(2jw) Upcycling of Plastic Waste into Value-Added Chemicals through Oxidation and Hydrogenation Reactions

Plastics have become essential in contemporary society due to their affordability, remarkable chemical stability, and versatile physical properties that can be tailored to suit specific applications. These properties have contributed to the exponential rise in global production of plastic resins, films, and fibers, from 2 Mt in 1950 to 380 Mt in 2015, which continues to this day. These uses generated 42 Mt plastic waste in the U.S, where over 75 % of which ends up in landfills where its decomposition is exceedingly slow. So far, there have been limited economically viable strategies for addressing this issue through either catalytic or non-catalytic processes. Thus, my independent research group is dedicated to developing approaches that efficiently convert discarded plastics into value-added products to limit the environmental burden. The developed catalytic system will extend the usefulness of fossil-derived products in new applications and displace the need for virgin materials.

In order to achieve this vision, my research group will focus on (1) the development of hydrophobic catalysts for indirect chemical recycling of BTX (benzene, toluene, and xylene), (2) the homogeneous oxidation reaction of polyolefins to produce oxygenated polymers/small molecules, and (3) heterogeneous catalytic system to achieve closed-loop recycling of biorenewable plastics. Our aim is to deepen understanding of the underlying mechanisms by investigating reaction kinetics and designing/characterizing catalysts, which will contribute to developing more efficient catalytic processes.

Postdoctoral Research at National Renewable Energy Laboratory (Dr. Beckham group)

My current research at NREL as a postdoctoral researcher focuses on redesigning reaction conditions in polystyrene autoxidation. By using cost-effective homogenous catalysts, the modified autoxidation exhibited ca. 3 times higher depolymerization rate and resulted in higher yields compared to those achieved in previous research. Techno-economic and life-cycle analyses confirmed a substantial reduction in minimum selling price, as well as ca. 20 % decrease in CO₂ emission compared to the conventional process. We are extending our capabilities to upcycle the products via bioconversion and heterogeneous catalysis.

Postdoctoral Research at the University of California, Santa Barbara (Dr. Scott group)

My research at UCSB focused on investigating the mechanism of oxidative cleavage for polypropylene (PP) and polyethylene (PE). The use of alkylhydroperoxide facilitates the formation of alkyl radicals by hydrogen atom abstraction from the polyolefin backbone, leading to b-scission of C-C bonds. According to IR, ¹H NMR, and 2D ¹H-¹³C HSQC/HMBC NMR, the functional groups in oxidized PE are predominantly internal ketones, while oxidized PP instead contains terminal methyl ketones, due to its different mechanism of chain cleavage. The developed process was successfully applied to convert post-consumer polyolefins (PP, PE, and their mixture) containing labels and dye additives to produce polar waxes. The polar waxes derived from PP and PE showed 2-4 times higher oxygen contents compared to conventional polar waxes.

1. Hyunjin Moon, Fumihico Shimizu, Kazuki Fukumoto, Susannah L. Scott, “Method of synthesizing polar waxes”, Provisional patent filed in December 2022.
2. Hyunjin Moon, Fumihico Shimizu, Kazuki Fukumoto, Hengbin Wang, Xiangcheng Sun, and Susannah L. Scott*, “Oxidative cleavage of polyolefins as a route to polar waxes”, Submitted.

Ph.D. Research at the University of California, Santa Barbara (Dr. Scott group)

During my Ph.D. at UCSB, my primary research focused on designing SBA-15 type mesoporous catalysts with gradually changing surface hydrophobicity and investigating catalyst surface effects for the improved hydrogenation of aromatic reactants. The use of operando solid-state NMR and ex-situ adsorption test confirmed that enhanced adsorption of aromatic reactants on the surface enables faster and more selective hydrogenation. By using ODNP method, we showed that ordered surface water structure can be formed on organosilica surfaces, which further improves the adsorption of reactants, suggesting a new strategy for catalyst surface design. In addition, we conducted research on lifetimes and degradation rates of plastics in various environments. The research found out that the degradation rates of biodegradable plastics are unexpectedly comparable to those of conventional polyolefins. In addition, the research emphasized the importance of improved experimental studies for plastic degradation with clearly defined reaction conditions.

1. Hyunjin Moon, Jason A. Chalmers, Ali Chamas, Susannah L. Scott*, “Operando NMR observation of molecular adsorption during phenol hydrogenation catalyzed by Pd and the effect of surface polarity”, In preparation.
2. Jason A. Chalmers, Hyunjin Moon, Samantha F. Ausman, Cheng-Hsun Chuang, and Susannah L. Scott*, “Enhancing phenol adsorption on Pd/SiO₂ to achieve faster and more selective hydrogenation, Topics in Catalysis, In review.
3. Hyunjin Moon, Ryan P. Collanton, Jacob I. Monroe, Thomas M. Casey, M. Scott Shell, Songi Han*, and Susannah L. Scott*, “Evidence for entropically controlled interfacial hydration in mesoporous organosilicas”, Journal of the American Chemical Society, 2022, 144, 1766-1777
4. Hyunjin Moon, Songi Han, Susannah L. Scott*, “Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity”, Chemical Science, 2020, 11, 3702-3712
5. Ali Chamas, Hyunjin Moon, Jiajia Zheng, Yang Qiu, Tarnuma Tabassum, Jun Hee Jang, Mahdi Abu-Omar, Susannah L. Scott*, Sangwon Suh*. “Assessing degradation rates of plastics in the environment”, ACS Sustainable Chemistry & Engineering, 2020, 8, 9, 3494-3511

Master’s Research at Seoul National University under Dr. Seung Hwan Ko

Prior to starting Ph.D., my M.S. research aimed to develop a conducting polymer/metal nanowire-based wearable devices via electropolymerization. In addition, the interrelationship among the reaction parameters for nanomaterial synthesis was investigated.

1. Hyunjin Moon, Habeom Lee, Jinhyeong Kwon, Young Duk Suh, Dong Kwan Kim, Inho Ha, Junyeob Yeo*, Sukjoon Hong*, and Seung Hwan Ko*, “Ag/Au/polypyrrole core-shell nanowire network for transparent, stretchable and flexible supercapacitor in wearable energy devices”, Scientific Reports, 2017, 7, 41981
2. Hyunjin Moon, Phillip Won, Jinhwan Lee, and Seung Hwan Ko*, “Low-haze, annealing-free, very long Ag nanowire synthesis and its application in a flexible transparent touch panel”, Nanotechnology, 2016, 27, 295201

Teaching Interests

During my master’s and Ph.D. studies, I have had diverse experiences that have nurtured my passion for teaching and helped me develop a keen interest into teaching. As a master student at Seoul National University, I gave lectures to undergraduate students from Thailand on how nanoscience and engineering are used to tackle the conventional issues regarding lithium batteries, sensor devices, and flexible electronics. In addition, they were able to gain practical experience through engaging in hands-on laboratory activities, involving the synthesis of nanomaterials and acquiring proficiency in the operation of characterization equipment. This was the time that I recognized the critical need for active teaching approaches. During the Ph.D. student at UCSB, I have served as a teaching assistant for General Chemistry Lab, Chemical Engineering Lab courses, and Reaction Engineering where I led lab/review sessions, and provided constructive feedback on student’s assignments. As I saw more students actively engaging and participating in my classes, I have come to the realization that teaching is highly fulfilling and rewarding. I have further delved into my teaching philosophy by taking a pedagogy class at UCSB where I learned about the effective teaching methods and gave several presentations to undergraduate students on how general chemical knowledge is expanded to real-world technologies. My primary objective in teaching is to motivate and excite students by bridging the gap between theoretical knowledge and real-world problem-solving. By doing so, I strive to empower them to become independent thinkers and effective problem solvers. The second goal I have in teaching is to enhance students’ confidence by designing progressively challenging problems. Through this approach, I aim to provide them with opportunities to develop their abilities, ultimately fostering a sense of self-assurance in their academic pursuits. Lastly, I focus on cultivating on inclusive learning environment that values and respect diverse perspectives.

I have a deep passion for implementing the most effective teaching strategies from literatures into my classes. I have a keen interest in teaching kinetics, catalysis, and polymer synthesis/physics courses at both the undergraduate and graduate level. Additionally, I am enthusiastic about developing classes regarding plastic recycling/upcycling. Furthermore, I am interested in teaching core courses in chemical engineering subjects such as thermodynamics and heat/mass transport. I believe that these fundamental courses play a crucial role in building a strong foundation for students pursuing a career in chemical engineering.