Stability of a Cs-promoted Co-Mo/Al2O3 catalyst during synthesis gas conversion

摘要

The stability of a Cs-promoted Co-Mo/Al2O3 catalyst, prepared by incipient wetness impregnation and operated under typical higher alcohol synthesis conditions, (280 degrees C, 8.2MPa, GHSV 8524h(-1), H-2:CO ratio 1) for up to 100h time-on-stream (TOS), is reported. The major cause of catalyst deactivation is shown to be due to carbonaceous deposits. The effect of adding H2O (0.047 and 0.094mol/mol (4.7 and 9.4 mol%)), NH3 (375-1500x10(-6)mol/mol (375-1500 ppmv)) and H2S (5x10(-6) and 10x10(-6)mol/mol (5 and 10 ppmv)) to the feed synthesis gas is also reported. Both the catalyst activity and the alcohol product selectivity are reduced in the presence of feed gas impurities, with H2O addition significantly increasing selectivity to CO2 and coke deposition. The impact of NH3 is reversible, whereas catalyst deactivation is only partially reversible in the case of H2O. H2S completely and irreversibly deactivates the catalyst.