Structure And Properties Of Zeolites Modified By Chemical Treatments

Zeolites were widely used in catalytic reaction process, especially in the oil refining and petrochemical industry. For different catalytic reactions, specific type of zeolites with a special pore size and surface property was required. However, the zeolites prepared by direct synthesis by existing technology, was generally confined to a relatively narrow range in terms of Si/Al ratio, which led them unable to meet the needs of the different catalytic reaction process. Thus modifying the zeolites in different method to change the Si/Al ratio, acidity and pore structure of the zeolite, and hence improve catalytic property of the zeolites is much important project in catalysis investigation field.In this thesis, various zeolites were modified by loading metals, hydrothermal treatment, and chloro methane treatment, respectively, and their acidity, pore structure and catalytic properties were investigated after the treatments.A new dealumination method using chloro methane as treating agent was proposed in this thesis, by means which the controlled dealumination of zelites can be easily realized. This method has the following advantages:(1) The time required for dealumination of zelites is shorter than the other method generally applied in the industry; (2) The dealumination level of the zelites can be simply controlled by the treating time, the treating temperature, and the concentration of chloro methane in the treating gas mixture; (3) By this method, not only the surface property, but also the pore structure can be modified.The zeolites Y and FER were modified by several metals using impregnation method, and the catalytic property of the modified zeolites were studied using selective catalytic reduction of NOx by acetylene (C2H2-SCR) as a model reaction. The results indicated that the NOx removel selectitity can be effectively improved by loadding 2wt% of Zr, Y, La, or 1wt% of W, and the catalytic activity of the zeolite at 300℃can be simultaneously increased by the zeolite doping by Zr and W.