(2am) Reaction Engineering of Complex Systems (RECS): Towards Circularity and Sustainability

My research interests focus on addressing impactful problems that demand fundamental insight but have clear, practical applications. These crucial issues include mitigating the environmental impacts of a fossil fuel-based economy and managing plastic wastes. I have honed a diverse set of experimental and computational skills through my graduate and postdoctoral research experiences. I intend to leverage these skills to design experimental processes and develop modeling strategies to elucidate the chemistry of complex systems—for instance, chemical recycling and upcycling of end-of-life plastics, and the production of sustainable bio-based materials.

Research Vision:

Reaction Engineering of Complex Systems (RECS) Lab: I envision my research group to be positioned at the intersection of three fundamental areas of experimental process design, kinetic modeling, and characterization (using chromatography, spectroscopy, and other analytical techniques). A combination of these areas will be leveraged for practical applications to build a sustainable circular economy. Some of the topics that I am motivated to explore are: 1) designing cost-effective processes for chemical upcycling of resins and mixed plastics from discarded electronics and municipal solid wastes, 2) unraveling reaction mechanisms of complex systems that include the formation of microplastics in different environments, and the production of value-added chemicals from mixed plastic wastes, and 3) creating a database of various feedstock characterization to identify the composition of complex feedstocks, e.g., plastic wastes, in conjunction with machine learning tools like principal component analysis (PCA) and neural networks. As new problems emerge, this three-pronged approach can be adapted and applied to reaction systems from other interdisciplinary areas. I plan to forge new collaborations with other multidisciplinary research groups and industries to stimulate innovative ideas toward challenges in chemical engineering.

Research Experience:

Postdoctoral research: My current research at Northwestern University, with prof. Linda Broadbelt, involves developing mechanistic models to elucidate the depolymerization chemistry of plastics, viz. polyethylene, polyethylene terephthalate (PET), and polyurethanes (PU), for designing and optimizing recycling strategies. Modeling depolymerization of heterogeneous polymers such as PET and PU is challenging as each chain has a unique monomer sequence. I developed a framework that can reconstruct the initial polymer sequences along with crystallinity effects, and track depolymerization using the kinetic Monte Carlo (kMC) approach to explain PET and PU solvolysis chemistry. Importantly, I discovered the dominant pathways of catalyzed and uncatalyzed glycolysis that govern the recovery rate of bis(2-hydroxyethyl) terephthalate, a monomer of PET. I worked in collaboration with two multidisciplinary groups: 1) National Renewable Energy Laboratory (NREL) team, led by Dr. Robert Allen through the BOTTLE consortium, and 2) a team led by prof. Sanat Kumar from Columbia University to achieve a holistic understanding of the chemical recycling of PET.

Doctoral research: The primary focus of my doctoral research at Ghent University (advised by prof. Kevin Van Geem) centered around obtaining insights into the fast pyrolysis of lignocellulosic biomass model compounds to produce sustainable value-added chemicals. I applied PCA methods to evaluate the impact of feedstock composition on bio-oil product distribution. Further, I worked extensively with a tandem micropyrolyzer (Py) reactor coupled with a GCxGC-FID/TOF-MS and a customized GC to obtain detailed product distributions of the pyrolysis vapors, including water. Through such comprehensive analysis, I uncovered the differences between dominant reaction pathways of model compounds, namely cellulose and hydroxycinnamic acids.

Furthermore, I briefly worked on a few industrial projects involving micro to bench-scale reactors. The applications ranged from upcycling low- and high-density polyethylenes to analyzing the compositional effects of hydrocarbon feedstocks on the production of ethane, ethylene, and other gases.

Masters research: My research at the Indian Institute of Technology Madras (advised by prof. Vinu Ravikrishnan) focused on the pretreatment of cellulose through traditional and non-conventional techniques. I developed a continuum kinetic model coupled with linear regression-based rate-parameter optimization to elucidate acid hydrolysis kinetics of cellulose into value-added chemicals. Further, I investigated the impact of ultrasound-assisted alkaline pretreatment on enzymatic hydrolysis of cellulose. I utilized a combination of spectroscopic and microscopic methods, and hydrolysis experiments to study the formation of glucose, an important platform chemical.

Teaching Interests

Teaching Experience:

My enthusiasm for teaching began as an undergraduate student in India when volunteering as a part-time teacher for middle and high school students. I created lesson plans and designed assignments for middle school science. I organized regular lab activities to help students connect classroom teaching to real-world phenomena.

At the Indian Institute of Technology Madras, I was a graduate teaching assistant for two core undergraduate-level courses: Chemical reaction engineering, and Momentum transfer and Mechanical operations lab, where I trained students to collect and analyze data from experiments, organized assignments, and evaluated exams.

I supervised two master’s dissertation projects at Ghent and an undergraduate research project at Northwestern University. My mentoring experience taught me to find ways to help comprehend difficult topics to make the learning process efficient.

To further my teaching skills, I attended an “Advanced learning through evidence-based teaching” certification course through a Massive Open Online Course by CIRTL Network. The course enabled me to identify the learning objectives of a class, include different learning methods, and design assignments that contain higher levels of Bloom’s taxonomy. I have been selected for Northwestern University’s Teaching Certificate Program (AY 2022-2023), through which I plan to expand my knowledge of inclusive teaching practices, course design, learning, and assessment methods.

Teaching Vision:

With all my teaching experience, I am prepared to teach any core chemical engineering course. I am particularly enthusiastic about teaching Chemical engineering kinetics and reactor design, Chemical engineering thermodynamics, Introduction to chemical engineering, and Chemical engineering laboratory, as these topics align with my research interests. I am excited to design elective courses on Polymer engineering, Energy and sustainability, and Advanced characterization techniques for chemical analysis, depending on the needs of the department. Regardless of the course, I will incorporate a combination of evidence-based pedagogical approaches mentioned above to enhance the learning experience. Through carefully designed activities and assignments, I will foster technical excellence among students enabling them to apply classroom teaching to address challenges in chemical engineering.

Selected Publications

1. SriBala, G.; Vargas, D. C.; Kostetskyy, P.; Van de Vijver, R.; Broadbelt, L. J.; Marin, G. B.; & Van Geem, K. M., New Perspectives into Cellulose Fast Pyrolysis Kinetics Using a Py-GC× GC-FID/MS System. ACS Engineering Au, 2022.
2. Harmon, R.E.; SriBala, G.; Broadbelt, L.J.; Burnham, A.K., Insight into Polyethylene and Polypropylene Pyrolysis: Global and Mechanistic Models. Energy Fuels, 2021, 35(8), 6765-6775.
3. SriBala, G.; Van de Vijver, R.; Li, L.; Dogu, O.; Marin, G.B.; Van Geem, K.M., On the Primary Thermal Decomposition Pathways of Hydroxycinnamic Acids. Proc. Combust. Inst., 2020, 38(3), 4207-4214.
4. SriBala, G.; Chennuru, R.; Mahapatra, S.; Vinu, R., Effect of alkaline ultrasonic pretreatment on crystalline morphology and enzymatic hydrolysis of cellulose. Cellulose, 2016, 23, 1725-1740.
5. SriBala, G.; Vinu, R., Unified kinetic model for cellulose deconstruction via acid hydrolysis. Ind. Eng. Chem. Res., 2014, 53, 8714-8725.