A large single crystal of TPAF-AlPO4-5 molecular sieve was synthesized by hydrothermal crystallization in the presence of ammonium fluoride. Starting material composition was · 1 P2O5 · 1 Al2O3 · 2. 2 T...A large single crystal of TPAF-AlPO4-5 molecular sieve was synthesized by hydrothermal crystallization in the presence of ammonium fluoride. Starting material composition was · 1 P2O5 · 1 Al2O3 · 2. 2 TPAOH · 1. 7 NH4F ·318 H2O. The crystal size has a hexagonal prism with 80μm across and 500μm length.The structure of tetrapropylarnmonium fluoride - aluminium phosphate type-5 was investigated with X-ray diffraction. The unit cell composition is 12AlPO4 · TPAF, space group P6cc (a= 13. 740(5), c= 8. 474(4) A ). Average bond distances are: P-O 1. 564A and Al-O 1. 640A ,which may be due to the partial disorder of the arrangement of P, Al in the framework. The angles of O-T-O and T-O-T (T?P, Al) are 102-116° and 148-176°, respectively. Residue electron density was not well enough defined to give a precise position for tetrapropylammonium fluoride (TPAF). The template agent, TPA+ cations, situate in the 12-ring channels and F- anions locate in double 4-rings near the 12-ring channels. Fixing atomic positions for the TPAF reduced the unweighted and weighted R, R, from 0. 063 and 0. 082 to 0. 046 and 0. 042,respectively.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
Mesoporous molecular sieves, NbFAPO-5 and NbFAPSO-5 were hydrothermally synthesized with AlPO-5 type structure. Characterization of these molecular sieves was performed by X-ray diffraction to determine their structur...Mesoporous molecular sieves, NbFAPO-5 and NbFAPSO-5 were hydrothermally synthesized with AlPO-5 type structure. Characterization of these molecular sieves was performed by X-ray diffraction to determine their structure, ICP-EAS for their elemental composition and infrared spectrometry to access their acidic properties. X-ray diffraction patterns confirmed well AlPO-5 type structure. ICP-EAS analysis confirmed the incorporation of silicon (12.9%), aluminium (15.4%), phosphorous (21.9%), iron (5.62%) and niobium (0.39%) into AlPO-5 framework. Infrared spectrometry analysis showed that both Bronsted and Lewis sites were found in the synthesized samples. The presence of both Bronsted and Lewis acid site led to bifunctional function of NbFAPO-5 and NbFAPSO-5 molecular sieve in promoting both oxidation and esterification reactions. NbFAPSO-5 Bronsted acidity was higher than that of NbFAPO-5 and for Lewis acidity, NbFAPO-5 was higher than that of NbFAPO-5.展开更多
文摘A large single crystal of TPAF-AlPO4-5 molecular sieve was synthesized by hydrothermal crystallization in the presence of ammonium fluoride. Starting material composition was · 1 P2O5 · 1 Al2O3 · 2. 2 TPAOH · 1. 7 NH4F ·318 H2O. The crystal size has a hexagonal prism with 80μm across and 500μm length.The structure of tetrapropylarnmonium fluoride - aluminium phosphate type-5 was investigated with X-ray diffraction. The unit cell composition is 12AlPO4 · TPAF, space group P6cc (a= 13. 740(5), c= 8. 474(4) A ). Average bond distances are: P-O 1. 564A and Al-O 1. 640A ,which may be due to the partial disorder of the arrangement of P, Al in the framework. The angles of O-T-O and T-O-T (T?P, Al) are 102-116° and 148-176°, respectively. Residue electron density was not well enough defined to give a precise position for tetrapropylammonium fluoride (TPAF). The template agent, TPA+ cations, situate in the 12-ring channels and F- anions locate in double 4-rings near the 12-ring channels. Fixing atomic positions for the TPAF reduced the unweighted and weighted R, R, from 0. 063 and 0. 082 to 0. 046 and 0. 042,respectively.
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.
文摘Mesoporous molecular sieves, NbFAPO-5 and NbFAPSO-5 were hydrothermally synthesized with AlPO-5 type structure. Characterization of these molecular sieves was performed by X-ray diffraction to determine their structure, ICP-EAS for their elemental composition and infrared spectrometry to access their acidic properties. X-ray diffraction patterns confirmed well AlPO-5 type structure. ICP-EAS analysis confirmed the incorporation of silicon (12.9%), aluminium (15.4%), phosphorous (21.9%), iron (5.62%) and niobium (0.39%) into AlPO-5 framework. Infrared spectrometry analysis showed that both Bronsted and Lewis sites were found in the synthesized samples. The presence of both Bronsted and Lewis acid site led to bifunctional function of NbFAPO-5 and NbFAPSO-5 molecular sieve in promoting both oxidation and esterification reactions. NbFAPSO-5 Bronsted acidity was higher than that of NbFAPO-5 and for Lewis acidity, NbFAPO-5 was higher than that of NbFAPO-5.
