Using cetyl-trimethyl-ammonium bromide （CTMAB） as template and tetraethylortho-silicate （TEOS） as silica source, the MCM-41 mesoporous materials incorporated in framework by Y, Nd and Sm were synthesized by hydrot...Using cetyl-trimethyl-ammonium bromide （CTMAB） as template and tetraethylortho-silicate （TEOS） as silica source, the MCM-41 mesoporous materials incorporated in framework by Y, Nd and Sm were synthesized by hydrothermal synthesis method. The structure, morphology of materials and the state of Y, Nd, Sm in materials were investigated by means of XRD, nitrogen adsorption-desorption, SEM, IR spectrometry, TG-DTA. The XRD results indicate that the samples possess the mesoporous MCM-41 structures with ordered hexagonal arrangements. Y, Nd and Sm ions can get into the framework of mesoporous materials. Nitrogen adsorption desorption isotherms show that the samples have typical mesopores characteristics. SEM micrographs reveal that incorporated sampies show a spherical morphology and the diameters are averagely 0. l0 to 0.15 μm. In IR spectrum of samples, there are the feature adsorption peaks about Si-O-Ln（Ln=Y, Sm, Nd）at 960-985 cm^-1, which affirm that Y, Nd, Sm ions locate in the framework of several mesoporous materials. Results from TG-DTA analysis suggest that two different template sorption sites exist in the framework of YMCM-41, SmMCM-41, NdMCM-41, which powerfully proves that the presence of Y, Nd and Sm in Si framework of the materials.展开更多
Using cetyl-trimethyl-ammonium bromide （CTMAB） as template agent and tetraethylorthosilicate （TEOS） as silica Source, the MCM-41 mesoporous materials were synthesized with Y, Nd and Sm incorporated in the framewor...Using cetyl-trimethyl-ammonium bromide （CTMAB） as template agent and tetraethylorthosilicate （TEOS） as silica Source, the MCM-41 mesoporous materials were synthesized with Y, Nd and Sm incorporated in the framework under hydrothermal conditions. The structure and the micro-morphology of the materials and the state of Y, Nd and Sm were investigated through the analyses of XRD, nitrogen adsorption-desorption isotherm, SEM, IR and TG-DTA. The XRD resuits indicate that the synthetic samples are of typical structure of mesoporous MCM-41 with ordered hexagonal arrangements, and Y, Nd and Sm can be incorporated into the framework of these mesoporous materials. Nitrogen adsorption-desorption isotherms show that the samples possess the typical mesopores character. SEM micrographs reveal that the incorporated samples show a well-defined spherical morphology with the diameter ranging 0.10 - 0.15μm. The occurrence of two different template sorption sites in the framework as revealed by TG-DTA analysis further suggests the presence of Y, Nd and Sm in siliceous framework.展开更多
Novel in-situ reduction approach was applied for the synthesis of palladium nanoparticles in the pores of mesoporous silica materials with grafted siliconhydride groups. Matrices possessing different structural proper...Novel in-situ reduction approach was applied for the synthesis of palladium nanoparticles in the pores of mesoporous silica materials with grafted siliconhydride groups. Matrices possessing different structural properties (MCM-41, SBA-15 and Silochrom) were used. Samples were studied by nitrogen adsorption-desorption method, low-angle X-ray diffraction, transmission electron microscopy (TEM) and FT-IR/PAS spectroscopy. The temperature-programmed oxidation (TPO) and reduction (TPR) methods were applied to examine reducibility of palladium species. Palladium containing catalysts were tested in methane oxidation reaction. It was demonstrated that relatively large pores in SBA-15 type silica facilitated formation of well-dispersed palladium nanoparticles confined in the pores channels. In the case of MCM-41 support, metallic palladium nanoparticles were formed on the external surface. The obtained materials showed high catalytic activity. Lower activity of the samples containing small crystallites located in the pore volume at high temperatures was related to worse accessibility of active sites to the reation mixture.展开更多
In the last 20 years, it has become apparent that waste produced from plastics was becoming an environmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste...In the last 20 years, it has become apparent that waste produced from plastics was becoming an environmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste plastics, it is generally accepted that material recovery is not a long-term solution to the present problem, and that energy or chemical recovery is a more attractive alternative, including cracking into the monomer constituents, combustion to produce energy, and thermal or catalytic conversion to produce useful intermediate chemicals. This paper is a contribution in the area of the last option for energy recovery. There have been a number of publications reporting the use of molecular sieves and amorphous silica-alumina catalysts for the cracking of polymers into a range of hydrocarbons. The research work reported here demonstrates the ability of mesoporous catalysts in cracking polyethyl- ene into gasoline range products. It was found that for mesoporous MCM-41 catalysts, its cracking activity increases with its crystallinity, displaying higher activity with smaller pore diameters. The hydrocarbon product distribution strongly indicates a carbenium ion cracking mechanism. The product distribution was also compared with those obtained from thermal cracking tests.展开更多
Cu-incorporated ordered hexagonal mesoporous silicates （Cu-MCM-41） with spheres-within-a-sphere hollow structure have been synthesized using thermoreversible polymer hydrogel methylcellulose （MC） and cationic surf...Cu-incorporated ordered hexagonal mesoporous silicates （Cu-MCM-41） with spheres-within-a-sphere hollow structure have been synthesized using thermoreversible polymer hydrogel methylcellulose （MC） and cationic surfactant as co-templates, which have been characterized by scanning electron micrograph （SEM）, X-ray diffraction （XRD）, transmission electron micrograph （TEM）, and N2 adsorption-desorption isotherms. The obtained results indicate that the morphology of Cu-incorporated MCM-41 materials is ＂spheres-within-a-sphere＂ hollow structure, which is very similar to that of the alveolus. In benzene hydroxylation with H2O2, the hollow spheres show much higher catalytic activity than particles of Cu-MCM-41.展开更多
A transparent thin film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G (R6G) dye on glass substrates. The film of silica-surfactant-R6G ma...A transparent thin film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G (R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure, was composed of nanocrystallites about 35 nm in diameter and 1-10 mm in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover, optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.展开更多
文摘Using cetyl-trimethyl-ammonium bromide （CTMAB） as template and tetraethylortho-silicate （TEOS） as silica source, the MCM-41 mesoporous materials incorporated in framework by Y, Nd and Sm were synthesized by hydrothermal synthesis method. The structure, morphology of materials and the state of Y, Nd, Sm in materials were investigated by means of XRD, nitrogen adsorption-desorption, SEM, IR spectrometry, TG-DTA. The XRD results indicate that the samples possess the mesoporous MCM-41 structures with ordered hexagonal arrangements. Y, Nd and Sm ions can get into the framework of mesoporous materials. Nitrogen adsorption desorption isotherms show that the samples have typical mesopores characteristics. SEM micrographs reveal that incorporated sampies show a spherical morphology and the diameters are averagely 0. l0 to 0.15 μm. In IR spectrum of samples, there are the feature adsorption peaks about Si-O-Ln（Ln=Y, Sm, Nd）at 960-985 cm^-1, which affirm that Y, Nd, Sm ions locate in the framework of several mesoporous materials. Results from TG-DTA analysis suggest that two different template sorption sites exist in the framework of YMCM-41, SmMCM-41, NdMCM-41, which powerfully proves that the presence of Y, Nd and Sm in Si framework of the materials.
文摘Using cetyl-trimethyl-ammonium bromide （CTMAB） as template agent and tetraethylorthosilicate （TEOS） as silica Source, the MCM-41 mesoporous materials were synthesized with Y, Nd and Sm incorporated in the framework under hydrothermal conditions. The structure and the micro-morphology of the materials and the state of Y, Nd and Sm were investigated through the analyses of XRD, nitrogen adsorption-desorption isotherm, SEM, IR and TG-DTA. The XRD resuits indicate that the synthetic samples are of typical structure of mesoporous MCM-41 with ordered hexagonal arrangements, and Y, Nd and Sm can be incorporated into the framework of these mesoporous materials. Nitrogen adsorption-desorption isotherms show that the samples possess the typical mesopores character. SEM micrographs reveal that the incorporated samples show a well-defined spherical morphology with the diameter ranging 0.10 - 0.15μm. The occurrence of two different template sorption sites in the framework as revealed by TG-DTA analysis further suggests the presence of Y, Nd and Sm in siliceous framework.
基金This work was supported by European Community,seventh Framework Programm(FP/2007-2013)Marie Curie International Research Staff Exchange Scheme(grant no.230790)project MEC 06 MAT2006 01997.
文摘Novel in-situ reduction approach was applied for the synthesis of palladium nanoparticles in the pores of mesoporous silica materials with grafted siliconhydride groups. Matrices possessing different structural properties (MCM-41, SBA-15 and Silochrom) were used. Samples were studied by nitrogen adsorption-desorption method, low-angle X-ray diffraction, transmission electron microscopy (TEM) and FT-IR/PAS spectroscopy. The temperature-programmed oxidation (TPO) and reduction (TPR) methods were applied to examine reducibility of palladium species. Palladium containing catalysts were tested in methane oxidation reaction. It was demonstrated that relatively large pores in SBA-15 type silica facilitated formation of well-dispersed palladium nanoparticles confined in the pores channels. In the case of MCM-41 support, metallic palladium nanoparticles were formed on the external surface. The obtained materials showed high catalytic activity. Lower activity of the samples containing small crystallites located in the pore volume at high temperatures was related to worse accessibility of active sites to the reation mixture.
文摘In the last 20 years, it has become apparent that waste produced from plastics was becoming an environmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste plastics, it is generally accepted that material recovery is not a long-term solution to the present problem, and that energy or chemical recovery is a more attractive alternative, including cracking into the monomer constituents, combustion to produce energy, and thermal or catalytic conversion to produce useful intermediate chemicals. This paper is a contribution in the area of the last option for energy recovery. There have been a number of publications reporting the use of molecular sieves and amorphous silica-alumina catalysts for the cracking of polymers into a range of hydrocarbons. The research work reported here demonstrates the ability of mesoporous catalysts in cracking polyethyl- ene into gasoline range products. It was found that for mesoporous MCM-41 catalysts, its cracking activity increases with its crystallinity, displaying higher activity with smaller pore diameters. The hydrocarbon product distribution strongly indicates a carbenium ion cracking mechanism. The product distribution was also compared with those obtained from thermal cracking tests.
基金Project supported by the National Natural Science Foundation of China, the Major State Basic Research Development Program of China （Nos. 2004CB217804 and 2003CB615802）, and Ministry of Education, China.
文摘Cu-incorporated ordered hexagonal mesoporous silicates （Cu-MCM-41） with spheres-within-a-sphere hollow structure have been synthesized using thermoreversible polymer hydrogel methylcellulose （MC） and cationic surfactant as co-templates, which have been characterized by scanning electron micrograph （SEM）, X-ray diffraction （XRD）, transmission electron micrograph （TEM）, and N2 adsorption-desorption isotherms. The obtained results indicate that the morphology of Cu-incorporated MCM-41 materials is ＂spheres-within-a-sphere＂ hollow structure, which is very similar to that of the alveolus. In benzene hydroxylation with H2O2, the hollow spheres show much higher catalytic activity than particles of Cu-MCM-41.
基金This work was financially supported by a grant from the Science Foundation of Guangzhou (2000-Z-076-01) and Laboratory of Rare Earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Science.
文摘A transparent thin film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G (R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure, was composed of nanocrystallites about 35 nm in diameter and 1-10 mm in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover, optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.
