钛硅分子筛催化剂的研究进展

钛硅分子筛催化剂的研究进展张小明张兆荣索继栓１）李树本（中国科学院兰州化学物理研究所精细石油化工中间体国家工程研究中心兰州７３００００）关键词钛硅分子筛催化氧化中孔分子筛分类号Ｏ６４３．３２含钛催化剂在有机化合物氧化反应中的作用是众所周知的［１，２］...     

钛硅分子筛TS—1催化环己酮氨氧化制环己酮肟

对钛硅分子筛ＴＳ－１催化环己酮氨氧化制环己酮肟的研究结果表明，提高催化剂的投料量、提高分子筛的钛硅比和降低Ｈ２Ｏ２的空速，有利于提高氨氧化反应的转化率和生，降低氨／酮比不利于氨氧化反应，适宜的氨／酮摩尔比应该在２．０以上，适宜的氨氧化反应温度是８０℃在右，过低和过高温度都不利于氨氧化反应，进料方式会严重影响ＴＳ－１催化氨氧化反应：Ｈ２Ｏ２的连续产和氨的间歇进料方式可获得最佳的结果，在优化的反应条件     

由沸石纳米粒子自组装制备具有高催化活性中心和水热稳定的新型介孔分子筛材料

 人们合成了一系列介孔分子筛材料，并发现它们在催化、吸附与分离以及化学组装制备先进材料和分子器件等方面具有很大的潜在应用价值．但是，介孔分子筛材料相对于微孔沸石分子筛存在着两个致命弱点：较低的水热稳定性和较不活泼的催化活性中心．这两个弱点大大地影响了介孔分子筛在催化反应中的广泛应用．本文系统地综述了最近几年利用沸石纳米粒子自组装制备具有高催化活性中心和水热稳定的介孔分子筛材料的研究进展．这包括利用硅铝沸石纳米粒子自组装制备具有强酸性和水热稳定的新型介孔硅铝分子筛材料，利用钛硅沸石纳米粒子自组装制备具有高催化氧化活性中心和水热稳定的新型钛硅介孔分子筛材料，以及利用含有不同杂原子的沸石纳米粒子自组装制备一系列水热稳定的新型介孔分子筛催化材料．     

钛硅分子筛TS-1催化环己酮氨氧化制环己酮肟

对钛硅分子筛ＴＳ１催化环己酮氨氧化制环己酮肟的研究结果表明，提高催化剂的投料量、提高分子筛的钛硅比和降低Ｈ２Ｏ２的空速，有利于提高氨氧化反应的转化率和选择性．降低氨／酮比不利于氨氧化反应，适宜的氨／酮摩尔比应该在２０以上．适宜的氨氧化反应温度是８０℃左右，过低和过高的温度都不利于氨氧化反应．进料方式会严重影响ＴＳ１催化氨氧化反应：Ｈ２Ｏ２的连续进料和氨的间歇进料方式可获得最佳的结果．在优化的反应条件下，环己酮的转化率可达１００％，环己酮肟的选择性为９７％．给出了可能的ＴＳ１催化氨氧化反应机理，认为氨氧化反应是经历了氨催化氧化为羟胺的过程，肟是羟胺与环己酮通过非催化方式直接反应的结果．     

具有 MWW 结构钛硅分子筛的研究进展

 综述了具有 MWW 结构钛硅分子筛的制备方法、孔道和晶体结构的调变和修饰以及催化应用三个方面的研究进展. 与 TS-1 相比, 具有 MWW 结构钛硅分子筛的制备方法多种多样; 其孔道结构可塑性强, 通过采用层间剥离、柱撑以及分子水平硅烷化插硅扩孔技术, 可以增大和暴露孔道和外表面, 满足不同选择氧化反应的要求. 由于 MWW 结构钛硅分子筛拥有复杂而独特的孔道结构, 所以在小分子 (如直链烯烃等) 的环氧化反应, 和大分子 (环状烯烃, 二苯并噻吩等) 氧化反应中都表现出优异的催化性能. 此外, 该钛硅分子筛表现出与 TS-1 完全不同的溶剂效应, 用于烯丙基氯液相环氧化与酮类氨氧化反应主产物选择性更高.     

钛硅分子筛TS-1催化氯丙烯环氧化反应动力学研究

 摘要：研究了钛硅分子筛催化氯丙烯环氧化反应的条件及动力学行为．\r\n结果表明，以钛硅分子筛为催化剂，氯丙烯可被高选择性地氧化为环氧\r\n氯丙烷．环氧化反应速度与分子筛中骨架钛的含量及分子筛的用量呈正\r\n比关系，是一级反应．对于氧化剂H2O2，只有当c（H2O2）＜0．4mol／\r\nL时，环氧化反应为一级反应；而c（H2O2）＞1．0mol／L时，为零级反\r\n应．对于氯丙烯，随着其浓度的变化，环氧化反应的级数在1和0之间．\r\n然而，只有当氯丙烯浓度很高时，环氧化反应的级数才有明显的降低．\r\n根据实验结果和Eley－Rideal单分子吸附方程，提出了氯丙烯环氧化反\r\n应的动力学模型．\r\n关键词：钛硅分子筛，氯丙烯，过氧化氢，环氧化，环氧氯丙烷，反应\r\n动力学     

钛硅分子筛TS-1的合成、表征及催化性能

钛硅分子筛TS-1自Taramasso等［1］首次报道合成以来,由于其优异的选择氧化催化 性能及其催化的反应具有对环境污染轻,反应条件温和等优点而备受关注. 钛硅分子筛的制 备及应用研究是分子筛催化领域中的热点之一. 在经典的合成体系中,四丙基氢氧化铵(TPAO H)常被用作模板剂［2］,这是钛硅分子筛价格较为昂贵的主要原因之一. 国内外学者 都致力于廉价合成体系的开发,Müller等［3］报道了以四丙基溴化铵(TPABr)作模板 剂合成钛硅分子筛. 对于钛源和硅源,人们往往都采用水解趋势较为缓和的钛酯和硅酯,以达 到钛源和硅源的匹配;在合成过程中,要预先将钛酯加入到乙酰丙酮或异丙醇溶剂中进行稀释 ,并对胶液进行蒸醇处理［2,3］. 这使得钛硅分子筛的合成过程更加复杂,并提高了 其合成费用. 本文以钛酸四丁酯(TBOT)和四氯化钛混合原料作钛源,成功地合成出对丙烯环 氧化具有优异催化性能的钛硅分子筛TS-1,避免了上述的复杂步骤,并降低了钛硅分子筛的成本.     

无机钛硅原料合成TS-1催化氯丙烯环氧化反应

采用无机钛硅原料体系合成出了TS-1分子筛,并对TS-1分子筛催化氯丙烯环氧化反应进行了研究.在以甲醇为溶剂的体系中考察了反应时间、反应温度、催化剂用量、氯丙烯与双氧水的摩尔比对反应的影响,得到了无机钛硅原料体系合成的TS-1催化氯丙烯环氧化反应的最优条件:反应时间为60 min,反应温度为45℃,催化剂用量为22.5 g L-1,氯丙烯与双氧水的摩尔比n(AC):n(H2O2)=1.8,并对无机钛硅原料体系合成的TS-1进行了修饰改性,评价了其催化性能.     

等级孔介孔-微孔TS-1分子筛单晶的合成及催化氯丙烯环氧化性能

针对当前钛硅型分子筛存在的微孔孔道孔径限制导致的流通扩散性能差及催化效率低等关键瓶颈问题, 通过在微孔分子筛中构筑跨尺度贯通高物质传输性能的等级孔道结构, 对钛硅分子筛(TS-1)晶体内等级孔道结构的可控构筑及其催化环氧化进行了研究, 成功制备出具有富含介孔孔道的等级孔介孔-微孔TS-1分子筛单晶材料(HTS-1), 其在氯丙烯催化环氧化反应中表现出了优异的催化活性及稳定性能.     

多级孔钛硅分子筛的制备及应用进展

以钛硅分子筛(TS-1)为催化剂的选择性催化氧化工艺具有反应条件温和、产物选择性高及环境污染小等特点,促进了烃类催化氧化反应的绿色化发展.但常规TS-1分子筛狭窄的孔道限制了其在大分子催化氧化反应中的应用.多级孔TS-1分子筛为包含不同尺度的孔道结构的晶体沸石,兼具微孔分子筛晶体优异的水热稳定性和介孔材料优异的扩散传输性能,因此其受到国内外众多专家学者的广泛关注.多级孔TS-1分子筛的制备方法很多,主要有直接合成法和后处理法,其中直接合成法包括硬模板法、软模板法和自组装法,而后处理制备主要为碱处理法.我们在对多级孔TS-1分子筛制备方法进行归纳总结的基础上,探讨不同制备方法对分子筛中钛硅物种分布、孔道结构及催化烃类选择性氧化反应性能的影响.结合目前TS-1分子筛应用现状,对其未来发展进行展望.     

Thermal stability of Ti–MCM-41

Ti containing mesoporous MCM-41 materials have been synthesized through two methods: heating and non-heating [room temperature (RT)]. The synthesized materials have been characterized using X-ray diffraction, Fourier transform infrared, nitrogen sorption, and X-ray fluorescence methods and their thermal stabilities evaluated using thermogravimetric methods in inert atmosphere. The thermal stabilities have been analyzed based on the synthesis method, as well as on the amount of titanium in the MCM-41 materials. The thermal stability results suggest that uncalcined MCM-41 materials generally show higher mass loss than their calcined counterparts. Also, the RT-synthesized materials showed lower stability than the high-temperature synthesized samples for the uncalcined samples. It is also been found that MCM-41 materials show improved thermal stabilities as the amount of titanium is increased.     

Ti接枝MCM-41催化剂的结构设计及化学亲和选择性研究

 用二氯化钛茂作为活性物种的来源，利用Si－MCM－41催化剂表面羟基的反应性，得到了Ti接枝MCM－41催化剂的两种结构模型．结构表征结果表明，Ti接枝MCM－41催化剂不仅长程结构好，孔径分布均一，而且催化剂表面活性中心含量高．两种结构模型催化剂上芳烃羟化反应性能表明，Ti接枝MCM－41催化剂表面的亲水／憎水性可以在较宽的范围内调变，从而可实现控制芳烃羟化的化学亲和选择性．另外，研究结果还表明，Ti接枝MCM－41催化剂具有很好的活性稳定性．     

Catalytic oxidation of 4-tert-butyltoluene over Ti-MCM-41

The surface-grafted titanium MCM-41 materials were prepared by anchoring titanocene onto the inner walls of MCM-41. The materials were characterized by powder X-ray diffraction (XRD), N2 adsorption-desorption isotherm and diffuse reflectance UV-visible (UV-vis) spectroscopies. The catalytic properties of Ti-MCM-41 were tested in oxidation of 4-tert-butyltoluene with tert-butylhydroperoxide (TBHP) in liquid phase. MCM-41 with loading 4.8 mol% Ti gave the maximal conversions of 23.6% of 4-tert-butyltoluene with a complete selectivity to 4-tert-butylbenzaldehyde.     

介孔Ti-MCM-41在苯乙烯氧化反应中的催化性能

以MCM-41为骨架,以无机钛源Ti(SO4)2为原料成功合成了不同Ti含量的Ti-MCM-41样品,并考察了它们在H2O2氧化苯乙烯反应中的催化性能,研究了溶剂和Ti含量等因素对其催化性能的影响.结果表明,该反应主要产物为苯甲醛,苯乙烯转化率和苯甲醛收率均随骨架Ti含量增加而增加;催化剂中钛含量相近时,孔径的减小能够改善其催化性能;反应体系的合适溶剂应具有一定极性,如乙腈;降低溶剂极性和H2O2浓度可减少苯乙烯的进一步氧化,从而适当增加了苯乙醛和环氧苯乙烷选择性.     

Solid-Phase Immobilization of a New Epoxidation Catalyst

The heterogenization of a titanium(IV ) silsesquioxane complex in an MCM-41 molecular sieve , by tailoring the polarity of MCM-41, results in self-assembled materials (see the space-filling model on the right) that are active, truly heterogeneous, and recyclable catalysts for liquid-phase alkene epoxidation.     

Heterogenization of [Ti(η-C5HMe4)Cl3] on to MCM-41 and organomodified MCM-41 to form epoxidation catalyst

This paper describes the heterogenization of a tetramethylmonocyclopentadienyl titanium (IV) trichloride complex, [Ti(η⁵-C₅HMe₄)Cl₃] onto mesoporous MCM-41. Its immobilization has been performed via a straightforward grafting process of the organometallic precursor in the pores of an MCM-41 host material and by reaction with previously organomodified MCM-41 material with a hydroxyl triazine based compound. Applying all-silica MCM-41 hosts, stable and heterogeneous liquid-phase epoxidation catalysts are obtained. Powder X-ray diffraction and nitrogen adsorption-desorption analysis indicated that the structural integrity of the support has been preserved during the titanium complex immobilization. These materials have been also extensively characterized using diffuse reflectance UV-vis, ¹³C and ²⁸Si MAS NMR and FT-IR spectroscopy. With these techniques the strong adsorption of the intact catalytic complex within an all-silica MCM-41 host is demonstrated. These materials have been tested as catalyst for the epoxidation of aliphatic and aromatic alkenes with TBHP as oxidant exhibiting a significant selectivity toward the epoxide with negligible leaching of titanium species. The conversion values are moderated, being the olefin trend reactivity 1-octene > cyclohexene > styrene.     

One-step synthesis of a highly active, mesoporous, titanium-containing silica by using bifunctional templating

A highly active, three-dimensional, mesoporous titanosilica, TiTUD-1, with comparable properties to Ti-grafted mesoporous silica MCM-41, has been prepared in a one-step synthesis. A non-surfactant chemical, triethanolamine, was used as a template molecule. Triethanolamine easily forms complexes with titanium alkoxides, yielding titanatrane complexes, which together with free triethanolamine form meso-sized aggregates that template mesopores upon increasing the temperature of the synthesis mixture. Triethanolamine served as both mesopore template and ligand for the titanium complexes, which represent the majority of the catalytic-site precursors. The formation of the silica network and the titanium insertion were followed by a combination of diffuse reflectance UV/ Vis/NIR and FTIR spectroscopy. A titanium-rich phase was obtained on the mesopore surfaces during calcination, allowing for easy accessibility of the reactants to the catalytic sites. TiTUD-1 is about six times more active than framework-substituted Ti-MCM-41 and has similar activity to Ti-grafted MCM-41.     

无溶剂高度分散Ni/MCM-41催化剂的制备及其萘加氢性能

分别用机械研磨无溶剂法、添加柠檬酸无溶剂法制备了Ni/MCM-41催化剂,对所制催化剂进行了分析表征,探究其萘加氢反应性能并与常规浸渍法进行了对比。与常规浸渍法相比,机械研磨无溶剂法所制催化剂的物理性质相近,金属镍分散度和萘加氢性能略有提高;添加柠檬酸无溶剂法则显著提升了催化剂的分散度和萘加氢性能,金属镍分散度由6.9%大幅提高至67.9%,萘加氢性能提高了近1倍。通过红外光谱、紫外光谱和热重分析,提出了添加柠檬酸对无溶剂法制备催化剂性能的促进作用机制。     

Characterizations and Catalytic Properties of Transition Metal Ions Incorporated in Mesoporous Materials

Mesoporous materials typified by MCM-41 possess well-ordered mesoporous channels with controllable pore sizes from 2-30 nm, and are expected as desirable materials for catalysis.However, silicious mesoporous materials generally do not have sufficient intrinsic catalytic activities.Thus many studies have focused on introducing catalytically active sites. It is expected that different synthetic methods would result in different coordination structures of metal cations introduced in MCM-41, and thus different catalytic properties in catalytic reactions. The author's group has used two methods, i.e., direct hydrothermal synthesis (DHT) and template-ion exchange (TIE), for the syntheses of V-, Fe-, and Cr-MCM-41 and applied them as catalysts to selective oxidations of hydrocarbons. This paper highlights the characterizations of the coordination structures of these metal cations introduced into MCM-41 by the DHT and the TIE methods, and the structural-property relationships of these metal ion-containing MCM-41 materials in selective oxidation reactions.MCM-41 was prepared by hydrothermal synthesis using hexadecyltrimethylammonium bromide and sodium silicate as the sources of template and silicon, respectively. In the DHT method, metal cations were directly added into the synthesis gel before hydrothermal synthesis, while the exchanging of metal ions in ethanolic solutions with the template cations contained in the uncalcined MCM-41 was performed in the TIE method. XRD and N2-adsorption measurements showed that the mesoporous regularity was not destroyed with both synthetic methods for all the metal ion-containing MCM-41 with appropriate contents of metal cations.For V-MCM-41, the characterizations with mainly EXAFS suggested that V5+ cations were in tetrahedral coordination and mainly incorporated inside the framework of MCM-41 to substitute Si4+in the samples by the DHT method. Tetrahedrally coordinated Vanadyl species were also obtained by the TIE method, but the VO4 was dispersed on the wall surface of MCM-41. The V-MCM-41-DHT showed higher selectivity in the partial oxidations of C3H8 and i-C4H10 to alkenes and acrolein and methacrolein, but the V-MCM-41-TIE exhibited better catalytic activities in the partial oxidation of CH4 to HCHO and the oxidative dehydrogenation of C2H6.For Fe-MCM-41, EXAFS studies indicated that the DHT method also resulted in Fe3+ cations incorporated inside the framework of MCM-41 if iron content was lower than ca. 1 wt%. However,aggregated iron oxides with iron in octahedral coordination were mainly observed in the calcined Fe-MCM-41 by the TIE method. In the partial oxidation of CH4 to HCHO with O2 and the epoxidation of styrene with H2O2, the Fe-MCM-41 by the DHT method exhibits remarkably higher catalytic performances than that by the TIE method.Chromium could not be incorporated inside the framework of MCM-41 to substitute Si4+, and both synthetic methods led to surface chromate species. However, the DHT method resulted in only monochromate species on the wall surface of MCM-41 while polychromate species existed over the sample by the TIE method as indicated by the UV-Raman spectroscopic studies. The two types of Cr-MCM-41 exhibited distinctly different catalytic behaviors in the partial oxidation of CH4 with O2.The Cr-MCM-41-DHT was remarkably more selective towards HCHO formation.     

Fe/MCM-41 as a promising heterogeneous catalyst for ozonation of p-chlorobenzoic acid in aqueous solution

Mesoporous MCM-41 and Fe loaded MCM-41（Fe/MCM-41）,which were successfully prepared by a hydrothermal method and a dipping method respectively,were applied as heterogeneous catalysts for ozonation of p-chlorobenzoic acid（p-CBA） in aqueous solution.MCM-41 and Fe/MCM-41 were characterized by XRD,FT-IR and diffuse reflectance UV-vis（DR-UV-vis） techniques. The presence of either MCM-41 or Fe/MCM-41 improves p-CBA and total organic carbon（TOC） removal efficiency compared to ozonation alone.Under the experimental condition,TOC removal rate of Fe/MCM-41/O₃ process is over 63.5%at 60 min oxidation time,44.5%using MCM-41 as catalyst,only 37.7%with ozonation alone.The presence of tert-butanol（TBA） in the Fe/MCM-41/ O₃ process indicated that the oxidation mechanism of p-CBA occurs via OH in the liquid bulk.And Fe/MCM-41 is a promising catalyst.