【作者】 高健；

【导师】 郭新闻；

【作者基本信息】 大连理工大学 ， 工业催化， 2010， 博士

【摘要】 气固相同晶取代法是合成具有MFI型孔道结构钛硅分子筛的一条简单易行、重复性好的合成路线；然而,传统气固相法合成钛硅分子筛的催化性能却相对于水热法较低。以先老化后晶化方法合成B-ZSM-5为母体制得的钛硅分子筛在一定程度上弥补这一不足,其催化性能接近于水热法合成的钛硅分子筛TS-1 (Titanium silicalite-1)。但其表现出较好催化性能的根本原因以及钛原子载入分子筛骨架过程和存在形式却并未进行详细探究。本论文以先老化后晶化方法合成的B-ZSM-5为母体,采用气固相同晶取代法合成Ti-ZSM-5。分别从母体合成和取代反应制备Ti-ZSM-5方面入手,对其催化性能提高的原因以及钛原子如何进入分子筛骨架及分布情况进行深入研究。论文内容如下：1.发现先老化后晶化可合成出由更小尺寸长方体颗粒团聚成的球状聚集体B-ZSM-5。长方体颗粒的尺寸大小直接决定以其B-ZSM-5为母体制得Ti-ZSM-5的催化活性和重复使用性的好坏。2.合成母体B-ZSM-5过程中,老化温度控制在333K-353K之间为最佳,此时母体B-ZSM-5中长方体颗粒尺寸最小并具有较大孔容及比表面积；以之为母体制得的Ti-ZSM-5在苯酚羟基化反应中的催化性能最为优异。3.制备母体过程中,有机醇的添加可明显改善母体聚集体的团聚状态；但对硼原子进入分子筛骨架却有较强抑制作用,导致骨架钛含量下降,Ti-ZSM-5催化性能降低；此外,添加丙三醇可制得表面光滑的十字形单晶且可有效缩短晶化时间至仅需4 h。4.采用TiCl4取代制备Ti-ZSM-5过程中,改变取代温度、热处理温度及取代时间等制备条件,考察其对Ti-ZSM-5催化性能的影响。发现该取代过程中有非锐钛矿的非骨架钛物种及骨架钛活性物种生成。低取代温度有利于不完全形式的骨架钛物种生成。经高温热处理后,这类钛物种可部分转变为四配位骨架钛物种,其他则转变为Ti-O-Ti形式的多聚态Ti物种；高取代温度下,以独立四配位形式存在的骨架钛物种则更易直接生成。基于上述结果,提出该合成方法中Ti原子进入分子筛骨架过程的推测。此外,还发现改变取代温度可有效控制钛物种在Ti-ZSM-5中的分布。低取代温度下,活性中心Ti4+分布在分子筛外表面居多；高取代温度下,活性中心Ti4+则多分布在分子筛孔道内。更多还原

【Abstract】 The gas-solid isomorphous substitution provides one operated easily and well repeated method to synthesize this titanium silicalite zeolite with the MFI structure. However, the catalytic activities of Ti-ZSM-5 synthesized from the gas-solid synthesis method are usually much lower than those of TS-1 obtained from hydrothermal synthesis. In these years, the improvement on the synthesis of the precursor B-ZSM-5 by adjusting the aging temperature can make up this deficiency. The catalytic activity of Ti-ZSM-5 using B-ZSM-5 as precursor, which is synthesized by aging treatment, and then crystallization, is similar to that of TS-1 obtained from the hydrothermal synthesis. But the reasons for showing such a good catalytic performance of Ti-ZSM-5, the incorporation process into the zeolite framework and existing forms of Ti species are still not clear.In this paper, Ti-ZSM-5 is synthesized by the gas-solid isomorphous substitution using B-ZSM-5 as precursor, which is prepared by aging treatment, and then crystallization. Proceeding with the precursor synthesis and the synthesis of Ti-ZSM-5 by the substitution reaction with TiCl4, the reasons for showing the high catalytic activity, the incorporation of Ti atoms into the zeolite framework and the main location of active sites are studied in detail.1. It is found that the precursors B-ZSM-5 synthesized by aging treatment, and then crystallization, consist of cuboid-like crystals with different sizes, which are agglomerated into different sizes of sphere-like particles. The good catalytic performance and recyclability of Ti-ZSM-5, using B-ZSM-5 as the precursor synthesized by aging treatment, and then crystallization, are mainly decided by the size of cuboid-like crystals.2. Adjusting the aging temperature, the optimized aging temperature should be controlled in the range of 333 K to 353 K. The obtained B-ZSM-5 has the smaller cuboid-like particles, the larger pore volume and surface area. Ti-ZSM-5 sample using this B-ZSM-5 as the precursor has a better catalytic performance for phenol hydroxylation.3. In the synthesis process of the precursors B-ZSM-5, adding the organic alcohol can modify the existing states of B-ZSM-5 that the sphere-like particles agglomerated by cuboid-like crystals with different sizes. But B atoms are strongly hindered to be incorporated into the zeolite framework; both the framework titanium content and catalytic performance of Ti-ZSM-5 become lower. In addition, adding glycerin, the crystal shape of B-ZSM-5 is also changed into the cross-like single crystals. The needed shortest aging crystallization time at 438 K is only 4 h.4. In the synthesis of Ti-ZSM-5 substituted with TiCl4, the effect of different substitution temperatures, times and heat treatment temperatures on the catalytic performance of Ti-ZSM-5 has been well investigated. It is found that there mainly exist isolated framework Ti4+ species and non-perfect framework titanium species. A low substitution temperature favors the formation of non-perfect framework titanium species, which can be converted into tetrahedrally coordinated Ti species and polymerized Ti species (Ti-O-Ti), after heat treatment. In contrast, at high substitution temperature, isolated tetrahedrally coordinated titanium species are easy to be obtained. Based on these results, a conjecture of the incorporation of Ti atoms into the lattice is proposed. In addition, it is also found that adjusting the substitution temperature can effectively control the location of Ti species in Ti-ZSM-5. At low substitution temperature, the active Ti (Ⅳ) species are mainly located on the external surface of Ti-ZSM-5; at high substitution temperature, the location of the active Ti (Ⅳ) species in Ti-ZSM-5 is inside the pore structures.更多还原