The controlled deposition of a catalytically active material on a support, resulting in defined particle sizes and shapes, as well as control over the specific surface area of the active material and the support are usually limited when applying conventional catalyst preparation techniques. Flame spray pyrolysis offers the potential to overcome this limitation and is tested for the preparation of Fischer-Tropsch catalysts. Conventional single flame spray pyrolysis and, for the first time, double flame spray pyrolysis are compared for the synthesis of alumina supported cobalt catalysts. In the latter process the metal oxide precursors are combusted individually in two opposing nozzles. The key parameter for defining the final material composition is the intersection distance of the flames, which was systematically varied. The Fischer-Tropsch performance of the Co-based catalysts was studied in a fixed bed reactor at 230 degrees C and 20 bar. The catalytic results are discussed on the basis of structural characterization of the different catalysts by XRD, BET, TPR, UV-vis and TEM/EF-TEM. While catalysts made by single flame spray pyrolysis Were inactive in the Fischer-Tropsch reaction regardless of whether cobalt was subsequently mixed with alumina or the supported catalyst was directly prepared in the flame reactor, the double flame sprayed catalysts showed good catalytic activity. Depending on the intersection distance of the two flames, the formation of cobalt oxide and alumina occurred separately in each flame reactor. In spite of the independent particle growth in the two flames, the double flame reactor geometry lead to good adhesion of the two oxides resulting in good stabilization of cobalt nanoparticles on the alumina support during the Fischer-Tropsch reaction. (C) 2013 Elsevier B.V. All rights reserved.

Sol-gel chemistry offers versatile new ways to prepare catalysts with tunable compositions and in different forms of application. In particular the option to obtain catalytic coatings is of interest for microreactors or the deposition of catalysts on monolithic supports. The present study explored a sol-gel approach for Fe and Co Fischer-Tropsch catalysts based on the so-called epoxide addition method. As a support and structural promoter, respectively, alumina was added. In the case of cobalt, the role of different precursors was studied, whereas in the case of iron, varying Fe-Al2O3 ratios were investigated. In both cases, ambient drying resulted in xerogels with high specific surface areas. The performance of the xerogels as catalysts for the Fischer-Tropsch (FT) reaction was studied in a fixed bed reactor and compared to cobalt-and iron-based reference catalysts synthesized by established impregnation and precipitation methods, respectively. All catalysts were carefully characterized in the as-prepared state as well as after catalysis with respect to their reducibility, stability and the distribution of the FT active component. Our study proves the suitability of the applied sol-gel technique to prepare highly active alumina-promoted Fe as well as alumina-supported Co FT catalysts and provides insight into the structure-performance relationships of these systems.

Chemie Ingenieur TechnikVolume 84, Issue 8 p. 1316-1316 VortragFree Access Doppel-Flammen-Sprüh-Pyrolyse als innovative Technik zur Synthese von hochaktiven Fischer-Tropsch-Katalysatoren H. Großmann, Corresponding Author H. Großmann grossmann@iwt.uni-bremen.de Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanyUniversität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this authorM. Minnermann, M. Minnermann Universität Bremen, Institut für Angewandte und Physikalische Chemie, Bibliothekstraße 1, D-28359 Bremen, GermanySearch for more papers by this authorS. Pokhrel, S. Pokhrel Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this authorK. Thiel, K. Thiel Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung, Wiener Straße 12, D-28359 Bremen, GermanySearch for more papers by this authorH. Hagelin-Weaver, H. Hagelin-Weaver University of Florida, Department of Chemical Engineering, Gainesville, FL 32611-6005, USASearch for more papers by this authorM. Bäumer, M. Bäumer Universität Bremen, Institut für Angewandte und Physikalische Chemie, Bibliothekstraße 1, D-28359 Bremen, GermanySearch for more papers by this authorL. Mädler, L. Mädler Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this author H. Großmann, Corresponding Author H. Großmann grossmann@iwt.uni-bremen.de Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanyUniversität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this authorM. Minnermann, M. Minnermann Universität Bremen, Institut für Angewandte und Physikalische Chemie, Bibliothekstraße 1, D-28359 Bremen, GermanySearch for more papers by this authorS. Pokhrel, S. Pokhrel Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this authorK. Thiel, K. Thiel Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung, Wiener Straße 12, D-28359 Bremen, GermanySearch for more papers by this authorH. Hagelin-Weaver, H. Hagelin-Weaver University of Florida, Department of Chemical Engineering, Gainesville, FL 32611-6005, USASearch for more papers by this authorM. Bäumer, M. Bäumer Universität Bremen, Institut für Angewandte und Physikalische Chemie, Bibliothekstraße 1, D-28359 Bremen, GermanySearch for more papers by this authorL. Mädler, L. Mädler Universität Bremen, Stiftung Institut für Werkstofftechnik, Badgasteiner Straße 3, D-28359 Bremen, GermanySearch for more papers by this author First published: 25 July 2012 https://doi.org/10.1002/cite.201250356AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume84, Issue8Special Issue: ProcessNet-Jahrestagung 2012 und 30. Jahrestagung der BiotechnologenAugust, 2012Pages 1316-1316 RelatedInformation

To obtain nano-sized metal and metal salt crystallites with a narrow size distribution synthesis methods utilizing water in oil (w/o) microemulsions, i.e. reverse micelles, have been widely applied and reported in literature. In this study we show the effect of support addition at different stages of the reverse micelle based preparation of cobalt oxide on alumina model catalysts. All catalysts were characterized with X-ray powder diffraction and Raman spectroscopy indicating the presence of Co3O4 on the Al2O3 support. Studies of the reduction behaviour and X-ray photoelectron spectroscopy however revealed the presence of difficult to reduce cobalt aluminate species in the samples where the support was added during or shortly after the precipitation step in the synthesis process. It can therefore be assumed that if the alumina support is added to the reverse micelle solution unprecipitated Co2+ ions and partially dissolved Al3+ combine and form cobalt aluminates. In the preparations where the solid cobalt precipitates are recovered from the microemulsion and then supported on the carrier, no metal-aluminate formation could be observed. This study therefore gives important information how metal-support interaction can be affected during catalyst preparation using reverse micelles.