Electrochemical Oxygen Separation

Fig. 5. Exploded view of an ion-exchange membrane electrochemical oxygen separator. Oxygen removal characteristics of the flow-through type oxygen removal system are shown. Air cathode area = 100 cm2, water temperature = 40 °C.

As is clear solid oxide electrolytes are not useful for applications as oxygen separation membrane, unless operated with external circuitry (oxygen pump) or as a constituent phase of a dual-phase membrane. Both modes of operation, classified in this paper as electrochemical oxygen separation, are briefly discussed in Section 10.4.3. But we first start with a discussion of the models that have been developed to describe the oxygen semi-permeability of solid oxide... 

Fujita, Y., Nakamura, H., Muto, T. (1986). An electrochemical oxygen separator using an ion-exchange membrane as the electrolyte. Journal of Applied Electrochemistry. 16(6), 935-940. 

Electropox [Electrochemical partial oxidation] Also called Pox. An electrochemical process for oxidizing methane to syngas. It combines the partial oxidation and steam reforming of methane with oxygen separation in a single stage. Invented in 1988 by T. J. Mazanec at BP Chemicals. An industrial-academic consortium to develop the process was formed in 1997. 

M. Liu, Theoretical assessment of oxygen separation rates of mixed conductors, in T.A. Ramanarayanan and H.L. Tuller (Eds.), Ionic and Mixed Conducting Oxide Ceramics 91-12. Electrochemical Society Inc., NJ, 1991, pp. 95-109. 

Electrochemical pumps and compressors that is, devices for dosage, separation, compression or removal of oxygen (or hydrogen), according to Faraday s law. The set-up devoted to separate oxygen from air has been also referred to as either the ion transport membrane (ITM) or solid electrolyte oxygen separation (SEOS) [6]. 

The major routes are oxidation with molecular oxygen or alkaline hydrogen peroxide or electrochemically. The separation of HFPO, bp —27.4°C, from starting hexafluoropropylene, bp —29.4°C, is performed by extractive distillation. ... 

In addition to the oxygen separation membranes, the proton conducting membranes can also be applied to reduce NO emission by combining heterogeneous catalysis and solid state electrochemistry. The solid electrolytes in MRs serve to electrochemically control chemisorptive bonds and enhance catalytic activity. Figure 8.10 shows the schematic diagram of a steam electrolysis cell constructed with a proton conductor for reducing NO. Steam is electrolyzed at the anode. It shows the produced H+ is electrochemically pumped to the cathode and reacts with NO to produce Nj and HjO ... 

Finally, dense ceramic oxide membrane-based eCMRs (Badwal Ciacchi, 2001 Fouletier Ghetta, 2009 Hibino, Ushiki, Kuwahara, 1997), which are available in both planar and tubular designs, have been investigated for O2 separation and compression at HT. Of course, the conventional (non-electrochemical) HT oxygen separation membranes are mixed oxide/electronic ceramics (Badwal Ciacchi, 2001). 

An alternative to gas chromatography is an electrochemical oxygen sensor. These inexpensive probes are commonly used in laboratories for atmospheric determination of oxygen. Connection of this probe to a sensitive multimeter dlows for probe utilization under vacuum, eliminating the need for transport of gases to a separate analytical system. 

Determination of nonstoichiometry in oxides is a key point in the search for new materials for electrochemical applications. In recent decades, owing to their current and potential applications (electrodes in fuel cells, insertion electrodes, membranes of oxygen separation, gas sensors, catalytic materials, etc.), various methods of precise characterization of MfECs have been proposed, either the measurement of the defect concentrations and the stoichiometric ratio as functions of the oxide composition, of the surroxmding oxygen pressure and of temperature, or the transport properties. There are different methods to determine the electrical properties of MIECs and, more specifically, the ionic and electronic contributions. The most appropriate method depends on different parameters, i.e., the total electrical conductivity of the studied oxides, the ionic and electronic transport numbers, the... 

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