MCM-41 Mesoporous Materials Research Articles

SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N 2 physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 °C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.

Physicochemical stability of high indomethacin payload ordered mesoporous silica MCM-41 and SBA-15 microparticles

Stability of high indomethacin (IMC) content formulations based on ordered mesoporous silica MCM-41 and SBA-15 materials was studied before and after a 3 month storage in stressed conditions (30 °C/56% RH). Overall, the physical stability of the samples was found satisfactory after the storage. However, some issues with the chemical stability were noted, especially with the MCM-41 based samples. The stability issues were evident from the decreased HPLC loading degrees of the drug after stressing as well as from the observed extra peaks in the HPLC chromatograms of the drug in the stressed samples. Drug release from the mesoporous formulations before stressing was rapid at pH 1.2 in comparison to bulk crystalline IMC. The release profiles also remained similar after stressing. Even faster and close to complete IMC release was achieved when the pH was raised from 1.2 to 6.8. To our knowledge, this is the first report of chemical stability issues of drugs in mesoporous silica drug formulations. The present results encourage further study of the factors affecting the chemical stability of drugs in mesoporous silica MCM-41 and SBA-15 formulations in order to realize their potential in oral drug delivery.

Continuous stirred tank reactor for ethylene oligomerization catalyzed by NiMCM-41

The performances of Ni-exchanged MCM-41 mesoporous material as catalyst for the ethylene oligomerization were evaluated in a pilot plant equipped with a continuous stirred tank reactor (CSTR). During the catalytic tests performed at 30°C, without any start-up solvent, over 170h on stream, the catalyst was highly active and stable to deactivation. Moreover, the reaction was very selective, resulting mainly in C4, C6, C8 and C10 olefins. The CSTR unit described in this article proved to be an effective and useful tool for performing complex catalytic studies, involving three-phase systems.

석탄회 산업폐기물로부터 제조한 메조다공성 실리카소재를 촉매로 사용하는 Knoevenagel 수용액 반응

화력발전소에서 배출되는 석탄회를 이용하여 메조다공성 소재인 MCM-41을 제조하였다. 제조한 소재는 XRD, FTIR, SEM 및 EDS 방법으로 특성을 규명하였다. 이 소재의 촉매활성을 방향족 알데히드와 malonontrile의 Knoevenagel축합 반응에서 5-arylindene malononitriles의 합성에 대해 연구하였다. 이 방법의 특징은 쉬운 취급법, 안정성, 촉매의 재사용 및 생태친화성, 고수율, 짧은 반응시간, 간단한 실험과정 및 마무리 절차 등을 들 수 있다. Coal fly ash of thermal power plants converted into mesoporous materials MCM-41. The synthesized material was characterized by XRD, FT-IR, SEM, and EDS techniques. The catalytic activity of prepared material was studied for the synthesis of 5-arylindene malononitriles via Knoevenagel condensation of aromatic aldehydes and malonontrile is described. The features of present method are easy handling, stability, reusability, and eco-friendliness of catalyst, high yields, short reaction time, simple experimental and work up procedure.

Pt and Pd nanoparticles supported on structured materials as catalysts for the selective reductive amination of carbonyl compounds

Metal catalysts based on Pt and Pd nano-particles supported on structured microporous Beta zeolites and mesoporous MCM-41 materials, as well as specially designed γ-Al2O3 samples, were synthesized following a simple and economic procedure. Physico-chemical characterization of metal-composites (by XRD, IR spectroscopy, TEM, N2 adsorption, ICP, among others) indicated that both Pt and Pd nano-particles were adequately supported and homogeneously dispersed on supports. These metal/solid acid composites were applied as efficient catalysts under mild reaction conditions in the selective reductive amination of ketones, a useful industrial reaction for the synthesis of substituted amines and N-heterocycles. Results obtained showed that Pt/Al-Beta catalyst possesses the best catalytic activity (TON=1610, with amine selectivities >95%) superior to that observed with commercial Pt/C and Pt/Al2O3 (TON≈1000). Enhancements in Pt/Al-Beta samples were achieved by optimizing the Pt loading, and mainly the Si/Al molar ratio in solids. On the contrary, inferior catalytic activities were encountered with the Pt/Si-MCM-41 and Pt/Al-MCM-41 materials. The Pd incorporation on MCM-41 materials produced more active catalysts than the commercial Pd/C and Pd/Al2O3 samples. Finally, the study of Pt/ and Pd/γ-Al2O3 materials demonstrated that the treatments of support prior to the metal impregnation and the posterior calcinations processes were essentials to obtain efficient catalysts.

Perchlorate uptake by organosilicas, organo-clay minerals and composites of rice husk with MCM-48

A variety of oraganosilicas such as MCM-41 and MCM-48 and composites of rice husks with MCM-48 were synthesized under an array of conditions and characterized by powder X-ray diffraction (XRD). Various MCM-41 mesoporous materials were prepared at room temperature using different surfactants. MCM-48 silica and its composites with rice husks were synthesized under hydrothermal conditions using cetyltrimethylammonium (CTMA) bromide and rice husks. Both untreated and carbonized rice husks were used for preparing composites of rice husk with MCM-48. Organo-clay minerals procured from two commercial sources were also investigated for their perchlorate uptake. Among the MCM-41 materials, the sample prepared from octadecyltrimethylammonium (ODTMA) chloride showed the highest perchlorate uptake capacity of 0.227 ± 0.006 meq/g while MCM-48 showed the highest perchlorate uptake capacity of 0.437 ± 0.011 meq/g among all the oraganosilicas and organo-clay minerals tested here. The uptake of perchlorate by organosilicas and organo-clay minerals is due to residual positive charge on the surfactants located in the mesopores of organosilicas and interlayers of organo-clay minerals.

NSAID naproxen in mesoporous matrix MCM-41: drug uptake and release properties

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.

Preparation of MCM-41 incorporated with lacunary Keggin polyoxometalate and its catalytic performance in esterification

The ordered mesoporous MCM-41 materials incorporated with lacunary polyoxometalate were prepared via an original direct synthesis method. As the control, the samples with similar lacunary polyoxometalate loadings were also prepared by impregnation of MCM-41. The prepared samples were characterized by XRF, XRD, FT-IR, Raman spectra, HRTEM, SEM, N2 adsorption isotherm, TG–DTA, and NH3–TPD technology. The results show that the lacunary polyoxometalate is better dispersed in the direct synthesized samples than in the impregnated samples, and its structure remains intact after formation of the materials. The catalytic performance of the materials was tested using the esterification of n-butanol with acetic acid. The direct synthesized samples display excellent catalytic performance and reusability, which is superior to the impregnated samples. Under the optimized conditions, the conversion of n-butanol is 89.7%, and the selectivity of butyl acetate is nearly 100%.

Functionalized bimodal mesoporous silicas as carriers for controlled aspirin delivery

The bimodal mesoporous silica modified with 3-aminopropyltriethoxysilane was performed as the aspirin carrier. The samples’ structure, drug loading and release profiles were characterized with X-ray diffraction, scanning electron microscopy, N 2 adsorption and desorption, Fourier transform infrared spectroscopy, TG analysis, elemental analysis and UV-spectrophotometer. For further exploring the effects of the bimodal mesopores on the drug delivery behavior, the unimodal mesoporous material MCM-41 was also modified as the aspirin carrier. Meantime, Korsmeyer–Peppas equation f t = kt n was employed to analyze the dissolution data in details. It is indicated that the bimodal mesopores are beneficial for unrestricted drug molecules diffusing and therefore lead to a higher loading and faster releasing than that of MCM-41. The results show that the aspirin delivery properties are influenced considerably by the mesoporous matrix, whereas the large pore of bimodal mesoporous silica is the key point for the improved controlled-release properties.

Synthesis of Mesostructured Materials of Different Heteroatoms and Their Catalytic Performances for Styrene Epoxidation

FeS-1, VS-1 or CuS-1 precursors are loaded and highly dispersed on the surface of mesoporous materials SBA-15, MCM-41 or SiO2by impregnating method. The samples were characterized by X-ray diffraction, FT-IR spectroscopy, TEM and N2adsorption. Their catalytic performances for styrene epoxidation with anhydrous TBHP as an oxidant agent were studied. The results suggest that zeolite primary and secondary building units are highly dispersed on the samples and the samples have still retained mesoporous structure. All of the catalysts exhibit good catalytic activities, producing styrene oxide and benzaldehyde as the main products. Cu/SBA-15 shows high activity and selectivity, which are comparable with that of other samples. We find that, under the conditions of preferable precursors,n(TBHP)/n(styrene) =1.5, reaction temperature 80°C, and reaction time 2.0h, the conversion and yield of styrene epoxide reached 65.9% and 42.2%, respectively.

Solvent-free Mukaiyama-aldol condensation catalyzed by Ce–Al–MCM-41 mesoporous materials

MCM-41 samples containing Ce 4+ and Al 3+ in the network, designated as Ce x –Al–MCM-41 ( x = 0.0–0.04), were synthesized and characterized systematically. These samples exhibited higher catalytic activity for Mukaiyama-aldol condensations to produce β-hydroxy carbonyl compounds under the solvent free conditions, compared to the samples containing either of the two cations. The product yield was found to depend on the electron donating/withdrawing characteristics of reactant molecules being responsible for the observed trend. Series of solvents were also investigated but considerably high yield of aldol products (∼95%) could be achieved without using any solvents. In all the cases, the selectivity was found to be 100%, typical of such Mukaiyama-aldol condensations. The higher catalytic activity of Ce x –Al–MCM-41 is explained on the basis of certain new acid sites generated due to co-incorporation of Ce and Al cations.

Organosilicas and organo-clay minerals as sorbents for toluene

This study investigated the adsorption of toluene as a non-ionic organic contaminant by organosilicas and organo-clay minerals. Different organic surfactants were used to prepare a variety of MCM-41 molecular sieves at room temperature while cetyltrimethylammonium (CTMA) bromide was used to synthesize MCM-48 mesoporous material under hydrothermal conditions. Organo-clay minerals were synthesized under hydrothermal conditions using synthetic low-charge Na-fluorophlogopite micas with CTMA bromide as organic surfactant. All synthetic organosilicas and organo-clay minerals, the latter including those procured from two commercial sources were characterized by powder X-ray diffraction (XRD) and their toluene sorption properties were investigated. Among organosilicas, MCM-48 exhibited the highest distribution coefficient ( K d ) value of toluene (95 ± 9 L/kg). An organo-clay mineral, Nanomer® PGW montmorillonite modified with CTMA bromide (Nanomer® 1.28E) showed the maximum K d value (345 ± 22 L/kg) for toluene among all the studied organosilicas and organo-clay minerals. The organo-clay mineral nanocomposites were found to be superior to MCM-41 and MCM-48 organosilicas tested here and the former could find applications in remediating organic contaminants such as toluene from soil and groundwater.

Influence of the incorporated metal on template removal from MCM-41 type mesoporous materials

Al-modified MCM-41, La-modified MCM-41, and Ce-modified MCM-41 mesoporous materials were prepared with different molar ratios (Si/M = 10; 25; 50; 100 and 200) at room temperature. The materials were characterized using XRD, BET–BJH, and TG–DTA. The XRD showed four peaks, due to the ordered hexagonal array of parallel silica tubes, which could be indexed as (100), (110), (200), and (210), assuming a hexagonal unit cell. The surface area decreased as the concentration of the metal incorporated in the material increased. The thermal stability of the materials was around 650 °C. The CeO2 phase made the mass transfer process more difficult, hindering Hofmann degradation and favoring oxidation.

Catalytic effect of MCM-41 on the pyrolysis and combustion processes of tobacco. Effect of the aluminium content

The hydrothermal stability and the acidity of mesoporous MCM-41 materials are strongly related with their aluminium content. In this work, the influence of the concentration of Al on the textural and acidic properties of MCM-41, as well as on its role as tobacco additive for reducing the toxicity of the smoke generated in the smoking process has been studied. The results obtained show that the material with an intermediate content of aluminium presents acceptable hydrothermal stability, and higher values for the decrease of the yields of CO, CO 2, and the condensed and non-condensed products, thus showing the best results from the point of view of reducing the toxicity associated with the generation of toxic and carcinogenic compounds in tobacco smoke.

A novel application of mesoporous silica material for extraction of pesticides

The mesoporous silica material MCM-41 was prepared by the sol–gel method and characterized using X-ray diffraction (XRD), N 2 adsorption–desorption and thermogravimetric analysis. The material was tested for extraction of trichlorfon, pyrimethanil, tetraconazole, thiabendazole, imazalil and tebuconazole from mango fruit, with analysis using gas chromatography–mass spectrometry (GC/MS). In experiments carried out in triplicate, at a 1.0 mg/kg concentration level, recoveries using the MCM-41 sorbent were in the range 73–103%. Comparison of MCM-41 with commercially available silica gel showed that MCM-41 was a similar extracting phase for the pesticides investigated with a significant cost advantage over this conventional material.

Valorization of cellulose over metal supported mesoporous materials

Hydrolytic hydrogenation of bleached birch (betula) kraft pulp from a Finnish pulp mill into sugars and sugar alcohols was carried out in liquid phase in a batch mode under 20bar of hydrogen at 458K over metal supported mesoporous materials. Proton form of MCM-48 mesoporous material along with Pt on this support and Ru on carbon was tested. The conversion of cellulose and xylans present in the pulp varied depending on type of active sites, their number and metal. The yields of the main products, e.g. sugars, sugar alcohols and furfurals (xylose, glucose, xylitol, sorbitol, furfural, furfuryl alcohol and 5-hydroxymethyl furfural), varied depending on active sites, acidity, presence of metal and structure of the mesoporous material.

Incorporation of nano-sized mesoporous MCM-41 material used as fillers in natural rubber composite

The nano-sized mesoporous MCM-41 (without template), and the modification of MCM-41 (without template) were used to prepare natural rubber (NR) composites. The effects of coupling agents γ-aminopropyltriethoxysilane (KH-550), γ-methacryloxypropyltrimethoxysilane (KH-570), bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si-69), isopropyl tri-(dioctylpyrophosphate)titanate (NDZ-201) on the mechanical properties of the composites were also investigated. The results showed that the tensile properties of Natural rubber/mesoporous MCM-41 nanocomposite were improved as compared with those of NR compound. KH-570 had good effect on enhancing the overall properties of the composites. Scanning electron microscopy (SEM) observations revealed that the modified nano-sized MCM-41 material was well dispersed in the polymer matrix and the enhancement of the interface between the matrix and fillers was obtained.

Immobilization of a molybdenum complex with tetradentate ligand on mesoporous material MCM-41 as catalyst for epoxidation of olefins

Covalent grafting of MCM-41 with 3-chloropropyl trimethoxysilane and subsequent reaction respectively with acacdien and complexation with MoO2(acac)2 afforded MoO2acacdien@MCM-41. X-ray diffraction and nitrogen sorption analyses revealed the preservation of the textural properties of the support as well as accessibility of the channel system despite sequential reduction in surface area, pore volume and pore size. Elemental analyses showed nearly complete complexation of the supported ligands and the presence of 0.24 mmol molybdenum per gram of the catalyst. Epoxidation of cyclooctene, 1-hexene and 1-octene in the presence of MoO2acacdien@MCM-41 with tert-butyl hydroperoxide (TBHP) were carried out with relatively good conversion in the mild reaction conditions. morphology of product because the organic ligands around yttrium center act like a protecting agent to prevent agglomeration.

Selective conversion of trioses to lactates over Lewis acid heterogeneous catalysts

Substituted mesoporous MCM-41 materials and transition-metal-free oxides were prepared and tested as heterogeneous catalysts for the direct conversion of trioses to lactates. This is a reaction of growing interest in the field of production of valuable chemicals from renewable sources. Very high selectivity towards the desired lactate product was achieved with gallium oxide and with the ordered mesoporous material Sn-MCM-41. The latter catalyst was also very active and gave complete conversion after 6 h of reaction. The excellent catalytic performance of Sn-MCM-41 is ascribed to a combination of strong Lewis acid sites and mild Bronsted acid sites, as shown by monitoring pyridine adsorption on the catalyst surface with FT-IR spectroscopy. The catalytic results obtained with Sn-MCM-41 in the conversion of dihydroxyacetone to ethyl lactate are unsurpassed among the heterogeneous catalysts reported so far for this reaction.

One-Step Synthesis of Metal-Doped Mesoporous MCM-41 Materials and Their Application in Esterification Catalysis

Metals (Fe, Ti, Zr) were doped into mesoporous MCM-41 by a one-step method using cetyltriethylammonium bromide (CTAB) micelles with micellar solubilized metallocenes as templates. X- ray diffraction (XRD) and N2 adsorption-desorption isotherms show that after metallocene doping, M- MCM-41(T ) materials still preserved the ordered hexagonal structure and high BET surface area. Inductively coupled plasma atomic emission spectrometry (ICP-AES) indicated that the mass fractions of the metals in the corresponding samples are: 1.71% Fe in Fe-MCM-41(400), 0.95% Ti in Ti-MCM-41(550) and 0.81% Zr in Zr-MCM-41(550). All the M-MCM-41(T) materials showed a particular high catalysis effect for the esterification of acetic acid and n-butanol. The TOF of Fe-MCM-41(400) and Zr-MCM-41(550) were 55643 g·h - 1 ·g - 1 and 125320 g·h - 1 ·g - 1 , respectively, which is much higher than that of the corresponding pure metallocenes.