杂多酸盐在Raney Ni和Raney Co表面上的状态

Valence States of Cu_(3/2)PMo_(12)O_(40) on the Surface of Raney Nickel and Raney Cobalt Catalysts

采用XPS表面分析技术研究了Cu3/2PMo12O40改性Raney Ni和Raney Co的表面状态,结果表明,RaneyNi和Raney Co表面上的Cu3/2PMo12O40分子中的Cu2+和Mo6+发生了很大变化,Cu2+被还原为Cu0,而Mo6+被部分还原为Mo5+和Mo4+.这些变化可归因于Raney Ni和Raney Co在制备过程中表面吸附的活泼氢所致.由于Raney Ni表面吸附的氢比Raney Co表面吸附的氢的活性高,使得Raney Ni表面的Mo6+被还原到Mo5+和Mo4+的量多.混合价态Mo的存在提高了羰基在催化剂表面吸附和活化的能力,同时Cu0的存在有助于羰基的加氢反应.所以,混合价态的Mo和Cu0对羰基加氢起着协同的作用.

The states of Cu3/2PMo12O40, which was used as a modifier for Raney nickel and Raney cobalt, were investigated by XPS technique. It was found that valence states of Cu2+ and Mo6+ were greatly changed, i.e. Cu2+ was reduced to Cu-0 while Mo6+ was partially reduced to Mo5+ and Mo-4. These changes were due to the presence of active hydrogen adsorbed onto the surface of Raney nickel and Raney cobalt catalysts. Raney nickel contained less low oxidation state Mo than Raney cobalt, which was probably due to the different activity of adsorbed hydrogen species on the Raney nickel surface and Raney cobalt surface. The presence of Cu was beneficial to the hydrogenation of carbonyl. The existence of Mo improved the adsorption and activation of carbonyl. In another word, the presence of Cu and Mo complemented each other in the hydrogenation of carbonyl.