Structural analysis of unpromoted Fe-based Fischer–Tropsch catalysts using X-ray absorption spectroscopy

Li, Senzi; O’Brien, Robert; Meitzner, G.; Hamdeh, Hussein H.; Davis, Burtron H.; Iglesia, Enrique

doi:10.1016/s0926-860x(01)00694-9

Cited by 104 publications

(75 citation statements)

References 23 publications

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“…The Fe K-edge XANES spectra for the standards, as well as the fresh calcined and activated Albemarle and Engelhard catalysts are presented in Figure- FeO, which is consistent with the literature for a CO pretreated Fe-based FT catalyst [26,[34][35][36]]. …”

Section: Xanes Resultssupporting

confidence: 86%

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Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

Adeyiga¹

2010

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Section: Xanes Resultssupporting

confidence: 86%

“…An assumption made in the least squares fitting was that the XANES contribution from the iron carbide (Fe x C) would be close agreement to the θ-Fe 3 C standard, which was also assumed in previous studies [26,34,36]. The least squares fitting results are in Table-3.…”

Section: Xanes Resultsmentioning

confidence: 72%

Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

Adeyiga¹

2010

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“…Recently, detailed studies on the structure and the evolution of the iron catalysts on active surface indicated that the working surface in F-T synthesis might be described as a dynamic phase, surrounding a thermodynamically stable oxide or carbide core, and consisting of oxygen and carbon vacancies, surface oxygen, and carbon atoms occupying lattice positions in the underlying bulk [13][14][15]. Through the study on the carburizing performance of the unreduced K/Cu/Fe catalysts, Li et al [15] have proved that the presence of K and Cu increased the F-T rates as well as the extent of steadystate carburization by providing nucleation sites for the formation of smaller FeC x crystallites.…”

Section: Introductionmentioning

confidence: 99%

CO Hydrogenation to Light Alkenes Over Mn/Fe Catalysts Prepared by Coprecipitation and Sol-gel Methods

Wang

Sun

et al. 2005

Catal Lett

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CO hydrogenation to light alkenes was carried out on manganese promoted iron catalysts prepared by coprecipitation and sol-gel techniques. Addition of manganese in the range of 1-4 mol.% by means of coprecipitation could improve notably the percentage of C 2 = $C 4 = in the products, but it was not so efficient when the sol-gel method was employed. XRD and H 2 -TPR measurements showed that the catalyst samples giving high C 2 = $C 4 = yields possessed ultrafine particles in the form of pure a-(Fe 1-x Mn x ) 2 O 3 , and high quality in lowering the reduction temperature of the iron oxide. Furthermore, these samples displayed deep extent of carburization and different surface procedures to the others in the tests of Temperature Programmed Surface Carburization (TPSC). The different surface procedures of these samples were considered to have close relationship with the evolving of surface oxygen. It was also suggested that for the catalysts with high C 2 = $C 4 = yields, the turnover rate of the active site could be kept at a relatively high level due to the improved reducing and carburizing capabilities. Consequently, there would be a large number of sites for CO adsorption/dissociation and an enhanced carburization environment on the catalyst surface, so that the process of hydrogenation could be suppressed relatively to a low level. As a result, the percentage of the light alkenes in the products could be raised.

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“…After problems with the Polywax 3000 and C 30 oil catalyst slurry, baseline filtration tests using Polywax 500 (with an average C [25][26][27][28][29][30] ) and 5 wt% iron oxide catalyst were conducted with and without permeate back-pulsing. As shown in Figure 1.…”

Section: Filtration Tests With Polywax 500/catalyst Slurrymentioning

confidence: 99%

“…Oxide-carbide phase-transformations during activation and/or Fischer-Tropsch synthesis induce a volumetric change due to a significant difference in densities and the resulting shear may lead to the formation of small crystallites of iron carbides which split off to form ultrafine particles [27]. The conversion of the oxide to carbide phase is dynamic and may be reversible depending upon the environment.…”

Section: − αmentioning

confidence: 99%

Separation of Fischer-Tropsch Wax Products from Ultrafine Iron Catalyst Particles

Sarkar¹,

Neathery²,

Davis³

2006

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A fundamental filtration study was started to investigate the separation of FischerTropsch Synthesis (FTS) liquids from iron-based catalyst particles. Slurry-phase FTS in slurry bubble column reactor systems is the preferred mode of operation since the reaction is highly exothermic. Consequently, heavy wax products in one approach may be separated from catalyst particles before being removed from the reactor system.Achieving an efficient wax product separation from iron-based catalysts is one of the most challenging technical problems associated with slurry-phase iron-based FTS and is a key factor for optimizing operating costs. The separation problem is further compounded by attrition of iron catalyst particles and the formation of ultra-fine particles.Existing pilot-scale equipment was modified to include a filtration test apparatus.After undergoing an extensive plant shakedown period, filtration tests with cross-flow filter modules using simulated FTS wax slurry were conducted. The focus of these early tests was to find adequate mixtures of polyethylene wax to simulate FTS wax. Analysis techniques for catalyst particle size distribution were also developed. Initial analyses of the slurry and filter permeate particles focused on catalyst particle attrition and the formation of ultra-fine iron carbide and/or carbon particles. The effects of chemical and physical changes of the catalyst slurry during activation/synthesis on the filtration properties were also studied.A study of various molecular weight waxes was initiated to determine the effect of wax physical properties on the permeation rate without catalyst present. It was found that the permeate flux was inversely proportional to the nominal average molecular 3 weight of the polyethylene wax. Even without catalyst particles present in the filtrate, the filter membranes experience fouling during an induction period on the order of several days on-line.Another long-term filtration test was initiated using a batch of ultrafine iron catalyst that was previously activated with CO in a separate continuous stirred tank reactor (CSTR) system. The permeate flux stabilized more rapidly than that experienced with unactivated catalyst tests.A series of crossflow filtration experiments were initiated to study the effect of olefins and oxygenate on the filtration flux and membrane performance. Iron-based FTS reactor waxes contain a significant amount of oxygenates, depending on the catalyst formulation and operating conditions. Mono-olefins and aliphatic alcohols were doped into an activated iron catalyst slurry (with Polywax) to test their influence on filtration properties. The olefin concentrations were varied from 5 to 25wt% and oxygenates from 6 to 17 wt% to simulate a range of reactor slurries reported in the literature. The addition of an alcohol (1-dodecanol) was found to decrease the permeation rate while the olefin added (1-hexadecene) had no effect on the permeation rate. A passive flux maintenance technique was tested that can temporarily increase the...

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Structural analysis of unpromoted Fe-based Fischer–Tropsch catalysts using X-ray absorption spectroscopy

Cited by 104 publications

References 23 publications

Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

CO Hydrogenation to Light Alkenes Over Mn/Fe Catalysts Prepared by Coprecipitation and Sol-gel Methods

Separation of Fischer-Tropsch Wax Products from Ultrafine Iron Catalyst Particles

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