Synthesis, Characterizations And Catalytic Properties Of Interlayer Expanded Zeolites

Many efforts have been devoted to the post-treatment of zeolitic lamellar precursors in order to widen the scope of their applications. Due to partial dissolution or even structural collapse caused inevitably by swelling at high temperature, zeolites prepared by delaminating or pillaring have significantly reduced long-range order. Compared to three-dimensional MWW structure, the interlayer expanded zeolite prepared by silylation with monomeric silicon source ((CH3)2SiCl2) preserved highly crystalline MWW intralayer structure with interlayer space enlarged by2.5A, showing a significantly improved catalytic activity in the liquid-phase epoxidation of alkenes with large molecular dimensions. Based on this concept, we propose to prepare interlayer more expanded MWW by silyation with dimeric silicon source [(CH3)2ClSi]2and [(CH3)2ClSi]2O. To overcome the spacial limitation of lamellar precursor, the reported mild swelling operated at room temperure was applied to reduce the damage to zeolitic structure. If Ti-MWW was used as the starting material, the process of swelling and silylation would cause severe titanium leaching, which is disadvantageous to its catalytic application. Therefore, we applied the liquid-solid isomorphous substitution reaction with H2TiF6to post-synthesize interlayer expanded Ti-MWW.The content of this dissertation includes the investigation of swelling degree, the type of silylation agents, the amount of silylation agents, different conditions of silylation and so on. By optimizing post-treatment conditions, interlayer expanded MWW zeolites with preserved crystallized intralayer structure were synthesized.The main issue of the subject is to synthesize interlayer expanded materials silylated with organosilanes in the form of mono-molecule, that is to say, not the condensed form. Besides, the calcination temperature is crucial from the perspective of decreasing the steric hindrance effect imposed on H2TiF6on the premise that the interlayer expanded structure is preserved.