【作者】 张海娇；

【导师】 何鸣元； 吴鹏； 刘月明；

【作者基本信息】 华东师范大学 ， 物理化学， 2007， 博士

【摘要】 作为一种具有优异催化氧化性能且环境友好的钛硅催化材料，TS-1分子筛的合成及其作为烃类有机物选择氧化催化剂的成功应用，被认为是80年代沸石催化领域的一个里程碑。然而其昂贵的生产成本和苛刻的合成条件，严重制约了TS-1分子筛进一步的工业化发展。近二十多年来，科研工作者在降低TS-1分子筛的成本，提高其制备重复性和稳定性，减少或消除锐钛矿TiO₂的生成，以及拓展其应用范围等方面做了很多研究工作，取得了一些令人瞩目的研究成果。本论文在前人研究的基础上，以TS-1分子筛作为研究对象，从低成本高性能合成体系的开发着手，采用新的合成方法和工艺路线，对TS-1分子筛的合成、结构以及催化性能进行了系统研究，同时对介孔钛硅分子筛的合成也进行了探索性的研究，并以苯酚羟基化反应和烯烃的环氧化反应为探针反应，对上述材料的催化氧化性能进行了表征。这些工作对于推动这一高效且环境友好的催化新材料的工业化应用提供了一定的理论指导和实践意义。本论文主要包括以下内容：第一部分，从工业化生产角度出发，针对目前TS-1分子筛成本高的问题，以四丙基氢氧化铵（TPAOH）为模板剂，采用较低碱浓度水解成胶、较高模板剂浓度晶化的新工艺合成了低成本的TS-1分子筛，并优化了合成的条件。研究表明，在水解成胶碱浓度为8％左右、晶化模板剂浓度为20％左右时合成的TS-1分子筛，在催化苯酚羟基化反应中，苯酚的转化率达到20.6％。该法在保证TS-1分子筛高活性的基础上，模板剂TPAOH的用量明显降低，从而大大降低了其合成的成本。为了进一步提高TS-1分子筛的催化活性，对其进行了酸洗改性处理。结果表明，对未焙烧的TS-1分子筛原粉经过酸改性处理可以有效地选择性脱除TS-1分子筛中的非骨架Ti物种；然而如果对焙烧脱除模板剂后的样品再进行酸洗，由于形成的锐钛矿很稳定，所以不能将其有效除去。改性后的TS-1分子筛在苯酚羟化和正己烯氧化反应中均表现出很高的催化活性，Si／Ti为30和40时，较未改性的TS-1分子筛的催化活性提高了大约10％，而对于钛含量较高的Si／Ti为20的产品，采用此方法已经不能完全消除样品中的非骨架钛物种，因此，活性提高不大。第二部分，在热处理条件下，使Ti（SO₄）₂在多孔硅胶表面自发分散成具有类似于钛硅分子筛催化活性中心结构单元的Si-O-Ti键的SiO₂-TiO₂前驱体，并以TPAOH为模板剂水热合成了催化性能较好的TS-1分子筛。苯酚羟基化反应测试研究表明，前驱体的处理温度对最后产品的催化性能影响较大，处理温度以450℃为宜。第三部分，在无碱金属离子存在下，以发烟硅胶为硅源，以环状化合物六亚甲基亚胺（HMI）为模板剂，在添加少量“活性晶种”的条件下，研究廉价体系TS-1分子筛的合成。在合成中发现，晶种的选择和添加是该合成成功与否的关键因素。同时也考察了其它合成条件如：硅源、晶化时间、Si／B、H₂O／Si以及HMI／Si比对TS-1分子筛物化和催化性能的影响。研究表明，合成条件对TS-1分子筛的结晶度、晶粒尺寸、骨架钛含量和催化性能产生明显的影响。第四部分，采用干胶法分别以发烟硅胶和正硅酸乙酯为硅源，以TPAOH为模板剂，在考察影响合成因素的基础上，通过XRD、FT-IR、UV-Vis、TG／DTG、SEM等表征技术，对材料的物性进行了详细的表征。另外，考察了此体系模板剂用量以及前驱体制备过程中添加晶种对TS-1分子筛合成及催化性能的影响，结果发现适量晶种的添加可提高TS-1分子筛的结晶度，降低模板剂的用量。研究表明，与水热合成法相比，采用相同的硅源时，干胶法合成的TS-1由于其晶粒尺寸较小，从而在正己烯氧化反应中表现出更优异的催化氧化性能。第五部分，以具有六方结构的有序介孔碳材料（CMK-3）为硬模板，以正硅酸乙酯（TEOS）和钛酸正丁酯（TBOT）分别为硅源和钛源，采用干胶法，成功合成出具有沸石特征的介孔钛硅分子筛ZMTS，N₂吸附-脱附等温线表征和孔径分布曲线证明分子筛中包含介孔结构。研究表明，在烯烃环氧化反应中，该材料比介孔的Ti-MCM-41和微孔的TS-1分子筛显示了一定的优越性。通过上述工作，作者对于TS-1分子筛的合成机理、影响因素及其相关理论，有了进一步的了解；对于TS-1分子筛的合成方法有了更加全面的认识，从而为低成本TS-1分子筛的合成，提供了几条可行性的路径。更多还原

【Abstract】 As an environment benign catalyst, the successful synthesis of titanium silicalite molecular sieve TS-1 has been considered to be a milestone in zeolite catalysis in 1980^th because of its unique catalytic performance in oxidation reaction involving H₂O₂ as an oxidant. However, the application of TS-1 zeolite in the industry was hindered seriously by many defects of the classical synthesis such as the high cost of the raw material and the severe preparation conditions. In last two decades, many improvements have been made, which include decreasing the synthsis costs, enhancing the preparing repetition and stability, decreasing and removing anatase TiO₂ and expanding its industrial application.On the base of the previous achievements, the dissertation was focused on the relationship between the structure and catalytic performance of TS-1 zeolite. A series of new routes for synthesizing TS-1 zeolite were proposed in cheaper ways, such as using new template, cheaper raw materials. At the same time, the mesoporous titanosilicate was been tentatively investigated. The studies on the TS-1 zeolite are of academic and practical values concerning in the industrial application of TS-1 zeolite. The main contents of the dissertation are as follows:In the first part, a lower cost method for synthesizing of TS-1 zeolite was proposed using lower template concentration during gelation process and higher template concentration during crystallization process using tetrapropylammonium hydroxide （TPAOH） as the template. The synthesized TS-1 zeolite exhibited high catalytic activity （phenol conversion was 20.6%） in the hydroxylation of phenol with aqueous hydrogen peroxide in which template concentration was about 8% during gelation process and about 20.5% during crystallization process. Compared to the conventional synthesis method, the cost of TS-1 zeolite synthesized using this new method was lower. To improve the catalytic performance of TS-1 zeolite, a new modification was investigated. That is, as-synthesied TS-1 zeolite is pretreated before calcination with aqueous solution of HNO₃ under 120℃ by oil bath under vigorous stirring for 18 h. UV-Vis spectra verfied that the octahedral Ti species were selectivelyremoved following such a acid treatment procedure, which improves about 10% catalytic activity for TS-1 zeolite with Si/Ti of 30 and 40 in hydroxylation and 1-hexene oxidation than untreated sample. Nevertheless, extraframework Ti species, both octahedral and anatase-like, still remained to a certain level for the samples obtained from the precursors with Si/Ti of 20, because they contained too high a concentration of octahedral Ti. This indicates that once the anatase is formed within the materials upon the calcination, it withstands the acid extraction and is hardly removed.In the second part, the inorganic SiO₂-TiO₂ precursor having Si-O-Ti bonds similar to those present in the titanium silicalite-1 （TS-1） was prepared through spontaneous dispersion of Ti（SO₄）₂ on amorphous porous silica by thermal treatment. The precursor was used as the silica and titanium sources to synthesize TS-1 zeolite using TPAOH as the template under hydrothermal crystallization conditions. The catalytic activity of TS-1 zeolite for the hydroxylation of phenol with dilute hydrogen peroxide showed that the treatment temperature of the SiO₂-TiO₂ precursor obviously influenced the catalyst performance, and the suitable treatment temperature was about 450℃.In the third part, the titanosilicate of TS-1 zeolite is skillfully hydrothermally synthesized from an inorganic silica source and a cheaper structure-directing agent （SDA） of hexamethyleneimine （HMI） with the assistant of active seeds of TS-1 precursor in absence of alkali metal ions. The adding of a precursor gel containing the primary and secondary building units of MFI structure is the key step of the synthesis. The nature of precursor and the preparation conditions have great influence on the incorporation of titanium into the framework, and its effect in this system has also been investigated in detail. Other synthesis parameters such as silica sources, crystallization time, Si/B ratio, H₂O/Si ratio, HMI/Si ratio have been discussed. It is revealed that the crystallinity, crystal size, amount of Ti incorporated in framework and the catalytic properties of the samples were affected greatly by the synthesis conditions.In the fourth part, TS-1 zeolite has been synthesized successfully by a low-costdry gel conversion method from tetraethoxysilane （TEOS） and fumed silica sources, tetrabutylorthotitanate （TBOT） as titanium source and TPAOH as the template. The influence of various factors, such as crystallization time, silica sources, and gel compositions on the formation of TS-1 zeolite has been thoroughly investigated. Some physical and chemical properties and the structure of product were characterized by XRD, FT-IR, UV-Vis, TG/DTG, SEM and ICP-AES techniques. In addition, the adding of the seed and its nature has great influence on the synthesis of TS-1 zeolite. The amount of TPAOH has been greatly reduced in the DGC method by further adding the active seed. The results indicated that TS-1 zeolite synthesized by dry gel conversion technique exhibited higher activity than in the epoxidation of 1-hexene with H₂O₂ than hydrothermally synthesized one because of a much smaller crystal size when the same silica source was used.In the last part, a crystalline MFI type titanosilicate showing mesoporous characteristics has been synthesized by crystallizing the synthesis gel with the assistant of mesoporous carbon （CMK-3） using a dry gel conversion method. The resulting zeolitic mesoporous titanosilicate material, denoted as ZMTS, has been applied to the oxidation of alkenes with H₂O₂ as the oxidant, and its catalytic properties have been compared with that of conventional catalysts such as TS-1 and Ti-MCM-41. ZMTS proves to be superior in catalytic activity.From the above researches, the author have known more about TS-1 zeolite crystallization mechanisms, preparation method and their influencing factors, as well as the correlative theories, which decrease TS-1 synthsis costs and explore the new feasible pathways.更多还原