用无机钛源合成Ti-MCM-41的研究

采用无机络合剂稳定钛酰离子的方法,用多种无机钛源合成出了中孔Ti-MCM-41型分子筛,采用XRD,低温N2吸附和FT-IR等方法对合成的含钛分子筛进行了物性的表征。以苯乙烯的H2O2氧化作为模型反应,考察了合成的Ti-MCM-41分子筛的催化性能。结果表明,钛原子已进入分子筛骨架,用Ti(SO4)2和TiCl4为钛源合成的Ti-MCM-41分子筛在960cm^-1处存在较强的红外吸收,并对苯乙烯的H2O2氧化表现出较高的催化活性。     

Ti/SiO_2催化H_2O_2氧化苯甲醇制苯甲醛反应机理的理论研究

采用密度泛函理论B3LYP方法研究了非贵金属Ti催化H2O2氧化苯甲醇为苯甲醛的反应机理.考察了6条可能的反应途径,优化得到了各个途径的过渡态和中间体结构,计算了气相和液相中的反应势垒.结果表明,无催化剂时,H2O2氧化苯甲醇的反应途径具有非常高的反应势垒,反应不能进行;以Ti/SiO2为催化剂时,标题反应在乙腈溶液中的反应势垒为123.8kJ/mol,反应可在约353K下发生.结果还表明,标题反应在极性较大的溶剂中有较高的反应势垒,而在气相或者极性较小的溶剂中的反应势垒较低.     

Ti-MCM-41催化环己烯环氧化反应

采用水热法合成了Ti-MCM-41分子筛,XRD、FT-IR、ICP-AES以及DRS-UV-Vis表征结果表明几乎所有的Ti均进入具有MCM-41结构的分子筛骨架中。所合成的Ti-MCM-41对环己烯催化环氧化反应具有较优异的催化性能。溶剂种类、Ti-MCM-41催化剂用量、环己烯/H2O2比、反应温度等工艺条件对Ti-MCM-41催化性能的影响考察表明,在催化剂用量23.33g/L、环己烯浓度2.67mol/L、H2O2浓度0.67mol/L、10mL乙腈为溶剂、70℃反应180min条件下,环己烯单程转化率及H2O2有效利用率最高分别可达23.85%和95.04%。     

天然丝光沸石多步脱铝-钛化制备钛硅分子筛

以优选的天然丝光沸石为原料, 采用多步脱铝-钛化法合成钛硅分子筛, 利用 X 射线粉末衍射、紫外-可见光谱、电感耦合等离子体原子发射光谱、N2 吸附-脱附法以及氨程序升温脱附等手段对其进行了表征, 并考察了它在苯乙烯氧化反应中的催化性能. 结果表明, 该方法可成功地将 Ti 同晶取代到天然丝光沸石的骨架中, 其 Si/Ti 达到 79, 且能稳定地保持天然丝光沸石的结构. 该钛硅分子筛在以 H2O2 水溶液为氧化剂的苯乙烯氧化反应中表现有良好的催化活性, 是商业 TS-1 催化剂的 75%, 具有一定的应用前景.     

气固相法合成的Ti-ZSM-5催化剂上苯乙烯氧化反应的宏观动力学

 采用TiCl4气固相同晶取代法制得的Ti－ZSM－5作催化剂,对H2O2氧化苯乙烯反应的宏观动力学进行了研究,考察了催化剂、苯乙烯和H2O2用量及反应温度对苯乙烯氧化反应速率的影响．结果表明,催化剂Ti－ZSM－5和底物苯乙烯对苯乙烯氧化反应速率的贡献均为一级,而H2O2为1／2级;苯乙烯氧化反应的表观活化能Ea＝48．14kJ／mol．当以丙酮为溶剂,在n（PhCH∶CH2）／n（H2O2）＝7．91,催化剂用量为20g／L,反应温度为343K的条件下,反应360min时,苯乙醛选择性和H2O2利用率分别可达91．9％和88．6％．     

金属次卟啉二甲酯催化氧化苯乙烯制苯甲醛

将金属次卟啉二甲酯用作叔丁基过氧化氢（TBHP）氧化苯乙烯制苯甲醛的催化剂。 考察了催化剂、氧化剂用量、反应温度、时间、溶剂和不同金属次卟啉二甲酯[M(DPDME)]对苯乙烯转化率及苯甲醛选择性的影响,初步探索了反应机理。 结果表明,金属次卟啉二甲酯能够顺利地选择性催化氧化苯乙烯生成苯甲醛。 以0.002 mmol锰次卟啉二甲酯[ClMn(DPDME)]为催化剂,0.4 mmol TBHP为氧化剂,1 mmol苯乙烯为底物,5 mL CH3CN/H2O(体积比4∶1)为溶剂,反应温度75 ℃,常压反应20 h,苯乙烯的转化率达到98.3%,苯甲醛的选择性为92.7%。     

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．     

以硅胶和三氯化钛为原料合成Ti-MCM-41分子筛 Ⅲ. Ti-MCM-41分子筛的催化活性

 考察了以硅溶胶和TiCl3水溶液为原料合成的含钛中孔分子筛Ti－MCM－41对苯乙烯,α－甲基苯乙烯和环己烯氧化反应的催化性能．结果表明,对于CC双键位于端部的苯乙烯和α－甲基苯乙烯,发生的主要反应是CC双键的氧化断裂,而对于CC双键位于中间的环己烯,发生的主要反应是环氧化反应．     

固定床反应器中Ti-MWW催化H2O2分解

在固定床反应器中,H2O2与Ti-MWW分子筛的接触时间越长,其分解率越高.结果表明,分子筛骨架Ti和其拥有的酸性位是造成H2O2在分子筛上分解的主要原因,非骨架Ti对H2O2分解的影响弱于骨架Ti.H2O2的无效分解直接影响反应物的转化效率.了解H2O2无效分解的原因,有利于设计出高活性钛硅分子筛.同时在固定床中研究钛硅分子筛催化分解H2O2的反应有可能成为一种评价钛硅分子筛催化活性的新方法.     

改性VPO催化剂选择性催化氧化苯乙烯合成苯甲醛

以30%H2O2为氧化剂,金属助剂改性VPO为催化剂选择性氧化苯乙烯合成苯甲醛.研究了金属助剂、反应时间、温度、溶剂、氧化剂的量等对反应的影响.结果表明,镍助剂修饰的VPO能显著提高苯甲醛选择性,在Ni-VPO催化剂用量为5%,n(苯乙烯)∶n(H2O2)=1∶2,乙腈做溶剂50℃反应6 h的最优条件下,苯乙烯转化率为80.6%,苯甲醛选择性74%.XRD、FT-IR、SEM对催化剂进行表征并提出了可能的反应机理.     

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.     

Ti-MCM-41催化环氧化合物与胺的开环反应

以十六烷基三甲基溴化铵(CTAB)为模板剂, 钛酸异丙酯为钛源, 通过水热法合成了Ti-MCM-41分子筛催化剂并对其进行了表征, 结果表明, Ti-MCM-41催化剂具有介孔结构, 其孔径约2.0~4.0 nm. 考察了无溶剂条件下Ti-MCM-41对环氧化合物与胺的开环反应的催化性能. 结果表明, 当反应温度和压力分别为145 ℃和2.5 MPa时, Ti-MCM-41(5)对环氧乙烷(EO)与二甲胺(DMA)的反应具有良好的催化性能, 环氧乙烷的转化率和N,N-二甲基乙醇胺的选择性分别为98.37%和86.68%. 表征结果表明, 催化剂骨架中四配位结构的Ti使其表面具有丰富的路易斯酸性位, 该酸性位对环氧化合物与胺的开环反应具有重要促进作用. 此外, 还对Ti-MCM-41催化环氧乙烷与二甲胺开环反应的机理进行了初步探讨.     

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.     

Synthesis, structure, and acidic properties of MCM-41 functionalized with phosphate and titanium phosphate groups

Mesoporous molecular sieves Si-MCM-41 (purely siliceous) and Ti-MCM-41 (partly covered with a surface layer of TiO2) were functionalized with phosphate groups by treatment with POCl3 (denoted -MCM-41(P)and Ti-MCM-41(P), respectively). With the use of TEM, X-ray diffraction, and N2 adsorption, it was shown that the initial hexagonal structure, the high specific surface area, and porosity are retained in the functionalized materials but are not as good as in the starting materials. 1H MAS NMR and 31P MAS NMR revealed that the surface of Si-MCM-41(P) consists of silicon phosphate and pyrophosphate species. That of Ti-MCM-41(P) additionally contains titanium dihydro-, hydro-, and pyrophosphate species, the latter being predominant. TPD of adsorbed ammonia for Si-MCM-41(P) and Ti-MCM-41(P) showed that functionalization leads to the creation of moderate and strong acid sites. A combination of mesoporous structure with acidic properties makes the MCM-41 functionalized with phosphate groups promising for use as solid acid catalysts.     

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．     

Au/Ti-MCM-41(H)催化丙烯气相直接环氧化

采用纳米组装法制备了一系列不同Ti含量的具有微孔-介孔复合结构(hybrid)的钛硅分子筛Ti-MCM-41(H)载体,继而用沉积-沉淀法制得纳米金催化剂.通过粉末X射线衍射(XRD)、氮气等温吸附-脱附、傅里叶变换红外(FT-IR)光谱、紫外-可见漫反射(DRUV-Vis)光谱、透射电镜(TEM)及等离子体原子发射光谱法(ICP-AES)对催化剂进行了表征,并考察了纳米金催化剂在氢气/氧气共存条件下丙烯气相直接氧化制环氧丙烷反应中的催化性能.结果表明:合成的微孔-介孔复合结构的钛硅分子筛Ti-MCM-41(H)具有典型的MCM-41结构,Ti(IV)以高分散的形式存在于分子筛的骨架结构中.在常压、423K反应温度下,以Ti/Si摩尔比为1%的Ti-MCM-41(H)为载体制备纳米金催化剂表现出了最佳的催化性能,反应30min,丙烯的转化率达5.4%,环氧丙烷的选择性为74.2%,环氧丙烷的生成速率为73.1g·h-1·kg-1;反应330min后,丙烯的转化率为4.9%,环氧丙烷的选择性为67.3%.     

Highly efficient olefin oxidation catalysts based on regular nano-particles of titanium-containing mesoporous molecular sieves

Ti-MCM-41 and Ti-MCM-48 are successfully prepared by one step synthesis and post-synthesis at room temperature. The samples have been characterized by X-ray diffraction, SEM, TEM, nitrogen adsorption/desorption isotherms and UV-Vis spectroscopy. The results demonstrate the existence of an ordered mesoporous structure. The Ti species are grafted into the pure silica sieve frameworks without any evidence of the formation of non-skeleton anatase. The post-synthesis Ti-MCM-41 regular nano-particles display a higher conversion and selectivity as compared to that for both the post-synthesis Ti-MCM-48 and Ti-MCM-41 with ordinary particles, in the epoxidation of cis-cyclooctene with aqueous H(2)O(2) as an oxidant. The enhanced catalytic activity may be attributed to the existence of a higher number of isolated tetracoordinated Ti active sites and regular nano-particles, which are conducive to the affinity of the reactants with active sites.     

Facile synthesis of Ti-TUD-1 for catalytic oxidative desulfurization of model sulfur compounds

A facile synthesis route for Ti-TUD-1 at room temperature employing silatrane and titanium glycolate as Si and Ti sources (2?C8 mol%), respectively, over a triethanolamine template is proposed. XRD, N₂ adsorption?Cdesorption isotherms, and TEM analysis confirmed disordered mesoporous structures with high surface area (715?C824 m²/g). According to the UV?Cvisible spectroscopy of the calcined materials, titanium species of ca. 2.7 mol% Ti loading were present mostly in tetrahedral coordination for a sample prepared with 4 mol% Ti in the substrate mixture. Ti-TUD-1 showed catalytic activity in cyclohexene epoxidation, which depended on the amount of tetrahedrally coordinated Ti species. The hydrophilic nature of the surface of Ti-TUD-1 was confirmed by the effect of oxidant such that tert-butyl hydroperoxide (TBHP, 5?C6 M in decane) was superior to other oxidants in water (cyclohexene conversion: TBHP in decane 36.5% vs. TBHP in water 30.6%). Ti-TUD-1 was more active in oxidative desulfurization (ODS) reaction than Ti-MCM-41 at the same Ti loading; the former produced 4,6-dimethyldibenzothiophene (4,6-DMDBT) conversion near 100% after reacting for 15 min, whereas Ti-MCM-41 produced final conversion of 4,6-DMDBT of 89% after reacting for 180 min. ODS over Ti-TUD-1 was influenced both by electron density and steric hindrance in model sulfur compounds. Partially polymerized Ti sites seemed to also contribute to the reaction.     

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.