CFD-based optimization and design of multi-channel inorganic membrane tubes

As a major configuration of membrane elements,multi-channel porous inorganic membrane tubes were studied by means of theoretical analysis and simulation.Configuration optimization of a cylindrical 37-channel porous inorganic membrane tube was studied by increasing membrane filtration area and increasing permeation efficiency of inner channels.An optimal ratio of the channel diameter to the inter-channel distance was proposed so as to increase the total membrane filtration area of the membrane tube.The three-dimensional computational fluid dynamics(CFD) simulation was conducted to study the cross-flow permeation flow of pure water in the 37-channel ceramic membrane tube.A model combining Navier–Stokes equation with Darcy's law and the porous jump boundary conditions was applied.The relationship between permeation efficiency and channel locations,and the method for increasing the permeation efficiency of inner channels were proposed.Some novel multichannel membrane configurations with more permeate side channels were put forward and evaluated.

Preparation and Conducting Behavior of Amphibious Organic/Inorganic Hybrid Proton Exchange Membranes Based on Benzyltetrazole

A series of novel amphibious organic/inorganic hybrid proton exchange membranes with H3PO4 doped which could be used under both wet and dry conditions was prepared through a sol-gel process based on acrylated triethoxysilane（A-TES） and benzyltetrazole-modified triethoxysilane（BT-TES）.The dual-curing approach including UV-curing and thermal curing was used to obtain the crosslinked membranes.Polyethylene glycol（400） diacrylate（PEGDA） was used as an oligomer to form the polymeric matrix.The molecular structures of precursors were characterized by 1 H,13 C and 29 Si NMR spectra.The thermogravimetric analysis（TGA） results show that the membranes exhibit acceptable thermal stability for their application at above 200 oC.The differential scanning calorimeter（DSC） determination indicates that the crosslinked membranes with the mass ratios of below 1.6 of BT-TES to A-TES and the same mass of H3PO4 doped as that of A-TES possess the-T g s,and the lowest T g（-28.9 ℃） exists for the membrane with double mass of H3PO4 doped as well.The high proton conductivity in a range of 9.4―17.3 mS/cm with the corresponding water uptake of 19.1%―32.8% of the membranes was detected at 90 oC under wet conditions.Meanwhile,the proton conductivity in a dry environment for the membrane with a mass ratio of 2.4 of BT-TES to A-TES and double H3PO4 loading increases from 4.89×10-2 mS/cm at 30 ℃ to 25.7 mS/cm at 140 ℃.The excellent proton transport ability under both hydrous and anhydrous conditions demonstrates a potential application in the polymer electrolyte membrane fuel cells.

Conventional processes and membrane technology for carbon dioxide removal from natural gas:A review

Membrane technology is becoming more important for CO,_ 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 CO2 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 CO2 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 CO2 from natural gas, challenges of current commercial polymeric membranes and inorganic membranes for CO2 removal and membrane surface modification for improved selectivity.

Preparation of Palladium-Silica Conjugated Membrane for Selective Hydrogen Permeation

Palladium membranes were prepared on an α-alumina support bymetal-organic compound chemical vapor deposition (MOCVD) method frompalladium (II) acetate precursor. Permeation properties of hydrogenand helium gas were studied as a function of the number of times ofdeposition of palladium on the peeling off phenomenon of palladium,which is common in electroless plated membrane, was observed. Silicawas introduced into the pores to prevent the palladium grain frompeeling off. The palladium-silica conjugated membrane does not showthe peeling off phenomenon and can withstand the high temperature upto 800 deg. C which is the upper limit of our apparatus.

Synthesis of Gas Transport through Nano Composite Ceramic Membrane for Esterification and Volatile Organic Compound Separations

The transport behaviour of carrier gases with inorganic catalytic ceramic membrane used for ethyl lactate production and VOC （volatile organic compound） recovery in the gauge pressure range of 0.10-1.00 bar and temperature range of 333 K was investigated. The gases include Ar （argon）, N2 （nitrogen） and CO2 （carbon dioxide）. The gas kinetic diameter with respect to permenace was found to occur in the order of At 〉 CO2 〉 N2, which was not in agreement with molecular sieving mechanism of transport after the first dip-coating of the support. However, gas flow rate was found to increase with gauge pressure in the order of Ar 〉 CO2 〉 N2, indicating Knudsen mechanism of transport. The porous ceramic support showed a higher flux indicating Knudsen transport. The surface image of the dip-coated porous ceramic membrane was characterised using SEM （scanning electron microscopy） to determine the surface morphology of the porous support at 333 K.

Catalytic Film and Selective Oxidation of Iso-butylene

A kind of heteropoly compound film supported on Ce0.5Zr0.5O2 oxide was prepared on a porous titanium tube. The catalytic activity of the film for the selective oxidation of iso-butylene was tested and compared with the fixed-bed reactor. Results show that the catalytic film increases the yield of the target product-methacrylic acid, and avoids the temperature fluctuation caused by the reaction heat.

Preparation and Characterization of Sepiolite Microfibers with High Aspect Ratio

It is difficult to access exfoliated sepiolite(Sep)fibers with high aspect ratio from Sep ore.The traditional method used to purify Sep ore also reduces its aspect ratio.In this study,impurities in the Sep ore were removed by acid activation followed by a cetyltrimethylammonium chloride(C16)treatment to organically modify the purified Sep by cation exchange.Then,the organically-modified Sep(O-Sep)was stripped and processed by an ultrasonic cell crusher to obtain Sep microfibers at a specific frequency for a given period.These Sep samples had relatively high aspect ratio,compared with the Sep fibers gotten by traditional method.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)demonstrate the micro-morphology of exfoliated Sep samples in an intuitive way.Moreover,pure inorganic membrane prepared only with the exfoliated Sep fibers exhibited excellent flexibility,further demonstrating the excellent properties of Sep fibers with high aspect ratio.

Recent developments of anti-plasticized membranes for aggressive CO_(2)separation

Membrane separation technology provides an effective alternative to mitigate the massive carbon emission with high carbon capture productivity and efficiency.In the context of operating membranes under high CO_(2)pressures allows increased separation productivity and reduced gas compression cost,which,however,often leads to CO_(2)induced plasticization,a key hurdle for current gas separation membranes.In this review,we reviewed the latest development of membranes with anti-plasticization resistance,potentially suited for operation under high CO_(2)feed streams.Specifically,the separation performance of polymeric membranes,inorganic membranes,and mixed matrix membranes under high CO_(2)feed pressures are discussed.Approaches to enhance CO_(2)induced plasticization of those membranes are also summarized.We conclude the recent progress of membranes for high CO_(2)pressures with perspectives and an outlook for future development.

Hierarchical CuO-ZnO/SiO_(2) Fibrous Membranes for Efficient Removal of Congo Red and 4‑Nitrophenol from Water

Hierarchical CuO-ZnO/SiO_(2)(CZS)nanofibrous membranes are designed and fabricated to remove Congo red and 4-nitro-phenol two common small molecular pollutants in water.The electrospun SiO_(2) fibrous membrane is serves as the substrate for hydrothermal depositing CuO-ZnO nanosheets.The CZS nanofibrous membrane shows good adsorption characteristics for Congo red due to the hierarchical morphology and the adsorption kinetics where isotherm follows the pseudo-second-order model and Langmuir model,respectively.The maximum adsorption capacity for Congo red is 141.8 mg/g.Moreover,the membrane exhibits excellent catalytic reduction activity for 4-nitrophenol under mild conditions and over 96%of the pollut-ants are degraded within 90 s.The CZS nanofibrous membrane has promising prospects in applications in water treatment and environmental protection because of the good flexibility,easy fabrication,excellent adsorption,and catalytic activity.

Gas separation using porous cement membrane

Gas separation is a key issue in various industrial fields. Hydrogen has the potential for application in clean fuel technologies. Therefore, the separation and purification of hydrogen is an important research subject. CO2 capture and storage have important roles in ＂green chemistry＂. As an effective clean technology, gas separation using inorganic membranes has attracted much attention in the last several decades. Membrane processes have many applications in the field of gas separation. Cement is one type of inorganic material, with the advantages of a lower cost and a longer lifespan. An experimental setup has been created and improved to measure twenty different cement membranes. The purpose of this work was to investigate the influence of gas molecule properties on the material transport and to explore the influence of operating conditions and membrane composition on separation efficiency. The influences of the above parameters are determined, the best conditions and membrane type are found, it is shown that cementitious material has the ability to separate gas mixtures, and the gas transport mechanism is studied.

Factors affecting the formation of zeolite seed layers and the effects of seed layers on the growth of zeolite silicalite-1 membranes

The present study investigates the formation of silicalite-1 seed layers on a porous carbon support of 0.5µm pore size andα-Al_(2)O_(3) supports with different pore sizes(0.1µm and 4µm)via the slip-casting technique.The effects of support property,seed size and solvent on the formation of seed layers were investigated in detail.The growth of sili-calite-1 membranes on different seeded supports by hydro-thermal synthesis was also evaluated.The scanning electron microscopy(SEM)and X-ray diffraction(XRD)character-izations indicate that a continuous seed layer can be obtained on the smooth support of 0.1µm pore size by using any seed of 100 nm,600 nm or 2.2µm in size,whereas,on the coarse supports with either 0.5µm or 4µm pore size,a continuous seed layer cannot be formed using the above seed sizes and the same seeding time.At a longer contact time,a seed layer can also be formed using 100 nm seed on the supports with larger pore size.However,the layer is not uniform and smooth.For a hydrophobic porous carbon support,seeding ethanol suspension,which has weak polarity,favors the formation of a continuous seed layer.The seed layers and membranes grown from the smaller seed are more uniform and continu-ous and possess smoother surfaces than those from the larger seed.The seed layer and respective grown membrane formed from nanosized seed(100 nm)are the most uniform and compact.With this method of seeded secondary synthesis of zeolite membranes,the quality of a membrane mainly depends on the quality of the seed layer.

Molecular and nanostructure designed superhydrophilic material with unprecedented antioil-fouling property for diverse oil/water separation

The design and development of new advanced superwetting porous membranes with antioil-fouling performance are still rare and highly desirable because of their potential widespread applications.A metallic phosphate nanoflower-covered mesh membrane with superhydrophilic and unprecedented antioil-fouling properties is prepared by an exceptionally simple and effective in-situ solution corrosion method.As demonstrated,the outstanding antioil-fouling property of the resulting mesh membrane is connected with the special phosphate group and the three-dimensional(3 D) nanoflower structure.Owing to the antioil-fouling property,upon to water,the oil-fouled mesh membrane can keep the surface free of various kinds of oils,including viscous crude oil to light n-hexane.Thanks to its unprecedented self-cleaning property,the superhydrophilic mesh membrane can effectively separate different oil/water mixtures without prior wetted by water,exhibiting great potential for practical spilled oil remediation.