H_2,CO,O_2在还原态Ni-W/Al_2O_3催化剂上的化学吸附研究

CHEMISORPTION OF H_2、CO、O_2 ON REDUCED Ni-W/Al_2O_3 CATALYST

本文应用容量吸附方法研究了 H_2,CO,O_2在还原态 Ni-W/Al_2O_3催化剂上的化学吸附。根据实验结果得到,Ni 在 W/Al_2O_3上可以处于两种状态,在低钨担载量的催化剂上,部分 Ni 直接担载在 Al_2O_3上;而在高钨担载量时,Ni 中心和 W 中心发生了较强的化学作用,生成 Ni-W 相互作用相。与担载在 Ni-Al_2O_3上的 Ni 中心相比较,H_2,CO,O_2在 Ni-W 作用相上的吸附能力大大降低,同时由 XRD 的结果还进一步得到 Ni-W 作用相的生成提高了 WO_3在Al_2O_3上的分散度。文中还对 CO,O_2的共吸附行为进行了考察和讨论。

Chemisorptions of hydrogen,carbon monoxide,and oxygen on reduced Ni- W/Al_2O_3 catalysts were studied by volumetric method.With increasing tungsten loading, the uptake of hydrogen and CO decreased gradually,while the uptake of oxygen showed a volcanic curve with its maximum at 3.8% NiO-26.7% WO_3/Al_2O_3.For a series of Ni-W/ Al_2O_3 catalysts with constant WO_3 loading of 22.9%,the amount of hydrogen,CO and oxyen chemisorption increased with increasing Ni content.These results were discussed in compari- son with those obtained on W/Al_2O_3.It is suggested that Ni could exist in two states in Ni- W/Al_2O_3 catalysts,In low W content catalysts,Ni might be bound directly to Al_2O_3 to form individual Ni centers,while in high W content catalyst,Ni interacted with W sites to form an interaction phase.Formation of the Ni-W interaction phase enhances the dispersion of WO_3 on Al_2O_3 as observed by XRD.The Ni-W interaction phase adsorbs less bydrogen and CO than the individual Ni site,but more oxygen than the individual W site.