of the process remains inconsistent, primarily due to variations in catalyst performance. This study aims to systematically assess the efficiency of different catalysts in waste plastic pyrolysis and elucidate their influence on product yield, quality, and process sustainability. The specific objectives include evaluating the catalytic activity of zeolite-supported catalysts versus metal oxide catalysts, determining optimal operational conditions for maximum liquid fuel yield, and analyzing the environmental and economic implications of various catalyst applications. A mixed-methods research approach was employed, integrating quantitative experimental procedures with qualitative assessments. The quantitative phase involved experimental pyrolysis of post-consumer polyethylene and polypropylene waste samples collected from local recycling centers, with a sample size of 100 plastic waste batches. Catalysts tested included zeolite-supported HZSM-5, alumina-supported nickel, and untreated controls. Reactor conditions were systematically varied across temperature ranges (450°C to 600°C), catalyst-to-plastic ratios (110 to 13), and residence times (30 to 90 minutes). Data was collected through gas chromatography-mass spectrometry (GC-MS) for product composition, thermogravimetric analysis (TGA) for catalytic activity, and Fourier-transform infrared spectroscopy (FTIR) for chemical interactions. Additionally, process performance metrics, such as conversion efficiency and liquid fuel yield, were recorded. Qualitative data from expert interviews provided contextual insights on operational challenges and environmental considerations. Data analysis utilized analysis of variance (ANOVA) to compare catalyst effectiveness across different parameters, complemented by regression analysis to model relationships between operational variables and product outputs. Kinetic models were developed based on Arrhenius equations to understand catalyst activity profiles, while thematic analysis of qualitative data elucidated stakeholder perspectives on process sustainability. The study further employed the Theory of Planned Behavior to predict adoption pathways of different catalytic processes within industrial settings. It is anticipated that zeolite-supported HZSM-5 catalysts will demonstrate superior cracking activity, resulting in higher liquid fuel yields with comparable thermodynamic profiles, whereas metal oxide catalysts may exhibit enhanced selectivity for specific hydrocarbon fractions. Furthermore, optimal process conditions are expected to be identified at a temperature of approximately 550°C, catalyst-to-plastic ratio of 15, and residence time of 60 minutes, balancing efficiency with environmental safety. The findings are projected to contribute novel insights into catalyst optimization strategies, facilitating the development of cost-effective and environmentally sustainable pyrolysis processes. The research is expected to demonstrate that catalyst selection significantly impacts product quality, process efficiency, and environmental footprint, informing best practices for scaling up waste plastic valorization technologies. The study concludes that tailored catalyst formulations and operational parameters can markedly improve pyrolysis outcomes, contributing to circular economy initiatives by promoting waste reduction and resource recovery. Recommendations include further exploration of nanostructured catalysts, integration of catalytic pyrolysis into existing waste management systems, and policy frameworks to incentivize sustainable plastic recycling. The research ultimately advances the scientific understanding of catalytic processes in plastic waste valorization, providing a robust empirical foundation for industrial adoption and future innovation in sustainable waste management practices.