Au负载OMS-2催化剂的制备及其低温催化氧化性能

通过前掺杂法(QI),浸渍法(IM)和沉积-沉淀法(DP)3种方法制备了Au负载氧化锰八面体分子筛(OMS-2)Au/OMS-2催化剂,研究了制备方法和制备条件对其催化氧化CO活性的影响.采用X射线衍射(XRD)和BET比表面积测定等技术对所制样品进行表征.结果表明,沉积-沉淀法制备的Au/OMS-2-DP催化剂活性明显高于前掺杂法和浸渍法制备的催化剂,这与Au/OMS-2-DP催化剂比表面积较大和负载Au颗粒较小有关.制备条件(沉淀剂种类、制备溶液pH、Au负载量和催化剂焙烧温度)明显影响Au/OMS-2-DP催化剂的催化活性.对于各种不同的沉淀剂,以KOH为沉淀剂制备的催化剂活性最高,这可能与其无钝化作用,而且形成的Au颗粒较小有关;制备溶液的为最佳,当pH值过高或过低容易导致Au颗粒的聚集和Au沉淀量较少;XRD结果表明,当Au负载量为5wt%催化剂和催化剂焙烧为300℃时,所制备的催化剂颗粒最小,所得的催化剂活性最高.最佳条件制备的Au/OMS-2-DP催化剂活性较好,CO完全转化(100%)的温度为67℃.

Low-temperature CO oxidation over Au-doped OMS-2 catalysts: preparation and catalytic activity

Au/OMS-2 catalysts were prepared by pre-incorporation(QI),typical wet impregnation(IM) and deposition-precipitation(DP) methods.The influences of prepared methods and conditions on the catalytic activity of CO oxidation were studied.The samples were characterized by X-ray diffraction(XRD) and Brunaner-Emmett-Teller(BET).As compared with pre-incorporation and typical wet impregnation methods,Au/OMS-2-DP prepared from deposition-precipitation(DP) method revealed the highest activity,due to the largest surface area and the smallest Au particle size.A study was conducted on the effects of different preparation conditions(i.e.,precipitating agents,pH of solution,Au loading and calcinations temperature) on the catalytic oxidation of CO over Au/OMS-2-DP.Effects of precipitating agents on catalytic activity were obvious.The best catalytic activity was shown by the Au/OMS-2-DP catalyst prepared with KOH as a precipitating agent,which could be explained in terms of the smallest Au particle size.A pH of 9 generated greater amounts of Au loading and smaller Au particles on OMS-2 than other pH value.The sample calcined at 300℃ showed the highest activity,which may be due to the sample’s calcined at 200℃ inability to decompose completely to metallic gold while the sample calcined at 400℃ had larger particles of gold deposited on the support.Au/OMS-2-DP prepared from a gold solution with KOH as a precipitating agent,pH of 9,Au loading at 5 wt%,and a calcination temperature of 300℃ provides the optimum catalytic activity for CO oxidation,i.e.100% CO conversion at 67℃.