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Catalytic Membranes and Membrane Reactors: An Integrated Approach to Catalytic Process with a High Efficiency and a Low Environmental Impact 总被引:1,自引:0,他引:1
Enrico DRIOLI Enrica FONTANANOVA Marcella BONCHIO Mauro CARRARO Martino GARDAN Gianfranco SCORRANO 《催化学报》2008,29(11)
The design of new heterogeneous photooxygenation systems able to employ visible light,oxygen,mild temperatures,and solvent with a low environmental impact has been investigated. In particular,the heterogenization of decatungstate (W10O4-32),a polyoxometalate with photocatalytic activity in oxidation reactions,has been carried out in polymeric membranes of polyvinylidenefluoride. The polymeric catalytic membranes prepared by phase inversion technique have been successfully applied in the aerobic mineralization of phenol in water,which was used as an example of organic pollutant. In order to evaluate the effect of the polymeric environment on the overall catalyst behavior,we have also heterogenized the decatungstate (opportunely functionalized) in perfluorinated membrane made of Hyflon. The photocatalytic composite membranes are characterized by different and tuneable properties depending on the nature of the polymeric micro-environment,in which the catalyst is confined. Moreover,the selective separation function of the membrane results in enhanced performance in comparison with homogeneous reactions. 相似文献
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Heteropoly compounds (HPC), a kind of polyoxometallates, with their strong acidity and oxidative ability, are good homogeneous and heterogeneous catalysts in both acid-catalyzed and selective oxidation reactions, and have been widely used in petroleum and fine chemical industries. Owing to the diversity in their composition and structure, the catalytic properties of HPC can be altered in a wide range. Among them, the heteropolyanions with Keggin structure have been studied by far the most,especially on their applications in heterogeneous catalysis. However, since they are thermally unstable at high temperatures, their utilization in this field has been restricted. In the last ten years, inorganic membranes have been proved to be beneficial to heterogeneous catalytic processes for their high selectivity and good heat-conductivity. And the sol-gel method, one of the most common approaches to prepare inorganic membranes, is becoming mature. Here a sol-gel method to prepare a porous HPC membrane is reported. The catalytic performance of the membrane was tested through a model reaction, the selective oxidation of t-BuOH. 相似文献
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Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomem-branes. It refers to that glycosyl groups are introduced onto the membrane surface by various strate-gies, which combine the separation function of the membrane with the biological function of the sac-charides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the sur-face-glycosylated membranes. 相似文献
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Isabel Vazquez-Fernandez Mohamed Raghibi Adnane Bouzina Laure Timperman Janick Bigarre Meriem Anouti 《Journal of Energy Chemistry》2021,(2):197-207,I0008
Poly(vinylidene fluoride), PVDF, membranes have attracted considerable attention as polymer electrolytes for fuel cells. This study explores the effect of solvent on the spherulite size and the crystallinity of the polymeric membranes. Based on Hansen solubility parameters theory, the mixture of DMC and DMSO was selected among a dozen of solvents for the preparation of PVDF membranes by thermally induced phase separation. The addition of two protic ionic liquids(PILs), bis(2-ethyl hexyl) ammonium hydrogen phosphate [EHNH_2][H_2PO_4], and imidazolium hexanoate [Im][Hex] to PVDF membranes at concentrations(10% < wP IL< 50%) has been investigated by SEM, FTIR, DSC, TGA, EIS, and DMA. The inclusion of ionic liquids into the polymer matrix influences structural parameters(degree of crystallinity and electroactive phases), thermal stability, proton conductivity and mechanical properties of the membranes. The membranes become transparent regardless type of ionic liquid employed. A small amount of ionic liquids increases the degree of crystallinity and facilitates the production of polar β and γ crystals. The proton conductivity mechanism(Grotthuss) is dependent on the ionic liquid structure(due to its selforganization in water) and the content in the PVDF membrane, as well as the membrane water uptake.Different behavior has been observed for the two ionic liquids, which stresses the challenge on selecting an appropriate cation and anion combination. The obtained composite membranes exhibited excellent mechanical performance and reduced elastic modulus, with respect to the pure polymer matrix. These results indicate that PVDF/IL composite membranes have a high potential for PEMFC applications. 相似文献
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Sheng Sui Xiaolong Zhuo Kaihua Su Xianyong Yao Junliang Zhang Shangfeng Du Kevin Kendall 《天然气化学杂志》2013,(3):477-483
An extensive study has been conducted on the proton exchange membrane fuel cells(PEMFCs) with reducing Pt loading.This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes.In this paper,a novel process of the catalyst layers was introduced and investigated.A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode(GCE) to form a thin carbon layer.Then Pt particles were deposited on the surface by reducing hexachloroplatinic(Ⅳ) acid hexahydrate with methanoic acid.SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method.The Pt nanowires grown are in the size of 3 nm(diameter) x 10 nm(length) by high solution TEM image.The novel catalyst layer was characterized by cyclic voltammetry(CV) and scanning electron microscope(SEM) as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering.The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants(oxygen or hydrogen). 相似文献
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<正>In an effort to develop biomaterials to meet guided tissue regeneration(GTR) standards for periodontal tissue recovery,a homogeneous and transparent chitosan(CS)/hydroxyapatite(HA) membrane with potential applications as GTR barrier in periodontal therapy has been prepared via in situ compositing.The membrane has been designed to have a smoothrough asymmetric structure that meets the demand for GTR.Component and morphology of the membrane are characterized by XRD and SEM.It can be indicated that HA was in situ synthesized uniformly in the CS membrane.Mechanical experiments of the membranes with various HA contents show that their tensile strengths are adequate for periodontal therapy.Biological properties of the membrane have been performed by cell toxicity assays,hemolysis tests and animal experiments.Results indicate that the membrane has good biocompatibility and inductive effect for cell growth.Therefore this membrane can be potentially applied as GTR barrier membrane for periodontal tissue regeneration. 相似文献
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Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry(FTIR), 1H Nuclear magnetic resonance(1H-NMR) and gel permeation chromatography(GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride)(PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential(ζ) of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy(SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental p H range. The copolymer was also in favor of the formation of β crystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br-anion with PF-6. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio(FR) and total fouling ratio(Rt) all suggested that the blend membranes had good anti-fouling properties. 相似文献
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Porous polymer supported palladium catalyst for cross coupling reactions with high activity has been successfully prepared by coordination of Pd 2+ species with Schiff bases functionalized porous polymer. The catalyst has been systemically investi-gated by a series of characterizations such as TEM, N 2 adsorption, NMR, IR, XPS, etc. TEM and N 2 isotherms show that the sample maintains the nanoporous structure after the modification and coordination. XPS results show that chemical state of palladium species in the catalyst is mainly +2. More importantly, the catalyst shows very high activities and excellent recycla-bility in a series of coupling reactions including Suzuki, Sonogashira, and Heck reactions. Hot filtration and poison of catalysts experiments have also been performed and the results indicate that soluble active species (mainly Pd(0) species) in-situ gener-ated from the catalyst under the reaction conditions are the active intermediates, which would redeposit to the supporter after the reactions. 相似文献
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In this paper,the effect of water vapor removal on methanol synthesis capacity from syngas in a fixed-bed membrane reactor is studied considering long-term catalyst deactivation.A dynamic heterogeneous one-dimensional mathematical model that is composed of two sides is developed to predict the performance of this configuration.In this configuration,conventional methanol reactor is supported by an aluminasilica composite membrane layer for water vapor removal from reaction zone.To verify the accuracy of the considered model and assumptions,simulation results of the conventional methanol reactor is compared with the industrial plant data under the same process condition.The membrane reactor improves catalyst life time and enhances CO2 conversion to methanol by overcoming the limitation imposed by thermodynamic equilibrium.This configuration has enhanced the methanol production capacity about 4.06% compared with the industrial methanol reactor during the production time. 相似文献
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Membrane technology is becoming more important for CO 2 separation from natural gas in the new era due to its process simplicity,relative ease of operation and control,compact,and easy to scale up as compared with conventional processes.Conventional processes such as absorption and adsorption for CO 2 separation from natural gas are generally more energy demanding and costly for both operation and maintenance.Polymeric membranes are the current commercial membranes used for CO 2 separation from natural gas.However,polymeric membranes possess drawbacks such as low permeability and selectivity,plasticization at high temperatures,as well as insufficient thermal and chemical stability.The shortcomings of commercial polymeric membranes have motivated researchers to opt for other alternatives,especially inorganic membranes due to their higher thermal stability,good chemical resistance to solvents,high mechanical strength and long lifetime.Surface modifications can be utilized in inorganic membranes to further enhance the selectivity,permeability or catalytic activities of the membrane.This paper is to provide a comprehensive review on gas separation,comparing membrane technology with other conventional methods of recovering CO 2 from natural gas,challenges of current commercial polymeric membranes and inorganic membranes for CO 2 removal and membrane surface modification for improved selectivity. 相似文献
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Through modeling it has been shown that a concentric-tube catalytic membrane reactor can be used to increase the selectivity for the intermediate products of a consecutive reaction scheme. The reactants are fed to the tube-side of the reactor where the catalyst is also located. The wall of the tube is permeable, allowing the intermediate products to pass through to the annular space instead of undergoing further reaction. The annular space is swept by an inert gas flow and contains no catalyst. Both permselective and non-permselective membranes have been considered in both co-current and counter-current flow regimes. In contrast to most catalytic membrane reactor applications where reactions are reversible and thermodynamically limited, in the present study the reactions considered are irreversible and are under kinetic control. 相似文献
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Clean water supply is an essential element for the entire sustainable human society, and the economic and technology development. Membrane filtration for water and wastewater treatments is the premier choice due to its high energy efficiency and effectiveness, where the separation is performed by passing water molecules through purposely tuned pores of membranes selectively without phase change and additional chemicals. Ceramics and polymers are two main candidate materials for membranes, where the majority has been made of polymeric materials, due to the low cost, easy processing, and tunability in pore configurations. In contrast, ceramic membranes have much better performance, extra-long service life, mechanical robustness, and high thermal and chemical stabilities, and they have also been applied in gas, petrochemical, food-beverage, and pharmaceutical industries, where most of polymeric membranes cannot perform properly. However, one of the main drawbacks of ceramic membranes is the high manufacturing cost, which is about three to five times higher than that of common polymeric types. To fill the large gap between the competing ceramic and polymeric membranes, one apparent solution is to develop a ceramic-polymer composite type. Indeed, the properly engineered ceramic-polymer composite membranes are able to integrate the advantages of both ceramic and polymeric materials together, providing improvement in membrane performance for efficient separation, raised life span and additional functionalities. In this overview, we first thoroughly examine three types of ceramic-polymer composite membranes, (i) ceramics in polymer membranes (nanocomposite membranes), (ii) thin film nanocomposite (TFN) membranes, and (iii) ceramic-supported polymer membranes. In the past decade, great progress has been made in improving the compatibility between ceramics and polymers, while the synergy between them has been among the main pursuits, especially in the development of the high performing nanocomposite membranes for water and wastewater treatment at lowered manufacturing cost. By looking into strategies to improve the compatibility among ceramic and polymeric components, we will conclude with briefing on the perspectives and challenges for the future development of the composite membranes. 相似文献
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The theory of reactions between a surface-active substrate and a polymeric catalyst in emulsions has been developed. The conditions under which the rate of reaction in such systems substantially surpasses the rate of reaction in homogeneous systems have been determined and the regimes that make it possible to reduce the total time of the process have been established. 相似文献
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