Selective Oxidation Of 5-hydroxymethylfurfural To 2,5-diformylfuran Over Mg Doped OMS-2 Nanorods

The problems of insufficient reserves,non-renewable and easy pollution of traditional fossil resources conflict with the sustainable development strategy.Biomass resources can make up for these deficiencies.5-hydroxymethylfurfural(HMF),as an important platform compound,can be transformed into high value-added chemicals.2,5-diformylfuran(DFF),an oxidation products of HMF,can be used as an intermediate to synthesize fine chemicals such as biomedicine and antibacterial agent.The reported catalytic systems for HMF oxidation to DFF have many defects,such as low catalytic efficiency and poor catalyst stability.In this paper,Mg doped manganese oxide catalyst was prepared by simple precipitation method at room temperature.The composition,crystal structure,formation mechanism and catalytic oxidation mechanism of the catalyst were investigated by a series of characterization methods such as XRD、HRTEM、TG-DTA、XPS,and H2-TPR.Ultrafine rod-shaped molecular sieve catalyst doped with Mg(Mg-OMS-2)was prepared.Mg2+can be doped into the framework of MnO6,which was obtained by the redox reaction of KMnO4 and H2O23 during the formation of single crystal.Mg-OMS-2 with 2×2 tunnel structure was synthesized by single crystal ordered arrangement in the subsequent stirring process.The ratio of H2O2/KMnO4 and Mg2+ doping ratio in the preparation process could affect the crystal type and particle size,and urea was beneficial to the synthesis of smaller particles.The conversion of HMF was 91.3%and the selectivity of DFF was 99.9%in 110 mmol·L-1 HMF solution under 0.9 MPa O2 pressure for 1 h at 120℃.After centrifugation,washing,drying and calcination,the activity of the regenerated catalyst did not decrease significantly.It showed that Mg-OMS-2 has excellent stability and reproducibility.The results of experiment,XPS,and TPR show that the oxidation of HMF catalyzed by Mg-OMS-2 follows the oxidation-reduction cycle mechanism of Mn4+/Mn3+/Mn2+.While maintaining the HMF conversion rate of 60%,the influence of O2 pressure,HMF and H2O concentration,reaction temperature on the catalytic activity were studied.The kinetic equation was r=3.2(CHMF)0.187(PO2)0.618.The activation energy was 44.0 kJ/mol by fitting Arrhenius curve.