Sustainable Catalysis for Plastics Recycling: A Case Study in Malaysia's PET Industry

Thesis Abstract

Plastic waste management in Malaysia faces challenges of insufficient supply of high-value recycled PET (rPET) due to suboptimal catalytic conversion processes and fragmented collection streams. This study investigates sustainable catalysis-driven recycling as a pathway to enhance PET valorisation within Malaysia’s plastics industry, addressing the gap between feedstock variability and catalytic performance that limits commercial viability. The aim is to develop and validate a catalysis-based framework that optimises chemical recycling of PET into high-purity monomers and oligomers while minimizing energy input and environmental impact. Specific objectives include (1) characterising the feedstock through PET-rich post-consumer stream profiling; (2) screening and optimizing heterogeneous and homogeneous catalysts for glycolysis, methanolysis, and hydrocracking routes; (3) evaluating process intensification strategies to reduce energy and solvent use; (4) assessing cradle-to-gate environmental footprints using life cycle assessment (LCA); and (5) proposing a scalable business model for Malaysian PET recycling clusters. The methodology integrates a mixed-methods research design. A quantitative phase will involve a factorial laboratory screening of at least six catalyst systems (e.g., metal oxides, zeolites, and organocatalysts) with PET feedstocks sourced from five municipal recycling facilities, producing a minimum of 180 reactor runs. Process metrics include monomer yield, selectivity to terephthalic acid (TPA) and ethylene glycol (EG), energy consumption, and catalyst stability over 50-hour continuous operation. Analytical techniques comprise high-performance liquid chromatography (HPLC) for product composition, gas chromatography–mass spectrometry (GC-MS) for trace impurities, Fourier-transform infrared spectroscopy (FTIR) for polymer signals, differential scanning calorimetry (DSC) for polymer transition properties, and X-ray diffraction (XRD) for crystallinity changes. A qualitative component will conduct semi-structured interviews with 15 industry stakeholders (policymakers, recyclers, and catalyst suppliers) to capture barriers and enabling conditions, analysed via thematic analysis guided by the Technology Acceptance Model (TAM) and the Theory of Planned Behavior (TPB). Data will be triangulated to inform a techno-economic-environmental decision framework. Data analysis for the quantitative strand will apply multiple regression and analysis of variance (ANOVA) to determine significant effects of catalyst type, solvent system, and temperature on monomer yields. Kinetic modelling will be used to derive rate constants and activation energies for the most promising catalysts. The environmental assessment will adopt a cradle-to-gate LCA using ISO 14040/14044 standards, comparing baseline mechanical recycling with chemical recycling routes under realistic Malaysian energy profiles. A sensitivity analysis will identify critical inputs impacting the total cradle-to-gate impact. The research will test two hypotheses H1, catalysts with designed acid–base functionality will yield higher TPA/EG monomer purity at lower energy input; H2, process intensification via solvent-free or low-solvent conditions will reduce environmental burden without compromising product quality. Expected findings indicate that tailored heterogeneous catalysts combined with optimized glycolysis/Methanolysis routes can deliver ?85% selectivity to TPA with >95% EG purity under moderate temperatures (180–240°C) and reduced solvent usage by 40–60% relative to conventional routes. Catalyst recyclability and resistance to feedstock impurities are anticipated to be the key determinants of process viability. The LCA is projected to show a net environmental advantage (reduced global warming potential and eutrophication potential) for optimized chemical recycling over mechanical routes when powered by Malaysia’s current energy mix, with notable improvements under projected decarbonisation scenarios. The study contributes to knowledge by offering a validated, catalyst-centric framework for PET chemical recycling in emerging economies, integrating process design with environmental and economic considerations to inform policy and industry practice. The main conclusion is that sustainable catalysis can substantially enhance the value proposition of PET chemical recycling in Malaysia when integrated with feedstock pre-processing, catalyst design for impurity tolerance, and scalable process intensification. Recommendations include targeted investment in modular catalytic plants adjacent to urban collection hubs, development of standards for pure rPET streams, governance for catalyst lifecycle management, and policy incentives to promote adoption of chemical recycling technologies aligned with circular economy goals.