Ti-MCM-41催化剂的表面性质及介质极性对

用不同的铝源改性Ti MCM 41催化剂 ,得到了具有长程有序结构、n(Si) /n(Ti) =2 5的不同Si/Al比的改性Ti MCM 41.通过研究芳烃羟化反应随催化剂表面性质的变化规律发现 ,调变催化剂的表面性质 ,可控制反应物苯及目的产物苯酚与Al Ti MCM 41催化活性中心接近的程度 ,从而可实现对芳烃羟化反应化学选择性的控制 .介质极性对芳烃的化学亲和选择性也有影响 ,只有富含供电子氧原子且其极性大于苯的介质才有利于芳烃的羟化反应     

单金属双中心Ti-MCM-41分子筛催化剂的光催化性能

 制备了单金属双中心Ti－MCM－41分子筛催化剂，通过XRD、低温N2吸附－脱附、XPS及原子吸收光谱等对催化剂进行了表征．结果表明，单金属双中心Ti－MCM－41分子筛催化剂具有良好的长程有序结构和孔结构，其比表面积大于1000m2／g，孔径分布窄，最可几孔径为2．7nm；Ti的电子结合能为458．6eV，介于骨架Ti（选择性氧化活性中心）和非骨架Ti（光催化活性中心）之间．以H2O2和·OH的生成量为基准，考察了Ti－MCM－41对苯羟化反应的催化性能随光照时间、催化剂用量、加水量、反应温度和空气流速等条件的变化，得出了光催化反应的最佳条件．在无外加氧化剂的情况下，单金属双中心Ti－MCM－41上苯的转化率为0．2％，表明其确实具有一定的光催化性能，可实现光催化－选择性氧化的反应－反应耦合．与骨架取代Ti－MCM－41和MCM－41负载TiO2催化剂相比，单金属双中心Ti－MCM－41的催化活性最高．这主要是由于它既具有光催化活性中心，又具有选择性氧化活性中心．     

Ti—MCM—41的结构特征与芳烃羟化反应的化学亲和选择性

以不同硅源合成了Si/Ti比不同的Si-Ti－MCM－41,并在引入Ti的同时引入Al,合成了Si/Al比不同的Si-Ti-Al-MCM-41。XRD、TEM、低温N2吸附的表征结果说明,Ti-MCM-41具有长程有序一维孔道,且比表面积较高,FT－IR光谱表征说明,Ti对骨架Si的取代使MCM－41表面出现缺陷羟基。Al的引入有利于Ti-MCM-41有序结构的形成。且可调变Ti-MCM-41的表面性质。Ti-MCM-41在不同极性芳烃化合物的羟化过程中表现出化学亲和选择性,且调变Ti-MCM-41的表面性质可实现对化学亲和选择性的控制。     

Ti—MCM—41催化剂的表面性质及介质极性对苯羟化合物化学选择性的影响

用不同的铝源改性Ti-MCM-41催化剂，得到了具有长程有序结构、n(Si)/n(Ti)=25的不同Si/Al比的改性Ti-MCM-41。通过研究芳烃羟化反应随催化剂表面性质的变化规律发现，调节催化剂的表面性质，可控制反应物苯及目的产物苯酚与Al-Ti-MCM-41催化活性中心接近的程度，从而可实现对芳烃羟化反应化学选择性的控制。介质极性对芳烃的化学亲和选择性也有影响。只有富含供水电子氧原子且极性大于苯的介质才有利于芳烃的羟化反应。     

Ti接枝KIT-1对苯羟化反应的化学亲和选择性及化学稳定性研究

以合成后表面接枝的方式制备了长程结构和孔结构均较好的Ti接枝KIT-1催化 剂,将其用于苯羟化反应,研究了Ti接枝KIT-1催化剂的苯羟化学性能和稳定性, 结果发现：Ti接枝KIT-1催化剂对苯羟化过程表现出化学亲和选择性,即使在过氧 化氢过量的条件下,也可避免深度氧化的进行;Ti接枝KIT-1催化剂在苯羟化过程 中表现出较好的结构稳定性。     

以硅胶和三氯化钛为原料合成Ti-MCM-41分子筛 Ⅱ. Ti-MCM-41分子筛的表征

 利用N2吸附,TG－DTA,FT－IR,UV－Vis和UV－Raman光谱等技术对以硅溶胶和TiCl3水溶液为原料合成的中孔Ti－MCM－41分子筛的孔结构和钛的配位状态进行了详细的表征．N2吸附等温线表明,Ti－MCM－41分子筛的孔径比纯硅MCM－41分子筛小,钛的加入使分子筛的单胞体积大大增加,比表面积和孔壁厚度也显著增大．TG－DTA结果表明,Ti－MCM－41分子筛中存在着两种不同的模板剂键合位．FT－IR,UV－Vis及UV－Raman光谱表明,Ti原子存在于分子筛骨架中且以四面体方式配位,没有结晶状态的TiO2形成．     

BO3－3／Mo－MCM－41的制备及其对2－甲氧基萘乙酰化反应的催化性能

 制备了Mo－MCM－41中孔分子筛，并将BO3－3引入到分子筛中制得BO3－3／Mo－MCM－41催化剂．采用XRD，FT－IR，ESR，BET和NH3－TPD对分子筛催化剂的结构及酸强度进行了表征．结果表明，Mo－MCM－41和BO3－3／Mo－MCM－41具有中孔分子筛的特征，有良好的长程有序 性和结晶度；但Mo并未进入分子筛骨架内部而是在分子筛表面以MoO2的形式存在；BO3－3附着于Mo－MCM－41分子筛上形成强酸中心．将BO3－3／Mo－MCM－41用于催化2－甲氧基萘乙酰化反应，考察了催化剂用量、Si／Mo比及BO3－3的引入方式对该反应性能的影响，发现BO3－3／Mo－MCM－41对2－甲氧基萘乙酰化反应具有良好的催化性能．     

结晶硅酸盐/硅铝酸盐介孔材料MCM-41的结构特征与应用性能

由于独特的结构特征及表面性质，MCM－41一问世即受到广泛的关注。但由于结构稳定性不足等原因，近年来关于MCM－41的研究骤然降温。本文从“扬长克短”和“扬长避短”的角度出发，对MCM－41作为催化剂、载体材料、吸附材料及在无机－有机复合材料中的潜在应用进行了综述。     

Mn（salen）／Al－MCM－41催化剂的制备及其对苯乙烯环氧化反应的催化性能

 报道了一种用微波固相法制备Mn（salen）／Al－MCM－41催化剂的新方法，并与常规制备方法进行了比较．FT－IR表征结果表明，微波固相方法和常规方法均能成功地将Mn（salen）配合物固载于Al－MCM－41介孔分子筛上，且微波固相法制备的Mn（salen）／Al－MCM－41催化剂在1448cm－1处具有更强的吸收带．比较了不同方法制备的催化剂在苯乙烯环氧化反应中的催化性能，发现微波固相法制备的Mn（salen）／Al－MCM－41催化剂具有较高的催化活性和环氧化物选择性．此外，催化剂的性能与制备过程中微波辐射的时间有关．考察了反应时间和反应温度对微波固相法制备的催化剂性能的影响规律，随着反应时间的延长和反应温度的升高，苯乙烯环氧化物的选择性逐渐下降．     

Co改性Mo/MCM-22催化剂上甲烷无氧芳构化及积炭研究

 研究了Co的添加对Mo／MCM－22催化剂甲烷无氧芳构化反应性能的影响．发现用共浸渍法制备的Co／Mo摩尔比为0．2的催化剂具有较高的活性,而先浸渍Mo后浸渍Co的催化剂具有较好的稳定性．XRD实验表明,Co及Mo的氧化物均高度分散在分子筛表面,其担载降低了分子筛的衍射强度．不同接触时间下催化剂的反应结果表明,接触时间长,积炭选择性随接触时间增加而迅速增加;接触时间短,积炭选择性随接触时间增加而减少．积炭催化剂的TG研究表明,催化剂上的积炭主要有两种形式．低温积炭随反应时间增加而迅速增多,高温积炭的变化则较为缓慢．低温积炭可能是导致催化剂活化和失活的主要原因．高温积炭可能是一种大分子量的碳氢物种,位于MCM－22分子筛的“超笼”中,表明MCM－22有较大的容积炭能力．     

过渡金属改性MCM-41的结构及对苯催化氧化的研究

制备了Ti,Fe,Cr,Ni改性的MCM-41,采用XRD、低温N₂吸附及TPD手段研究了改性MCM-41的结构特征和表面性质.过渡金属可同品取代骨架Si,同品取代的能力与过渡金属离子半径有关.过渡金属改性MCM-41均具有较好的长程有序结构、均一的孔径分布和较高的比表面积.引入不同的过渡金属可以改变MCM-41表面酸性和亲水/憎水性.考察了改性MCM-41对苯氧化的催化性能.     

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.     

Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Br?nsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.     

高负载钛MCM-41催化剂的制备与表征

钛硅分子筛在各种有机反应中具有独特的催化氧化性能，采用廉价双氧水作氧化剂，产物选择性高，反应条件温和，不会发生深度氧化，且整个催化反应无污染排放，所以越来越受到人们的重视．然而TS—1以及其它微孔分子筛的孔径较小，难以使大分子的有机化合物进人孔道中进行催化反应，因此合成较高水热稳定性及高氧化活性的介孔钛硅分子筛仍是催化研究的重要课题。     

Grafting Titanocene on Hydrophilic Amorphous Silica:Synthesis of an Effective Catalyst for Olefin Epoxidation

Ti/silica catalysts were prepared by grafting titanocene dichloride (Cp₂TiCl₂) on hydrophilic amorphous silica with different Ti contents under mild conditions. The results of FT-IR, UV-vis and XPS analyses proved that titanium was successfully grafted in the form of Ti(IV) on amorphous silica and the maximum content of Ti grafted was found to be ca. 3 wt.%. When cyclohexene epoxidation with TBHP was carried out over these synthesized catalysts, both the activity and the selectivity to epoxide increased with the amount of Ti grafted. This amorphous Ti/silica catalyst showed a higher activity and a higher selectivity to epoxide than Ti-containing molecular sieves, Ti-MCM-41 and Ti-beta, with nearly the same Ti content. With Ti content larger than 3 wt.%, however, anatase phase (TiO₂) was formed to give a lower activity and selectivity to epoxide.     

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.     

新戊基钛在MCM-41表面的接枝反应及产物性质

采用原位红外光谱法在真空系统中考察了MCM-41分子筛表面与四新戊基钛Ti(CH2CMe3)4的反应,发现这个反应可在室温下定量进行,得到表面新戊基钛(≡Si－O)2Ti(CH2CMe3)2. 这种表面新戊基钛很容易与CH3OH、H2O和O2进一步发生反应分别得到(≡Si－O)2Ti(OCH3)2、(≡Si－O)2Ti(OH)2和(≡Si－O)2Ti(OCH2CMe3)2等表面化合物.在氧气中焙烧由(≡Si－O)2Ti(CH2CMe3)2水解所得的(≡Si－O)2Ti(OH)2可制得表面含钛MCM-41介孔分子筛（Ti-MCM-41）.元素分析、低温N2吸附-脱附、紫外可见漫反射光谱、X射线粉末衍射和FTIR等表征结果表明,接枝反应和后续的处理不破坏分子筛的介孔结构; Ti-MCM-41的比表面积和孔直径较MCM-41略有降低; Ti原子在Ti-MCM-41表面以TiO4四面体配位状态分散,并对乙烯氧化有较明显的光催化活性.论文还通过对Ti-MCM-41与水热合成骨架含钛[Ti]-MCM-41结构和光催化活性的比较,对分子筛类材料光催化作用机制进行了分析探讨.     

Characterization of methylated nanoscale MCM-41 material

In this study, nanoscale MCM-41 molecular sieve was prepared under a basic condition by a hydrothermal method using cetyltrimethylammonium bromide as a template and tetraethyl orthosilicate as a silica source. Methylated nanoscale MCM-41 molecular sieve was prepared from the nanoscale MCM-41 by post-synthesis method using trimethylchlorosilane (TMCS) as coupling agent. The product was characterized by means of element analysis, powder X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, low-temperature nitrogen adsorption-desorption technique at 77 K, scanning electron microscopic (SEM), thermogravimetry-differential thermal analysis (TG-DTA). Powder XRD showed that the framework of the molecular sieve was well retained and the degree of ordering of the methylated MCM-41 decreases. IR spectra and the low-temperature nitrogen adsorption-desorption technique suggested that methyl was successfully grafted to the inner surface of the methylated MCM-41 and the mesoporous channels of the methylated MCM-41 were still maintained. Scanning electron microscopic results showed that the average size of the methylated MCM-41 prepared was 112 nm. Differential thermal analysis showed that the prepared material has preferable thermal stability and the methylated MCM-41 can be stable at 903 °C.     

Supported dichlorobis(3-hydroxi-2-methyl-4-pyrone)Ti(IV) catalysts: Evaluation on ethylene polymerization

Dichlorobis(3-hydroxi-2-methyl-4-pyrone)Ti(IV) complex was grafted on different inorganic supports, namely different kinds of SiO₂, MAO-modified silica, MCM-41, Al₂O₃, ZrO₂ and MgO. The resulting supported catalysts were shown to be active in ethylene polymerization using methylaluminoxane (MAO) as cocatalyst, most of them being even more active that the homogeneous complex. The highest catalyst activities were observed for the Ti complex supported on SiO₂ 948 activated at 450 °C, MCM-41 and Al₂O₃.