the slurry bubble column reacting system while maintaining or increasing the activity of the catalyst application_number US 81079001 A description the present invention provides supported cobalt catalysts which are well suited for use in fischer tropsch synthesis processes these catalysts are particularly well suited for use in three phase reactor processes examples of general catalyst compositions provided by the present invention include a cobalt without any promoter preferably supported on doped u03b3 alumina b cobalt with one or more noble metal promoters preferably supported on doped u03b3 alumina c cobalt promoted with both a noble metal promoter and one or more selectivity promoters preferably an alkali or rare earth oxide preferably supported on doped u03b3 alumina and d cobalt promoted with one or more selectivity promoters and without a noble metal promoter preferably supported on doped u03b3 alumina examples of typical promoters include but are not limited to noble metals such as ruthenium metal oxides such as oxides of zirconium lanthanum or potassium and other oxides of elements from groups ia iia ivb vb and vib preferred catalyst compositions comprise per 100 parts by weight of support from about 10 to about 70 pbw cobalt from about 0 1 to about 8 pbw ruthenium when present from about 0 1 to about 8 pbw potassium when present and from about 0 5 to about 8 pbw lanthana when present the catalyst can also include other promoter materials we have discovered that to obtain a particularly desirable combination of selectivity and activity particularly in reaction systems such as slurry bubble column reactors the catalysts will most preferably comprise per 100 parts by weight of support from about 15 to about 55 pbw more preferably from about.