Siliceous MCM-41 Research Articles

Cerium Containing Siliceous MCM-22: Preparation, Characterization and its Potential Application towards Oxidation of Isoeugenol to Vanillin

Aim: Preparation of cerium containing silicious MCM-22 zeolite material and explore its application for biomass conversion. Background: Zeolites and zeolite like microporous materials are well known as potential heterogeneous acid catalysts, whose discovery has made a significant impact in the petroleum, petrochemical and fine chemical industries. In recent years, zeolite, zeolites like molecular sieves, and inorganic oxide-based heterogeneous catalysts played a significant role in biomass valorization to receive value-added chemicals. Thus we focused on utilization of zeolite for biomass transformation. Objective: Preparation of cerium containing aluminium-free siliceous MCM-22 (AF-CeMCM- 22) by the in-situ hydrothermal method and explore its importance on biomass transformation. Methods: Powder XRD, FTIR and BET surface area were used to study the microstructure of the samples. SEM and FE-SEM were used to study morphology, TGA was used to evaluate the thermal stability, and 29Si NMR and DR-UV-Vis were used to study the environment of the MCM-22 framework. The prepared and confirmed material was used for the oxidation of levulinic acid over the liquid phase setup. Gas chromatography was used to evaluate the catalytic study, such as conversion and selectivity; also, GCMS was used for the confirmation of products. Results: The powder XRD pattern showed well distinguish MCM-22 framework structure with a uniform dispersion of cerium ions in the MCM-22 framework. SEM image of the cerium AFCeMCM- 22 showed platelet structure having flaky spherical morphology and the surface area in the range of about 175 m2g−1. 29Si NMR and DR-UV-Vis studies confirmed the well-condensed nature of the MCM-22 silica framework and the cerium ions present in both tetrahedral and octahedral extra-framework environments. Conclusion: The catalyst developed in the present studies was found to be a promising catalyst for the conversion of iso-eugenol to vanillin at 60°C, using H2O2 oxidant with the vanillin selectivity of 71 %.

The effect of Lewis acidity of tin loading siliceous MCM-41 on glucose conversion into 5-hydroxymethylfurfural

The effect of Lewis acidity of tin loading siliceous MCM-41 on glucose conversion into 5-hydroxymethylfurfural

Green synthesis and characterization of silicate nanostructures coated with Pluronic F127/gelatin for triggered drug delivery in tumor microenvironments

Thermo-/pH-sensitive nanocomposites based on mesoporous silicate MCM-41 (MSNCs) derived from rice husk ash were synthesized and characterized. MSNCs were coated with thermo-/pH-sensitive Pluronic® F127 and gelatin to form MSNCs@gp nanocomposites, serving as carriers for controlled release of the anticancer drug doxorubicin (Dox). The in vitro and in vivo antitumor efficacy of MSNCs@gp-Dox against liver cancer was evaluated. Fourier-transform infrared (FTIR) spectra confirmed the silica nature of MSNCs@gp by detecting the Si-O-Si group. Under acidic microenvironments (pH 5.4) and 42 °C, MSNCs@gp-Dox exhibited significantly higher Dox release (47.33 %) compared to physiological conditions. Thermo-/pH-sensitive drug release (47.33 %) was observed in simulated tumor environments. The Makoid-Banakar model provided the best fit at pH 7.4 and 37 °C with a mean squared error of 0.4352, an Akaike Information Criterion of 15.00, and a regression coefficient of 0.9972. Cytotoxicity tests have demonstrated no significant toxicity in HepG2 cells treated with various concentrations of MSNCs@gp, while MSNCs@gp-Dox induced considerable cell apoptosis. In vivo studies in nude mice revealed effective suppression of liver cancer growth by MSNCs@gp-Dox, indicating high pharmaceutical efficacy. The investigated MSNCs@gp-based drug delivery system shows promise for liver cancer therapy, offering enhanced treatment efficiency with minimal side effects.

Properties of CrOx/MCM-41 and Its Catalytic Activity in the Reaction of Propane Dehydrogenation in the Presence of CO2

Propylene is an important raw material for the production of many valuable compounds, especially polypropylene, the consumption of which continues to grow every year. The reaction of oxidative dehydrogenation of propane, where carbon dioxide is used as a mild oxidant, is a promising method for producing propylene. At the same time, the problem of utilization of greenhouse gas CO2 is partially solved. The synthesis and analysis of the physicochemical properties of mesoporous silicate MCM-41 and supported catalysts CrOx/MCM-41 prepared on its basis were carried out. These catalysts were prepared using incipient wetness impregnation. The support and catalysts were characterized by the methods of low-temperature nitrogen adsorption, TG-DTA, XRD, SEM, TPR-H2, UV/Vis diffuse reflectance spectroscopy, and small-angle X-ray scattering. It is shown that chromium is present in the samples simultaneously in the form of Cr3+ and Cr6+. The catalytic tests were performed in the range of 550–700 °C. The highest selectivity for propylene was observed for the 5%Cr/MCM-41 catalyst and was 76% at a temperature of 650 °C with a propane conversion of 20%. The deposited catalysts Cr/MCM-41 and Cr/SiO2 (Acros) were compared. The propylene selectivity for the MCM-41-supported catalyst was ~1.5 times higher than that for the SiO2-supported catalyst.

Toluene/water separation using MCM-41/ PEBA mixed matrix membrane via pervaporation process

Pervaporation (PV) process with the mixed matrix membrane (MMM) is a feasible and cost-effective alternative to conventional volatile organic compounds (VOC) removal methods. In this study, the mesoporous silicate MCM-41 was synthesized by a new and rapid sol-gel method and incorporated into the polyether-block-amide (PEBA-2533) polymer network. Prepared MMM and MCM-41 were characterized by XRD, FESEM, TEM, AFM, TGA, DSC, FTIR, contact angle, and mechanical analyses. Effect of MCM-41 calcination on the performance of MMM for toluene/water solution separation was studied using a PV setup. Experiments were conducted to determine the effects of MCM-41 loading, feed concentration, and feed temperature on total flux, component flux, separation factor, and pervaporation separation index (PSI). For a 300 ppm toluene aqueous solution at 30 °C, the separation factor, from 44.4 to 203.7 (358.7% increment), and toluene flux, from 3.9 to 10.5 g m−2 h−1 (163.8% increment), were improved by using 7.5% uncalcined MCM-41 loading. The PSI value of this sample was attained at 67290 g m−2 h−1, which was 412% higher than that of a neat PEBA membrane (13142 g m−2 h−1).

Mesoporous silica based copper catalytic materials for potential deNOx application: Synthesis and characterization

In this work hybrid catalytic porous materials were prepared and investigated with respect to their structural and functional properties. The development of the catalytic systems was performed through a modified polyol route utilizing two mesoporous siliceous templates, MCM-41 & MCF as substrates, whereas copper was used as the active component. Microwave irradiation was applied as heating source and the size of as-formed NPs along with their dispersion on selected porous hosts were effectively controlled through fine tuning of the reaction parameters. Characterization results reveal the successful preparation of Cu NPs of approximately 16 nm diameter in both studied composites. DeNOx catalytic activity results performed under stoichiometric conditions demonstrate an enhanced efficiency reaching 37–42% maximum NO conversion by CO at moderate temperatures (~400 °C). However, a more detailed study is required for an in depth comprehension of the synthetic parameters that will enable the production of supported Cu NPs with desirable particle size distribution and enhanced catalytic activity.

Dynamics of water confined in mesopores with variable surface interaction.

We have investigated the dynamics of liquid water confined in mesostructured porous silica (MCM-41) and periodic mesoporous organosilicas (PMOs) by incoherent quasielastic neutron scattering experiments. The effect of tuning the water/surface interaction from hydrophilic to more hydrophobic on the water mobility, while keeping the pore size in the range 3.5 nm-4.1 nm, was assessed from the comparative study of three PMOs comprising different organic bridging units and the purely siliceous MCM-41 case. An extended dynamical range was achieved by combining time-of-flight (IN5B) and backscattering (IN16B) quasielastic neutron spectrometers providing complementary energy resolutions. Liquid water was studied at regularly spaced temperatures ranging from 300 K to 243 K. In all systems, the molecular dynamics could be described consistently by the combination of two independent motions resulting from fast local motion around the average molecule position and the confined translational jump diffusion of its center of mass. All the molecules performed local relaxations, whereas the translational motion of a fraction of molecules was frozen on the experimental timescale. This study provides a comprehensive microscopic view on the dynamics of liquid water confined in mesopores, with distinct surface chemistries, in terms of non-mobile/mobile fraction, self-diffusion coefficient, residence time, confining radius, local relaxation time, and their temperature dependence. Importantly, it demonstrates that the strength of the water/surface interaction determines the long-time tail of the dynamics, which we attributed to the translational diffusion of interfacial molecules, while the water dynamics in the pore center is barely affected by the interface hydrophilicity.

Mesoporous Zeolitic Materials (MZMs) Derived From Zeolite Y Using a Microwave Method for Catalysis.

Mesostructured zeolitic materials (MZMs) with relatively high acidity in comparison with the mesoporous siliceous MCM-41 were prepared via an efficient, mild, and simple post-synthetic treatment of Y zeolite facilitated by microwave irradiation, i.e., microwave-assisted chelation (MWAC). The disordered mesoporous aluminosilicates materials (DMASs) of MZM were created from Y zeolite in the absence of using mesoscale templates. The prepared DMASs showed the good mesoporous features with the mesopore area and volume of ~260 m2 g−1 and ~0.37 cm3 g−1, respectively, and with the mesopore sizes distributed in a range of 2–10 nm. MZMs possess a total acidity of about 0.6 mmol g−1 and exhibited comparatively superior catalytic activity to the parent Y zeolite and MCM-41 in the vapor phase catalytic dealkylation of 1,3,5-triisopropylbenzene (TiPBz) and liquid phase catalytic aldol condensation of benzaldehyde with 1-heptanal. Although the yield loss was inevitable for preparing MZMs using the MWAC method, the preliminary economic analysis of the preparation cost of MZMs showed the promise. Additionally, a comprehensive comparison of the state-of-the-art mesoporous materials concerning their sustainable aspects was made, showing that MZMs are promising mesoporous materials for further development and functionalization for catalysis.

Study on the preparation of amine-modified silicate MCM-41 adsorbent and its H2S removal performance

A series of APTMS ((3-aminopropyl)trimethoxysilane)-modified silicate MCM-41 adsorbents ( x-APTMS/MCM-41, x is the volume of APTMS per 1 g of silicate MCM-41) with different APTMS contents was prepared, and the effects of APTMS content on the desulfurization performance of the APTMS/MCM-41 adsorbents were studied in a fixed adsorption bed using H2S and N2 mixture as a model gas. The as-prepared adsorbents were characterized by X-ray diffraction analysis, N2 adsorption–desorption, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The results showed that all the APTMS-modified x-APTMS/MCM-41 adsorbents retained the mesoporous silica structure of MCM-41. The Brunauer–Emmett–Teller-specific surface area of x-APTMS/MCM-41 increased slightly with increasing x at first and then decreased with further increasing APTMS content. The H2S removal performances of x-APTMS/MCM-41 adsorbents decreased in the order 0.6-APTMS/MCM-41 > 0.7-APTMS/MCM-41 > 0.5-APTMS/MCM-41 > 0.4-APTMS/MCM-41 > 0.8-APTMS/MCM-41. At x = 0.6, the maximum H2S removal rate of 54.2% and H2S saturated capacity of 134.4 mg g−1 were observed. The regeneration experiment of 0.6-APTMS/MCM-41 adsorbent after three times regeneration at 423 K for 3 h in nitrogen confirmed that it possessed a good regenerability.

Mesoporous silica MCM-41, SBA-15 and derived bridged polysilsesquioxane SBA-PMDA for the selective removal of textile reactive dyes from wastewater

Treatment methodologies and precautionary measures are the topmost priority for sustainable development. Mesoporous silicates MCM-41, SBA-15 and its hybrid SBA-PMDA were directly employed to remove the textile reactive dyes from water at room temperature and neutral pH. These nanostructured materials were prepared and characterized by using FTIR spectroscopy, Nitrogen adsorption/desorption, NMR spectroscopy, X-rays diffraction, Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and Zeta potential. The cationic reactive dye brilliant green (BG) removal capacity of silicas SBA-15 and MCM-41 was found 119.0 mg g−1 133.20 mg g−1, respectively and zero affinity was observed for anionic dye reactive blue (RB 15) by these materials. In comparison, modified silica with PMDA bridged polysilsesquioxane SBA-PMDA, showed 25.66 mg g−1 of removal capacity for anionic dye RB 15. Kinetic studies showed that about 70% of the dye was removed within 4–5 h. To predict the system efficiency, the experimental data was treated with mathematical models such as Langmuir, Freundlich, Sips and Dubinin–Radushkevich isotherms, pseudo-first-order and pseudo-second-order. The obtained results suggest that nanostructured silicates could be simple, efficient, inexpensive and convenient adsorbents for the direct and selective removal of reactive dyes from water at room temperature.

Zn supported on titania-doped mesoporous silicate MCM-41 as efficient catalysts for acetylene hydration

A highly efficient grafting method to synthesise Ti-doped MCM-41 mesoporous supports and their respective Zn catalysts was investigated.

Generation of gold nanoclusters encapsulated in an MCM-22 zeolite for the aerobic oxidation of cyclohexane.

In this work, we will report the generation of Au clusters in a purely siliceous MCM-22 zeolite. The catalytic properties of these Au clusters have been tested for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA-oil). The Au clusters encapsulated in the MCM-22 zeolite are highly active and selective for the oxidation of cyclohexane to KA-oil, which is superior to Au nanoparticles on the same support. These results suggest that Au clusters are highly active for the activation of oxygen to produce radical species.

Resin-Based Materials with Chlorhexidine-Loaded MCM-41: Surface Characteristics, Drug Release, and Antibiofilm Activity.

Poly(methyl methacrylate) resins containing chlorhexidine diacetate (CHX)-loaded mesoporous silicate MCM-41 have the ability to prevent Candida biofilm adhesion and growth over time. With the aim of increasing knowledge of the drug release and surface properties of these materials and their relationship with antibiofilm activity, in this paper an acrylic-based resin containing CHX-loaded spherical and narrow size silanized MCM-41 was prepared. Resins containing CHX but no filler were prepared as well and compared. Samples were characterized for polymerization degree, water sorption, and drug release. The sample capacity of inhibiting Candida biofilm adhesion and formation over time was evaluated. All samples were able to reduce the Candida biofilm mass over time. The resin containing CHX loaded into silanized MCM-41 mesopores resulted in less activity during the first 4 h but was able to maintain antibiofilm activity for a longer time. This effect was correlated to the prolonged CHX release and to the sample surface modifications observed after treatment with water and artificial saliva, evaluated by X-ray photoemission spectroscopy, scanning electron, and atomic force microscopies.

Advanced and green ozonation process for removal of clofibric acid in water system: Preparation and mechanism analysis of efficient copper-substituted MCM-48

This paper described the use of modified mesoporous molecular sieves to remove clofibric acid through catalytic ozonation. The mesoporous silicate MCM-48 and Cu-substituted MCM-48 (Cu-MCM-48) with different Cu contents were prepared by hydrothermal method in surfactant solutions. The catalyst was characterized by XRD, UV–vis, and XPS, indicating that copper was successfully doped in the framework of three-dimensional MCM-48 and Cu-O-Si linkage was formed in Cu-MCM-48 samples. The SEM and TEM graphs exhibited that the cubic arrays were highly homogeneous and well-ordered. However, high Cu contents destroyed the basic structure of pure MCM-48 and metallic nanometric clusters accumulated on the surface of samples. The degradation and mineralization of clofibric acid (CA) were investigated with the presence of Cu modified MCM-48 (Cu-MCM-48) during ozonation. When the molar ratio of Si/Cu was 60, TOC removal reached 41.1% at 60 min oxidation time. The catalytic mechanism of Cu60-MCM-48 was also investigated by using density functional theory (DFT). The radical quenching experiments revealed that hydroxyl radical (OH) and superoxide radical (O2−) were the reactive oxygen species (ROS) for CA degradation. Cu60-MCM-48 showed favorable removal efficiency in the mild acid condition and remained high Lewis acid amount after reactions according to the results of Fourier transformer infrared (FTIR) of adsorbed pyridine. Furthermore, the possible reaction routes including C1O and C4Cl bonds destroying and aromatic ring cleavage were proposed by HPLC-MS. 2-hydroxyisobutiric acid was the main intermediate in ozonation process with the presence of Cu60-MCM-48.

Synthesis of MCM-41 nanoparticles from stem of common reed ash silica and their application as substrate in electrooxidation of methanol

In this work, stem of common reed ash (SCRA) is introduced as a new source of silica in the preparation of mesoporous materials. Mesoporous silicate MCM-41 nanoparticles were synthesized hydrothermally using sodium silicate prepared from SCRA as a silica source. The characterization of MCM-41was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N $$_{2}$$ adsorption/desorption (BET) and transmission electron microscopy (TEM). SEM shows that MCM-41 nanoparticles are sphere-like with size in the range of 30–50 nm with some degree of agglomeration. TEM image of the synthesized sample shows the open framework structure of MCM-41. A type IV isotherm can be observed from adsorption/desorption curves, which is the characteristic of mesoporous materials. The prepared MCM-41 nanoparticles were used as substrate to facilitate the oxidation of methanol through the modification with an electroactive species. The modification was achieved by impregnation of MCM-41 pores with $$\hbox {Ni}^{2+}$$ ions (Ni-doped MCM-41). A modified carbon paste electrode (CPE) was prepared by mixing Ni-doped MCM-41 with carbon paste (NiMCM-41CPE). Cyclic voltammetry of NiMCM-41CPE shows an increment in current density of methanol oxidation in comparison with CPE in alkaline solution. Moreover, a decrease in the overpotential of methanol oxidation occurred on the surface of modified electrode. The effects of some parameters such as scan rate and methanol concentration are also investigated on the behaviour of NiMCM-41CPE. Also, the heterogeneous electron transfer rate for the catalytic reaction (k) of methanol is calculated.

Water Transport in Periodic Mesoporous Organosilica Materials

Water transport in periodic mesoporous organosilicas (PMOs) was studied using pulsed field gradient NMR. A series of isogeometric PMO materials with different chemical compositions of the pore walls were investigated and compared to a purely siliceous MCM-41 material with an identical pore size. The long-range water diffusivities measured were found to be largely controlled by the macroscopic textural properties of the materials, namely, by the particle geometry and a degree of the particle agglomeration, and by thermodynamic conditions under which the experiments were performed. It is shown that their combined effect caused water molecules either to propagate predominantly along the capillary-condensed water domains or to frequently alternate their trajectories between these domains and the water phase in the interparticle space. Because the transport rates in these two regimes differ substantially, it is suggested that by a purposeful choice of the PMO composition, both the long-range transport rate and...

Selective oxidation of CO in the presence of propylene over Ag/MCM-41 catalyst

Ag/MCM-41 catalyst is prepared by impregnation technique and characterized by low-temperature N2 sorption, XRD, TPR and TEM methods. The ordered structure of mesoporous silicate MCM-41 is used as a nanoreactor to synthesize and stabilize small Ag nanoparticles. Two types of Ag particles are shown to form in Ag/MCM-41 catalyst: ultrasmall (<3 nm) inside pores of support and large (4–8 nm) on the external surface of the MCM-41. Catalytic tests in oxidation mixture containing 1% CO and 1% propylene show that Ag/MCM-41 catalyst can be used for selective oxidation of CO in the presence of propylene from 91 °C (CO conversion > 98%) to 217 °C (conversion of propylene < 5%). The catalyst can be used for purification of hydrocarbons from CO by selective oxidation of second.

Influence of gel composition and microwave-assisted hydrothermal time in MCM-41 synthesis

This work reports syntheses of siliceous mesoporous MCM-41 by microwave-assisted hydrothermal process with CTAB:SiO2 ratio from 0.025 to 0.400 and NaOH:SiO2 ratio of 1.0, 1.3 and 2.0. From XRD results, the MCM-41 phase increases with CTAB:SiO2 ratio until 0.300. Another amorphous phase is produced from the gel with CTAB:SiO2 ratio of 0.400. MCM-41 from the optimal CTAB:SiO2 ratio (0.300) has surface area of 1138 m2 g−1 and pore wall thickness of 12.70 Å. With CTAB:SiO2 ratio fixed at 0.300, the optimal NaOH:SiO2 ratio is 1.0. Then, an influence of microwave-assisted hydrothermal time is studied from 0 to 180 min on the gels with CTAB:SiO2 ratio of 0.300 and NaOH:SiO2 ratio of 1.0. All MCM-41 samples have essentially similar XRD pattern, surface area and pore-wall thickness. However, their TEM images indicate that the longer hydrothermal time produced MCM-41 with the less defects.

PH-insusceptible cobalt-manganese immobilizing mesoporous siliceous MCM-41 catalyst for ozonation of dimethyl phthalate

Mesoporous siliceous MCM-41 immobilized with Co and Mn metal ions (Co-Mn-MCM-41) was synthesized using a hydrothermal method. The structural regularity and the valence states of the metal species were measured by X-ray diffractometer and X-ray photoelectron spectrometer. The resultant bimetallic Co-Mn-MCM-41 catalyst was tested for the degradation of dimethyl phthalate (DMP) via a catalytic ozonation mechanism, demonstrating that the catalytic properties of Co-Mn-MCM-41 catalyst significantly accelerated the ozonation process. Total organic carbon (TOC) and DMP removal efficiency reached 94% and 99.7% at 15min under the optimal conditions. The oxidation pathways were proposed after identifying the intermediate products from ozonation using a gas chromatography-mass spectrometer. The enhanced catalytic reactivity was attributed to the highly-dispersive cobalt and manganese species in MCM-41 scaffolds, which promoted the ozone decomposition and hydroxyl radicals’ generation in catalytic ozonation and accelerated the degradation of DMP. Bimetallic Co-Mn-MCM-41 catalyst remained stable in mild acidic conditions and continued to show high activity after repeated runs.

Influence of Aluminum Addition in the Framework of MCM-41 Mesoporous Molecular Sieve Synthesized by Non-Hydrothermal Method in an Alkali-Free System

Purely siliceous MCM-41 and Al-containing MCM-41 (Al-MCM-41) mesoporous materials were synthesized by non-hydrothermal method in alkali-free ions medium at room temperature and short reaction times. Under these synthesis conditions, it was also investigated the influence of Al incorporation in the crystal structure of MCM-41. The solids were characterized by ICP-OES, AAS, N2 adsorption at 77 K, XRD, TEM, NH3-TPD, 27Al and 29Si-MAS-NMR, FT-IR and TGA. The resulting mesoporous materials showed a well-defined hexagonally ordered pore geometry maintaining a uniform and unimodal pore size distribution with high specific surface areas (1000-1400 m2g-1). The Al+3 ions were introduced successfully in the structure of the purely siliceous MCM-41 expanding the unit cell parameter and forming four-coordinated Al species, and in a less extent, forming six-coordinated Al species. In addition, the surface acidity of the MCM-41 increased with Al loading. Contrary, the presence of Al in the MCM-41 mesoporous structure resulted in a decrease of the crystallinity and specific surface area possibly due to the presence of Al species in highly distorted tetrahedral structures and Al extra-framework or amorphous alumina occluded in the pores. The MCM-41 type mesoporous materials obtained in this work show similar characteristics of those synthesized by conventional hydrothermal methods.