Fischer–Tropsch Synthesis: Preconditioning Effects Upon Co-Containing Promoted and Unpromoted Catalysts

Abstract

In the preparation and evaluation of FischerTropsch (FT) catalysts, active catalysts formed by both incipient wetness impregnation (IWI) and atomic layer deposition (ALD) of major components were demonstrated. ALD-deposited Co on a silica support was more effective than a similar catalyst deposited upon a support of ALD-deposited Al 2 O 3 on silica. The addition of Co reduction promoters including Pt, Ir and Ru using either ALD or IWI has been shown to strongly affect the catalyst pre-conditioning step. CO conversion results were consistent with previously reported Temperature Programmed Reduction X-ray Absorption Near-edge Structure/Extended X-ray Absorption Fine Structure Spectroscopy (TPR-XANES/EXAFS) experiments observing the nature of chemical transformations occurring during the activation of cobalt-based FT catalysts in hydrogen. Specifically, there exists a 2-step reduction process involving Co 3 O 4 to CoO and CoO to Co 0 transformations. The extent of catalyst preconditioning was strongly affected by the reduction temperature (with 400°C preferred) and the loading of the promoter. This was demonstrated using a continuous-flow catalytic-bed unit with a 2:1 molar blend of H 2 :CO, at temperatures ranging from about 260 to 300°C, pressures averaging 1.3 MPa (190 psia), and gas space velocities about 24 NL/h-g.

Co-Supported CeO2Nanoparticles for CO Catalytic Oxidation: Effects of Different Synthesis Methods on Catalytic Performance

“…These results clearly show that the reduction behavior of Co 3 O 4 strongly depends on the CeO 2 synthesis method, dispersion state of CoO x , and the interaction between CoO x and CeO 2 , which is consistent with conclusions of previous reports [26,43]. For the Co/CeO 2 catalysts, the reduction peaks can be classified as follows: (1) [41,42]. Among these catalysts, Co/CeO 2 -h displayed the lowest reduction temperature, which indicates that Co/CeO 2 -h exhibits the best redox performance.…”

“…Similarly, all the samples display β peaks at about 800 • C due to the reduction of bulk CeO 2 , and it can be observed that the temperature of the reduction peak decreases gradually in the order 4%Co/CeO 2 -h< 4%Co/CeO 2 -p < 4%Co/CeO 2 -c. This further confirms that 4%Co/CeO 2 -h exhibits the best reduction performance among all catalysts and that strong interactions between the active component CoO x and CeO 2 supports are present. Various studies [40][41][42] have shown that the reduction of Co 3 O 4 is a two-step process, involving the reductions of Co 3 O 4 to CoO and CoO to Co. These results clearly show that the reduction behavior of Co 3 O 4 strongly depends on the CeO 2 synthesis method, dispersion state of CoO x , and the interaction between CoO x and CeO 2 , which is consistent with conclusions of previous reports [26,43].…”

The application of synchrotron methods in characterizing iron and cobalt Fischer–Tropsch synthesis catalysts

“…The first section demonstrates how these uncertainties were overcome by coupling XANES and EXAFS spectroscopies to temperature programmed reduction/carburization [32][33][34][35][36][37][38][39][40]. The influence of catalyst preparation [39][40][41][42][43][44] and pretreatment [37,44,45] on activation is also addressed to some extent in this section. The working state of unpromoted catalysts has also been investigated by EXAFS [e.g., 56].…”

“…In some cases, researchers have examined -using EXAFS and XANES spectroscopies -the impact of the promoter on the extent [57][58][59][60] or both rate and extent [7,34,39,61,62] of reduction of cobalt oxides simply by focusing on changes at the Co edges. Researchers have also explored the carburization of iron oxides by examining Fe edge data [35,36,38,62].…”

Fischer-Tropsch Synthesis: The Characterization and Testing of Pt-Co/SiO2 Catalysts Prepared with Alternative Cobalt Precursors

“…For example, Bambal et al [22] added chelating agents such as nitrilotriacetic acid and ethylenediaminetetraacetic acid to silica, which modified the surface prior to adding cobalt nitrate; the resulting dispersions were improved by 2-4.3 times. Another example was the use of atomic layer deposition (ALD), which enabled a decrease in the size of Co particles from 10.1 nm to the range of 5.6-5.9 nm for Co/silica catalysts with Co loadings in the range of 20-25% [23].…”