微乳法制备的负载型铑催化剂粒子大小对CO加氢反应性能的影响

Effect of Rhodium Particle Size in Rh/SiO_2 Catalyst Prepared by Microemulsion Method on Reaction Performance of CO Hydrogenation

利用微乳法,通过调节W0值（水与表面活性剂的摩尔比）, 实现了负载型Rh/SiO2催化剂中金属铑粒子大小的可控合成. 该催化剂具有核壳结构,其中铑为核, SiO2为壳. TEM表征及反应评价结果显示金属铑的粒子大小（1.8～5.0 nm）对CO加氢反应性能具有显著的影响. 当粒子大小为3 nm时, CO加氢反应活性存在最小值; 随着粒子的进一步增大, CO加氢反应活性上升. 与浸渍法制备的催化剂相比,微乳法制备的催化剂粒子大小均一; 对负载量相同、平均粒子大小相同的两种催化剂,微乳法合成的Rh/SiO2催化剂对CO加氢反应具有较高的催化活性.

Controllable synthesis of the silica-supported rhodium catalyst with uniform particle size has been achieved through microemulsion technique by manipulating the W0 value （molar ratio of water to surfactant in the precursor）. The catalyst shows a core-shell morphology, in which rhodium is encapsulated by a silica shell. The characterization of the catalyst morphology by TEM and the catalytic performance of the catalyst for CO hydrogenation indicated significant influence of the rhodium particle size. There was a minimum value of the CO conversion over the catalyst with the average rhodium particle size of 3 nm in the range of 1.8-5.0 nm. With increasing the rhodium particle size from 3 to 5.0 nm, the reactivity increased. Compared with the Rh/SiO2 catalyst prepared by the conventional impregnation method, the present catalyst had more uniform distribution of rhodium particle size and showed superior catalytic activity for CO hydrogenation, when the catalyst samples had the same loading and average particle size.