Impact of Activation Conditions on the State of the Active Cobalt Surface in Co-Al Catalysts of Fischer-Tropsch Synthesis
Co-based catalysts are well-known as effective catalysts for Fischer-Tropsch synthesis (FTS) from hydrogen-rich syngas. To a great extent activity of the catalysts is determined by the dispersion of Coo particles formed on the surface of the catalysts after reductive activation. Our work was aimed at exploring the possibility of controlling the dispersion of Coo particles formed in the course of reductive activation of oxide precursors of Co-Al catalysts. Temperature-programmed reduction (TPR) was used for investigation of the reduction dynamics of oxide precursors formed during the thermal treatment of combined CoAl hydroxo-nitrate-carbonate compounds having a hydrotalcite-type structure in the inert atmosphere and in the inert atmosphere containing 3-4% vol. NO. It was shown that the reduction occurs in two main stages, that, according to the XRD data , correspond to the reduction of Co (III) to Co (II) and then to Coo. The character of reduction depends on the oxidative properties of the gas during thermal pretreatment, particularly at the stage of formation of Co (II) (Figure 1). The specific surface area of Coo was measured by N2O titration method. The catalysts pretreated in NO-containing Ar have higher specific Coo surface area (Table 1). The catalytic tests of obtained catalysts in FTS were performed at 0.1 and 2.1 MPa, H2:CO:N2 = 6:3:1, at 210oC in a fixed bed reactor.