Synthesis and application of γ-Al2O3 supported CoRu-based Fischer–Tropsch catalyst

The supported CoRu-based catalysts were prepared on γ-Al2O3 with different porous structures. The presence of polyethylene glycol (PEG) in a co-impregnation process could form small Co3O4 particles (8.4 nm) and maintain their extents of reduction (75.3%) as similar as large Co3O4 particles (21.5 nm, 79.8%) prepared by the PEG-free method on the small porous γ-Al2O3 (5.8 nm). Combined use of large porous γ-Al2O3 (21.2 nm) as support and the PEG-additive impregnation as preparative method, it reduced the size of Co3O4 to 4.6 nm which was about 3-fold smaller than the pore size of catalyst (14.5 nm). This finding contrasted to pore size–particle size dependence for supported Co-based catalyst prepared by the impregnation method. Although these small Co3O4 strongly interacted with Al2O3, it stabilized the Co0 formed in H2 leading to high fractional dispersion of Co0 (0.316). The resultant high dispersion of Co0 and large porous structure on catalyst provided more active sites and enhanced the diffusion of CO. This improved its Co-time yield 6-fold higher than small porous γ-Al2O3 supported catalyst prepared by same method.

► PEG-additive method forms smaller Co3O4 than pore size of nanofibrous γ-Al2O3. ► CoRu/nanofibrous γ-Al2O3 catalyst has more Co0 sites and better CO diffusion. ► Co-time yield and C5+ selectivity of CoRu/nanofibrous γ-Al2O3 are improved.