SBA-15固载金属氧化物介孔材料的研究进展

介孔分子筛SBA-15具有独特的物理化学性质和广阔的应用前景,成为目前众多研究领域的一个研究热点。本文结合我们自己的工作和国内外相关研究,较全面地阐述了近年来几种SBA-15固载金属氧化物介孔材料的研究状况,并展望了今后其研究、发展方向和应用前景。     

Synthesis of crystallized mesoporous transition metal oxides by silicone treatment of the oxide precursor

Ordered mesoporous transition metal oxides were successfully crystallized after strengthening the amorphous framework by a silica layer, which efficiently protected the original mesoporous structure against crystallization and resulting mass transfer.     

Uptake of curcumin by supported metal oxides (CaO and MgO) mesoporous silica materials

A series of LaMnO₃ perovskites as catalysts for selective reduction of NO by CO were synthesized using microwave and ultrasound assisted sol-gel method. The catalysts were characterized by BET area measurements, Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) techniques. XRD results showed revealed the orthorhobic crystalline structure and with very high purity. SEM analyses proved lower particle size for ultrasound (US) assisted synthesized LaMnO₃. In addition, US assisted synthesized LaMnO₃ presented higher surface area respect to other catalysts, synthesized by the other methods. Results revealed that the ultrasound assisted synthesized catalyst determines the lowest crystallite size, the highest surface area and the highest concentration of O-vacancies and, as a consequence, the highest catalytic activity.

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Catalysts based on cordierite modified with transition metal oxides

Catalysts active in ammonia oxidation have been obtained by the substitution of transition metal (Mn, Fe, Co, Ni, and Cu) ions for Mg ions in the cordierite structure 2MgO · 2Al₂O₃ · 5SiO₂ at 1100°C. Their phase composition, texture, and activity depend on the type and amount of introduced transition metal oxide. The Mn- and Cu-containing catalysts, which consist of substituted cordierites 2(Mg_{1 ? x} M _x )O · 2Al₂O₃ · 5SiO₂ and Mn₂O₃ or CuO crystallites located on their surface, are most active in ammonia oxidation. The catalysts are characterized by a small specific surface area and have large pores, whose total volume is small. The Fe-containing catalysts consist of the Fe-substituted cordierite phase and particles of an iron oxide phase. These particles are mostly located in internal pores of the catalysts and are, therefore, hardly accessible to ammonia molecules. The introduction of Co or Ni oxide leads to the formation of a low-active spinel phase rather than the cordierite phase.     

Dehydrogenation activities of highly dispersed transition metal oxides on NaY zeolite

Highly dispersed α-Fe_2O_3/NaY,NiO/NaY,and CuO/NaY catalyst systems were pre-pared by impregnation method.Dispersion thresholds of the transition metal oxides on NaY" zeolitewere determined by XRD phase analysis.The dispersion capacities of the transition metal oxides on NaYzeolite are much lower than that estimated on the basis of a closed packed monolayer in the micropores.The catalytic activity and selectivity of the highly dispersed oxide catalyst systems for ethylben-zene and cyclohexane dehydrogenation reactions were reported.     

Polymer flame inhibition in presence of transition metal oxides

Summary Transition metal oxides like Fe₂O₃, Ni₂O₃, Co₂O₃ and MnO₂ suppress the combustion of polystyrene. The effect has been explained on the basis of condensed-phase and gas-phase reactions.With 2 figures and 1 table     

New families of supermicroporous metal oxides: the link between zeolites and mesoporous materials

Sol-gel hydrolysis reactions in propanol of two or more metal acetates or alkoxides in n-alkylamines have been found to yield porous mixed oxides with the presence of pores largely in the 10-20 A region.     

Single crystal particles of a mesoporous mixed transition metal oxide with a wormhole structure

A new type of mesoporous mixed transition metal oxide of Nb and Ta (NbTa-TIT-1) has been prepared through a two-step calcination, which consists of single crystal particles with wormhole mesoporous structure.     

Thermal studies of the reactions of vanadium(V) oxide with other transition metal oxides

Studies of the thermal behaviour of binary oxide mixtures containing vanadium(V) oxide (V₂O₅-TiO₂, V₂,O₅- MoO₃, V₂,O₅-ZrO₂ and V₂O₅-ZnO) have shown that the evolution of gaseous oxygen at fairly low temperatures is characteristic of those systems which are eflective catalysts for the oxidation of hydrocarbons. No weight changes were observed with V₂, O₅-ZnO mixtures under these conditions and, in accordance with this, zinc(II) oxide does not enhance the catalytic activity of vanadium(V) oxide. In V₂O₅-containing systems, evolution of oxygen occurs during the reduction of V₂O₅ to V₂O₄. This process is accelerated in the presence of certain metal oxides and such acceleration may be caused by structural interactions at the interface of the oxides. Among the systems studied, the formation of compounds such as Mo₆V₉O₄₀ is thought to be of little significance from the catalytic point of view.

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Zusammenfassung Die Untersuchung des thermischen Verhaltens vanadium(V)-oxid-haltiger binärer Mischungen (V₂O₅-TiO₂, V₂O₅-MoO₃, V₂O₅-ZrO₂ und V₂O₅-ZnO) ergab, daß die Entwicklung gasförmigen Sauerstoffs bei niedrigen Temperaturen für jene Systeme, welche effektive Katalysatoren der Oxidierung von Kohlenwasserstoffen sind, charakteristisch ist. Keine Gewichtsänderungen wurden bei Mischungen von V₂O₅-ZnO unter diesen Bedingungen beobachtet und dementsprechend fördert Zink(II) Oxid die katalytische Aktivität von Vanadium(V) Oxid nicht. In V₂O₅-haltigen Systemen erfolgt die Sauerstoffentwicklung während der Reduktion von V₂O₅ zu V₂O₄. Dieser Vorgang wird durch die Anwesenheit gewisser Metalloxide beschläunigt und kann durch strukturelle Wechselwirkungen an der Grenzfläche der Oxide gedeutet werden. Bei den untersuchten Systemen wird die Bildung von Verbindungen wie Mo₆V₉O₄₀ vom Gesichtspunkt der Katalyse als wenig bedeutend betrachtet.

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Résumé L'étude du comportement thermique de mélanges d'oxydes binaires contenant de l'oxyde de vanadium(V) (V₂O₅-TiO₂, V₂O₅-MoO₃, V₂O₅-ZrO₂ et V₂O₅-ZnO) a montré que le dégagement de gaz oxygène à température relativement faible est caractéristique des systèmes qui sont des catalyseurs actifs de l'oxydation des hydrocarbures. Avec les mélanges V₂,O₅-ZnO, on n'a pas observé de variations pondérales dans les mêmes conditions et, en accord avec l'observation faite, l'oxyde de zinc(II) n'augmente pas l'activité catalytique de l'oxyde de vanadium(V). Dans les systèmes contenant V₂O₅, le dégagement d'oxygène a lieu au cours de la réduction de V₂O₅ en V₂,O₄. Cette réaction est accélérée en présence de certains oxydes métalliques. Le phénomène d'accélération peut être dû à des interactions structurales à l'interface des oxydes. Dans les systèmes étudiés, la formation de composés comme Mo₆V₉O₄₀ est considérée de peu d'importance du point de vue catalytique.

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, (V₂O₅-iO₂, V₂O₅-₃, V₂O₅-ZrO₂ V₂O₅-ZnO), , , . V₂O₅-ZnO , , () . , , V₂O₅ V₂O₄. . Mo₆V₉O₄₀ , .

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The authors would like to thank Dr. D. J. Cole for carrying out the experimental work.     

Three-coordinate metal centers in extended transition metal oxides

The n = 3 Ruddlesden-Popper phase Sr3LaFe1.5Co1.5O10+/-delta is capable of sustaining O contents as low as O7.5 with a mean metal oxidation state of +2 and three coordination at the central site in the trilayer of originally octahedral transition metal sites. The shortening of the axial bonds to the flanking octahedral layers stabilizes the low oxidation state and consequent unusual low coordination number of the Fe2+ and Co2+ cations within the extended structure.     

Dehydrogenation of 1-methylcyclopentene in the presence of oxide catalysts

Summary We studied the dehydrogenation of 1-methylcyclopentene in the presence of an alumina-molybdenum catalyst at 600°, a flow rate of 1.0 h^–1 and residual pressures of 20 and 100 mm of Hg. In both cases the yield of methylcyclopentadiene amounted to 30% based on the starting hydrocarbon.We express our deep appreciation to É. G. Ostapenko and E. D. Tulupova for assistance in performing the Chromatographic analyses.Translated from Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 5, pp. 912–914, May, 1964     

Container effect in nanocasting synthesis of mesoporous metal oxides

We report a general reaction container effect in the nanocasting synthesis of mesoporous metal oxides. The size and shape of the container body in conjunction with simply modifying the container opening accessibility can be used to control the escape rate of water and other gas-phase byproducts in the calcination process, and subsequently affect the nanocrystal growth of the materials inside the mesopore space of the template. In this way, the particle size, mesostructure ordering, and crystallinity of the final product can be systemically controlled. The container effect also explain some of the problems with reproducibility in previously reported results.     

Silicate coatings on titanium, modified with transition metal oxides and their activity in CO oxidation

CuO+M _x O _y /TiO₂+SiO₂/Ti composites (M = Mn, Fe, Co, Ni) were produced by plasma-electrolytic oxidation and impregnation, followed by annealing. The elemental and phase composition of these composites were examined and their activity series in CO oxidation was determined.     

Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption-desorption measurements.     

Synthesis of thermally stable mesoporous cerium oxide with nanocrystalline frameworks using mesoporous silica templates

Highly ordered mesoporous cerium oxides, composed of nanocrystalline pore walls and exhibiting high thermal stability even at 973 K, were synthesized using mesoporous silica templates with hexagonal p6mm and cubic Ia3d symmetries.     

Poly(ethylene oxide)-based surfactants as templates for the synthesis of mesoporous silica materials

Various mesoporous silica solids were prepared by using poly(ethylene oxide)-based surfactants as templates in a neutral, fluoride, or moderately acidic medium, and their properties examined by different physical techniques. Precipitation in an acid or neutral medium provided materials of pore size in between those of micropores and mesopores irrespective of the molecular size of the surfactant. On the other hand, syntheses in a fluoride-containing medium yielded mesoporous materials with pore diameters over the range 36-84 A that increased with increasing surfactant size. All materials possessed specific surface areas above 650 m(2)g(-1) and high pore volumes-particularly those obtained in a fluorinated medium. The conditions used in the syntheses and the fact that all produced highly disordered porous materials suggest that their mechanism of formation is essentially of the N(0)I(0) neutral type. The materials obtained in the presence of fluoride ion, which promote the condensation of siliceous species, retain greater amounts of surfactant and exhibit increased cross-linking and decreased particle sizes, which results in textural mesoporosity.