Preparation And Investigation On Properties Of Hierarchical Porous Nano-molecular Sieves

There is great demand for energy, especially petroleum, since our country is in the high speed development. Effective use of petroleum resources is imperative in the age of soaring oil prices, therefore it is of great significance that studying the catalysts for petroleum processing. Molecular sieve catalysts are the important member of catalyst family, which are high active, high selective, easily operating, long service life. They bring enormous economic benefits and social effects as a result of that they can raise the utilization rate of raw materials, reduce the energy consumption, reduce the environmental pollution. Microporous molecular sieves possess strong acidity and good hydrothermal stability, which is obvious superior in the cracking of small and middle molecules. However, the finite size of microporous molecular sieves will restrict the entrance for heavy oil molecules, which makes the widespread applications in catalytic cracking reaction be restrained. Mesoporous materials exhibit better catalytic properties in the catalytic decomposition of petroleum, the transformation of fine chemicals and especially the catalytic reaction with macromolecules as participant because they possess larger pore size, high special surface area, high porosity and large pore volume. But mesoporous materials, in actual application, are incompetent at the reactions in which high hydrothermal stability and strong acid condition are requested, since they show lower crystallinity of pore wall, lower catalytic center activity and poorer hydrothermal stability than microporous materials. Thus, preparation of the hierarchical porous sieves is so imminent for extensive application in the field of catalytic cracking.The thesis put stress upon the preparation of micro-mesoporous materials and micro-macroporous materials as high effective catalysts for petroleum refining. We corroded nanocrystals forming mesopores or macropores by three different methods without destroying the microporous structures and prepared the hierarchical porous composite materials. Nano-laminar molecular sieve layers were prepared by the interaction of the structural directing agent and the cationic surfactant and put macromolecules in contact with the molecular sieves more adequately to raise the catalytic performance.Firstly, nano-ZSM-5 sieves with different sizes (40nm-500nm) and different Si/Al were prepared under hydrothermal system by adjusting the proportion of reactants. The crystal size and Si/Al of products can be regulated by changing the proportion of reactants and the amount of agents, which pave the way for the base corrosion. Three methods were adopted to treat ZSM-5 crystals and prepared micro-mesoporous materials and micro-macroporous materials. The products with different Si/Al were synthesized by controlling the reaction conductions and the samples possess great microporous structures and strong acidic catalytic centers. On the other hand, with the appearance of the mesopores and macropores. the special surface area is greatly increased, so that the contact of reactants with active centers is enhanced in the catalytic cracking reaction.Secondly, nano-TS-1 sieves with different sizes (40nm-200nm) and different Si/Ti were prepared under hydrothermal system by adjusting the proportion of reactants. The crystal size of products and the content of Ti in the sieve frameworks can be regulated by changing the proportion of reactants and the amount of agents. Hierarchical materials were prepared through treating calcined TS-1 crystals in lye solution by microwave method. The products possess great microporous structures and mesoporous or macroporous structures. At the same time, the special surface area is increased with 30% and the proportion of framework Ti is also increased. The results open the way to TS-1 as a good catalyst in phenol hydroxylation reaction.Thirdly, ordered nano-laminar microporous molecular sieves were prepared by the interaction of the structural directing agent and the cationic surfactant in a hydrothermal system. By the characteration of XRD, SEM, TEM, the samples synthesized by different conditions were investigated and the optimal reaction condition were obtained. Experimental data have demonstrated that the products have homogeneous flaky morphology with a dimension of several dozens of nanometers and possess high ordered microporous structures. The gaps among the layers are advantageous to the entrance of macromolecules, so that the contact of reactants with molecular sieves is enhanced in the catalytic reaction and the hierarchical materials can show excellent catalytic activity in the catalytic cracking reactions.