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Microwave-assisted synthesis of 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) in the presence of tungsten disulfide has been studied for the first time. The catalyst was synthesized at 600 °C in a tubular furnace using elemental tungsten and sulfur to obtain multilayered flakes/sheets of WS 2 . The textural and morphological properties of the synthesized WS 2 catalyst were characterized using XRD, Raman, SEM, SEM-EDX, TEM, TEM-EDX, HR-TEM, SAED, and surface area analyzer, which showed the formation of multiple two-dimensional layers of sheet/flake-type structure. Activity test of the catalyst in a microwave-assisted reaction resulted in 100% fructose conversion and 62% EMF yield for the experiment performed at 160 °C temperature in 15 min. A qualitative analysis of the product samples using GC-MS spectrometry showed the presence of several intermediates and byproducts based on which a mechanistic insight into the production of EMF from fructose has been proposed.

A Keggin silicotungstic acid (HPS) catalyst was heterogenized by loading (10−40 wt %) over zirconia support, and the resulting catalysts were named ESZN-1 (10 wt %), ESZN-2 (20 wt %), ESZN-3 (30 wt %), and ESZN-4 (40 wt %). After that, synthesized catalysts were characterized using several tools and techniques which revealed that the Keggin structure of the parent HPS catalyst remained intact after heterogenization. Eventually, synthesized catalyst performance evaluation tests were performed for the production of ethyl levulinate from biomass-derived levulinic acid under microwave heating irradiations. Under optimum operating conditions, more than 90% LA conversion with 100% EL selectivity was obtained at a 110 °C temperature in 30 min in the presence of 100 mg of ESZN-4 in a solution containing levulinic acid and ethanol in a 1:43 ratio. A kinetic study on LA conversion in the presence of the ESZN-4 catalyst revealed a pseudo-first-order mechanism for ethyl levulinate synthesis.

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