2. Thesis and Dissertations

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    Production of 5 - (Halomethyl) Furfurals from Cellulosic Biomass and their Synthetic Upgrading into Renewable Chemicals
    (National Institute of Technology Karnataka, Surathkal, 2020) Sharath, B. O.; Dutta, Saikat
    The transportation fuels and most of the bulk and fine chemicals are primarily sourced from crude oil. However, the excessive use of crude oil has depleted the reserves, created a disparity between the demand and supply, and degraded the environment. In search of a renewable and preferably carbon-neutral source, biomass has found by many as a commercially-feasible replacement for fossilized carbon. The chemocatalytic valorization of biomass is of particular interest since they are fast, biomass agnostic, selective, and can potentially be integrated into the existing infrastructure. A major challenge in the chemocatalytic value addition of biomass is to develop a new generation of robust, selective, inexpensive, and environment-friendly catalysts that can selectively deconstruct the biopolymers. In this regard, the acidcatalyzed depolymerization and dehydration of biomass-derived carbohydrates (e.g., cellulose) into furanics is an elegant way of removing excessive functionalities from the carbohydrate. Biomass-derived 5-(hydroxymethyl)furfural (HMF), 5- (chloromethyl)furfural (CMF), furfural and levulinic acid (LA) have been used as renewable chemical building blocks for further value addition into fuels and specialty chemicals. In this thesis work, an improved synthesis of CMF and LA have been reported using aqueous HCl as the acid catalyst in the presence of quaternary ammonium chloride as a surface-active agent (SAA). The SAA afforded noticeably higher yields of CMF and LA compared to the control reactions. The reactions were optimized on various reaction parameters such as temperature, duration, loading of the substrate, and the loading of SAA. The SAA was successfully recovered and recycled. LA was converted into alkyl levulinates, a potential diesel additive and a renewable solvent, in the presence of phosphotungstic acid as an environment-friendly and recyclable catalyst. Alkyl levulinates were also prepared by the alcoholysis of CMF and furfuryl alcohol using HClO4-SiO2 as an inexpensive heterogeneous catalyst. A scalable and high-yielding preparation of 5-(alkoxymethyl)furfural, a novel fuel oxygenate, from CMF has also been reported.
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    Application of Polyoxometalates as Efficient and Green Catalyst for Catalytic Upgrading of Cellulosic Biomass
    (National Institute of Technology Karnataka, Surathkal, 2020) Tiwari, Ritesh; Mal, Sib Shankar; Dutta, Saikat
    In recent years, the research on the sustainable production of energy, transportation fuels, and materials has been incentivized. Non-food and preferably waste biomass has been identified as a commercially-feasible renewable alternative to fossilized carbons for producing fuels and chemicals. The chemocatalytic value addition of biomass, where the oxygen-rich biopolymers are selectively deconstructed into functionally-rich small organic molecules, is of particular interest. A new generation of robust, inexpensive, and environment-friendly catalysts are crucial for the chemocatalytic route. Over the past years, heteropolyacids (HPAs) are increasingly being used as a catalyst in the chemistry of renewables and biomass value addition. HPAs have been used in the hydrolysis and dehydration of pentose and hexose sugars in biomass into furfural and 5- (hydroxymethyl)furfural (HMF), respectively. Furfural, levulinic acid, and HMF act as renewable chemical building blocks that can be converted into commodity chemicals and materials via chemical or catalytic transformations. The proposed work is intended to explore the efficiency of various homogenous and heterogeneous HPA catalysts for the catalytic upgrading of biomass-derived chemical intermediates into value-added chemicals. HPA-based homogeneous and heterogeneous catalysts were used for the acetalization, esterification, and Baeyer-Villiger oxidation reactions of various biomass-derived chemical intermediates. The reaction conditions were optimized on various parameters such as temperature, duration, loading of reactant, and loading of catalyst. The cyclic acetals of biomass-derived furfural were prepared in high isolated yields in refluxing benzene in the presence of the phosphotungstic acid (PTA) catalyst. The PTA catalyst was successfully recovered and reused several times without significant loss in mass or activity. The esterification of saturated and unsaturated free fatty acids such as oleic acid and stearic acid were conducted in the presence of PTA catalyst as an efficient and recyclable catalyst. 2-Furanone was prepared by the selective oxidation of furfural using hydrogen peroxide as an inexpensive oxidant and PTA supported on ammonium zeolites as the catalyst. A scalable and high yielding preparation of alkyl benzoates and alkyl 2-furoates has also been reported.