MCM-22、MCM-49和MCM-56分子筛的表征

MWW结构分子筛是一类新型的催化材料，具有独特的10元环孔道和12元环孔穴结构、优良的水热稳定性和特殊的酸中心分布，在多种反应中表现出良好的催化活性。以六亚甲基亚胺为模板剂，合成了具有MWW结构的MCM-22、MCM-49和MCM-56三种分子筛，并采用XRD、BET、TG/DTG和SEM手段对合成分子筛进行了表征，表明它们具有相同的单层结构，彼此之间的区别只有层间排列的结合层度和结合方式不同。MCM-56是薄层结构，晶体的层数少，MCM-22和MCM-49是多层结构，层数多。MCM-22的层间结合比较疏松，MCM-49的层间结合比较紧密。     

碱处理制备介孔-微孔沸石分子筛的影响因素及其应用研究进展

综述了碱处理制备介孔-微孔沸石分子筛的影响因素,包括碱处理条件、沸石分子筛硅铝比和模板剂对碱处理脱硅形成介孔的影响。评述了碱处理所制备介孔-微孔沸石分子筛在应用方面所取得的进展,重点介绍了它们在烷基化、异构化、裂化和醇烃化等催化反应中的应用。通过碱处理引入介孔可极大地缩短分子在沸石微孔道中的扩散距离,从而增强表观催化反应活性及提高催化剂的稳定性。提出了今后研究的重点为：阐明碱处理引入介孔的形成机理和碱处理对分子筛骨架结构、酸性的影响,拓展碱处理制备介孔-微孔沸石分子筛的应用 范围。     

Catalytic behavior of vanadium substituted mesoporous molecular sieves

A series of V-MCM-41 samples with different pore sizes has been systematically investigated with both gas and liquid phase reactions. Methanol oxidation has been performed in the gas phase on these catalysts. Turnover frequencies are normalized by oxygen uptake measured under reaction conditions. A strong effect of pore size on the catalytic activity was observed in the form of a “volcano curve” and may be correlated with a variation in the local bond angle of Si–O–V. Considering this effect, the catalytic activity may be ‘tuned' to maximum by varying the pore size. As expected, the same effect was observed in the liquid phase oxidation of cyclohexene. In order to interpret the pore size effect, the reaction rates of both the gas phase and liquid phase oxidation were then correlated with the variation of edge energies of V K-edge XANES on these MCM-41 catalysts. Additional reactions were performed in the liquid phase to compare the activity of V-MCM-41 with that of crystalline vanadium and titanium silicalite zeolites. The possible causes of the difference in the catalytic behaviors of these materials is also discussed.     

Remarkable effect of the preparation method on the state of vanadium in BEA zeolite: Lattice and extra-lattice V species

The state of vanadium in two BEA zeolites is investigated by XRD, FTIR, DR UV–vis and EPR. One of the samples, VAlBEA (1.3 wt.% of V), is prepared by conventional ion exchange and the other, VSiBEA (2.0 wt.% of V), by a two-step postsynthesis method involving dealuminated BEA zeolite. No structural changes are observed after incorporation of vanadium into AlBEA zeolite by ion-exchange method. In contrast, the impregnation of SiBEA with V(IV) (VOSO₄) precursor leads to an increase of unit cell parameters of the BEA, to the consumption of silanol groups in vacant T-sites and incorporation of V in the framework of BEA zeolite as well dispersed tetrahedral V(V) species. NO and CO used as IR probe molecules, DR UV–vis and EPR allow to establish the oxidation state of vanadium in as prepared, oxidized, activated and reduced VAlBEA and VSiBEA zeolites. The IR spectra of oxidized, activated and reduced VAlBEA samples are very similar. It suggests that V introduced by ion exchange in extra-lattice position is stabilized on all samples in similar oxidation state. CO adsorption evidence the presence of vanadium in IV oxidation state via IR bands at about 2200 and 2180 cm⁻¹ assigned to V(IV)–CO monocarbonyl and V(IV)–(CO)₂ dicarbonyl species. In contrast, the oxidation state of V in VSiBEA changes strongly in function of calcinations in oxygen, outgassing at high temperature (773 K) and reducing with hydrogen at high temperature (873 K). This shows that lattice tetrahedral V species change easily oxidation state and this property allows them to be good candidate as active site of selective redox reactions.     

锡硅分子筛：新型杂原子分子筛催化材料

锡硅分子筛能高效催化含氧烃转化，因此其具有重要潜在工业应用价值。本文简述了锡硅分子筛的骨架锡判定、合成方法、多级孔合成研究及应用领域。XRD、NMR和EXAFS等表征方法可以判别锡硅分子筛内锡原子的配位形式及落位。合成锡硅分子筛通常采用水热晶化法、后插入法和干胶转化法。碱性水热合成过程中匹配锡源和硅源的水解速率是使锡原子高效插入分子筛骨架的关键。中性水热合成方法制备的锡硅分子筛结晶度较高，但存在使用剧毒含氟试剂和晶粒较大等问题。干胶转化法可在短时间内制备高结晶度含锡分子筛，但该法存在传质传热差等弊端。采用后插入法可将锡原子插入到不同拓扑结构的分子筛骨架，但锡原子易发生聚集。同时，采用碱处理、硬模板剂法和软模板剂法合成多级孔锡硅分子筛，可提升骨架锡活性中心的可接近性。其中，采用软模板剂法展示出独特的优势，其可制备介孔分布均匀且贯通性良好的多级孔锡硅分子筛。另外，锡硅分子筛的骨架锡原子对含氧官能团具有优异的活化作用，因此其在Meerwein-Ponndorf-Verley-Oppenauer反应、葡萄糖异构化反应、乳酸及乳酸酯制备及Baeyer-Villiger氧化反应中都展示了良好的催化效果。     

光催化苯羟基化制苯酚研究进展

苯酚是一种重要的有机化工基础原料,应用广泛。近年来,随着苯酚需求量的增加和生产苯酚的主流工艺——异丙苯法与可持续发展的理念冲突,越来越多的研究者将目光投向苯直接羟基化制苯酚。主要从吸收波长范围在紫外光区和可见光区催化剂的角度介绍光催化苯直接羟基化氧化制苯酚的研究进展,当前光催化苯制苯酚研究中,钒氧化物催化剂和贵金属催化剂活性组分易流失,钒氧化物催化剂寿命短,纳米金催化剂活性衰减快,铁系物催化剂和氧化钛催化体系选择性偏低,这也是今后需要解决的重点。     

A new synthesis procedure for titanium-containing zeolites under strong alkaline conditions and the catalytic activity for partial oxidation and photocatalytic decomposition

A new synthesis procedure for titanium-containing aluminosilicate zeolites has been obtained using a clear colloidal dispersion (sol) which was prepared with titanium isopropoxide, water, hydrochloric acid and colloidal silica, Ludox. When NaY, KL, offretite, mordenite and ZSM-5 zeolites were crystallized from the sol following conventional hydrothermal crystallization procedures, all the aluminosilicate zeolites showed the same X-ray absorption fine structure at the Ti K edge indicating framework Ti. The zeolites showed remarkable catalytic activity for the partial oxidation of cyclohexene using H₂O₂ as an oxidant and the photocatalytic decomposition of trichloroethene using water.     

Au-SBA-15介孔分子筛的合成及其催化性能研究

利用原位技术将Au物种引入介孔分子筛SBA-15，得到具有氧化活性中心的Au-SBA-15分子筛。通过X射线衍射(XRD)、FT-IR和紫外可见漫反射(UV-Vis)等手段进行表征。结果表明，Au物种已进入SBA-15的骨架。这种新型催化剂在环己烷催化氧化反应中表现出较好的催化活性，在不需添加任何助剂的条件下，以O₂为氧化剂，环己烷的转化率可达9.3％，酮醇选择性可达92.8％。     

Ti-MCM-41分子筛研究进展

介绍了Ti-MCM-41分子筛的合成方法、物性表征、表面硅烷化、负载杂原子改性研究及其近年来在催化领域的应用。Ti-MCM-41分子筛具有优异的选择催化氧化性能，还具有良好的光催化活性。可用于烃类的选择性氧化、环氧化和羟基化反应，也可作为光催化剂应用于有机物的加氢、降解反应。     

Degradation of naphthalene by liquid-phase oxidation over ordered mesoporous V-<Emphasis Type="Italic">m</Emphasis>-TiO<Subscript>2</Subscript> catalysts

The vanadium species doped mesoporous anatase TiO₂ samples were successfully synthesized via a facile one-pot EISA method. The physical chemical properties were characterized by XRD, N₂ sorption, UV–Vis, Py-IR, SEM, TEM and XPS techniques, and the catalytic performance were also investigated in the oxidation of naphthalene with hydrogen peroxide. The vanadium species with 4+ or 3+ valence can be homogeneously tetrahedrally incorporated into the mesoporous framework of anatase TiO₂, and it would increase the Brønsted acidity resulting in the promotion of catalytic performance. Naphthalene conversion of 26.1% can be obtained over 10 V-m-TiO₂ sample in the absence of ascorbic acid. The catalytic performance was much higher than other samples with the same loading of vanadium species prepared by impregnation or coprecipitation even though they were in the presence of ascorbic acid as reductant. Although the intrinsic reusability for 10 V-m-TiO₂ sample was poor, the catalytic performance was promoted and the catalytic reusability can be kept well by introduction of ascorbic acid into the oxidation system even after repeated reaction for five times.     

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular structure of vanadium in water and in the solid state and an overview of the spectroscopic techniques enabling to study the chemistry of supported vanadium oxides. In the second part, it will be shown that advanced spectroscopic tools can be used to obtain detailed information about the coordination environment and oxidation state of vanadium oxides during each stage of the life-span of a heterogeneous catalyst. Three topics will be discussed: (1) the molecular structure of supported vanadium oxide catalysts under hydrated, dehydrated and reduced conditions, including the parameters, which influence the molecular structures formed at the surface of the support oxide; (2) elucidation of the active surface vanadium oxide during the oxidation of methanol to formaldehyde, the reaction mechanism and the vanadium oxide---support effect; and (3) deactivation of fluid catalytic cracking (FCC) catalysts by migration of vanadium oxides and the development of a method preventing the structural breakdown of zeolites by trapping the mobile vanadium oxides in an aluminum oxide coating.     

分子筛的补铝及其催化性能研究

本文介绍了分子筛的补铝方法及其补铝后分子筛的催化性能。按所用的补铝溶液性质可分为 Na OH等碱性溶液补铝法、Al Cl3 和 HCl酸性溶液补铝法及含羟基有机酸溶液补铝法 ,补铝机理涉及晶格缺陷位补铝、非骨架位表面反应以及同晶取代三种。补铝的分子筛表面酸性质发生了变化 ,改善了某些催化反应性能     

Structure modification of mordenite through isomorphous Ti substitution: Characterization and catalytic properties

The introduction of Ti atoms by means of TiCl₄ treatment and hydrothermal synthesis has been applied to mordenite zeolite with different structures from silicalite. The incorporation of Ti into the mordenite framework is demonstrated by XRD, FTIR,²⁹Si MAS NMR techniques, and tested with catalytic oxidation reactions. Ti-Al-mordenite catalyses the oxidation ofn-hexane, cyclohexane and benzene with hydrogen peroxide under very mild conditions. These reactions can be performed in methanol, acetonitrile and water as solvents. The rate of the reaction is strongly affected by the kind of solvent.     

New strategy of creation of local catalytic sites in definite electronic and coordination states

Atomic-scale engineering of catalytic functions of isolated redox sites in confined environments of zeolitic channels is proposed as a new approach to the investigation of structure-properties relationship in heterogeneous ‘biomimetic’ catalysis. It is shown that the design of such catalysts, on the base of high-silica zeolites, containing isolated transition-metal cations as active redox sites, may present promising opportunities for creation of new types of contacts from a practical point of view. A detailed analysis of transition-metal cation incorporation into high-silica zeolites by either conventional or solid-state exchange is given. Stabilization of one or several transition-metal ions by matrices of high-silica zeolites (mainly H-ZSM-5) is discussed. The influence of different factors on the processes of cationic-species stabilization is analyzed. These data are correlated with the results of catalytic testing in reactions of total oxidation of hydrocarbons (HC), direct decomposition of NO_x and SCR of NO_x by HC. The relationship between catalytic activity and selectivity of cationic sites and their coordination and electronic state, regulated by either thermal treatment or introduction of different anionic ligands, is analyzed.     

Key Aspects of Catalyst Design for the Selective Oxidation of Paraffins

This review examines some aspects in the development of heterogenous catalysts for the oxyfunctionalization of light paraffins. Particular attention is devoted to the raction of paraffin oxydehydrogenation to olefins and of n-butane oxidation to maleic anhydride. Most catalyst compositions are based on vanadium oxide as the main component, and the peculiar properties of this element with respect to the catalytic performance are discussed. These properties are also examined in ligh of the stability of the product of partial oxidation towards consecutive unselective oxidation reactions, and with respect to the mechanism of paraffin activation.     

生物基乳酸（酯）制丙烯酸的工艺研究

以乳酸（酯）脱水反应为模型反应,分别考察了X、Y、ZSM-5和SBA等分子筛、硫酸盐、磷酸盐以及复配催化剂的催化性能。结果表明,适当调节分子筛催化剂的酸碱度,实现多种催化剂的复配应用,催化剂性能较好,丙烯酸及其酯的总选择性达80.3%。     

The effect of vanadium sources on the synthesis and catalytic activity of VMCM-41

Mesoporous VMCM-41 was synthesized hydrothermally using various vanadium sources, viz, tetravalent vanadium such as vanadyl sulfate and vanadyl acetylacetonate, as well as pentavalent vanadium like sodium vanadate and ammonium vanadate. The influence of different vanadium sources on the framework substitution of vanadium, as well as their catalytic activity for the oxidation of cyclohexane, was investigated. Among the different vanadium stocks, the tetravalent vanadium sources showed maximum vanadium incorporation in the silicate framework of MCM-41. As a consequence, these catalysts gave much higher substrate conversion and excellent product selectivity. On the other hand, the catalysts prepared from pentavalent vanadium sources showed lower activity owing to the smaller amounts of vanadium in the matrix. Although the activity of the catalyst slightly decreased after first recycle as due to leaching of small amounts of active vanadium species, it however remained nearly the same even after several recycles. This was further confirmed by washing experiments wherein non-framework vanadium ions were removed upon ammonium acetate treatment; the washed catalysts showed a similar activity to those of the recycled catalysts. Thus, recycled/washed VMCM-41 behaves truly as heterogeneous catalyst. Furthermore, the influence of pore size of the catalyst was tested for the oxidation of bulkier substrate, viz, cyclododecane.     

Hydroxylation of benzene and phenol in presence of vanadium grafted Beta and ZSM-5 zeolites

Vanadium grafted zeolites type Beta and ZSM-5 were investigated for direct oxidation of benzene to phenol and hydroxylation of phenol with hydrogen peroxide in acetonitrile media at 353 K. The introduction of vanadium was done by reductive solid state ion exchange. The morphological characterisation of samples and the stability of the vanadium sites were examined before and after the reaction by applying FTIR, UV–Vis techniques and reduction/oxidation cycles (TPR/TPO). The results proved that the vanadium sites had retained their multiple oxidation state when used in liquid phase oxidation at high vanadium atom efficiency for the reaction product.     

Preparation, characterization and catalytic properties of unsupported vanadium sulphides

This work concerns the preparation and the ability of unsupported vanadium sulphide to catalyze different reactions representative of hydrotreatment. Pure V₂S₃ was prepared by decomposition of ammonium thiovanadate at relatively low temperature. The reactivity of the decomposed solid towards oxygen confirms the high oxophilic character of this group V sulphide. The oxidation mechanism involves a superficial oxidation followed by an insertion of oxygen into the lacunar structure of the solid. The comparison of the catalytic properties of this chalcogenide with those of molybdenum or tungsten sulphides shows the superiority of vanadium sulphide for performing hydrogenation reaction of various cyclic molecules. In contrast, the hydrodesulphurization properties are of the same order.     

Effects of base metal promoters in VOC catalysts for chlorocarbons and n-Hexane Oxidation

The oxidation reactions of dichloromethane, dichloroethane and n-hexane were carried out over honey-comb type platinum basic VOC catalyst (BVC) containing vanadium, chromium, manganese, cobalt, copper or barium. In dichloromethane and dichloroethane catalytic oxidation up to 450 °C, chromium was found as the most active component. Although vanadium was also effective initially, it was deactivated after treatment in the furnace at 800 °C for 120 hours. Chromium, cobalt, vanadium and barium promoted catalysts showed higher activities than BVC in the reaction of n-hexane.