共查询到20条相似文献,搜索用时 265 毫秒
1.
2.
3.
4.
5.
6.
分别用氮气吸附-脱附测定、激光傅立叶红外(FTIR)、29Si和37Al固态魔角核磁共振(MASNMR)和微分热重(DTG)等手段表征了低表面活性剂浓度及低表面活性剂与硅原子摩尔比的十六烷基三甲基溴化钦与硅酸钠体系中不同温度形成的不同中孔M41S和微孔ZSM-5沸石.研究发现,合成温度从100℃提高至135℃,MCM-41的固体颗粒变细,孔壁厚增加而中孔表面积和体积降低.合成温度从135℃提高至150℃,由热稳定的六角相转化形成的层状M41S层间移去表面活性剂后,层面倒塌而失去中孔结构,红外骨架谱中出现双环振动谱带,同时层板硅羟基相互凝聚导致29SiMASNMR港失去精细结构.合成温度再提高至≥165℃,骨架硅羟基高度凝聚,Q3/Q4比大为降低,红外光谱中双环振动峰增强且位移至548cm-1,层状M41S转化为ZSM-5沸石.DTG结果显示,不同结构的分子筛的形成来自于在不同温度下CTMAB与硅酸根物种间的不同相互作用. 相似文献
7.
8.
干法合成纯硅丝光沸石 总被引:2,自引:0,他引:2
在Na2O-SiO2-EA体系中利用干法首次成功地合成了纯硅丝光沸石,采用XRD,SEM及IR等仪器分析方法对产物的结构,形貌,红外有架振动及稳定性等进行了表征。实验结果表明,干法合成的纯硅丝光沸石具有良好的耐酸性;与水热体系合成的丝光沸石相比,干法得到的丝光沸石的晶胞体积出现较明显的收缩趋势。 相似文献
9.
龙英才 《高等学校化学学报》1995,16(3):351-353
无定型二氧化硅在硅沸石表面上的固相转化龙英才(复旦大学化学系,上海,200433)关键词硅沸石,固相转化,无定型二氧化硅硅沸石(Silicalite-1)的晶体结构与ZSM-5相同,由于其疏水/亲有机物的独特吸附特性作为一种新型沸石吸附剂有广泛的应用... 相似文献
10.
采用XRD、SEM、FT-IR、MAS NMR等表征手段, 对以氟离子为结构导向剂无胺法合成的高硅丝光沸石进行了表征. 结果表明: 高硅丝光沸石结构属立方晶系, 晶胞参数小于传统低硅丝光沸石, 但b、c值要比相近硅铝比非氟体系合成的丝光沸石样品的大; 样品形貌及粒径与其硅铝比有关, 表明晶化条件对产物形貌及粒径均有影响; 随硅铝比的增大, FT-IR光谱中450、544、1053 cm-1谱带向高频移动, 720 cm-1谱带强度减弱, 表明骨架中铝减少而硅增多; 采用含氟无胺体系合成高硅丝光沸石时基本上不会产生非骨架铝. 相似文献
11.
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
12.
13.
Dealuminated Y zeolites (DAY) were obtained by steaming of NH4NaY at temperatures between 450 °C and 700 °C. They were characterised by means of 27Al and 29Si MAS NMR, IR spectroscopic and XRD measurements. The Si/Al framework ratios of samples were calculated using the 29Si MAS NMR signal intensities, the wave numbers of the double‐ring vibration band wDR and the asymmetrical TOT valence vibration wTOT of IR spectra as well as the XRD lattice constant a0. In contrast to actual Si/Al ratio obtained from wDR and a0, the NMR spectroscopic and wTOT values were determined to be too high because of the superposition of the signals coming from dealuminated zeolite framework and silica gel which forms in the zeolite as a result of steaming. The differently determined Si/Al ratios characterise the siliceous extra‐framework species. 相似文献
14.
Dr. Wolfgang Lutz Rainer Bertram Detlef Heidemann Rolf Kurzhals Claus Rüscher Galina Kryukova 《无机化学与普通化学杂志》2011,637(1):75-82
Zeolites of type USY (ultra‐stable Y) were obtained by steaming of NH4NaY modification. Samples were modified by subsequent alkaline treatment in KOH solution. USY and USY‐KOH were characterised by chemical element analysis, XRD, IR, 29Al and 29Si MAS NMR spectroscopic measurements. Correct silicon to aluminium ratios (Si/Al) were determined by XRD and IR (double ring vibration wDR) data whereas values calculated according to data of 29Si MAS NMR and IR spectroscopy (asymmetrical TOT valence vibration wTOT) appeared to be too high., In the latter case, the signals of the zeolite framework were strongly superimposed by that of extra‐framework silica gel (EFSi) formed during steaming. It was found that alkaline leaching induces desilication of silicon‐rich area of the zeolite framework and partial dissolution of EFSi. Silicate ions of both react with likewise dissolved extra‐framework aluminium (EFAl) to form X‐ray amorphous aluminosilicate. Consequently, the superposition of the 29Si MAS NMR signals of the zeolite framework by silica gel was reduced for Q4(0Al) but increased for Q4 (2Al) and Q4(3Al) structure units. A reinsertion of EFAl into the zeolite framework has not been observed. 相似文献
15.
16.
W. Lutz W. Wieker D. Müller M. Schneider C. H. Rüscher J.‐Ch. Buhl 《无机化学与普通化学杂志》2000,626(6):1460-1467
The steaming of zeolite Y (here at 873 K for 7 hours) leads to the formation of an amorphous aluminium aluminosilicate in addition to the dealuminated zeolite (DAY). An alkaline treatment of DAY causes the transformation of the non‐framework phase into an alkali aluminosilicate and the partial desilication of the DAY framework. The alkali aluminosilicate is decomposed by a moderate acid leaching under the formation of silica gel. The 29Si MAS NMR and IR spectra of DAY and its chemically treated modifications are superimposed by the signals of the crystalline zeolite framework and the amorphous non‐framework materials whereas XRD measurements only characterize the current state of the framework. 相似文献
17.
Structure determinations of siliceous zeolite-sorbate host-guest complexes by solid-state NMR require highly resolved 29Si MAS NMR spectra. As the temperature is lowered, the 29Si MAS NMR spectra of many zeolite-sorbate complexes become broadened such that the resolution of the individual 29Si peaks is lost, limiting the application of solid-state NMR for structure determination. It is shown that the 29Si peak widths are related to the 29Si T2 relaxation times and that the source of the 29Si relaxation and the line broadening is paramagnetic molecular oxygen in the channels of the zeolite. Removal of the oxygen by purging the sample with nitrogen gas leads to a dramatic increase in the resolution of the 29Si MAS NMR spectrum of the p-dibromobenzene/ZSM-5 complex. An analysis of the individual 29Si T1 relaxation times reveals that the oxygen molecules are localized mainly in the zigzag channels of ZSM-5, suggesting that the p-dibromobenzene molecules are located in the channel intersections. 相似文献
18.
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
19.
Nigel J. Clayden Serena Esposito Michele Pansini 《Journal of solid state chemistry》2006,179(7):1957-1964
The thermal transformation of Ba exchanged zeolite X to celsian has been studied by 27Al and 29Si MAS NMR spectroscopy. Evidence for the degradation of the zeolite framework is present in the 29Si NMR spectra after thermal treatment at 850 °C. Confirmation is provided by the 29Si NMR data that synthesis of celsian via the decomposition of Ba exchanged zeolite leads to a single defect phase. Clustering of the isomorphous replacement of aluminium by silicon must occur to explain the observed 29Si chemical shifts. The 27Al NMR data show distorted aluminium co-ordination sites upon the thermal transformation of Ba exchanged zeolite X. The distortions present in the amorphous matrix are greater than those present in the monoclinic and hexagonal crystalline phases of celsian. 相似文献
20.
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