Hydroxyl-Rich Deep Eutectic Solvents Assistant Synthesis of VPO and Its Application in Selective Oxidation of n-Butane

Deep eutectic solvents (DESs) consisting of choline chloride (ChCl) and polyols (Ethylene glycol (EG), 1,4-Butanediol (BDO), Glycerol (GL), and Xylitol (XYL)) as a green and effective promoter assisting the synthesis of vanadium phosphorus oxide (VPO) were innovatively proposed and investigated in detail for the selective oxidation of n-butane to maleic anhydride (MA). The catalytic results showed that the performance of VPO catalysts was improved significantly with the addition of polyols DESs. A combination of techniques including SEM, TEM, XRD, FT-IR, Raman, XPS, and TG-DTA were employed to investigate the effect of DES on the structure of VPO. We correlated the structure of the catalysts with catalytic performance and found that the n-butane conversion was positively correlated with the intensity ratio of I-(020)/I((204))for catalysts, and the MA selectivity of VPO catalysts was negatively correlated with the vanadium average oxidation state on the catalyst surface.