Multiwall carbon nanotubes (MWNTs) and alumina are combined to give a new type of nanohybrid for Fisher-Tropsch synthesis (FTS) catalyst support. Alumina nano-particles (10 wt%) were introduced directly on funct...Multiwall carbon nanotubes (MWNTs) and alumina are combined to give a new type of nanohybrid for Fisher-Tropsch synthesis (FTS) catalyst support. Alumina nano-particles (10 wt%) were introduced directly on functionalized MWNTs by a modified sol-gel method. Microstructure observations show that alumina particles were homogeneously dispersed on the inside and outside of modified MWNTs surfaces. 15 wt% cobalt loading catalysts were prepared with this nanohybrid and γ-alumina as a reference, using a sol-gel technique and wet impregnation method respectively. These catalysts were characterized by TEM, XRD, N2-adsorption, H2 chemisorption and TPR. The deposition of cobalt nanoparticles synthesized by sol-gel technique on the MWNTs nanohybrid shift the reduction peaks to a low temperature, indicating higher reducibility for uniform cobalt particles. Nanohybrid also aided in high dispersion of metal clusters and high stability and performance of catalyst. The proposed MWNTs nanohybrid-supported cobalt catalysts showed the improved FTS rate (gHc/(gcat.min)), CO conversion (%), and water gas shift rate (WGS)(gcoz/(gcat.h)) of 0.012, 52, and 30E-3, respectively, as compared to those of 0.007, 25, and 18E-3, respectively, on the γ-alumina-supported cobalt catalysts with the same Co loading.展开更多
Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AAC...Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AACH) and their mixture were obtained, and then, different kinds of alumina were obtained after calcination. Three catalysts supported on the different alumina were obtained via impregnating cobalt and ruthenium by incipient wetness. The effects of different precipitants on composition of precursors were?studied by XRD, FTIR, and TGA. The property and structure of alumina were studied by XRD and BET. The supported catalysts were studied by characterizations of XRD and H2-TPR, and the catalytic performance for Fischer-Tropsch synthesis (FTS) were evaluated at a fix-bed reactor. The relations among the composition of precursors, the property of alumina and the catalytic performance of supported catalysts were researched thoroughly.展开更多
A series of mesoporous alumina (MA) supported cobalt (Co/MA) catalysts with MA isomorphically substituted by zirconium (Zr) were synthesised and evaluated for their performance in the Fischer</span><span styl...A series of mesoporous alumina (MA) supported cobalt (Co/MA) catalysts with MA isomorphically substituted by zirconium (Zr) were synthesised and evaluated for their performance in the Fischer</span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;">Tropsch synthesis. The Zr/(Zr + Al) atomic ratios varied from 1% - 15%. A zirconium-impregnated Co/MA catalyst prepared by wet impregnation with a Zr/(Zr + Al) atomic ratio of 5% was also evaluated to examine Zr incorporation’s effect method. The catalysts synthesised were characterised using N</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> adsorption-desorption, X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). It was found that Zr</span><sup><span style="font-family:Verdana;">4+</span></sup><span style="font-family:Verdana;"> ions were incorporated into the framework of MA and kept intact up to a Zr/(Zr + Al) atomic ratio of 5%. The cobalt dispersion and reducibility were improved as the Zr/(Zr + Al) atomic ratio increased to 50%. The performance of these catalysts for Fischer</span></span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;">Tropsch synthesis was evaluated using a fixed bed reactor at temperature and pressure of 493 K and 20 bar, respectively. The feed syngas </span><span><span style="font-family:Verdana;">had an H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/CO ratio of 2, diluted with 10% Ar. For isomorphically</span></span><span style="font-family:Verdana;"> Zr-substituted Co/MA, the CO conversion and selectivity of diesel (C</span><sub><span style="font-family:Verdana;">10</span></sub><span style="font-family:Verdana;"> - C</span><sub><span style="font-family:Verdana;">20</span></sub><span style="font-family:Verdana;">) increased first and then decreased with increasing the Zr/(Zr + Al) atomic ratio. The maximum 38.9% CO conversion and 34.6% diesel (C</span><sub><span style="font-family:Verdana;">10</span></sub><span style="font-family:Verdana;"> - C</span><sub><span style="font-family:Verdana;">20</span></sub><span style="font-family:Verdana;">) selectivity were obtained at Zr/(Zr + Al) atomic ratio of 5%. The isomorphic substitution method was better than the wet impregnation method in CO conversion and diesel selectivity.展开更多
Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means...Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means of X-ray diffraction (XRD), temperature programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD) and O2 titration. Co-support compound formation can be detected in catalyst system by XRD. For the Co/Al2O3 catalysts with low cobalt loading, CoAl2O4 phase appears visibly. Two different reduction regions can be presented for Co/Al2O3 catalysts, which belong to Co3O4 crystallites (reduction at 320 ℃) and cobalt oxide-alumina interaction species (reduction at above 400 ℃). Increasing Co loading results in the increase of Co3O4 crystallite size. The reduced Co/Al2O3 catalysts have two adsorption sites, and cobalt loading greatly influences the adsorption behavior. With the increase of cobalt loading, the amount of low temperature adsorption is increased, the amount of high temperature adsorption is decreased, and the percentage reduction and cobalt crystallite size are increased.展开更多
Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-program...Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR). Activity and selectivity of iron-cobalt supported on different carriers for CO hydrogenation were studied under the conditions of 1.5 MPa, 493 K, 630 h^-1, and H2/CO ratio of 1.6. The results indicate that the activity, C4 olefin/(C4 olefin+C4 paraffin) ratio, and C5 olefin/(C5 olefin+C5 paraffin) decrease in the order of Fe-Co/SiO2, Fe-Co/AC1, Fe-Co/Al2O3 and Fe- Co/AC2. The activity of Fe-Co/SiO2 reached a maximum. The results of TPR show that the Fe-Co/SiO2 catalyst is to some extent different. XRD patterns show that the Fe-Co/SiO2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.展开更多
A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spect...A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spectroscopy. The Co/γ-Al_2O_3 catalysts were activated by using H_2, 20%CH_4/H_2 or CH_4, respectively. There was no obvious difference between the activities of the Co/γ-Al_2O_3 catalyst activated by using the different activation methods for methane dry reforming. The catalytic properties of the Co/γ-Al_2O_3 catalysts with different Co loadings were also investigated. The optimized Co loading for the Co/γ-Al_2O_3 catalyst pretreated with 20% CH_4/H_2 is around 12%(mass fraction).展开更多
The addition of small amounts of ceria to Co/Al2O3 catalysts increases the turnover rate of the catalyst and C5+ selectivity in the Fischer-Tropsch synthesis. In this work, the amounts of ceria, the calcination tempe...The addition of small amounts of ceria to Co/Al2O3 catalysts increases the turnover rate of the catalyst and C5+ selectivity in the Fischer-Tropsch synthesis. In this work, the amounts of ceria, the calcination temperature, the temperature-programmed reduction (TPR), the temperature-programmed oxidation (TPO), and XRD are investigated. The results show that the addition of small amounts of ceria to Co/Al2O3 catalyst (Ce/Co≈1∶ 10 ~1∶ 7, atom) can increase the CO conversion and liquid yield, while the calcination temperature can control both the chain growth probability and CO conversion in a reverse trend. The TPR and TPO experiments show that small amounts of Ceria can improve the reducibility, but the amounts of carbon deposit increase, and two-type carbon deposition is found in the short-term reaction catalyst.展开更多
Water-gas shift reaction catalyst at lower temperature (200-400 ℃) may improve the conversion of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobaltmolybdenum/alumina catalyst for...Water-gas shift reaction catalyst at lower temperature (200-400 ℃) may improve the conversion of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobaltmolybdenum/alumina catalyst for water-gas shift reaction. The influences of temperature, space velocity, and gas components on the formation of carbonyl sulfide over sulfided cobalt-molybdenum/alumina catalyst B303Q at 200-400 ℃ were studied in a tubular fixed-bed quartz-glass reactor under simulated water-gas shift conditions. The experimental results showed that the yield of carbonyl sulfide over B303Q catalyst reached a maximum at 220 ℃ with the increase in temperature, sharply decreased with the increase in space velocity and the content of water vapor, increased with the increase in the content of carbon monoxide and carbon dioxide, and its yield increased and then reached a stable value with the increase in the content of hydrogen and hydrogen sulfide. The formation mechanism of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was discussed on the basis of how these factors influence the formation of COS. The yield of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was the combined result of two reactions, that is, COS was first produced by the reaction of carbon monoxide with hydrogen sulfide, and then the as-produced COS was converted to hydrogen sulfide and carbon dioxide by hydrolysis. The mechanism of COS formation is assumed as follows: sulfur atoms in the Co9Ss-MoS2/Al2O3 crystal lattice were easily removed and formed carbonyl sulfide with CO, and then hydrogen sulfide in the water-gas shift gas reacted with the crystal lattice oxygen atoms in CoO-MoOa/Al2O3 to form Co9S8-MoS2/Al2O3. This mechanism for the formation of COS over water-gas shift catalyst B303Q is in accordance with the Mars-Van Krevelen's redox mechanism over metal sulfide.展开更多
基金supported by the Research Council of the Research Institute of Petroleum Industrythe Research and Development of the National Iranian Oil Company
文摘Multiwall carbon nanotubes (MWNTs) and alumina are combined to give a new type of nanohybrid for Fisher-Tropsch synthesis (FTS) catalyst support. Alumina nano-particles (10 wt%) were introduced directly on functionalized MWNTs by a modified sol-gel method. Microstructure observations show that alumina particles were homogeneously dispersed on the inside and outside of modified MWNTs surfaces. 15 wt% cobalt loading catalysts were prepared with this nanohybrid and γ-alumina as a reference, using a sol-gel technique and wet impregnation method respectively. These catalysts were characterized by TEM, XRD, N2-adsorption, H2 chemisorption and TPR. The deposition of cobalt nanoparticles synthesized by sol-gel technique on the MWNTs nanohybrid shift the reduction peaks to a low temperature, indicating higher reducibility for uniform cobalt particles. Nanohybrid also aided in high dispersion of metal clusters and high stability and performance of catalyst. The proposed MWNTs nanohybrid-supported cobalt catalysts showed the improved FTS rate (gHc/(gcat.min)), CO conversion (%), and water gas shift rate (WGS)(gcoz/(gcat.h)) of 0.012, 52, and 30E-3, respectively, as compared to those of 0.007, 25, and 18E-3, respectively, on the γ-alumina-supported cobalt catalysts with the same Co loading.
文摘Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AACH) and their mixture were obtained, and then, different kinds of alumina were obtained after calcination. Three catalysts supported on the different alumina were obtained via impregnating cobalt and ruthenium by incipient wetness. The effects of different precipitants on composition of precursors were?studied by XRD, FTIR, and TGA. The property and structure of alumina were studied by XRD and BET. The supported catalysts were studied by characterizations of XRD and H2-TPR, and the catalytic performance for Fischer-Tropsch synthesis (FTS) were evaluated at a fix-bed reactor. The relations among the composition of precursors, the property of alumina and the catalytic performance of supported catalysts were researched thoroughly.
基金supported by Unité de Catalyse et Chimie du Solide (UCCS)sponsor of scholarship: China scholarship council and School of Environment, Tsinghua University
文摘A series of mesoporous alumina (MA) supported cobalt (Co/MA) catalysts with MA isomorphically substituted by zirconium (Zr) were synthesised and evaluated for their performance in the Fischer</span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;">Tropsch synthesis. The Zr/(Zr + Al) atomic ratios varied from 1% - 15%. A zirconium-impregnated Co/MA catalyst prepared by wet impregnation with a Zr/(Zr + Al) atomic ratio of 5% was also evaluated to examine Zr incorporation’s effect method. The catalysts synthesised were characterised using N</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> adsorption-desorption, X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). It was found that Zr</span><sup><span style="font-family:Verdana;">4+</span></sup><span style="font-family:Verdana;"> ions were incorporated into the framework of MA and kept intact up to a Zr/(Zr + Al) atomic ratio of 5%. The cobalt dispersion and reducibility were improved as the Zr/(Zr + Al) atomic ratio increased to 50%. The performance of these catalysts for Fischer</span></span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;">Tropsch synthesis was evaluated using a fixed bed reactor at temperature and pressure of 493 K and 20 bar, respectively. The feed syngas </span><span><span style="font-family:Verdana;">had an H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/CO ratio of 2, diluted with 10% Ar. For isomorphically</span></span><span style="font-family:Verdana;"> Zr-substituted Co/MA, the CO conversion and selectivity of diesel (C</span><sub><span style="font-family:Verdana;">10</span></sub><span style="font-family:Verdana;"> - C</span><sub><span style="font-family:Verdana;">20</span></sub><span style="font-family:Verdana;">) increased first and then decreased with increasing the Zr/(Zr + Al) atomic ratio. The maximum 38.9% CO conversion and 34.6% diesel (C</span><sub><span style="font-family:Verdana;">10</span></sub><span style="font-family:Verdana;"> - C</span><sub><span style="font-family:Verdana;">20</span></sub><span style="font-family:Verdana;">) selectivity were obtained at Zr/(Zr + Al) atomic ratio of 5%. The isomorphic substitution method was better than the wet impregnation method in CO conversion and diesel selectivity.
文摘Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means of X-ray diffraction (XRD), temperature programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD) and O2 titration. Co-support compound formation can be detected in catalyst system by XRD. For the Co/Al2O3 catalysts with low cobalt loading, CoAl2O4 phase appears visibly. Two different reduction regions can be presented for Co/Al2O3 catalysts, which belong to Co3O4 crystallites (reduction at 320 ℃) and cobalt oxide-alumina interaction species (reduction at above 400 ℃). Increasing Co loading results in the increase of Co3O4 crystallite size. The reduced Co/Al2O3 catalysts have two adsorption sites, and cobalt loading greatly influences the adsorption behavior. With the increase of cobalt loading, the amount of low temperature adsorption is increased, the amount of high temperature adsorption is decreased, and the percentage reduction and cobalt crystallite size are increased.
文摘Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR). Activity and selectivity of iron-cobalt supported on different carriers for CO hydrogenation were studied under the conditions of 1.5 MPa, 493 K, 630 h^-1, and H2/CO ratio of 1.6. The results indicate that the activity, C4 olefin/(C4 olefin+C4 paraffin) ratio, and C5 olefin/(C5 olefin+C5 paraffin) decrease in the order of Fe-Co/SiO2, Fe-Co/AC1, Fe-Co/Al2O3 and Fe- Co/AC2. The activity of Fe-Co/SiO2 reached a maximum. The results of TPR show that the Fe-Co/SiO2 catalyst is to some extent different. XRD patterns show that the Fe-Co/SiO2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.
文摘A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spectroscopy. The Co/γ-Al_2O_3 catalysts were activated by using H_2, 20%CH_4/H_2 or CH_4, respectively. There was no obvious difference between the activities of the Co/γ-Al_2O_3 catalyst activated by using the different activation methods for methane dry reforming. The catalytic properties of the Co/γ-Al_2O_3 catalysts with different Co loadings were also investigated. The optimized Co loading for the Co/γ-Al_2O_3 catalyst pretreated with 20% CH_4/H_2 is around 12%(mass fraction).
文摘The addition of small amounts of ceria to Co/Al2O3 catalysts increases the turnover rate of the catalyst and C5+ selectivity in the Fischer-Tropsch synthesis. In this work, the amounts of ceria, the calcination temperature, the temperature-programmed reduction (TPR), the temperature-programmed oxidation (TPO), and XRD are investigated. The results show that the addition of small amounts of ceria to Co/Al2O3 catalyst (Ce/Co≈1∶ 10 ~1∶ 7, atom) can increase the CO conversion and liquid yield, while the calcination temperature can control both the chain growth probability and CO conversion in a reverse trend. The TPR and TPO experiments show that small amounts of Ceria can improve the reducibility, but the amounts of carbon deposit increase, and two-type carbon deposition is found in the short-term reaction catalyst.
基金the National Basic Research Program of China (No.2005CB221203)
文摘Water-gas shift reaction catalyst at lower temperature (200-400 ℃) may improve the conversion of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobaltmolybdenum/alumina catalyst for water-gas shift reaction. The influences of temperature, space velocity, and gas components on the formation of carbonyl sulfide over sulfided cobalt-molybdenum/alumina catalyst B303Q at 200-400 ℃ were studied in a tubular fixed-bed quartz-glass reactor under simulated water-gas shift conditions. The experimental results showed that the yield of carbonyl sulfide over B303Q catalyst reached a maximum at 220 ℃ with the increase in temperature, sharply decreased with the increase in space velocity and the content of water vapor, increased with the increase in the content of carbon monoxide and carbon dioxide, and its yield increased and then reached a stable value with the increase in the content of hydrogen and hydrogen sulfide. The formation mechanism of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was discussed on the basis of how these factors influence the formation of COS. The yield of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was the combined result of two reactions, that is, COS was first produced by the reaction of carbon monoxide with hydrogen sulfide, and then the as-produced COS was converted to hydrogen sulfide and carbon dioxide by hydrolysis. The mechanism of COS formation is assumed as follows: sulfur atoms in the Co9Ss-MoS2/Al2O3 crystal lattice were easily removed and formed carbonyl sulfide with CO, and then hydrogen sulfide in the water-gas shift gas reacted with the crystal lattice oxygen atoms in CoO-MoOa/Al2O3 to form Co9S8-MoS2/Al2O3. This mechanism for the formation of COS over water-gas shift catalyst B303Q is in accordance with the Mars-Van Krevelen's redox mechanism over metal sulfide.