Faculty Publications
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Publications by NITK Faculty
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Item Oxidation and Reduction of Biomass-Derived 5-(Hydroxymethyl)furfural and Levulinic Acid by Nanocatalysis(American Chemical Society, 2020) Dutta, S.; Bhat, N.S.; Vinod, N.Nanocatalysis combines the advantageous characteristics of both homogenous and heterogeneous catalysis while reducing their respective drawbacks. In recent years, nanocatalysts are increasingly being used in the chemical-catalytic conversion of biomass into value-added fuels and specialty chemicals. 5-(Hydroxymethyl)furfural (HMF) and levulinic acid (LA) are well-documented biomass-derived chemical intermediates that can be synthetically modified into products of commercial significance. Nanocatalysts have played a crucial role in the selective oxidation and reduction of HMF and LA into high-value compounds. In some cases, nanocatalysts provide selectivity and reactivity under relatively mild reaction conditions that could not be achieved by conventional homogeneous or heterogeneous catalysts. Over the years, a thorough understanding of the size-dependent properties of nanoparticles, the interactions among various components of catalysts including support materials, and the interactions of starting materials or products with the catalytic materials have helped in fine-tuning the new generation of nanocatalysts for unprecedented reactivities and selectivities toward the products of interest. In this chapter, the use of nanocatalysts for the selective oxidation and reduction of HMF and LA into valuable chemicals is elaborated, and the future prospects of nanocatalysts in this area are appraised. © 2020 American Chemical Society.Item High-yielding synthesis of alkyl stearates from stearic acid within a closed batch reactor using heteropolyacids as efficient and recyclable catalyst(American Institute of Physics Inc. subs@aip.org, 2020) Vinod, N.; Tiwari, R.; Bhat, N.S.; Mal, S.S.; Dutta, S.This study reports high-yielding and scalable synthesis of alkyl stearates from stearic acid (SA) within a closed batch reactor using commercially-available heteropolyacid catalysts. The reaction was carried out by using different commercially-available heteropolyacids and reaction conditions were optimized by using phosphotungstic acid (PTA) catalyst. The solvent-free, gram-scale reactions afforded alkyl stearates in excellent isolated yields (>95%) within 4?h at 110 °C using slight excess of alcohols and only 1?mol% of the phosphotungstic acid (PTA) catalyst. The PTA catalyst was successfully recovered and reused for five consecutive cycles without significant loss in mass or activity. © 2020 Author(s).Item A straightforward preparation of levulinic esters from biorenewable levulinic acid using methanesulfonic acid supported on silica gel (MSA-SG) as an efficient heterogeneous catalyst(Elsevier Ltd, 2023) Vinod, N.; Bandibairanahalli Onkarappa, S.; Madhwaraj Girija, V.; Dutta, S.The present work reports methanesulfonic acid supported on silica gel (MSA-SG) as an inexpensive heterogeneous solid acid catalyst for the high-yielding production of various alkyl levulinates from biomass-derived levulinic acid. The catalyst was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The reactions were conducted in a batch-type glass pressure reactor under conventional heating. The esterification reaction was optimized on temperature, duration, and catalyst loading. The optimized reaction conditions (120 °C, 8 h, 8 wt% MSA-SG) afforded methyl- to butyl levulinate in excellent isolated yields (≥90 %). The catalyst was filtered, and the products were purified by simply evaporating the excess alcohol reagent. © 2022Item Semi-Active Vibration Isolation of a Modular Magnetorheological Elastomer Device with ON-OFF and Fuzzy Logic Control(Institute of Physics, 2025) Sathiyasai, S.; Kamath, N.; Shenoy, K.P.; Vinod, N.; Rao, G.; Gangadharan, G.A modular device incorporating a magnetorheological elastomer (MRE) has been developed for vibration isolation applications. Following characterisation of its open-loop dynamic behaviour, this study investigates semi-active control strategies - ON/OFF control, proportional-integral-derivative (PID) control, and fuzzy logic control - targeting vibration attenuation at a dominant frequency of 12 Hz. These controllers dynamically adjust the MRE's damping properties by modulating the electromagnet's magnetic field in response to input vibration signals. Performance was evaluated using a shaker setup with a defined vibration spectrum, with the electromagnet's power consumption serving as a key metric. Experimental results show that ON/OFF control consumed the highest energy, drawing an average current of 2.5 A (26 W) and using 130 J over 5 s. While fuzzy logic control achieved the lowest consumption, a 72.5 % reduction compared to ON/OFF and 37.2 % less than PID. These findings highlight fuzzy logic control as the most energy-efficient strategy, offering significant power savings without compromising vibration isolation performance. © Published under licence by IOP Publishing Ltd.Item Energy Densification of Biomass-Derived Furfurals to Furanic Biofuels by Catalytic Hydrogenation and Hydrodeoxygenation Reactions(Multidisciplinary Digital Publishing Institute (MDPI), 2021) Vinod, N.; Dutta, S.The concomitant hydrolysis and dehydration of biomass-derived cellulose and hemicellulose to furfural (FUR) and 5-(hydroxymethyl)furfural (HMF) under acid catalysis allows a dramatic reduction in the oxygen content of the parent sugar molecules with a 100% carbon economy. However, most applications of FUR or HMF necessitate synthetic modifications. Catalytic hydrogenation and hydrogenolysis have been recognized as efficient strategies for the selective deoxygenation and energy densification of biomass-derived furfurals generating water as the sole byproduct. Efficient and eco-friendly catalysts have been developed for the selective hydrogenation of furfurals affording renewable furanic compounds such as 2-methylfuran, 2,5-dimethylfuran and 2-methyltetrahydrofuran with potential applications as biofuel, solvent and chemical feedstock. Hydrogen gas or hydrogen donor molecules, required for the above processes, can also be renewably obtained from biomass using catalytic processes, enabling a circular economy. In this review, the recent developments in the energy densification of furfurals to furanic compounds of commercial significance are elaborated, emphasizing the role of catalyst and the reaction parameters employed. Critical discussion on sourcing hydrogen gas required for the processes, using hydrogen donor solvents, catalyst design and the potential markets of furanic intermediates have been made. Critical evaluations of the accomplishments and challenges in this field are also provided. © 2021 by the authors.Item Catalytic conversion of glucose and its biopolymers into renewable compounds by inducing C–C bond scission and formation(Springer Science and Business Media Deutschland GmbH, 2024) Anchan, H.N.; Bhat, N.S.; Vinod, N.; Prabhakar, P.S.; Dutta, S.Transportation fuels and chemicals can be produced renewably by selectively altering the carbon skeleton of biomass-derived glucose. The predominantly catalytic processes incorporate carbon–carbon (C–C) bond scission and formation reactions with concomitant defunctionalization and refunctionalization steps. The production and synthetic upgrading of various biochemicals achieved by the C–C bond-scission (C1–C5) and C–C bond-forming (> C6) reactions from glucose and its biopolymers (e.g., starch, cellulose) have been reviewed. The details of transforming glucose and its polymers into targeted biochemicals, such as mechanistic pathway, process parameters, product selectivity, and specifics of the catalysts employed, have been elaborated. The interconversions of these chemicals of commercial significance under catalytic conditions are also highlighted. This review will assist the researchers in comprehending this field from a distinct perspective, reassess the challenges, identify the research gaps, and critically appraise the emerging research avenues. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022.Item Hydrochloric acid-catalyzed coproduction of furfural and 5-(chloromethyl)furfural assisted by a phase transfer catalyst(Elsevier Ltd, 2020) Bhat, N.S.; Vinod, N.; Onkarappa, S.B.; Dutta, S.Furfural has been produced in 53% isolated yield from D-xylose within an aqueous HCl-1,2-dichloroethane biphasic reaction mixture using benzyltributylammonium chloride (BTBAC) as a phase transfer catalyst. The use of BTBAC noticeably improved the yield of furfural compared to that in the control reaction. The reaction was optimized on the reaction temperature, duration, concentration of HCl, and the loading of BTBAC. Furfural and 5-(chloromethyl)furfural (CMF) have also been coproduced from a mixture of pentose and hexose sugars. Under optimized conditions (100 °C, 3 h, 20.2% HCl, 10 wt% BTBAC), CMF and furfural were isolated in 17% and 53% yield, respectively, from a mixture of glucose and xylose. In addition, levulinic acid was isolated from the aqueous layer in 31% yield. © 2020 Elsevier LtdItem Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst(MDPI, 2023) Vinod, N.; Dutta, S.This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support. © 2023 by the authors.Item Efficient Preparation of the Esters of Biomass-Derived Isohexides by Base-Catalyzed Transesterification under Solvent-Free Conditions(American Chemical Society, 2023) Bhat, N.S.; Vinod, N.; Tarafder, K.; Nayak, M.K.; Jana, A.; Mal, S.S.; Dutta, S.The monoesters and diesters of glucose-derived isosorbide (IS) have potential applications as sustainable dispersants, surfactants, emulsifiers, monomer units for polymers, and plasticizers. This work reports a solvent-free, high-yielding, and scalable pathway for producing the monoesters and diesters of IS by a transesterification reaction using K2CO3 as an efficient, inexpensive, and recyclable base catalyst. In the case of monoesters, the selectivity toward the exo-monoester of IS was found higher than that toward the endo-monoester. The methodology was successfully extended to synthesize the monoesters and diesters of isomannide and isoidide. The gram-scale preparation of alkyl, vinyl, and aryl esters of isohexides was optimized on the reaction temperature, duration, equivalence of the ester reagent, and catalyst loading. Under optimized conditions (50 mol % K2CO3, 180 °C, 6 h), various aryl and alkyl esters of the isohexides were isolated in satisfactory yields. The unsymmetrical diesters of the isohexides were conveniently synthesized by stepwise transesterification. © 2023 American Chemical Society.