Arul Mozhi Devan Padmanathan - Academia.edu (original) (raw)

Arul Mozhi Devan Padmanathan

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Papers by Arul Mozhi Devan Padmanathan

Research paper thumbnail of Pyrolytic activation of cellulose: energetics and condensed phase effects

Reaction Chemistry & Engineering, 2022

Computational strategies used to capture condensed phase effects provide a novel outlook on cellu... more Computational strategies used to capture condensed phase effects provide a novel outlook on cellulose chemistry. With phase transition, cellulose primary decomposition has a significant entropic penalty below 900 K but is enthalpy controlled beyond.

Research paper thumbnail of Understanding Acidity of Molten Salt Hydrate Media for Cellulose Hydrolysis by Combining Kinetic Studies, Electrolyte Solution Modeling, Molecular Dynamics Simulations, and 13C NMR Experiments

ACS Catalysis, 2019

Depolymerization of lignocellulosic biomass in concentrated metal salts and more specifically in ... more Depolymerization of lignocellulosic biomass in concentrated metal salts and more specifically in acidified LiBr molten salt hydrate (AMSH) results in high glucose yields at low acid concentrations, low temperatures, and very short times with potentially considerable economic benefits. However, our understanding of this promising medium is limited. Here, we study the effect of different LiBr concentrations on acidity and hydrolysis of cellobiose, a cellulose surrogate molecule, in dilute H 2 SO 4 solutions. We use thermodynamic modeling to predict the H + (hydron) activity and the speciation and correlate these with the experimentally measured reaction rates. We find that the main contribution of the salt to the reactivity stems from the dramatic increase in H + activity and secondary to an interaction of salt with the acid species that effectively renders the inorganic acid very strong. We perform molecular dynamics simulations and reveal that the increased hydron activity can be attributed to the decrease in the number of water molecules in the hydron solvation shell upon salt addition. Additionally, we extend the analysis to other salts and acids concluding that the effects of different cations, anions, and acids in cellobiose hydrolysis can likewise be primarily attributed to changes in acidity. A key physicochemical descriptor of various salts is their enthalpy of dissolution. Finally, we explore the use of 13 C-NMR spectroscopy to estimate the pH of AMSH solutions.

Research paper thumbnail of Predictive Framework for the Spreading of Liquid Drops and the Formation of Liquid Marbles on Hydrophobic Particle Bed

Langmuir, 2019

In this work, we have developed a model to describe the behavior of liquid drops upon impaction o... more In this work, we have developed a model to describe the behavior of liquid drops upon impaction on hydrophobic particle bed and verified it experimentally. Polytetrafluoroethylene (PTFE) particles were used to coat drops of water, aqueous solutions of glycerol (20, 40 and 60 v/v %) and ethanol (5 and 12 v/v %). The experiments were conducted for Weber number (We) ranging from 8 to 130 and Reynolds number (Re) ranging from 370 to 4460. The bed porosity was varied from 0.8-0.6. The experimental values of max (ratio of the diameter at the maximum spreading condition to the initial drop diameter) were estimated from the time lapsed images captured using a high-speed camera. The theoretical max was estimated by making energy balances on the liquid drop. The proposed model accounts for the energy losses due to viscous dissipation and crater formation along with a change in kinetic energy and surface energy. A good agreement was obtained between the experimental max and the theoretical max estimated. The proposed model yielded least % Absolute Average Relative Deviation (%AARD) of 5.5  4.3 when compared with other models available in the literature. Further, it was found that the liquid drops impacting on particle bed are completely coated with PTFE particles with max values greater than 2.

Research paper thumbnail of Pyrolytic activation of cellulose: energetics and condensed phase effects

Reaction Chemistry & Engineering, 2022

Computational strategies used to capture condensed phase effects provide a novel outlook on cellu... more Computational strategies used to capture condensed phase effects provide a novel outlook on cellulose chemistry. With phase transition, cellulose primary decomposition has a significant entropic penalty below 900 K but is enthalpy controlled beyond.

Research paper thumbnail of Understanding Acidity of Molten Salt Hydrate Media for Cellulose Hydrolysis by Combining Kinetic Studies, Electrolyte Solution Modeling, Molecular Dynamics Simulations, and 13C NMR Experiments

ACS Catalysis, 2019

Depolymerization of lignocellulosic biomass in concentrated metal salts and more specifically in ... more Depolymerization of lignocellulosic biomass in concentrated metal salts and more specifically in acidified LiBr molten salt hydrate (AMSH) results in high glucose yields at low acid concentrations, low temperatures, and very short times with potentially considerable economic benefits. However, our understanding of this promising medium is limited. Here, we study the effect of different LiBr concentrations on acidity and hydrolysis of cellobiose, a cellulose surrogate molecule, in dilute H 2 SO 4 solutions. We use thermodynamic modeling to predict the H + (hydron) activity and the speciation and correlate these with the experimentally measured reaction rates. We find that the main contribution of the salt to the reactivity stems from the dramatic increase in H + activity and secondary to an interaction of salt with the acid species that effectively renders the inorganic acid very strong. We perform molecular dynamics simulations and reveal that the increased hydron activity can be attributed to the decrease in the number of water molecules in the hydron solvation shell upon salt addition. Additionally, we extend the analysis to other salts and acids concluding that the effects of different cations, anions, and acids in cellobiose hydrolysis can likewise be primarily attributed to changes in acidity. A key physicochemical descriptor of various salts is their enthalpy of dissolution. Finally, we explore the use of 13 C-NMR spectroscopy to estimate the pH of AMSH solutions.

Research paper thumbnail of Predictive Framework for the Spreading of Liquid Drops and the Formation of Liquid Marbles on Hydrophobic Particle Bed

Langmuir, 2019

In this work, we have developed a model to describe the behavior of liquid drops upon impaction o... more In this work, we have developed a model to describe the behavior of liquid drops upon impaction on hydrophobic particle bed and verified it experimentally. Polytetrafluoroethylene (PTFE) particles were used to coat drops of water, aqueous solutions of glycerol (20, 40 and 60 v/v %) and ethanol (5 and 12 v/v %). The experiments were conducted for Weber number (We) ranging from 8 to 130 and Reynolds number (Re) ranging from 370 to 4460. The bed porosity was varied from 0.8-0.6. The experimental values of max (ratio of the diameter at the maximum spreading condition to the initial drop diameter) were estimated from the time lapsed images captured using a high-speed camera. The theoretical max was estimated by making energy balances on the liquid drop. The proposed model accounts for the energy losses due to viscous dissipation and crater formation along with a change in kinetic energy and surface energy. A good agreement was obtained between the experimental max and the theoretical max estimated. The proposed model yielded least % Absolute Average Relative Deviation (%AARD) of 5.5  4.3 when compared with other models available in the literature. Further, it was found that the liquid drops impacting on particle bed are completely coated with PTFE particles with max values greater than 2.

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