546762 Soldering Promoters for Iron and Cobalt Fischer-Tropsch Catalysts

Wednesday, June 5, 2019: 1:30 PM
Texas Ballroom EF (Grand Hyatt San Antonio)
Bang Gu1, Vitaly Ordomsky2, Mounib Bahri3, Ovidiu Ersen3, P.a. Chernavskii4 and Andrei Khodakov2, (1)Lille University of Science and Technology, Lille, France, (2)Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France, Villeneuve d'Ascq, France, (3)Strasbourg University, Strasbourg, France, (4)Moscow State University, Moscow, Russian Federation

Soldering promoters for iron and cobalt Fischer-Tropsch catalysts

Bang Gua, Vitaly V. Ordomskya, Mounib Bahrib, Ovidiu Ersenb, Petr A. Chernavskiic  and Andrei Y. Khodakova*

aUniv. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France

bIPCMS-UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, BP 43-67034 Strasbourg Cedex 2, France

cDepartment of Chemistry, Moscow State University, 119992 Moscow, Russia

Fischer-Tropsch (FT) synthesis is one of the most practicable ways to convert non-oil based feedstocks like natural gas, coal, biomass and shell gas to valuable fuels and chemicals [1]. Iron and cobalt catalysts have been widely used in FT synthesis. Many efforts have been dedicated to improve the activity and stability. Here, we found that metals usually used for soldering (Bi and Pb) had major positive effects on the catalytic performance and stability of iron and cobalt catalysts [2-3].

Iron catalysts have been widely used in high temperature FT synthesis for direct light olefin synthesis from syngas. We found that the promotion of iron catalysts with Bi and Pb results a remarkable increase (several times) in the FTO reaction rate and selectivity to the C2-C4 olefins (up to 55%-65%). The direct olefin synthesis from syngas occurs even at under atmospheric pressure. The presence of the promoters significantly slows down secondary hydrogenation of olefins and decreases the chain growth probability and selectivity to the C5+ hydrocarbons. A combination of characterization techniques uncovered notable migration of the promoting elements during the reaction and decoration of iron carbide nanoparticles with the promoters to form core-shell structures. The promoters seem to facilitate CO dissociation by removing O atoms from iron carbide.

  Figure 1. Promotion effect on activity and stability on iron(A)[2] and cobalt (B)catalysts in Fischer-Tropsch synthesis

Deactivation remains one of the main challenges of the cobalt-based catalysts in FT process. The major deactivation mechanisms of cobalt catalysts involve metal sintering and carbon deposition. Interestingly, the soldering promoter Bi also has an excellent effect of improving the stability of cobalt catalysts. Bismuth remarkably reduces both carbon deposition and metal sintering. At low content of the promoter, bismuth does not affect the selectivity of FT synthesis. Coupling of carbon oxidation with CO hydrogenation over the Bi-promoted catalysts reduces carbon deposition and results in the continuous catalyst self-regeneration under FT reaction conditions. Decoration of metal nanoparticles with Bi, which is highly mobile under the reaction conditions, protects them from sintering.

[1] A. Y. Khodakov, W. Chu, P. Fongarlond, Chemical Review, 2007, 107(5), 1692-1744

[2] Y. Luo, B. Gu, A.Y. Khodakov, et al., ACS Catalysis, 2017, 7(10), 6445-6452.

[3] B. Gu, V.V. Ordomsky, A.Y., Khodakov, et al., Applied Catalysis B: Environment, 2018, 234, 153-166.

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