Showing papers on "MCM-41 published in 2012"
TL;DR: In this paper, solid acid catalysts of the Keggin-type 12-tungstophosphoric acid (H3PW12O40, HPW) incorporated within the mesochannels of MCM-41 are prepared through a simple and effective impregnation method.
Abstract: In this work, solid acid catalysts of the Keggin-type 12-tungstophosphoric acid (H3PW12O40, HPW) incorporated within the mesochannels of MCM-41 are prepared through a simple and effective impregnation method. The catalysts are characterized by various techniques such as XRD, FTIR, TEM, N2 adsorption and thermal analysis. The surface acidities are measured by non-aqueous titration of n-butyl amine in acetonitrile and FTIR spectra of chemisorbed pyridine. The acidity and the textural parameters of the nanocomposites can be controlled simply by changing the loading of HPW on the MCM-41. The results indicate that the surface saturation coverage of MCM-41 is reached with 60 wt% HPW. The high saturation coverage is indicative of the well-dispersion of HPW within the mesochannels of MCM-41. The catalytic activities of the HPW/MCM-41 catalysts for the Pechmann, esterification reaction and Friedel–Crafts acylation reactions are studied in detail. Both the surface acidity and the catalytic activity sharply increase with the modification of MCM-41 by HPW. The sample with 60 wt% HPW shows the highest acidity and catalytic activity. The reusability tests of the catalysts show that the catalysts can be used several times without significant loss in activity. The HPW/MCM-41 catalysts have great potential for applications as commercial catalysts in promoting acid-catalyzed organic transformations under environmental friendly conditions and processes.
127 citations
TL;DR: In this article, the structure and activity of dispersed manganese oxides on γ-alumina and MCM-41 were compared at temperatures from 22 to 100°C.
113 citations
TL;DR: In this paper, a series of micro-mesoporous ZSM-5/MCM-41 composite molecular sieves were prepared by combining a microporous zeolite silica source with nano self-assembly methods, and characterized by SEM, TEM, XRD, N2 adsorption and desorption, TPD of ammonia, and their catalytic performance for the dehydration of methanol to dimethyl ether in a fixed bed microreactor at atmospheric pressure.
Abstract: A series of micro–mesoporous ZSM-5/MCM-41 composite molecular sieves were prepared by combining a microporous zeolite silica source with nano self-assembly methods, and characterized by SEM, TEM, XRD, N2 adsorption and desorption, TPD of ammonia, and their catalytic performance for the dehydration of methanol to dimethyl ether (DME) in a fixed bed microreactor at atmospheric pressure. Among these catalysts, the ZSM-5/MCM-41 sample alkali-treated with 1.5 mol/L NaOH solution, in which the relative crystallinity of ZSM-5 and MCM-41 are 54.5% and 30.5%, respectively, gave the best activity (XMeOH > 80%) with 100% selectivity and a long lifetime in a wide range of temperature from 190 °C to 300 °C. From the characterization and activity data, the formation mechanism of the micro–mesoporous composite molecular sieves was proposed to be a liquid-crystal templating mechanism.
110 citations
TL;DR: In this article, high-ordered mesoporous material (Bu4N)4H3(PW11O39)/MCM-41 with 10, 18, and 25.5% loadings was prepared by impregnation method in acidic media under reflux conditions, and characterized by XRD, HRTEM, Nitrogen adsorption/desorption, FT-IR, 31P CP-MAS NMR, XPS, SEM and TEM.
98 citations
TL;DR: The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5, and Insight into the core- shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes.
Abstract: A series of core-shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol-gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15-100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4-3.0 nm in diameter) to zeolite micropores (approximate to 0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (approximate to 7.88 x 10(-19) m(2) s(-1)) is almost retainable after covering with 75 nm-thick mesoporous silica shells (approximate to 7.25 x 10(-19) m(2)s(-1)), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core-shell composite shows greatly enhanced adsorption capacity (approximate to 1.35 mmolg(-1)) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (approximate to 0.4 mmolg(-1)) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core-shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Bronsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5. Insight into the core-shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes.
95 citations
TL;DR: In this article, MCM-41 supported CoAMo bimetallic catalysts with different Co/Mo atomic ratios were pre-pared by incipient wetness impregnation, and the channels of MCM41 acted as nano-reactor.
78 citations
TL;DR: Amine functionalized MCM-41 with varying amine amount (6.4, 10.2, 12.8, and 20 wt %) was prepared by the cocondensation method using cetyltrimethylammonium bromide (CTAB) as structure-directing agent (SDA), 3-aminopropyltriethoxysilane (APTES), and tetraethylorthosilicate (TEOS) as discussed by the authors.
Abstract: Amine functionalized MCM-41 (NH2-MCM-41) with varying amine amount (6.4, 10.2, 12.8, and 20 wt %) was prepared by the cocondensation method using cetyltrimethylammonium bromide (CTAB) as structure-directing agent (SDA), 3-aminopropyltriethoxysilane (APTES), and tetraethylorthosilicate (TEOS). The characterizations of the synthesized samples were performed by X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, and Fourier transform infrared spectral studies. The results revealed that the ordered hexagonal structure of MCM-41 was well retained after the amine functionalization irrespective of the amount of amine loading. Adsorption of Cu(II) from the aqueous state with varying parameters such as concentration, temperature, and pH was performed over as-synthesized and surfactant-removed NH2-MCM-41. Atomic adsorption spectroscopy investigations reported a higher percentage of adsorption in the case of as-synthesized NH2-MCM-41 compared to surfactant-removed samples. The e...
74 citations
69 citations
TL;DR: The results indicated that US-H(2)O(2)-α-Fe(2,O(3)/MCM-41 nanocomposite system is effective for the degradation of MB, suggesting its great potential in removal of dyes from wastewater.
56 citations
TL;DR: The structural and textural characterization techniques reveal that the resulted surfactant-free MCM-41 exhibits higher features compared to that of those obtained using the conventional calcinations approaches.
55 citations
TL;DR: In this paper, an iron-containing MCM-41 nanoparticles were successfully prepared using CTAB in sodium hydroxide medium at ambient temperature from both direct-hydrothermal and post-synthesis methods.
Abstract: Iron-containing MCM-41 nanoparticles (Fe-MCM-41 NPs) were successfully prepared using cetyltrimethylammonium bromide (CTAB) in sodium hydroxide medium at ambient temperature from both direct-hydrothermal and post-synthesis methods. The materials were characterized by X-ray diffraction, nitrogen adsorption/desorption isotherms, SEM, TEM, and UV–vis spectroscopy. The characterization results show the existence of highly ordered hexagonal mesopores in the nanoparticles and tetrahedral Fe species in the framework. In phenol hydroxylation with aqueous H2O2, Fe-MCM-41 nanoparticles displayed higher initial reaction rate than Fe-MCM-41 with larger particle size. It is proposed that the diffusion of the reactants is accelerated and the accessibility to the catalytic Fe species is enhanced in the shorter mesopore channels in Fe-MCM-41 nanoparticles. The recyclability potential of the nanoparticles was evaluated in the regeneration by room-temperature washing approach. Fe-MCM-41 NPs also appear to be suitable catalysts for the Friedel–Crafts alkylation of benzene with benzyl chloride.
TL;DR: Mesoporous MCM-41 was prepared by leaching of sepiolite and sequent hydrothermal synthesis in NaOH solution with hexadecyltrimethylammonium bromide as template as discussed by the authors.
TL;DR: Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes and are used as cooperative catalysts in the Henry reaction.
Abstract: The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction.
TL;DR: In this article, a magnetically recyclable catalyst for one-pot synthesis of N-aryl-2-amino-1,6-naphthyridine derivatives was proposed.
TL;DR: In this article, the isomerization of endo-dicyclopentadiene using Al-grafted MCM-41 was studied as an industrial practical synthesis route for exo-DCPD.
Abstract: The isomerization of endo -dicyclopentadiene ( endo -DCPD) using Al-grafted MCM-41 was studied as an industrial practical synthesis route for exo -DCPD. The catalyst was prepared with post-synthesis grafting method, characterized by XRD, N 2 adsorption/desorption, 27 Al and 29 Si MAS NMR, in-situ pyridine adsorption IR and NH 3 -TPD. The materials retain ordered mesoporous structure and high surface area. Al atoms are preferentially anchored in tetra-coordination, but these in octa-coordination increase significantly in case of high Al content. The amount of Bronsted acid is closely related to the amount of tetra-coordinated Al species whereas that of Lewis acid corresponding to the total Al content. The prepared material shows higher activity than microporous zeolites because its mesoporous structure gives free diffusion and excellent coke tolerance capability. A good correlation between the conversion of endo -DCPD and the amount of Lewis acid was observed. Specifically, the weak Lewis acid sites catalyze the endo - to exo -isomerization, meanwhile the moderate ones account for the [2 + 2] cycloaddition of two DCDP molecules. Catalyst with Si/Al of 8 is most active due to its highest concentration of weak Lewis acid. Addition of inert solvent, relatively low reaction temperature and high catalyst dosage can improve the isomerization. The deactivated catalyst can be easily regenerated by calcination.
TL;DR: In this article, the mesoporous support Al2O3 was incorporated onto the surface of AM 10 in order to modify the surface property of AM10, forming composite Fe/Al 2O3-MCM-41 (Fe/AM 10).
Abstract: In situ incorporation of mesoporous Al2O3 (meso-Al2O3) into the MCM-41 extraframework without blocking the pores generates an ordered, long range and high surface area mesoporous support Al2O3–MCM-41 (AM). The mesoporous support surprisingly shows high surface area as compared to pristine MCM-41. The incorporation of meso-Al2O3 into the extraframework of MCM-41 through the silanol group is evidenced by FTIR, 27Al MAS NMR and 29Si MAS NMR spectroscopy. The result shows that Si/Al ratio 10 (AM 10) possesses improved textural properties as compared to AM 50 and AM 90. Iron is incorporated onto the surface of AM 10 in order to modify the surface property of AM 10, forming composite Fe/Al2O3–MCM-41 (Fe/AM 10). Characterization by small angle X-ray diffraction (SXRD), transmission electron microscopy (TEM), and N2 adsorption–desorption measurements reveals that the mesoporous support and iron incorporated support possess large BET surface area (207–1244 m2 g−1), narrow pore size (2.4–2.7 nm) and high pore volume (0.370–2.37 cm3 g−1). Among them, AM 10 shows highest surface area (1244 m2 g−1), narrow pore size (2.7 nm) and pore volume (2.37 cm3 g−1). The incorporation effect of both meso-Al2O3 and iron in the formation of Fe/AM 10 has been well established by 27Al MAS NMR spectroscopy. X-Ray photoelectron spectroscopy study confirms the 2+ state of iron in Fe/AM 10 and also establishes the incorporation of meso-Al2O3 and iron. Among the prepared mesoporous supports and different wt% of iron incorporated supports, it is seen that 5 Fe/AM 10 (‘5’ denotes the wt% of iron) has high adsorption as well as photo-Fenton degradation activity for MB. Moreover, 5 Fe/AM 10 is not merely a good adsorbent but also an efficient catalyst in the adsorption and photo-Fenton degradation (100%) of MB in 15 and 5 minutes, respectively. Furthermore, in the case of mixed cationic and anionic dyes (uniform mixture of methylene blue and methyl orange), MO adsorption and degradation (by photo-Fenton process) occur appreciably on the surface of MB through cationic–anionic interaction of MB and MO.
TL;DR: In this paper, the effect of the textural properties of support materials on the palladium-catalyzed hydrogenation of succinic acid using mesoporous supports (MCM-41 and SBA-15) was examined.
TL;DR: In this article, two different methods for the preparation of copper-containing catalysts have been described, including post-synthesis and co-condensation methods, using both organic and aqueous media.
Abstract: In this paper two different methods for the preparation of copper-containing catalysts have been described. Copper (II) ethylacetoacetate or copper (II) nitrate metallic precursors have been immobilized onto previously organofunctionalized MCM-41 material with N4-(3-(triethoxysilyl)propyl)pyrimidine-2,4,6-triamine (DAPyPTS) compound. The amino hybrid materials have been prepared by using both post-synthesis and co-condensation methods. In addition, the immobilization has been performed using organic and aqueous media. The catalysts have been characterized using X-ray diffraction (XRD), N2 adsorption–desorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscope (SEM) with energy-dispersive X-ray (EDX), elemental analysis, 1H, 13C and 28Si MAS NMR, FT-IR and DRUV–vis spectroscopy. Copper-containing catalysts have been tested in the benzyl alcohol oxidation with TBHP and H2O2 as oxidants and under solventless conditions. High selective (97%) to benzaldehyde was achieved using TBHP as oxidant and copper (II) ethylacetoacetate immobilized onto organofunctionalized MCM-41 as catalyst under solventless conditions.
TL;DR: In this article, in situ synthesis of Pd nanoparticles supported on boron (B)-substituted MCM-41 with Si/B ratio varying from 100 to 5 was carried out by hydrothermal method using H3BO3 as B source.
TL;DR: In this article, the catalytic thermal degradation of polypropylene over aluminum containing ordered mesoporous MCM-41 and SBA-15 based materials was studied in a semi-batch reactor.
TL;DR: In this article, CoO and Co3O4 nanoparticles were uniformly dispersed inside mesoporous MCM-41 and Al-MCM41 supports using supercritical CO2 reactive deposition.
TL;DR: The obtained surfactant-assisted delivery systems constitute a new approach towards controlled release of small therapeutic molecules and were used as drug delivery carriers for ibuprofen.
Abstract: A novel series of mesoporous silica materials has been developed by using non-ionic, biocompatible alkyl maltoside surfactants as organic structure directing agents and working under biomimetic conditions (e.g., room temperature and almost neutral pH) to avoid modifications of potential drugs occluded within. The obtained mesophases were tuned by changing the template and its concentration. These sugar surfactant–silica platforms were used as drug delivery carriers for ibuprofen, by encapsulating drug molecules within the hydrophobic core of the template micelles. The obtained surfactant-assisted delivery systems constitute a new approach towards controlled release of small therapeutic molecules.
TL;DR: A series of Fe-MCM-41s with high iron content were synthesized using direct hydrothermal method under alkaline condition using tartaric acid as complexing reagent and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent.
TL;DR: Ni-and Co-incorporated MCM-41 type mesoporous materials with Ni/Si and Co/Si molar ratios of 0.12 were synthesized, characterized, and tested in both steam reforming of ethanol (SRE) and sorptionenhanced steam reforming (SESRE) reactions.
Abstract: Ni- and Co-incorporated MCM-41 type mesoporous materials with Ni/Si and Co/Si molar ratios of 0.12 were synthesized, characterized, and tested in both steam reforming of ethanol (SRE) and sorption-enhanced steam reforming of ethanol (SESRE) reactions. Characterization results showed that Co and Ni were successfully incorporated and well-dispersed in the mesoporous MCM-41 support. Ni- and Co-incorporated MCM-41 catalysts had surface area values of 449.0 and 303.6 m2/g, respectively. They also had narrow pore size distributions, with average pore diameters of 2.2 and 1.98 nm, respectively. SESRE results obtained with these catalysts showed that in situ capture of CO2 during ethanol reforming reaction significantly enhanced hydrogen yield in the temperature range of 500–600 °C. The catalytic performance of Ni-incorporated MCM-41 was much better than the Co-incorporated MCM-41, in hydrogen production by ethanol reforming. The highest hydrogen yield value obtained over the Ni-incorporated MCM-41 catalyst was a...
TL;DR: In this paper, the differences in an uptake and subsequent release of anti-inflammatory drug naproxen from unmodified and amino modified MCM-41 samples were studied, and the amount of the drug released was monitored with thin layer chromatography (TLC) with densitometric detection in defined time intervals.
Abstract: Hexagonally ordered mesoporous silica material MCM-41 (SBET = 1090 m2/g, pore size = 31.2 A) was synthesized and modified by 3-aminopropyl ligands. The differences in an uptake and subsequent release of anti-inflammatory drug naproxen from unmodified and amino modified MCM-41 samples were studied. The prepared materials were characterized by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), nitrogen adsorption/desorption, Fourier-Transform Infrared Spectroscopy (FT-IR), Small-angle X-ray scattering (SAXS), thermoanalytical methods (TG/DTA) and elemental analysis. The amount of the drug released was monitored with thin layer chromatography (TLC) with densitometric detection in defined time intervals. The amounts of the released naproxen from mesoporous silica MCM-41/napro and amine-modified silica sample A-MCM-41/napro were 95 and 90% of naproxen after 72 h. In this study we compare the differences of release profiles from mesoporous silica MCM-41 and mesoporous silica SBA-15.
TL;DR: In this paper, mesoporous MCM-41 silica spheres were synthesized via modified Stober method and modified by silylation, which showed that the obtained MCM41 spheres had ordered mesophorous structure and spherical morphology.
TL;DR: In this article, the thermogravimetry (TG) was used for characterization of the fly ash (FA)-based MCM-41 mesoporous materials, which were synthesized using silica extracts from different FA.
Abstract: The thermogravimetry (TG) was used for characterization of the fly ash (FA)-based MCM-41 mesoporous materials. MCM-41 mesoporous materials were synthesized using silica extracts from different FA. The synthesis of MCM-41 from FA was carried out by the hydrothermal method using the supernatants of coal FA (in the form of sodium silicate) and cationic cetyltrimethylammonium bromide (CTAB) surfactants as the structure-directing agents. On the basis of the data obtained from the TG analysis, thermal behaviour of FA-based MCM-41 mesoporous materials was assessed. This study has established the range of temperatures corresponding to the desorption of water, decomposition of the surfactant and condensation of silanol, thereby making the overall quality assessment of FA-based MCM-41 mesoporous materials.
TL;DR: A series of MCM-41 samples containing molybdenum oxide as active species in the mesoporous channels loaded by spontaneous monolayer dispersion (SMD) and impregnation (IM) have been prepared and characterized using XRD, N2 adsorption-desorption analysis, Fourier transform infrared spectroscopy (FTIR) and intelligent gravimetric analyzer (IGA) as mentioned in this paper.
TL;DR: In this article, three different mesoporous silica materials, i.e., rice husk ash, RHA-MCM-41 and commercial silica gel were employed as catalyst to study the styrene oxide ring opening with aniline to form β-amino alcohols.
TL;DR: In this paper, the condensation reaction of 1,2-diketones and o-phenylenediamines was investigated in the presence of nano-sized mesoporous silica (MCM-41) supported 12-tungstophosphoric acid (TPA) as solid acid catalyst.