2011 年 32 巻 7 号 p. 439-444
Two-components catalysts Rh-ReOx/SiO2, Rh-MoOx/SiO2 and Ir-ReOx/SiO2 were active in the C-O hydrogenolysis of glycerol, 1,2-propanediol and tetrahydrofurfuryl alcohol. The activities were much higher than those of monometallic catalysts. The selectivities to terminal alcohols decreased in the following order: Ir-ReOx/SiO2 > Rh-ReOx/SiO2 > Rh-MoOx/SiO2 » Rh/SiO2. Characterization with XRD, TEM, CO adsorption, temperature-programmed reduction (TPR), XANES and EXAFS revealed that noble-metal particles were partially covered with ReOx or MoOx species. The MoOx species in Rh-MoOx/SiO2 formed a monomeric structure. The ReOx species in Rh-ReOx/SiO2 and Ir-ReOx/SiO2 formed monolayer clusters and multilayer clusters, respectively. A reaction mechanism was proposed where the alkoxide species formed on ReOx (or MoOx) was attacked by the active hydrogen species on Rh (or Ir) atoms bonded with the Re (or Mo) atom. The difference of the size of the modifier may affect the selectivity.