(2eo) Advancing Sustainable Chemistry through Experimental and Computational Approaches to Multi-Phase Chemical Reaction Processes

Replacing chemical processes that are powered by fossil fuels and use petrochemical feedstocks with those driven by renewable electricity and sustainable chemical precursors is paramount to establish a sustainable chemicals industry. My research group will make a meaningful contribution to this generational challenge by designing new chemical synthesis routes that leverage unconventional and renewable material inputs and chemical driving forces.

In pursuit of sustainable chemistry, my group will harness synergistic effects of two or more complementary chemical functions to achieve new possibilities for reactivity and product selectivity in homogeneous (liquid phase) and heterogeneous (surface catalyzed) processes. One aspect of our research will generate free radicals in aqueous solution using high-frequency ultrasound as a low-carbon electricity-powered energy source to functionalize organic substrates into chemical products of value. In another, we will pioneer the design of heterogeneous catalyst materials with multiple complementary chemical functions that synergistically couple during reaction timescales. By integrating first principles calculations, multi-scale models (e.g. micro-kinetic modeling, kinetic Monte Carlo simulations, continuum-level transport models), and experimental reaction kinetics, we will comprehensively understand intrinsic chemical reactivity and simulate reaction rates under prevalent experimental conditions. By uniting these theoretical, computational, and experimental tools we will envision new chemical processes, simulate their performance, and rigorously validate their feasibility to address real-world challenges in practice.

Research Background

My dissertation research with Professor Enrique Iglesia at the University of California, Berkeley (UC Berkeley) aimed to resolve a long-standing controversy surrounding how hydrogenation rates of unsaturated hydrocarbons (e.g. alkenes and arenes) on metal nanoparticle surfaces (e.g. Pt) are promoted by nominally inert metal-oxide scaffolds (e.g. Al₂O₃, MgO, and TiO₂). With toluene hydrogenation to methylcyclohexane as a probe reaction, we discovered that partially hydrogenated species derived from toluene (e.g. methylcyclohexene isomers) form at low concentrations (<1 Pa) dictated by the kinetics of toluene-H₂ reactions at Pt-surfaces. While toluene is unreactive at Al₂O₃ surfaces, toluene derived cyclo-alkenes and cyclo-alkadienes are hydrogenated by H₂ adsorbed at surface Lewis-acid-base pairs (vicinal Al-O). I unified the newfound hydrogenation activity of Al₂O₃ surfaces with a mechanistic picture for toluene-H₂ reactions at Pt surfaces through reaction-transport formalisms to describe the mechanism underlying promotional effects conferred by non-conductive oxides. To gain these valuable mechanistic insights, I obtained rigorous experimental kinetics, developed continuum reaction-transport models, derived thermodynamic descriptions of densely covered metal surfaces using lattice statistics, and calculated energies of prevalent surface intermediates using plane-wave density-functional theory calculations. These mechanistic insights and the quantitative framework I have developed enable new avenues to improve catalyst performance by leveraging bifunctional synergies, with particular relevance to the hydrogenation-dehydrogenation processes central to emerging applications of organic molecules as substrates for H₂ storage and transport.

My postdoctoral research with Professor Tej S. Choksi at Nanyang Technological University (NTU) in Singapore applies robust modeling techniques to understand and simulate mechanisms that utilize free radicals derived from ultrasound to upgrade biomass feedstocks into valuable chemicals. A renaissance in ultrasound-induced “sonochemistry” has led to the discovery of diverse applications including selective oxidation, depolymerization, and amination chemistry. I devised a robust multi-scale modeling framework parameterized by rate constants from first-principles calculations that enabled reaction rates and product selectivity for aldehyde oxidation and aromatic fragmentation to be predicted with chemical accuracy. These model predications were validated against kinetic and electron paramagnetic resonance (EPR) measurements performed by teams of experimental collaborators at the French National Centre for Scientific Research (CRNS; France) and NTU. In doing so, I uncovered the nature of prevalent radical initiators, key radical-mediated elementary steps, and solvent effects for these reactions. These mechanism-based descriptions of reactivity were used to predict experimental operating conditions for the selective formation of desired products. This framework for mechanistic inquiry advances the field of sonochemistry from beyond speculative mechanisms towards mechanism-based descriptions of reactivity. Such rigorous mechanistic insights are essential for process design and energy optimization studies of sonochemical reactors for sustainable chemical synthesis.

Teaching Interests

As a highly trained chemical engineer with experience in both experimental and computational research, I am prepared to teach any of the core courses in the chemical engineering curriculum. I am particularly enthusiastic to teach undergraduate and graduate-level reaction kinetics and statistical/classical thermodynamics, an undergraduate elective on sustainable chemistry, and a graduate elective on multi-scale modeling approaches to multi-phase chemical processes. My experience as a graduate student instructor at UC Berkeley has prepared me to teach effectively to a diverse group of students. There, I taught Introduction to Chemical Engineering Design (1^st year), Transport Processes (2^nd year), and Chemical Engineering Laboratory (3^rd year). In these roles, I developed course materials, gave lectures, prepared exams and homework assignments, held office hours, and offered mentorship to students facing difficulties. From these experiences and feedback from students, I have learned that a range of pedagogical approaches are necessary to reach a diverse group of students. As one example, my lessons will incorporate physical demonstrations and computer simulations of complex chemical engineering phenomena to engage visual learners. I am also passionate about scientific outreach and research dissemination; to this end, I am developing tools to express results from my research through music to engage an audience beyond the scientific community. Furthermore, mentoring students and engaging with the community in Singapore has prepared me to support, educate, and learn from students and colleagues from diverse backgrounds different from my own. These experiences will help me to foster a safe, inclusive, and diverse research and classroom environment that celebrates contributions from students of all communities and backgrounds and encourages them to reach their educational goals.