Porous ceramic membranes in high temperature applications

In this paper an evaluation is given of the uses of porous ceramic membranes in high temperature applications, on basis of the results achieved in the past years in our laboratory, in some cases combined with data from the literature. The high temperature (> 300°C) reactor applications of non-modified and of silver modified γ-alumina catalytically active membranes have been studied in relation with the (oxidative) dehydrogenation of methanol, while these of vanadia modified titania catalytically active membranes have been studied in relation with the de-NOx reaction. Catalytically active membrane reactors appeared to be well controllable devices and able to regulate the supply of the reactants to the reaction zone which is the membrane layer itself. Membrane reactors incorporating non-modified γ-alumina passive (separative) membranes have been used in combination with commercial catalysts to enhance the equilibrium conversion of n-butane or of methanol dehydrogenation by separating the hydrogen product. The equilibrium conversions have been shifted by a factor of 2, accompanied with improved selectivities. The selection of the chemical and structural characteristics of the membrane layers as well as of the process parameters of the membrane reactor, is strongly depended on the function of the membrane and determines the performance of the membrane reactor during the process, as discussed in this contribution.