表面活性剂性能对MCM-41中孔分子筛稳定性的影响

通过对各种表面活性剂、不同环境的表面活性剂以及几种表面活性剂混合使用对提高MCM-41中孔材料水热稳定性影响的介绍，提出了表面活性剂的性能直接影响MCM-41分子筛的稳定性和特性，新的表面活性剂的开发和应用是改善MCM-41性能的重要途径之一；MCM-41无定型孔壁的晶化是解决目前中孔材料的根本措施之一；表面活性剂周边环境的调常和改性以及不同性能的表面活性剂同时利用，对提高MCM-41的水热稳定性有明显的作用。一种新的具有相当水热稳定性的中微孔材料也在文中报道。     

微结构单元提高介孔MCM-41分子筛水热稳定性的研究进展

综述了微结构单元提高介孔MCM-41分子筛水热稳定性的主要合成方法和研究现状,系统分析了不同微结构单元对介孔分子筛MCM-41水热稳定性的影响规律,探讨了微结构单元与介孔分子筛水热稳定性之间的关联度,阐释了微结构单元合成镶嵌结构或核壳结构的高水热稳定性介孔分子筛的机理,最后展望了高水热稳定性介孔分子筛的应用前景。     

提高中孔分子筛水热稳定性技术研究进展

综述了近年来提出的各种提高中孔分子筛水热稳定性的方法，分析比较了各种方法的特点和存在的问题，指出用硅铝纳米簇进行自组装以及选用适合高温合成的模板体系将是今后的发展方向。     

MCM-48中孔分子筛的合成

在文献报道的水热法合成MCM 48中孔分子筛的基础上,针对在不同时期合成MCM 48合成重复性不好的问题,系统地考察了滴加正硅酸乙酯(TEOS)时溶液的温度,发现在溶液温度为20℃时滴加TEOS时配制的合成液能合成出有序性较高的MCM 48,并考察了焙烧温度及气氛对合成MCM 48中孔分子筛的影响,通过XRD、TG/DSC等对合成的产物进行了表征。     

MCM-41介孔分子筛改性研究新进展

针对目前研制的MCM-41介孔分子筛因水热稳定性较差、孔径过小、难以用于重油加工等方面的缺陷,综述了国内外对MCM-41介孔分子筛改性研究的新进展,尤其是扩大分子筛孔径、提高水热稳定性、引入杂原子和后处理等方面的最新研究。     

MCM-41介孔分子筛研究进展

介绍了介孔材料的定义,总结了MCM-41介孔分子筛的合成方法,针对其目前存在的孔径较小及酸性较小的缺点,综述了国内外对MCM-41介孔分子筛的孔径扩大分的最新研究进展。     

介孔MCM—41分子筛水热稳定性的研究进展

综述了近年来关于各种增强介孔MCM-41分子筛水热稳定性的方法,分析比较了各种方法的特点,阐释了各种方法的作用机理,最后指出了提高分子筛水热稳定性的发展前景.     

介孔分子筛MCM-48对果胶酶吸附研究

利用水热合成法制备得到纳米介孔分子筛MCM-48,并研究了其对果胶酶的吸附固载性能和吸附条件及过程特点,测定了固载果胶酶的活性。动力学研究表明,MCM-48与果胶酶间的吸附符合准二阶动力学方程。热力学计算表明,该吸附过程ΔH=-68.94kJ/mol,ΔS=-197.90J·mol~(-1)·K~(-1),说明MCM-48对于果胶酶的吸附是一个放热的、熵减的吸附过程。通过对比游离酶(酶活力14 569U)和固定化果胶酶(酶活力13 345U)的酶活力,说明固载在MCM-48中的果胶酶依然具有良好的活性,这对于保持果胶酶的天然结构以及生物活性非常有益。     

MCM-41-HY介孔-微孔复合分子筛的水热合成

以微孔分子筛HY浆液为母液,合成介孔-微孔复合分子筛MCM-41-HY。通过XRD、NH_3-TPD和N_2吸附-脱附等手段对复合材料进行了表征,并对复合分子筛的水热稳定性进行了考察。结果表明,复合分子筛MCM-41-HY具有中孔分子筛MCM-41和微孔HY型沸石的特点,并且与纯MCM-41分子筛相比,复合分子筛的酸强度明显增强,水热稳定性提高。     

MCM-41介孔分子筛改性研究进展

介绍了有序介孔材料的定义和分类,MCM-41介孔分子筛、合成方法和形成机理,针对其MCM-41目前存在的一些问题,综述了国内外对MCM-41介孔分子筛最新的改性研究进展。     

纯硅MCM-48介孔材料的快速合成及其表征

以氨水作为催化剂,用一种快速简便的方法制备了MCM-48型介孔分子筛,产品用粉末X衍射、透射电镜、低温氮气吸附—脱附和傅立叶变换红外光谱等进行来表征。结果表明所制备材料具有高的比表面积(S_(BET)=1729m~2/g),大的孔容量(Vp=1.06cm~3/g),孔径大小为2.4nm,排列整齐。并研究了不同合成条件对产品结构的影响。     

Ni-PMo_(12)/MCM-48催化剂的制备与催化性能研究

通过水热合成法制备了中孔分子筛MCM-48,并采用等体积浸溃法负载活性组分镍(Ni)和磷钼酸(PMo12).采用XRD、BET吸附、红外吡啶吸附等方法对催化剂进行表征.考察了反应温度、还原温度和还原时间对异构化催化性能的影响及催化性能随反应时间的变化.结果表明,w(Ni)=3%-w(PMo12)=30%/MCM-48对正庚烷异构化反应具有较好的异构化性能,当还原温度400℃、反应温度300℃时,催化剂催化性能最好,转化率为14.2%时,异构化选择性能够达到65.6%.     

Mechanical Stability of Mesoporous Materials, MCM-48 and MCM-41

The structural collapse of mesoporous molecular sieves, MCM-48 and MCM-41 materials by mechanical compression was found to occur mechanochemically through hydrolysis of Si–O–Si bonds. Their ordered structures were retained by compressing the well-dried samples under dry N2. Trimethylsilylation of mesoporous materials proved effective in eliminating their instability to compression through enhancing hydrophobicity.     

Application of mesoporous MCM-48 and SBA-15 materials for the separation of biochemicals dissolved in aqueous solution

The application of molecular sieves for the separation and purification of biological molecules has been limited because of their available pore size (>1.3 nm). With the development of synthetic mesoporous materials, the available pore size range (1.5-10 nm) has been extended. They have pores large enough to allow access for a number of biological molecules. This work investigated the use of two mesoporous materials (MCM-48 and SBA-15) with different pore sizes and structures for adsorption of cephalosporin C as a model compound of biological molecules in terms of ethanol concentration, solution pH, and temperature. It was found that these materials have the potential for the separation and purification processes of biochemicals including antibiotics, amino acids, and proteins.     

The entrapment of UO2 in mesoporous MCM-41 and MCM-48 molecular sieves

A method based on direct template-ion-exchange was employed for the entrapment of UO₂²⁺ ions in MCM-41 and MCM-48 molecular sieves via swapping of cetyltrimethylammonium cations present in the mesoporous channels by the UO₂²⁺ ions in an aqueous solution. The samples were characterized by XRD, FT-IR, and ICP-AES techniques. The entrapment of UO₂²⁺ ions is facilitated by the large pore size vis-a-vis the high surfactant content in the as-synthesized host materials. A higher loading of UO₂²⁺ ions was achieved in MCM-48 as compared to MCM-41, which could be attributed to its three-dimensional pore system and higher surfactant-to-silica ratio. FT-IR results provide an evidence of a strong binding of UO₂²⁺ groups with the defect silica sites of mesoporous molecular sieves.     

Synthesis of Amine-Functionalized MCM-41 and MCM-48 for Removal of Heavy Metal Ions from Aqueous Solutions

In this research amino functional mesoporous MCM-41 and MCM-48 materials were prepared in an attempt to develop efficient adsorbents for removal of heavy metals from aqueous solutions. The adsorbents were characterized by XRD, FTIR, and TG-DTG techniques. The synthesized adsorbents were used for the removal of Cu(II), Co(II), Cd(II), and Pb(II) from aqueous solutions for the first time, and the influence of some effective parameters including concentration, initial pH, contact time, and temperature on the sorption process was studied and optimized. Significant adsorption capacities were obtained at low concentrations. The kinetic studies showed that the adsorption process was fast and more than 90% of equilibrium capacity was achieved within 60 min. Experimental kinetic data was well fitted with the pseudo-second-order kinetic model. Thermodynamic parameters computed from the experimental data showed that the adsorption was endothermic and spontaneous.     

Preparation of Titanium Oxide Supported MCM-48 by the Designed Dispersion of Titanylacetylacetonate

Titaniumoxide supported MCM-48 was prepared by a novel synthesis method, utilizing titanylacetyl-acetonate as the Ti source. The process consists of an adsorption and subsequent thermolysis of the Ti-complex. The interaction of the complex with the surface was studied by FTIR, TGA and chemical analysis. Further characterization was done by XRD, Raman, UV-DR and N₂ adsorption measurements. The Ti-complex is irreversibly adsorbed on the MCM-48 surface by a hydrogen bonding mechanism independent of the Ti loading. During calcination, the supported TiO(acac)₂ complex is converted towards supported titaniumoxide, whereby the Ti atoms are partly incorporated into the pore walls of MCM-48. The adsorption of TiO(acac)₂ is an efficient way to create supported titaniumoxides with a high surface area.     

Influence of the reaction conditions on the thermal stability of mesoporous MCM-48 silica obtained at room temperature

The thermal stability of MCM-48 silicas synthesized at room temperature under basic conditions using cetyltrimethylammonium bromide (CTAB) as template was evaluated as a function of the reaction time, CTAB/TEOS and H₂O/ethanol molar ratios and ammonium hydroxide (NH₄OH) concentration in the initial gel composition. Samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analyses, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that synthesis conditions affect the structural and thermal properties of the MCM-48 silicas. These silicas exhibited a size from 200 to 500 nm with spherical morphology.     

MCM-48分子筛催化剂上正庚烷的临氢异构化

制备了Ni-PMo₁₂/MCM-48中孔分子筛催化剂并用于正庚烷异构化反应研究。采用XRD、BET吸附、红外吡啶吸附等方法对催化剂进行表征。研究了反应温度、还原温度、 还原时间和还原氢气流速对异构化催化性能的影响,并考察了催化性能随时间的变化。结果表明,当镍（Ni）和磷钼酸（PMo）质量分数分别为3%和30%、Ni-PMo/MCM-48对正庚烷异构化反应具有较好的异构化性能,还原温度400℃、还原4h、氢气流速为30 mL/min、反应温度300 ℃时,催化剂性能最好,转化率为14.2%时,异构化选择性达到65.6%。