制备参数对Au/TiO_2催化剂上CO低温氧化性能的影响

Effect of Preparation Parameters on the CO Low-Temperature Oxidation Performance of Au/TiO_2 Catalysts

以溶胶-凝胶法制备TiO2载体,用沉积-沉淀法制备出一系列负载型Au/TiO2。系统考察了焙烧温度、金的负载量、反应液pH值、沉淀剂种类以及Cl-存在与否等制备参数对催化剂活性的影响。以室温下CO的催化氧化为探针反应,确定催化剂的最适宜制备参数,并对优化的质量分数为1.0%的Au/TiO2催化剂进行了活性稳定性测试。结果表明:Au/TiO2的最适宜焙烧温度是200～350℃;反应液的最适宜pH值为9;最适宜沉淀剂是NaOH;金的负载量(质量分数,下同)在0.5%～5.0%范围内时,金含量越高,催化剂活性和热稳定性越好。大量Cl-的存在能导致催化剂活性的显著下降。对优化的Au/TiO2催化剂在室温下催化氧化不同浓度的CO进行循环测试,经历3次循环,连续反应2 160 min后,CO的转化率仍为100%。

The support TiO2 and its supported catalysts Au/TiO2 were synthesized by sol-gel and deposition-precipitation method,respectively.The effect of several preparation parameters on the activity of the catalysts,such as calcination temperature,gold loading,pH value of reaction solution,kinds of precipitation reagents and presence or absence of Cl-ions,were investigated.The preparation parameters were optimized by using ambient CO oxidation as probe reaction.In addition,the thermal stability of the optimized catalyst 1.0% Au/TiO2 was also investigated.It is confirmed that the optimal calcination temperature is between 200—350 ℃;the best pH value and precipitation reagent are 9 and NaOH,respectively;when the gold loading is in the range of 0.5%—5.0%,the higher gold contents the better catalytic activity and the higher thermal stability.The presence of Cl-ions leads to an obvious decrease of the catalytic activity of Au/TiO2.The results of circular tests using different concentration of CO on the optimized Au/TiO2 catalysts showed that the CO conversion was always 100% at ambient temperature even after undergoing three cycles and a continuous reaction of 2 160 min.