A Morphological Study of Ceramic Hollow Fibre Membranes: A Perspective on Multifunctional Catalytic Membrane Reactors

Abstract

In recent years ceramic membrane technology has advanced considerably and ceramic membranes are now being applied to a number of high temperature applications, in particular in the energy industry as membrane reactors. Due to the thermal stability of ceramic materials, development in this area is extremely promising as these applications cannot be realized using polymeric membrane technology. Although a wide range of ceramic materials have been developed and processing techniques have improved considerably, the high production cost and lack of control over membrane properties when fabrication processes are scaled up are prohibitive in the commercial application of ceramic membrane technology. However, by using a dry-wet spinning process and the combined phase inversion and sintering technique, novel asymmetric hollow fibre morphologies consisting of a porous sponge-like structure and finger-like macrovoids in which catalyst may be deposited can be prepared in a cost effective way. These asymmetric hollow fibres are prepared from raw materials and are suitable for use in catalytic membrane reactors. Fibre morphology is determined by the rheological properties of the ceramic spinning suspension as well as the parameters used during fibre spinning and the effect of sintering during heat treatment. A generic mechanism has been suggested for the formation of asymmetric structures and the parameters at each of these three stages have been varied systematically in order to predict and control hollow fibre structure. Hollow fibres prepared in this way have been characterized in terms of morphology, pore size distribution, porosity and mechanical strength in terms of their applicability to membrane reactor applications. The versatility of this preparation technique is demonstrated by the inclusion of a chapter describing a catalytic membrane reactor for hydrogen production by water-gas-shift as well as a reactor for the dehydrogenation of propane. It should also be noted that this reactor design could be applied to a number of other catalytic gas phase reactions