A sulfided Pd/SiO 2 catalyst was doped with various kinds of metal additives (M: Li, K, Cs, Mg, Ca, Sr, Ba, Sc, Y, La, Nd, Mn, Zn, or Al) and used for methanol synthesis from CO hydrogenation. The addition of Ca, Y, La, or Nd significantly improved the activity for methanol synthesis, and among these additives, Ca was the most effective additive. Besides, the methanol synthesis activity of the sulfided Pd/SiO 2 doped with the Ca additive changed, depending on the preparation method of the precursor. The calcination of the precursor after impregnating with the Pd-containing solution was helpful for improving the methanol synthesis activity. The most active catalyst doped with the Ca additive yielded 720 g kg-cat -1 h -1 of methanol at 593 K and 5.1 MPa, which was about 50% of the space-time yield of methanol that is obtained with a commercial Cu/Zn/Al catalyst at 593 K and 5.1 MPa from a syngas containing CO 2 . Besides, even in the presence of H 2 S, the sulfided Pd/SiO 2 catalyst doped with the Ca additive preserved 35% of the initial activity. The undoped catalyst showed a much lower methanol synthesis activity than the doped catalyst in the presence of H 2 S as well. Thus, even in the presence of a small amount of H 2 S in syngas, the Ca additive shows the promoting effect on increasing the methanol synthesis activity. In contrast with the sulfided catalysts, in the presence of H 2 S, the methanol synthesis activity of the Cu/Zn/Al catalyst decreased linearly with time on-stream and eventually dropped to zero.
