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Saikat Chakraborty, Speaker at Chemical Engineering Conferences
Indian Institute of Technology Kharagpur, India
Title : Rapid, ionic liquid mediated catalytic conversion of lignocellulosic Sunn hemp fibres to biofuel precursors


Lignocelluloses from non-food crops are considered to be the most important feedstock for second generation biofuel production since they do not conflict with food sources. We use non-edible cellulose-rich lignocellulosic Sunn hemp fibres – containing 75.6% cellulose, 10.05% hemicellulose, 10.32% lignin, with high crystallinity (80.17%) and degree of polymerization (650) – as a new non-food substrate for lignocellulosic biofuel production. Microwave irradiation is employed to rapidly rupture the cellulose’s glycosidic bonds and enhance glucose yield to 78.7% at 160°C in only 46 min. The reactants – long-chain cellulose, ionic liquid, transition metal catalyst, and water – form a polar supramolecular complex that rotates under the dual-mode microwave’s alternating polarity and rapidly dissipates the electromagnetic energy through molecular collisions, thus accelerating glycosidic bond breakage. In 46 minutes, 1 kg of Sunn hemp fibres containing 756 g of cellulose produces 595 g of glucose at 160 °C, and 203 g of hydroxymethyl furfural (furanic biofuel precursor) at 180°C. Yeast (Saccharomyces cerevisiae) mediated glucose fermentation produces 75.6% bioethanol yield at 30°C, and the ionic liquid is recycled for cost-effectiveness.
We also present experimental evidences of chemical chaos, which is observed when the Sunn hemp fibres are hydrolyzed using the same ionic liquid and the transition metal catalyst in well-mixed batch reactors heated to 110°C by an oil-bath instead of a microwave. The catalytic hydrolysis of lignocelluloses produces chaotic strange attractors with fractal dimensions and positive Lyapunov coefficients on the product phase spaces. All the 5 products (glucose, fructose, hydroxymethyl furfural (HMF), levulinic acid (LA), and formic acid (FA)) exhibit aperiodic (i.e., non-repetitive) temporal oscillations, peaking at 5 hours for water-addition rates ranging from 25 to 43 µl/gm/hr, when the hydrolysis system operates in the domain of chemical chaos. 37.5 µl/gm/hr of water-addition maximizes the concentrations of glucose, LA, FA at all times, with their average yields peaking at 5 hours to 67.5%, 12.4%, and 5%, respectively. At water-addition rates of 45 µl/gm/hr and higher, the system operates close to its thermodynamic equilibrium, resulting in the temporal oscillations to disappear completely, though the yields of glucose and HMF continue to peak at 5 hours. We show that the peak non-equilibrium yield of glucose obtained at the water-addition rate of 37.5 µl/gm/hr is 15% higher than its corresponding peak equilibrium yield at 45 µl/gm/hr of water addition, leading to a 15% increase in bioethanol production.


Dr. Saikat Chakraborty is an Associate Professor in the Department of Chemical Engineering at the Indian Institute of Technology Kharagpur, with joint affiliation at the School of Energy Science and Engineering, and the PK Sinha Center for Bioenergy and Renewables. He did his PhD in Chemical Engineering from University of Houston, USA, and his post-doctoral fellowship in Pulmonary Physiology from University of Texas Medical School. His areas of research include lignocellulosic and algal biofuels, and chemical pattern formation. He has published 50 international papers and has filed for 4 patents. He has received Young Engineer Award from Institute of Engineers India, Sigma Xi Research Achievement Award from the University of Houston, and is a member of the European Federation of Chemical Engineers’ Sustainability Section.