Synthesis,Characterization And Catalytic Performance Of Transition Metal Modified Heteroatomic Molecular Sieves

Molecular sieves are widely used in catalysis because of their large specific surface area,regular pore structure and uniform pore size.It is necessary for the development and renewal of catalysts to study molecular sieves with simple synthesis method and good catalytic performance.Considering the stability and catalytic effects of molecular sieves,pure silicon molecular sieves are synthesized by different routes.The structure of the as-synthesized sample is characterized by XRD,IR and UV-Vis.The valence and existing forms of transition metals are analyzed by XPS,EPR and TPR.The morphology and pore size of the products are also discussed by SEM and nitrogen adsorption and desorption.Finally,the catalytic performance of the as-synthesized catalyst was tested by the oxidation reactions of styrene and benzyl alcohol.The specific contents are as follows:?1?The layered silicate Mn-magadiite was synthesized by ion exchange method.Mn-magadiite as silicon source and manganese source synthesize Mn-Silicalite-1 by hydrothermal crystallization under neutral condition.A series of characterization results show that Mn has successfully entered the framework of Silicalite-1.The catalytic performance of Mn-Silicalite-1 was evaluated by the oxidation of styrene.The catalytic results show that the performance is excellent,and the low temperature is beneficial to the formation of oxidized styrene while the high temperature is beneficial to the formation of benzaldehyde.The selectivity of oxidized styrene decreases from 94.46%at 298K to 6.52%at 368K,and benzaldehyde increases from 5.54%at 298K to 93.48%at 368K.?2?V-Silicalite-1 with high vanadium content in the framework is successfully synthesized by controlling the alkalinity of the synthetic system.The characterization results confirme that V successfully repalce Si in the framework of molecular sieves.In the process of hydro-thermal synthesis,OH^-effectively promotes vanadium to enter the framework of Silicalite-1.V-Silicalite-1 showed well catalytic performance for selective oxidation of styrene at different reaction temperatures.At 298K,the conversion of styrene is 84.89%,and the selectivity of styrene oxidation is 91.04%.At 358K,the conversion of styrene is 97.47%,and the selectivity of benzaldehyde is 80.97%.?3?The highly ordered V-MCM-41 with high vanadium content is synthesized in the system with excessive NH₃?H₂O.A series of results show that vanadium species disperses well.Most vanadium enter the framework of MCM-41with states of tetravalence and pentavalence.In addition,other transition metals modified MCM-41 are successfully synthesized by the method of V-MCM-41.The catalytic performance of V-MCM-41 with different vanadium content is tested by the oxidation of benzyl alcohol.The results show that V-MCM-41 has good catalytic activity for the oxidation of benzyl alcohol.When the initial V/Si=0.10,the catalytic effect is the best.The conversion of benzyl alcohol is 74.83%,and the selectivity of benzaldehyde is 96.20%.