Deactivation on Co catalyst supported on alumina for Fischer- Tropsch synthesis

Co / Al2 O3 catalyst demonstrates a high performance in Fischer-Tropsch synthesis. In this study, the Co /Al2 O3 catalyst was prepared with impregnation method and the FTS performance of the catalyst was tested in a continu- ally stirred tank reactor (CSTR) at 220 ℃ ,2. 0 MPa,10 000 h-1 ,and syngas H2 / CO = 2. 0. With the increase of reac- tion time,the activity of the catalyst decreased continually while the selectivity to CH4 increased gradually. To under- stand the deactivation mechanism,spent catalysts with different reaction times were characterized with N2 adsorption (BET),X-ray photoelectron spectroscopy ( XRD),transmission electron microscope ( TEM) and temperature pro-grammed hydrogenation (TPH). The characterization results show that the pore structure of the catalyst had no signifi- cant change during the reaction. With the increase of reaction time,the Co metal particle size and carbon deposition amount in the catalysts increased. It was evident that the Co metal sintering and carbon deposition should be the main reasons of Co / Al2 O3 catalyst deactivation in this study. In order to improve the sintering resistance ability of the cata- lyst,the pore structure of the Al2 O3 support was adjusted to control the Co metal particle size distribution,and to inhib- it the formation of small Co particles that are easy to be sintered. Furthermore,by the modification of the catalyst reci- pe,a sintering and carbon deposition resistance Co catalyst was developed. The catalyst demonstrated high stability and low CH4 selectivity during a 1 800 h test in the CSTR.