Professor Varma's research group investigates topics in hydrogen and other energy sources, and chemical and catalytic reaction engineering. The projects typically involve combined experimental and modeling studies.

A major current emphasis involves new methods to generate hydrogen for fuel cells, for both portable applications such as notebook computers and mobile phones, and vehicle transportation. For portable applications, combustion of novel chemical mixtures is used to obtain high hydrogen yield and safe solid reaction products. For vehicle transportation applications, new methods (Ammonia Borane hydrothermolysis and thermolysis, with additives and under effective reaction heat management) have been developed in our laboratory. Regeneration of spent boron products to efficiently yield ammonia borane is also being investigated. The new methods to generate hydrogen for PEM fuel cell vehicle applications developed in our laboratory provide the highest hydrogen yield among all methods reported in the literature.

Other current energy-related directions involve feasibility studies for underground coal gasification in the state of Indiana, catalytic conversion of glycerol (byproduct of biodiesel production) to valuable chemicals, and development of new catalysts for oxidative coupling of methane to ethylene and higher hydrocarbons. A universal method for crude glycerol purification from different feedstock in biodiesel production has also been developed recently.

Another recent direction is carbon sequestration, which involves capture and storage of CO2. Specifically, we are developing new oxygen carriers for chemical looping combustion, a new technology with inherent separation of CO2 in power plants using fossil fuels, either natural gas or gas from coal and/or biomass gasifiers.

A major emphasis in recent years has been combustion synthesis, a process for the production of advanced materials. We have focused on understanding the mechanisms involved in the synthesis and structure formation of materials such as ceramics, intermetallics and composites. This understanding can be used to control the microstructure, and hence the properties, of advanced materials such as nanoscale oxide powders for adsorption and catalysis, intermetallic-ceramic composites for aerospace applications and alloys for orthopedic implants. Our current efforts in this area are focused on developing solution combustion synthesis, a one-step method for the preparation of nanostructured complex metal oxides with tailored composition, phase, oxidation state, and surface areas by variation of tunable synthesis parameters, for a variety of catalytic and other applications.

Other recent investigations in chemical and catalytic reaction engineering have included novel synthesis of metal-composite and ceramic membranes, inorganic membrane reactors, and multiphase reactors. Current research projects in multiphase reactors include two directions: hydrodynamics studies of trickle-bed reactors with a particle size distribution of catalyst support which has a significant effect on reactor performance, makes reactor modeling difficult and leads to failure of scale-up; and experimental hydrogenation studies for pharmaceutical applications.

Purdue Mexico Center for Sustainability

Professor Varma serves as the Director of the Purdue Mexico Center for Sustainability (PMCS). Building upon existing collaborations between Purdue University and Mexican institutions, PMCS aims to develop deeper relationships that will include education and research activities in bioenergy; nanotechnology for energy, environment and agriculture applications; engineering to mitigate natural disasters; and water management.

“Highly Selective Nonoxidative Coupling of Methane over Pt-Bi Bimetallic Catalysts,” Y. Xiao and A. Varma, ACS Catalysis, 8, 2735-2740 (2018).

"Hydrogen Generation from Hydrous Hydrazine over Ni/CeO2 Catalysts Prepared by Solution Combustion Synthesis," W. Kang, and A. Varma, Applied Catalysis B: Environmental, 220, 409-416 (2018).

"Mechanistic Elucidation of Thermal Runaway in Potassium-Ion Batteries," R. Adams, A. Varma and V. G. Pol, Journal of Power Sources, 375, 131-137 (2018).

"Tailored Solution Combustion Synthesis of High Performance ZnCo2O4 Anode Material for Lithium-ion Batteries," R. Adams, V. G. Pol and A. Varma, Industrial & Engineering Chemistry Research, 56, 7173-7183 (2017).

"Kinetics of Glycerol Conversion to Hydrocarbon Fuels over Pd/H-ZSM-5 Catalysts," Y. Xiao and A. Varma, AIChE Journal, 63, 5445-5451 (2017).

"Binder-free, N- and O- Rich Carbon Nanofiber Anodes for Long Cycle Life K-ion Batteries," R. Adams, J.-M. Syu, Y. Zhao, C.-T. Lo, A. Varma and V. G. Pol, ACS Applied Materials & Interfaces, 9, 17872-17881 (2017).

"Electrochemical Performance of MXenes as K-ion Battery Anodes," M. Naguib, R.A. Adams, Y. Zhao, D. Zemlyanov, A. Varma, J. Nanda and V. G. Pol, Chemical Communications, 53, 6883-6886 (2017).

"Kinetics of Guaiacol Deoxygenation Using Methane over Pt-Bi Catalyst," Y. Xiao and A. Varma, Reaction Chemistry & Engineering, 2, 36-43 (2017).

"Acetophenone Hydrogenation on Rh/Al2O3 Catalyst: Flow Regime Effect and Trickle Bed Reactor Modeling," S.B. Lee, N. Zaborenko and A. Varma, Chemical Engineering Journal, 317, 42-50 (2017).

"An Experimental and Theoretical Study of Glycerol Oxidation to 1,3-Dihydroxyacetone over Bimetallic Pt-Bi Catalysts," Y. Xiao, Z.J. Zhao, J. Greeley, G. Xiao and A. Varma, AIChE Journal, 63, 705-715 (2017).

"Solution Combustion Synthesis of Nanoscale Materials," A. Varma, A.S. Mukasyan, A.S. Rogachev and K.V. Manukyan, Chemical Reviews, 116, 14493-14586 (2016).

"The Effects of Particle Properties, Void Fraction, and Surface Tension on the Trickle-Bubbly Flow Regime Transition in Trickle Bed Reactors," G. S. Honda, J. H. Pazmino, E. Lehmann, D. A. Hickman and A. Varma, Chemical Engineering Journal, 285, 402-408 (2016).

"Acetophenone Hydrogenation on Rh/Al2O3 Catalyst: Intrinsic Reaction Kinetics and Effects of Internal Diffusion," S.B. Lee, Z. Yu, N. Zaborenko and A. Varma, Chemical Engineering Journal, 288, 711-723 (2016).

"Kinetic Study of Pd-Catalyzed Hydrogenation of N-Benzyl-4-Fluoroaniline," H.T. Hwang, J. R. Martinelli, R. Gounder and A. Varma, Chemical Engineering Journal, 288, 758-769 (2016).

"Conversion of Glycerol to Hydrocarbon Fuels via Bifunctional Catalysts," Y. Xiao and A. Varma, ACS Energy Letters, 1, 963-968 (2016).

"Aldol Condensation of n-Butyraldehyde in a Biphasic Stirred Tank Reactor: Experiments and Models," S.B. Lee and A. Varma, AIChE Journal, 61, 2228-2239 (2015).

"Effects of Pre-Wetting on Bubbly and Pulsing Flow Regime Transitions in Trickle-Bed Reactors," G. Honda, E. Lehmann, D. Hickman and A. Varma, Industrial & Engineering Chemistry Research, 54, 10253-10259 (2015).

"The Value of an Industrial Internship for a Graduate Student Education," G. S. Honda, J. Pazmino, D. A. Hickman, and A. Varma, Chemical Engineering Education, 49 (4), 195-200 (2015).

"Catalytic Deoxygenation of Guaiacol Using Methane," Y. Xiao and A. Varma, ACS Sustainable Chemistry & Engineering, 3, 2606-2610 (2015).

"Oxidative Coupling of Methane using Catalysts Synthesized by Solution Combustion Method: Catalyst optimization and kinetic studies," R. Ghose, H. T. Hwang and A. Varma, Applied Catalysis A: General, 472, 39-46 (2014).

"Conversion of Guaiacol on Noble Metal Catalysts: Reaction performance and deactivation studies," D. Gao, C. Schweitzer, H. T. Hwang and A. Varma, Industrial & Engineering Chemistry Research, 53, 18,658-18,667 (2014).

"Hydrogen Storage for Fuel Cell Vehicle Applications," H. T. Hwang and A. Varma, Current Opinion in Chemical Engineering, 5, 42-48 (2014).

"Perspective Article: Evolving Trends in Chemical Engineering Education," A. Varma and I. E. Grossmann, AIChE Journal, 60, 3692-3700 (2014).