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Title: Fischer-tropsch synthesis: temperature programmed EXAFS/XANES investiation of the influence of support type, cobalt loading, and nobel metal promoter addition to the reduction behavior of cobalt oxide particles.

Abstract

TPR-XANES/EXAFS carried out using a novel multi-sample holder provided key information for verifying the nature of the chemical transformations occurring during cobalt Fischer-Tropsch synthesis catalyst activation in hydrogen. In the past, assumptions had to be made regarding the nature of the cobalt species present along the trajectory of a standard TPR experiment. The new technique directly provided insight into (a) the nature of the reduction process of cobalt oxide species and (b) the resulting cobalt crystallite size, as a function of the strength of the catalyst support interaction with the cobalt oxide species. A two-step reduction process involving Co{sub 3}O{sub 4} to CoO and CoO to Co{sup 0} transformations over standard calcined catalysts was observed and quantified over all catalysts exhibiting both weak interactions (e.g., Co/SiO{sub 2}) and strong interactions (e.g., Co/Al{sub 2}O{sub 3}) with the support. Noble metal promoter (e.g., Pt) addition strongly improved the reducibility of cobalt oxide species, most likely via a H{sub 2} dissociation and spillover mechanism. Increasing cobalt loading, on the other hand, led to a measurable, but lesser, improvement on reducibility, due to the larger resulting particle size that resulted in less surface contact with the support. Higher reduction temperatures were needed to effectivelymore » reduce cobalt oxide particles deposited on strongly interacting surfaces in comparison with unsupported Co{sub 3}O{sub 4} or only weakly interacting supported cobalt catalyst. Nevertheless, despite lower extents of reduction, the smaller resulting Co particles on the more strongly interacting catalysts generally led to higher Co{sup 0} active site densities. The addition of the noble metal promoter to strongly interacting supported catalyst significantly decreased the temperature required to reduce the cobalt oxides to Co{sup 0} particles; this allows one to take advantage of the higher Co{sup 0} surface areas arising from the combination of a smaller average Co{sup 0} particle size and a higher extent of reduction.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
FE; National Aeronautic and Space Administration (NASA); Commonwealth of Kentucky
OSTI Identifier:
947529
Report Number(s):
ANL/CMT/JA-58434
Journal ID: ISSN 0926-860X; ACAGE4; TRN: US200905%%54
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Appl. Catal. A; Journal Volume: 333; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
01 COAL, LIGNITE, AND PEAT; 08 HYDROGEN; CATALYST SUPPORTS; CATALYSTS; COBALT; COBALT OXIDES; DISSOCIATION; FISCHER-TROPSCH SYNTHESIS; HYDROGEN; PARTICLE SIZE; PROMOTERS; STRONG INTERACTIONS; SURFACE AREA; SYNTHESIS; TRANSFORMATIONS; WEAK INTERACTIONS

Citation Formats

Jacobs, G., Ji, Y., Davis, B. H., Cronauer, D., Kropf, A. J., Marshall, C. L., Chemical Engineering, and Univ. of Kentucky. Fischer-tropsch synthesis: temperature programmed EXAFS/XANES investiation of the influence of support type, cobalt loading, and nobel metal promoter addition to the reduction behavior of cobalt oxide particles.. United States: N. p., 2007. Web. doi:10.1016/j.apcata.2007.07.027.
Jacobs, G., Ji, Y., Davis, B. H., Cronauer, D., Kropf, A. J., Marshall, C. L., Chemical Engineering, & Univ. of Kentucky. Fischer-tropsch synthesis: temperature programmed EXAFS/XANES investiation of the influence of support type, cobalt loading, and nobel metal promoter addition to the reduction behavior of cobalt oxide particles.. United States. doi:10.1016/j.apcata.2007.07.027.
Jacobs, G., Ji, Y., Davis, B. H., Cronauer, D., Kropf, A. J., Marshall, C. L., Chemical Engineering, and Univ. of Kentucky. Mon . "Fischer-tropsch synthesis: temperature programmed EXAFS/XANES investiation of the influence of support type, cobalt loading, and nobel metal promoter addition to the reduction behavior of cobalt oxide particles.". United States. doi:10.1016/j.apcata.2007.07.027.
@article{osti_947529,
title = {Fischer-tropsch synthesis: temperature programmed EXAFS/XANES investiation of the influence of support type, cobalt loading, and nobel metal promoter addition to the reduction behavior of cobalt oxide particles.},
author = {Jacobs, G. and Ji, Y. and Davis, B. H. and Cronauer, D. and Kropf, A. J. and Marshall, C. L. and Chemical Engineering and Univ. of Kentucky},
abstractNote = {TPR-XANES/EXAFS carried out using a novel multi-sample holder provided key information for verifying the nature of the chemical transformations occurring during cobalt Fischer-Tropsch synthesis catalyst activation in hydrogen. In the past, assumptions had to be made regarding the nature of the cobalt species present along the trajectory of a standard TPR experiment. The new technique directly provided insight into (a) the nature of the reduction process of cobalt oxide species and (b) the resulting cobalt crystallite size, as a function of the strength of the catalyst support interaction with the cobalt oxide species. A two-step reduction process involving Co{sub 3}O{sub 4} to CoO and CoO to Co{sup 0} transformations over standard calcined catalysts was observed and quantified over all catalysts exhibiting both weak interactions (e.g., Co/SiO{sub 2}) and strong interactions (e.g., Co/Al{sub 2}O{sub 3}) with the support. Noble metal promoter (e.g., Pt) addition strongly improved the reducibility of cobalt oxide species, most likely via a H{sub 2} dissociation and spillover mechanism. Increasing cobalt loading, on the other hand, led to a measurable, but lesser, improvement on reducibility, due to the larger resulting particle size that resulted in less surface contact with the support. Higher reduction temperatures were needed to effectively reduce cobalt oxide particles deposited on strongly interacting surfaces in comparison with unsupported Co{sub 3}O{sub 4} or only weakly interacting supported cobalt catalyst. Nevertheless, despite lower extents of reduction, the smaller resulting Co particles on the more strongly interacting catalysts generally led to higher Co{sup 0} active site densities. The addition of the noble metal promoter to strongly interacting supported catalyst significantly decreased the temperature required to reduce the cobalt oxides to Co{sup 0} particles; this allows one to take advantage of the higher Co{sup 0} surface areas arising from the combination of a smaller average Co{sup 0} particle size and a higher extent of reduction.},
doi = {10.1016/j.apcata.2007.07.027},
journal = {Appl. Catal. A},
number = 2007,
volume = 333,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}