Pore Expansion And Crystal Transformation Of Microporous Zeolites

The isomerization of β-pinene is an important reaction to synthesize spices,such as camphene,limonene,terpinene,and terpinolene,among which terpinene and terpinolene are difficultly obtained.Herein,MOR zeolite modification by both inorganic base(NaOH)and organic base(TEAOH)was conducted,which showed high catalytic activity for the isomerization of β-pinene to high-added value spices of terpinene and terpinolene.Different from the zeolite catalyst modified by solely inorganic base or organic base,both high conversion of β-pinene and high selectivity for terpinene and terpinolene could be achieved over dual-modified zeolite catalyst.The roles of inorganic base and organic base had been revealed based on the various characterizations and catalytic reaction results,and possible reaction mechanism was described.The modification by inorganic base was mainly to introduce additional mesopores into the MOR zeolite,which had an important influence on the conversion of β-pinene through accelerating the diffusion and mass transfer of various bulky organic molecules in the reaction system.The modification by organic base was mainly to tune the Br(?)nsted/Lewis acid property,which had an important impact on the selectivity of products.In contrast,the zeolite modification by solely inorganic base mainly showed Lewis acidity,which led to camphene and limonene as the main products;the zeolite modification by solely organic base mainly showed Br(?)nsted acidity,which produced camphene,terpinene and terpinolene as the main products.The dual-modified zeolite catalyst by inorganic/organic bases turned the ratio of Br(?)nsted/Lewis acidity to 6.59,which promoted the selectivity of terpinene and terpinolene to 70.9 %.The resulting catalyst showed high reaction-recycling stability,which maintained the catalytic performance up to 10 recycles.SSZ-13 zeolite is widely used in the process of industrial production.The traditional synthesis method requires N,N,N-trimethyl-1-adamantylammonium hydroxide as a template,and the high synthesis cost limits the application of SSZ-13 zeolite.In this paper,SSZ-13 zeolite was synthesized by rotating hydrothermal method using the complex of metal and organic amine as template.During the crystallization process of molecular sieve,we observed the phenomenon of crystal transformation from FAU to CHA crystal phase.The research has successfully synthesized SSZ-13 zeolite by crystal transformation method from commercial Na-Y zeolite,and expanded the template into complexes of different metals with tetraethylenepentamine(TEPA)or diethylenetriamine(DEPA).The optimal synthesis conditions of SSZ-13 zeolite and the influence of various conditions on the crystal phase transition during the synthesis process were obtained by adjusting the conditions,such as the ratio of silicon to aluminum,the pH of the gel and the template agent,and the in-situ method of crystal transformation with Co-DEPA as the template agent and so on.