Fischer–Tropsch synthesis: effect of water on the deactivation of Pt promoted Co/Al 2O 3 catalysts

Abstract

The effect of water on the deactivation of a Pt promoted Co/Al 2O 3 catalyst [15%Co-Pt(0.5%)/Al 2O 3] during Fischer–Tropsch (FT) synthesis was studied in a continuously stirred tank reactor (CSTR) by (1) varying the conversion through changes of the space velocity and (2) by including additional water into the feed gas. At higher space velocities (>2 SL/gcat/h), the catalyst was exposed to low water partial pressures and exhibited stable activity. The runs with lower space velocities resulted in higher water partial pressures and higher catalyst deactivation rates. The addition of small amounts of water slightly decreased CO conversion and the effect was reversible. Increasing the amount of added water to provide P H 2O / P CO∼1 in the feed resulted in a permanent deactivation of the catalyst. The higher CO 2 selectivity indicated that cobalt oxide or another catalytic form of cobalt such as cobalt aluminate was formed under higher water partial pressure.