MCM-41 Materials Research Articles

Effect of ball milling on the structural and textural features of MCM-41 mesoporous material

This paper reports on the ball-milling process and its influence on the structural, textural and morphological features of mesoporous MCM-41 material. MCM-41 and the as-milled products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N2-adsorption, a field emission scanning electron microscope (FE-SEM) and a thermogravimetric analysis (TGA). The XRD showed that the mechanical treatment of MCM-41 in a ball mill leads to a gradual crystallinity loss with time until 2 h, and complete crystallinity loss was observed after 4 h of ball milling. N2 sorption measurements revealed a sharp surface area decrease as well as mesoporosity loss accompanying the milling process. The FE-SEM investigation demonstrated severe damage of the spherical morphology of MCM-41 upon milling for 8 h. Moreover, it was found that these structural, textural and morphological changes strongly affected the water content of the milled MCM-41 material.

Hydrodesulfurization of dibenzothiophene over PtMo/MCM-48 catalysts

Catalysts of platinum and molybdenum supported on MCM-48 materials were synthesized and characterized by XRD, XPS and N2 adsorption–desorption. Catalytic activity was evaluated in the model reaction of hydrodesulfurization of dibenzothiophene. Catalytic results showed high catalytic performance of ca. 95% for PtMo/MCM-48 catalyst with the formation of biphenyl (BP) as the main product, typical from direct hydrodesulfurization (DDS) pathway and ciclohexylbenzene (CHB) in a minor proportion from the hydrogenation prior to the desulfurization pathway.

Hydroconversion of n-hexadecane over bifunctional microporous and mesoporous model catalysts. Influence of pore architecture on selectivity

A model hydrocracking catalyst with a narrow and homogeneous distribution of mesopores of 3.2nm of diameter has been prepared by alumination of the surface of a siliceous MCM-48 material, loaded with platinum and evaluated in the hydroconversion of n-hexadecane. Compared to zeolite catalysts featuring a similar acidity but containing both micropores and mesopores, the Pt/Al-MCM-48 catalyst leads to the same overall activity but with higher hexadecane isomer yields and a symmetrical repartition of the cracked products, typical for primary central cracking, even at very high conversion levels. It is suggested that the unique behavior of the model Pt/Al-MCM-48 mesoporous hydroconversion catalyst is due to optimal sorption energetics of the primary reaction products in the network of uniformly distributed mesopores.

Fabrication of the Mesoporous Fe@MnO2NPs–MCM-41 Nanocomposite: An Efficient Photocatalyst for Rapid Degradation of Phenolic Compounds

Incorporation of nanoparticles in the extraframework of MCM-41 and its effect on the photocatalytic degradation of phenol has been studied. Mesoporous MnO2 nanoparticles (meso-MnO2NPs) are incorporated in situ into the extraframework of MCM-41 during its synthesis to obtain mesoporous MnO2NPs–MCM-41(MM) materials. Three samples of mesoporous MnO2NPs–MCM-41 have been prepared with Si/Mn ratios 10, 50, and 90. The sample with Si/Mn ratio 10 shows better textural properties compared to the other two samples. Formation of meso-MnO2NPs, reversible coordination of Mn ⇄ Si, and formation the Fe-modified MM-10 nanocomposite (mesoporous Fe@MM–10 NC) are the crucial steps involved in the present investigation. The role of CTAB, NH3, and (NH4)2S2O8 are the key ingredients for the fabrication of meso-MnO2NPs and mesoporous Fe@MM–10 NC. The materials are characterized by LXRD, N2 sorption, and HRTEM to evaluate the mesoporosity, morphology, and textural properties. Mesoporous Fe@MM–10 NC was treated as an efficient photocatalyst for degradation of phenolic compounds, an exemplary move. Nearly 100% degradation of concentrated phenolic compounds (100 mg L–1) has been achieved within 45 min by mesoporous 5Fe@MM–10 NC. Intraparticle mesoporosity, small particle sizes of the nanocomposite, the formation of a large number of •OH radicals, and the generation of high photocurrent are important factors for swift degradation of phenolic compounds by mesoporous 5Fe@MM–10 NC material.

PENGARUH WAKTU HIDROTERMAL DAN TMAOH DALAM SINTESIS LANGSUNG MCM-41

The MCM-41processing synthesis with variation time hydrothermal and TMAOH at direct synthesis process has been done. The synthesis of MCM–41 was used templating agents with cetiltrimetilammonium bromide (CTAB). The optimization of synthesis of MCM-41 was carried out to produce good material characteristics. Hydrothermal time variation performed in the synthesis of MCM-41 for 18 hours, 24 hours, 48 hours and 88 hours has been done. So the study of effect TMAOH was used CTAB/ TMAOH ratio: 1 and 1.25. The results showed that the 24- hour time hydrothermal was able to produce the good crystallinity with 100% relative crystallinity. However, the best stability of MCM-41 materials synthesized in hydrothermal time during the 48 hours. So the effect of TMAOH additions in the synthesis MCM-41 can bedecreased crystallinity of MCM-41.

Ultrafast Dynamics of Nile Red Interacting with Metal Doped Mesoporous Materials

We report on ultrafast studies of Nile Red (NR) interacting with MCM41 mesoporous materials doped by Al, Ga, Zr, and Ti in dichloromethane suspensions. The steady-state results showed a significant red shift and broadening of the diffuse transmittance and the emission spectra upon interaction with the MCM41-based materials. These findings are explained in terms of H-bonds with the host, different Brønsted/Lewis interactions with the matrix and formation of H- and J-aggregates, in addition to weakly and strongly adsorbed monomers. The pico- to nanosecond time-resolved data support this explanation, showing a significant shortening in the emission lifetimes where NR is interacting with metal-doped MCM41. The femtosecond dynamics of NR loaded into X-MCM41 (X = Si, Al, Ga) indicate that the charge-separated state (CS) is formed at the S1 state in ∼350 fs. For Zr- and Ti- MCM41 hosts the intramolecular charge transfer (ICT) occurs in less than 200 fs, and a subsequent electron injection to Ti or Zr trap states happens in ∼250 fs. Our studies reveal a strong interaction between the NR species and the framework of MCM41 materials at both the S0 and S1 states.

Effect of surface functionalization of cerium-doped MCM-48 on its catalytic performance for liquid-phase free-solvent oxidation of cyclohexane with molecular oxygen

Ce-doped MCM-48 (Ce-MCM-48) mesoporous molecular sieve was prepared hydrothermally and its surface was modified with organic groups or fluorine, and their physicochemical properties were characterized by XRD, low-temperature N2 adsorption, TEM, UV–visible and FT-IR spectroscopies, XPS and contact angle measurement. The results indicated that Ce species were highly dispersed on the MCM-48 materials as Ce3+ and Ce4+. After post-functionalization of Ce-MCM-48, the organic groups or fluorine species have been immobilized on the surface of Ce-MCM-48, but the chemical status of Ce species were hardly changed, and the post-functionalization improved the surface hydrophobicity of the Ce-MCM-48 sample. The catalytic activity testing for the oxidation of cyclohexane with molecular oxygen showed that, Ce-MCM-48 after post-functionalization exhibited the higher cyclohexane conversion and selectivity to cyclohexanol and cyclohexanone, 8.9% cyclohexane conversion with 91.2% selectivity to cyclohexanone and cyclohexanol could be achieved over the Ce-MCM-48 with F-modified catalyst, which was attributed to the proper modification of their surface properties including hydrophobicity and polarity. The F-modified catalyst also showed excellent reusability, and its catalytic performance has no obvious deterioration after being repeatedly used five times.

Applications of inorganic–organic mesoporous materials constructed by self-assembly processes for removal of benzo[k]fluoranthene and benzo[b]fluoranthene

The mesoporous materials MCM-41 and the functionalized inorganic–organic material p-aminobenzoic acid-MCM-41 (PABA-MCM-41) were used as adsorbents to remove the PAHs benzo[k]fluoranthene and benzo[b]fluoranthene from aqueous media. Both MCM-41 and PABA-MCM-41 exhibited the hexagonal mesostructures typical of the M41S family, as confirmed by SAXS, with type IV isotherms and type H1 hysteresis. The materials showed uniform mesopore size distributions, high surface areas, and thermal stability. Adsorption tests showed that for both mesoporous materials, the quantity adsorbed (q e) increased for higher initial PAH concentrations, and adsorption equilibrium was reached in around 90 min. The experimental kinetic data were fitted using the pseudo-second-order model, and the adsorption process could be described by the Langmuir isotherm. At higher temperatures, there were increases in the initial rates of adsorption and the kinetic constants for adsorption of the PAHs by PABA-MCM-41. The thermodynamic parameters indicated that the process was spontaneous, endothermic, and with a tendency toward disorder of the system at the adsorbent/adsorbate interface. The functionalization of MCM-41 increased the efficiency of adsorption of the PAHs by 44.5 and 32.0 % for benzo[k]fluoranthene and benzo[b]fluoranthene, respectively. Effect of contact time on adsorption of (a) B[k]F and (b) B[b]F by PABA-MCM-41. Conditions: 0.05 g of PABA-MCM-41, 5 mL of each PAH solution (concentration 200 µg L−1), temperature of 25 °C, contact time of 300 min, and agitation at 150 rpm.

CO2 adsorption performance of different amine-based siliceous MCM-41 materials

A series of amine-based adsorbents were synthesized using siliceous MCM-41 individually impregnated with four different amines (ethylenediamine (EDA), diethylenetriamine (DETA), tetraethylenepentamine (TEPA) and pentaethylenehexamine (PEHA)) to study the effect of amine chain length and loading weight on their CO2 adsorption performances in detail. The adsorbents were characterized by FT-IR, elemental analysis, and thermo-gravimetric analysis to confirm their structure properties. Thermo-gravimetric analysis was also used to evaluate the CO2 adsorption performance of adsorbents. Longer chain amine-based materials can achieve higher amine loadings and show better thermal stability. The CO2 adsorption capacities at different temperatures indicate that the CO2 adsorption is thermodynamically controlled over EDA-MCM41 and DETA-MCM41, while the adsorption over TEPA-MCM41 and PEHA-MCM41 is under kinetic control at low temperature. The chain length of amines affects the CO2 adsorption performance and the adsorption mechanism significantly. The results also indicate that CO2 adsorption capacity can be enhanced despite of high operation temperatures, if appropriate amines (TEPA and PEHA) are applied. However, adsorbents with short chain amine exhibit higher adsorption and desorption rates due to the collaborative effect of rapid reaction mechanisms of primary amines and less diffusion resistance of shorter chain length amines.

Production of silver-silica core-shell nanocomposites using ultra-short pulsed laser ablation in nanoporous aqueous silica colloidal solutions

Ultra-short pulsed laser ablation of materials in liquid has been demonstrated to be a versatile technique for nanoparticles production. In a previous paper, it has been described, for the first time, how by laser ablation in a liquid system, silver nanoparticles can be loaded onto SBA-15 and MCM-41 supports which show promising catalytic properties for the oxidation of Volatile Organic Compounds (VOCs). The aim of the present research is to demonstrate the formation of stable silver-silica core-shell nanoparticles by direct laser ablation (Ti:Sa; 800 nm; pulse duration: 120 fs; repetition rate: 1 kHz, pulse energy: 3.6 mJ, fluence: 9 J cm − 2) of a Ag target submerged in a static colloidal solution of MCM-41 or SBA-15 silica nanoporous materials. In previous studies, it was discovered that a side and negligible product of the laser ablation process of silver performed in water-silica systems, could be related to the formation of silver-silica core-shell nanoparticles. In order to emphasize this side process some modifications to the laser ablation experimental set-up were performed. Among these, the most important one, in order to favor the production of the core-shell systems, was to keep the liquid silica suspension firm. The laser generated nanomaterials were then analyzed using TEM morphologic characterization. By UV–vis absorption spectra the observed features have been related to components of the colloidal solution as well as to the number of the incident laser pulses. In this manner characterizations on both the process and the resulting suspension have been performed. Significant amount of small sized silver-silica core-shell nanoparticles have been detected in the studied systems. The size distribution, polydispersivity, UV–vis plasmonic bands and stability of the produced silver-silica core-shell nanocomposites have been related to the extent of damage induced in the nanoporous silica structure during the ablation procedure adopted here. In presence of SBA-15 the silver-silica core-shell nanoparticles observed by TEM are smaller and more homogeneously dispersed if compared with the core-shell system obtained when the MCM-41 mesoporous silica was used. The outcomes show that the choice of the mesoporous silica material can affect the silica shell thickness in addition to the Ag NPs size distribution. With this regard, TEM images evidence that in MCM-41 the silver-silica core-shell nanostructures display a silica layer thickness between 1–10 nm; conversely, for SBA-15, the silver-silica core-shell nanoparticles are finely dispersed and the silica shell shows, when present, an average thickness of about 5 nm.

Adsorption of Cr(III) ions using 2-(ureylenemethyl)pyridine functionalized MCM-41

Modified MCM-41 material with uniform meropore channels was prepared by surfactant-directed synthesis strategy and post functionalized with 3-(triethoxysilyl)propyl isocyanate (ICPES). By utilizing the reaction between –NCO group of ICPES and –NH2 group of 2-picolylamine in acetonitrile, the chelating ligand, 2-(ureylenemethyl)pyridine, has been successfully immobilized over MCM-41 (UMP-MCM-41) without destroying the mesoporous structure. The synthesized materials show very good mesoporosity and long range order. The ability of removing chromium from water and artificial seawater by using the UMP-MCM-41 mesoporous material was explored. The synthesized material showed good adsorption ability for Cr(III) ions from water and artificial seawater with selectivity of 36 and 64 %, respectively, in the presence of interfering metal ions such as Zn(II), Cd(II), Co(II), and Cu(II). In order to disclose the adsorption ability of the material from single metal ion solution for Cr(III) ion, factors such as effect of pH, stirring time, initial ion concentration and presence of ethanol in adsorption medium were also explored. Further the experiments revealed that the UMP-MCM-41 is giving maximum adsorption at pH 6. The adsorption equilibrium has been attained within 5 h with 84 % adsorption. Moreover, the presence of ethanol in the adsorption medium enhances the amount of adsorption.

Influence of frost damage and sample preconditioning on the porosity characterization of cement based materials using low temperature calorimetry

Low temperature calorimetry (LTC) can be used to study the meso-porosity of cement based materials. The influence of frost damage on the meso-porosity determination by LTC was explored on a model material MCM-41 and two cement pastes by conducting repeated cycles of freezing and melting measurements. The results indicate that the pressure generated during freezing and melting measurements has little impact on the pore structure of the powder MCM-41 samples. As for the studied cylinder samples of cement pastes, frost damage probably took place and it changed the pore connectivity while it had limited effect on changing the interior size distribution of the meso-pores. The analysis of the freezing and melting behavior of the pore liquid of cement based materials is complicated by the presence of ions. The freezing and melting behavior of the pore solution of cement paste samples preconditioned in either a small amount or a big amount of saturated limewater was compared. The results suggest that either the preconditioning in a big amount of limewater does not change the ionic concentration of the pore solution very much or the possible leaching of ions from cement hydrates during the preconditioning has limited influence on the freezing and melting behavior of the pore solution in the studied cement paste samples.

Long-term antifungal activity of volatile essential oil components released from mesoporous silica materials

Antimicrobial volatile substances from plants have become known as a suitable alternative to synthetic pesticides and food preservatives. The study tested the antifungal activity against Aspergillus niger of seven volatile essential oil components from plants—allyl isothiocyanate, carvacrol, cinnamaldehyde, diallyl disulfide, eugenol, thymol, and thymoquinone. To provide long-term effects by controlled release and ease of application, these substances were encapsulated into mesoporous silica material MCM-41 and then compared to the effects of pure substances. Significant antifungal activity was verified in five out of the seven tested substances. These results were correlated with the evaporation rate of pure and encapsulated substances. It has been proven that by encapsulating selected volatiles, excluding sulfur compounds, their long-term effectiveness is ensured by controlled release and easy handling, with positive effects for their antifungal activity.

Matrix effect of montmorillonite and MCM-41 matrices on the antibacterial activity of Ag2CO3 nanoparticles

The activity and stability of nanoparticles (NPs) is known to be influenced by the nature of the supports used for their immobilization. In this study, two matrices, MCM-41 and montmorillonite (Mt) clay, were used for the incorporation of Ag2CO3 nanoparticles. MCM-41 material is a neutral matrix with high surface area, high pore volume and without the complications of a network. Mt is an ionic support with a layered structure. Non-simultaneous support decoration with antibacterial NPs by a precipitation method was used for the synthesis of bulk Ag2CO3 and nanocomposites. The two nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet–visible diffuse reflectance spectroscopy (DRS). The powder X-ray diffraction showed intercalation of Ag2CO3 nanoparticles into the clay interlayer space but nanoparticles have located on the surface area of mesoporous materials. The diffuse reflectance spectra indicated a strong surface plasmon resonance (SPR) absorption band in the visible region, resulting from metallic Ag nanoparticles. The two nanocomposites contained both Ag2CO3 and Ag. But the metallic silver content in MCM-41 mesoporous material was lesser in Mt clay. However, their antibacterial activities varied significantly. The antibacterial testing results demonstrated that the Ag2CO3-MCM-41 exhibited an antibacterial activity higher than that of Ag2CO3-Mt against Escherichia coli.

ChemInform Abstract: Catalysis via Sol‐Gel Acid Silicas: An Important Chemical Technology for 2nd Generation Biorefineries

AbstractReview: [57 refs.

Synthesis of Nanoporous Materials Al-MCM-41 from Natural Halloysite

Nanoporous materials Al -MCM-41 with varying Si / Al molar ratios have been successfully synthesized from natural clay mineral halloysite nanotubes (HNTs). Hydrothermal treatment of acid-pretreated HNTs and NaOH solution resulted in the one-step synthesis of final nanoporous products by using surfactant. The effects of Si / Al molar ratios (7.7, 61.0 and 176.5) on the surface area, porosity and degree of structural order of Al -MCM-41 materials have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption–desorption measurements and Fourier transform infrared (FTIR) spectra techniques. The results indicated that Si / Al molar ratio had important effect on the characteristics of nanoporous materials, and Al -MCM-41 with an intermediate Si / Al molar ratio of 61.0 exhibited excellent characteristics with high degree of order, high surface area (S BET ) of 1033 m2/g and pore volume of 0.92 mL/g.

Influence of the Synthesis Time in the Textural and Structural Properties of Ni-Containing Mesoporous Materials

MCM-41 materials have been synthesized by hydrothermal synthesis, and the influence of the synthesis time variation on the structural and textural properties of the final solids was studied. Nickel-modified samples were synthesized with a molar ratio Si/Ni of 60 and increased days of synthesis from 0 to 7 days. The structures obtained were characterized by X-ray diffraction (XRD) and UV-vis diffuse reflectance (UV–Vis DRS) spectroscopy.XRD patterns of samples are typical of MCM-41 structure, which improves with increasing the time of hydrothermal treatment. XRD and UV–vis studies revealed that the short synthesis times do not allow the proper incorporation of nickel in the structure. It was corroborated that, the synthesis time has an important influence on the properties of mesoporous material modified with Ni.

Ion exchange growth of Zinc Sulfide quantum dots in aqueous solution

We report the growth by ion exchange synthesis of ZnS nanoparticles in MCM-41 matrices using Zn (CH3COO)2 and Na2S starting sources. The final product (ZnS/MCM-41) was characterized by X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectrometry (IR) and UV-vis spectroscopy. Its crystalline structure and morphology was studied by XRD and scanning electron microscopy. Exciton absorption peaks at higher energy than the fundamental absorption edge of bulk ZnS indicates quantum confinement effects in nanoparticles as a consequence of their small size.

Transition metal/metal oxide modified MCM-41 for pollutant degradation and hydrogen energy production: a review

Metal/metal oxide modified MCM-41 materials are suitable for various catalytic applications. The high surface area, mesoscopic pore size and tunable pore volume of the materials play a key role in enhancing the catalytic activity.

Pd–Ti-MCM-48 cubic mesoporous materials for solar simulated hydrogen evolution

A facile synthetic method (in as little as four hours) for simultaneously loading high amounts of titania (Si/Ti = 3) and Pd0 co-catalyst (0.1 wt.% per gram of total catalyst) in cubic mesoporous MCM-48 material was developed at room temperature. The solar simulated photocatalytic hydrogen evolution from photocatalysts containing Pd0 and TiO2 nanoclusters in periodic cubic MCM-48 and aperiodic mesoporous silica was compared. The results indicate that the periodicity of the mesoporous silica support, the oxidation state of Pd, the location and dispersion of Pd0 have a significant impact on the photocatalytic activity. Periodic cubic MCM-48 mesoporous silica containing Pd0 in close contact with titania exhibit superior hydrogen evolution rates compared to Pd0-TiO2 containing aperiodic mesoporous silica. The highly ordered and open three-dimensional mesoporous cubic MCM-48 support has high surface area and facilitate good dispersion and close contact of titania and Pd0. At very low loadings of 0.1 wt.% of Pd, hydrogen yield was found to be 560 μ mol h−1, which is among the highest reported in the literature for Pd0 containing TiO2 based materials under solar simulated conditions. The results suggest that the pore architecture of the support is also an important parameter that governs the photocatalytic activity. In addition, the Pd0-mesoporous materials in general possess higher activity than Pd2+ containing mesoporous materials. The photocatalysts were extensively characterized by a variety of techniques such as powder X-ray diffraction (XRD), nitrogen sorption analysis, transmission and scanning electron microscopic studies, photoluminescence, diffuse reflectance spectroscopy (DRS), CO Chemisorption, and X-ray photoelectron spectroscopy (XPS).