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Burtron H. Davis - One of the best experts on this subject based on the ideXlab platform.
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Fischer-Tropsch Reactors
Studies in Surface Science and Catalysis, 2020Co-Authors: A P Steynberg, Burtron H. Davis, B B BremanAbstract:Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) Reactor in commercial use at present. Three broad categories of catalyst are used in these Reactors. The four types of Reactor are: circulating fluidized bed Reactor, fluidized bed Reactor, tubular fixed bed Reactor, and slurry phase Reactor. It discusses that the fluidized bed Reactors operate in the temperature range 320oC to 350oC. This temperature range is 100oC higher than the typical operating temperature range used with the Reactors of around 220oC to 250oC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the Reactors on the left hand side and the term low temperature FT is used to describe the Reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT Reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT Reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.
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Fischer–Tropsch Synthesis: Influence of Acid Treatment and Preparation Method on Carbon Nanotube Supported Ruthenium Catalysts
Industrial & Engineering Chemistry Research, 2017Co-Authors: Venkat Ramana Rao Pendyala, Gary Jacobs, Wilson D. Shafer, Uschi M. Graham, Michela Martinelli, Liang Kong, Burtron H. DavisAbstract:The influences of nitric acid treatment on a carbon nanotube (CNT) support and the preparation method, incipient wetness impregnation (IWI) versus chemical vapor deposition (CVD), on catalytic performance during Fischer–Tropsch (FT) synthesis were examined using a slurry phase Reactor. Acid treated CNT (ACNT) supported Ru catalysts exhibited higher activities compared to Ru supported on untreated CNTs (UCNTs). The acid-treated CVD catalyst had higher initial CO conversion (smaller average Ru particle size) but sintered more due to a greater tendency for Ru to be deposited exterior to CNT channels relative to IWI. After the initial decline and leveling off period, the ACNT IWI catalyst had the highest steady activity among the catalysts tested. The ACNT IWI catalyst also displayed greater oxygenate selectivity (∼17%) compared to ACNT CVD (∼12%) and UCNT IWI (∼10%) catalysts at similar conversions. Acid treatment created adsorption sites on the CNT surface that anchor Ru precursors and promote CO insertion ...
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Effect of H_2S in Syngas on the Fischer–Tropsch Synthesis Performance of a 0.5%Pt–25%Co–Al_2O_3 Catalyst
Catalysis Letters, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Burtron H. DavisAbstract:The effect of 1.0 ppm H_2S in the syngas feed on initial activity and selectivity of a 0.5%Pt–25%Co/Al_2O_3 catalyst was studied by comparing the catalyst performance under H_2S and sulfur free conditions. The reaction tests were performed using a 1-L slurry phase Reactor for 141–212 h under constant reaction conditions: 220 °C, 2.0 MPa, H_2/CO = 2.0 and 6.0 Nl/g-cat/h. In the H_2S poisoning test, an H_2S in N_2 gas mixture was added to the syngas feed (1.0 ppm) after running the Fischer–Tropsch synthesis (FTS) reaction for ca. 6.0 h; as such, the impact of H_2S on the initial deactivation of the cobalt catalyst (unsteady state) was successfully assessed. The used catalysts were characterized by XANES to investigate if Co–S surface species were formed during the deactivation. The initial deactivation under 1.0 ppm H_2S condition was significantly higher (by 2.0–2.4 times) than that under clean conditions. CH_4 selectivity increased substantially and C_5+ selectivity decreased greatly with time regardless of whether H_2S was added or not; however, the addition of H_2S accelerated the changes in the hydrocarbon selectivities, which were likely caused by the sharp deactivation of the catalyst in the presence of H_2S. After co-feeding the sulfur for 141 h, a comparison was made at similar conversions by adjusting space velocity; the sulfur pretreated cobalt catalysts favored heavier hydrocarbons (C_5+) formation and suppressed lower hydrocarbon formation. The addition of H_2S to the feed increased CO_2 selectivity and the secondary reaction of 1-olefins. The XANES results revealed that surface species involving Co–S bonding formed on the cobalt catalyst after exposure to H_2S during FTS. This was likely the primary reason for the abnormal selectivity trends observed during and after the deactivation of the catalyst by sulfur. This study points out a possible approach to increase the selectivity to heavy hydrocarbons by properly sulfiding the cobalt catalyst prior to the FTS reaction. Graphical Abstract
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Effect of H 2 S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst
Applied Catalysis A-general, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Shelley D. Hopps, Burtron H. DavisAbstract:Abstract The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270 °C, 1.3 MPa, H2/CO = 0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase Reactor. The used Fe catalysts were characterized by XRD, Mossbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1 ppm H2S in the feed. Co-feeding of 0.1 ppm H2S in syngas for 70 h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2 ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50 ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270 °C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260 °C and increased further to 13.5 at 230 °C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mossbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230 °C), and similar M/S ratios (13.5–15.0) were obtained.
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Fischer-Tropsch synthesis: Effect of ammonia in syngas on the Fischer-Tropsch synthesis performance of a precipitated iron catalyst
Journal of Catalysis, 2015Co-Authors: Wenping Ma, Gary Jacobs, Gerald A. Thomas, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Yongfeng Hu, Shelley D. Hopps, Aimee Maclennan, Burtron H. DavisAbstract:Abstract The 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 °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. NH 3 /av. Wt. feed) ammonia in syngas did not significantly deactivate the Fe catalyst or alter selectivities toward CH 4 , C 5+ , CO 2 , 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 χ-Fe 5 C 2 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 χ-Fe 5 C 2 during FTS via its thermal dissociation product, HNO 3 . This conclusion is further supported by reaction tests with co-feeding of similar concentrations of HNO 3 . Additional oxidation routes of iron carbide to magnetite by HNO 3 and/or by its thermal decomposition products are also considered: Fe 5 C 2 + NO x (and/or HNO 3 ) → Fe 3 O 4 . In this study, ion chromatography detected that 50–80% HNO 3 directly added or dissociated from AN eventually converted to ammonia during or after its oxidation of iron carbide, resulting from the reduction of NO x (NO x + H 2 + CO → NH 3 + CO 2 + N 2 + H 2 O) by H 2 and/or CO.
A P Steynberg - One of the best experts on this subject based on the ideXlab platform.
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Fischer-Tropsch Reactors
Studies in Surface Science and Catalysis, 2020Co-Authors: A P Steynberg, Burtron H. Davis, B B BremanAbstract:Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) Reactor in commercial use at present. Three broad categories of catalyst are used in these Reactors. The four types of Reactor are: circulating fluidized bed Reactor, fluidized bed Reactor, tubular fixed bed Reactor, and slurry phase Reactor. It discusses that the fluidized bed Reactors operate in the temperature range 320oC to 350oC. This temperature range is 100oC higher than the typical operating temperature range used with the Reactors of around 220oC to 250oC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the Reactors on the left hand side and the term low temperature FT is used to describe the Reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT Reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT Reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.
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Intensification of commercial slurry phase Reactors
Studies in Surface Science and Catalysis, 2020Co-Authors: Alex Vogela, A P Steynberg, B B BremanAbstract:Publisher Summary While air separation and synthesis gas generation remain the main contributors to the capital cost of the GTL process units, capital savings can also be achieved in synthesis gas conversion. Improvements in Fischer–Tropsch Reactor design allows increased production capacity from the same Reactor shell size or equivalent production capacity from smaller Reactors through process intensification while maintaining or improving selectivity and overall synthesis gas conversion. The manufacture of large-scale Reactors is costly with a limited number of suppliers who have the capacity to produce such vessels. This chapter focuses on the potential of the Fischer–Tropsch slurry phase Reactor to contribute to cost reductions per barrel of product through Reactor intensification. The cost reduction could be realized through a combination of a lower material and construction cost per barrel of product produced, as well as having access to a larger pool of potential manufacturers. Opportunities will be created to standardize certain components of Reactor manufacture in partnership with preferred suppliers. A further benefit is the ability to match the FT Reactor capacity to the increasing maximum capacity for vendor-supplied air separation units and synthesis gas-generation units. Single train capacities of ca. 7000 ton/day oxygen are expected to be achievable in the future, which corresponds to a FT Reactor capacity of ca. 40,000 bpd.
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Chapter 2 - Fischer-Tropsch Reactors
Studies in Surface Science and Catalysis, 2004Co-Authors: A P Steynberg, B H Davis, Mark E. Dry, B B BremanAbstract:Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) Reactor in commercial use at present. Three broad categories of catalyst are used in these Reactors. The four types of Reactor are: circulating fluidized bed Reactor, fluidized bed Reactor, tubular fixed bed Reactor, and slurry phase Reactor. It discusses that the fluidized bed Reactors operate in the temperature range 320ºC to 350ºC. This temperature range is 100ºC higher than the typical operating temperature range used with the Reactors of around 220ºC to 250ºC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the Reactors on the left hand side and the term low temperature FT is used to describe the Reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT Reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT Reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.
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Low temperature Fischer–Tropsch synthesis from a Sasol perspective
Applied Catalysis A-general, 1999Co-Authors: R. L. Espinoza, A P Steynberg, BARBARA JAGER, A. C. VoslooAbstract:Abstract The characteristics of a slurry phase Reactor are contrasted with those of a conventional tubular fixed bed Reactor (TFBR) for the conversion of synthesis gas to long chain hydrocarbons. Hydrodynamic information needed for the design of a commercial scale slurry phase Fischer–Tropsch (FT) Reactor were obtained from experiments carried out on a 1 m internal diameter pilot plant Reactor. The kinetics, selectivities and deactivation mechanisms of Fe and supported Co FT catalysts are compared for both slurry phase and fixed bed operation. The combined advantages of the slurry phase Reactor and a very active Co catalyst create the opportunity to convert remote natural gas to high quality middle distillates in a cost effective manner.
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Low temperature Fischer-Tropsch synthesis from a Sasol perspective
Applied Catalysis A: General, 1999Co-Authors: R. L. Espinoza, A P Steynberg, BARBARA JAGER, A. C. VoslooAbstract:The characteristics of a slurry phase Reactor are contrasted with those of a conventional tubular fixed bed Reactor (TFBR) for the conversion of synthesis gas to long chain hydrocarbons. Hydrodynamic information needed for the design of a commercial scale slurry phase Fischer-Tropsch (FT) Reactor were obtained from experiments carried out on a 1 m internal diameter pilot plant Reactor. The kinetics, selectivities and deactivation mechanisms of Fe and supported Co FT catalysts are compared for both slurry phase and fixed bed operation. The combined advantages of the slurry phase Reactor and a very active Co catalyst create the opportunity to convert remote natural gas to high quality middle distillates in a cost effective manner. © 1999 Elsevier Science B.V. All rights reserved.
Wenping Ma - One of the best experts on this subject based on the ideXlab platform.
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Effect of H_2S in Syngas on the Fischer–Tropsch Synthesis Performance of a 0.5%Pt–25%Co–Al_2O_3 Catalyst
Catalysis Letters, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Burtron H. DavisAbstract:The effect of 1.0 ppm H_2S in the syngas feed on initial activity and selectivity of a 0.5%Pt–25%Co/Al_2O_3 catalyst was studied by comparing the catalyst performance under H_2S and sulfur free conditions. The reaction tests were performed using a 1-L slurry phase Reactor for 141–212 h under constant reaction conditions: 220 °C, 2.0 MPa, H_2/CO = 2.0 and 6.0 Nl/g-cat/h. In the H_2S poisoning test, an H_2S in N_2 gas mixture was added to the syngas feed (1.0 ppm) after running the Fischer–Tropsch synthesis (FTS) reaction for ca. 6.0 h; as such, the impact of H_2S on the initial deactivation of the cobalt catalyst (unsteady state) was successfully assessed. The used catalysts were characterized by XANES to investigate if Co–S surface species were formed during the deactivation. The initial deactivation under 1.0 ppm H_2S condition was significantly higher (by 2.0–2.4 times) than that under clean conditions. CH_4 selectivity increased substantially and C_5+ selectivity decreased greatly with time regardless of whether H_2S was added or not; however, the addition of H_2S accelerated the changes in the hydrocarbon selectivities, which were likely caused by the sharp deactivation of the catalyst in the presence of H_2S. After co-feeding the sulfur for 141 h, a comparison was made at similar conversions by adjusting space velocity; the sulfur pretreated cobalt catalysts favored heavier hydrocarbons (C_5+) formation and suppressed lower hydrocarbon formation. The addition of H_2S to the feed increased CO_2 selectivity and the secondary reaction of 1-olefins. The XANES results revealed that surface species involving Co–S bonding formed on the cobalt catalyst after exposure to H_2S during FTS. This was likely the primary reason for the abnormal selectivity trends observed during and after the deactivation of the catalyst by sulfur. This study points out a possible approach to increase the selectivity to heavy hydrocarbons by properly sulfiding the cobalt catalyst prior to the FTS reaction. Graphical Abstract
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Effect of H 2 S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst
Applied Catalysis A-general, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Shelley D. Hopps, Burtron H. DavisAbstract:Abstract The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270 °C, 1.3 MPa, H2/CO = 0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase Reactor. The used Fe catalysts were characterized by XRD, Mossbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1 ppm H2S in the feed. Co-feeding of 0.1 ppm H2S in syngas for 70 h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2 ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50 ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270 °C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260 °C and increased further to 13.5 at 230 °C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mossbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230 °C), and similar M/S ratios (13.5–15.0) were obtained.
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Fischer-Tropsch synthesis: Effect of ammonia in syngas on the Fischer-Tropsch synthesis performance of a precipitated iron catalyst
Journal of Catalysis, 2015Co-Authors: Wenping Ma, Gary Jacobs, Gerald A. Thomas, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Yongfeng Hu, Shelley D. Hopps, Aimee Maclennan, Burtron H. DavisAbstract:Abstract The 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 °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. NH 3 /av. Wt. feed) ammonia in syngas did not significantly deactivate the Fe catalyst or alter selectivities toward CH 4 , C 5+ , CO 2 , 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 χ-Fe 5 C 2 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 χ-Fe 5 C 2 during FTS via its thermal dissociation product, HNO 3 . This conclusion is further supported by reaction tests with co-feeding of similar concentrations of HNO 3 . Additional oxidation routes of iron carbide to magnetite by HNO 3 and/or by its thermal decomposition products are also considered: Fe 5 C 2 + NO x (and/or HNO 3 ) → Fe 3 O 4 . In this study, ion chromatography detected that 50–80% HNO 3 directly added or dissociated from AN eventually converted to ammonia during or after its oxidation of iron carbide, resulting from the reduction of NO x (NO x + H 2 + CO → NH 3 + CO 2 + N 2 + H 2 O) by H 2 and/or CO.
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Fischer-Tropsch synthesis: Effects of hydrohalic acids in syngas on a precipitated iron catalyst
ACS Catalysis, 2015Co-Authors: Wenping Ma, Gary Jacobs, Gerald A. Thomas, Wilson D. Shafer, Dennis E. Sparks, Hussein H. Hamdeh, Burtron H. DavisAbstract:The current investigation was undertaken to identify limits of hydrohalic acid (HX, X = F, Cl, Br) impurities in syngas and shed light on the mechanism of HX poisoning of a 100 Fe/5.1 Si/2 Cu/3 K FTS catalyst under industrially relevant conditions using a 1-L Slurry-Phase Reactor. Co-feeding
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Fischer–Tropsch synthesis. Effect of alkali, bicarbonate and chloride addition on activity and selectivity
Catalysis Today, 2013Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Dennis E. Sparks, Jungshik Kang, Muthu Kumaran Gnanamani, Venkat Ramana Rao Pendyala, Robert A. Keogh, Uschi M. Graham, Gerald A. ThomasAbstract:Abstract The sensitivity of 100Fe/5.1Si/2Cu/3K Fischer–Tropsch synthesis (FTS) catalyst to the impurities of KCl, NaCl, KHCO3 and NaHCO3 in syngas (0.1–100 ppm) was studied in a slurry phase Reactor at 533.2 or 543.2 K, H2/CO = 0.67–0.77, 1.31 MPa and 10 NL/g-cat/h. The impurities were co-fed with syngas, and the influence of each contaminant concentration on Fe catalyst behavior was examined for 72–144 h. The presence of up to 40 ppmw halide compounds (NaCl and KCl) or alkali bicarbonates (NaHCO3 and KHCO3) in syngas at 543.2 K or up to 100 ppm of NaCl and KCl at 533.2 K had little impact on the Fe catalyst activity and selectivities to CH4, C5+ and C4 olefin and 1-olefin during 400 h (543.2 K) or 1400 h testing (533.2 K). CO2 selectivity slightly increased after feeding the impurity-containing solutions, which was due to enhanced water gas shift (WGS). ICP results for the Fe catalysts at the end of the FTS reaction test and of the FTS products (i.e., water, oil or wax phase) indicate that the impurity ions (K+, Na+ or Cl−) introduced were present in all phases of the FTS products, the greater part being retained in the wax. Therefore, the contaminant ions (i.e., Na, K or Cl) in the water solution injected appear to not strongly adsorb on the Fe catalyst surface at typical FTS conditions in the slurry phase Reactor. This is assumed to be responsible for the lack of change in FTS behavior for the Fe catalyst using the contaminants studied.
B B Breman - One of the best experts on this subject based on the ideXlab platform.
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Intensification of commercial slurry phase Reactors
Studies in Surface Science and Catalysis, 2020Co-Authors: Alex Vogela, A P Steynberg, B B BremanAbstract:Publisher Summary While air separation and synthesis gas generation remain the main contributors to the capital cost of the GTL process units, capital savings can also be achieved in synthesis gas conversion. Improvements in Fischer–Tropsch Reactor design allows increased production capacity from the same Reactor shell size or equivalent production capacity from smaller Reactors through process intensification while maintaining or improving selectivity and overall synthesis gas conversion. The manufacture of large-scale Reactors is costly with a limited number of suppliers who have the capacity to produce such vessels. This chapter focuses on the potential of the Fischer–Tropsch slurry phase Reactor to contribute to cost reductions per barrel of product through Reactor intensification. The cost reduction could be realized through a combination of a lower material and construction cost per barrel of product produced, as well as having access to a larger pool of potential manufacturers. Opportunities will be created to standardize certain components of Reactor manufacture in partnership with preferred suppliers. A further benefit is the ability to match the FT Reactor capacity to the increasing maximum capacity for vendor-supplied air separation units and synthesis gas-generation units. Single train capacities of ca. 7000 ton/day oxygen are expected to be achievable in the future, which corresponds to a FT Reactor capacity of ca. 40,000 bpd.
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Fischer-Tropsch Reactors
Studies in Surface Science and Catalysis, 2020Co-Authors: A P Steynberg, Burtron H. Davis, B B BremanAbstract:Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) Reactor in commercial use at present. Three broad categories of catalyst are used in these Reactors. The four types of Reactor are: circulating fluidized bed Reactor, fluidized bed Reactor, tubular fixed bed Reactor, and slurry phase Reactor. It discusses that the fluidized bed Reactors operate in the temperature range 320oC to 350oC. This temperature range is 100oC higher than the typical operating temperature range used with the Reactors of around 220oC to 250oC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the Reactors on the left hand side and the term low temperature FT is used to describe the Reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT Reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT Reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.
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Chapter 2 - Fischer-Tropsch Reactors
Studies in Surface Science and Catalysis, 2004Co-Authors: A P Steynberg, B H Davis, Mark E. Dry, B B BremanAbstract:Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) Reactor in commercial use at present. Three broad categories of catalyst are used in these Reactors. The four types of Reactor are: circulating fluidized bed Reactor, fluidized bed Reactor, tubular fixed bed Reactor, and slurry phase Reactor. It discusses that the fluidized bed Reactors operate in the temperature range 320ºC to 350ºC. This temperature range is 100ºC higher than the typical operating temperature range used with the Reactors of around 220ºC to 250ºC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the Reactors on the left hand side and the term low temperature FT is used to describe the Reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT Reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT Reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.
Gary Jacobs - One of the best experts on this subject based on the ideXlab platform.
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Fischer–Tropsch Synthesis: Influence of Acid Treatment and Preparation Method on Carbon Nanotube Supported Ruthenium Catalysts
Industrial & Engineering Chemistry Research, 2017Co-Authors: Venkat Ramana Rao Pendyala, Gary Jacobs, Wilson D. Shafer, Uschi M. Graham, Michela Martinelli, Liang Kong, Burtron H. DavisAbstract:The influences of nitric acid treatment on a carbon nanotube (CNT) support and the preparation method, incipient wetness impregnation (IWI) versus chemical vapor deposition (CVD), on catalytic performance during Fischer–Tropsch (FT) synthesis were examined using a slurry phase Reactor. Acid treated CNT (ACNT) supported Ru catalysts exhibited higher activities compared to Ru supported on untreated CNTs (UCNTs). The acid-treated CVD catalyst had higher initial CO conversion (smaller average Ru particle size) but sintered more due to a greater tendency for Ru to be deposited exterior to CNT channels relative to IWI. After the initial decline and leveling off period, the ACNT IWI catalyst had the highest steady activity among the catalysts tested. The ACNT IWI catalyst also displayed greater oxygenate selectivity (∼17%) compared to ACNT CVD (∼12%) and UCNT IWI (∼10%) catalysts at similar conversions. Acid treatment created adsorption sites on the CNT surface that anchor Ru precursors and promote CO insertion ...
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Effect of H_2S in Syngas on the Fischer–Tropsch Synthesis Performance of a 0.5%Pt–25%Co–Al_2O_3 Catalyst
Catalysis Letters, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Burtron H. DavisAbstract:The effect of 1.0 ppm H_2S in the syngas feed on initial activity and selectivity of a 0.5%Pt–25%Co/Al_2O_3 catalyst was studied by comparing the catalyst performance under H_2S and sulfur free conditions. The reaction tests were performed using a 1-L slurry phase Reactor for 141–212 h under constant reaction conditions: 220 °C, 2.0 MPa, H_2/CO = 2.0 and 6.0 Nl/g-cat/h. In the H_2S poisoning test, an H_2S in N_2 gas mixture was added to the syngas feed (1.0 ppm) after running the Fischer–Tropsch synthesis (FTS) reaction for ca. 6.0 h; as such, the impact of H_2S on the initial deactivation of the cobalt catalyst (unsteady state) was successfully assessed. The used catalysts were characterized by XANES to investigate if Co–S surface species were formed during the deactivation. The initial deactivation under 1.0 ppm H_2S condition was significantly higher (by 2.0–2.4 times) than that under clean conditions. CH_4 selectivity increased substantially and C_5+ selectivity decreased greatly with time regardless of whether H_2S was added or not; however, the addition of H_2S accelerated the changes in the hydrocarbon selectivities, which were likely caused by the sharp deactivation of the catalyst in the presence of H_2S. After co-feeding the sulfur for 141 h, a comparison was made at similar conversions by adjusting space velocity; the sulfur pretreated cobalt catalysts favored heavier hydrocarbons (C_5+) formation and suppressed lower hydrocarbon formation. The addition of H_2S to the feed increased CO_2 selectivity and the secondary reaction of 1-olefins. The XANES results revealed that surface species involving Co–S bonding formed on the cobalt catalyst after exposure to H_2S during FTS. This was likely the primary reason for the abnormal selectivity trends observed during and after the deactivation of the catalyst by sulfur. This study points out a possible approach to increase the selectivity to heavy hydrocarbons by properly sulfiding the cobalt catalyst prior to the FTS reaction. Graphical Abstract
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Effect of H 2 S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst
Applied Catalysis A-general, 2016Co-Authors: Wenping Ma, Gary Jacobs, Wilson D. Shafer, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Qunfeng Xiao, Yongfeng Hu, Shelley D. Hopps, Burtron H. DavisAbstract:Abstract The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270 °C, 1.3 MPa, H2/CO = 0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase Reactor. The used Fe catalysts were characterized by XRD, Mossbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1 ppm H2S in the feed. Co-feeding of 0.1 ppm H2S in syngas for 70 h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2 ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50 ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270 °C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260 °C and increased further to 13.5 at 230 °C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mossbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230 °C), and similar M/S ratios (13.5–15.0) were obtained.
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Fischer-Tropsch synthesis: Effect of ammonia in syngas on the Fischer-Tropsch synthesis performance of a precipitated iron catalyst
Journal of Catalysis, 2015Co-Authors: Wenping Ma, Gary Jacobs, Gerald A. Thomas, Dennis E. Sparks, Hussein H. Hamdeh, Venkat Ramana Rao Pendyala, Yongfeng Hu, Shelley D. Hopps, Aimee Maclennan, Burtron H. DavisAbstract:Abstract The 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 °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. NH 3 /av. Wt. feed) ammonia in syngas did not significantly deactivate the Fe catalyst or alter selectivities toward CH 4 , C 5+ , CO 2 , 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 χ-Fe 5 C 2 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 χ-Fe 5 C 2 during FTS via its thermal dissociation product, HNO 3 . This conclusion is further supported by reaction tests with co-feeding of similar concentrations of HNO 3 . Additional oxidation routes of iron carbide to magnetite by HNO 3 and/or by its thermal decomposition products are also considered: Fe 5 C 2 + NO x (and/or HNO 3 ) → Fe 3 O 4 . In this study, ion chromatography detected that 50–80% HNO 3 directly added or dissociated from AN eventually converted to ammonia during or after its oxidation of iron carbide, resulting from the reduction of NO x (NO x + H 2 + CO → NH 3 + CO 2 + N 2 + H 2 O) by H 2 and/or CO.
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Fischer-Tropsch synthesis: Effects of hydrohalic acids in syngas on a precipitated iron catalyst
ACS Catalysis, 2015Co-Authors: Wenping Ma, Gary Jacobs, Gerald A. Thomas, Wilson D. Shafer, Dennis E. Sparks, Hussein H. Hamdeh, Burtron H. DavisAbstract:The current investigation was undertaken to identify limits of hydrohalic acid (HX, X = F, Cl, Br) impurities in syngas and shed light on the mechanism of HX poisoning of a 100 Fe/5.1 Si/2 Cu/3 K FTS catalyst under industrially relevant conditions using a 1-L Slurry-Phase Reactor. Co-feeding