Advanced Catalytic Conversion of Waste Plastics into Value-Added Petrochemical Feedstocks Using Heterogeneous ZSM-5 Based Catalysts

Project Abstract

This study presents a comprehensive investigation into the catalytic conversion of municipal and industrial waste plastics into valuable petrochemical feedstocks using heterogeneous ZSM-5 based catalysts, aiming to address plastic waste accumulation while enhancing the sustainability of petrochemical supply chains. A dual-faceted catalytic approach is employed (i) catalytic pyrolysis and (ii) catalytic hydrocracking, operated under optimized temperature, pressure, and residence time regimes to maximize liquid hydrocarbon yields within the gasoline and light diesel range, and to minimize the formation of undesired gases and heavy tars. ZSM-5 zeolites, modified with acidic sites and hierarchical porosity through templating and post-synthesis dealumination, are combined with metal promoters (e.g., Fe, Ni) and sapolysation strategies to tune acidity, shape selectivity, and coke resistance. The catalysts' physicochemical properties are characterized by BET surface area, XRD, SEM-EDS, TEM, NH3-TPD, Py-IR, and TGA to correlate structure–activity relationships with product distributions. Feedstocks include low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and mixed plastic scraps, pretreated to remove contaminants and facilitate consistent reaction behavior. Reaction experiments are conducted in a fixed-bed reactor under inert atmosphere for pyrolysis and in a continuous-flow reactor for hydrocracking, with in-situ real-time online GC-FID and GC-MS analysis to monitor product evolution. A two-tier modeling framework is implemented (i) kinetic modeling to capture primary decomposition pathways and secondary cracking, and (ii) process optimization using response surface methodology (RSM) and genetic algorithms to identify operating windows that maximize desirable C5–C12 olefins and aromatics while minimizing coke formation and polyaromatic hydrocarbons. Life cycle assessment (LCA) is integrated to quantify environmental benefits, including reductions in greenhouse gas emissions, fossil feedstock dependence, and plastic leakage, alongside sensitivity analyses to evaluate the influence of feedstock variability and catalyst lifetime. The study investigates catalyst stability under coking conditions, regeneration strategies via mild oxidative treatments, and the effect of metal loading and zeolite framework topology on selectivity toward benzene, toluene, xylene (BTX) precursors and light olefins. Preliminary results indicate that hierarchical ZSM-5 with optimized Si/Al ratios and balanced Brønsted/Lewis acidity achieves superior feed conversion with elevated BTX synergies and reduced heavy-cycle oil formation. In-depth product characterization reveals a favorable distribution of high-value fuels and petrochemical feedstocks, with potential co-production of valuable aromatics compatible with refinery integration. The findings offer scalable pathways for converting plastic waste streams into commercially relevant petrochemical intermediates, contributing to circular economy objectives, waste valorization, and sustainable materials management. The work also identifies critical gaps in catalyst longevity and feedstock preprocessing, proposing targeted improvements in catalyst design, regeneration protocols, and process control to optimize industrial viability.

Project Overview

What This Project Is About

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A simple, beginner-friendly look at turning plastic waste into useful petrochemical building blocks using a special helper material called a zeolite catalyst (ZSM-5). The project explores how plastics can be broken down into smaller, valuable chemicals that are used to make plastics, fuels, and other products, using a solid catalyst that can be reused.

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The Problem It Addresses

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Plastic waste is growing and much of it ends up in landfills or the environment. Traditional recycling methods often struggle with mixed plastics and low-value outputs. This project seeks a cleaner way to convert waste plastics into higher-value chemical feedstocks, reducing waste and expanding sustainable options.

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Objectives of the Project

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1. Understand how plastics can be broken down into smaller useful molecules.
2. Explain what ZSM-5 catalyst is and why it helps in breaking down plastics.
3. Demonstrate a simple, scalable process to convert plastic waste to petrochemical feedstocks.
4. Assess the performance of the catalyst in terms of product yield and quality.
5. Identify the main factors that affect the efficiency and selectivity of the reaction.

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What You Will Do Step by Step

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1) Review basic concepts about plastics, catalysis, and ZSM-5 materials. 2) Design a small experimental setup to test plastic conversion with a solid catalyst. 3) Run experiments with different plastic types and catalyst conditions. 4) Collect data on outputs, such as fuel-range liquids or light hydrocarbons. 5) Analyze results to see which conditions work best. 6) Compare products to common petrochemical feedstocks. 7) Discuss practical challenges and safety considerations. 8) Summarize findings and suggest improvements for future work.

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Expected Outcome

Clear demonstration that waste plastics can be converted into useful chemical feedstocks using a ZSM-5 catalyst, with data showing which plastics and conditions give the best results. The project should identify practical limits, safety notes, and potential for scaling up to a real-world process.