Water dense membrane reactors

Silver membranes are permeable to oxygen. Metal membranes have been extensively studied in the countries of the former Soviet Union (Gryaznov and co-workers are world pioneers in the field of dense-membrane reactors), the United States, and Japan, but, except in the former Soviet countries, they have not been widely used in industry (although fine chemistry processes were reported). This is due to their low permeability, as compared to microporous metal or ceramic membranes, and their easy clogging. Bend Research, Inc. reported the use of Pd-composite membranes for the water-gas shift reaction. Those membranes are resistant to H2S poisoning. The properties and performance characteristics of metal membranes are presented in Chapter 16 of this book. 

Dense membrane reactors are discussed, emphasizing the most frequently investigated configurations and applications. Factors influencing economics are analyzed and, as a case study, results on the water-gas shift reaction in Pd-based membrane reactors are presented. 

Dense Membrane Reactors for the Water-Cas Shift Reaction 251 Tab. 9.2 M ain factors influencing the economics of membrane reactors. 

Dense Membrane Reactors for the Water-Cas Shift Reaction... 

Saracco and Specchia [84] noted that inorganic membranes have great potential in gas separation, catalytic reactors, gasification of coal, water decomposition, and solid electrolyte fuel cells [81-89]. Inorganic membranes are usually made from alumina, sUica, carbon, and zeolites [85]. We will only assess porous membranes since fouling is virtually absent in dense membranes [81]. 

The single cells consist of a dense solid electrolyte membrane and two porous electrodes. In most cases, at least one of the electrodes is exposed to an oxygen-containing gas (often, ambient air), while the other electrode is exposed to an inert gas, a liquid metal, a partial vacuum, or a reacting mixture (hydrogen, water vapor, hydrocarbons, CO, CO2, etc.). The single-chamber reactor (SCR) has been also proposed either as a membrane reactor or as a fuel cell. In this case, the solid-electrolyte disk, with two different electrodes that are coated either on opposite sides or on the same side of the pellet, is suspended in a flow of the reacting mixture (see Section 12.6.3). 

D. Mendes, S. Tosti, A. Mendes, L. M. Madeira, S. Sa, J. M. Sousa, Experimental and modeling studies on the low-temperature water-gas shift reaction in a dense Pd-Ag packed-bed membrane reactor, Chem. Eng. Sci. 66 (2011) 2356-2367. 

---