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 microstructural study was conducted on cement and cement-slag pastes immersed in different concentrations of Mg（NO3）2 solutions utilizing ^29Si, ^27Al NMR spectroscopy and XRD techniques. The results show that t...The microstructural study was conducted on cement and cement-slag pastes immersed in different concentrations of Mg（NO3）2 solutions utilizing ^29Si, ^27Al NMR spectroscopy and XRD techniques. The results show that the hydration of both the cement and cement-slag pastes is delayed when the pastes are cured in Mg（NO3）2 solutions as compared to the pastes cured in water. Moreover, Mg^2＋ ions also exhibit an decalcifying and dealuminizing effect on the C-A-S-H in cement and cement-slag pastes, and thereby decrease Ca/Si and Al[4]/Si ratios of the C-A-S-H. The dealuminization of C-A-S-H is mitigated for cement-slag paste as compared to pure cement paste. The depolymerized calcium and aluminum ions from C-A-S-H gel mainly enter the pore solution to maintain the pH value and form Al^[6] in TAH, respectively. On the other hand, Mg^2＋ ions exert an impact on the intra-transition between Al^[6] species, from AFm and hydrogarnet to hydrotalcite-like phase. NO3^-ions are interstratified in the layered Mg-Al structure and formed nitrated hydrotalcite-like phase（Mg1-xAlx（OH）2（NO3）x·nH2O）. Results from both ^27Al NMR and XRD data show that ettringite seems not to react with Mg^2＋ ions.展开更多
RECENTLY a new family of mesoporous molecular sieves,M41S,was reported by researchers atMobil R&D Corporation.As a member of the family,MCM-41,which exhibits a hexagonalarray of uniform channel mesopores,has been ...RECENTLY a new family of mesoporous molecular sieves,M41S,was reported by researchers atMobil R&D Corporation.As a member of the family,MCM-41,which exhibits a hexagonalarray of uniform channel mesopores,has been synthesized.The channel size can be variedfrom approximately 1.5 nm to greater than 10 nm by choosing different surfactants,auxiliarychemicals(1,3,5-trimethylbenzene)in the reactant,and by changing the reaction condi-tions.The wall thickness of this kind of molecular sieve is in the range of 0.3 to 1.3 nm esti-展开更多
1 Introduction To study the acidic properties of Y-type zeolites has important meaning in the field of zeolite catalysis. The nature and numbers of active sites of Y-zeolites can be modified by dealumination and rare ...1 Introduction To study the acidic properties of Y-type zeolites has important meaning in the field of zeolite catalysis. The nature and numbers of active sites of Y-zeolites can be modified by dealumination and rare earth ion exchange to increase the catalytic activity and stability of modified Y-zeolites. In view of the zeolite structure,the origin of strong acid sites is due to the change of the density and distribution of the framework aluminum atoms, which results in the increasing of the isolated framework aluminum atoms or those with no展开更多
A series of different H-mordenites from acid leaching and steam calcination have beenmeasured with <sup>29</sup>Si NMR. Through analysis of these solid-state <sup>29</sup>Si NMR spectra, theres...A series of different H-mordenites from acid leaching and steam calcination have beenmeasured with <sup>29</sup>Si NMR. Through analysis of these solid-state <sup>29</sup>Si NMR spectra, theresults related to dealumination process of mordenite are obtained. It is shown that mor-denite is combined by four kinds of non-equivalent Si （or Al） via oxygen bridges. The deal-umination order is T（1）, T（2）, T（4） and T（3）. The dealuminated amount in the non-equivalentsites during different dealumination processes has also been discussed in detail.展开更多
Sol-gel method is a technique to synthesize inorganic materials based on wet-chemical reaction theory. The results have shown that reactants tetraethyl orthosilicate （TEOS） and Ca（NO3）2·4H2O can form sol and ...Sol-gel method is a technique to synthesize inorganic materials based on wet-chemical reaction theory. The results have shown that reactants tetraethyl orthosilicate （TEOS） and Ca（NO3）2·4H2O can form sol and gel in solution at 50-60 ℃, and the cosolvents are propyl alcohol （NPA） and H2O, the catalyst is HNO3. This sol-gel is burned for 12 hat 1 350-1 450 ℃ so that the organic matter, free water （moisture） in sol-gel system are removed and a solid reaction has taken place to form the resulting product. The product has been confirmed to be C3S by XRD, SEM and 29Si MAS NMR, as well as free lime content of the product which is less than 0.2% was determined by propanetriol-ethanol-method. The analysis determined by EDXA has indicated that the n（Ca）/n（Si） ratio in corresponding to micro-region is close to theoretical value of 3∶1. This resulting product is C3S with Si sites of Q0 polymerization, and has higher purity and hydraulic activities at earlier age of hydration.展开更多
Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in depende...Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in dependence of an increasing CaO/SiO2 ratio (C/S ratios) from 0.41 up to 1.66 at temperatures in the crossover region of tobermorite to xonotlite (180℃ and 230℃). Parallel runs with the same C/S ratio but on the one hand with constant mass of quartz and variation of lime and on the other hand under reverse conditions (constant mass of lime but variable amounts of quartz) were performed at both temperatures. The aim was to clarify the connections of crystallization mechanism and kinetics of phase formation with structure, crystallinity and morphology of the CSH’s in the mentioned C/S ratio for both temperatures in the tobermorite-xonotlite crossover region. The parallel experiments with different mass ratios of the educts are important to study the influence of time evaluation of supersaturation within the solution under the peculiarities of the retrograde solubility of lime but accelerated solubility of quartz. The products were characterized by XRD, SEM/EDX, FTIR and 29Si MAS NMR spectroscopy (using the Q-site nomenclature [1]). The experiments could clarify some important connections of crystallization process and the reaction pathway.展开更多
采用水热合成法,以二正丙胺(DPA)和二异丙胺(DIPA)混合物为模板剂合成SAPO-11分子筛,考察了模板剂用量和混合模板剂中DPA和DIPA配比对所得产物的影响,并通过XRD、N2吸附、NH3-TPD和29Si MAS NMR等手段对样品进行了表征。结果表明,改变...采用水热合成法,以二正丙胺(DPA)和二异丙胺(DIPA)混合物为模板剂合成SAPO-11分子筛,考察了模板剂用量和混合模板剂中DPA和DIPA配比对所得产物的影响,并通过XRD、N2吸附、NH3-TPD和29Si MAS NMR等手段对样品进行了表征。结果表明,改变模板剂用量和配比不仅可以调节SAPO-11结晶度,还会改变Si在分子筛骨架上的分布,从而调节SAPO-11的酸性。当模板剂用量比为1.5,模板剂中DPA的质量分数为66%时,样品的Si区面积最小,Si(nAl)(0<n<4)结构最多。因此,分子筛酸性和对正十四烷异构活性也最高。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Funded by National Natural Science Foundation of China(Nos.51778513,51402003,51578004)China Ministry of Science and Technology(No.2015CB655101)
文摘The microstructural study was conducted on cement and cement-slag pastes immersed in different concentrations of Mg（NO3）2 solutions utilizing ^29Si, ^27Al NMR spectroscopy and XRD techniques. The results show that the hydration of both the cement and cement-slag pastes is delayed when the pastes are cured in Mg（NO3）2 solutions as compared to the pastes cured in water. Moreover, Mg^2＋ ions also exhibit an decalcifying and dealuminizing effect on the C-A-S-H in cement and cement-slag pastes, and thereby decrease Ca/Si and Al[4]/Si ratios of the C-A-S-H. The dealuminization of C-A-S-H is mitigated for cement-slag paste as compared to pure cement paste. The depolymerized calcium and aluminum ions from C-A-S-H gel mainly enter the pore solution to maintain the pH value and form Al^[6] in TAH, respectively. On the other hand, Mg^2＋ ions exert an impact on the intra-transition between Al^[6] species, from AFm and hydrogarnet to hydrotalcite-like phase. NO3^-ions are interstratified in the layered Mg-Al structure and formed nitrated hydrotalcite-like phase（Mg1-xAlx（OH）2（NO3）x·nH2O）. Results from both ^27Al NMR and XRD data show that ettringite seems not to react with Mg^2＋ ions.
文摘RECENTLY a new family of mesoporous molecular sieves,M41S,was reported by researchers atMobil R&D Corporation.As a member of the family,MCM-41,which exhibits a hexagonalarray of uniform channel mesopores,has been synthesized.The channel size can be variedfrom approximately 1.5 nm to greater than 10 nm by choosing different surfactants,auxiliarychemicals(1,3,5-trimethylbenzene)in the reactant,and by changing the reaction condi-tions.The wall thickness of this kind of molecular sieve is in the range of 0.3 to 1.3 nm esti-
基金Project supported by the National Natural Science Foundation of China.
文摘1 Introduction To study the acidic properties of Y-type zeolites has important meaning in the field of zeolite catalysis. The nature and numbers of active sites of Y-zeolites can be modified by dealumination and rare earth ion exchange to increase the catalytic activity and stability of modified Y-zeolites. In view of the zeolite structure,the origin of strong acid sites is due to the change of the density and distribution of the framework aluminum atoms, which results in the increasing of the isolated framework aluminum atoms or those with no
文摘A series of different H-mordenites from acid leaching and steam calcination have beenmeasured with <sup>29</sup>Si NMR. Through analysis of these solid-state <sup>29</sup>Si NMR spectra, theresults related to dealumination process of mordenite are obtained. It is shown that mor-denite is combined by four kinds of non-equivalent Si （or Al） via oxygen bridges. The deal-umination order is T（1）, T（2）, T（4） and T（3）. The dealuminated amount in the non-equivalentsites during different dealumination processes has also been discussed in detail.
文摘以含氟的二胺5,5’-(六氟异丙基)-二-(2-氨基苯酚)(6FHP)及二酐4, 4’-(六氟异丙基)-苯二酸酐(6FDA)或均苯四甲酸酐(PMDA)为单体,以分散红 1(DR1)为活性生色分子合成具有非线性光学特性的含氟聚酰亚胺,并采用溶胶-凝胶(Sol-Gel)法合成相应的聚酰亚胺／SiO2杂化材料．采用固态29 Si MAS NMR谱研究了含氟聚酰亚胺／SiO2杂化材料的交联结构,结果表明杂化材料中是以T3、Q3、Q4结构为主,说明在杂化材料中形成了交联网状结构．采用衰减全反射(ATR)测定了聚酰亚胺和杂化材料在832 nm处的电光系数,其值分别为 32、28、34和29 pm／V,结果表明具有较高的电光系数．
基金Financially supported by National Basic Research Program of China (973Program)(No. 2009CB623200)National Natural Science Foundation of China(No.50972109)Doctoral Program of Higher Education (No. 20090141110021)
文摘Sol-gel method is a technique to synthesize inorganic materials based on wet-chemical reaction theory. The results have shown that reactants tetraethyl orthosilicate （TEOS） and Ca（NO3）2·4H2O can form sol and gel in solution at 50-60 ℃, and the cosolvents are propyl alcohol （NPA） and H2O, the catalyst is HNO3. This sol-gel is burned for 12 hat 1 350-1 450 ℃ so that the organic matter, free water （moisture） in sol-gel system are removed and a solid reaction has taken place to form the resulting product. The product has been confirmed to be C3S by XRD, SEM and 29Si MAS NMR, as well as free lime content of the product which is less than 0.2% was determined by propanetriol-ethanol-method. The analysis determined by EDXA has indicated that the n（Ca）/n（Si） ratio in corresponding to micro-region is close to theoretical value of 3∶1. This resulting product is C3S with Si sites of Q0 polymerization, and has higher purity and hydraulic activities at earlier age of hydration.
文摘Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in dependence of an increasing CaO/SiO2 ratio (C/S ratios) from 0.41 up to 1.66 at temperatures in the crossover region of tobermorite to xonotlite (180℃ and 230℃). Parallel runs with the same C/S ratio but on the one hand with constant mass of quartz and variation of lime and on the other hand under reverse conditions (constant mass of lime but variable amounts of quartz) were performed at both temperatures. The aim was to clarify the connections of crystallization mechanism and kinetics of phase formation with structure, crystallinity and morphology of the CSH’s in the mentioned C/S ratio for both temperatures in the tobermorite-xonotlite crossover region. The parallel experiments with different mass ratios of the educts are important to study the influence of time evaluation of supersaturation within the solution under the peculiarities of the retrograde solubility of lime but accelerated solubility of quartz. The products were characterized by XRD, SEM/EDX, FTIR and 29Si MAS NMR spectroscopy (using the Q-site nomenclature [1]). The experiments could clarify some important connections of crystallization process and the reaction pathway.
文摘采用水热合成法,以二正丙胺(DPA)和二异丙胺(DIPA)混合物为模板剂合成SAPO-11分子筛,考察了模板剂用量和混合模板剂中DPA和DIPA配比对所得产物的影响,并通过XRD、N2吸附、NH3-TPD和29Si MAS NMR等手段对样品进行了表征。结果表明,改变模板剂用量和配比不仅可以调节SAPO-11结晶度,还会改变Si在分子筛骨架上的分布,从而调节SAPO-11的酸性。当模板剂用量比为1.5,模板剂中DPA的质量分数为66%时,样品的Si区面积最小,Si(nAl)(0<n<4)结构最多。因此,分子筛酸性和对正十四烷异构活性也最高。
