在TMEDA(四甲基乙基二胺)-Na_2O-SiO_2-Al_2O_3-H_2O体系(Ⅰ),Na_2O-K_2O-Al_2O_3-SiO_2-H_2-HCO_3^-CO_3^(2-) (Ⅱ)及Py(吡啶)-PrNH_2(正丙胺)-HF-SiO_2-H_2O体系(Ⅲ)中,分别合成了纯相FER沸石及FER硅沸石.用粉末XRD,FT-IR,^(29)Si MAS...在TMEDA(四甲基乙基二胺)-Na_2O-SiO_2-Al_2O_3-H_2O体系(Ⅰ),Na_2O-K_2O-Al_2O_3-SiO_2-H_2-HCO_3^-CO_3^(2-) (Ⅱ)及Py(吡啶)-PrNH_2(正丙胺)-HF-SiO_2-H_2O体系(Ⅲ)中,分别合成了纯相FER沸石及FER硅沸石.用粉末XRD,FT-IR,^(29)Si MAS NMR及TG/DTA等表征其结构性质,并用超微量电子真空吸附天平测定这些沸石样品对正己烷,甲醇和水的吸附等温线.结果表明:各体系合成的样品虽然结晶度高,呈现出FER沸石的典型结构特征,但由于它们的组成和晶格微结构不同,热稳定性与吸附性质有明显的差异.在(Ⅰ)体系中合成的FER沸石层错缺陷少,晶格完美,正己烷与甲醇的吸附量可达到理论值,结构破坏温度为1190℃.红外精细谱及^(29)Si MAS NMR高分辨谱证明FER硅沸石具有十分完美的骨架结构.由于晶胞收缩,它对正己烷与甲醇吸附量略低于理论值,并呈现出高度的疏水性.它的结构破坏温度高于1300℃.在(Ⅱ)体系中合成的FER型沸石结构缺陷多,沸石孔中的钾离子不易被质子完全交换.它的正己烷与甲醇吸附量均较低,而水的吸附量相对较高.吸附现象表明,正己烷和甲醇都被吸附于FER沸石的十元环主孔道中,分压较高时,甲醇可通过八元环进入小笼,而水的吸附性质则主要与各样品的Si-OH缺陷及骨架中的阳离子含量有关.展开更多
The structures of silicalite-1 and H、 Na form of ZSM-5 with various SiO2/Al2O3 ratios were characterized by powder XRD, 29Si MAS NMR, and the desorption process of р-xylene (p-x) on the zeolites was investigated by ...The structures of silicalite-1 and H、 Na form of ZSM-5 with various SiO2/Al2O3 ratios were characterized by powder XRD, 29Si MAS NMR, and the desorption process of р-xylene (p-x) on the zeolites was investigated by using TG/DTG/DTA. SiOH defects of ZSM-5 have no relation with the content of structural Al. Silicalite-1 possesses perfect framwork structure without SiOH defects and structural Al. On a curve of TG/DTG/DTA, p-x adsorbed by silicalite completely desorbs in the range of 57-174℃by two steps, accompaned with endothermal effect. While on the TG/DTG/DTA curves of H, Na-ZSM-5, there is a third desorption step of p-x in the range of 180-600℃ with exothermic effect. Below 180℃ the number of desorbed p-x molecules is related to pore space, but over 180℃,it is related to SiOH and positive ion linking with the structural Al.展开更多
Ca-montmorillonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, 29Si and 27A1 MAS NMR, to investigate the microstructure of the activated montmorillonites. Wi...Ca-montmorillonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, 29Si and 27A1 MAS NMR, to investigate the microstructure of the activated montmorillonites. With the increase of acid concentration and dissolution of cations of montmorillonite, the intensity of d(001) decreased obviously and significant changes of the microstructure of Si and Al occurred. There were two new types of structural units of Si atoms formed: (SiO)3SiOH units and Q4(0A1) units. For Al atoms, in the course of activation, the removal of one of a pair of octahedral aluminium atoms from montmorillonite removed two hydroxyl groups and left the other aluminum of the pair in the four-fold coordination. The 27A1 signal at 5 54.0 corresponding to AlIV arose from the four-coordinated Al in the octahedral sheet. This study first confirmed, by 29Si and 27A1 MAS NMR spectra, that the model of microstructural evolution for activated montmorillonite postulated by Thomas et al. (1950)展开更多
A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with +4NH exchange by using ammonium salt and calcinations (procedure I), or with +4NH exchange followed by treatment with acid (procedu...A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with +4NH exchange by using ammonium salt and calcinations (procedure I), or with +4NH exchange followed by treatment with acid (procedure II). The coordination state of Si and Al atoms in the framework, the property of ion exchange, and the adsorption of the H-STI zeolite samples prepared by different modification procedure were investigated with XRD, EDX, 29Si and 27Al MAS NMR, Ag+ ion exchange and N2 adsorption. The results of the investigations indicate that different procedure of the modification made variety on the distribution of the framework Si atoms and Al atoms, the content of non-framework aluminum, and the blocking channels and the shielding effect to the positions of the exchangeable cations. The H-STI zeolite prepared by the procedure II possesses high ion exchange capacity, open and perfect pore system, and high thermal stability.展开更多
基金Project supported by The National Natural Science Foundation of China(Grant CH29236120)-03)Gansu Longhai FuelChemical Company
文摘在TMEDA(四甲基乙基二胺)-Na_2O-SiO_2-Al_2O_3-H_2O体系(Ⅰ),Na_2O-K_2O-Al_2O_3-SiO_2-H_2-HCO_3^-CO_3^(2-) (Ⅱ)及Py(吡啶)-PrNH_2(正丙胺)-HF-SiO_2-H_2O体系(Ⅲ)中,分别合成了纯相FER沸石及FER硅沸石.用粉末XRD,FT-IR,^(29)Si MAS NMR及TG/DTA等表征其结构性质,并用超微量电子真空吸附天平测定这些沸石样品对正己烷,甲醇和水的吸附等温线.结果表明:各体系合成的样品虽然结晶度高,呈现出FER沸石的典型结构特征,但由于它们的组成和晶格微结构不同,热稳定性与吸附性质有明显的差异.在(Ⅰ)体系中合成的FER沸石层错缺陷少,晶格完美,正己烷与甲醇的吸附量可达到理论值,结构破坏温度为1190℃.红外精细谱及^(29)Si MAS NMR高分辨谱证明FER硅沸石具有十分完美的骨架结构.由于晶胞收缩,它对正己烷与甲醇吸附量略低于理论值,并呈现出高度的疏水性.它的结构破坏温度高于1300℃.在(Ⅱ)体系中合成的FER型沸石结构缺陷多,沸石孔中的钾离子不易被质子完全交换.它的正己烷与甲醇吸附量均较低,而水的吸附量相对较高.吸附现象表明,正己烷和甲醇都被吸附于FER沸石的十元环主孔道中,分压较高时,甲醇可通过八元环进入小笼,而水的吸附性质则主要与各样品的Si-OH缺陷及骨架中的阳离子含量有关.
文摘The structures of silicalite-1 and H、 Na form of ZSM-5 with various SiO2/Al2O3 ratios were characterized by powder XRD, 29Si MAS NMR, and the desorption process of р-xylene (p-x) on the zeolites was investigated by using TG/DTG/DTA. SiOH defects of ZSM-5 have no relation with the content of structural Al. Silicalite-1 possesses perfect framwork structure without SiOH defects and structural Al. On a curve of TG/DTG/DTA, p-x adsorbed by silicalite completely desorbs in the range of 57-174℃by two steps, accompaned with endothermal effect. While on the TG/DTG/DTA curves of H, Na-ZSM-5, there is a third desorption step of p-x in the range of 180-600℃ with exothermic effect. Below 180℃ the number of desorbed p-x molecules is related to pore space, but over 180℃,it is related to SiOH and positive ion linking with the structural Al.
基金This wok was supported by the National Natural Science Foundation of China (Grant No. 49972018)the Natural Science Foundation of Guangdong Province (Grant No. 990522).
文摘Ca-montmorillonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, 29Si and 27A1 MAS NMR, to investigate the microstructure of the activated montmorillonites. With the increase of acid concentration and dissolution of cations of montmorillonite, the intensity of d(001) decreased obviously and significant changes of the microstructure of Si and Al occurred. There were two new types of structural units of Si atoms formed: (SiO)3SiOH units and Q4(0A1) units. For Al atoms, in the course of activation, the removal of one of a pair of octahedral aluminium atoms from montmorillonite removed two hydroxyl groups and left the other aluminum of the pair in the four-fold coordination. The 27A1 signal at 5 54.0 corresponding to AlIV arose from the four-coordinated Al in the octahedral sheet. This study first confirmed, by 29Si and 27A1 MAS NMR spectra, that the model of microstructural evolution for activated montmorillonite postulated by Thomas et al. (1950)
文摘A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with +4NH exchange by using ammonium salt and calcinations (procedure I), or with +4NH exchange followed by treatment with acid (procedure II). The coordination state of Si and Al atoms in the framework, the property of ion exchange, and the adsorption of the H-STI zeolite samples prepared by different modification procedure were investigated with XRD, EDX, 29Si and 27Al MAS NMR, Ag+ ion exchange and N2 adsorption. The results of the investigations indicate that different procedure of the modification made variety on the distribution of the framework Si atoms and Al atoms, the content of non-framework aluminum, and the blocking channels and the shielding effect to the positions of the exchangeable cations. The H-STI zeolite prepared by the procedure II possesses high ion exchange capacity, open and perfect pore system, and high thermal stability.