共查询到20条相似文献,搜索用时 15 毫秒
1.
Yong Jin Pingjun Wang Donghong Yin Jianfu Liu Huayu Qiu Ningya Yu 《Microporous and mesoporous materials》2008,111(1-3):569-576
The stabilization of gold nanoparticles (GNPs) by disulfide groups linked to imidazolium chloride units in a periodic mesoporous organosilica of SBA-15 and their catalytic performances in the epoxidation of styrene were investigated. The mesoporous organosilica (PMO-SBA-15) was synthesized via a one-pot condensation process involving the assembly of ionic liquid silsesquioxane organic precursor containing disulfide group and tetraethoxysilane (TEOS) in the presence of P123 (EO20PO70EO20). Aqueous chloroaurate ions were in situ reduced by the silanol groups presented on the channel surface of the mesoporous organosilica to form GNPs that were subsequently captured by disulfide group to obtain Au-containing mesoporous organosilica (Au-PMO-SBA-15). The PMO-SBA-15 and Au-PMO-SBA-15 were characterized by XRD, 29Si MAS-NMR, FT-IR, UV–vis, TEM and N2 adsorption–desorption measurements. It was found that both PMO-SBA-15 and Au-PMO-SBA-15 had the typical characteristics of mesoporous SBA-15, and that the GNPs entrapped into the channels of Au-PMO-SBA-15 possessed mean size of ca. 1.8 nm. The Au-PMO-SBA-15 was used as a catalyst in the epoxidation of styrene. 95% of styrene conversion and 75% of selectivity to styrene epoxide were obtained over the novel Au-PMO-SBA-15 catalyst, which were higher than that over the reported nano-Au catalysts. Furthermore, the Au-PMO-SBA-15 could be conveniently recovered for recycled use without significant loss of catalytic activity and selectivity. 相似文献
2.
Mesoporous GaSBA-15 molecular sieves with different nSi/nGa ratios have been directly synthesized using Pluronic 123 triblock polymer as a structure-directing agent by pH-adjusting method. The mesoporous materials have been characterized using ICP-AES, XRD, N2 adsorption, 71Ga-MAS NMR, SEM and TEM. ICP-AES studies show a high amount of gallium incorporation on the silica pore walls. The structural and textural properties of calcined GaSBA-15 are characterized by XRD and N2 adsorption. 71Ga MAS NMR results demonstrate that a high amount of tetrahedral-gallium could be substituted for Si in the framework of SBA-15. TEM and FE-SEM images show the uniform pore diameter and rope-like hexagonal mesoporous structure of GaSBA-15. These GaSBA-15 materials have been used as catalysts for vapour-phase t-butylation of 1,2-dihydroxybenzene (DHB) for selective synthesis of 4-t-butylcatechol (4-TBC) under different reaction conditions. GaSBA-15(10) gave the highest 93.2% conversion of DHB and 95.7% selectivity of 4-TBC as compared with other GaSBA-15 catalysts. 相似文献
3.
A. Vinu Dhanashri P. Sawant K. Ariga M. Hartmann S.B. Halligudi 《Microporous and mesoporous materials》2005,80(1-3):195-203
Aluminum-containing mesoporous molecular sieves AlSBA-15 with different nSi/nAl ratios and AlMCM-41 have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. XRD, N2 adsorption and 27Al NMR spectroscopy. The low angle XRD and N2 adsorption measurements reveal that the structural order of SBA-15 was retained after the incorporation of Al. The increase of the unit cell parameter with increasing aluminum content and 27Al MAS NMR spectroscopy confirm the incorporation of aluminum in the framework. Benzylation of benzene and substituted benzenes reaction employing benzyl chloride as the alkylating agent over AlSBA-15 and AlMCM-41 have been investigated. The influence of various reaction parameters such as reaction temperature, reactant feed ratio and catalyst amount affecting the activity and selectivity of AlSBA-15, have been studied. Among the mesoporous catalysts studied, AlSBA-15(45), where the number in parentheses indicates the molar nSi/nAl ratio, shows both high conversion and high selectivity for the benzylation of benzene. The activity of this catalyst for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > mesitylene > anisole. Kinetics of the benzene benzylation over different catalysts have also been investigated. 相似文献
4.
Govindasamy Chandrasekar Kwang-Seok You Ji-Whan Ahn Wha-Seung Ahn 《Microporous and mesoporous materials》2008,111(1-3):455-462
An alkali fusion method was adopted to extract silicate species from coal bottom ash in a power plant and the supernatant solution was used for the synthesis of MCM-41, SBA-15, and SBA-16 mesoporous silica materials. The minor impurities present in the bottom ash were not found to be detrimental to the successful formation of mesoporous silica phases. Additional silica from sodium metasilicate was introduced to improve the textural properties for SBA-15 and SBA-16. According to SEM analyses, particle morphology of the samples gradually approaches those prepared using pure chemical as the amount of external silica source increases. XRD analyses confirmed well-ordered mesostructures in all of these silica materials. N2 adsorption–desorption isotherms of MCM-41 prepared using bottom ash showed a type IV isotherm with a region of steep increase due to capillary condensation, whilst SBA-15 and SBA-16 showed type IV isotherm with H1 and H2 hysteresis loops, respectively. 27Al MAS NMR analysis of MCM-41 synthesized from the supernatant solution reveals that the extracted Al species from bottom ash were tetrahedrally incorporated in the framework. TEM clearly showed the uniform pore structure of the materials prepared using the industrial waste. 相似文献
5.
New and ordered 2D-hexagonal (p6mm) mesoporous aluminosilicates (CMI-11) have been synthesized in strongly alkaline media using aluminosilicate ester ((BusO)2-Al-O-Si-(OEt)3) as single-source molecular precursor and CTMABr as surfactant and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption and 27Al and 29Si MAS NMR spectroscopy. These mesoproous aluminosilicates exhibit a very low Si/Al ratio of 1.9 and highly thermal stable tetrahedral aluminum sites in the mesoporous walls. 27Al and 29Si MAS NMR spectroscopy indicates that the pore walls of CMI-11 are fully condensed with molecular homogeneity of Si–O–Al linkage. These materials are highly important in catalysis, in particular for the petroleum processing and the bulky molecules treatment. 相似文献
6.
Mesoporous silica SBA-15 was prepared and loaded with Pt using the deposition–precipitation method (DP). The Pt loaded material was characterized by N2 sorption, and X-ray diffraction (XRD) at low scattering angles as well as XRD at wide angles, in order to monitor the impact of the metal deposition pathway on the mesoporous texture. After DP the material contains ordered mesoporous silica as well as a fraction appearing as non-ordered amorphous silica. This is most likely caused by the hydrothermal treatment involved in the DP. The material was also characterized using NIR and 29Si MAS NMR spectroscopy. The NIR results of the calcined materials indicate that the silanol groups of SBA-15 may act as anchoring groups for the metallic Pt particles. The NMR spectroscopy data shows that the Pt/SBA-15 sample prepared by the DP method posseses a better short-range regularity of SBA-15 walls as compared to the parent SBA-15. This is suggested to be caused by dissolution and possible re-precipitation of siliceous species. 相似文献
7.
S. Perathoner P. Lanzafame R. Passalacqua G. Centi R. Schlgl D.S. Su 《Microporous and mesoporous materials》2006,90(1-3):347-361
SBA15–TiO2 samples prepared by introducing titanium with a grafting method and having TiO2 loadings below 15 wt.% have been characterized by XRF, XRD, IR, porosimetry, SEM, HRTEM, and UV–Visible diffuse reflectance. Differently from the samples reported in the literature characterized by a high TiO2 loading, no evidences have been found for the presence of titania particles inside or outside the mesopores of SBA-15. Three different titanium species were instead evidenced to be present. The first two derive from the reaction of titanium with silanol groups in the corona area of inner SBA-15 walls leading to the formation of either TiO4 tetrahedral sites (by reaction by hydroxyl nests of surface defect sites) and/or pseudo-octahedral surface sites anchored by two (or more) Si or Ti ions through bridging oxygens. The third species derives from the reaction of titanium in the regions with high sylanol density, e.g. in the micropores located in the corona of SBA-15 channels, leading to the formation of TiO2-like nanoareas (probably Si-doped) with dimensions of around 1–2 nm maximum. The potential interest of these materials as photocatalysts, for the presence of a TiO2-like nanoareas highly accessible by reactants, is discussed. 相似文献
8.
采用溶剂法和焙烧法制备了SBA-15和MCM-41两类介孔氧化硅,并以此为载体制备固载型三氟甲基磺酸镱(Yb(OTf)3)催化剂。通过小角X射线衍射(SAXD)、氮气吸附/脱附、29Si固体核磁共振光谱(NMR)、透射电子显微镜(TEM)及热重分析(TG)等方法对载体及催化剂进行表征,研究其在葡萄糖制备乳酸反应中的催化性能。结果表明:溶剂法制备的氧化硅表面羟基含量比焙烧法高,负载的磺酸基团和三氟甲基磺酸镱都更多,催化活性更高;SBA-15的平均孔径比MCM-41的大3 nm左右,这使得SBA-15具有更好的传质性能以及Yb(OTf)2-SBA-15具有更好的催化性能。以Yb(OTf)2-SBA-15-S为催化剂,在2 MPa N2压力、190 ℃下反应60 min,乳酸的收率达到42.35%。 相似文献
9.
10.
The production of Ph3Sn–O–SBA-15 (Ph3SnSBA) was achieved by heating triphenyltin chloride and SBA-15 in N-methylpyrrolidone at 190 °C for 5 h using triethylamine as a catalyst. The composition, structure, and sur-face physical and chemical properties of Ph3SnSBA were characterized using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), 13C, 119Sn and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy in situ pyridine infrared spectroscopy (Py-IR), N2 adsorption–desorption isotherms, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results of ICP-AES and organic elemental analysis showed that the grafting yield of Sn was 17%(by mass) for Ph3SnSBA. The elemental analysis and solid-state NMR results for Ph3SnSBA were consistent with grafting of triphenyltin on SBA-15. The N2 adsorption–desorption, XRD and TEM analyses showed that Ph3SnSBA retained an ordered hexagonal mesoporous structure, resulting in decreases in the surface area, pore size and mesopore volume, and an increase in acidity as compared with SBA-15. The Hammett acidity function (H0) value and the number of acid sites for Ph3SnSBA, obtained by the Hammett methods, were 2.77–3.30 and 2.07 mmol·g?1, respectively. The Friedel–Crafts acylation of toluene and acetic anhydride over Ph3SnSBA was investigated. The yield of methylacetophenone (MAP) and the selectivity for 4-methylacetophenone (PMAP) were 79.56%and 97.12%, respectively, when the conditions were n (toluene):n (anhydride)=2.0:1.0 with 6%(by mass) catalyst, and heating under reflux for 5 h. The PMAP selectivity stil reached 93.11%when Ph3SnSBA was used for the fifth time under the same reaction conditions. 相似文献
11.
The phosphoric acid groups has been successfully grafted on the surface of mesoporous molecular sieve SBA-15 to form a solid acid catalyst P-SBA-15 by post-synthesis method. The samples were characterized by means of XRD, FT-IR, SEM, TEM, 31P MAS NMR, NH3-TPD, N2 adsorption/desorption and the esterification reaction. The XRD and N2 adsorption/desorption results indicate that P-SBA-15 catalyst keeps the 2D hexagonal mesoporous structure and opens channels with the lower surface area of 554.35?m2/g compared with that of SBA-15. The SEM and TEM results show that the figuration of P-SBA-15 behaves ??rod-like?? and phosphoric acid groups is scattered differently on the surface of P-SBA-15. The FT-IR and 31P MAS NMR results display that phosphorus species graft onto the surface of SBA-15, which provide the Br?nsted acid sites on the surface of P-SBA-15. The acidity of the generated Br?nsted acid sites on P-SBA-15 significantly is verified by NH3-TPD. The esterification reaction results shows that catalytic activity of P-SBA-15 is enhanced significantly compared with that of SBA-15, and its stability is good. 相似文献
12.
Xiaoyu Wang Pan Wang Zihao Dong Zhengping Dong Zongyan Ma Jian Jiang Rong Li Jiantai Ma 《Nanoscale research letters》2010,5(9):1468-1473
An inorganic–organic hybrid fluorescence chemosensor (DA/SBA-15) was prepared by covalent immobilization of a dansylamide
derivative into the channels of mesoporous silica material SBA-15 via (3-aminopropyl)triethoxysilane (APTES) groups. The primary
hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. Fluorescence characterization
shows that the obtained inorganic–organic hybrid composite is highly selective and sensitive to Hg2+ detection, suggesting the possibility for real-time qualitative or quantitative detection of Hg2+ and the convenience for potential application in toxicology and environmental science. 相似文献
13.
After PAMAM (polyamidoamine) dendrimers have been successfully grown in SBA-15 mesoporous materials, Wilkinson's catalyst (RhCl(PPh3)3) precursor has been tethered on these dendritic supports to produce heterogeneous catalysts for hydroformylation reaction of styrene. SBA-15 has been functionalized by two methods. In the passivation method, the silanols outside the SBA-15 pores have been passivated to preclude the rhodium precursor to be tethered outside the channels. The rhodium catalysts supported in the pore channels of this passivated SBA-15 show positive dendritic effects in enhancing the catalytic activity, regio-selectivity and stability of the catalyst by minimizing the leaching of the rhodium complex catalyst from the catalyst support to the liquid-phase media. 相似文献
14.
Yinfeng Zhao Yue Qi Yingxu Wei Yangyang Zhang Shigang Zhang Yue Yang Zhongmin Liu 《Microporous and mesoporous materials》2008,111(1-3):300-306
Nitrided mesoporous silica was used as a host for accommodating nano-silver into the channels. The nitridation of the mesoporous silica host, i.e. SBA-15, with ammonia caused the generation of –NHx groups on the surface. The following impregnation of the nitrided SBA-15 with aqueous AgNO3 solution and further reduction led to formation of silver nanostructures in the channels. The samples were characterized by FTIR, XRD, TEM and XPS techniques. The impregnation time has effect on the morphology of the resulting nanostructures. The interaction between silver species and surface –NHx was the key to immobilize Ag in the channels. A scheme was proposed to illustrate the synthesis of Ag nanostructures using nitrided mesoporous host. 相似文献
15.
Hsien-Ming Kao Tzu-Yi Shen Jyun-Da Wu Lung-Ping Lee 《Microporous and mesoporous materials》2008,110(2-3):461-471
Well-ordered cubic mesoporous silicas SBA-1 functionalized with thiol groups have been synthesized via co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) templated by cetyltriethylammonium bromide (CTEABr) under strongly acidic conditions. Various synthesis parameters such as HCl concentration, synthesis temperature, and time for hydrothermal treatment were systematically investigated as a function of MPTMS contents. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), solid-state 13C and 29Si NMR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and nitrogen sorption measurements. Direct evidence of the presence of chemically attached thiol moieties was provided by solid-state 29Si and 13C NMR spectroscopy. A high degree of structural ordering was still retained when MPTMS loading was incorporated up to 20 mol% in the synthesis mixture. Increasing the synthesis temperature and the time for the hydrothermal treatment not only increased the degree of framework cross-linking, but also did not lead to the undesirable phase transformation as often observed in the conventional synthesis of pure silica SBA-1. SEM results reveal that the morphology of thiol-functionalized SBA-1 depends on the HCl concentration used in the synthesis. The sample prepared with a low acid concentration exhibits a highly isotropic morphology with more facets than that of pure silica SBA-1, whereas it changes to a spherical shape as the acid concentration is increased. The maximum content of the attached thiol group (–SH) in the mesoporous framework is 2.39 mmol/g. The thiol-functionalized SBA-1 mesoporous materials are efficient Hg2+ adsorbents. 相似文献
16.
Manuel Baca Emmanuel de la Rochefoucauld Emmanuelle Ambroise Jean-Marc Krafft Redouane Hajjar Pascal P. Man Xavier Carrier Juliette Blanchard 《Microporous and mesoporous materials》2008,110(2-3):232-241
Mesoporous aluminas of controlled pore sizes were synthesized by multiple grafting of Al isopropoxide in organic solvents on mesoporous silica SBA-15. These materials were characterized by N2 physisorption, TEM, XRD, 27Al NMR and their surface chemical properties were probed by DRIFT, cumene cracking and MoO3 thermal spreading. The results show that the chemical nature of the Al-grafted materials varies continuously with the number of grafting from pure silica to pure alumina. Typically, after three graftings, this original method of synthesis allows one to prepare ordered mesoporous aluminas with specific surface areas above 300 m2 g−1 and a narrow pore size distribution centered on ca. 60 Å. In addition to the characterizations, different models were developed to understand the evolution of the specific surface area and to discard a possible pore blocking. 相似文献
17.
High-surface area and well-ordered mesoporous Cr-incorporated SBA-15 (Cr-SBA-15) and SBA-15-supported chromia (CrOx/SBA-15) with Cr surface density = 0.05–1.11 Cr-atom/nm2 have been prepared, respectively, using the one-step synthesis and incipient wetness impregnation method, and characterized by AAS, XRD, BET, ESEM, TEM, XPS, laser Raman, UV-Vis, FT-IR, and H2-TPR. It is observed that the Cr-SBA-15 and CrOx/SBA-15 samples showed an evolution of surface morphology from long chain-shaped to short rod-like and further to an irregularly spherical architecture at elevated Cr content, which might arise from the interaction of Cr ions or CrOx domains with SBA-15. There were co-presence of tetrahedrally coordinated mono- and poly-chromate (Cr6+) as well as octahedrally coordinated Cr3+ species in Cr-SBA-15 and CrOx/SBA-15, with the Cr6+ species being dominant at Cr surface density ≤0.22 Cr-atom/nm2 in Cr-SBA-15 and Cr ≤0.54 Cr-atom/nm2 in CrOx/SBA-15, whereas the amount of the Cr3+ species increased markedly at Cr surface density ≥0.53 Cr-atom/nm2 due to the formation of crystal Cr2O3 phase. Maximal Cr incorporation into Cr-SBA-15 and one monolayer surface CrOx coverage on CrOx/SBA-15 occurred at Cr surface density ≤0.53 Cr-atom/nm2 and <1.11 Cr-atom/nm2, respectively. The CrOx/SBA-15 samples exhibited better reducibility than the Cr-SBA-15 samples, with the best reducibility exhibited at Cr surface densities of 0.54 and 0.12 Cr-atom/nm2, respectively. 相似文献
18.
Direct synthesis of highly ordered Co-SBA-15 mesoporous materials by the pH-adjusting approach 总被引:1,自引:0,他引:1
Zhensong Lou Ruiheng Wang Hui Sun Yuan Chen Yanhui Yang 《Microporous and mesoporous materials》2008,110(2-3):347-354
Cobalt-substituted SBA-15 (Co-SBA-15) mesoporous materials were directly synthesized under mild conditions (pH > 2.0) by a “pH-adjusting” method using sodium hydroxide. Characterization results, such as powder X-ray diffraction (XRD), N2 physisorption and high-resolution transmission electron microscopy (HRTEM), showed that the resultant materials exhibit highly ordered hexagonal mesoporous structures, which was strongly correlated to the pH in the synthesis solution. The Co-SBA-15 sample obtained at pH of 3.0 gave the best structure. Solid state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated less condensation under higher pH. In addition, the pH also strongly affected the incorporation of cobalt cations in the silica framework. Diffuse reflectance UV–vis absorption spectra of calcined Co-SBA-15 samples and hydrogen temperature programmed reduction (H2-TPR) demonstrated that the cobalt ions in the silica framework locate at tetrahedrally coordinated sites. The effect of pH and sodium (NaOH) addition on improving the cobalt ion incorporation and the mesostructure of Co-SBA-15 materials were also discussed. 相似文献
19.
U. Brenn H. Ernst D. Freude R. Herrmann R. Jhnig H. G. Karge J. Krger T. Knig B. Mdler U. -T. Pingel D. Prochnow W. Schwieger 《Microporous and mesoporous materials》2000,40(1-3):43-52
A sodium ilerite, molar ratios 1Na2O:8.2SiO2:10.2H2O, was obtained with a good crystalline structure and characterized by several NMR techniques in addition to X-ray diffraction (XRD). The X-ray pattern of the as-synthesized ilerite is in very good agreement with the structure proposed by Gies and coworkers. The narrow 29Si MAS NMR signals (FWHM=0.3 ppm) indicate a good short-range order of the framework. The proton dynamics influences several 29Si NMR parameters. The 16 ppm signal in the 1H MAS NMR spectra is explained by a proton in a bridging position in the short (2.3 Å) O4–O4 bonding. The quadrupole coupling constant Cqcc=100 kHz with η=0.2 for the 16 ppm signal, which was obtained from the 2H MAS NMR spectra, confirms this explanation. 17O NMR shows also a separate signal for SiOH groups but cannot resolve the three expected lines for SiOSi. PFG NMR detects a small mobile portion of water in the ilerite, which is located probably on the external surface of the crystallites. An intracrystalline diffusion coefficient of the intercalated water molecules of the order of magnitude 10−15 m2 s−1 was obtained by NMR tracer exchange experiments. 相似文献
20.
Aluminium-containing ethane-silica hybrid mesoporous materials having ethane groups in the frame wall positions are synthesized using aluminium isopropoxide as well as aluminium nitrate as the aluminium sources. The materials were characterized in detail using powder XRD, N2 adsorption–desorption, SEM, TEM, TG-DTG, TPD, 29Si, 13C and 27Al MAS NMR techniques. Characterization techniques revealed that aluminium isopropoxide was the appropriate source for the synthesis of organo aluminosilicas on considering the structural ordering, acidity as well as the percentage of aluminium incorporation into the ethane bridge. 27Al MAS NMR displays aluminium as tetrahedrally coordinated in both the aluminium-containing organosilicas. Unlike the conventional EtOH–HCl template extraction process, in the present studies, we had used EtOH–NH4OH as the surfactant-extracting medium and chemical analysis results suggest that using this procedure the extent of dealumination can be greatly reduced. XRD and nitrogen physisorption studies further proved that the materials are hydrothermally stable, that the ordered pore channels retains its structure even after 150 h reflux in boiling water, while the conventional Al-MCM-41 catalyst collapsed its mesostructure after 50 h reflux in water. The improved hydrothermal stability of the hybrid materials, even in presence of sodium ions, is attributed to the thick pore walls as well as due to the presence of hydrophobic bridging ethane groups in the wall positions. 相似文献