MCM-41 Framework Research Articles

Glycerol carbonate synthesis via transesterification of enriched glycerol and dimethyl carbonate using a Li-incorporated MCM-41 framework.

Waste crude glycerol was successfully enriched and utilized as an inexpensive source for producing value-added chemicals, such as glycerol carbonate (GC) - a valuable compound with extensive industrial applications. The Li/MCM-41 heterogeneous catalyst was synthesized and used for the transesterification of enriched glycerol and dimethyl carbonate (DMC) to produce GC. The catalyst's physicochemical properties were characterized using thermogravimetric, Hammett indicator, inductively coupled plasma-optical emission spectroscopy, nitrogen adsorption-desorption, X-ray diffractometry, scanning electron microscopy, and Fourier-transform infrared spectroscopy analyses. Reaction conditions were optimized using response surface methodology and analysis of variance, yielding an accurate quadratic model to predict the GC yield under different transesterification variables. The results revealed that 5%Li/MCM-41 served as the optimal catalyst, achieving the highest TOF of 4.72 h-1. The DMC: enriched glycerol molar ratio had the greatest impact on the GC yield, with an R2 = 0.9743 and adjusted R2 = 0.9502. The optimal GC yield (58.77%) with a final purity of 78% was attained at a 5.15 wt% catalyst loading relative to the initial amount of enriched glycerol, DMC: enriched glycerol molar ratio of 4.24 : 1, and a reaction temperature of 86 °C for 165 min. The 5%Li/MCM-41 heterogeneous catalyst could be reused for four cycles with a decreased GC yield from 58.77% to 45.72%. Thus, the Li/MCM-41 catalyst demonstrated a remarkable efficiency and potential as a heterogeneous catalyst for synthesizing GC. This method not only contributes to environmental sustainability by making use of a byproduct from biodiesel production but also aligns with the principles of a circular economy.

Fabrication of highly efficient nanofiltration membranes decorated with praseodymium based triamino-functionalized MCM-41 for desalination and micropollutants removal

The nanofiltration membranes with a stable decoration of inorganic fillers such as zeolites are desperately required for enhancing the desalination performance of the membranes and hence three nanofiltration membranes were fabricated by decorating the membranes with praseodymium-based triamino-functionalized MCM-41 (Pr-(NH)2NH2-MCM-41). The membranes were applied for the removal of emerging pharmaceutically active micropollutants from water. The Pr-(NH)2NH2-MCM-41 was synthesized by using an in-situ approach where praseodymium oxide was chemically decorated in the framework of MCM-41 followed by simultaneous amine functionalization using N1-(3-Trimethoxysilylpropyl)diethylenetriamine (TMSPTA). A thorough characterization of the synthesized Pr-(NH)2NH2-MCM-41 was carried out by using HR-TEM, SEM, WCA, XRD, FTIR, BET, elemental and mapping analysis. Three different concentrations of synthesized Pr-(NH)2NH2-MCM-41 were decorated in the membrane active layer through interfacial polymerization in the presence of an aqueous tetra-amine solution and using terephthaloyl chloride as an organic crosslinker. Subsequently, the fabricated membranes were used for desalinating saline feed containing divalent (CaCl2, MgCl2, Na2SO4, MgSO4) and monovalent (NaCl) ions. The rejection of salts by PA/0.05-Pr-MCM@PSU/PET membrane was found to be the highest among all the fabricated membranes which were found to be 98 %, 96 %, 95 %, 87 %, and 82 % for CaCl2, MgCl2, MgSO4, Na2SO4 and NaCl, respectively. The permeate flux was found to be dependent on the applied feed pressure which was found to be 56 L m-2 h-1 (LMH) at 25 bar for PA/0.050-Pr-MCM@PSU/PET membrane. The rejection performance of the membranes was also evaluated by using different well-known pharmaceuticals (Caffeine, Sulfamethoxazole, Amitriptyline, and Loperamide) as micropollutants in the feed. All the pharmaceutical drugs were found to be highly rejected > 96 % by PA/0.5-Pr-MCM-41@PSU/PET membrane followed by PA/0.025-Pr-MCM-41@PSU/PET membrane. Therefore, the current approach of synthesizing functionalized zeolites is quite effective and efficient for the stable decoration of inorganic fillers in the membrane active layer and should be extended to other zeolites such as zeolites with antimicrobial potential.

Enhancement of the thermal stability for MCM-48 with incorporation of different metals

The incorporation of different metal types (Fe, Al, Mn, Zn, and Cu) on MCM-48 synthesized by the direct sol-gel method was investigated. In this work, tetraethyl orthosilicate (TEOS) was used as a silica source, whereas cetyltrimethylammonium bromide (CTAB) was employed as a structure directing agent. The molar ratio of Silicon/metal was kept at 45. The obtained samples were characterized by XRD, N2 physisorption, SEM, and UV-VIS techniques. It revealed that Fe, Mn, and Zn incorporated into the framework of MCM-48 resulted in increased thickness of the pore wall, leading to better thermal stability than pure MCM-48. In contrast, the agglomeration of metal oxides, and the nature of aluminum perhaps lead to the decreased thickness of the pore wall in MCM-48 and consequently lower thermal stability. Additionally, the findings indicate that when the thickness of the pore wall is approximately 1.3 nm onward, the thermal stability of metal-incorporated MCM-48 will be improved.

Tritium separation from radioactive wastewater by hydrogen isotope-selective exchange of hydrogen-bonded fluorine

The separation of tritium (3H) from radioactive wastewater is a persistent challenging problem in the nuclear industry from an environmental perspective. This study provides new insight into the tritium separation by investigating hydrogen isotope-selective exchange reaction on hydrogen-bonded fluorine (F····H····O) site. In this study, fluorinated mesoporous silica, F-MCM-41_NCs were prepared as a novel tritium sorbent that showed a significantly enhanced tritium isotope separation factor (α) compared to the pristine MCM-41 (α = 1.2). The optimal α of 3.3 is achieved using 0.5F-MCM-41_NC prepared with 0.5 g of NH4F per gram of MCM-41. This optimal α is attributed to an excellent compromise between the amount and the stability of (NH4)2SiF6 on the pore channel with the integrity of the MCM-41 framework. Experimental, theoretical, and analytical characterization results consistently support chemical affinity quantum sieving effect at F····H····O hydrogen-bonding sites via the hydrogen isotope-selective exchange reaction as the dominant tritiumseparation mechanism.

Deactivation origins and stability-enhancing strategies of Sn/SiO2 catalysts for ethane dehydrogenation

A low-cost and environment-friendly Sn/SiO2 catalyst, highly active and selective for ethane dehydrogenation, is an effective alternative for high-cost Pt and toxic CrOx-based catalysts. While the catalyst deactivates fast due to the loss and aggregation of Sn species. In order to solve the problem, complexation impregnation method and in-situ synthesis approach have been tried to enhance the stability of Sn-based catalyst. As for the former one, a relatively stable performance of 5Sn/SiO2 catalyst can be achieved due to depressed Sn loss and coke deposition, while there is still room for improvement. When the latter strategy is applied, 5Sn-MCM-41 catalyst demonstrates the optimal dehydrogenation performance, with 44.0% of ethane conversion and 98.8% of ethylene selectivity, and no obvious decreasing trend is observed in the progress of 18 h reaction due to the well dispersion and anchoring of Sn species on the framework of MCM-41.

Enhancing catalytic ozonation activity of MCM-41 via one-step incorporating fluorine and iron: The interfacial reaction induced by hydrophobic sites and Lewis acid sites

Fe-MCM-41 had been widely used as ozonation catalyst, however, the existence of large amount of hydrophilic silanol hindered its interfacial reaction with O3 and pollutants. To solve this problem, F–Fe-MCM-41 was synthesized by co-doping F and Fe into the framework of MCM-41 to replace silanol with Si–F groups through a one-step hydrothermal method. F introduced hydrophobic sites which contributed to more ibuprofen (IBP) chemisorption on the surface of F–Fe-MCM-41. Moreover, doping F also enhanced the acidity, which accelerated O3 decomposition into •OH. F–Fe-MCM-41/O3 exhibited notably activity with 96.6% IBP removal efficiency within 120 min, while only 78.5% and 80.9% in O3 alone and Fe-MCM-41/O3, respectively. Surface Lewis acid sites and metal hydroxyl groups were considered as important factors for O3 activation and •OH generation. F–Fe-MCM-41 exhibited excellent catalytic performance under acidic and alkaline conditions. Comparative experiments revealed that F doping improved the interfacial reaction, especially the interfacial electron transfer, which resulted in the high catalytic activity of F–Fe-MCM-41. F–Fe-MCM-41 possessed good stability and reusability, with only 5.7% decline for IBP removal in five successive cycles. Furthermore, the possible degradation path of IBP was proposed according to DFT calculation and GC-MS analysis.

The mechanism of Ce-MCM-41 catalyzed peroxone reaction into •OH and •O2− radicals for enhanced NO oxidation

A series of Cerium-doped MCM-41 were prepared by hydrothermal method and used in peroxone process (O3/H2O2) for low-temperature NO oxidation. The experimental results showed that the NO oxidation efficiency could reach 93% for 3Ce-MCM-41 (molar ratio Ce/Si = 3%) under the molar ratio of H2O2/NO = 2.8 and O3/NO = 0.5. The addition of SO2 was conducive to the improvement of NO oxidation efficiency, which was assigned to SO2 improving the desorption of the intermediate product NO2 and promoting the progress of NO oxidation reaction. The hydroxyl and superoxide radical scavenger tert‑butanol and p-Quinone confirmed that O3/H2O2/3Ce-MCM-41 followed the •OH and •O2− radicals co-oxidation mechanism. Afterwards, the characterized results exhibited that Ce was incorporated into the framework of MCM-41 and presented in tetrahedral coordination, which enhanced Lewis acid sites over Ce-MCM-41 samples. Besides, the presence of Ce3+/Ce4+ promoted electron transfer. Meanwhile, the high surface area of 3Ce-MCM-41 (819 m2•g−1) was benefited to reactants transfer. Thus, O3/H2O2/3Ce-MCM-41 process achieved a high NO oxidation efficiency.

Facile preparation of ordered mesoporous Nb,Ta-MCM-41 by hydrothermal direct synthesis using columbite ore as metal source

– The current study aims to prepare an Nb,Ta-containing ordered mesoporous catalyst MCM-41, using hydrated mixed oxide of niobium and tantalum, extracted from the columbite ore processing, as an alternative source of these metals. Direct hydrothermal synthesis was employed to incorporate the metals into the molecular sieve structure using the TEOS + sodium silicate mixture as silica source and varying Nb and Ta content in terms of Si/Me (Me = Nb and Ta) molar ratios of 60, 30 and 15 to evaluate the influence of the charge of these metals on both structural formation and properties of the material. The material was characterized by XRD, SEM, TEM, N2 adsorption, UV–Vis-DRS, and FTIR investigations to the incorporation of the metal into the MCM-41 framework. The techniques employed proved the successful replacement of Si atoms by metallic cations of Nb and Ta. The catalyst showed good structural order preservation and surface area (>600 m2 g-1) with mesoporous behavior with capillary condensation even at a higher metal load. This research signifies a successful procedure of a novel bimetallic mesoporous material with promising properties for several applications using an abundant ore as a metal source.

Magnetic Fe3O4 nanoparticles and ZrO2-doped mesoporous MCM-41 as a monolithic multifunctional catalyst for γ-valerolactone production directly from furfural

A magnetically-recoverable multifunctional catalyst (Fe3O4/ZrO2@MCM-41) was tailored by the impregnation of ZrO2 supported on mesoporous MCM-41 coated Fe3O4 nanoparticles, which successfully served as a monolithic catalyst for the cascade conversion of furfural (FAL) giving high yield to γ-valerolactone (GVL), a versatile platform molecule. The ordered hexagonal framework of the parent MCM-41 well reserved after the embedding of Fe3O4 and ZrO2. The incorporation of Fe3O4 could not only impart the catalyst with a strong magnetism, but also tune its acidity to promote GVL production. An impressive yield of 85% was accomplished straight from FAL processing with iso-propanol as a hydrogen donor and solvent. The kinetic study demonstrated higher activation energy for levulinate-to-GVL step (86.9 kJ/mol) than FAL transfer hydrogenation (35.0 kJ/mol) and subsequent alcoholysis process (51.0 kJ/mol). The catalyst could be fully recovered by an external magnetic field and showed good reusability. The sustainability of this conversion represents greatly improved by the process intensification based on one-pot reaction, magnetically-recoverable multifunctional catalyst, and mild operating conditions without using gaseous hydrogen.

Metal-Loaded Mesoporous MCM-41 for the Catalytic Wet Peroxide Oxidation (CWPO) of Acetaminophen

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the formation of oxides of the different metals on the surfaces of all materials. Low-angle X-ray diffraction (XRD) analyses showed that calcination resulted in the incorporation of metallic Zn, Fe and Cr in the framework of MCM-41, while in the case of Cu, thin layers of CuO were formed on the surface of MCM-41. The solids obtained were tested in the catalytic wet peroxide oxidation (CWPO) of acetaminophen at different temperatures (25–55 °C). The activity followed the order: Cr/MCM-41 ≥ Fe/MCM-41 > Cu/MCM-41 > Zn/MCM-41. The increase of the reaction temperature improved the performance and activity of Cr/MCM-41 and Fe/MCM-41 catalysts, which achieved complete conversion of acetaminophen in short reaction times (15 min in the case of Cr/MCM-41). Fe/MCM-41 and Cr/MCM-41 were submitted to long-term experiments, being the Fe/MCM-41 catalyst the most stable with a very low metal leaching. The leaching results were better than those previously reported in the literature, confirming the high stability of Fe/MCM-41 catalysts synthesized in this study.

Performance of Al-MCM-41 nanospheres as catalysts for dimethyl ether production

The need to develop specific-morphology nanomaterials to produce dimethyl ether (DME), a promissory alternative fuel, by the catalytic methanol dehydration has triggered extensive research to synthesize novel materials. In this work mesoporous Al-MCM-41 nanospheres with variable size (35−90 nm) were synthesized by the sol-gel method. The size of the Al-MCM-41 nanospheres was controlled by adjustable NaOH/TEOS ratio (0.2−0.5). The Al-MCM-41 nanospheres were characterized by TPD, TEM, XRD, EDX, XPS and N2-physisorption. According to the characterization results the Al ions were successfully incorporated in the MCM-41 framework and the Al-MCM-41 nanospheres showed hexagonal and mesoporous structure. Additionally, it was observed that the higher the NaOH/TEOS ratio the smaller size of the nanosphere and, smaller Al-MCM-41 nanospheres presented more amount of medium acidic sites on its surface. The catalytic activity results showed that all samples tested reached 100% of selectivity towards DME. The smallest Al-MCM-41 nanospheres achieved 78% of DME yield at 300 °C and good catalytic activity performance below to 300 °C. The stability of the fresh and regenerated Al-MCM-41 nanospheres was evaluated for 48 h time-on-stream. High values of DME yield (> 60%) were maintained during 48 h time-on-stream showing the possibility for recycling the material.

MCM-41 modified heterogeneous catalysts from rice husk for selective oxidation of styrene into benzaldehyde

This study examined the preparation of MCM-41, Ni-MCM-41 and Co-MCM-41 from silica extracted from rice husk ash (RHA) via sol–gel technique. The materials were characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Diffuse reflectance UV–Vis (DR/UV–Vis),Energy Dispersive X-ray Spectrometry (EDX), N 2 adsorption–desorption and NH 3 TPD. XRD and TEM analyses showed reduction in the long range order upon the introduction of heteroatoms into MCM-41 framework. Successful substitution of Si 4 + with metal cations was verified by the shifting in the siloxane (Si-O-Si) bond. Presence of nickel phyllosilicates was evidenced from the FT-IR and DR/UV–Vis investigations. Mesoporous behavior with capillary condensation was unchanged even after the incorporation of Ni and Co species into the MCM-41 matrix. MCM-41 and modified MCM-41 catalysts were evaluated in the liquid-phase oxidation of styrene for 4 h under the influence of reaction parameters such as reaction temperature, catalyst loading, types of solvent and molar ratio of styrene : H 2 O 2 . Under the optimum condition of 343 K, 0.20 g catalyst, 1:4 molar ratios and DMF as the reaction medium, the activity was found to increase following the trend: Ni-MCM-41 (79.9%) >Co-MCM-41(56.6%) > MCM-41 (40.7%). Benzaldehyde was the sole product over Ni-MCM-41 and Co-MCM-41 while MCM-41 gave benzaldehyde (96.0%) and styrene oxide (4.0%). Surface characteristics and TPD acidity strength was found to govern the catalysis. Negligible leaching (0.448 ppm) and exceptional activity during successive reruns demonstrates that Ni-MCM-41 was beyond doubt, heterogeneous in nature. This research signifies a successful conversion of waste biomass into value added products. • Cobalt and nickel supported MCM-41 catalysts were synthesized from rice husk. • The catalyst was active in the oxidation of styrene at mild condition. • Benzaldehyde was the sole product over the modified MCM-41 catalysts. • The catalysis of Ni-MCM-41 was heterogeneous in nature with minor leaching. • Successful conversion of waste biomass into benign product.

Micelles of Mesoporous Silica with Inserted Iron Complexes as a Platform for Constructing Efficient Electrocatalysts for Oxygen Reduction.

Iron, N-codoped carbon materials (Fe-N-C) are promising electrocatalysts toward oxygen reduction reactions due to their high atom utilization efficiency and intrinsic activity. Nanostructuring of the Fe-N-C materials, such as introducing porosity into the carbon structure, would be conducive to further increasing the exposure of active sites as well as improving the mass transfer. Herein, we explore the potential of iron complex-functionalized micelles of mesoporous SiO2 as a platform for constructing porous Fe-N-C materials. The classical three-dimensional MCM-48 was selected as a proof-of-concept example, which was utilized as the hard template, and cetyltrimethylammonium bromide micelles inside it played the role of the main carbon source. Fe-Nx sites were derived from Fe-1,10-phenanthroline complexes in the micelles introduced by in situ incorporation of 1,10-phenanthroline and post Fe2+ insertion in an aqueous solution. After thermal annealing in a nitrogen atmosphere and subsequent removal of the MCM-48 framework, a carbon material that possesses porous structural features with uniformly dispersed Fe-Nx sites (MPC@PhFe) was obtained, which shows superior ORR activity in a 0.1 M KOH solution and great potential for Zn-air battery applications as well. This work demonstrates the feasibility as well as the effectiveness of turning micelles of mesoporous SiO2 into porous carbon structures and might offer a universal strategy for manufacturing carbon materials for future application in energy storage and conversion.

Role of Br\xf8nsted and Lewis acidic sites in sulfonated Zr-MCM-41 for the catalytic reaction of cellulose into 5-hydroxymethyl furfural

A series of sulfonated Zr-MCM-41 samples were synthesized by the in-situ method followed by sulfonation using sulfuric acid for the catalytic study of cellulose to 5-hydroxymethyl furfural in batch condition. All synthesized catalysts were characterized by XRD, N2 adsorption–desorption isotherm, FT-IR, TEM, EDX, and NH3 temperature-programmed desorption analysis. The XRD and N2 adsorption–desorption isotherm results have confirmed that incorporated Zr4+ was substituted within the framework of silica MCM-41 with hexagonal pores. Similarly, the FT-IR and EDX results have proved that Zr-MCM-41 was sulfonated. The Brønsted acidic and Lewis acidic sites were identified by NH3-TPD analysis. Among the sulfonated Zr-MCM-41 catalysts, S-15Zr-MCM-41 has shown 70% cellulose conversion with 16.4% selectivity of 5-hydroxymethyl furfural at 170 °C for 2 h which was higher than other catalysts. It was attributed to the high ratio of Brønsted acidic to Lewis acidic sites.Graphic abstract

In-situ incorporation of ruthenium/copper nanoparticles in mesoporous silica derived from rice husk ash for catalytic acetylation of glycerol

Abstract Ruthenium and copper nanoparticles were incorporated into MCM-41-like mesoporous silica via a fast sol-gel method at 80 °C using rice husk ash (RHA) as the silica source. The physico-chemical characterization of the synthesized materials was carried out using various analytical techniques. The X-ray diffraction results indicated that the mesoporous silica synthesized in this study had the standard MCM-41 structure. The Fourier transform infrared spectroscopy results showed that ruthenium and copper ions were successfully incorporated into the hexagonal framework of the mesoporous materials. The transmission electron microscopy results revealed that the RHA-MCM-41, MCM-41-10Ru, and MCM-41-10Ru10Cu samples consisted of ordered mesoporous straight channels. MCM-41-10Cu consisted of copper nanospheres. MCM-41-10Ru and MCM-41-10Ru10Cu showed ruthenium nanoparticle agglomerates distributed on their external MCM-41 framework surfaces. In the case of MCM-41-10Cu and MCM-41-10Ru10Cu, copper ions were homogeneously dispersed on the internal surface of the agglomerated porous silica matrix. The as-prepared Ru- and Cu-doped MCM-41 catalyst was used for the acetylation of glycerol. The catalyst showed a high conversion of 98% and high shape selectivity towards the formation of diacetin and triacetin unlike conventional silica-based catalysts, which show selectivity towards the formation of monoacetin.

Benzene-1,3,5-tricarboxylic acid-functionalized MCM-41 as a novel and recoverable hybrid catalyst for expeditious and efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones via one-pot three-component reaction

Benzene-1,3,5-tricarboxylic acid-functionalized MCM-41 (MCM-41-Pr-BTA), as a novel hybrid organosilica, was prepared and properly characterized by the Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, thermal gravimetric analysis and energy-dispersive X-ray spectroscopy to evaluate the functional groups, crystallinity, surface area, morphology, particle size distribution and loading of functional groups. Interestingly, the 1,3-propylene linker used in this study incorporates appropriate catalytic activity into the MCM-41 framework compared to the more known trialkoxypropyl silanes. This new organosilica can be used as a hybrid nanocatalyst for the expeditious and efficient synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives, as an important pharmaceutical scaffold, in aqueous media via a three-component one-pot condensation of isatoic anhydride and aromatic aldehydes with primary amines or ammonium salts. This method has several advantages such as low catalyst loading, high to excellent yields, short reaction times, working under green conditions and simple workup.

CO2 methanation over Ni/Mg@MCM-41 prepared by in-situ synthesis method

A series of xMg@MCM-41(x=0, 0.05, 0.1) functional mesoporous materials were synthesized by a novel in-situ one pot method and then were used as supports for Ni based catalysts. The results of XRD and TEM show that when the amount of Mg/Si (molar ratio) is 0.05, Mg@MCM-4 with a regular and ordered mesoporous structure is synthesized where Mg is introduced into the framework of MCM-41. Introducing Mg into the framework of the support can significantly enhance the basic properties of the catalyst, thus promoting the adsorption and activation of CO2. The catalysts prepared in the experiments all have good thermal stability and catalytic activity. Among them, Ni/0.05Mg@MCM-41 showed the best low temperature reaction activity in the CO2 methanation reaction.

Weak base favoring the synthesis of highly ordered V-MCM-41 with well-dispersed vanadium and the catalytic performances on selective oxidation of benzyl alcohol

The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms. The alkalinity plays the indispensable role in synthetic process of V-MCM-41 catalyst. The excessive alkalinity of synthetic system will make the MCM-41 difficult to crystallize, even to dissolve. It is easy to accumulate for heteroatomic species in the system of low alkalinity. Herein, the highly ordered V-MCM-41 with high vanadic content in framework is synthesized in the condition of excessive NH3·H2O in this paper. A series of characterization results prove the good dispersion of vanadium species, and most of vanadium gets into the framework of MCM-41 with the states of tetravalence and pentavalence. Furthermore, the modified MCM-41 by other transition metals is successful synthesized by the method of V-MCM-41 in this paper. The V-MCM-41 shows well catalytic activity for the selective oxidation of benzyl alcohol, which up to 74.83% for the conversion of benzyl alcohol and 96.20% for selectivity of benzaldehyde when initial V/Si = 0.10. The paper provides the possibility for industrial application of V-MCM-41 in the oxidation of benzyl alcohol for benzaldehyde. Besides, the work provides a significant idea for the synthesis of modified MCM-41 by well-dispersed transition metals.

CH4 Cracking over the Cu–Ni/Al-MCM-41 Catalyst for the Simultaneous Production of H2 and Highly Ordered Graphitic Carbon Nanofibers

The Cu-Ni bimetallic catalysts dispersed on various silica supports were examined for catalytic cracking of CH4 to produce pure H2 with near zero COx emissions and fine quality carbon nano fibers. The 27Al MAS NMR spectra of Al containing MCM-41 samples revealed the existence of framework and extra framework decorated Al species. Insertion of Al species into the framework of MCM-41, significantly improved the accessible active surface Ni sites, which was confirmed from the simultaneous H2 and N2O pulse titration techniques. NH3 TPD measurements demonstrated a high ratio of moderate and strong acid sites upon Al- insertion into the silica matrix. The framework tetrahedral -Al in MCM-41 stabilized the surface Cu-Ni alloy sites and protected from the sintering and fragmentation of Ni consequently enhanced the H2 yields of 270 Nm3/(molNi)-1 were obtained with Si/Al ratio = 150 with catalyst. The better performance of the Cu-Ni/Al-MCM-41 (Si/Al = 150) was rationalized using the physicochemical characteristics ...

Iron oxide impregnated mesoporous MCM-41: synthesis, characterization and adsorption studies

Mesoporous MCM-41 and MCM-41 impregnated with structural iron (Fe–MCM-41) were prepared by a facile surfactant based wet chemical method using tetraethyl orthosilicate, cetyl trimethyl ammonium bromide in the presence of ammonium hydroxide and FeSO4·7H2O as impregnated reagent. The prepared mesoporous materials were characterized by small and wide angle X-ray diffraction (XRD), XPS, FESEM, HRTEM, FTIR and N2 gas adsorption/desorption isotherm techniques. The results indicate the formation of high surface area (1266 m2/g) porous structure with particle size in the range of 200–400 nm for MCM-41. In case of Fe–MCM-41 the surface area decreases (880 m2/g) substantially with formation of iron oxide nanoparticles in the frame work of MCM-41. The obtained mesoporous materials were used as adsorbents for the removal of methylene blue from aqueous media. The percentage removal of the dye was found to be 99.9% for Fe–MCM-41 and 94.5% for MCM-41, respectively, by using 20 mL of dye solution with initial concentration of 100 mg/L and 0.05 g of each adsorbent. The maximum adsorption capacity of Fe–MCM-41 was found to be 194 mg/g and for MCM-41, it was 149.5 mg/g. This result suggests that the prepared Fe–MCM-41 is an effective adsorbent for decontamination of Methylene blue from aqueous media.