Ceramic Composite Membrane Research Articles

Preparation of Ceramic Membrane Filters, From Waste Fly Ash, Suitable for Hot Gas Cleaning

The preparation and performance of ceramic membrane filters made from fly ash from coal-fired power stations were investigated. The porous and crack-free ceramic composite membrane was prepared by dip-coating a stainless steel mesh in a slurry of fly ash. Membrane properties investigated included pore structure, permeability and mechanical strength. The ash membrane filter shows great potential for the filtration and microfiltration of high-temperature gas-particulate streams, and reuses waste fly ash composed of multiple oxides with a wide size distribution. The median pore size of the tested membrane was 2.3 μm and the differential pressure gradient was 0.9 kPa 1-1 min-1, which is comparable to fabric filters currently in use in some New South Wales power stations. The high mechanical strength of the membrane was caused by fusion of the glassy material in the fly ash. Since the membrane consists of metal and ceramic composities, it also shows good flexibility.

Preparation and characterization of microporous ceramic hollow fibre membranes

Ceramic hollow fibre membranes have been prepared out of aluminium-oxide and silicon-nitride. The fibres have been produced in a three stage process. A polymer filled with ceramic material has been prepared in a blender, a hollow fibre precursor has been made by extrusion of the melt with a spinneret and the precursor is transformed in a ceramic fibre by means of heat treatment at 1200–1650°C. The outer diameter of the ceramic fibres is 800–2700 μm depending on the diameter of the spinneret used. The hollow fibres are microporous and show gas flues of about 4–15 × 10 −8 m 3/m 2 s Pa. In a final step alumina fibres have been modified by coating them with a γ-alumina top-layer. The composite fibres have gas fluxes of about 4 × 10 −8 m 3/m 2 s Pa and are gas selective. The selectivity is close to the value predicted by the Knudsen diffusion theory. So it is possible to produce a defect free ceramic composite hollow fibre membrane. This membrane can serve as a basis for a high selective membrane.

Thermomechanical Stability of Polymer—Ceramic Composite Membranes

Abstract The mechanical stability of thin-film polymer—ceramic composite membranes has been evaluated in a variety of processing steps with temperatures ranging from 25 to 350°C. Although not measured in this work, references for similar materials indicate that the coefficients of thermal expansion for the two layers of the membrane are considerably different. Upon heating, this difference led to the development of thermally-induced stresses. These stress could be relieved if the membrane were heated in an unrestrained manner; however, they were sufficient to cause membrane failure if not relaxed. Heating to temperatures above the glass transition of the polymer resulted in defect formation in that layer due to flow into the ceramic support. These results indicate that, if properly handled, the membranes are sufficiently stable to be used over a wide range of temperatures. However, serious consideration must be given to these issues in the design of larger-scale devices.

Preparation of composite ceramic membrane from titania powders

A titania-based composite membrane has been developed. The membrane is prepared from titania powder and stainless steel mesh by an aqueous slurry technique. The effects of dispersion technique and heat-treatment temperature on the nature imperfections and titania agglomerates were investigated. The membranes were characterised by determining their pore size distributions, the pressure drop to air flow and the membranes' flexibility.

Effect of mild solvent post-treatments on the gas transport properties of glassy polymer membranes

This study examines the effect of treatment of defective glassy polymer membranes with a variety of vapors and liquids which have varying solvency power for the polymer. The pure-gas oxygen/nitrogen selectivities of defective, asymmetric membranes are shown to be permanently increased, in special cases, by treatment with certain solvents which have adequate solvency power to cause a critical level of swelling in the membrane skin layer. Three distinct types of membranes have been treated; asymmetric polysulfone membranes formed by dry/wet phase inversion, spin-coated poly(phenylene oxide)-ceramic composite membranes and solution-deposited polyimide-ceramic composite membranes. While the detailed fundamental processes controlling the elimination of surface defects are complex, our results suggest that plasticization of the selective skin layer, coupled with surface-tension driven cohesive forces are likely to be the key factors at play.

Ceramic zeolite composite membranes.: Preparation, characterization and gas permeation

Ceramic zeolite composite membranes, comprising a ceramic substrate and a dense pure zeolite thin layer on the surface of the substrate, have been developed by in-situ synthesis. The zeolite thin layer has been shown by X-ray diffraction, SEM and optical microscopy to have a pure zeolite phase, in which individual zeolite crystallites have intergrown in three dimensions into a polycrystal zeolite thin disc. The nitrogen permeability of these composite membranes, after calcination, reaches 1–4 m 3/m 2-hr-bar at room temperature. The ideal selectivities are 2.81 for He over N 2 and 47.7 for N 2 over n-butane, which are far beyond the range of Knudsen diffusion. After improvement of the preparation procedure the membrane even shows a selectivity of 6.2 for n-butane over i-butane. Combined effects of “shape-selectivity” of the zeolite and capillary condensation of the non-zeolite pores are considered to be responsible for the high selectivities.

Preparation of polymer–ceramic composite membranes with thin defect‐free separating layers

AbstractPolymer—ceramic composite membranes with essentially defect‐free separating layers have been prepared by a solution deposition technique. Rigid polymers were used for the selective organic layer. These included high molecular weight samples of 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuran‐dione, isopropylidenedianiline (6FDA‐IPDA), 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuran‐dione, methylenedianiline (6FDA‐MDA), tetramethylhexafluorobisphenol‐A polycarbonate (TMHFPC), and tetramethylhexafluoropolysulfone (TMHFPSF). Attempts to prepare composite membranes from lower molecular weight samples of bisphenol‐A polycarbonate (PC) and tetrabromohexafluorobisphenol‐A polycarbonate (TBHFPC) were unsuccessful. The PC and TBHFPC composites exhibited a decrease in the measured gas flux after polymer deposition; however, the selectivities of the composites were considerably less than that of a dense film of the same materials. A microporous ceramic membrane prepared by Anotec Separations was used as the support layer. This ceramic membrane provided minimal resistance to gas flow. The selective composite membranes were found to have high gas fluxes and gas separating abilities essentially equivalent to that of a dense isotropic film. The estimated, effective skin layer thicknesses for these membranes are on the order of 1500 Å to 1.0 μm. The formation of these composites is believed to occur through a sieving process in which large swollen polymer chains are sieved out of solution by the ceramic support. Polymer solutions that had swollen coil diameters that were smaller than that of the ceramic membrane did not produce selective composite membranes, while those solutions with swollen coil diameter that were larger than that of the ceramic membrane produced defect‐free polymer layers. © 1992 John Wiley & Sons, Inc.

Ceramesh — a company and a membrane

Claimed as a major advance in microfiltration technology, Ceramesh is an inorganic composite ceramic membrane that can be produced in a flat sheet suitable for use in process-scale crossflow filtration systems. The membrane combines a metal mesh and a ceramic to give strength, formability and both chemical and heat resistance The Ceramesh membrane technology has its origins in work carried out at Alcan Separations in Banbury and has been under development since 1988. Some of the original team had also worked on the development of the Anopore membrane, since commercialised by Anotec, and these close personal links have been maintained. Ceramesh Ltd was formed in 1990 by Alcan and a venture capital company with the aim of speeding the development of the membrane and ensuring its early introduction to the commercial filtration market. These objectives have now been achieved and by the middle of 1992 the Ceramesh membrane has been evaluated for a number of specific applications, been incorporated into a range of commercial filtration equipment, and formally launched into the chemical-process industries at the Eurochem exhibition held in Birmingham in June.

Preparation Of Ceramic Molecular Sieve Membranes

ABSTRACTThe preparation of a composite ceramic membrane consisting of large silicalite (MFI-type) crystals and a gas tight lead-boron silicate glaze is reported on. A one single crystal containing membrane model was prepared to establish the zeolite stability after each preparative step.