Fe/SiO_2纳米复合物上合成气制低碳烯烃催化性能研究

分别采用一步合成法和常规共沉淀法制备了Fe/SiO2催化剂,通过N2物理吸附、X射线衍射、透射电镜、傅里叶变换红外光谱和程序升温还原等方法对催化剂进行了表征,并在固定床反应器中对其费托合成制低碳烯烃的催化性能进行了评价。结果表明,与共沉淀铁基催化剂不同,采用一步合成法制备的纳米复合物主要由Fe3O4相构成,形貌呈规则球形,平均粒径为30 nm,尺寸分布窄,更容易还原。一步合成法制得的Fe/SiO2催化剂对费托合成反应具有较高的活性和低碳烯烃选择性、较低的甲烷选择性和良好的稳定性。     

Al2O3助剂对Co/SiC催化剂F-T反应性能的影响

分别采用沉淀法、尿素水解法制备Al₂O₃/SiC复合载体,采用等体积浸渍法制备Co/Al₂O₃-SiC催化剂。结合N₂吸附、XRD、H₂-TPR、XPS等表征手段,研究Al₂O₃助剂对钴基催化剂物相结构、还原行为以及F-T合成性能等的影响。结果表明,氧化铝加入后增强了载体与钴物种之间的相互作用,提高了钴物种的分散度,降低了钴物种的还原度。尿素水解法引入Al₂O₃后,载体与钴物种具有适中的相互作用,表现出较高的反应活性。沉淀法制备的载体负载钴物种后由于较强的金属-载体相互作用,表现出较优的稳定性。     

热分解法制备的Co/SiO2催化剂上费-托合成反应性能

以无定形二氧化硅为载体,分别采用浸渍法和热分解法制备了钴基催化剂Co/A200-I和Co/A200-D,采用TG、XRD、TEM和TPR等手段对其进行了表征,并考察了这些催化剂在费-托合成反应中的性能。结果表明,浸渍法制备的Co/A200-I催化剂中钴颗粒没有规则的形状,但却具有较高的费-托合成反应活性;热分解法制备的Co/A200-D催化剂中钴颗粒呈一种球形二次结构,直径比较均匀,对于费-托合成反应具有较高的轻质烃选择性。此外,载体比表面积对催化剂结构也有较大的影响;相对于Co/A200-D催化剂,Co/A380-D催化剂的载体比表面积较大,这使得金属-载体间的相互作用较强而较难还原,但还原后Co/A380-D催化剂拥有较高的钴分散度和较好的反应活性     

Fischer-Tropsch synthesis by nano-structured iron catalyst

Effects of nanoscale iron oxide particles on textural structure, reduction, carburization and catalytic behavior of precipitated iron catalyst in Fischer-Tropsch synthesis (FTS) are investigated. Nanostructured iron catalysts were prepared by microemulsion method in two series. Firstly, Fe2O3, CuO and La2O3 nanoparticles were prepared separately and were mixed to attain Fe/Cu/La nanostructured catalyst (sep-nano catalyst); Secondly nanostructured catalyst was prepared by co-precipitation in a water-in-oil microemulsion method (mix-nano catalyst). Also, conventional iron catalyst was prepared with common co-precipitation method. Structural characterizations of the catalysts were performed by TEM, XRD, H2 and CO-TPR tests. Particle size of iron oxides for sep-nano and mix-nano catalysts, which were determined by XRD pattern (Scherrer equation) and TEM images was about 20 and 21.6 nm, respectively. Catalyst evaluation was conducted in a fixed-bed stainless steel reactor and compared with conventional iron catalyst. The results revealed that FTS reaction increased while WGS reaction and olefin/paraffin ratio decreased in nanostructured iron catalysts.     

Kinetics studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis (FTS) were studied in a wide range of synthesis gas conversions and compared with conventional catalyst. The conventional Fe/Cu/La catalyst was prepared by co-precipitation of Fe and Cu nitrates in aqueous media and Fe/Cu/La nanostructure catalyst was prepared by co-precipitation in a water-in-oil micro-emulsion. Nano-structured iron catalyst shows higher FTS activity. Kinetic results indicated that in FTS rate expression, the rate constant (k) increased and adsorption parameter (b) decreased by decreasing the catalyst particle size from conventional to nano-structured. Since increasing in the rate constant and decreasing in the adsorption parameter affected the FTS rate in parallel direction, the particle size of catalyst showed complicated effects on kinetic parameters of FTS reaction.     

Cu/Mn/ZrO2 catalyst for alcohol synthesis by Fischer-Tropsch modified elements

A Cu/Mn/ZrO₂ methanol synthesis catalyst modified by Fischer-Tropsch (F-T) element (Ni,Co,Fe) was prepared by an coprecipatation method. The addition of F-T elements had a great effect on the catalyst performance. The higher alcohol selectivity increased greatly compared with that of the Cu/Mn/ZrO₂ catalyst when nickel and cobalt were added, while the addition of iron improved the selectivity tohydrocarbon due to the interaction of the F-T element and the Cu/Mn/ZrO₂ catalyst.     

Effect of nano-particle size on product distribution and kinetic parameters of Fe/Cu/La catalyst in Fischer-Tropsch synthesis

Effects of nano-particle size on hydrocarbon production rates and distributions for precipitated Fe/Cu/La catalysts in Fischer-Tropsch synthesis were investigated. Nano-structured iron catalyst was prepared by micro-emulsion method. The concept of two superimposed Anderson-Schulz-Flory (ASF) distributions has been applied for the representation of the effects of reaction conditions and nano-particles size on kinetics parameters and product distributions. These results reveal that by reducing the particle size of catalyst, the break in ASF distributions was decreased. Also useful different kinetics equations for synthesis of C_3 to C_9 and C_(10) to C_(22) were determined by using α_1 and α_2 chain growth probabilities.     

制备方法对双介孔钴基催化剂结构及其费-托反应性能的影响

以双介孔分布MCM-41分子筛为载体,采用等体积浸渍、氨水气相诱导水解和过量浸渍法制备了费-托合成钴摹催化剂,并考察了它们的孔结构、活性物种分布及费-托合成催化性能.结粜表明,采用等体积浸渍法和氨水气相诱导水解法制备的催化剂都保持了较好的双介孔特性,Co颗粒人部分位于分子筛的孔道内部.过量浸渍法和等体积浸渍法制备的催化...     

Study on iron-manganese catalysts for Fischer-Tropsch synthesis

Iron-manganese catalysts were prepared by co-precipitation method.Characterization of catalysts was carried out by using X-ray diffraction(XRD),scanning electron microscopy(SEM),temperature program reduction(TPR),N2 adsorption-desorption measurements.The results from catalytic performance tests in Fischer-Tropsch synthesis showed that the iron-manganese catalysts are supersensitive to catalyst composition and materials source.It was found that C2~4 light olefins increased while CH4 and CO2 decreased by using iron-manganese catalyst prepared from iron(II) sulfate(A catalyst).The activity and selectivity of A catalyst was studied in different operational conditions.The results showed that the best operational conditions for C2~4 light olefins production were H2/CO=1/1(GHSV=2400h-1) at 260℃ under 0.3MPa total pressure.     

Deactivation studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

A nano-structured iron catalyst for syngas conversion to hydrocarbons in Fischer-Tropsch synthesis (FTS) was prepared by micro-emulsion method. Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen (TPSR-H2), and XRD techniques. Many carbonaceous species on surface and bulk of the nano-structured iron catalysts were completely identified by combined TPSR-H2 and XRD spectra and which were compared with those recorded on conventional co-precipitated iron catalyst. The results reveal that the catalyst deactivation results from the formation of inactive carbide phases and surface carbonaceous species like graphite, and it will be increased when the particle size of iron oxides was reduced in FTS iron catalyst.     

凹凸棒石负载Cu-Fe-Co基催化剂组合体系用于CO加氢制备低碳醇

采用浸渍法(IM)和浸渍燃烧法(IMSC)制备了凹凸棒石(ATP)及凹凸棒石-多孔硅胶微球混合物(ATPS)负载CuFe-Co基改性费托催化剂,通过N_2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、透射电镜(TEM)、H_2-程序升温还原(H_2-TPR)和CO_2-程序升温脱附(CO_2-TPD)等手段对催化剂进行了表征,并将它们应用于CO加氢制备低碳醇反应。结果表明,IMSC较IM制备催化剂更有利于CuO的负载、分散和还原,促进H_2和CO与Cu活性位的接触,但两者的最佳低碳醇合成温度均为280℃。通过对ATP和ATPS负载Cu-Fe-Co基催化剂(CFCK/ATP、CFCK/ATPS)与Cu/ZnO/Al_2O_3(CZA)甲醇催化剂的组合体系的优化,获得较理想的低碳醇合成催化剂组合体系CZA║CFCK/ATPS-IMSC。利用它们之间的"产物转化耦合效应",实现CO转化率为46.3%,低碳醇选择性为39.6%,C_(2+)醇含量为22.7%。     

Silylation of a Co/SiO2 catalyst. Characterization and exploitation of the CO hydrogenation reaction

Several silylated- and nonsilylated Co/SiO2 catalysts have been prepared by reaction of the surface silanol groups with hexamethyldisilazane (HMDS). These samples have been characterized by means of N2 adsorption isotherms, solid-state nuclear magnetic resonance (29Si and 1H), X-ray photoelectron spectroscopy, thermogravimetric analysis, and diffuse reflectance IR spectroscopy. We have focused on the study of the silylated surface stability at high temperatures and in different atmospheres. The characterization techniques have shown that silica silylation after cobalt impregnation leads to a silylated SiO2 surface composed of hydrophobic Si-(CH3)3 species highly stable up to 600-650 K in both oxidizing and reducing atmospheres. However, X-ray diffraction and temperature-programmed reduction have shown that the hydrophobic nature of the silica surface does not affect the metal dispersion and its reducibility. The materials prepared in this way have been tested as catalysts for the Fischer-Tropsch synthesis reaction. The CO conversion reaction rate increased over the silylated catalyst, probably as a consequence of the higher number of available active sites because water adsorption over the catalyst surface is impeded. However, catalyst deactivation was not affected by the hydrophobic nature of the support, suggesting that carbon deposition is the more probable mechanism of cobalt-based catalyst deactivation during the Fischer-Tropsch synthesis.     

间苯二酚-甲醛树脂凝胶对Co/SiO_2催化剂费-托性能的影响(英文)

采用共沉淀法制备了高Co含量的Co/SiO2费托合成催化剂,并向其中添加一定含量的间苯二酚-甲醛树脂凝胶.结果表明,催化剂在393K干燥时,树脂会发生分解,因而仅有少量的含碳凝胶残留在催化剂中.然而,少量碳凝胶的存在显著增加了催化剂的还原度和金属钴的分散度,致使催化剂表面产生更多的活性金属Co,同时,催化剂的孔径也有所增大,因此Co/SiO2催化剂具有更高的反应活性及高碳烃选择性.其中80%Co/SiO2-C催化剂活性及高碳烃的选择性与我们前期报道的一种高活性的80%Co-8%ZrO/SiO催化剂相近.     

Controlled synthesis of cobalt nanocrystals on the carbon spheres for enhancing Fischer–Tropsch synthesis performance

Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method,the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.     

SLURRY FISCHER-TROPSCH/ZSM-5 TWO STAGE PROCESS OF CONVERTING SYNGAS TO GASOLINE 1.PREPARATION AND PROMOTION STUDIES OF PRECIPITATED Fe/Cu/K CATALYST

Precipitated Fe/Cu/K catalvsts with desired properties forFischer-Tropsch synthsis were prepared under optimum precipitationconditions.Effects of pH and temperature of precipitation on catalystproperties were investigated intensively Promotion effect of copper oncatalyst performance was also studied It was found that certain Cu levellowered the catalyst reduction and operation temperatures.made the activityand selectivity stable     

Fe3O4纳米催化剂的制备及其F-T合成性能研究

基于溶剂热合成体系,制备了不同形貌的Fe₃O₄微球和纳米片催化剂,考察了水热合成条件对Fe₃O₄晶粒形貌的影响,并研究了Fe₃O₄纳米催化剂的费托合成(F-T)性能。结果表明,成核和晶体生长速率是控制Fe₃O₄晶体形貌的关键。与传统的沉淀铁催化剂相比,Fe₃O₄纳米催化剂更容易还原和向活性相转变,因此,具有更高的F-T反应活性、低碳烯烃选择性及C₅₊选择性;Fe₃O₄微球催化剂比纳米片催化剂更易维晶粒的稳定,具有更高的反应活性和稳定性。     

TiO2 supported cobalt-manganese nano catalysts for light olefins production from syngas

Cobalt-manganese nano catalysts were prepared by sol-gel method. This research investigated the effects of different cobalt-manganese (Co/Mn = 1/1) loading, pH and calcination conditions on the catalytic performance of Co-Mn/TiO₂ catalysts for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor. It was found that the catalyst containing 30wt%(Co-Mn)/TiO₂ was an optimal catalyst for the conversion of synthesis gas to light olefins especially propylene. The activity and selectivity of optimal catalyst were studied under different operational conditions. The results showed that the best operational conditions were H₂/CO= 1/1 molar feed ratio at 250 °C and GHSV= 1300 h^?1 under atmospheric pressure. Characterization of catalysts was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption measurements.     

INTRAPARTICLE DIFFUSION EFFECTS IN FISCHER-TROPSCH SYNTHESIS Ⅱ.EFFECTS OF PARTICLE SIZE,TEMPERATURE AND PORE STRUCTURE

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费托合成 Fe基催化剂中铁物相与活性的关系

 采用连续共沉淀和喷雾干燥相结合的方法制备了微球形 Fe 基催化剂, 采用 N2 吸附-脱附、X 射线衍射和穆斯堡尔谱等手段, 考察了催化剂在不同还原条件下铁物相的转变, 并在浆态床反应器中评价了催化剂的费-托合成 (FTS) 反应性能. 结果表明, Fe 基催化剂在合成气气氛下首先从α-Fe2O3 转变为 Fe3O4, 然后转变为铁碳化物 (FexC); 还原压力的增大有利于 α-Fe2O3 向 Fe3O4 的转变, 而抑制 Fe3O4 向 FexC 的转变; 还原空速的增加则促进 Fe3O4 转变为 FexC. 催化剂的 FTS 反应活性随着催化剂中 Fe3O4 含量的增加而逐渐下降, 而随着 FexC 含量的增加而逐渐上升.     

焙烧温度对含Mg助剂的铁基催化剂F-T合成反应性能的影响

采用连续共沉淀和喷雾干燥技术相结合的方法制备了Mg助剂的Fe/Cu/K/SiO2催化剂,采用N2物理吸附、XRD、MES 和H2-TPR等表征手段,考察了焙烧温度对催化剂比表面积、体相结构和还原性能的影响。结果表明,随着焙烧温度的升高,催化剂的比表面积降低,平均孔径增大,体相中α-Fe2O3晶粒逐渐增大,催化剂变的越来越难还原,其结构更加稳定。在H2/CO （摩尔比）= 2.2、250 ℃、2.0 MPa和2 000 h－1于固定床反应器考察了焙烧温度对该催化剂F-T合成反应性能的影响,结果表明,随着焙烧温度的升高,催化剂的F-T合成反应活性降低,在运行过程中反应活性逐渐增加直至达到平稳,但达到平稳所需的诱导期越来越长;提高焙烧温度使烃产物分布向重质烃方向转移,有利于降低CH4的选择性,促进重质烃的生成。