Ru/MgO catalyzed oxidation of 5-hydroxymethylfurfural to prepare high-purity 2,5-furandicarboxylic acid under base-free conditions
The support MgO was prepared using a calcination method,followed by the preparation of Ru/MgO catalysts through an impregnation-reduction method.Characterization analyses of the catalysts were conducted,and the results indicated that the specific surface area and alkalinity of MgO increased after loaded Ru.Ru,serving as the active center of the catalyst,significantly enhanced the catalytic activity of the Ru/MgO catalyst in the selective oxidation of 5-hydroxymethylfurfural(HMF)under base-free conditions.After loading Ru on MgO,the turnover frequency(TOF)value increased from 2.82 × 10-4 h-1 to 5.98 × 10-1 h-1.Ru/MgO catalyst under optimal reaction conditions,the conversion rate of HMF reached 100%,and the yield of 2,5-furandicarboxylic acid(FDCA)was 95.7%,and it can maintained high activity after three cycles of reuse,with the active component Ru not leaching significantly and only a minimal amount of MgO dissolving.Semi-preparative liquid chromatography was employed to achieve the green separation of the product,finally obtaining FDCA powder with a purity greater than 99%,thereby avoiding the addition of concentrated hydrochloric acid to separate FDCA.This preparation method provides a reference for the efficient synthesis of FDCA from HMF in an base-free system.