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dc.contributor.authorMa, Wenping
dc.contributor.authorJacobs, Gary
dc.contributor.authorSparks, Dennis E.
dc.contributor.authorPendyala, Venkat Ramana Rao
dc.contributor.authorHopps, Shelley D.
dc.contributor.authorThomas, Gerald A.
dc.contributor.authorHamdeh, Hussein H.
dc.contributor.authorMacLennan, Aimee
dc.contributor.authorHu, Yongfeng
dc.contributor.authorDavis, Burtron H.
dc.identifier.citationMa, Wenping; Jacobs, Gary; Sparks, Dennis E.; Pendyala, Venkat Ramana Rao; Hopps, Shelley D.; Thomas, Gerald A.; Hamdeh, Hussein H.; MacLennan, Aimee; Hu, Yongfeng; Davis, Burtron H. 2015. Fischer-Tropsch synthesis: effect of ammonia in syngas on the Fischer-Tropsch synthesis performance of a precipitated iron catalyst. Journal of Catalysis, vol. 326:pp 149–160en_US
dc.descriptionClick on the DOI link to access the article (may not be free).en_US
dc.description.abstractThe effect of ammonia in syngas on the Fischer-Tropsch synthesis (FTS) reaction over 100Fe/5.1Si/2.0Cu/3.0K catalyst was studied at 220-270 degrees C and 1.3 MPa using a 1-L slurry phase reactor. The ammonia added in syngas originated from adding ammonia gas, ammonium hydroxide solution, or ammonium nitrate (AN) solution. A wide range of ammonia concentrations (i.e., 0.1-400 ppm) was examined for several hundred hours. The Fe catalysts withdrawn at different times (i.e., after activation by carburization in CO, before and after co-feeding contaminants, and at the end of run) were characterized by ICP-OES, XRD, Mossbauer spectroscopy, and synchrotron methods (e.g., XANES, EXAFS) in order to explore possible changes in the chemical structure and phases of the Fe catalyst with time; in this way, the deactivation mechanism of the Fe catalyst by poisoning could be assessed. Adding up to 200 ppmw (wt. NH3/av. Wt. feed) ammonia in syngas did not significantly deactivate the Fe catalyst or alter selectivities toward CH4, C5+, CO2, C-4-olefin, and 1-C-4 olefin, but increasing the ammonia level (in the AN form) to 400 ppm rapidly deactivated the Fe catalyst and simultaneously changed the product selectivities. The results of ICP-OES, XRD, and Mossbauer spectroscopy did not display any evidence for the retention of a nitrogen-containing compound on the used catalyst that could explain the deactivation (e.g., adsorption, site blocking). Instead, Mossbauer spectroscopy results revealed that a significant fraction of iron carbides transformed into iron magnetite during co-feeding high concentrations of AN, suggesting that oxidation of iron carbides occurred and served as a major deactivation path in that case. Oxidation of chi-Fe5C2 to magnetite during co-feeding high concentrations of AN was further confirmed by XRD analysis and by the application of synchrotron methods (e.g., XANES, EXAFS). It is postulated that AN oxidized chi-Fe5C2 during FTS via its thermal dissociation product, HNO3. This conclusion is further supported by reaction tests with co-feeding of similar concentrations of HNO3. Additional oxidation routes of iron carbide to magnetite by HNO3 and/or by its thermal decomposition products are also considered: Fe5C2 + NOx (and/or HNO3) -> Fe3O4. In this study, ion chromatography detected that 50-80% HNO3 directly added or dissociated from AN eventually converted to ammonia during or after its oxidation of iron carbide, resulting from the reduction of NOx (NOx + H-2 + CO -> NH3 + CO2 + N-2 + H2O) by H-2 and/or CO.en_US
dc.description.sponsorshipThis work was made possible by financial support from U.S. DOE contract number of DE-FC26-08NT0006368, and the Commonwealth of Kentucky. Research described in this paper was performed in part at the Canadian Light Source, which is funded by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the National Research Council Canada, the Canadian Institutes of Health Research, the Government of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan.en_US
dc.publisherElsevier B.V.en_US
dc.relation.ispartofseriesJournal of Catalysis;v.326
dc.subjectFischer-Tropsch synthesisen_US
dc.subjectFe catalysten_US
dc.subjectBiomass-to-liquids (BTL)en_US
dc.subjectSlurry phase reactoren_US
dc.subjectAmmonia (NH3)en_US
dc.subjectAmmonium nitrate (NH4NO3)en_US
dc.subjectNitric acid (HNO3)en_US
dc.subjectMossbauer spectroscopyen_US
dc.titleFischer-Tropsch synthesis: Effect of ammonia in syngas on the Fischer-Tropsch synthesis performance of a precipitated iron catalysten_US
dc.rights.holderCopyright 2015 Elsevier

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