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Abstract

The use of electrochemical membrane absorbers for the purification of waste gases is investigated. In this type of reactor a gas and a liquid phase are brought into contact in the pore structure of a solid gas-diffusion electrode. The gaseous reactant is absorbed and converted by electrochemical reduction or oxidation. A limiting current analysis shows that such membrane systeme can have a better mass transfer intensity than conventional packed-bad absorbers or fluidized bed absorbers. This is demonstrated experimentally for the electrochemical absorption of chlorine in hydrochloric acid. The combination of a cathodic chlorine reduction with an anodic hydrogen oxidation leads to the concept of a membrane absorber which operates as a chlorine/hydrogen fuel cell. The chlorine conversion, the overcall current efficiency, and the fuel cell voltage were measured in dependence of the applied cell current. The importance of crossover phenomena of hydrogen and chlorine in the electrolyte gap is discussed.