【作者】 徐俊青；

【导师】 李保山；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 博士

【摘要】 分子筛由于具有较高的比表面积，较大的孔容及均匀的孔径分布等特性，在基础科学研究和工业应用中受到了广泛关注。然而，纯硅分子筛作为催化剂使用时，其酸活性位较少，催化活性低，不能满足某些催化反应的需要。杂原子的引入可以有效增加分子筛的酸性位，这是提高分子筛催化活性最有效的方法之一。杂原子分子筛中骨架金属的含量与分子筛酸性位的数量有直接关系。因此，制备高金属含量、高规整度的金属杂原子分子筛对提高其催化活性具有重要的意义。根据分子筛孔径的大小，可将其分为微孔、介孔及大孔分子筛。微孔分子筛的晶体结构具有较好的稳定性，但由于孔径尺寸较小，在大分子催化反应中的应用受到限制；介孔分子筛虽然解决了孔径限制的问题，但其无定形的孔壁结构使得其水热稳定性较差，应用也受到极大的限制。目前，解决这一问题的主要方法是将微孔分子筛的结构单元引入到介孔分子筛的孔壁上，制备多级孔复合分子筛。多级孔复合分子筛的孔壁是由包含微孔分子筛单元的无定形介孔骨架构成的，制备具有全晶态骨架的介孔分子筛对解决这一问题提供了更有效的途径。本论文主要致力于高铁含量分子筛、多级孔复合分子筛、具有晶体结构介孔分子筛、高规整度杂原子介孔分子筛的制备研究，详细阐述了各种分子筛的合成条件和方法，并进一步对他们的结构特征、物理化学性能及催化活性进行了表征。论文通过水解控制及两步pH调节的方法，成功制备了高铁含量的微孔分子筛和介孔分子筛；通过两步晶化法将MFI结构单元引入到MCM-41介孔孔壁中，制备了微孔-介孔复合分子筛；以金属离子的配合物与长链表面活性剂分子的缔合物为模板剂，成功制备了具有晶体结构的介孔分子筛。通过X射线荧光光谱（XRF）、X射线衍射（XRD）、扫描电子显微镜（SEM）、高分辨透射电子显微镜（HR-TEM）、N₂吸附-脱附（N₂-sorption）、红外吸收光谱（FT-IR）、紫外可见分光光谱（UV-vis）、电子顺磁共振光谱（EPR）、X射线吸收精细结构（XAFS）、热重-差热（TG-DSC）、H2程序升温还原（H2-TPR）等分析测试手段对分子筛样品的组成、形貌、孔径结构、金属原子的配位状态、稳定性等进行了表征。并通过苯酚羟基化反应和渣油的加氢裂化反应对催化剂的催化活性进行了考察。论文的主要研究成果有：1)通过水解控制及两步pH调节的方法制备了骨架铁含量为10.5wt%（Si/Fe=8）的介孔分子筛Fe-MCM-41。测试结果表明，分子筛中Fe3+主要以四配位的方式存在于分子筛的硅氧骨架中，分子筛骨架在引入大量金属原子后依然保持了较好的介孔结构和较高的热稳定性。在以H₂O为反应介质，以H₂O₂为氧化剂的苯酚羟基化反应中，催化实验结果表明：苯酚的转化率随分子筛中骨架铁含量的增大而提高，当骨架中铁含量为10.5wt%时，分子筛具有较高的催化活性，在0.47g苯酚，0.03g催化剂，15ml去离子水，1.2ml H₂O₂，反应温度为70℃，反应时间为180min条件下，苯酚的转化率可达52wt%。2)通过水解控制的方法制备了骨架铁含量为7.2wt%微孔分子筛Fe-MFI。通过考察合成条件对其结晶度的影响，得到了最佳制备条件，并在该条件下制备了一系列不同铁含量的Fe-MFI。测试结果表明，制备的高铁含量Fe-MFI样品具有较好的晶体结构，随着铁含量的提高，样品的结晶度有所下降，晶粒尺寸也发生了改变。EPR和XAFS分析数据显示，Fe³⁺主要以四配位的方式存在于分子筛的硅氧骨架中。制备的高铁含量微孔分子筛Fe-MFI的颜色为白色，也说明Fe³⁺全部进入到分子筛的硅氧骨架中。3)通过双模板剂两步晶化的方法制备了双金属微孔-介孔复合结构的分子筛FeCo-MFI/MCM-41。测试结果表明，FeCo-MFI/MCM-41分子筛既具有MFI微孔结构，又具有MCM-41的介孔结构。XAFS数据显示，Fe³⁺和Co²⁺以四配位方式存在于分子筛的硅氧骨架中。渣油加氢裂化结果表明，FeCo-MFI/MCM-41催化剂对渣油的转化率和对汽油的选择性都高于单一孔结构、单一杂原子的微孔分子筛和介孔分子筛。4)以长链表面活性剂分子和金属配合物的络合物为模板剂，通过一步晶化法制备了具有晶体结构的介孔分子筛Cry-Ni-MCM-41。测试结果表明，样品既具有微孔分子筛的晶态骨架，同时又具有典型的介孔结构。扫描电镜图显示，材料可以形成较好的晶体结构，通过高分辨透射电镜可以观察到晶体上存在均一的介孔结构，且随着Ni含量的增大样品的结晶度也有所提高。样品中Ni的含量可达16wt%。样品经NaOH溶液处理之后依然保持了完整的晶体结构，说明该材料具有较好的碱稳定性。5)通过两步法制备了高规整度的介孔分子筛Fe-MCM-41。以K₃Fe（CN）₆为铁源，通过后处理法制备了具有极高规整度的Fe-MCM-41介孔分子筛。HR-TEM和N₂吸脱附表征结果表明，在将Fe³⁺引入到分子筛骨架上之后，其规整度和孔道结构没有被破坏。在FT-IR和XAFS测试结果基础上，提出了高规整度介孔分子筛Fe-MCM-41形成机理，Fe（CN）³⁺₆首先与模板剂分子发生相互作用，之后，Fe³⁺在焙烧过程中进入到分子筛骨架上。苯酚羟基化反应结果证明，制备的含骨架铁的Fe-MCM-41其催化活性要高于氧化铁负载的介孔分子筛Fe/MCM-41，且随着Fe-MCM-41中铁含量从0.2wt%增大到0.7wt%，苯酚的转化率也从21.7%提高到38.9%。6)在测试结果的基础上，探讨了各类分子筛材料的形成机理。更多还原

【Abstract】 Molecular sieve materials have received considerable attentions in basic scientificresearch and industrial applications on account of their acidity and structure features.However, their weak surface acidity restricts the applications of pure silica zeolite;on the other hand, the pore-restrictions of microporous zeolite and lowerhydrothermal stability of mesoporous molecular sieves also hindered theirapplications.The incorporation of foreign atoms into the silica framework was found to be aneffective strategy to promote the surface activity. The acidities of molecular sieveswere related to the metal content in the framework; more metal atoms in theframework could be conducive to the generation of more catalytically. Thus,metal-rich incorporation molecular sieves are desirable. A number of papers dealwith the synthesis of composite materials, which should combine the advantages ofmicroporous zeolite and mesoporous molecular sieves.In the present studies, we show that high content of iron can successfully beincorporation into the microporous zeolite and mesoporous molecular sievesframework using a simple hydrothermal method, avoiding co-precipitation of iron oxides during the synthesis. Micro-mesoporous composites were prepared using adual templating method through a process of two-step crystallization. Mesoporoussilica with crystalline zeolitic framework was synthesized through one-pot process.The obtained products were characterized by using X-ray fluorescence spectroscopy（XRF）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high-powertransmission electron microscopy （HR-TEM）, N2adsorption/desorption（N₂-sorption）, infrared absorption spectroscopy （FT-IR）, UV-visible absorptionspectroscopy （UV-vis）, electron paramagnetic resonance spectroscopy （EPR）, X-rayabsorption fine structure （XAFS）, thermogravimetric-differential scanningcalorimetry （TG-DSC）, H₂temperature-programmed desorption （H₂-TPR）. And thecatalytic activities were investigated through the hydroxylation of phenol and residuehydrocracking reaction. The main research results are as following:1) The mesoporous ferrisilicates （MFS） with high iron content were synthesizedby pH-modification method and the iron content could be up to10.5wt%（Si/Fe=8）.The pH was kept less than2at pre-hydrothermal synthesis step and was adjusted to11during hydrothermal step. The characterized results suggested that the MFSmaterials were ordered2D-hexagonal mesophase of MCM-41, and the iron ionswere tetrahedral coordinated in the silica framework. This material could efficientlycatalyze the hydroxylation of phenol in water medium using H₂O₂as an oxidant, andthe phenol conversion could be up to52wt%under the optimal experimentalconditions.2) A series of Fe-MFIs with a high content of iron were synthesized using TBAB as the structure directing agent. The optimum limit of iron incorporation in theframework was7.2wt%. Characterization results showed the Fe³⁺was tetrahedralcoordination in the silica framework. The crystallinity of Fe-MFI decreased with theiron content increases; the crystalline sizes also change with the iron contentincreases.3) The MFI/MCM-41composites with bimetallic Fe and Co were prepared usinga templating method through a process of two-step crystallization. Characterizationresults showed that two kinds of stable MFI/MCM-41composites can be synthesizedduring the course of recrystallization. The iron and cobalt were incorporated into thesilicon framework according to the characterization data. The composites presentedexcellent activities in hydrocracking of residual oil, which were superior to the purematerials of silicate-1/MCM-41.4) Mesoporous molecular sieves Cry-Ni-MCM-41with crystalline zeoliticframework was synthesized using one pot process. The obtained products possesseda good crystal particle with uniform mesoporous channel. The alkali stability of thesample wss much higher than the amorphous pore walls of mesoporous molecularsieves.5) A method of incorporating iron onto the mesoporous silica network usingpotassium ferricyanide （K₃Fe（CN）₆） as the iron source was established. TheFe（CN）₆³+ions interact with the template and attached onto the silica network afterthe as-synthesized sample calcined at823K. FT-IR spectroscopy provided a clearevidence for the interaction between cyanide ligands and template. XANES spectroscopic displayed that the Fe³⁺changed from octahedral to tetrahedralcoordinated during thermal treatment. XRD and HRTEM results indicated that theiron ions incorporated onto the silica network without destroying the lattice structureof the parent MCM-41. The synthesized material exhibited a good activity for phenolhydroxylation.6) According to the results of the characterizations, the formation mechanisticof the samples was described.更多还原