Multinucleax solid-state NMR was employed to study the silicon-substitutedmolecular sieve Si-VPI-5. 29Si and 27Al NMR suggest that Si can be incorporated intothe framework of VPI-5 and the substitution of two silicon ...Multinucleax solid-state NMR was employed to study the silicon-substitutedmolecular sieve Si-VPI-5. 29Si and 27Al NMR suggest that Si can be incorporated intothe framework of VPI-5 and the substitution of two silicon atoms for an aluminium atomplus a phosphorus atom is predominant. Such substitution is limited in a certain domainof the crystal and "silicon rich" regions are thus generated. 1H MAS spectra reveal that asmall arnount of silicon atoms substitute phosphorus only and SiOHAl groups are formed,which provides the acidic source for the molecular sieves. Si-VPI-5 prepared with silicagel as the silicon source exhibits a higher content of SiOHAl groups than that preparedwith (EtO)4Si.展开更多
The aluminophosphate molecular sieve VPI-5 has received much attention as a new structure containing one-dimensional circular pores circumscribed by 18 tetrahedral atoms. The AlPO;-8 is another new type of structure w...The aluminophosphate molecular sieve VPI-5 has received much attention as a new structure containing one-dimensional circular pores circumscribed by 18 tetrahedral atoms. The AlPO;-8 is another new type of structure which was found to contain 1 4-ring open pores. Recently, we have successfully synthesized the molecular sieves of VPI-5 and AlPO;-8, and found that the mixture of VPI-5 and AlPO;-8 was easily formed under similar conditions, and VPI-5 can be converted to AlPO;-8 by dehydration via heating. It is suggested that there exists relationship between the structures of VPI-5 and A1PO;-8. Therefore, the study on the transition and relationship between VPI-5 and A1PO;-8 is very important for designing and preparing new molecular sieves with new structures.展开更多
The molecular sieve VPI-5 was synthesized by using various organic amines (DEA, Di-PA, DBA, DPenA, TBA, DEOA and TEOA) as the structure-directing agent. The use of DPA enlarged the range of the crystallization tempera...The molecular sieve VPI-5 was synthesized by using various organic amines (DEA, Di-PA, DBA, DPenA, TBA, DEOA and TEOA) as the structure-directing agent. The use of DPA enlarged the range of the crystallization temperature from 110℃ to 190℃ in the synthesis of VPI-5, while the use of TEOA changed the composition of the reactants in a broad variety. Diamines are the typical amines in the synthesis of VPI-5. Among them DBA and DPA are the most favorite structure-directing agents for the synthesis of VPI-5 molecular sieve.展开更多
The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnopho...The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnophosphate molecular sieves, the synthesis of the molecular sieves of VPI-5 type ls of many unique features. Both VPI-5 and Si-VPI-5 were characterized by XRD, IR, TG-DTA, and MAS-NMR.展开更多
文摘Multinucleax solid-state NMR was employed to study the silicon-substitutedmolecular sieve Si-VPI-5. 29Si and 27Al NMR suggest that Si can be incorporated intothe framework of VPI-5 and the substitution of two silicon atoms for an aluminium atomplus a phosphorus atom is predominant. Such substitution is limited in a certain domainof the crystal and "silicon rich" regions are thus generated. 1H MAS spectra reveal that asmall arnount of silicon atoms substitute phosphorus only and SiOHAl groups are formed,which provides the acidic source for the molecular sieves. Si-VPI-5 prepared with silicagel as the silicon source exhibits a higher content of SiOHAl groups than that preparedwith (EtO)4Si.
基金Supported by the National Natural Science Foundation of China
文摘The aluminophosphate molecular sieve VPI-5 has received much attention as a new structure containing one-dimensional circular pores circumscribed by 18 tetrahedral atoms. The AlPO;-8 is another new type of structure which was found to contain 1 4-ring open pores. Recently, we have successfully synthesized the molecular sieves of VPI-5 and AlPO;-8, and found that the mixture of VPI-5 and AlPO;-8 was easily formed under similar conditions, and VPI-5 can be converted to AlPO;-8 by dehydration via heating. It is suggested that there exists relationship between the structures of VPI-5 and A1PO;-8. Therefore, the study on the transition and relationship between VPI-5 and A1PO;-8 is very important for designing and preparing new molecular sieves with new structures.
基金Supported by the National Natural Science Foundation of China
文摘The molecular sieve VPI-5 was synthesized by using various organic amines (DEA, Di-PA, DBA, DPenA, TBA, DEOA and TEOA) as the structure-directing agent. The use of DPA enlarged the range of the crystallization temperature from 110℃ to 190℃ in the synthesis of VPI-5, while the use of TEOA changed the composition of the reactants in a broad variety. Diamines are the typical amines in the synthesis of VPI-5. Among them DBA and DPA are the most favorite structure-directing agents for the synthesis of VPI-5 molecular sieve.
基金Supported by the National Natural Science Foundation of China
文摘The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnophosphate molecular sieves, the synthesis of the molecular sieves of VPI-5 type ls of many unique features. Both VPI-5 and Si-VPI-5 were characterized by XRD, IR, TG-DTA, and MAS-NMR.
