强化酸中心的介孔分子筛的合成和催化有机大分子反应

As known microporous zeolites have replaced the traditional, harmful and separation-difficult AlCl3 and liquid acid catalysts in many important processes of organic fine chemical reactions and acted as new, highly efficient, clean, separation-easy, regenerated and environment-friendly solid acid catalysts. On the other hand, these zeolite catalysts could not be used in the reactions of large organic molecules due to small pore of zeolite. The large pore, however, characteristic of mesoporous molecular sieves provides opportunities for the reactions of lare organic molecules. Because the conventional mesoporous molecular sieves have only weaker acid sites, their catalytic applications are limited. The mesoporous materials with enhanced acid centers synthesized here will overcome the shortcoming of lack of strong acid sites and be hopeful to play important catalytic role in the reactions of organic large molecules. The research work here utilized two-step method of hydrothermal crystallization. In the first step the precurdor containing the structure units of zeolite(named as zeolite structure precursor) with stronger acid sites was firstly synthesized, but complete crystalline structure of zeolite was not formed in this step. The second step of synthesis would transform the zeolite structure precursor into mesostructure in the presence of surfactant, generating the mesoporous molecular sieves with enhanced acid centers. Different from the micro-meoporous composite materials reported by other groups, the stronger acid sites of the mesoporous materials prepared here was located in the mesoporous wall not in the micropore or micro-cavity, to which larger reactant molecule was easily accessible to perform the catalytic reactions. In order to prepare zeolite structure precursor and know the synthesis condtions, the synthesis and reaction dynamics of the corresponding microporous molecular sieves, such as BETA, ZSM-5, ZSM-22, ZSM-23 and MCM-n zeolites, were firstly investigated. Moreover, to transform zeolite structure precursors into mesostructures the synthesis conditions and rule of conventional mesoprous molecular sieves were studied in detail, laying the foundation of the synthesis of the mesoporous materials with enhanced acid sites. The microporous and conventional mesoporous molecular sieves synthesized by us have also been used as supports or solid acid in the methane aromatization, the synthesis of eicosanic acid from a-eicosanol, the esterification of glycerol by oleic acid and the selective hydrogenation of oleic acid methylester. Based on the study on synthesis of all above, the new mesoporous materials were prepared under the templating function of surfactant by adjusting reaction composition and crystallization conditions, the purpose of increasing the acid strength of mesoporous molecular sieves being realized. In fact only BETA, ZSM-5 and MCM-22 were selected to prepare corresponding zeolite structure precursors which were transformed into mesoporous materials due to various limitation. Among the new mesoporous materials prepared one formed from the ZSM-5 structure precursor was micro-mesoporous composite or mixed materials, while ones generated from the BETA and MCM-22 structure precursors were pure mesophases. BETA mesophases included hexgonall(like MCM-41), cubic(like MCM-48) and lamellar structure.(like MCM-50)., designated as MB41, MB48 and MB50 respectively. For MCM-22 mesophase only hexagonal structure was synthesized and this mesostructured sample was named MM41. In the process of H-form transformation of the new mesoporous materials the treatment conditions were very important to protect mesostructures. The composition, structure and physicochemical properties of the new mesoporous materials were analyzed and characterized by XRD, SEM, TEM, MAS NMR, FTIR, TG-DTA, TPD, physical adsorption, elemental analysis, catalytic reaction, etc. and the results obtained verified that the new mesoporous materials possessed ordered pore structures, suitable Si/Al composition and thermal stability as well as acid centers

采用两步水热晶化方法合成具有强化的酸中心性质的介孔分子筛,通过改变分子筛模板剂和Щ跫?生长适宜的分子筛结构单元体,进而达到增强和调变合成的介孔分子筛酸性的作用.选择大分子的有机反应,如付氏烷基化,酰化和缩醛化反应等.研究制备的介孔分子筛的酸催灾?开发环境友好的大分子有机合成的新型固体酸介孔分子筛催化剂.