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Title: Fischer–Tropsch synthesis: Effect of ammonia on supported cobalt catalysts

The effect of ammonia in syngas on the performance of various supported cobalt catalysts (i.e., Al 2O 3, TiO 2 and SiO 2) was investigated during Fischer-Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). The addition of ammonia (10 ppmv NH 3) caused a significant deactivation for all supported cobalt catalysts, but the rate of deactivation was higher for the silica-supported catalysts relative to the alumina and titania-supported catalysts used in this work. Ammonia addition had a positive effect on product selectivity (i.e., lower light gas products and higher C 5+) for alumina and titania-supported catalysts compared to ammonia free conditions, whereas, the addition of ammonia increased lighter hydrocarbon (C 1-C 4) products and decreased higher hydrocarbon (C 5+) selectivity compared to ammonia-free synthesis conditions for the silica-supported catalyst. For alumina and titania-supported catalysts, the activity almost recovered with mild in-situ hydrogen treatment of the ammonia exposed catalysts. For the silica-supported catalyst, the loss of activity is somewhat irreversible (i.e., cannot be regained after the mild hydrogen treatment). Addition of ammonia led to a significant loss in BET surface area and changes in pore diameter (consistent with pore collapse of a fraction of pores into the microporous rangemore » as described in the literature), as well as formation of catalytically inactive cobalt support compounds for the silica-supported catalyst. On the other hand, the pore characteristics of alumina and titania-supported catalysts were not significantly changed. In conclusion, XANES results of the ammonia exposed silica-supported catalysts further confirm the formation of cobalt-support compounds (cobalt silicates).« less
Authors:
 [1] ;  [1] ; ORCiD logo [1] ;  [2] ;  [1]
  1. Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
Publication Date:
Report Number(s):
BNL-112618-2016-JA
Journal ID: ISSN 0021-9517
Grant/Contract Number:
SC0012704; AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 337; Journal Issue: C; Journal ID: ISSN 0021-9517
Publisher:
Elsevier
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Fischer–Tropsch synthesis; Effect of ammonia; Supported cobalt catalysts; EXAFS/XANES; Deactivation; Product selectivity
OSTI Identifier:
1340391
Alternate Identifier(s):
OSTI ID: 1341146