Preparation of egg-shell-type Ni/Ru bimetal alumina pellet catalysts: Steam methane reforming for hydrogen production

Egg-shell-type pellet catalysts were prepared by selectively placing nickel and/or ruthenium on the outer region (shell) of alumina pellets so that the active components can be utilized effectively in steam methane reforming (SMR) reaction with high gas-hourly space velocity conditions. To ensure the reproducibility of catalyst preparation, we evaluated two types of commercial alumina pellets. And, we finally selected one commercial alumina pellet, which had uniform pores distribution. The thickness of the ruthenium-shell can be controlled by optimizing the evaporation temperature and rotating speed while preparing an 'egg-shell-type' 1 wt. % Ru/alumina catalyst. When applied to a SMR reaction, as the space velocity of the reactant increased in SMR reaction, 'egg-shell-type' 1 wt. % Ru/alumina catalyst showed a higher methane conversion than a 'homo-type' 1 wt. % Ru/alumina pellet catalyst, in which the active metal was uniformly dispersed in the whole region of pellet. Since ruthenium is a costly noble metal, we prepared a Ni/Ru bimetal catalyst ['egg-shell-type' 5 wt. % Ni/0.7 wt. % Ru bimetal catalyst] substituting nickel for some portion of the ruthenium in order to increase the economic feasibility. The bimetal Ni/Ru catalyst showed even better CH4 conversion than the egg-shell-type catalyst containing ruthenium only. We also confirmed that the egg-shell-type catalyst effectively utilized its active components in the SMR reaction.