Journal Articles
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Item Recent advances in the preparation of levulinic esters from biomass-derived furanic and levulinic chemical platforms using heteropoly acid (HPA) catalysts(Elsevier B.V., 2021) Bhat, N.S.; Mal, S.S.; Dutta, S.The esters of biomass-derived levulinic acid (LA) have several potential applications, including cleaner-burning fuel additive, green solvent, fragrance ingredient, and a renewable chemical intermediate for downstream value addition. The levulinic esters (LEs) can be prepared by the acid-catalyzed alcoholysis of the biomass-derived furanic and levulinic chemical platforms such as LA, furfuryl alcohol (FAL), 5-(hydroxymethyl)furfural (HMF), and angelica lactone (AGL). The acid-catalyzed deconstruction of carbohydrates in an alcoholic medium affords the one-pot preparation of LEs. Choosing the right catalyst is of paramount importance for synthesizing LEs from both the economic and environmental perspectives. In this regard, heteropoly acids (HPAs), a class of polyoxometalates (POMs) bearing protons as the counter cation, have found widespread applications as acid catalysts in various organic transformations. HPAs are blessed with conducive properties such as controlled Brønsted and Lewis acidity, high thermal stability, robust structural features, non-toxic nature, tunable solubility, and less corrosiveness. Over the past several years, HPAs have found extensive applications as efficient and environment-friendly catalysts in biorefinery operations, including the synthesis of LEs. At this juncture, it is imperative to ascertain the achievements in this field to date and re-evaluate the challenges. This review attempts to provide up-to-date information about the preparation of LEs using HPA-based catalysts, critically analyze the literature cited, draw conclusions, and propose future prospects. © 2021 Elsevier B.V.Item Recent Advances in the Value Addition of Biomass-Derived Levulinic Acid: A Review Focusing on its Chemical Reactivity Patterns(John Wiley and Sons Inc, 2021) Dutta, S.; Bhat, N.S.Levulinic acid (LA) is one of the most prominent biomass-derived chemical building blocks that can be transformed into specialty chemicals like fuels, solvents, monomers for polymers, plasticizers, surfactants, agrochemicals, and pharmaceuticals. Over the past three decades, an enormous amount of research data have been acquired on the preparation and downstream value addition of LA, and these works have been reviewed. However, considering the astonishing number of publications appearing every year on LA derivatives, the periodical review of recent works focusing on unique aspects of chemistry must be undertaken to critically evaluate the achievements to date, reassess the challenges, and recognize new opportunities. This review discusses the chemical-catalytic synthesis of various derivatives of LA by focusing on its functionalities and reactivity patterns. Recent literature on some crucial derivatives such as γ-valerolactone, 4,4’-diphenolic acid, and ethyl levulinate have been tabulated and discussed. The synthetic interconversion between various derivatives, mechanistic insights, critical analysis of the reaction parameters toward selective preparation of various derivatives, and their potential commercial applications have been elaborated using predominantly heterogeneous catalysts. A critical assessment of the relative advantages and shortcomings of the existing synthetic strategies for various derivatives of LA has been presented to enkindle fresh ideas. © 2021 Wiley-VCH GmbHItem Chemocatalytic value addition of glucose without carbon-carbon bond cleavage/formation reactions: an overview(Royal Society of Chemistry, 2022) Dutta, S.; Bhat, N.S.As the monomeric unit of the abundant biopolymer cellulose, glucose is considered a sustainable feedstock for producing carbon-based transportation fuels, chemicals, and polymers. The chemocatalytic value addition of glucose can be broadly classified into those involving C-C bond cleavage/formation reactions and those without. The C6 products obtained from glucose are particularly satisfying because their syntheses enjoy a 100% carbon economy. Although multiple derivatives of glucose retaining all six carbon atoms in their moiety are well-documented, they are somewhat dispersed in the literature and never delineated coherently from the perspective of their carbon skeleton. The glucose-derived chemical intermediates discussed in this review include polyols like sorbitol and sorbitan, diols like isosorbide, furanic compounds like 5-(hydroxymethyl)furfural, and carboxylic acids like gluconic acid. Recent advances in producing the intermediates mentioned above from glucose following chemocatalytic routes have been elaborated, and their derivative chemistry highlighted. This review aims to comprehensively understand the prospects and challenges associated with the catalytic synthesis of C6 molecules from glucose. This journal is © The Royal Society of ChemistryItem Catalytic synthesis of renewable p-xylene from biomass-derived 2,5-dimethylfuran: a mini review(Springer Science and Business Media Deutschland GmbH, 2023) Dutta, S.; Bhat, N.S.In this work, the renewable synthesis of p-xylene (PX) from biomass-derived carbohydrates has been reviewed. PX is a crucial chemical feedstock and an essential starting material of polyethylene terephthalate (PET). PX can be produced selectively by the Diels-Alder reaction between ethylene and 2,5-dimethylfuran (DMF) followed by catalytic dehydration of the oxanorbornene adduct. DMF is primarily produced by the catalytic hydrogenation of 5-(hydroxymethyl)furfural (HMF), a furanic intermediate produced by the acid-catalyzed hydrolysis/dehydration of biomass-derived hexoses. With ethylene being sourced by dehydrating bioethanol, PET can be made biorenewable in its entirety. The atom economy and carbon efficiency of converting glucose into PX have been calculated. The existing literature (both theoretical and experimental) on the catalytic production of PX from DMF and ethylene are summarized, and future directions on this research have been proposed. The effect of Brønsted and Lewis acidity, porosity, and surface area of the heterogeneous catalysts on the selectivity and yield of PX have been highlighted. In addition, the techno-economic analysis of renewable PET, its future prospects based on the petroleum market, and the possibility of a circular economy of PET using chemical and enzymatic recycling strategies have been discussed. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.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 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.Item Kinetics and regression analysis of phenanthrene adsorption on the nanocomposite of CaO and activated carbon: Characterization, regeneration, and mechanistic approach(Elsevier B.V., 2021) Aravind Kumar, J.; Krithiga, T.; Vijai Anand, K.; Sundararaman, S.; Karthick Raja Namasivamyam, S.; Annam Renita, A.A.; Hosseini-Bandegharaei, A.; Praveenkumar, T.R.; Manivasagan, M.; Bhat, N.S.; Dutta, S.In the present study, calcium oxide supported on activated carbon (CaO@AC) nanocomposite was synthesized using Basil leaf extract as a promoter and used to remove phenanthrene, an environmental pollutant, from aqueous solution. The activated carbon (AC) was prepared by the carbonization of Palm shells under pyrolytic conditions. The CaO@AC nanocomposite was characterized by FTIR, SEM-EDX, BET, and PXRD. The characterized CaO@AC nanocomposite was employed as an adsorbent for selective removal of phenanthrene from wastewater, maintaining the optimized conditions at initial phenanthrene concentration (5 mg/L), catalyst dosage (1 g), temperature (30 °C), and pH (7.6) for all batches. The adsorption isotherm and the kinetic studies for regression analysis were well fitted for the Freundlich model (R2 = 0.9956) and non-linear Pseudo (II order) mechanism (R2 = 0.9942). The results showed that the type IV linear form of pseudo-II order kinetic expression was inadequate for the kinetic rate parameters compared to the type I - III models. The CaO@AC was demonstrated as an inexpensive, scalable, recyclable, and eco-friendly adsorbent material for removing phenanthrene from wastewater. © 2021 Elsevier B.V.