合成气脱除羰基铁净化剂研究进展

介绍了羰基铁的分析方法以及合成气脱除羰基铁净化剂的脱除方法,综述国内外合成气脱除羰基铁净化剂的脱除性能,并对以后脱除羰基铁净化剂的研究提出建议。     

离子液体桥连的聚苯乙烯负载型2,2,6,6-四甲基哌啶氧化物催化剂的稳定性

研究将小分子催化剂2,2,6,6-四甲基哌啶氧化物通过化学共价键键合离子液体桥连的方法负载在聚苯乙烯氯球上,制备负载型催化剂。考察其在N₂气氛的热稳定性、溶剂中的溶胀性以及两相反应体系(NaClO/NaBr、CH2Cl₂/H₂O)中的化学稳定性。结果表明,负载型催化剂在反应温度低于180 ℃表现出较好的热稳定性,且在苯甲醇催化氧化过程中可以循环使用20次,苯甲醇转化率大于95%。所得催化剂具有亲水亲油的两亲性,适用于两相体系的催化环境,比直接负载2,2,6,6-四甲基哌啶氧化物的催化剂有更好的耐溶剂性及稳定性。     

Investigation of the sintering mechanisms of GDC pellets obtained by the compaction of nanostructured oxide microspheres

The sintering behavior of green pellets obtained from nanostructured Ce_0.8Gd_0.2O_1.9 submillimetric microspheres is studied in the present paper. Corresponding shrinkage rate curve shows a two‐step densification in dynamic conditions, with the presence of two successive extrema, at 1200 K and 1500 K. To fully understand this non‐common densification behavior, an iterative study was performed. Multiple characterizations point out multiscale organization of the matter with temperature giving rise to differential sintering stages of two different particle size classes. Concerning 1200 K‐first shrinkage rate maximum, it corresponds to the densification of nanometric aggregates of crystallites into submicrometric pre‐sintered aggregates, resulting in a specific porous microstructure with residual open porosity. As‐generated porosity combined with submicron size of pre‐sintered aggregates thus prevent from a homogeneous sintering illustrated by a single maximum shrinkage rate. Finally, the second maximum shrinkage rate at 1500 K can then be associated to optimal temperature for submicrometric particles sintering.     

Synthesis of monodispersed micaceous iron oxide by the oxidation of iron with oxygen under hydrothermal conditions

The oxidation behavior of iron powder with oxygen was investigated in 5–25 m NaOH solutions at 5 MPa of oxygen partial pressure and 130–290°C, where m = mol(kg H₂O)^?1. Monodispersed micaceous iron oxide, α-Fe₂O₃, was synthesized by the oxidation of iron powder with 5 MPa of oxygen in 10–16 m NaOH solutions at 250–270°C. The diameter of micaceous iron oxide greatly changed depending on the reaction conditions such as the temperature, reaction time and concentrations of NaOH and coexisting ions.     

Mechanism of potassium loss by desorption from an iron oxide catalyst for the styrene process

Several types of experiments have been done with molecular beam and mass spectrometric methods to characterize the desorption processes of potassium from a commercial styrene (potassium promoted iron oxide) catalyst. The loss of potassium as desorption of K is found to be mainly thermal, with an activation energy close to 1.0 eV (97 kJ/mole), which probably is associated with release of K from the initially bound positions in the bulk. The directly measured rate of loss as K appears too small to account for the experimentally observed total rate of loss. A new loss mechanism as electronically excited but not easily field ionizable potassium atoms is detected with an activation barrier of 1.7 eV (164 kJ/mole). Excited states may be important for the total loss both through direct emission of excited K atoms, and since excited states may give rise to cluster formation at the surface and more rapid loss as clusters K_n.     

Variations in the porous structure of a Cr2O3/Al2O3 catalyst by coke deposition

The porous structure of a Cr₂O₃/Al₂O₃ catalyst deactivated by coke deposition has been studied at various levels of coke content. The results obtained agree satisfactorily with a model of uniform coverage of the catalyst pores, thus allowing the hypothesis of pore blockage to be discarded under the conditions investigated.     

用SnO/TiO2/ZnO作催化剂合成DOP的研究

用SnO/TiO_2/ZnO作催化剂合成邻苯二甲酸二(2-乙基)己酯(DOP)。当n(苯酐):n(2-EH)=1:(2.3～2.4),反应温度200～220℃,催化剂用量为反应物总量的0.2％～0.3％时,可得到优级品的DOP。     

Fischer-Tropsch synthesis: Impact of potassium and zirconium promoters on the activity and structure of an ultrafine iron oxide catalyst

Slurry phase Fischer-Tropsch synthesis was conducted with an ultrafine iron oxide catalyst promoted with either 0.5 at% K or 1.0 at% Zr or both. Pretreatment in CO yielded higher conversions and a more stable catalyst than activation in hydrogen or synthesis gas. Hydrogen pretreatment of K promoted catalysts and synthesis gas activation in general were less effective. Mössbauer spectroscopy and XRD showed-Fe₅C₂ and -Fe_2.2C were formed during pretreatment in CO and did not depend on promoters present. Catalysts pretreated in H2 were reduced to metallic Fe and Fe₃O₄; promotion with K and Zr decreased the extent of reduction. Hydrogen pretreated catalysts, promoted with K, lost surface area and carbided rapidly under synthesis conditions. Activation in synthesis gas reduced all catalysts to Fe₃O₄. Subsequent synthesis did not affect the phase present for the unpromoted and Zr promoted catalysts while those promoted with K formed -Fe₅C₂ and -Fe_2.2C. It is concluded that pretreatment type is more important to the catalyst activity during the early period of synthesis than the impact of promotion with K and/or Zr and that changes in the bulk composition of iron catalysts do not necessarily correlate with changes in activity.     

Preparation,characterisation and activity of an iron/sodalite catalyst for the oxidation of methane to methanol

An iron sodalite catalyst similar to that reported to have good selectivity for the oxidation of methane to methanol by Lyons et al. has been prepared, tested and characterised. In a limited range of temperature at 34 bar total pressure the selectivity of the catalyst to methanol is a little better than that of an empty silica glass reactor. Before reaction, X-ray powder diffraction and Mössbauer spectroscopy confirm the presence of Fe(III) in the sodalite framework. After reaction Mössbauer spectroscopy identifies Fe(II) and also small particles of iron(III) oxide, < 1 m in size.     

Preparation of silica/poloxamer composite by sol-gel process and pore control of silica gel obtained from the composite

Silica gels that controlled the pore size were prepared by calcination of silica/organic polymer (50/50 wt %) composites prepared by the sol-gel process. Poly(ethylene oxide) (PEO)-poly(propyrene oxide) (PPO)-PEO triblock copolymers, which are called poloxamers, were used as an organic polymer. The pore control of the silica gels was carried out by changing the molecular weight of PEO or PPO in the poloxamers. The silica gels obtained by the above procedure had a dual pore size of around 4 nm and below 2 nm in diameter, and the specific surface area was 500–1000 m²/g. The poloxamer molecules were supposed to be dispersed monomolecularly in the composites. Therefore, the pore structure of the silica gels reflected the structure of the poloxamer and, particularly, the radius of gyration of PPO in the composites. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 763–768, 1997     

Planar defect of the nano-structured zinc oxide as the site for stabilization of the copper active species in Cu/ZnO catalysts

The catalytic activity of CuZn catalysts in the synthesis of methanol is related to those reduced Cu species, which originate from the Cu_xZn_1−xO solid solution of wurtzite-like structure. Copper cations in the Cu_xZn_1−xO solid solution are localized in the extended stacking faults of the ZnO lattice. Copper sites could be supposedly described as the product of introducing (OH)Cu(OH) to the planar defects of zinc oxide structure. Hydroxyl groups stabilize the planar defects of ZnO. The process of the samples reduction leads to the formation of flat Cu⁰ particles over the surface of zinc oxide. The planar defects of ZnO structure are preserved in the reduced state. During the reoxidation, copper atoms return back to the extended stacking faults of ZnO as the tape-like clusters of flat-square coordinated copper cations.     

Microstructure of LaNiO3 thin films obtained by the spin-on technique from citrate precursors

The morphology of perovskite LaNiO₃ (LNO) thin films is a very important feature considering the fact that they could be used as an electrode material in ferroelectric devices. In this work, LNO films were prepared from citrate precursors. The films were deposited on Si (100) and Pt covered Si substrates [Pt (111)/Ti/SiO₂/Si] using the spin-on technique. The phase composition of the films was confirmed by X-ray powder diffraction analysis, while the microstructures were investigated by atomic force microscopy. The influence of the metal ion:citric acid:ethylene glycol ratio on the morphology of the films was investigated. After optimization of these parameters, very homogenous, uniform and crack-free LNO films were obtained.     

Synthesis of Hard Materials by Field Activation: The Synthesis of Solid Solutions and Composites in the TiB2–WB2–CrB2 System

The synthesis of solid solutions of (Ti,W,Cr)B₂ from elemental reactants using the field-activated, pressure-assisted synthesis method and employing the SPS apparatus was investigated. The nature of the products depended on temperature; they were nearly pure solid solutions at 1900°C with minor amounts of β-WB. The product density and microhardness depended on the temperature of synthesis for the same value of applied pressure (64 MPa). Samples with the highest density (94%) corresponded to a hardness of 22.7 GPa. When annealed at 1500°C, the solid solutions decomposed, precipitating a (W,Ti,Cr)B₂ phase in a spinodal form. In addition, β-WB precipitates in the form of thin (0.4–5.3 nm) layers were observed. They existed in a 60°/120° orientation to the (Ti,W,Cr)B₂ matrix, in agreement with previous observations. Highly faceted, small (nanosized) pores associated with the β-WB precipitates were also observed.     

助剂Al改善Co/ZnO催化剂F-T反应性能的研究

通过均匀沉淀法制备Zn O,将其作为Co基催化剂载体,评价Co/Zn O催化剂的F-T反应性能,研究发现,助剂Al可以改善Co/Zn O催化剂失活现象。采用XRD和H2-TPR对催化剂进行表征。结果表明,Co/Zn O催化剂主要因为反应过程中的烧结导致失活,添加助剂Al有效缓解催化剂的烧结现象,Al质量分数为0.1%时,不仅明显改善催化剂的反应稳定性,还提高催化剂的F-T反应活性。     

合成气费托合成制重质烃Ru-Co/SiC催化剂的制备及性能

费托合成是以合成气生产清洁燃料和其他化学品的重要途径。传统费托合成产物遵循A-S-F分布,只有甲烷和重质烃的选择性没有极限值。因此,费托合成研究以最大程度地合成重质烃,提高合成产物中重质烃的选择性为目标。基于此,首先详细探究了Al₂O₃、SiO₂和SiC载体对费托反应性能的影响。结果表明 Co/SiC催化剂具有最高的CO转化率（83.5%）和C₅₊选择性（80.3%）。与浸渍法相比,原位还原法更为有效地引入Ru到Co/SiC催化剂,将C₅₊选择性提高至90.1%。Ru助剂能在保持较高催化活性不变的前提下,有效提高Co/SiC催化剂C₅₊选择性。催化剂表征（XRD、H₂-TPR、XPS、H₂-化学吸附和TEM）结果表明,Ru能与Co发生相互作用,提高了催化剂的可还原性和活性组分的分散性,进而改善了Co/SiC催化剂重质烃的选择性。     

Effect of complexing agents on the electrochemical performance of LiFePO4/C prepared by sol-gel method

ABSTRACT: LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO4/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g-1 at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g-1, and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO4/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO4/C via sol-gel method.     

SO_4~(2-)/TiO_2-Al_2O_3复合固体超强酸催化合成柳酸异戊酯的研究

采用共沉淀法制备了固体超强酸SO42-/TiO2-Al2O3,首次将其用于催化柳酸与异戊醇的酯化反应,研究了各种因素对产物收率的影响,确定了反应的最佳条件:催化剂焙烧温度为500℃,催化剂中n(Ti):n(Al)=2:1,n(醇):n(酸)=1.8:1,反应时间3h,反应温度120～140℃,催化剂用量1.0g,带水剂(甲苯)用量为10mL,该条件下,柳酸异戊酯收率高达98％,并推断出催化剂酸强度为:-16.02相似文献   

A silica supported Fe-Co bimetallic catalyst prepared by the sol/gel technique: Operating conditions, catalytic properties and characterization

A Co/Fe catalyst was prepared using the sol/gel technique in order to study its catalytic activity and selectivity in the Fischer-Tropsch synthesis. The effect of a range of operation variables such as pressure, temperature and H₂/CO molar feed ratio on the catalytic performance of 40%Fe/60%Co/15 wt.%SiO₂/1.5 wt.%K catalyst was investigated. It was found that the optimum operating conditions is a H₂/CO = 2/1 molar feed ratio at 350 °C temperature and 3 bar pressure. Characterization of both precursor and calcined catalysts was carried out using XRD, SEM, EDS, TPR, BET surface area measurements and thermal analysis methods such as TGA and DSC. It was observed that all of the different operation variables influenced the structure, morphology and catalytic performance of the catalysts.     

On the fabrication of functional graded 3Y-PSZ/316L materials by SPS: Process optimization and characterization of the obtained products

Dense and crack free six-layered functional graded materials were successfully produced by Spark Plasma Sintering by combining 3 mol% Y₂O₃-partially stabilized ZrO₂ (3Y-PSZ) and 316L stainless steel. All the sintered products consisted of a steel free layer on one side and a cermet composite containing 50 vol% of both constituents on the opposite side. Conversely, the stainless steel concentration in the interlayers was progressively changed following diverse spatial profiles.It was found that the temperature interval from 1080 to 1180 °C required for the full consolidation from the 50 vol% composite layer to the 3Y-PSZ one, respectively, can be reached when adopting a specific die configuration where the cross section was varied from 30 to 28 mm, respectively. Correspondingly, the densification level of each layer, as well as the related hardness and fracture toughness properties, were highly enhanced with respect to the standard cylindrical die. In addition, a significant improvement of the material toughness was obtained when the material concentration exponent was decreased from 2 to 1, whereas this effect tends to vanish when such parameter was further reduced to 0.5.