Faculty Publications
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Item Efficient and Scalable Production of Alkyl Levulinates from Cellulose-Derived Levulinic Acid Using Heteropolyacid Catalysts(Wiley-Blackwell info@wiley.com, 2019) Onkarappa, S.B.; Javoor, M.; Mal, S.S.; Dutta, S.This work reports a straightforward and scalable synthesis of a series of alkyl levulinates from cellulose-derived levulinic acid and alkyl alcohols using commercially available heteropolyacid catalysts under homegenous conditions. The reaction was optimized on parameters such as temperature, molar ratio of reagents, type and loading of catalyst. The solvent-free reactions afforded alkyl levulinates in high isolated yields (>85%) using only slight excess of alcohols and 10 wt% of catalyst at 120 °C in 6 h. Further, the catalysts were successfully recycled for three consecutive cycles without significant loss in activity. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem High-Yielding Synthesis of 5-(alkoxymethyl)furfurals from Biomass-Derived 5-(halomethyl)furfural (X=Cl, Br)(Wiley-Blackwell info@wiley.com, 2019) Onkarappa, S.B.; Dutta, S.A series of 5-(alkoxymethyl)furfurals (AMFs) have been synthesized in excellent isolated yields (>90%) by reacting biomass-derived 5-(chloromethyl)furfural (CMF) or 5-(bromomethyl)furfural (BMF) with monohydric alkyl alcohols (methanol to 1-butanol) at slightly elevated temperatures (RT-50 °C) and short reaction time (3 h). The modified work-up procedure minimizes side reactions while simplifying the isolation and purification of AMFs. Although higher primary alcohols like 1-pentanol and 1-hexanol and secondary alcohol like 2-propanol were found to be less reactive, use of N,N-diisopropylethylamine (DIPEA) as a base additive afforded AMFs in excellent yields within 6 h at 65 °C using only slight excess of the alcohol (1.2 eq.) reagent. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Phase Transfer Catalyst Assisted One-Pot Synthesis of 5-(Chloromethyl)furfural from Biomass-Derived Carbohydrates in a Biphasic Batch Reactor(Wiley-Blackwell info@wiley.com, 2019) Onkarappa, S.B.; Dutta, S.5-(Chloromethyl)furfural (CMF), a bio-renewable chemical building block, has been produced in good isolated yields from biomass-derived carbohydrates within a closed aqueous HCl-1,2-dichloroethane biphasic reactor in the presence of benzyltributylammonium chloride (BTBAC) as a phase transfer catalyst (PTC). The solvent-economic, one-pot strategy afforded CMF in 73% isolated yield (90 °C, 3 h) from sucrose with a combined yield of 84% for CMF and levulinic acid. The process was optimized on temperature, duration, solvent, type, and loading of PTC. Use of BTBAC led to nearly 10% increase in yield of CMF for all substrates when compared to control reactions. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem 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, WeinheimItem Catalytic conversion of biomass-derived carbohydrates into levulinic acid assisted by a cationic surface active agent(John Wiley and Sons Inc, 2019) Onkarappa, S.B.; Bhat, N.S.; Parashuram, D.; Dutta, S.Levulinic acid (LA), a bio-renewable chemical building block, has been produced in good isolated yields by treating biomass-derived carbohydrates with aqueous hydrochloric acid in the presence of quaternary ammonium salts as cationic surface-active agent (SAA). Under optimized conditions (120 °C, 3 h, 20.2% HCl), the one-pot process afforded LA in 80% isolated yield from glucose using only 5.77mol% (10 wt%) of benzyl-tributylammonium chloride (BTBAC) at the SAA. The control reaction (no BTBAC) provided LA in only 64% yield from glucose under identical conditions. The process was optimized on the reaction temperature, loading of BTBAC, and the concentration of HCl. The use of BTBAC led to a nearly 8–17% increase in yield of LA (compared to the control reaction) for all the carbohydrates studied. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.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 Preparation of alkyl levulinates from biomass-derived 5-(halomethyl)furfural (X = Cl, Br), furfuryl alcohol, and angelica lactone using silica-supported perchloric acid as a heterogeneous acid catalyst(Springer Science and Business Media Deutschland GmbH, 2020) Onkarappa, S.B.; Bhat, N.S.; Dutta, S.This work reports the synthesis of a series of alkyl levulinates from biomass-derived 5-(halomethyl)furfural (X = Cl, Br), furfuryl alcohol, and angelica lactone using silica-supported perchloric acid (HClO4-SiO2) as a heterogeneous acid catalyst. The solvent-free, one-pot preparation afforded levulinate esters in excellent isolated yields (> 84%). The reactions were performed at 120 °C for 6 h in a batch-type glass pressure reactor using XMF and furfuryl alcohol in presence of excess of the alcohol reagent and 4 wt.% of the HClO4-SiO2 catalyst (0.028 mmol HClO4). Furthermore, the reaction protocol was extended for the synthesis of ALs starting with angelica lactone at 90 °C for 2 h in a round-bottomed flask by using excess alcohol and 4 wt.% of the HClO4-SiO2 catalyst. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.