Showing papers on "MCM-41 published in 2008"
TL;DR: In this article, PdCl 2 / SBA-15 showed the highest capacity of selective sulfur adsorption among all known sorbents, and the significant breakthrough occurred at about 50.0 ml/g for desulfurization of JP-5 light fraction.
158 citations
TL;DR: In this article, the number and strength of Bronsted acid sites were determined quantitatively by a method of infrared-mass spectroscopy/temperature-programmed desorption (IRMS-TPD) of ammonia.
100 citations
TL;DR: In this paper, the first step was a simple condensation under basic conditions yielding CP-MS41 leading sequentially to R4Cl-MS 41, and a wide variety of ionic liquids by manipulating the TEOS to 3-chloropropyltriethoxysilane (ClPTES) ratios were synthesized and characterized by a number of physico-chemical measurements such as XRD, BET, FT-IR, CP 13C, 29Si MAS-NMR and TG/DTG.
97 citations
TL;DR: The pH-controlled gate-like scaffoldings on S1 might be a suitable prototype for the development of orally applicable delivery systems designed to have the particular ability to protect the cargo from the acidic conditions of the stomach but will release the load at the intestine.
97 citations
TL;DR: In this paper, 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 SBA16 mesoporous silica materials.
80 citations
TL;DR: In this paper, mesoporous nanocomposite silicotungstic acid (STA) was successfully synthesized following different impregnation procedures, and the results showed that the catalyst preparation procedure had significant influence on its activity as well as the product distribution in ethanol dehydration.
Abstract: In this study, mesoporous nanocomposite silicotungstic acid (STA) incorporated MCM-41 and mesoporous aluminosilicate catalysts with narrow pore size distributions, in the range of 2.5–3.5 nm, were successfully synthesized following different impregnation procedures. Results showed that the catalyst preparation procedure had significant influence on its activity as well as the product distribution in ethanol dehydration. STAMCM41C catalyst, which was prepared by the impregnation of STA into calcined MCM-41 containing a W/Si ratio of 0.24, and STAMAS catalyst, which was prepared by the impregnation of STA into mesoporous aluminosilicate, showed very high activities in dehydration of ethanol. Ethylene yield showed an increasing trend with temperature, reaching to about 100% above 250 °C. In contrast to ethylene, DEE was formed at lower temperatures, reaching to a yield value of about 70% at 180 °C with STAMCM41C. DEE formation at lower temperatures was concluded to be due to the presence of Bronsted acid sit...
79 citations
TL;DR: In this paper, the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP), anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide were presented.
Abstract: Metalloporphyrin catalysts are able to carry out selective oxidation of organic substrates with several oxidizing agents. Recently, mesoporous materials have been studied as supports because they present high specific surface area, better dispersion and regeneration properties. This work presents the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP, where TPP = tetraphenylporphyrin) anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide. A modified sol–gel preparation was chosen for the synthesis of the MCM-41 mesoporous material, as well as the anchoring was followed by Soxhlet extraction to ensure strong adsorption of the complex. The supported materials were much more stable than pure metalloporphyrins. The synthesized catalysts were characterized by UV–vis, FTIR, XRD, ICP-AES, 29 Si MAS-NMR and thermal analysis, before and after incorporation. Evidence of the metalloporphyrin immobilization was confirmed by elemental analysis and their activity in the oxidation reaction. FeTPPCl/MCM-41 showed higher conversion than CoTPP/MCM-41 and MnTPPCl/MCM-41. However, MnTPPCl/MCM-41 even in low concentration on the support showed a good conversion for the direct oxidation of cyclohexene with the highest turnover number (1.54 × 10 5 ). All catalysts showed similar selectivity that favors allylic oxidation products over epoxidation. No leaching of the metalloporphyrins was observed after the reaction.
73 citations
TL;DR: In this paper, a detailed study about the relationship existing between the Ti loading in the catalyst, the acid properties and the catalytic efficacy is presented in this contribution. But the authors did not consider the effect of the presence of tetrahedral Ti species in the framework, the Bronsted acid sites were also generated at high Ti loadings.
73 citations
TL;DR: In this article, mesoporous MFI zeolite is fabricated through impregnating a structure-directing agent into as-synthesized MCM-41 followed by dry-gel conversion to transform amorphous silica to Zeolite crystal.
Abstract: Mesoporous MFI zeolite is fabricated through impregnating a structure-directing agent into as-synthesized MCM-41 followed by dry-gel conversion to transform amorphous silica to zeolite crystal. The original surfactant in the as-synthesized MCM-41 is used as the necessary mesoporogen to direct the mesopore genesis of zeolites, using the process of streaming to spur the transformation and tailoring the texture of mesoporous ZSM-5 by adjusting the Si : Al ratio in the MCM-41 source. The resulting sample is characterized by X-ray diffraction, IR spectroscopy, TEM and N2 adsorption to evaluate the textural properties of the mesoporous zeolite. Two kinds of nitrosamines with different structures are used as probe molecules to survey the adsorption function of the resulting mesoporous zeolite. Mesoporous zeolites exhibit good adsorption capacities and exceed either microporous zeolite or mesoporous silica. This synthesis strategy omits the fabrication and removal of the carbon template and simplifies the synthesis process of mesoporous zeolites, saving energy and time.
72 citations
TL;DR: In this paper, ZSM-5 synthesis gels were aged during 18-72h at temperatures between 30 and 90°C and were obtained from gels with diameters around 2.5nm.
69 citations
TL;DR: In this paper, the authors used ordered mesoporous silica supports (MCM-41) for the hydrogenation of diethyl itaconate and showed that the high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of up to 6000 h −1 for hydrogenation, and no deactivation of the catalysts is observed after repeated recycling.
Abstract: Chiral Schiff base–gold and –palladium complexes were immobilized on ordered mesoporous silica supports (MCM-41), and their catalytic hydrogenation ability is studied and compared with that of their homogeneous counterparts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of up to 6000 h–1 for the hydrogenation of diethyl itaconate. The easily recoverable immobilized catalysts duplicate the activity of their homogeneous analogues, and no deactivation of the catalysts is observed after repeated recycling. Gold(III) homogeneous or heterogenized complexes also catalyze the homocoupling of arylboronic acids or alkynes to afford symmetrical biaryls, whereas the respective gold(I) and palladium(II) complexes catalyze the corresponding cross-coupling reaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, a dilute solution route in sodium hydroxide medium at ambient temperature was used to obtain 80-160 nm in diameter (Ti-MCM-41 NP) nanoparticles.
TL;DR: The presence of the heterogeneous mesoporous Al-MCM-41 catalyst remarkably accelerated the cyanosilylation of various aldehydes and ketones with trialkylsilyl cyanide, giving the corresponding cyanohydrin silyl ethers in quantitative yields under mild reaction conditions.
TL;DR: In this paper, a hexagonal mesoporous silica containing titanium, Ti-HMS(30), was also prepared, using n-dodecylamine as a template at pH 10.
Abstract: Mesoporous materials containing aluminum and titanium were obtained by direct synthesis at room temperature, using a sol–gel method with two reaction steps (acid and alkaline hydrolysis). After solvent extraction and calcination (823 K), three solids, H-MCM-41, Al-MCM-41(10) and Ti-MCM-41(30) were obtained, where the numbers in parenthesis denote the Si/metal molar ratio. A hexagonal mesoporous silica containing titanium, Ti-HMS(30), was also prepared, using n-dodecylamine as a template at pH 10. Characterization of samples was made by ICP-OES, ATR-FTIR, XRD, N2 adsorption at 77 K, XPS and ammonia TPD. The results indicate that the samples have low crystallinity, surface areas of 500–750 m2/g, high degree of isomorphic substitution and, in certain cases, higher acidity (Bronsted and Lewis) as compared to a commercial Y zeolite (Si/Al = 1.5). Catalytic studies of anthracene oxidation in liquid phase at 348 K, using tert-butylhydroperoxide as oxidant agent showed that the Ti-HMS(30) sample is much more prone to produce 9,10-anthraquinone (yield >90%) than the other mesoporous samples. This performance is directly related to parameters such as surface area, nature of the heteroatom introduced, Si/Ti molar ratio and strength and concentration of acid sites. The reaction kinetic experiments show a great dependency of specific reaction rates with temperature (in the range 320–348 K) and an activation energy value of 15.2 kcal/mol. A set of experiments performed under factorial design indicated that an optimal oxidant/aromatic ratio is 5.5 and the optimal amount of catalyst is about 44.3 mg. In general, our results confirm that the synthesized materials are promising catalysts (redox and acid) for petrochemical applications.
TL;DR: To perform organic reactions without solvents is one of the most important challenges for organic chemists from both an economic and environmental standpoint because it would reduce environmental pollution and bring down handling costs owing to simplification of experimental procedures and workup techniques.
Abstract: To perform organic reactions without solvents is one of the most important challenges for organic chemists from both an economic and environmental standpoint because it would reduce environmental pollution and bring down handling costs owing to simplification of experimental procedures and workup techniques. Solvent-free reactions may be carried out by using the reactants alone or by incorporating them in clays, zeolites, silica, alumina or other matrices. Moreover, the development of active and environmentally friendly solid catalysts is also a priority with respect to green chemistry. Such catalysts offer several advantages such as good selectivity, easy separation and the possibility to be recovered and reused. In recent years, Er salts have been employed as efficient and non-toxic Lewis acid catalysts in several organic transformations. Among the plethora of lanthanide ions, Er is one of the most efficient Lewis acids in terms of the values of its hydrolysis constant (Kh) and water-exchange rate constants [6]
TL;DR: Ulasonic irradiation has a particular effect on MCM-41 structural uniformity and reduced the reaction times and improved the product yields, and the solid catalysts could be recovered and reused several times without loss of its activity.
TL;DR: In this paper, a series of La2O3−V2O5/MCM-41 catalysts with high specific surface area were prepared by means of incipient wetness impregnation for the dehydrogenation of ethylbenzene to styrene using CO2 as oxidant.
Abstract: A series of La2O3−V2O5/MCM-41 catalysts with high specific surface area were prepared by means of incipient wetness impregnation for the dehydrogenation of ethylbenzene to styrene using CO2 as oxidant. At 600 °C, the conversion of ethylbenzene and selectivity to styrene over 10La15V/MCM-41 after an on-stream time of 4 h was about 86.5 and 91.0%, respectively. The properties of the catalysts before and after the reaction were characterized using techniques such as X-ray diffraction, specific surface area, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and oxidation. The high catalytic activity and stability of 10La15V/MCM-41 during dehydrogenation of ethylbenzene is attributed to an optimized La/V atomic ratio. The accumulation of amorphous carbon species on the external surface of La2O3−V2O5/MCM-41 is the cause for catalyst deactivation.
TL;DR: In this article, a combination of various physical techniques was used for characterizing the catalysts, such as X-ray diffraction, N 2 physisorption, diffuse reflectance UV-Vis (DR-UV-Vis), Fourier transmission infra red (FT-IR), atomic emission spectroscopy (ICP-AES), and 29 Si MAS NMR (magic-angle spinning nuclear magnetic resonance) spectrographs, to confirm that Nb atoms are isolated and tetrahedrally coordinated in the framework of MCM-41.
TL;DR: In this paper, the template-ion exchange (TIE) method, an equilibrium adsorption (EA) of nickel ammine complex, and a conventional impregnation (IMP) method were applied to prepare nickel ion-loaded mesoporous silica MCM-41 and silica gel and their catalytic activity was examined for the newly developed ethene to propene (ETP) reaction.
TL;DR: In this article, a copper-incorporated MCM-41-type high-surface-area mesoporous materials were synthesized following a direct hydrothermal synthesis method and also by the impregnation of copper into the mesopores of the pre-synthesized MCM41 structure.
Abstract: In the present study, novel copper-incorporated MCM-41-type high-surface-area mesoporous materials were synthesized following a direct hydrothermal synthesis method and also by the impregnation of copper into the mesopores of the pre-synthesized MCM-41 structure. XRD results indicated the formation of a CuO phase within the MCM-41 structure. Sharp H2S breakthrough curves, quite high sorption rate parameters, and high sulfur retention capacities were obtained in high-temperature removal of H2S using these copper-incorporated mesoporous materials. XRD patterns of the sulfided products indicated the formation of a Cu1.81S phase within the MCM-41 structure. A deactivation model gave good predictions of the experimental H2S breakthrough data.
TL;DR: Palladium nanocatalysts have been prepared by anchoring (η 3 -C 3 H 5 ) 2 Pd 2 Cl 2 onto diamine-functionalized MCM-41 supports followed by reaction with hydrogen under catalytic conditions.
Abstract: Palladium nanocatalysts have been prepared by anchoring (η 3 -C 3 H 5 ) 2 Pd 2 Cl 2 onto diamine-functionalized MCM-41 supports followed by reaction with hydrogen under catalytic conditions. The catalyst precursor and used catalyst have been studied by solid-state NMR ( 13 C, 29 Si), XPS, and TEM. The organometallic-derived catalyst exhibits the best performance (activity and selectivity) to date toward the selective hydrogenation of industrially relevant o- and m-chloronitrobenzene to the corresponding chloroaniline derivatives and is distinctly superior to 5% Pd/C. Grazing angle XPS studies reveal that conversion of the tethered molecular species to the nanoparticles of palladium produces a core-shell nanostructure.
TL;DR: The role of silylation in changing the surface hydrophilic character of these catalysts is investigated in this article, and the effect is more pronounced on Ti-MCM-41 than with low-surface area Ti-SiO2 and the catalytic performances are strongly dependent on the nature of the reactant.
TL;DR: In this paper, the photocatalytic reactivity of the catalysts for the partial oxidation of methane was found to strongly depend on the local structure of the V-oxide species including the coordination and loading sites.
Abstract: V-containing MCM-41 catalysts were prepared by a direct synthesis method under acidic and basic conditions and impregnation. Their photocatalytic reactivity was evaluated for the selective photocatalytic oxidation of methane with NO under UV irradiation at 295 K. Selective methanol formation was observed on V-MCM-41 prepared in acidic solution and imp-V/MCM-41, while only coupling reaction products were obtained on V-MCM-41 prepared in basic solution. The photocatalytic reactivity of the catalysts for the partial oxidation of methane was found to strongly depend on the local structure of the V-oxide species including the coordination and loading sites, i.e., the charge transfer excited states of the isolated tetrahedral V5+-oxide species supported on the catalyst surface act as the active sites for the selective photocatalytic oxidation of methane into methanol.
TL;DR: In this paper, a mesoporous Ti-MCM-41 molecular sieve was synthesized under hydrothermal conditions and the resulting catalysts were characterized by powder X-ray diffraction (XRD), N 2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectrography (DRS), thermogravimetric analysis (TGA) and differential thermal analysis (DTA), scanning electron microscopy (SEM), energy dispersive spectrographic (EDS),
TL;DR: In this article, a detailed and correlative study about the effect of different synthesis parameters on physicochemical properties of the material has been carried out, and it seems that the synthesis time and the surfactant chain length are critical variables to obtain good structures.
TL;DR: The MCM-41 sample prepared in this study exhibited well defined long-range order and good hydrothermal stability and it was demonstrated that reducing the time of self-assembly step to 2 h during the synthesis had no unfavorable effect on the quality of MCM.
TL;DR: In this paper, a novel organic-inorganic mesoporous hybrid materials were synthesized by linking lanthanide (Tb{sup 3+], Eu{Sup 3+}) complexes to the MCM-41 through modified meta-methylbenzoic acid (MMBA-Si) using co-condensation method in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template.
TL;DR: In this paper, mesoporous materials with a MCM-41 structure were applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with hydrogen peroxide at 343 K.
TL;DR: In this article, a mesoporous molecular sieves MCM-41 was used to impregnation of zirconium sulfate followed by calcination for n-butane isomerization.
TL;DR: In this paper, the ionic liquids were generated on chloropropyl functionalized MCM-41 (CP-MS41) through the immobilization of trialkylamines, and their catalytic performance in the chemical fixation of CO2 with epoxide to produce cyclic carbonate was investigated.
Abstract: In this study, ionic liquids (ILs) on ordered mesoporous materials were prepared and their catalytic performance in the chemical fixation of CO2 with epoxide to produce cyclic carbonate was investigated. The ionic liquids were generated on chloropropyl functionalized MCM-41 (CP-MS41) through the immobilization of trialkylamines. The first step involved simple condensation under basic conditions yielding CP-MS41, which lead sequentially to R4Cl-MS41. A variety of CP-MS41s were synthesized by manipulating the TEOS to 3-chloropropyltriethoxysilane (ClPTES) ratio, and characterized using a number of physico-chemical measurements including XRD, BET, FT-IR, CP 13C, 29Si MAS-NMR and TG/DTG. 29Si MAS-NMR and FT-IR showed that the ionic liquids formed adduct with the chloropropyl groups attached to the silica surface. The ordering of the mesoporous structure decreased gradually with increasing ClPTES concentration in the synthesis gel. This study reports a methodology for synthesizing hybrid MS41 and solvent extraction techniques. The activity of the immobilized ionic liquids (IILs) was maintained after recycling and was higher in the IILs containing amines with a lower alkyl chain length.