Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
23 results
Search Results
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 Nanocatalysis for renewable aromatics(wiley, 2022) Dutta, S.; Bhat, N.S.; Anchan, H.N.Chemocatalytic transformation of biomass feedstock, especially the non-food, inexpensive, and abundant terrestrial lignocellulose into fuels and chemicals, has multifaceted benefits, including the development of a sustainable economy and a cleaner environment. Aromatic compounds have a ubiquitous presence in the chemical industry. They must be accessed from biomass to supplant the same from fossilized resources. Several pathways have been developed to convert the major biomass components into aromatic hydrocarbons and functionalized aromatic compounds by catalytic methods. In this regard, heterogeneous nanocatalysts (NCs) have received particular attention since they have many superior properties, such as better selectivity, faster kinetics, and the requirement of lower loading due to higher activity, compared to the traditional heterogeneous catalysts of the micrometer scale. Polymeric carbohydrates like cellulose can be converted into furanic compounds first, which were then converted to benzene derivatives. The lignin fraction can be deconstructed into phenolics or further reduced into mononuclear aromatic hydrocarbons. Direct conversion of biomass into bio-oil containing aromatics is an alternative option. This chapter attempts to divulge the major pathways available to convert various biomass components into aromatic compounds emphasizing on the use of NCs for the chemical transformations. The accomplishments made to date and the challenges ahead are also emphasized. © 2023 John Wiley & Sons Ltd.Item 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.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 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, Weinheim
- «
- 1 (current)
- 2
- 3
- »