1 / 1

G. Jacobs*, M.C. Ribeiro*, W. Ma*, S. Khalid**, B.H. Davis*

Group 11 promoters Ag and Au facilitate Co reduction and boost Co metal site densities during Fischer-Tropsch synthesis. G. Jacobs*, M.C. Ribeiro*, W. Ma*, S. Khalid**, B.H. Davis* *University of Kentucky Center for Applied Energy Research **Brookhaven National Laboratory.

hakeem-knox
Télécharger la présentation

G. Jacobs*, M.C. Ribeiro*, W. Ma*, S. Khalid**, B.H. Davis*

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Group 11 promoters Ag and Au facilitate Co reduction and boost Co metal site densities during Fischer-Tropsch synthesis G. Jacobs*, M.C. Ribeiro*, W. Ma*, S. Khalid**, B.H. Davis* *University of Kentucky Center for Applied Energy Research **Brookhaven National Laboratory • Fischer-Tropsch synthesis (FT) is used to convert coal, natural gas, and biomass-derived syngas – a mixture of CO and H2 – to a distribution of hydrocarbons that can be upgraded to produce transportation fuels (e.g., diesel and jet fuels) and chemicals (e.g., lubricants and waxes). Alumina is often the support of choice for commercial slurry phase Fischer-Tropsch synthesis, due to its high attrition resistance and ability to stabilize small cobalt metal particles. However, due to the strong interaction between the support and cobalt oxides, catalyst activation, which involves reducing the Co3O4 to Co0 (surface Co0 being the active site) via CoO intermediate, can be a challenge. Expensive promoters like Pt are often added to promote reduction. • A combination of in-house (e.g., TPR and H2-chemisorption/pulse reoxidation) and synchrotron (e.g., XANES and EXAFS) methods was employed to characterize the catalysts. A significant improvement in extent of reduction was observed by addition of Cu, Ag, and Au that, for some specific cases, translated to significantly higher Co0 surface active site densities. Reactor testing using a slurry phase reactor confirmed a 75% increase in CO conversion with a negligible to slight decrease in C1 selectivity with certain catalysts promoted by Au and Ag. • The synchrotron measurements provided key information on oxidation state changes and local atomic structure in order to link the changes in catalyst structure with resulting improvements in performance. Normalized XANES spectra of references and cobalt catalysts after direct reduction of the calcined catalysts at 350oC in H2, including (a) 15%Co/alumina; (b) 1.63%Cu-15%Co/alumina, (c) 2.76%Ag-15%Co/alumina; (d) 5.05%Au-15%Co/alumina; (e) Co0 foil; and (f) CoO reference. Group 11 promoter addition significantly facilitates the reduction of CoO species, and in the cases of Ag and Au, boosting Co0 surface site densities, leading to higher CO conversion rates on a per gram catalyst basis. Jacobs, G.; Ribeiro, M.C.; Ma, W.; Ji, Y.; Khalid, S.; Sumodjo, P.T.A.; Davis, B.H., “Group 11 (Cu, Ag, Au) promotion of 15%Co/Al2O3 Fischer-Tropsch synthesis catalysts,” Applied Catalysis A: General 361 (2009) 137-151. Work performed on beamline X-18b.

More Related