查看更多>>摘要：Ce based Metal Organic Framework(MOF)UiO-66(Ce)and a MOF-composite Ce02@Ui0-66(Ce)were prepared by conventional heating and hydrothermal method respectively.Both the MOFs were characterized using X-ray Diffraction(XRD)technique,Fourier Transform Infra Red(FT-IR)spectroscopy,Field Emission-Secondary Electron Microscopy(FE-SEM),Small Angle X-ray Scattering(SAXS),Thermogravimetric Analysis(TGA),Differential Thermal Analysis(DTA)and Transmission Electron Microscopy(TEM).N2 adsorption-desorption isotherms of UiO-66(Ce)showed large specific surface area of-981 m~2/g and a reasonably large pore volume compared to the composite sample.Their uranium adsorption capacity in aqueous solutions was investigated in the pH range 2-6.Uranium adsorption experiments indicated reasonably higher uranium adsorption capacity of 239 mg/g for CeO2@Ui0-66(Ce)compared to UiO-66(Ce)(190 mg/g).Kinetic studies revealed rapid uranium adsorption in pure MOF compared to the composite material which was attributed to the blocking of pores by CeO2 nanoparticles in the composite material.These frameworks showed good thermal stability as revealed by the thermogravimetric studies.The synthesized MOFs exhibit moderate recyclability using dilute acid and can be utilized in successive cycles.The selectivity studies showed that these MOFs are highly selective to U(VI)compared to Fe(III),Co(II),Ni(II)and Sr(II).This study could pave a way for more advanced material synthesis involving MOFs which could prove very beneficial for the wastewater remediation thus creating a safer environment to live in.
Brunela Pereira da SilvaViswanathan S.SajiIdalina Vieira Aoki
9页
查看更多>>摘要：Incorporating nanoreservoirs loaded with corrosion inhibitors is the most attractive approach for developing extrinsic self-healing anti-corrosion coatings.This work reports a rapid and eco-friendly one-step synthesis of dodecylamine-encapsulated mesoporous silica nanocontainers.The nanocontainers were characterized by X-ray diffraction,electron microscopy and thermogravimetric analysis.The as-synthesized nanocontainers were amorphous with short-range ordered mesoporous channels.Thermogravimetric study confirmed the inhibitor loading to be ~13.6%.The nanocontainers(1 wt%)were further dispersed in 0.1 mol/L NaCl solution,and the release behaviour was systematically studied as a function of pH(acidic,basic and neutral)by electrochemical impedance spectroscopy at different durations.The release was more pronounced at acidic pH ranges.The inhibitor-loaded nanocontainers provided significantly higher impedance values in acidic environment revealing sustained inhibitor release and enhanced corrosion protection for the carbon steel electrode.The study also reports detailed thermogravimetric results on the effect of different washing procedures in determining the inhibitor percentage loading.
查看更多>>摘要：A series of Zr-Al-MWW zeolites with different Zr state and layer-stacking structure are successfully synthesized via direct grafting zirconocene dichloride onto the external silanols of three kinds of MWW zeolites,i.e.MCM-22 with multilayered structure,ITQ-2(through layer delaminated route)and OL-MWW(by direct hydrothermal synthesis)with oligolayered structure.The structure,porosity and state of grafted Zr species are distinctly different among the three Zr-Al-MWW zeolites.Zr-OL-MWW possesses the highest content of single Zr atoms with an ideal micro-meso-macro pore system,while Zr-MCM-22 and Zr-ITQ-2 contain two kinds of Zr species(ZrO2 clusters and single Zr atoms)coexisting in various proportions.The high dispersion of single Zr atoms on OL-MWW can be assigned to the large amount of external silanols of OL-MWW.The as-prepared three bi-functional Zr-Al-MWW zeolites are used for the cascade Meerwein-Ponndorf-Verley(MPV)reduction and etherification(ETH)reaction.Among them,Zr-OL-MWW shows dramatically higher conversion of cinna-maldehyde and yield of 1-cinnamyl 2-propyl ether than Zr-MCM-22 and Zr-ITQ-2,owing to the higher catalytic activity of Lewis acid centers from single Zr atoms,as well as more integrated framework Al sites as Br0nsted acid centers with good accessibility.This study offers a simple and efficient strategy to construct Lewis-Br0nsted acidic zeolites with exposed heteroatom sites and integrated framework structure,which will provide especial potential in the catalytic conversion of macromolecules.
查看更多>>摘要：The framework confined Pt/TixAlOy catalysts were prepared by a one-step evaporation-induced self-assembly(EISA)technique,and their activities for the catalytic oxidation of propane were investigated.The Pt/TixAlOy catalysts exhibited high specific surface area due to the ordered mesoporous structure.With the increase of TiO2 contents,the specific surface area and acidic sites of Pt/TixAlOy catalysts increased.The specific surface area and acidic sites could improve the exposure of the active sites and electron transfer of Pt and TiO2,which was beneficial to catalytic oxidation of propane.However,too high acidic sites of catalysts could lead to coke deposition and clogging of the pores,and the addition of TiO2 had the optimal value.The Pt/Ti_(0.1)AlOy catalyst exhibited superior catalytic activity,which could be attributed to the higher specific surface area,higher the percentage of Pt~(2+)and lattice oxygen,abundant acid sites,and higher redox properties.In addition,the Pt/Ti_(0.1)AlOy catalyst also exhibited superior sulfur resistance due to the multiple acidic sites of catalysts.
查看更多>>摘要：A series of composite CO2 sorbents were obtained by placing an amino acid ionic liquid(AAIL)l-Ethyl-3-meth-ylimidazolium glycine([Emim][Gly])into mesoporous silica gel using an impregnation method.The parameters of the porous structure for the silica support and composite sorbents were determined from nitrogen adsorption-desorption isotherms measured at 77 K.The morphology of the materials was studied using field-emission scanning electron microscopy.It was shown that at lower[Emim][Gly] loadings(<50 wt%),the sorption is fast and the dynamic CO2 sorption capacity of the material is proportional to the mass content of the AAIL.At higher[Emim][Gly] loadings(>50 wt%),the rate of CO2 sorption by the AAIL decreases due to hindered mass transfer.An increase in CO2 concentration in the gas flow leads to a faster sorption and higher CO2 sorption capacity for the AAIL-containing composite.Meanwhile,the integral enthalpy of sorption decreases with increasing CO2 concentration,which can be explained by the greater contribution of physical adsorption/absorption processes to the total CO2 sorption capacity at higher CO2 concentrations.The most promising composite material(40 wt%[Emim][Gly]/SiO2)was tested in consecutive temperature-swing sorption-desorption cycles.It was demonstrated that lowering the regeneration temperature from 100 to 80 ℃ leads to a decrease in the dynamic sorption capacity of the material,but ensures its stability in the cyclic sorption-desorption process.
查看更多>>摘要：With the modified Ti-ZSM-5 zeolites as supports,the propane dehydrogenation(PDH)performance of the non-noble metal Co-based catalysts can be enhanced,which is benefited from the Ti species-tuned state of active Co species and surface acid property.The developed Co/Ti-ZSM-5 catalysts exhibit>95% C3H6 selectivity and good regeneration stability in the recycling PDH reactions.The characterization results illustrate the structural evolution of Ti from the framework and extra-framework Ti species to the small-size anatase TiO2 species with decreasing the Si/Ti ratio of the Ti-ZSM-5 zeolites,tailoring the dispersion and chemical state of the Co sites at different Co-zeolite or Co-TiO2 interfaces.The Ti-ZSM-5 zeolites with high Si/Ti ratios also show significantly reduced surface acidity especially the Br0nsted acidity in comparison with the Al-ZSM-5 zeolite,thus facilitating the C3H6 desorption for enhancing the selectivity and anti-coke stability.
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