共查询到14条相似文献,搜索用时 62 毫秒
1.
利用水热合成的方法,使用新型的表面活性剂十六烷基三甲基对苯磺酸盐作为模板剂合成了高质量的MCM-48介孔分子筛,并用X-射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)以及N2吸附-脱附进行了表征。合成过程的研究表明该合成体系经历了三相,起始相为具有六方对称性的MCM-41,随着加热时间的延长,生成了具有立方对称性的MCM-48,进一步延长加热时间则生成了层状相MCM-50。三相转变发生的核心驱动力来自于表面活性剂有效堆积参数g因子的改变,随着反应时间的延长,由于对甲基苯磺酸根离子(Tos-)的流失,表面活性剂极性头所占的有效面积(a0)明显减小,g值变大。另外,XRD、傅立叶变换的红外光谱(FT-IR)以及固体魔角自旋核磁共振(29Si MAS NMR)的表征结果证明:随着晶化时间的延长,相转变的同时伴随着介孔材料的孔壁逐渐由原子无序的非晶态向原子有序的晶态结构转变。最终形成的原子有序层状介孔分子筛可以作为扩孔型微孔分子筛合成的有效前驱体。 相似文献
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缓冲体系中高热和水热稳定性的MCM-48介孔分子筛的合成 总被引:3,自引:0,他引:3
利用混合阳离子-非离子表面活性剂为模板剂在缓冲体系中成功地合成出具有高热和水热稳定性的MCM-48介孔材料. 通过XRD, N2吸附-脱附, 29Si MAS NMR和 31P MAS NMR等手段对样品进行了表征. 结果表明, 合成的MCM-48材料具有高的比表面积和高度有序的孔道系统. 样品在空气中于900 ℃下焙烧15 h和在600 ℃ 100%水蒸气下处理8~10 h, 仍能保持良好的立方孔道结构, 显示很高的热稳定性和极好的水热稳定性. 相似文献
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MCM-48介孔分子筛的合成研究 总被引:23,自引:0,他引:23
利用水热法合成了MCM-48介孔分子筛,通过IR,TG-DTA,XRD,TEM,N2吸附等方法对产物进行了表征,并系统地研究了晶化温度、晶化时间、凝胶组成等对合成MCM-48介孔分子筛的影响 相似文献
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介孔材料B-Al-MCM-48合成的新方法 总被引:1,自引:2,他引:1
首次在两种阳离子表面活性剂存在的弱碱反应体系中加入三乙醇胺进行分子调变从而合成了具有较高稳定性和酸性的介孔材料B-Al-MCM-48,并用XRD、IR、TEM、NMR等油试手段对其进行了表征,同时阐述了其合成化学特点。结果表明,实验产品有序度高,介孔排布均匀,孔径大约介于2.0nm-3.0nm,比表面积为1200m^2/g,孔容为1.18mL/g;孔墙中引入的硼以四配位形式存在,改善了沸石酸性和稳定性。进而以轻汽油的催化加氢为探针反应考察了载Ni后介孔材料B-Al-MCM-48的催化活性,与现行X型沸石催化剂载体相比,脱氮、脱硫和芳烃转化大幅度提高。 相似文献
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A new crystalline phase (via amorphous intermediate), NCUZ-1, was obtained when MCM-41 (Si/Al=9) was under prolonged heating in the mother liquid (which contains NaAlO2, [N(CH3)4]2SiO3, SiO2, and surfactant C16H33N(CH3)3OH(aq) at 105°C for more than two weeks. The largest d spacing of NCUZ-1 calculated from X-ray diffraction data is approx. 6 Å, indicating that the long-range order of the mesopores in MCM-41 was not present in NCUZ-1. Nitrogen absorption studies showed that NCUZ-1 contains both mesopores and micropores. The volume ratio of the mesopore to micropore is approx. 10 to 1 and the BET surface area is 400 m2/g. The TEM micrograph of NCUZ-1 revealed a homogenous phase with distorted mesopores. The 13C NMR spectrum of NCUZ-1 before calcination is similar to that of uncalcined MCM-41, indicating that the organic templates in both phases have a similar structure. In the phase transformation process, the counteranion (OH−) of the surfactant template played an important role. It increased the solubility of the aluminosilicate wall; the breaking and reforming the Si–O and Al–O bonds make the phase transformation possible, although the process is very slow. When C16H33N(CH3)3Cl, instead of C16H33N(CH3)3OH, was used as a template, no NCUZ-1 phase was obtained under the same reaction conditions. TEM micrograph, nitrogen absorption isothermal, and 13C NMR spectra of NCUZ-1 suggested that the mesopores were present in the NCUZ-1 phase, although there is no long-range order of these mesopores. 相似文献
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Hariharaputhiran Subramanian Ranjit T. Koodali 《Reaction Kinetics and Catalysis Letters》2008,95(2):239-245
Fe-MCM-48 mesoporous material was found to be a highly active catalyst for the Baeyer-Villiger oxidation of several cyclic
ketones. The catalyst could be reused several times without any loss of activity. 相似文献
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Wieslaw J. Roth 《Adsorption》2009,15(3):221-226
The synthesis of cubic mesoporous material MCM-48 has been simplified and can be accomplished via facile hydrothermal synthesis
using convenient commercial reagents. The cubic structure evolves from the initially formed hexagonal MCM-41 and undergoes
slow conversion to the lamellar MCM-50 precursor. The system was sampled at 1 hr intervals and the intermediate products characterized
by elemental analysis, X-ray powder diffraction and adsorption. The results are discussed from the standpoint of possible
mechanisms of MCM-48 generation. 相似文献
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Broad-band dielectric spectroscopy was used to investigate the dielectric properties of the meso- porous materials MCM-48,
Al-MCM-48 and Ti-MCM-48. The samples were examined in the frequency range from 20 Hz to 1 MHz and in the temperature range
from −100 to 250 °C. The dielectric relaxation of the materials has a complex nonexponential behavior with some common features
for all the samples. The dielectric spectroscopy and Fourier transform IR measurements identified the relaxation process related
to percolation of H+ ions associated with silanol groups and water adsorbed in the materials. The non-Debye behavior of the macroscopic dipole
correlation functions related to the percolation process allowed us to extract the fractal dimensions of the paths of excitation
transfer within the porous medium, and the porosity of each sample was estimated.
Received: 7 September 1999 Accepted: 10 December 1999 相似文献