Microwave-assisted selective oxidation of sugars to carboxylic acids derivatives in water over zinc-vanadium mixed oxide
Résumé
Zinc-vanadium (Zn3V2O8) nanostructured mixed oxide (ZVO) was synthesized by precipitation method. The ZVO was characterized by TGA, XRD, N2-adsorption/desorption, NH3-TPD, XPS, SEM, and TEM. XPS and NH3-TPD analyses revealed that it was a Zn/V-based strong oxidant catalyst, with a mixture of both Lewis acid and Brønsted surface acid sites. The ZVO was found to be an efficient catalyst for selective oxidation of glucose and xylose to galacturonic and glycolic acid, respectively, under microwave activation. Response surface methodology was applied to find the optimal operating conditions for maximization of the sugar conversion and selectivity. There was a 60% selectivity of galacturonic acid and 46% of glycolic acid using glucose and xylose, respectively. The ability to regenerate the ZVO was assessed by determining the change in the reaction indices in successive reaction–regeneration cycles. The causes of performance activation were ascertained, characterizing the regenerated ZVO by XRD, SEM, and NH3-TPD.
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