The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A se...The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A self-consistent kinetic model for Fischer-Tropsch reaction proposed here was found to correlate experimental data well and hence was used to describe the consumption rates of reactants and formation rates of hydrocarbon products.The perturbed-chain statistical associating fluid theory equation of state was used to describe vapor-liquid equilibrium behavior associated with Fischer-Tropsch reaction.Local interaction between intraparticle diffusion and Fischer-Tropsch reaction was investigated in detail.Results showed that in order to avoid the adverse influence of intraparticle diffusional limitations on catalyst reactivity and product selectivity,the use of small particles is necessary.Large eggshell spherical particles are shown to keep the original catalyst reactivity and enhance the selectivity of heavy hydrocarbon products.The suitable layer thickness for a spherical particle with a diameter of 2 mm is nearly 0.15 mm.With the same outer diameter of 2 mm,the catalyst reactivity and heavy product selectivity of hollow cylindrical particles with a layer thickness of 0.25 mm are found to be larger than eggshell spherical particles.From the viewpoint of catalytic performance,hollow cylindrical particles are a better choice for industrial applications.展开更多
A systematic study was carried out to investigate the promotion effect of manganese on the performance of a coprecipitated iron-manganese bimetallic catalyst for the light olefins synthesis from syngas. The catalyst s...A systematic study was carried out to investigate the promotion effect of manganese on the performance of a coprecipitated iron-manganese bimetallic catalyst for the light olefins synthesis from syngas. The catalyst samples were characterized by N2 physisorption, transmis- sion electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, powder X-ray diffraction （XRD）, Mossbauer spectroscopy, H2- differential thermogravimetric analysis （H2-DTG）, CO temperature-programmed reduction （CO-TPR） and CO2 temperature-programmed des- orption （CO2-TPD）. The Fischer-Tropsch synthesis （FTS） performance of the catalyst was measured at 1.5 MPa, 250 ℃ and syngas with H2/CO ratio of 2.0. The characterization results indicated that the addition of manganese decreases the catalyst crystallite size, and improves the catalyst BET surface area and pore volume. The presence of manganese suppresses the catalyst reduction and carburization in H2, CO and syngas, respectively. The addition of manganese improves the catalytic activity of water-gas shift reaction and suppresses the oxidation of iron carbides in the FTS reaction. The incorporation of manganese improves the catalyst surface basicity and results in a significant improvement in the selectivities to light olefins and heavy hydrocarbons （C5＋）, and furthermore an inhibition of methane formation in FTS. The pure iron catalyst （Mn-00） has the highest initial FTS catalytic activity （65%） and the lowest selectivity （17.35 wt%） to light olefins （C2=-C4=）. The addition of an appropriate amount of manganese can improve the catalyst FTS activity.展开更多
The isothermal kinetics of the Fischer-Tropsch synthesis （FTS） over Fe-Cu-K spray-dried catalyst was studied in a spinning basket reactor. The experiments were carried out at a constant temperature of 523 K, n（H2...The isothermal kinetics of the Fischer-Tropsch synthesis （FTS） over Fe-Cu-K spray-dried catalyst was studied in a spinning basket reactor. The experiments were carried out at a constant temperature of 523 K, n（H2）/n（CO） feed ratios of 0.8 2.0, reactor pressures of 1.1 2.5 MPa, and space velocity of 0.556× 10^-3 Nm^3/kgcat·s. Kinetic model for hydrocarbon formation was derived on the basis of simplified carbide mechanism to reduce the number of parameters. Two individual rate constants for methane and ethene were considered. Furthermore, the model was modified empirically by non-intrinsic effect, such as physisorption and fictitious olefin pressures that were taken into account, and the influences of secondary reaction of α-olefins on product distribution. The simulation results showed that the experimental phenomena of FTS and the deviations from ASF distribution, such as the relatively high yield of methane and low yield of ethene observed experimentally could be depicted basically.展开更多
The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through d...The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through density functional theory calculations.We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites.The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst.The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C-O bond.We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models.We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations.Among them,a ridge linear regression model with2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.展开更多
Solid surfaces usually reach thermodynamic equilibrium through particle exchange with their environment under reactive conditions.A prerequisite for understanding their functionalities is detailed knowledge of the sur...Solid surfaces usually reach thermodynamic equilibrium through particle exchange with their environment under reactive conditions.A prerequisite for understanding their functionalities is detailed knowledge of the surface composition and atomistic geometry under working conditions.Owing to the large number of possible Miller indices and terminations involved in multielement solids,extensive sampling of the compositional and conformational space needed for reliable surface energy estimation is beyond the scope of ab initio calculations.Here,we demonstrate,using the case of iron carbides in environments with varied carbon chemical potentials,that the stable surface composition and geometry of multielement solids under reactive conditions,which involve large compositional and conformational spaces,can be predicted at ab initio accuracy using an approach that combines the bond valence model,Gaussian process regression,and ab initio thermodynamics.Determining the atomistic structure of surfaces under working conditions paves the way toward identifying the true active sites of multielement catalysts in heterogeneous catalysis.展开更多
The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 tempe...The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 temperature-programmed reduction （TPR）, and Mǒssbauer spectroscopy. The FTS performances of the catalysts were tested in a slurry phase reactor. The characterization results indicated that Mn increased the surface area of the catalyst, and improved the dispersion of （α-Fe2O3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction. The Fe-Mn interaction also suppressed the reduction of （α-Fe2O3 to Fe3O4, stabilized the FeO phase, and （or） decreased the carburization degree of the catalysts in the H2 and syngas reduction processes. In addition, incorporated Mn decreased the initial catalyst activity, but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe3O4, and improved further carburization of the catalysts. Manganese suppressed the formation of CH4 and increased the selectivity to light olefins （C2-4^=）, but it had little effect on the selectivities to heavy （C5＋） hydrocarbons. All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter, to some extent, in the precipitated iron-manganese catalyst system.展开更多
A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basici...A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basicity of an iron-based Fischer-Tropsch synthesis （FTS） catalyst. The catalyst samples were characterized by N2 physisorption, X-ray photoelectron spectroscopy （XPS）, H2 （or CO） temperature-programmed reduction （TPR）, CO2 temperature-programmed desorption （TPD）, and M5ssbauer spectroscopy. The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor （CSTR）. The characterization results indicated that the manganese promoter incorporated by using the coprecipitation method could improve the dispersion of iron oxide, and decrease the size of the iron oxide crystallite. The manganese incorporated with the impregnation method is enriched on the catalyst＇s surface. The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H2, CO, and syngas because of the excessive enrichment of manganese on the catalyst surface. The catalyst added manganese using the coprecipitation method has the highest CO conversion （51.9%） and the lowest selectivity for heavy hydrocarbons （C12＋）.展开更多
Fischer-Tropsch synthesis （FTS） was carried out with an industrial iron-based catalyst （100Fe/5Cu/6K/16SiO2, by weight） under the baseline conditions in a stirred tank slurry reactor （STSR）. The effects of activ...Fischer-Tropsch synthesis （FTS） was carried out with an industrial iron-based catalyst （100Fe/5Cu/6K/16SiO2, by weight） under the baseline conditions in a stirred tank slurry reactor （STSR）. The effects of activation pressure on the catalyst activity and selectivity were investigated. It was found that iron phase compositions, textural properties, and FTS performances of the catalysts were strongly dependent on activation pressure. The high activation pressure retards the carburization. MФssbauer effect spectroscopy （MES） results indicated that the contents of the iron carbides clearly decrease with the increase of activation pressure, especially for the activation pressure increasing from 1.0 MPa to 1.5 MPa, and the reverse trend is observed for superparamagnetic Fe^3＋ （spm）. The higher content of Fe^3＋ （spm） results in the higher amount of CO2 in tail gas when the catalyst is reduced at higher pressure. The catalyst activity decreases with the increase of activation pressure. The high quantity of iron carbides is necessary to obtain high FTS activity. However, the activity of the catalyst activated in syngas can not be predicted solely from the fraction of the carbides. It is concluded that activation with syngas at the lower pressure would be the most desirable for the better activity and stability on the iron-based catalyst.展开更多
The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurryphase continuously stirred tank reactor （CSTR） over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregna...The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurryphase continuously stirred tank reactor （CSTR） over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N2 physisorption, X-ray photoelectron spectroscopy （XPS）, H2 （or CO） temperature-programmed reduction （TPR）, Mossbauer spectroscopy, and CO2 temperature-programmed desorption （TPD）. The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas, and decreased the catalyst surface basicity. At the same time, the addition of small amounts of sulfate improved the activities of FischerTropsch synthesis （FTS） and water gas shift （WGS）, shifted the product to light hydrocarbons （C1-C11） and suppressed the formation of heavy products （C12＋）. Addition of SO4^2- to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe, and S-05 catalyst gave the highest CO conversion （62.3%）, and beyond this sulfur level the activity of the catalyst decreased.展开更多
Fischer-Tropsch synthesis(FTS)wax is a mixture of linear hydrocarbons with carbon number from C7 to C70+.Converting FTS wax into high-quality diesel(no sulfur and nitrogen contents)by hydrocracking technology is attra...Fischer-Tropsch synthesis(FTS)wax is a mixture of linear hydrocarbons with carbon number from C7 to C70+.Converting FTS wax into high-quality diesel(no sulfur and nitrogen contents)by hydrocracking technology is attractive in economy and practicability.Kinetic study of the hydrocracking of FTS wax in elementary step level is very challenging because of the huge amounts of reactions and species involved.Generation of reaction networks for hydrocracking of FTS wax in which the chain length goes up to C70 is described on the basis of Boolean adjacency matrixes.Each of the species(including paraffins,olefins and carbenium ions)involved in the elementary steps is represented digitally by using a(N+3)N matrix,in which a group of standardized numbering rules are designed to guarantee the unique identity of the species.Subsequently,the elementary steps are expressed by computer-aided matrix transformations in terms of proposed reaction rules.Dynamic memory allocation is used in species storage and a characteristic vector with nine elements is designed to store the key information of a(N+3)N matrix,which obviously reduces computer memory consumption and improves computing efficiency.The detailed reaction networks of FTS wax hydrocracking can be generated smoothly and accurately by the current method.The work is the basis of advanced elementary-step-level kinetic modeling.展开更多
Chemical-disordered materials have a wide range of applications whereas the determination of their structures or configurations isone of the most important and challenging problems. Traditional methods are extremely i...Chemical-disordered materials have a wide range of applications whereas the determination of their structures or configurations isone of the most important and challenging problems. Traditional methods are extremely inefficient or intractable for large systemsdue to the notorious exponential-wall issue that the number of possible structures increase exponentially for N-body systems.Herein, we introduce an efficient approach to predict the thermodynamically stable structures of chemical-disordered materials viaactive-learning accompanied by first-principles calculations. Our method, named LAsou, can efficiently compress the samplingspace and dramatically reduce the computational cost. Three distinct and typical finite-size systems are investigated, including theanion-disordered BaSc(O_(x)F_(1−x))3 (x = 0.667), the cation-disordered Ca_(1−x)Mn_(x)CO_(3) (x = 0.25) with larger size and the defect-disordered ε-FeC_(x) (x = 0.5) with larger space. The commonly used enumeration method requires to explicitly calculate 2664, 1033,and 10496 configurations, respectively, while the LAsou method just needs to explicitly calculate about 15, 20, and 10configurations, respectively. Besides the finite-size system, our LAsou method is ready for quasi-infinite size systems empoweringmaterials design.展开更多
基金supported by the National Natural Science Foundation of China(21908234)the National Key Research&Development Program of China(2020YFB0606404)+1 种基金the Inner Mongolia Science and Technology Agency Program(2019CG058)Shanxi Province Natural Science Foundation(202103021223063).
文摘The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A self-consistent kinetic model for Fischer-Tropsch reaction proposed here was found to correlate experimental data well and hence was used to describe the consumption rates of reactants and formation rates of hydrocarbon products.The perturbed-chain statistical associating fluid theory equation of state was used to describe vapor-liquid equilibrium behavior associated with Fischer-Tropsch reaction.Local interaction between intraparticle diffusion and Fischer-Tropsch reaction was investigated in detail.Results showed that in order to avoid the adverse influence of intraparticle diffusional limitations on catalyst reactivity and product selectivity,the use of small particles is necessary.Large eggshell spherical particles are shown to keep the original catalyst reactivity and enhance the selectivity of heavy hydrocarbon products.The suitable layer thickness for a spherical particle with a diameter of 2 mm is nearly 0.15 mm.With the same outer diameter of 2 mm,the catalyst reactivity and heavy product selectivity of hollow cylindrical particles with a layer thickness of 0.25 mm are found to be larger than eggshell spherical particles.From the viewpoint of catalytic performance,hollow cylindrical particles are a better choice for industrial applications.
基金supported by Natural Science Foundation of Chongqing Three Gorges University (12ZD14)Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University
文摘A systematic study was carried out to investigate the promotion effect of manganese on the performance of a coprecipitated iron-manganese bimetallic catalyst for the light olefins synthesis from syngas. The catalyst samples were characterized by N2 physisorption, transmis- sion electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, powder X-ray diffraction （XRD）, Mossbauer spectroscopy, H2- differential thermogravimetric analysis （H2-DTG）, CO temperature-programmed reduction （CO-TPR） and CO2 temperature-programmed des- orption （CO2-TPD）. The Fischer-Tropsch synthesis （FTS） performance of the catalyst was measured at 1.5 MPa, 250 ℃ and syngas with H2/CO ratio of 2.0. The characterization results indicated that the addition of manganese decreases the catalyst crystallite size, and improves the catalyst BET surface area and pore volume. The presence of manganese suppresses the catalyst reduction and carburization in H2, CO and syngas, respectively. The addition of manganese improves the catalytic activity of water-gas shift reaction and suppresses the oxidation of iron carbides in the FTS reaction. The incorporation of manganese improves the catalyst surface basicity and results in a significant improvement in the selectivities to light olefins and heavy hydrocarbons （C5＋）, and furthermore an inhibition of methane formation in FTS. The pure iron catalyst （Mn-00） has the highest initial FTS catalytic activity （65%） and the lowest selectivity （17.35 wt%） to light olefins （C2=-C4=）. The addition of an appropriate amount of manganese can improve the catalyst FTS activity.
基金This work was supported by Chinese Academy of Sciences (No. KGCX1-SW-02)National Ministry of Science and Technology of via 863 plan (No. 2001AA523010)Shanxi Natural Science Foundation (No. 20031032)National Natural Science Foundation of China (No. 20473111, 20590361).
文摘The isothermal kinetics of the Fischer-Tropsch synthesis （FTS） over Fe-Cu-K spray-dried catalyst was studied in a spinning basket reactor. The experiments were carried out at a constant temperature of 523 K, n（H2）/n（CO） feed ratios of 0.8 2.0, reactor pressures of 1.1 2.5 MPa, and space velocity of 0.556× 10^-3 Nm^3/kgcat·s. Kinetic model for hydrocarbon formation was derived on the basis of simplified carbide mechanism to reduce the number of parameters. Two individual rate constants for methane and ethene were considered. Furthermore, the model was modified empirically by non-intrinsic effect, such as physisorption and fictitious olefin pressures that were taken into account, and the influences of secondary reaction of α-olefins on product distribution. The simulation results showed that the experimental phenomena of FTS and the deviations from ASF distribution, such as the relatively high yield of methane and low yield of ethene observed experimentally could be depicted basically.
基金financially supported from the National Natural Science Foundation of China (No.22002008)Ningxia Key Research and Development Project,China (Nos.2022BEE03002 and 2022BSB03056)funding support from Synfuels China,Co.,Ltd.and Beijing Advanced Innovation Center for Materials Genome Engineering。
文摘The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through density functional theory calculations.We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites.The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst.The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C-O bond.We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models.We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations.Among them,a ridge linear regression model with2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.
基金This work was financially supported by the National Science Fund for Distinguished Young Scholars of China(grant no.22225206)the National Key R&D Program of China(no.2022YFA1604103)+6 种基金the National Natural Science Foundation of China(nos.21972157 and 21972160)the CAS Project for Young Scientists in Basic Research(YSBR-005)the Key Research Program of Frontier Sciences CAS(ZDBS-LY-7007)the Major Research Plan of the National Natural Science Foundation of China(92045303)the Informatization Plan of the Chinese Academy of Sciences(grant no.CAS-WX2021SF0110)the Youth Innovation Promotion Association CAS(2020179)Funding support was also received from the Beijing Advanced Innovation Center for Materials Genome Engineering,Synfuels China Co.,Ltd.,and the Institute of Coal Chemistry,Chinese Academy of Sciences.
文摘Solid surfaces usually reach thermodynamic equilibrium through particle exchange with their environment under reactive conditions.A prerequisite for understanding their functionalities is detailed knowledge of the surface composition and atomistic geometry under working conditions.Owing to the large number of possible Miller indices and terminations involved in multielement solids,extensive sampling of the compositional and conformational space needed for reliable surface energy estimation is beyond the scope of ab initio calculations.Here,we demonstrate,using the case of iron carbides in environments with varied carbon chemical potentials,that the stable surface composition and geometry of multielement solids under reactive conditions,which involve large compositional and conformational spaces,can be predicted at ab initio accuracy using an approach that combines the bond valence model,Gaussian process regression,and ab initio thermodynamics.Determining the atomistic structure of surfaces under working conditions paves the way toward identifying the true active sites of multielement catalysts in heterogeneous catalysis.
基金Foundation item:the National Outstanding Young Scientists Foundation of China(20625620)the National Key Basic Research Program of China(973 Program,2007CB216401)+1 种基金the National Natural Science Foundation of China(20590360)the Natural Science Foundation of Shanxi Province(2006021014).
文摘The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 temperature-programmed reduction （TPR）, and Mǒssbauer spectroscopy. The FTS performances of the catalysts were tested in a slurry phase reactor. The characterization results indicated that Mn increased the surface area of the catalyst, and improved the dispersion of （α-Fe2O3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction. The Fe-Mn interaction also suppressed the reduction of （α-Fe2O3 to Fe3O4, stabilized the FeO phase, and （or） decreased the carburization degree of the catalysts in the H2 and syngas reduction processes. In addition, incorporated Mn decreased the initial catalyst activity, but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe3O4, and improved further carburization of the catalysts. Manganese suppressed the formation of CH4 and increased the selectivity to light olefins （C2-4^=）, but it had little effect on the selectivities to heavy （C5＋） hydrocarbons. All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter, to some extent, in the precipitated iron-manganese catalyst system.
基金Foundation item:the National Natural Science Foundation of China(20590360)the Natural Science Foundation of Shanxi Province(2006021014)+1 种基金the National Outstanding Young Scientists Foundation of China(20625620)National Key Basic Research Program of China(973 Program)(2007CB216401).
文摘A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basicity of an iron-based Fischer-Tropsch synthesis （FTS） catalyst. The catalyst samples were characterized by N2 physisorption, X-ray photoelectron spectroscopy （XPS）, H2 （or CO） temperature-programmed reduction （TPR）, CO2 temperature-programmed desorption （TPD）, and M5ssbauer spectroscopy. The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor （CSTR）. The characterization results indicated that the manganese promoter incorporated by using the coprecipitation method could improve the dispersion of iron oxide, and decrease the size of the iron oxide crystallite. The manganese incorporated with the impregnation method is enriched on the catalyst＇s surface. The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H2, CO, and syngas because of the excessive enrichment of manganese on the catalyst surface. The catalyst added manganese using the coprecipitation method has the highest CO conversion （51.9%） and the lowest selectivity for heavy hydrocarbons （C12＋）.
基金supported by the Foundation of China Postdoctoral Science Foundation (20080430734)
文摘Fischer-Tropsch synthesis （FTS） was carried out with an industrial iron-based catalyst （100Fe/5Cu/6K/16SiO2, by weight） under the baseline conditions in a stirred tank slurry reactor （STSR）. The effects of activation pressure on the catalyst activity and selectivity were investigated. It was found that iron phase compositions, textural properties, and FTS performances of the catalysts were strongly dependent on activation pressure. The high activation pressure retards the carburization. MФssbauer effect spectroscopy （MES） results indicated that the contents of the iron carbides clearly decrease with the increase of activation pressure, especially for the activation pressure increasing from 1.0 MPa to 1.5 MPa, and the reverse trend is observed for superparamagnetic Fe^3＋ （spm）. The higher content of Fe^3＋ （spm） results in the higher amount of CO2 in tail gas when the catalyst is reduced at higher pressure. The catalyst activity decreases with the increase of activation pressure. The high quantity of iron carbides is necessary to obtain high FTS activity. However, the activity of the catalyst activated in syngas can not be predicted solely from the fraction of the carbides. It is concluded that activation with syngas at the lower pressure would be the most desirable for the better activity and stability on the iron-based catalyst.
基金the National Natural Science Foundation of China(20590360)and the Natural Science Foundation of Shanxi Province(2006021014).
文摘The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurryphase continuously stirred tank reactor （CSTR） over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N2 physisorption, X-ray photoelectron spectroscopy （XPS）, H2 （or CO） temperature-programmed reduction （TPR）, Mossbauer spectroscopy, and CO2 temperature-programmed desorption （TPD）. The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas, and decreased the catalyst surface basicity. At the same time, the addition of small amounts of sulfate improved the activities of FischerTropsch synthesis （FTS） and water gas shift （WGS）, shifted the product to light hydrocarbons （C1-C11） and suppressed the formation of heavy products （C12＋）. Addition of SO4^2- to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe, and S-05 catalyst gave the highest CO conversion （62.3%）, and beyond this sulfur level the activity of the catalyst decreased.
基金supported by the National Key Research&Development Program of China(2020YFB0606404)National Natural Science Foundation of China(21908234)。
文摘Fischer-Tropsch synthesis(FTS)wax is a mixture of linear hydrocarbons with carbon number from C7 to C70+.Converting FTS wax into high-quality diesel(no sulfur and nitrogen contents)by hydrocracking technology is attractive in economy and practicability.Kinetic study of the hydrocracking of FTS wax in elementary step level is very challenging because of the huge amounts of reactions and species involved.Generation of reaction networks for hydrocracking of FTS wax in which the chain length goes up to C70 is described on the basis of Boolean adjacency matrixes.Each of the species(including paraffins,olefins and carbenium ions)involved in the elementary steps is represented digitally by using a(N+3)N matrix,in which a group of standardized numbering rules are designed to guarantee the unique identity of the species.Subsequently,the elementary steps are expressed by computer-aided matrix transformations in terms of proposed reaction rules.Dynamic memory allocation is used in species storage and a characteristic vector with nine elements is designed to store the key information of a(N+3)N matrix,which obviously reduces computer memory consumption and improves computing efficiency.The detailed reaction networks of FTS wax hydrocracking can be generated smoothly and accurately by the current method.The work is the basis of advanced elementary-step-level kinetic modeling.
基金The authors are grateful for the financial support from the National Key R&D Program of China(No.2022YFA1604103)National Science Fund for Distinguished Young Scholars of China(Grant No.22225206)+5 种基金the National Natural Science Foundation of China(Nos.21972157,21972160 and 21703272)CAS Project for Young Scientists in Basic Research(YSBR-005),Key Research Program of Frontier Sciences CAS(ZDBS-LY-7007)Major Research plan of the National Natural Science Foundation of China(92045303)CAS Project for Internet Security and Information Technology(CAS-WX2021SF0110)Science and Technology Plan Project of Inner Mongolia Autono-mous Region of China(2021GG0309)funding support from Beijing Advanced Innovation Center for Materials Genome Engineering,Synfuels China,Co.Ltd,and Institute of Coal Chemistry(CAS).Q.P.would like to acknowledge the support provided by LiYing Program of the Institute of Mechanics,Chinese Academy of Sciences(Grant No.E1Z1011001).
文摘Chemical-disordered materials have a wide range of applications whereas the determination of their structures or configurations isone of the most important and challenging problems. Traditional methods are extremely inefficient or intractable for large systemsdue to the notorious exponential-wall issue that the number of possible structures increase exponentially for N-body systems.Herein, we introduce an efficient approach to predict the thermodynamically stable structures of chemical-disordered materials viaactive-learning accompanied by first-principles calculations. Our method, named LAsou, can efficiently compress the samplingspace and dramatically reduce the computational cost. Three distinct and typical finite-size systems are investigated, including theanion-disordered BaSc(O_(x)F_(1−x))3 (x = 0.667), the cation-disordered Ca_(1−x)Mn_(x)CO_(3) (x = 0.25) with larger size and the defect-disordered ε-FeC_(x) (x = 0.5) with larger space. The commonly used enumeration method requires to explicitly calculate 2664, 1033,and 10496 configurations, respectively, while the LAsou method just needs to explicitly calculate about 15, 20, and 10configurations, respectively. Besides the finite-size system, our LAsou method is ready for quasi-infinite size systems empoweringmaterials design.
