The Study On The Synthesis And Catalytic Properties Of Beta Zeolites With Large Crystal Size

In this dissertation,the hydrothermal synthesis and metal modification of Beta zeolites with large crystal size have been studied,and the physical and chemical properties were characterized.First,hydrothermal synthesis of Beta zeolites by different templating agents?tetraethylammonium hydroxide?TEAOH?and tetraethylammonium bromide?TEABr??were carried to screen suitable conditions for the preparation of large zeolite crystals,respectively.The factors,including the source of alkali,the amount of potassium the ratio of silicon to aluminum?SiO₂/Al₂O₃?,and the crystallization temperature were investigated.The results show that Beta zeolite with a larger size?0.6?m?1.0?m?is obtained by changing the alkali source from Na OH to KOH.For the synthesis with TEABr as template,the suitable composition of alumino-silicate gels for zeolite is K⁺/at 140?was required to obtain 0.8?m?1.2?m Beta zeolite aggregates.For the preparation with TEAOH as template,the suitable composition of alumino-silicate gels crystallization at 140?was required to obtain highly crystallinity Beta zeolite as large as 1?m.The use of TEAOH template results in large Beta zeolites?>1?m crystal size?,which show better stability and catalytic activity in the esterification reaction than those of Beta zeolites synthesized using the TEABr as template.Next,the modification of Beta zeolites by copper ion was studied.The copper species was introduced into Beta zeolite by the in-situ hydrothermal synthesis method and the impregnation method,respectively.Comparing to the synthesis of pure zeolite,the product yield increases from 70%to 85%and the zeolite size increases from 0.5?m to 1.0?m of Beta zeolite crystal,as well as the acid amount,after the inducing copper via the in-situ hydrothermal synthesis method.In comparison with the use of Cu?NO₃?₂or CuSO₄ as raw copper sources,the use of CuCl₂ leads to the highest product yield?85%?and the highest content of copper atoms?2.2%?,and the acid amount of Beta zeolite modified by the impregnation method decreases with the use of Cu?NO₃?₂ or CuSO₄ as raw copper source,respepctively.When CuCl₂ is used,the acid amount of the modified Beta zeolite increases.In comparison with pure Beta zeolites,Beta zeolites modified by copper ion showed a lower catalytic activity in the esterification of levulinic acid.