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Author: search.filters.author.Tiwari, R.

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    Straightforward synthesis of calcium levulinate from biomass-derived levulinic acid and calcium carbonate in egg-shells
    (Elsevier Ltd, 2019) Sharath, B.O.; Tiwari, R.; Mal, S.S.; Dutta, S.
    Calcium levulinate (CL) is a nutritional supplement for calcium and a chemical intermediate in synthesizing levulinic biofuels. The reported synthesis of CL involve reaction between cellulose-derived levulinic acid (LA) and calcium hydroxide in an aqueous medium. In this work, we report the production of CL using CaCO3 from poultry egg shells. The scalable production uses biomass-derived LA and egg-shell derived CaCO3 under conventional heating and mechanical stirring. The reaction was optimized on temperature, duration of reaction, and equivalent of CaCO3. Using 1.5 equivalent of CaCO3, the reaction completed within 2h at 50°C and afforded up to 97% isolated yield of CL as a crystalline solid. The reaction was also successfully carried out under mechanical grinding and scaled up to 20 g. The purity of the product was confirmed by melting point, FTIR, 1H-NMR and 13C-NMR spectroscopy. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials, Energy & Environmental Sustainability, ICAMEES2018
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    The hydrogen peroxide-mediated oxidation of biorenewable furfural to 2(5H)-furanone using heteropolyacids supported on ammonium y zeolite as the catalyst
    (Elsevier Ltd, 2020) Tiwari, R.; Bhat, N.S.; Mal, S.S.; Dutta, S.
    A series of heteropolyacid supported on ammonium Y zeolite (HPA-NH4YZ) catalysts were prepared and used for the catalytic oxidation of furfural to 2(5H)-furanone in aqueous hydrogen peroxide. The catalysts were characterized by PXRD, FTIR, TGA, and SEM analyses. The organic-solvent-free reaction was optimized on temperature, duration, loading of catalyst, and the equivalent of H2O2. The 20%PTA-NH4YZ catalyst showed the best catalytic activity giving 2(5H)-furanone in 40% isolated yield by solvent extraction under optimized conditions (20wt% cat., 100°C, 90min, 7.5eq. 30%H2O2). In addition, around 20% of succinic acid was recovered from the aqueous layer. © 2020 Elsevier Ltd. All rights reserved.
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    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).
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    A scalable and high-yielding synthesis of 2-(2-furyl)-1,3-dioxolane from biomass derived furfural and ethylene glycol using heteropoly acids as green catalyst
    (Chemical Publishing Co., 2019) Tiwari, R.; Mal, S.S.; Dutta, S.
    In present work, Keggin-type commercial heteropoly acids have been employed as efficient solid acid catalysts in the acetalization of biomass-derived furfural with ethylene glycol. The reaction was optimized on parameters such as the type and loading of catalyst, duration of reaction and the relative ratio of reagents. The reaction was scaled up and the cyclic acetal 2-(furan-2-yl)-1,3-dioxolane was isolated in 92 % yield within 4 h using only 2 wt % of phosphotungstic acid in refluxing benzene. © 2019 Chemical Publishing Co.. All rights reserved.
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    Efficient Preparation of Alkyl Benzoates by Heteropolyacid-Catalysed Esterification of Benzoic Acid under Solvent-Free Condition
    (Wiley-Blackwell, 2019) Tiwari, R.; Rahman, A.; Bhat, N.S.; Onkarappa, S.B.; Mal, S.S.; Dutta, S.
    This study reports a high-yielding, solvent-free, and scalable synthesis of alkyl benzoates from benzoic acid and its derivatives using heteropolyacids (HPA) as efficient and recyclable acid catalysts. The alkyl benzoates were obtained in excellent isolated yields (>85%) within 4 h at 120 °C using 1.5 equivalent of the alcohol reagent and only 0.4 mol% of the phosphotungstic acid (PTA) catalyst. The PTA catalyst was conveniently recovered and reused for three consecutive cycles without significant loss in mass or activity. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim