W/TiO_2催化剂表面上钨的分散性

Dispersibility of W Species on the Surface of W/TiO_2 Catalysts

采用浸渍法和干混法制备了以TiO2为载体负载WO3的加氢精制催化剂,利用XRD分析了样品表面上钨的分散性。结果表明,通过浸渍法处理含低、中、高钨质量分数的催化剂,钨在载体TiO2表面上自发分散使晶相钨物种消失;而通过干混法热处理的催化剂,只有含钨质量分数的催化剂中钨自发分散使晶相钨物种消失,而含钨质量分数中、高的催化剂,其表面上均仍保留晶相钨物种,这就说明浸渍法制备的W/TiO2催化剂中钨的分散较好,而干混法制备的W/TiO2催化剂钨较难分散。对浸渍法与干混法制备的W/TiO2催化剂进行氨溶处理,可以使含低、中、高钨质量分数的催化剂上所有的晶相钨物种消失,即氨溶处理溶解掉部分表面钨物种,改善了钨物种在载体表面上的分散性。

The dispersibility of WO3 or AMT on the surface of W/TiO2 was determined by X-ray diffraction (XRD). The results show that the XRD peaks of WO3 crystalline disappear when the W loading is low, medium or high in the W/TiO2 catalysts prepared by immersion method. While the catalysts prepared by mechanically mixing and heating method, the XRD peaks of WO3 crystalline disappear if the W loading is low in W/TiO2 catalysts and the XRD peaks of W species are observed when the W loading is high. The dispersibility of W species on the surface of TiO2 catalysts prepared by immersion method is better than that of mechanically mixing and heating method when their W contents are the same. Ammonia can extract W crystalline and a portion of non-active dispersed W in W/TiO2 catalysts.