负载型Keggin杂多酸催化糠醛液相氧化制备顺酐

用不同比例的四水合钼酸铵、偏钒酸铵、钨酸、草酸和磷酸等合成了4种Keggin杂多酸,并以SiO_2为载体,采用浸渍法制备了负载型的Keggin杂多酸催化剂。采用红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)和程序升温脱附(NH_3-TPD)等手段对催化剂进行表征。以合成的负载型杂多酸为催化剂,H_2O_2为氧化剂,二氯乙烷为溶剂,研究了催化剂催化糠醛液相氧化制备顺酐的性能,考察了催化剂种类和用量,溶剂、氧化剂用量,反应温度和反应时间对糠醛转化率和顺酐收率的影响。结果表明,以MoWP/SiO_2为催化剂,催化反应性能较好,较佳的工艺条件为反应温度60℃,反应时间3 h,催化剂与糠醛的质量比为0.09,二氯乙烷和糠醛物质的量之比为3,H_2O_2和糠醛物质的量之比为2.5,在此条件下糠醛的转化率为82.33%,顺酐的收率和选择性分别可达78.51%和95.36%。催化剂在使用5次后,顺酐的收率为64.18%,重复使用性能较好。

Performance of Supported Keggin-Type Heteropolyacid Catalyst in Liquid Phase Oxidation of Furfural to Maleic Anhydride

Four different Keggin-type heteropolyacids were synthesized using different proportions of ammonium molybdate tetrahydrate, ammonium metavanadate, tungstic acid, oxalic acid and phosphoric acid. These Keggin-type heteropolyacid catalysts were obtained using SiO2 as the support by impregnation method. The catalysts were characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope(SEM) and NH3 temperature programmed desorption(NH3-TPD). The performance of the SiO2-supported Keggin-type heteropolyacid catalyst in liquid phaseoxidation of furfural to maleic anhydride were investigated using H2O2 as oxidant, and dichloroethane as solvent. The effects of catalyst type and dosage, dosage of hydrogen peroxide and solvent, reaction time and reaction temperature on conversion of furfural and yield of maleic anhydride were investigated. The results showed that the catalytic performance was excellent using MoWP/SiO2 as the catalyst, and the optimal reaction conditions were as follows: the reaction temperature 60℃, the reaction time 3 h, the mass ratio of catalyst to furfural 0.09, the molar ratio of dichloroethane to furfural 3, and the molar ratio of H2O2 to furfural 2.5. Under these optimal reaction conditions, the conversion of furfural was 82.33%, the yield and the selectivity of maleic anhydride were 78.51% and 95.36%, respectively. The yield of maleic anhydride remained 64.18% over the catalyst reused 5 times.