(2dk) Unraveling Reaction Kinetics of Complex Systems for Sustainable Process Development

Sustainable process development and decarbonization are crucial steps towards mitigating climate change. Facilitating the transition from conventional methods of producing materials to the next generation of sustainable processes requires a fundamental understanding of complex reaction systems. While there are remarkable efforts towards meeting these grand challenges, knowledge gaps exist in understanding the multiscale chemical interactions of complex macromolecules, from waste management to human health. My research group will integrate high-throughput experimental and computational approaches to unravel the kinetics of complex reaction systems to drive the development of sustainable processes. Specifically, my research group will investigate multiscale, multiphase reaction chemistries that contribute to designing processes to produce value-added chemicals from wastes and renewables, remediate environmental contamination, and decarbonization. The initial stages of my research program will be dedicated to addressing the following research aims.

Developing energy-efficient microwave- and sonication-assisted catalytic processes for chemical transformations of complex feedstocks such as resins, mixed plastic wastes, and renewables.

Designing high-throughput experimental methods coupled with advanced analytics to unravel the intrinsic kinetics of depolymerization and decomposition of materials.

Developing kinetic modeling frameworks – conventional and machine learning-based models – to deepen the understanding of chemical and biochemical decomposition pathways of macromolecules to study their persistence in different environments.

Postdoctoral research (Advisor: Linda Broadbelt, Northwestern University)

During my postdoctoral research, I studied the pyrolysis chemistry of high-density polyethylene using continuous distribution kinetics to understand the effects of iso-thermal and transient reaction conditions on the temporal evolution of products and their final product yields. As a member of the BOTTLE consortium, I developed detailed kinetic Monte Carlo (KMC)-based frameworks to study the solvolytic depolymerization of heterogeneous polymers like polyethylene terephthalate (PET). I focused on understanding the distribution of repeating units in amorphous and crystalline phases of the polymer and their influence on reaction kinetics that govern the monomer recovery. Further, I discovered the impact of polymer morphology on PET hydrolysis kinetics under accelerated aging conditions with a system of 10⁵ unique chain sequences. I investigated the decomposition pathways of tails, loops, and ties of PET spherulites that eventually lead to micro and nano plastics forming under aquatic conditions. During these years, I collaborated with multidisciplinary teams from national labs and academic institutions to achieve a holistic understanding of the chemical recycling of post-consumer waste plastics.

Doctoral research (Advisor: Kevin Van Geem, Ghent University)

My doctoral research focused on obtaining insights into the fast pyrolysis of lignocellulosic biomass model compounds to produce sustainable value-added chemicals. I developed comprehensive experimental methods 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 discovered the dominant water-assisted decarboxylation pathways of lignin using model compounds hydroxycinnamic acids. By integrating experimental analysis and kinetic modeling, I investigated the influence of cellulose crystallinity on mid-chain scission and end-chain scission reactions that govern the formation of levoglucosan. Further, I evaluated the impact of feedstock composition on pyrolysis oil product distribution using principal component analysis coupled with k-means clustering methods. In addition, I worked with industrial collaborators on projects ranging from understanding the pyrolysis chemistry of low- and high-density polyethylenes in a microreactor to analyzing the compositional effects of hydrocarbon feedstocks on producing ethane, ethylene, and other gases using a bench-scale steam cracking reactor.

Master’s research (Advisor: Vinu Ravikrishnan, Indian Institute of Technology Madras)

My masters research centered around the pretreatment of cellulose through traditional and non-conventional techniques. I developed a continuous distribution kinetics model coupled with linear regression-based rate-parameter optimization to elucidate the acid hydrolysis kinetics of cellulose into value-added chemicals. Further, I investigated the impact of ultrasound-assisted alkaline pretreatment on the enzymatic hydrolysis of cellulose. I utilized a combination of spectroscopic and microscopic methods, and hydrolysis experiments to study the formation of glucose at relatively low temperatures via ultrasound-assisted hydrolysis.

Teaching Interests:

My teaching philosophy includes a learner-centered approach, and I am committed to creating an inclusive and intellectually stimulating learning environment. As a formally trained chemical engineer, I am prepared to teach all core courses, with a particular interest in introduction to chemical engineering, transport phenomena, chemical reaction engineering, and kinetics at graduate and undergraduate levels. I am interested in developing undergraduate-level courses on energy and sustainability, highlighting complex environmental challenges, producing value-added chemicals from renewable sources, recycling strategies, and life cycle analysis. In all the courses I teach, I am committed to supporting learning needs by setting class objectives, attending to student concerns, and creating a sense of belonging to help students succeed. I will incorporate concepts of diversity, equity, inclusion, and environmental justice in the courses to foster critical-thinking mindsets and reflect on the importance of DEI when pursuing careers as chemical engineers.

To build a stronger foundation as a teacher, I pursued a yearlong teaching certificate course (2022-2023) offered by Northwestern University’s Searle Center for Teaching and Learning. I independently designed inclusive course design strategies and developed syllabi, lesson plans, and assessment rubrics for an elective course on Introduction to Sustainability. Prior to that, I was a graduate teaching assistant for two core undergraduate-level courses, chemical reaction engineering, and mechanical operations lab, at IIT Madras. I trained students to collect and analyze data from experiments, organized assignments, and evaluated exams. During my PhD, I was a guest TA for an undergraduate-level analytical techniques course where I taught students the operations of GCxGC-FID/ToF-MS and elemental analysis. Beyond the classroom, I supervised two master’s thesis students and mentored an undergraduate research student. With all these experiences, I am equipped to build an effective and inclusive learning environment in all classes I teach.

Selected Publications (Total: 12, 8 first author, 4 co-authored)

Rorrer, N.A;* SriBala, G.;* Hesse, S. A.;* Singh, A.;* Morais, A. R.;* Buss, B. L.; Brandner, D.G.; Takacs, C. J.; DesVeaux J. S.; Curley J. B.; Uekert, T.; Nicholson, S. R.; Donohoe, B.S.; Browning; M., Quigley, J.; Miscall, J.; Tan, E.; Carpenter, A. C.; Breyta, G.; Baldwin, R. M.; Beckham, G.T.; Broadbelt, L.J.; Tassone, C.J.; Allen R.D. Triethylamine-catalyzed glycolysis of poly(ethylene terephthalate). (*shared first author; manuscript to be submitted, draft available upon request)

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.

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.

SriBala, G.; Toraman, H.E.; Symoens, S.; Dejardin, A.; Pilate, G.; Boerjan, W.; Ronsse, F.; Van Geem, K.M.; Marin, G.B., Analytical Py-GC/MS of Genetically Modified Poplar for the Increased Production of Bio-Aromatics. Comput. Struct. Biotechnol. J., 2019, 17, 599-610.

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.

SriBala, G.; Vinu, R., Unified kinetic model for cellulose deconstruction via acid hydrolysis. Eng. Chem. Res., 2014, 53, 8714-8725.

Selected Awards and Grants

Northwestern University Postdoctoral Association service grant (2022)

Rising Star in Chemical Engineering, MIT (2021)

European Union COST-SMARTCATs action short-term research grant (2017)

DAAD scholarship under DAAD-IIT Sandwich Program (2013-1014)