期刊
FUEL PROCESSING TECHNOLOGY
卷 92, 期 12, 页码 2353-2359出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.fuproc.2011.08.011
关键词
Fischer-Tropsch synthesis; Iron-based catalyst; Reducing agents; Iron carbides; Mossbauer effect spectroscopy
资金
- National Key Basic Research Program of China [2007CB216401, 2011BAD22B06]
- Synfuels China Co., Ltd.
Effects of reducing agents on the textural properties and bulk/surface phase compositions of a precipitated iron-manganese catalyst were investigated by N-2-physisorption, X-ray photoelectron spectroscopy (XRD), Mossbauer effect spectroscopy (MES), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (LRS). Fischer-Tropsch synthesis (FTS) was performed in a slurry-phase continuously stirred tank reactor. The characterization results indicated that the hematite in the fresh catalyst was converted mainly to magnetite in H-2 atmosphere without the formation of intermediate metallic iron. Large amounts of Fe3O4 and small amounts of epsilon'-Fe2.2C and chi-Fe2.5C were formed after syngas pretreatment. In contrast, CO activation led to the formation of large amounts of chi-Fe2.5C and carbonaceous species on the surface of magnetite. In the FTS reaction, the CO-activated catalyst presented the highest initial activity compared to the H-2 and syngas-reduced catalysts, and remained unchanged in the activity following the transformation of iron carbides to Fe3O4. Furthermore, the FTS activity of the H-2-reduced catalyst increased gradually accompanied with the conversion of magnetite to iron carbides. All of the results suggested that the formation of iron carbides (especially for chi-Fe2.5C) on the surface layers provides probably the active sites for FTS, whereas the Fe3O4 formed plays a negligible role in the FTS activity. (C) 2011 Elsevier B.V. All rights reserved.
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