Showing papers on "MCM-41 published in 2016"

Comparative performance of M-MCM-41 (M: Cu, Co, Ni, Pd, Zn and Sn) catalysts for steam reforming of methanol

Abstract: One-pot hydrothermal procedure was used to synthesize high surface area M-MCM-41 (M: Cu, Co, Ni, Pd, Zn, and Sn) nanocatalysts. The M-MCM-41 catalysts containing 10 wt% of different metals were examined to evaluate the performance of individual metals in steam reforming of methanol (SRM) in terms of activity, selectivity and long term stability under similar operating conditions. The fresh and spent catalysts were characterized using BET, XRD, TGA-DSC, TEM, TPR, ICP-OES, EDX, Raman, and FTIR analytical techniques. Cu-MCM-41 showed the best performance in terms of activity and selectivity among the different catalysts investigated in this study. The overall SRM reactivity trend for different metals based on methanol conversion followed the order: Cu-MCM-41 > Pd-MCM-41 > Sn-MCM-41 > Ni-MCM-41 ≈ Zn-MCM-41 > Co-MCM-41. The catalytic performance of Cu-MCM-41 at 250 °C using 1:3 methanol-water mole ratios showed 100% H2 selectivity, ∼6% CO, and no methane formation. The time-on-stream studies conducted continuously for 40 h at 300 °C revealed that Cu-MCM-41 was the most stable catalysts and displayed consistent steady state conversion (up to74%). The SRM activity of Pd, Sn and Zn was comparatively better; however, they deactivated steadily with time. Although coking was a major factor in deactivation of the catalysts, degradation of the mesoporous structure and thermal sintering appeared to play an influential role in deactivation, particularly in the case of Sn-MCM-41.

Immobilization of a vanadium complex onto functionalized nanoporous MCM‐41 and its application as a catalyst for the solvent‐free chemoselective oxidation of sulfide to sulfoxide

Abstract: A complex moiety containing VO(IV) was anchored covalently into organic-modified Si-MCM-41 to prepare a new catalyst. The prepared materials were characterized using various techniques. Several types of aromatic and aliphatic sulfides were successfully oxidized to the corresponding sulfoxides in good to excellent yields using H2O2 in the presence of a catalytic amount of the catalyst under solvent-free conditions. The results showed that the OH groups of the various compounds such as 2,2-(phenylthio)ethanol and 2-(methylthio)ethanol remained intact under similar conditions. Meanwhile the catalyst was stable in the reaction system, and could be reused at least four times without significant loss of its activity and chemoselectivity. Copyright © 2016 John Wiley & Sons, Ltd.

Mn-Schiff base modified MCM-41, SBA-15 and CMK-3 NMs as single-site heterogeneous catalysts: Alkene epoxidation with H2O2 incorporation

Abstract: The development of new functional catalytic materials prepared via appropriate chemical modification of mesoporous silica SBA-15, MCM-41 or carbon nanomaterials CMK-3, are presented. Their synthesis has been carried out via two synthetic approaches: (a) a two steps procedure which includes grafting of the Schiff base ligand 1,3-bis[3-aza-3-(1-methyl-3-oxobut-1-enyl)-prop-3-en-1-yl]-2-(4-hydroxy-phenyl)-1,3-imidazolidine (L) onto the suppors and subsequent metalation of the so-formed hybrid material, and (b) an one step procedure which allows covalent grafting of the entire [Mn II -Schiff base] catalyst onto the carbonaceous support. The resulting single-site heterogeneous catalysts were characterized and evaluated for alkene epoxidation with H 2 O 2 in the presence of CH 3 COONH 4 as additive. They are efficient and selective towards formation of epoxides. The highest TONs have been achieved by L@MCM-41-Mn II and Mn II -L@CMK-3 . Moreover, Mn II -L@CMK-3 is operative for a second use and kinetically very fast, demonstrating remarkably high TOFs 65–634 h −1 that is correlated to its practically zero porosity. Based on the present data, the textural features of the obtained catalysts are discussed in correlation with their catalytic performance.

MCM-41 immobilized 12-silicotungstic acid mesoporous materials: Structural and catalytic properties for esterification of levulinic acid and oleic acid

Abstract: 12-silicotungstic acid (H4SiW12O40, HSiW) was successfully immobilized in the mesoporous molecular sieves MCM-41, which was prepared by an open synthesis method without hydrothermal process, to form a novel catalyst. The HSiW/MCM-41 catalysts preserve the hexagonal mesoporous features of MCM-41 and the typical Keggin structure of bulk HSiW. Up to a loading of 45 wt.%, the HSiW species are found to be homogeneously dispersed on the surfaces or inside the pores of MCM-41 frameworks. The influences of various catalytic reaction parameters such as the reaction temperature, reaction time and types of alcohol on the conversion of levulinic acid were investigated to characterize the catalytic performances of the mesoporous catalysts. Remarkably, the results show that the conversion value could reach 100% under the optimized conditions. The esterification reaction of oleic acid with methanol was also utilized to evaluate the catalytic performances of the mesoporous materials. The HSiW/MCM-41 catalysts exhibit excellent reusability in the esterification reactions and the yield of methyl oleate is as high as 81.2%.

Catalytic performance of supported g-C3N4 on MCM-41 in organic dye degradation with peroxymonosulfate

Abstract: A graphitic carbon nitride-containing MCM-41 catalyst (g-C3N4/MCM-41) was prepared through an in situ thermal approach and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, N2 adsorption–desorption and X-ray photoelectron spectroscopy. It was found that Acid Orange 7 (AO7) and other five organic dyes can be completely degraded by the g-C3N4/MCM-41 catalyst within 30 min in the presence of peroxymonosulfate (PMS), while g-C3N4 + PMS and MCM-41 + PMS show nearly no activity. A non-radical pathway accompanied by radical generation in PMS activation and AO7 oxidation is proposed. The oxidized carbon species N–C–O on g-C3N4 with strong electron density plays a key role in the reaction, while the large surface area of the catalyst can also efficiently enhance the accessibility of catalytic active sites. Though the reusability of the g-C3N4/MCM-41 catalyst is not very good as that of metal oxide catalysts, its activity can be recovered by KOH treatment. The study can broaden the application of g-C3N4 in the area of wastewater treatment.

Biodiesel production from Hevea brasiliensis oil using SO3H-MCM-41 catalyst

Abstract: The use of Hevea brasiliensis oil (para rubber seed oil) as a biodiesel feedstock was achieved under high pressure in an autoclave reactor using a methyl propyl sulfonic acid-functionalised MCM-41 catalyst (SO3H-MCM-41). Four experimental parameters, namely catalyst loading, reaction time, reaction temperature, and the molar composition of 3-mercaptopropyl(methyl)dimethoxysiloxane, were investigated using the Box–Behnken design. The optimisation model showed good statistical reliability, with a linear correlation coefficient close to 1. Under the optimum reaction conditions (5.06 wt% catalyst loading, 120 min, 153 °C, and 0.266 of MPMDS molar composition), the highest predicted and experimental fatty acid methyl ester yields were 96.6% and 95.5%, respectively. The catalyst was benchmarked against a commercial homogeneous catalyst (H2SO4) and proven to be more effective. Moreover, the catalyst could be reused up to four cycles under the optimum reaction conditions without significant loss of product yield.

Efficient Hydrogenolysis of Guaiacol over Highly Dispersed Ni/MCM-41 Catalyst Combined with HZSM-5

Abstract: A series of MCM-41 supported Ni catalysts with high metal dispersion was successfully synthesized by simple co-impregnation using proper ethylene glycol (EG). The acquired Ni-based catalysts performed the outstanding hydrogenolysis activity of guaiacol. The effects of the synthesis parameters including drying temperature, calcination temperature, and metal loading on the physical properties of NiO nanoparticles were investigated through the use of X-ray diffraction (XRD). The drying temperature was found to significantly influence the particle sizes of NiO supported on MCM-41, but the calcination temperature and metal loading had less influence. Interestingly, the small particle size (≤3.3 nm) and the high dispersion of NiO particles were also obtained for co-impregnation on the mixed support (MCM-41:HZSM-5 = 1:1), similar to that on the single MCM-41 support, leading to excellent hydrogenation activity at low temperature. The guaiacol conversion could reach 97.9% at 150 °C, and the catalytic activity was comparative with that of noble metal catalysts. The hydrodeoxygenation (HDO) performance was also promoted by the introduction of acidic HZSM-5 zeolite and an 84.1% yield of cyclohexane at 240 °C was achieved. These findings demonstrate potential applications for the future in promoting and improving industrial catalyst performance.

Cu-Mo2C/MCM-41: An Efficient Catalyst for the Selective Synthesis of Methanol from CO2

Abstract: Supported molybdenum carbide (yMo2C/M41) and Cu-promoted molybdenum carbide, using a mechanical mixing and co-impregnation method (xCuyMo2C/M41-M and xCuyMo2C/M41-I) on a mesoporous molecular sieve MCM-41, were prepared by temperature-programmed carburization method in a CO/H2 atmosphere at 1073 K, and their catalytic performances were tested for CO2 hydrogenation to form methanol. Both catalysts, which were promoted by Cu, exhibited higher catalytic activity. In comparison to 20Cu20Mo2C/M41-M, the 20Cu20Mo2C/M41-I catalyst exhibited a stronger synergistic effect between Cu and Mo2C on the catalyst surface, which resulted in a higher selectivity for methanol in the CO2 hydrogenation reaction. Under the optimal reaction conditions, the highest selectivity (63%) for methanol was obtained at a CO2 conversion of 8.8% over the 20Cu20Mo2C/M41-I catalyst.

Enhanced photodegradation of dyes and mixed dyes by heterogeneous mesoporous Co–Fe/Al2O3–MCM-41 nanocomposites: nanoparticles formation, semiconductor behavior and mesoporosity

Abstract: In situ loading of mono and bimetallic nanoparticles in the framework of mesoporous Al2O3–MCM-41 and its effect on the photo-Fenton degradation of dyes and mixed dyes has been reported in the present study. The nanocomposites are synthesized by in situ sol–gel cum hydrothermal method where oleic acid has been used as capping agent for mono and bimetallic nanoparticles. Materials were characterized by high and low angle XRD, N2 sorption, and HRTEM to evaluate mesoporosity, morphology and textural properties. The photoluminescence (PL) study and band gap energy measurement reveals suppression of e− and h+ recombination and semiconductor behaviour of bimetallic/Al2O3–MCM-41 in visible region. Both the processes of photo-Fenton and photocatalysis takes place over mesoporous Co–Fe/Al2O3–MCM-41 nanocomposite, which is found to be an efficient material with 100% efficiency for the degradation of dyes and mixed dyes (100 mg L−1) at pH 10 in just 60 minutes. Framework mesoporosity, nanoparticle morphology of the nanocomposite, semiconductor behavior, lowering of the electron–hole recombination and the formation of a large number of ˙OH radicals are the crucial factors for swift degradation of dyes and mixed dyes by mesoporous Co–Fe/Al2O3–MCM-41 nanocomposite.

Catalytic Performance of Al-MCM-41 Catalyst for the Allylation of Aromatic Aldehydes with Allyltrimethylsilane: Comparison with TiCl4 as Lewis acid

Abstract: Mesoporous Al-MCM-41 molecular sieve with Si/Al ratio equal to 12.5 was synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. This solid was characterized using several techniques e.g. powder X-ray diffraction (XRD), N2 adsorption-desorption, FT-IR, TG/DTG and pyridine adsorption-desorption followed by IR spectroscopy. The catalytic performance of Al-MCM-41 catalyst as Lewis acid was used without treatment and was compared with TiCl4 in the allylation of aromatic aldehydes with allyltrimethylsilane. The results showed that in presence of Al-MCM-41, homoallyl silyl ether is obtained regardless of the nature of aromatic aldehydes at a temperature of 35 °C. When TiCl4 was used, the reactions require temperature of −85 °C and all the products obtained were due to the diallylation. To explain this different allylation in the presence of the Al-MCM-41 or TiCl4, two plausible reaction mechanisms are proposed. The Al-MCM-41 was used in four consecutive experiments without important loss of activity, confirming it stability. Finally, a new method for preparing single allylation in the short timeframe and mild conditions are presented.

Tungstophosphoric acid-based mesoporous materials anchored to MCM-41: characterization and catalytic performance in esterification of levulinic acid with ethanol

Abstract: MCM-41 was synthesized with a non-hydrothermal procedure and then used to assemble a series of supported H3PW12O40 (HPW) mesoporous catalysts. The optimization of the reaction conditions for LA esterification with ethanol, such as the reaction temperature, reaction time, the reactant molar ratio and the catalyst dosages was performed to maximize the conversion of LA over 25 wt% HPW/MCM-41 catalysts. The catalytic performance of the resultant HPW/MCM-41 catalysts was investigated. The results show that these catalysts retain the hexagonal phase of MCM-41 and the Keggin characteristic of HPW. Although their textural parameters decrease with increasing HPW loading, these catalysts still exhibit much higher specific surface area and pore volume (SBET ≥ 446 m2 g−1, VP ≥ 0.345 cm3 g−1) than that of HPW (SBET = 5 m2 g−1, VP = 0.010 cm3 g−1). LA conversion increases with increasing HPW loading and the value may reach up to 83.7 % over 45 wt% HPW/MCM-41 under the present conditions. The resultant ethyl levulinate is promising in reducing the consumption of petroleum-derived fossil fuels.

Synthesis of Micro-Mesoporous Composites MCM-41/13X and Their Application on CO2 Adsorption: Experiment and Modeling

Abstract: Two micromesoporous composites of MCM-41/13X are synthesized through a two-step crystallization process and a one-step crystallization process, respectively. The results of X-ray diffraction, nitrogen adsorption–desorption isotherms, Fourier transform infrared spectroscopy, and transmission electron microscopy results show that the as-prepared samples possessed both micropores and mesopores. The materials take advantage of not only the large adsorption capacity and thermal stability of the microporous material, but also the rapid diffusion and mass transfer of mesoporous materials, which lead to improve CO2 adsorption capacities compared to the pure microporous or mesoporous materials.

A facile preparation of palladium Schiff base complex supported into MCM-41 mesoporous and its catalytic application in Suzuki and Heck reactions

Abstract: A simple and efficient method for phosphine-free C–C coupling reactions such as Heck and Suzuki reactions in the presence of pyrrole Schiff base complex of palladium immobilized on mesoporous mesoporous of MCM-41 (Pd-Py-MCM-41) has been reported. The Suzuki reaction was carried out in PEG-400 using phenylboronic acid (PhB(OH)2). Pd-Py-MCM-41 has been found as a promising catalyst for Heck reaction of butyl acrylate with aryl halides (including Cl, Br and I). The catalyst was characterized by FT-IR, TEM, XRD, SEM, BET and ICP-OES techniques. The protocol proves to be efficient and environmentally benign in terms of high yield, easy of recovery and reusability of catalyst.