Effects of rhodium dispersion on catalytic behavior of Rh/active-carbon catalysts for H/D exchange reaction between CH4 and D2

Abstract

The H/D exchange reaction between CH₄ and D₂ was carried out over Rh/active-carbon catalysts, which were prepared from RhCl₃ and Rh(NO₃)₃. In the case of the catalysts prepared from RhCl₃, Rh species were homogeneously dispersed on the support from external surface to the inside of pores. Metallic particles of Rh were found to be the predominant species on the catalysts prepared from Rh(NO₃)₃ in the low Rh-loading region of <2 wt.%, whereas the number of highly dispersed Rh species remarkably increased with an increase in the amount of Rh-loading in the region of >2 wt.%. The reaction rate per unit gram of catalyst and the product distribution in methane reflected well the Rh-dispersion on the catalysts. The catalysts which contained the highly dispersed Rh species as predominant species were found to be more active for the H/D exchange reaction than the catalysts with relatively large metal particles of Rh. On the former, the ratio of CH₃D/CD₄ was observed to be much higher than that on the latter.