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Title: SBA-15-supported iron catalysts for Fischer-Tropsch production of diesel fuel

Abstract

Iron supported on SBA-15, a mesoporous structured silica, has been developed as a catalyst for the Fischer-Tropsch synthesis of hydrocarbons. The catalysts retain the high surface area of the support, {approximately}500 m{sup 2}/g, average pore size, and pore volume. Inclusion of aluminum into the SBA-15 did not significantly alter these parameters. XRD, XAFS, and Moessbauer spectroscopies were used to characterize the catalyst before and after being subjected to the reaction conditions. Prior to reaction, the iron was distributed among {alpha}-Fe{sub 2}O{sub 3}, ferrihydrite, and minor {gamma}Fe{sub 2}O{sub 3}. After reaction, the iron phases detected were nonmagnetic iron oxides, iron carbide, and metallic iron. The length of the induction period typically seen with iron-based F-T catalysts was strongly dependent on the amount of aluminum present in the catalyst. With no aluminum, the induction period lasted about 25 h, whereas the induction period decreased to less than 5 h with an Al:Si mass ratio of 0.010. A further increase in aluminum content lengthened the induction period, but always remained less than that without aluminum. Catalyst activity and product selectivity were also strongly dependent on aluminum content with the maximum diesel fuel fraction, C{sub 11+}, occurring with the Al:Si ratio of 0.010 andmore » a CO conversion of 37%. The small concentration of aluminum may serve to increase the rate of iron carbide formation, whereas higher concentrations may begin to inhibit the rate. 23 refs., 6 figs., 2 tabs.« less

Authors:
; ; ; ; ; ;  [1]
  1. University of Utah, Salt Lake City, UT (United States). Department of Chemistry
Publication Date:
OSTI Identifier:
20838266
Resource Type:
Journal Article
Resource Relation:
Journal Name: Energy and Fuels; Journal Volume: 20; Journal Issue: 6; Other Information: eyring@chem.utah.edu
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; CATALYST SUPPORTS; SILICA; IRON; CATALYSTS; FISCHER-TROPSCH SYNTHESIS; DIESEL FUELS; CATALYTIC EFFECTS

Citation Formats

Dae Jung Kim, Brian C. Dunn, Frank Huggins, Gerald P. Huffman, Min Kang, Jae Eui Yie, and Edward M. Eyring. SBA-15-supported iron catalysts for Fischer-Tropsch production of diesel fuel. United States: N. p., 2006. Web.
Dae Jung Kim, Brian C. Dunn, Frank Huggins, Gerald P. Huffman, Min Kang, Jae Eui Yie, & Edward M. Eyring. SBA-15-supported iron catalysts for Fischer-Tropsch production of diesel fuel. United States.
Dae Jung Kim, Brian C. Dunn, Frank Huggins, Gerald P. Huffman, Min Kang, Jae Eui Yie, and Edward M. Eyring. Fri . "SBA-15-supported iron catalysts for Fischer-Tropsch production of diesel fuel". United States. doi:.
@article{osti_20838266,
title = {SBA-15-supported iron catalysts for Fischer-Tropsch production of diesel fuel},
author = {Dae Jung Kim and Brian C. Dunn and Frank Huggins and Gerald P. Huffman and Min Kang and Jae Eui Yie and Edward M. Eyring},
abstractNote = {Iron supported on SBA-15, a mesoporous structured silica, has been developed as a catalyst for the Fischer-Tropsch synthesis of hydrocarbons. The catalysts retain the high surface area of the support, {approximately}500 m{sup 2}/g, average pore size, and pore volume. Inclusion of aluminum into the SBA-15 did not significantly alter these parameters. XRD, XAFS, and Moessbauer spectroscopies were used to characterize the catalyst before and after being subjected to the reaction conditions. Prior to reaction, the iron was distributed among {alpha}-Fe{sub 2}O{sub 3}, ferrihydrite, and minor {gamma}Fe{sub 2}O{sub 3}. After reaction, the iron phases detected were nonmagnetic iron oxides, iron carbide, and metallic iron. The length of the induction period typically seen with iron-based F-T catalysts was strongly dependent on the amount of aluminum present in the catalyst. With no aluminum, the induction period lasted about 25 h, whereas the induction period decreased to less than 5 h with an Al:Si mass ratio of 0.010. A further increase in aluminum content lengthened the induction period, but always remained less than that without aluminum. Catalyst activity and product selectivity were also strongly dependent on aluminum content with the maximum diesel fuel fraction, C{sub 11+}, occurring with the Al:Si ratio of 0.010 and a CO conversion of 37%. The small concentration of aluminum may serve to increase the rate of iron carbide formation, whereas higher concentrations may begin to inhibit the rate. 23 refs., 6 figs., 2 tabs.},
doi = {},
journal = {Energy and Fuels},
number = 6,
volume = 20,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • Iron supported on SBA-15, a mesoporous structured silica, has been developed as a catalyst for the Fischer-Tropsch synthesis of hydrocarbons. The catalysts retain the high surface area of the support, {approx}500 m{sup 2}/g, average pore size, and pore volume. Inclusion of aluminum into the SBA-15 did not significantly alter these parameters. XRD, XAFS, and Moessbauer spectroscopies were used to characterize the catalyst before and after being subjected to the reaction conditions. Prior to reaction, the iron was distributed among {alpha}-Fe{sub 2}O{sub 3}3, ferrihydrite, and minor {gamma}-Fe{sub 2}O{sub 3}. After reaction, the iron phases detected were nonmagnetic iron oxides, iron carbide,more » and metallic iron. The length of the induction period typically seen with iron-based F-T catalysts was strongly dependent on the amount of aluminum present in the catalyst. With no aluminum, the induction period lasted about 25 h, whereas the induction period decreased to less than 5 h with an Al:Si mass ratio of 0.010. A further increase in aluminum content lengthened the induction period, but always remained less than that without aluminum. Catalyst activity and product selectivity were also strongly dependent on aluminum content with the maximum diesel fuel fraction, C{sub 11+}, occurring with the Al:Si ratio of 0.010 and a CO conversion of 37%. The small concentration of aluminum may serve to increase the rate of iron carbide formation, whereas higher concentrations may begin to inhibit the rate.« less
  • A series of silylated Co/SBA-15 catalysts were prepared via the reaction of surface Si-OH of SBA-15 with hexamethyldisilazane (HMDS) under anhydrous, vapor-phase conditions, and then characterized by FT-IR, N{sub 2} physisorption, TG, XRD, and TPR-MS. The results showed that organic modification led to a silylated SBA-15 surface composed of stable hydrophobic Si-(CH{sub 3}){sub 3} species even after calcinations and H{sub 2} reduction at 673 K. Furthermore, the hydrophobic surface strongly influenced both metal dispersion and reducibility. Compared with non-silylated Co/SBA, Co/S-SBA (impregnation after silylation) showed a high activity, due to the better cobalt reducibility on the hydrophobic support. However, S-Co/SBAmore » (silylation after impregnation) had the lowest FT activity among all the catalysts, due to the lower cobalt reducibility along with the steric hindrance of grafted -Si(CH{sub 3}){sub 3} for the re-adsorption of {alpha}-olefins. -- Graphical abstract: The silylation of an SBA-15 before cobalt impregnation enhanced the reducibility of cobalt oxides on an SBA-15-supported cobalt catalyst and consequently increased the catalytic activity for Fischer-Tropsch synthesis. Display Omitted« less
  • Iron aerogels, potassium-doped iron aerogels, and potassium-doped iron xerogels have been synthesized and characterized and their catalytic activity in the Fischer-Tropsch (F-T) reaction has been studied. Iron aerogels and xerogels were synthesized by polycondensation of an ethanolic solution of iron(III) chloride hexahydrate with propylene oxide which acts as a proton scavenger for the initiation of hydrolysis and polycondensation. Potassium was incorporated in the iron aerogel and iron xerogel by adding aqueous K{sub 2}CO{sub 3} to the ethanolic solutions of the Fe(III) precursor prior to addition of propylene oxide. Fischer-Tropsch activities of the catalysts were tested in a fixed bed reactormore » at a pressure of 100 psi with a H{sub 2}:CO ratio of 2:1. Iron aerogels were found to be active for F-T synthesis, and their F-T activities increased on addition of a K containing promoter. Moessbauer spectroscopic data are consistent with an open, nonrigid iron(III) aerogel structure progressing to an iron carbide/metallic iron catalyst via agglomeration as the F-T synthesis proceeds in the course of a 35 h fixed bed reaction test.« less
  • The chemisorption properties of unpromoted and potassium-promoted iron catalysts were studied by infrared spectroscopy using nitric oxide as a probe molecule. The catalysts, supported on alumina, are active in the Fischer-Tropsch synthesis, producing increasing fractions of long-chain hydrocarbons and olefins with increasing alkali content. The NO chemisorption spectra on the reduced catalysts are complex, but major features include bands indicative of Fe/sup 2 +/ and Fe/sup 0/ sites. On oxidized catalysts, the band ascribed to Fe/sup 0/ disappears, while bands corresponding to more oxidized species such as nitrates or nitrites are evident. With increasing alkali loading, the major NO bandsmore » exhibit a shift to lower frequencies. With the reduced catalysts, increasing the potassium loading results in a decrease in the Fe/sup 0/ band and an increase in the more oxidized NO species. In the presence of gas-phase H/sub 2/, the NO band corresponding to Fe/sup 0/ is substantially greater with these same catalysts. The results are interpreted in terms of the electron donor properties of potassium on the iron catalyst surface. It is suggested that a delicate balance exists between associative and dissociative chemisorption of NO with these catalysts.« less