钒铌氧化物催化剂催化氧化乙二醛制乙醛酸

对钒铌氧化物催化氧化乙二醛制乙醛酸进行研究，考察V₂O₅、Nb₂O₅及其混合物和工艺条件如乙二醛浓度、催化剂加入量、反应温度及反应时间对反应的影响。结果表明，HNO₃+NaNO₂+Nb₂O₅体系中，在乙二醛质量分数20%、催化剂用量1 g、反应温度318 K和反应时间2 h条件下，乙二醛转化率为82%，乙醛酸选择性为79%。以SiO₂为载体，采用共沉淀法制备Nb₂O₅/SiO₂催化剂，采用N₂等温吸附-脱附和XRD对催化剂进行表征，考察Nb₂O₅负载量和催化剂用量对催化氧化乙二醛合成乙醛酸的影响，并对催化剂稳定性进行研究。结果表明，Nb2O5能提高硝酸催化氧化乙二醛体系中乙二醛转化率和乙醛酸选择性，Nb₂O₅/SiO₂比纯Nb₂O₅的催化效果更好。HNO₃+NaNO₂+Nb₂O₅/SiO₂体系中，在催化剂用量5 g、活性组分Nb₂O₅负载质量分数18%和反应时间2 h条件下，乙二醛转化率为85%，乙醛酸选择性为87%，Nb₂O₅/SiO₂的稳定性和重复使用效果均良好。

V and Nb Oxides catalysts for catalytic oxidation of glyoxal to glyoxalic acid

Using Nb2O5 and V2O5 catalysts and the traditional nitric acid oxidation process, the effect of glyoxal concentration,catalyst dosage, reaction temperature and time on the oxidation of glyoxal to glyoxylic acid were investigated. The results showed that in the system of HNO3 ＋ NaNO2 ＋ Nb2O5 glyoxal conver- sion of 82% and the selectivity to glyoxalic acid of 79% were attained under the condition as follows ： glyoxal mass fraction 20%, Nb2O5 catalyst amount 1 g, reaction temperature 318 K, and reaction time 2 h. After that, Nb2OJSiO2 catalyst prepared by co-precipitation method was investigated in the liquid- phase oxidation of glyoxal to glyoxylic acid, and was characterized by N2 isothermal adsorption-desorption and XRD. The effect of Nb20s loadings, the dosage and stability of the catalyst on the oxidation of glyoxal to glyoxylic acid was studied. The results indicated that in the system of HNO3 ＋ NaNO2 ＋ Nbz Os/SiO2 the catalytic effect of Nb2O5/SiO2 for the oxidation of glyoxal to glyoxylic acid was better than Nb205 ,and The conversion of glyoxal and the selectivity to glyoxalic acid were 85% and 87% ,respectively under the condi- tion of Nb2O5/SiO2 catalyst dosage 5 g,active component Nb2O5 loading 18wt% and reaction time 2 h.The stability and the effect of repeated use of Nb2Os/SiO2 catalyst were good.