共查询到18条相似文献,搜索用时 140 毫秒
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高硅FAU沸石与甲胺吸附物的相互作用 总被引:1,自引:0,他引:1
合成高硅沸石中所用的模板剂胺类分子与沸石骨架 Si—O基团间的相互作用机理尚不清楚 .迄今为止 ,沸石与吸附胺之间的相互作用的研究还只限于测定沸石酸性质 [1,2 ]、表面羟基活性位或了解模板分子在沸石骨架中的位置和状态 [3,4 ] .甲胺、乙胺在骨架完美的高硅 FAU(Y型 )沸石上的亲和性指数 AT 值 ,即被吸附有机物脱附峰温与该有机物的沸点之差分别高达 1 60与 1 5 0℃[5] .而在高硅 MFI(Silicalite-1 )沸石上为 1 60与 1 2 7℃ [6 ] .与大多数有机物不同 ,被吸附的胺类脱附时的吸热效应十分明显 .上述现象表明胺与高硅沸石骨架 O2 -… 相似文献
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用测定吸附等温线法研究乙胺、正戊烷和乙醇在疏水高硅FAU沸石上的吸附热效应。根据Clapeyron-Clausius方程,处理吸附等温线,得到不同覆盖度C(C=被吸附分子数/晶胞)的等量吸附热Qst(C)(一定覆盖度C时由Clapeyron-Clausius方程计算的吸附热)及平均等量吸附热Qst^*(一定温度区间里等量吸附热Qst的平均值),以及Qst^*与沸点蒸发热△Hv的差值△H1(定义为相互作用强度△H1=Qst^*-△Hv)。所研究的三种有机分子的△H1的次序为△H1(乙胺)>△H1(正戊烷)>>△H1(乙醇)。这与AT值(定义为脱附温度Td与吸附质的沸点温度Tb的差值,无需单位)有正相关关系。由AT值观察到的高硅FAU沸石Si-O骨架与被吸附乙胺之间可能存在的强相互作用、为本研究测定的热力学定量数据△H1值所证明。 相似文献
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用^13C HPDEC MAS NMR与热分析方法表征了在四氢呋喃(THF)-Na2O-SiO2- Al2O3-H2O体系中水热合成的高硅Na-THF-FER沸石、酸交换后的H-THF-FER沸石以及 吸附于Na-FER和H-FER沸石中的THF。结果证明,模板剂分子THF位于Na-THF-FER沸 石骨架的FER笼内,平衡骨架阳离子Na^+主要存在于十元环孔道;而吸附子FER沸石 中的THF仅处于十元环孔道中,合成样品中THF的化学位移与液态THF相比,向低场 移动,谱线明显变宽,表明THF分子与FER笼之间存在很强的相互作用。 相似文献
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将高硅TON, MFI和FAU沸石分别浸渍于SnCl2溶液,再于873 K温度下焙烧,在高硅TON,MFI和FAU沸石外表面制备出二氧化锡纳米粒子。用XRD和SAED表征生成物的物相,TEM表征形成二氧化锡纳米粒子的形貌、尺寸和聚集状态。结果显示:在TON, MFI和FAU沸石外表面形成二氧化锡纳米粒子的尺寸分别在8 nm, 10-80 nm和6 nm。在室温下用40%的氢氟酸分解SnO2-TON和SnO2-MFI分别得到二氧化锡微胶囊和网状的二氧化锡纳米结构。同在NaY沸石表面形成的纳米二氧化锡比较,在具有一维孔道体系的TON沸石和二维孔道体系的MFI沸石外表面形成的纳米二氧化锡的形貌与聚集状态都不相同,这表明沸石的骨架类型、表面结构与特性在沸石外表面形成二氧化锡纳米结构时起重要作用。 相似文献
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在TMEDA(四甲基乙基二胺)-Na2O-SiO2-Al2O3-H2O体系(I),Na2O-K2O-Al2O3-SiO2-H2O-HCO3^--CO3^2^-体系(II)及Py(吡啶)-PrNH2(正丙胺)-HF-SiO2-H2O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, 29Si 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29Si 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。 相似文献
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CXN天然沸石的研究1: 离子交换与结构性质表征 总被引:2,自引:0,他引:2
采用离子交换和焙烧等方法,对我国CXN天然沸石(STI型)进行改性。应用化学分析,粉末XRD,TG/DTA,^2^7AlMASNMR,^2^9SiMASNMR,低温N~2吸附等方法表征相关的结构、离子交换等性质。CXN沸石的晶胞组成Na~0~.~2Mg~0~.~1Ca~8~.~4[Al~1~7~.~2Si~5~4~.~8O~1~4~4].65H~2O,属富钙型。经离子交换脱Ca^2^+后的沸石在焙烧过程中伴随有骨架脱铝,骨架的热稳定性已由原样的500℃以下提高到700℃以上。交换改性后的沸石,呈现反映该沸石微孔特性的I型氮吸附等温线。 相似文献
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The leading role of association in framework modification of highly siliceous zeolites with adsorbed methylamine. 总被引:1,自引:0,他引:1
Ai-Jie Han Juan Guo Hui Yu Yu Zeng Yue-Fang Huang He-Yong He Ying-Cai Long 《Chemphyschem》2006,7(3):607-613
Affinity index (AT value), adsorption heat, X-ray diffraction (XRD), and 13C and 29Si magic-angle spinning (MAS) NMR, FTIR, and Raman spectroscopies were used to study the interaction of highly siliceous MFI-, FAU-, and FER-type zeolites with adsorbed methylamine (MA). Compared with the data for methanol, the much higher AT values and adsorption heats, and significant changes in XRD patterns, 29Si MAS NMR spectra, and FTIR spectra for the zeolites after adsorption of MA, revealed a strong hydrogen-bonding interaction between the perfect framework of the zeolites and the adsorbed MAs. This interaction results from the fact that the H atom of the amine group attacks the [Si-O] framework to form a Si-OHN bond, which leads to the appearance of Si-N bonds in the zeolites at 323 K. Therefore, the zeolite framework can be modified with MA under mild conditions. The highly siliceous MFI zeolite and the H-ZSM-5 zeolite with SiO2/Al2O3=31:1 were modified with MA and investigated by temperature-programmed desorption of CO2. The modified zeolites exhibited greatly enhanced basic properties in comparison with those of the raw materials. The influence of defects in the zeolite on the adsorption and the interaction with MA is discussed. 相似文献
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Introduction Oxygen and nitrogen have been produced tradition-ally by cryogenic distillation of air. Methods for the non-cryogenic separation based on selective adsorption have been developed and commercialized since the 1970s and have led to a cost-effective process for this important separation.1 Low-silica zeolites are important materials for producing oxygen by selective adsorption of nitrogen. In 19891990, a new generation of lith-ium-based adsorbents was developed.2,3 Highly lithium exc… 相似文献
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W. Liu Y. Xu She-Tin Wong L. Wang J. Qiu N. Yang 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):257-265
By using a high-resolution solid state nuclear magnetic resonance spectrometer with 27Al and 29Si probes, the interaction between Mo species and HZSM-5 of frsol|Mo/HZSM-5 catalysts has been studied. The results show that there is a strong interaction between Mo species and HZSM-5 zeolite. The framework aluminum in the zeolite can be easily extracted by the introduction of Mo species. The extractability of framework aluminum by Mo species increases with increasing Mo loading and the calcination temperature. The extraction process leads to the formation of non-framework Al at first and then a new crystalline phase of Al2(MoO4)3. The dealumination of the catalyst having a Mo loading of 15% and had been calcined at 973 K is so severe that all the aluminum in the framework are extracted and no framework Al could be detected by 27Al MAS NMR. The catalyst, therefore, lost its catalytic activity for methane dehydrogenation and aromatization in the absence of oxygen. The Si/Al ratio measured from 29Si MAS NMR further confirms the dealumination process observed by 27Al MAS NMR. The MAS NMR results give us an evidence that Al2(MoO4)3 crystallites are much less active for the reaction. 相似文献
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The adsorption of methylamine on highly siliceous MFI, FAU and FER-type zeolites was investigated withXRD, FT-IR, Raman, ^13C and ^29Si MAS NMR, and compared with the adsorption of methanol. As the adsorption of the amine, the relative intensity of XRD peaks of the zeolites has been changed significantly, the high-resolution ^29Si MAS NMR peaks have been broadened and shifted to low field, and the resonance of Si-OH groups has appeared. The vibration of N-H has been shifted to low frequency and C-N vibration moved to high frequency in the IR spectra, and the ^13C resonance peak broadened and shifted to high field for the adsorbed amine. The facts reveal an associating interaction between the perfect framework of the zeolites and the adsorbed methylamine with hydrogen bonds, leading to the formation of Si-OH groups and the high desorption temperature of the methylamine from the zeolites. 相似文献
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