Ceramic membranes competitiveness

Bottino, A., Capannelli, G, Comite, A., Del Borghi, A., Di Felice, R., 2004. Catalytic ceramic membrane in a three-phase reactor for the competitive hydrogenation-isomerisation of methylenecyclohexane. Separation and Purification Technology 34,239-245. 

Palladium is an expensive metal and this imposes limits on the thickness of material that can be used for hydrogen purification in competition with other industrial methods. Emonts et al. estimated that films less than about 5 p,m in thickness need to be used in a fuel-cell methanol reformer [7], while Criscuoli et al. [8] concluded that 20 p,m is an upper limit for membranes to be economically competitive. These economic estimates overlook the possibility of recycling the palladium or palladium alloy. This becomes a very real possibility in the use of free-standing membranes rather than composite structures with other metals or ceramics. Recycling prospects probably increase the thickness constraint to something between 5 jxm and 8 p.m, a value that is also consistent with factors such as limitations on the volume of space occupied by a multiple membrane assembly. 

Aaron and Tsouris [66] rank membrane separation processes as one of the most promising options. They anticipate advances in ceramic and metallic membrane technology will eventually lead to membrane processes that are more efficient than absorption - the best current option. Favre [67] argues that polymeric membrane technology is competitive today despite its dismissal in most studies. A techno-economic analysis suggests membranes are competitive when carbon dioxide concentration reaches -20% (as found in the effluent from cement and steel factories) and vacuum is used to drive carbon dioxide transport. Although the subject of debate, the potential for membrane technology will continue to attract interest and research effort. 

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