Author ORCID Identifier

https://orcid.org/0009-0008-2875-3334

Semester

Spring

Date of Graduation

2026

Document Type

Dissertation (Campus Access)

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Debangsu Bhattacharyya

Committee Member

Jianli Hu

Committee Member

Oishi Sanyal

Committee Member

Madelyn Ball

Committee Member

Christina Wildfire

Abstract

Microwave (MW)-assisted catalytic pyrolysis offers a promising pathway for efficient plastic upcycling. This work develops an integrated modeling framework combining dynamic data reconciliation, temperature-dependent rate model, and a yield model to represent the time-varying production rate of components in a MW-assisted LDPE pyrolysis conducted in a batch reactor. An Arrhenius-type rate model with temperature-dependent reaction order is developed. A bi-exponential correlation is proposed for yield of gaseous products that enables to capture evolving product formation behavior during conversion. In the yield correlation, one term is used to represent the initial increase in yield, reflecting the rapid formation of intermediate or primary products at the early stages of reaction when a larger fraction of the reactant remains available. As conversion progresses, the influence of this term gradually diminishes. The other term accounts for the subsequent decrease in the predicted yield, representing secondary reactions such as further cracking or coke formation that reduce the concentration of certain products at higher conversion.  The model is found to accurately represent reconciled experimental flowrate profiles from an in-house MW-assisted catalytic batch reactor for major products, including ethylene, ethane, 1-butene, and benzene, across 250–350 °C. Ethylene remains the dominant product but decreases from about 41.95% at 250 °C to 30.14% at 350 °C, while heavier products increase significantly, with 1-butene rising to nearly 8.37% and benzene reaching 2.17% at intermediate temperatures. The model shows that the ethylene production rate can be maximized at around 270 oC. The models developed in this work can be utilized for process optimization, reactor design and scale-up of microwave-assisted plastic conversion technologies, and economic analysis.

This study presents a comprehensive process modeling and techno-economic analysis of microwave-assisted catalytic pyrolysis of low-density polyethylene (LDPE) for ethylene production and compares its performance with a conventional ethane-propane steam cracking process. A plant-wide model is developed in Aspen Plus, incorporating detailed reactor modeling, downstream separation, and economic evaluation. The MW-assisted process is analyzed at both modular and commercial scales under constant feed-flow and constant product-flow scenarios across multiple operating temperatures. Results indicate that the MW-assisted process offers significant economic advantages over the conventional base case, particularly at the commercial scale, where the minimum selling price (MSP) is reduced from 512.43 $/ton to approximately 321–328 $/ton and the net present value (NPV) is substantially improved. Among the operating conditions, 300°C is identified as the optimal temperature, balancing product yield, capital investment, and operating cost. At the modular scale, the process remains economically competitive, although higher MSP values are observed due to scale limitations. Sensitivity analysis reveals that ethylene price, electricity cost, and catalyst cost are key factors influencing economic performance, with ethylene price having the strongest impact due to its direct effect on revenue. Overall, the findings demonstrate that MW-assisted catalytic pyrolysis is a promising and energy-efficient pathway for plastic waste upcycling to value-added chemicals, offering a viable alternative to conventional steam cracking under favorable economic conditions.

The new in-house experimental data includes benzene as a liquid product accumulated at the end of the experiment. To account for this, dynamic data reconciliation is performed to ensure consistency with carbon and hydrogen balance. Using the reconciled data, parameter estimation is carried out to obtain updated kinetic parameters for the reaction system. The existing fixed-bed reactor model is successively updated with these estimated kinetic parameters to predict the conversion and product yields. In addition, reaction behavior at the particle level is also investigated to provide further insight into the reaction mechanisms. The plant-wide model is then updated in Aspen Plus using a methane feed flow rate of 11,230 kg/h, and the results are compared with the previous study. The techno-economic analysis indicates an increase in the equivalent benzene and ethylene production rates, along with a reduction in coke formation. Despite the improvement in product yields, the specific energy cost ($/kg) is approximately 19% higher than in the previous work. This increase is primarily attributed to inflationary effects and higher utility costs, particularly electricity prices, compared to earlier studies.

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