Direct reduction of cobalt nitrate versus conventional calcination/reduction treatment was conducted using alumina with identical methodology as previously applied to SiO₂ and TiO₂. Similar BET surface areas, pore volumes and pore size distributions were obtained for the activated calcined and uncalcined catalysts indicating no significant difference in morphological properties. However, the reducibility slightly increases and Co crystallite size is smaller for activated uncalcined samples. Reduction phenomena were analyzed by TPR-MS and TPR-EXAFS/XANES. Combining these techniques allows an explanation of the complex phenomena occurring during the direct reduction of cobalt nitrate, as both nitrate decomposition and cobalt oxide reduction are involved. Cobalt nitrate species are converted to CoO_x intermediates. These species are oxidized by NO_X (from nitrate decomposition) to Co₃O₄ spinel, which is converted to CoO prior to Co⁰ formation. Noble metals (Pt, Re, Ru and Ag) improve cobalt oxide reducibility, especially for the final reduction step (i.e., CoO to Co⁰). The effect of direct nitrate reduction on FT activity was investigated using a 1 L CSTR. Activated unpromoted and Pt-promoted uncalcined catalysts achieved higher initial and steady-state CO conversions in comparison to the corresponding calcined catalysts. The best performance was achieved with direct reduction of uncalcined 0.5 %Pt-25 %Co/Al₂O₃.

使用氧化铝以与以前应用于SiO ₂和TiO ₂相同的方法，对硝酸钴与常规煅烧/还原处理进行了直接还原。对于活化的煅烧和未煅烧的催化剂，获得了相似的BET表面积，孔体积和孔径分布，表明在形态学性质上没有显着差异。但是，对于未煅烧的活化样品，还原度略有增加，Co晶粒尺寸较小。通过TPR-MS和TPR-EXAFS / XANES分析还原现象。结合使用这些技术可以解释在直接还原硝酸钴过程中发生的复杂现象，因为涉及硝酸盐分解和氧化钴还原。硝酸钴物质转化为CoO _x中间体。这些物质被NO _X（由硝酸盐分解）氧化为Co ₃ O _4。尖晶石，在形成Co ⁰之前先转化为CoO 。贵金属（Pt，Re，Ru和Ag）提高了氧化钴的还原性，尤其是对于最后的还原步骤（即CoO到Co ⁰）。使用1 L CSTR研究了硝酸盐直接还原对FT活性的影响。与相应的煅烧催化剂相比，活化的未促进和Pt促进的未煅烧催化剂实现了更高的初始和稳态CO转化率。直接还原未煅烧的0.5％Pt-25％Co / Al ₂ O ₃可获得最佳性能。