Fischer–Tropsch synthesis: Support and cobalt cluster size effects on kinetics over Co/Al2O3 and Co/SiO2 catalysts

Ma, Wanhong; Jacobs, Gary; Sparks, Dennis E.; Gnanamani, Muthu Kumaran; Pendyala, Venkat Ramana Rao; Yen, Chia H.; Klettlinger, Jennifer L.S.; Tomsik, Thomas M.; Davis, Burtron H.

doi:10.1016/j.fuel.2010.10.029

Cited by 75 publications

(45 citation statements)

References 62 publications

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“…Ma et al [81] observed that due to the increase in the density of active Co 0 on the surface site, the average cobalt cluster diameter decreased by about 30% (from 38.4 nm for a catalyst containing 15 wt% metal content to 27 nm for a catalyst containing 25 wt% metal content) in a cobalt catalyst supported by silica, resulted in an increase in the intrinsic reaction rate constant by about 102%. Hong et al [82] enhanced the reducibility and catalytic activity of cobalt supported silica in F-T synthesis by adding organic additive (sorbitol, HOCH 2 (CHOH) 4 CH 2 OH) to the impregnation solution during the preparation step.…”

Section: Overview Of Previous Work Regarding the Fischer-tropsch Synmentioning

confidence: 99%

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

Mahmoudi

Doustdar

et al. 2017

Biofuels Engineering

147

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For more than half a century, Fischer-Tropsch synthesis (FTS) of liquid hydrocarbons was a technology of great potential for the indirect liquefaction of solid or gaseous carbon-based energy sources (Coal-To-Liquid (CTL) and Gas-To-Liquid (GTL)) into liquid transportable fuels. In contrast with the past, nowadays transport fuels are mainly produced from crude oil and there is not considerable diversity in their variety. Due to some limitations in the first generation bio-fuels, the Second-Generation Biofuels (SGB)' technology was developed to perform the Biomass-To-Liquid (BTL) process. The BTL is a well-known multi-step process to convert the carbonaceous feedstock (biomass) into liquid fuels via FTS technology. This paper presents a brief history of FTS technology used to convert coal into liquid hydrocarbons; the significance of bioenergy and SGB are discussed as well. The paper covers the characteristics of biomass, which is used as feedstock in the BTL process. Different mechanisms in the FTS process to describe carbon monoxide hydrogenation as well as surface polymerization reaction are discussed widely in this paper. The discussed mechanisms consist of carbide, COinsertion and the hydroxycarbene mechanism. The surface chemistry of silica support is discussed. Silanol functional groups in silicon chemistry are explained extensively. The catalyst formulation in the Fischer Tropsch (F-T) process as well as F-T reaction engineering is discussed. In addition, the most common catalysts are introduced and the current reactor technologies in the F-T indirect liquefaction process are considered. process overview IntroductionThe over-reliance of the world's nations on conventional fossil fuels puts our planet in peril. The continuity of the current situation will result in the rise of a combined average temperature over global land and ocean surfaces by 5 ∘ C in 2100, bringing a rise in sea levels, food and water shortages and an increase in extreme weather events. The global warming, caused by humans, is one of the biggest threats to our future well-being [1]. In addition, oil reserves are limited and these reserves are decreasing dramatically. This reduction alongside the other relevant economic factors affects the world's oil prices. The need to run engines with the new generation of liquid fuels is inevitable. The investigations by the US Energy Information Administration (EIA) published in 2013 expressed a 56 percent increase in the world's energy consumption by the year 2040. Total world energy demand will have risen to 865 EJ (exajoule) by this year. The total world energy consumption was reported as 553 EJ in 2010. The outlook indicates that renewable energy is one of the fastest-growing energy sources in the world; where its usage increases 2.5 percent per year. Despite increasing success in the renewable energies, it is predicted that the fossil fuels will supply al-

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Section: Overview Of Previous Work Regarding the Fischer-tropsch Synmentioning

confidence: 99%

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

Mahmoudi

Doustdar

et al. 2017

Biofuels Engineering

147

View full text Add to dashboard Cite

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“…Returning to cobalt/alumina catalysts, interestingly, by aging the catalyst sufficiently (i.e., the catalyst is significantly deactivated from its initial condition) [55] or utilizing catalysts with 10+ nm size [56], the deactivation rate becomes low, and the positive kinetic effect occurring on metallic cobalt particles can be observed. The main point is that the water effect can be modeled using a simple power law expression with a water effect parameter, m, and the magnitude and sign (i.e., positive [57] or negative [55,57]) of m provides valuable information about the structure of the catalyst.…”

Section: Modeling Of Site Suppression and Deactivationmentioning

confidence: 99%

Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

Jacobs¹,

Ma²,

Davis³

2014

Catalysts

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This focused review article underscores how metal reduction promoters can impact deactivation phenomena associated with cobalt Fischer-Tropsch synthesis catalysts. Promoters can exacerbate sintering if the additional cobalt metal clusters, formed as a result of the promoting effect, are in close proximity at the nanoscale to other cobalt particles on the surface. Recent efforts have shown that when promoters are used to facilitate the reduction of small crystallites with the aim of increasing surface Co 0 site densities (e.g., in research catalysts), ultra-small crystallites (e.g., <2-4.4 nm) formed are more susceptible to oxidation at high conversion relative to larger ones. The choice of promoter is important, as certain metals (e.g., Au) that promote cobalt oxide reduction can separate from cobalt during oxidation-reduction (regeneration) cycles. Finally, some elements have been identified to promote reduction but either poison the surface of Co 0 (e.g., Cu), or produce excessive light gas selectivity (e.g., Cu and Pd, or Au at high loading). Computational studies indicate that certain promoters may inhibit polymeric C formation by hindering C-C coupling.

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“…low temperature FischerTropsch synthesis or dry reforming of methane [1][2][3][4][5][6][7][8][9][10][11][12][13]). The catalytic activity of these catalysts is strongly related with the characteristics of Co phase, and thus with the preparation method, mainly with the impregnation-deposition procedure followed [14].…”

Section: Introductionmentioning

confidence: 99%

Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition

Vakros¹,

Bourikas²,

Kordulis³

et al. 2014

TOCATJ

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Abstract:The mode of retention of Co(H 2 O) 6 2+ species at the "γ-alumina/aquatic solution" interface is refined using simulations, adsorption isotherm, potentiometric mass titrations and mainly proton -ion titrations jointly with diffuse reflectance spectroscopy. It was found that the increase in the Co(II) surface concentration affects considerably the kind of the Co(II) species deposited. Mononuclear/mono-substituted inner sphere Co(II) complexes are formed at extremely low Co(II) surface concentration. A mixed surface state involving mononuclear/mono-substituted and binuclear/bi-substituted Co(II) complexes is formed at relatively low Co(II) surface concentration. Only binuclear/bi-substituted Co(II) complexes are formed at intermediate Co(II) surface concentration. Finally, oligo-nuclear inner sphere Co(II) species are formed at relatively high Co(II) surface concentration, in addition to the bi-nuclear ones. The above species concern a range of surface Co(II) concentration extending from zero to 2.7 theoretical surface layers of [Co(H 2 O) 6 ] 2+. The formation of Co(II) surface precipitate starts above these theoretical surface layers. The above indicates that one may control the surface Co(II) concentration, by adjusting the Co(II) concentration in the impregnating solution, and thus the Co(II) surface species formed. This control allows tailoring the preparation of cobalt catalysts supported on γ-alumina and thus the development of effective Co/γ-alumina catalysts.

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Fischer–Tropsch synthesis: Support and cobalt cluster size effects on kinetics over Co/Al2O3 and Co/SiO2 catalysts

Cited by 75 publications

References 62 publications

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition

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