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Ce-promoted Co/Al2O3 catalysts for Fischer-Tropsch synthesis
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. Univ Mayor San Andres, Bolivia.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
2017 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 42, no 15, 9754-9765 p.Article in journal (Refereed) Published
Abstract [en]

The effect of ceria promotion on the performance of Co/Al2O3 catalyst was evaluated in a high pressure fixed bed reactor for Fischer Tropsch (FT) synthesis at close industrial conditions. Ce-Al2O3 supports with a molar ratio of Al/Ce = 8 were prepared by two different methods: one by co-precipitation of cerium and aluminum precursors in water in-oil microemulsion and the other one by aqueous impregnation of cerium nitrate on commercial alumina. These supports, together with the unmodified alumina carrier, were used to prepare four cobalt-based catalysts. These catalysts were characterized by XRD, SEM, EDX, TEM, N-2 adsorption/desorption, TPR and chemisorption techniques. The results show that the presence of CeO2 on the surface of the support favors the reducibility of cobalt oxides with a shift down in reduction temperature of about 70 degrees C. The catalytic evaluation of the catalysts revealed that cerium addition by impregnation increases the activity and selectivity to C5+ catalyst in FTS. The catalyst synthetized by microemulsion show lower catalytic performance. Nevertheless, the catalytic property of this material can be improved by increasing the crystalline micro-domains size of CeO2. (C) 2017 Hydrogen Energy Publications LLC.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD , 2017. Vol. 42, no 15, 9754-9765 p.
Keyword [en]
Water-in-oil-microemulsion, Cerium promoter, Cobalt-alumina catalyst, Fischer-Tropsch synthesis
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-210386DOI: 10.1016/j.ijhydene.2017.01.056ISI: 000402587500039OAI: oai:DiVA.org:kth-210386DiVA: diva2:1119514
Note

QC 20170704

Available from: 2017-07-04 Created: 2017-07-04 Last updated: 2017-10-04Bibliographically approved
In thesis
1. Cobalt catalyst supports for Fischer-Tropsch synthesis
Open this publication in new window or tab >>Cobalt catalyst supports for Fischer-Tropsch synthesis
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the Fischer-Tropsch (FT) synthesis, CO and H2 (synthesis gas) are converted into hydrocarbons that can be further upgraded to high-quality fuels and chemicals. Different carbon sources such as natural gas, coal and biomass can be used as feed-stocks for the synthesis gas. In commercial applications, supported cobalt catalysts are commonly used in the FT synthesis, especially when the synthesis gas emanates from natural gas and when the desired final product is diesel. The activity and selectivity of a cobalt catalyst is dependent on several parameters, one of them being the support.

The present thesis is focused on the design, synthesis and characterization of alumina and silica materials (with and without Ce and Zr promoters) with non-conventional morphology, and evaluation of their feasibility as cobalt supports in the FT synthesis.

Ce- and Zr-alumina nanoparticles were synthesized by co-precipitation in water-in-oil microemulsion. The obtained product is amorphous alumina with highly dispersed promoters, resulting in strong cobalt-support interactions and low cobalt reducibility. By increasing the calcination temperature of the Ce-promoted support, crystalline CeO2 is obtained which apparently increases the cobalt reducibility and thereby the catalytic activity (per gram catalyst). The small pore size of the materials may induce diffusion limitations on the reactants arrival and/or result in very small cobalt particles, which favour methane over long-chain hydrocarbons. 

Successful preparations of pore expanded mesoporous silicas with 1D, 2D and 3D pore structures via the atrane route, combined with the addition of swelling agents, have been demonstrated. The advantage of this method is that pore expansion can be achieved at mild conditions and there is no need for a post-synthesis process using an autoclave system. In larger silica support pores, larger cobalt particles will be formed and the weaker the cobalt-support interactions will be. This generally results in a higher cobalt reducibility for larger-pore supports and thereby a higher catalytic activity.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017
Series
TRITA-CHE-Report, ISSN 1654-1081
Keyword
Silica, alumina, zirconium, cerium, mesoporous materials, nanoparticles, microemulsion, atrane route, cobalt catalyst, Fischer-Tropsch synthesis
National Category
Engineering and Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-215121 (URN)978-91-7729-548-8 (ISBN)
Public defence
2017-10-26, L1, Drottning Kristinas väg 30, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20171004

Available from: 2017-10-04 Created: 2017-10-02 Last updated: 2017-10-05Bibliographically approved

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