共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Amit Katiyar Lei Ji Panagiotis G. Smirniotis Neville G. Pinto 《Microporous and mesoporous materials》2005,80(1-3):311-320
The adsorption of Bovine Serum Albumin (BSA) and lysozyme on MCM-41 was studied. In particular, characteristics important to the use of this adsorbent as a chromatographic support for protein separations have been examined. These include the effects of external surface area, solution conditions (pH), and rate of adsorption. Comparative studies were performed on MCM-41 of three pore sizes (24.8 Å, 36 Å, 53.5 Å). It has been shown that differences in external surface area can strongly influence the adsorption capacity. This implies that adsorption on the external surface can be misinterpreted as adsorption in the pores of MCM-41. Thus, high adsorption capacities may not necessarily mean high molecular-sieving capacities. This paper also reports a dependence of protein uptake rates on solution conditions. Calorimetry suggests that under certain solution conditions the adsorption of BSA is a combination of two sequential energetic events. These are postulated to be BSA adsorption followed by reorientation/reconformation of the adsorbed protein on the surface. The slow second step affects the attainment of equilibrium. 相似文献
3.
K. Vidya S. E. Dapurkar P. Selvam S. K. Badamali N. M. Gupta 《Microporous and mesoporous materials》2001,50(2-3):173-179
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. 相似文献
4.
H.I. Meléndez-Ortiz L.A. García-CerdaY. Olivares-Maldonado G. CastruitaJ.A. Mercado-Silva Y.A. Perera-Mercado 《Ceramics International》2012
A rapid and facile synthesis route to obtain mesoporous MCM-41 silica at room temperature under basic conditions using as template cetyltrimethylammonium bromide (CTAB) is reported. The synthesis variables such as reaction time, molar ratios of CTAB/TEOS and H2O/ethanol in the initial gel composition were studied. Samples were characterized by X-ray diffraction, nitrogen adsorption–desorption analyses, scanning electron microscopy and transmission electron microscopy. It was found that reaction conditions affect the quality of the MCM-41 silica. This silica can be prepared at short periods of time, and it exhibited a uniform size and spherical morphology. 相似文献
5.
Effect of pH in aqueous media used in the hydrothermal treatment of as-synthesized MCM-41 on the structure and the wetting
stability of the resulting materials was studied using XRD, TG-DTA and N2 adsorption. The long-range structural order and the wetting stability of the mesoporous MCM-41 were improved through hydrothermal
treatment of as-synthesized sample at around pH 7 without salt addition. The pH adjustment of aqueous media toward neutral
is thought to shift the polymerization equilibrium of silica species around external surface of the micelles to a higher degree
of condensation, and to reduce the electrostatic repulsion between the silicate–micelle composites. This leads to the further
formation of Si–O–Si network within the silica walls of the mesoporous materials, resulting in the enhancement of the structural
stability of MCM-41 samples. 相似文献
6.
7.
8.
Izabela SobczakMaria Ziolek Elena Pérez-MayoralDavinia Blasco-Jiménez Antonio J. López-PeinadoRosa M. Martín-Aranda 《Catalysis Today》2012,179(1):159-163
Design of base catalyst featuring large mesoporous surfaces allows performing base-catalysed reactions in the fields of production of perfumes. Post-synthesis grafting of organotrialkoxysilanes has effectively been applied to incorporate active organic functional groups onto the mesoporous silica surfaces. The novelty of our study is the use of mesoporous materials with different chemical compositions: silicate (MCM-41), aluminosilicate (AlMCM-41; Si/Al = 64) and niobosilicate (NbMCM-41; Si/Nb = 64) and consequently, different acidity, as supports for three aminopropylalkoxysilanes (APMS), [3-(2-aminoethylamino) propyl]trimethoxysilane (2APMS) and 3-[2-(2-aminoethylamino) ethylamino]propyltrimethoxysilane (3APMS). Isomerization of safrole to the corresponding thermodynamically stable isosafrole has been carried out on these amino-grafted MCM-41 materials. Maximum conversion of around 85% with a cis/trans ratio of 1/9 at 433 K in DMF as solvent was obtained. Isomerization is strongly dependent on the nature of the support and changed in the following order: APMS/AlMCM-41 > APMS/NbMCM-41 ? APMS/MCM-41. The nature of the amine chain is also responsible of the activity. The order of activity is APMS/AlMCM-41 > 2APMS/AlMCM-41 > 3APMS/AlMCM-41. 相似文献
9.
10.
Buğçe Aydemir 《Chemical Engineering Communications》2016,203(5):635-641
Aluminum-containing MCM-41 catalysts were synthesized in this study by impregnation of aluminum into hydrothermally synthesized MCM-41. Aluminum was loaded into the porous framework of silica with different Al/Si ratios, using aluminum isopropoxide as the aluminum source. These catalysts exhibited Type IV adsorption–desorption isotherms and had a pore diameter of 2.4 nm. Aluminum species were coordinated tetra- and octahedrally in the structure of catalysts. Diffuse Reflectance Fourier Transform Infrared Spectra (DRIFTS) analysis of the pyridine-adsorbed catalysts revealed the existence of Brönsted acid sites in the synthesized catalysts in addition to the Lewis acid sites. The performance of these catalysts was tested in the degradation of polyethylene using a thermogravimetric analyzer. Pure MCM-41 did not show a significant reduction in the degradation temperature of polyethylene, whereas aluminum-impregnated catalysts were successful in decreasing the temperature. 相似文献
11.
12.
13.
14.
The synthesis of MCM-41 mesoporous compounds with Si/Al ratios as low as 2 without observing the presence of octahedral Al in27AlMAS NMR is reported. FTIR spectra of chemisorbed pyridine indicated that MCM-41 materials in their protonated form exhibit both Brønsted and Lewis acid sites. 相似文献
15.
以粉煤灰为初始原料,十六烷基三甲基溴化铵(CTAB)为模板剂采用水热法合成出中孔分子筛MCM-41,采用小角XRD、TEM、氮气吸附-脱附等对样品的物相、比表面积、孔径、孔体积等进行表征,并研究了样品分子筛对镍离子的吸附性能。结果表明:样品具有典型中孔分子筛MCM-41的特性,比表面积为576 m^2/g,平均孔径为5.53 nm;Ni^2+能定量吸附在样品分子筛上,最大去除率可达到96%,吸附性能符合Langmuir吸附方程特征,并且随吸附液pH的增大,Ni^2+去除率也随之增加。 相似文献
16.
含铁MCM-41的合成与表征 总被引:1,自引:0,他引:1
实验采用液相沉积方式,向MCM-41有序介孔微球的介孔中引入铁盐,通过加热使铁盐分解,铁以氧化物纳米颗粒或Fe-O纳米团簇的形式存在于有序介孔微球的介孔中,从而获得含铁MCM-41有序介孔微球.对不同铁含量的MCM-41进行了比较性表征,并研究了不同铁源对含铁MCM-41合成的影响.研究表明,以Fe(acac)3的甲苯溶液和Fe(NO3)3的水溶液为铁源时,所得试样中铁的含量均随铁离子浓度的增大而增大.铁离子浓度相同时,由前者所得试样的载铁量是后者的3~4倍,最大铁负载量达1 mmol8226;g-1.载铁后,有序介孔微球的比表面积、孔容和孔径均减小.以Fe(NO3)3的水溶液为铁源时,载铁前驱体试样煅烧后,MCM-41的硅氧骨架发生收缩,而以Fe(acac)3的甲苯溶液为铁源时,MCM-41的硅氧骨架未见变化.因此,从载铁量及负载过程对有序介孔材料骨架结构的影响看,Fe(acac)3的甲苯溶液作为铁源用于合成含铁MCM-41优于Fe(NO3)3的水溶液. 相似文献
17.
Sulfated zirconia (SZ) was supported on mesoporous molecular sieves MCM-41 by impregnation of zirconium sulfate followed by calcination. The nanochannels of MCM-41 provide a large surface area for the solid state dispersion of zirconium sulfate and a steric restriction on formation of zirconia nanoparticles. The catalysts were tested in n-butane isomerization. With the addition of a proper amount of alumina as a promoter, denoted as ASZ/MCM-41, the catalytic activity was dramatically improved in comparison to the activities of SZ/MCM-41. The increase of activity was determined primarily by the amount of aluminum added and the temperature of calcination. The SZ/MCM-41 catalysts were characterized by X-ray diffraction (XRD), high resolution TEM (HR-TEM), NH3 adsorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption (EXAFS). In particular, the Zr K-edge EXAFS data give one a measure of the degree of dispersion of zirconia on the surface of MCM-41. The trend of the promotion effects of alumina on SZ in butane isomerization is not monotonic; there is an optimum level of Al-loading for high activity. It is explained based on three quantitative factors: increased sulfur loadings, balanced distribution of Lewis and Brønsted acid sites, and higher dispersion of zirconia. 相似文献
18.
Takashi Tatsumi Keiko A. Koyano Yoshinori Tanaka Shinichi Nakata 《Journal of Porous Materials》1999,6(1):13-17
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. 相似文献
19.
Soledad G. AspromonteÁlvaro Sastre Alicia V. Boix María J. CoceroEsther Alonso 《Microporous and mesoporous materials》2012,148(1):53-61
CoO and Co3O4 nanoparticles were uniformly dispersed inside mesoporous MCM-41 and Al-MCM-41 supports using supercritical CO2 reactive deposition. This method represents a one-pot reproducible procedure that allows the dissolution of the organocobalt precursor and supports impregnation in supercritical CO2 at 70 °C and 110 bar, followed by the precursor thermal decomposition into cobalt species at 200 °C and 160 bar. By the relative concentration of the cobalt precursor [cobalt (II) bis (η5-ciclopentadienil)], the load of cobalt nanoparticles was controlled and then determined by Inductively Coupled Plasma (ICP-OES). The synthesis of CoO and Co3O4 species inside the MCM-41 and Al-MCM-41 substrates was confirmed by X-ray Photoelectron (XPS) and Laser Raman Spectroscopies (LRS). By N2 adsorption and Small Angle X-ray Scattering (SAXS), it was determined that the hexagonal arrangement as well as the surface area and pore size of the substrates changed after the addition of cobalt. By means of X-ray mapping from SEM images, a homogeneous distribution of cobalt nanoparticles was observed inside the mesopores when the cobalt loading was 1 wt.%. In addition, spherical cobalt nanoparticles of average diameter close to 20 nm were detected on the outer surface of MCM-41 and Al-MCM-41 supports when the cobalt content was higher. On the other hand, by Transmission Electron Microscopy (TEM), it was possible to measure the interplanar distance of the crystalline plane of the outer nanoparticles, which was later compared with the theoretical distance values which allowed identifying the CoO and Co3O4 phases. 相似文献
20.
通过浸渍法将5种咔唑类荧光分子负载于介孔材料MCM-41上,制备有机-无机杂化复合荧光材料,并对咔唑荧光分子和杂化复合材料的表面结构、紫外-可见吸收、荧光发射等性质进行了对比。结果表明,负载后的咔唑类荧光分子分散于MCM-41孔道上,材料热稳定性提高,在100~350℃内没有明显失重,其紫外吸收和荧光发射也发生明显蓝移(λmaxabs=331~368 nm,λmaxem=401~435 nm)。制备的杂化复合材料可用作蓝色荧光材料(λmaxem=401~435 nm)。 相似文献