VPO/TiO2催化乳酸乙酯绿色合成丙酮酸乙酯

以V_2O_5和磷酸为原料,采用有机相法制备负载型钒磷氧(VPO)催化剂,并考察了其在乳酸乙酯氧化合成丙酮酸乙酯反应中的催化性能。结果表明,n(P)∶n(V)=1.4∶1.0,TiO_2为载体制备的VPO/TiO_2最好;合成丙酮酸乙酯的最适宜条件为:n(乙腈)∶n(H_2O_2)∶n(乳酸乙酯)=12∶2∶1,催化剂添加量为10%(以乳酸乙酯质量计),反应温度65℃,反应时间5 h;在该条件下,乳酸乙酯的转化率为85.24%,丙酮酸乙酯的收率可达80.96%。催化剂重复利用5次,丙酮酸乙酯收率仍稳定在70%以上。通过对催化剂进行XRD、FTIR、XPS和钒价态分析,提出了反应机理可能涉及以V4+和V5+动态变化为活性中心的氧化还原循环。

The Green Oxidation of Ethyl Lactate to Ethyl Pyruvate over VPO/TiO2 Catalyst

Supported vanadium-phosphorus oxide catalysts were prepared from vanadic oxide and phosphoric acid through organic solvent method, and their catalytic performance was investigated in the selective oxidation of ethyl lactate(EL) to ethyl pyruvate(EP). Results showed that the yield of ethyl pyruvate was 73.67% when the VPO catalyst supported by TiO2 with P/V molar ratio 1.40; Under the optimal conditions(n(acetonitrile):n(hydrogen peroxide):n(ethyl lactate)=12:2:1, the amount of VPO/TiO2 catalyst is 10%, 65 °C, 5 h), the conversion of ethyl lactate was 85.24%, and the yield of ethyl pyruvate was up to 80.96%. When the catalyst was reused 5 times, the yield of ethyl pyruvate was still more than 70%. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and determination of average valence state of vanadium, the reaction mechanism is expected to involve a redox cycle in which V4+ in combination with dynamic V5+ sites acts as the active centers.