Takenaka et al. investigated the catalytic nature of active species (Ru, Co, Ni, Fe, Pd, and Pt) on SiO2 as well.4 Over Ru, Co, and Ni on SiO2, CO was converted at temperatures below 380 °C, while over Fe, Pd, and Pt on SiO2, CO remained unreacted. In spite of high CO conversion, Co species do not seem to be suitable active species because Co catalysts improve not only the activity of CO hydrogenation but also the activity of WGS reaction.