Zn(Al)O复合氧化物负载Au催化剂催化氧化甘油制备1,3-二羟基丙酮

Zn(Al)O composite oxides supported Au catalysts for selective oxidation of glycerol to 1,3-dihydroxyacetone

以尿素为沉淀剂,采用均匀沉积沉淀法制备了Zn(Al)O复合氧化物负载Au催化剂,并用于无碱条件下催化氧化甘油制备1,3-二羟基丙酮(DHA)反应,值得注意的是随着载体中Zn/Al摩尔比的不同,负载Au催化剂的催化活性和产物DHA的选择性呈现明显差距。结合X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电镜(TEM)、CO吸附傅里叶变换红外光谱(CO吸附FTIR)等表征手段,发现载体Zn(Al)O复合氧化物中Zn/Al摩尔比会影响表面氧物种的含量并进一步会影响催化剂的催化活性和选择性。当Zn/Al摩尔比为7∶1、反应温度为80℃、氧气压力为10bar、反应2h时获得最佳的甘油转化率(58.5%)和DHA的选择性(95.3%)。同时,还考察了反应温度、反应时间、反应压力及载体的焙烧温度对催化性能的影响,并发现反应条件对催化剂的催化活性和选择性均有不同程度的影响。此外,以Au/Zn(Al)O-7∶1催化剂为基准考察了催化剂的稳定性,并通过表征手段分析了催化剂失活的主要原因。

A series of Zn(Al)O composite oxides supported Au catalysts were prepared by depositionprecipitation with urea.Interestingly,the catalysts with varied Zn/Al molar ratios showed different catalytic performance for selective catalytic oxidation of glycerol to 1,3-dihydroxyacetone(DHA)without base.The physicochemical properties of the catalysts were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),CO adsorbed Fourier transform infrared(FTIR)spectroscopy.The results showed that the molar ratio of Zn/Al in the Zn(Al)O composite metal oxide affected the content of the reactive oxygen species and in turn the catalytic activity of glycerol oxidation.When the molar ratio of Cu/Al reached 7∶1,the supported catalyst showed the best performance,i.e.the conversion of glycerol and product selectivity of DHA reached 58.5%and 95.3%respectively with the initial O2 pressure of 10bar,at 80℃for 2h.Then,the Au/Zn(Al)O-7∶1 catalyst was used to investigate the effects of reaction temperature,reaction time,reaction pressure and calcination temperature of supports on the catalytic oxidation of glycerol and the selectivity for DHA.Additionally,we also studied the stability of the Au/Zn(Al)O-7∶1 catalyst and discussed the deactivation reasons.