Effect of Properties of Various Activated-Carbon Supports and Supported Fe−Mo−Cu−K Catalysts on Metal Precursor Distribution, Metal Reduction, and Fischer−Tropsch Synthesis

The physical and surface chemistry properties of four activated carbons (ACs) have been studied, and the effects of these properties on the distribution and reduction of metal precursors of Fischer−Tropsch (FT) catalysts have been noted. The four ACs used have been derived from peat, generic wood, pecan, and walnut. The catalysts used are Fe with Mo−Cu−K additives, supported on the various ACs, successfully used earlier for selective production of C1−C34 hydrocarbons. Characterization techniques used include Brunauer−Emmett−Teller (BET), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), surface pH, temperature-programmed desorption−mass spectrometry (TPD−MS), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). The BET and SEM results show that the four ACs have similar overall pore-size distributions qualitatively. All ACs contain 75−94% micropores. The four ACs differ considerably in their surface morphology, surface area, and amounts of micro-, meso-, and macropores. The AC derived from peat is the least porous. ACs derived from pecan and walnut show ridges containing small spherical agglomerates. These ACs contain relatively more meso- and macropores (wide pores) than the wood AC, which has a wide distribution of irregular agglomerates. The EDS result indicates that all four ACs contain 5.6−7.5% oxygen; the wood- and peat-based varieties include smaller amounts of other impurities as well. The results of pH and TPD indicate that the surface of all four ACs are primarily covered by neutral and/or basic oxygen-containing groups, along with small amounts of acidic oxygen groups. Analyzing the BET, TPD, and TEM results of the four carbon-supported Fe−Mo−Cu−K catalysts shows that metal precursors are uniformly distributed on each AC surface, but the distribution of metal precursors on the carbon surface is likely related to pore types and amounts and not the total surface area of supports. Wide pores play a more important role to distribute metal precursors than micropores. Metal precursors tend to be present predominantly inside the pores of the peat-, pecan-, and walnut-based ACs, which contain greater amounts of wide pores. However, for the wood-based AC, which contains greater amounts of micropores, more metal precursors tend to be present on the exterior surface and the average metal particle size is also larger. The TPR and BET results indicate that the interaction between metallic precursors and