Date on Master's Thesis/Doctoral Dissertation

5-2022

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemical Engineering

Degree Program

Chemical Engineering, PhD

Committee Chair

Sathitsukanoh, Noppadon

Committee Co-Chair (if applicable)

Willing, Gerold

Committee Member

Willing, Gerold

Committee Member

Jaeger, Vance

Committee Member

Thompson, Lee

Author's Keywords

solid acids; catalysts; zeolites; metal-organic frameworks; lignocellulose upcycling; plastic upcycling

Abstract

My goal is to develop chemical processes for transforming waste to solve environmental problems and enhance sustainability. Environmental problems such as pollution and massive amounts of waste are the main drivers that stimulate my research ideas. I focused on creating novel, efficient catalytic processes for converting polymeric waste "feedstocks" into high-value chemicals by integrating my expertise in catalysis, materials science, and synthetic chemistry to develop porous solid catalytic materials. During my Ph.D., I focused on two polymeric feedstocks, lignocellulose, and discarded plastic.

Early in my Ph.D. journey, I focused on catalytic upcycling of lignocellulose. Lignocellulosic biomass is cost-effective, abundant, and renewable. Upcycling lignocellulose into renewable fuels and chemicals has the potential to reduce reliance on fossil fuels, mitigate global warming, and promote a sustainable bioeconomy. The major challenge in upcycling lignocellulose is the active, selective, and reusable catalysts. I developed porous solid acid catalysts by solvothermal techniques and tuned their catalytic performance through surface modifications to upcycle these lignocellulose samples.

Later part of my Ph.D. tenure, I continued to use my understanding of lignocellulose polymer and catalysis to upcycle synthetic polymers (discarded plastic). Global plastic production creates more than 400 million metric tons of plastic per year. Polyolefins account for >60% of global plastic consumption. Unfortunately, most plastics are discarded in landfills, and they pollute waterways and food chains, negatively affecting human health and the environment. In addition, most plastics are inert and designed to last a lifetime. As a result, discarded plastic ends up in landfills, pollutes waterways, and negatively affects the environment and health. The ability to upcycle plastic will mitigate plastic pollution and support a circular economy, thereby providing a financial incentive for industries to upcycle plastics instead of sending them to landfills.

I divided this dissertation into nine chapters to provide a guide in designing catalytic systems for upcycling lignocellulose and discarded plastic. Chapter One gives the background on lignocellulose and plastic and catalysis. I briefly discussed the aim and scope of this dissertation. Chapter Two explores the surface modification techniques of zeolites by organic surfactants and applies them for efficient glycerol conversion to solketal. Chapters Three, Four, Five, and Six discuss how tuning properties and structural modification of MOFs enhanced the acidity and catalytic performance. Chapter Seven combines experimental results and computational study to elucidate how Hf- and Zr-containing MOFs activate biomass-derived carbonyl compounds during transfer hydrogenation reaction.

Chapters Eight and Nine detail upcycling approaches for plastic Brønsted acid sites. Chapter Eight shows the development of the novel solid Brønsted acidic catalysts by sulfonating polypropylene for esterification of lignocellulose-derived levulinic acid. This work allowed me to translate my knowledge in lignocellulose conversion to plastic upcycling. Chapter Nine explores the use of plastic-derived Brønsted acidic catalysts for the conversion of different biomass-derived compounds and elucidates the reaction pathways for efficient conversion. Overall, the development of porous solid acid catalysts for lignocellulose and plastic upcycling will provide promising solutions to transition our society toward a circular economy.

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