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Several decades of research by Air Products and Ceramatec have recently culminated in the construction and operation of a test unit with the capacity to produce up to 100 tons per day of oxygen using planar, ceramic mixed conducting, ion transport membranes (ITM). In the first tonnage operation of this unit, over 16 tons/day of oxygen were produced. Smaller scale experiments demonstrated high purity oxygen production for over 15000 hours. A parallel development effort has produced planar ceramic mixed conducting membranes to partially oxidize methane to produce syngas.

A novel process employing solid electrolyte-based ion-transport membranes enables the production of high-purity oxygen at elevated pressure from a feed stream of ambient pressure air. This technology exploits the theoretically infinite selectivity of oxygen ion migration through a dense ceramic electrolyte membrane under the influence of an externally applied electrical potential. The solid electrolyte is derived from cerium oxide, with dopants added to enhance both ion transport and membrane processability. The oxidation and reduction reactions are promoted by the use of porous perovskite electrodes, which together with the electrolyte form an electrochemical cell. Stacks comprising multiple cells in a planar configuration have demonstrated excellent electrochemical performance and stability, mechanical integrity, and the capacity to produce high-purity oxygen over thousands of hours. An oxygen generator based on this technology must incorporate an integrated thermal management system, air mover, power supply, and control systems.High-purity oxygen is supplied commercially to many consumers as compressed gas in cylinders and as liquid in dewars or tanker trucks. Specific grades of product are available with purities that range from 99.5% to greater than 99.998% oxygen. The distribution and handling requirements for these products necessitate a significant infrastructure. For applications requiring oxygen purities of less than 93%, adsorption separation technology has provided some consumers with an economical option for oxygen produced on-site. Consumers demanding higher purity oxygen, however, currently have no alternative to distributed oxygen and its associated infrastructure requirements. A new technology employing an ion transport membranes ͑ITMs͒ has the potential to provide many of these consumers with economical, high-purity oxygen via on-site generation. 1 The ITM solid electrolyte oxygen separation ͑SEOS͒ technology is based on the principle of oxygen ion migration through a dense ceramic electrolyte membrane under the influence of an externally applied electrical potential, as illustrated in Fig. 1. The relationship between the equilibrium oxygen partial pressures on the anode and cathode side of the electrolyte is governed by the Nernst equationRemoval of the oxygen product from the anode side of the electrolyte membrane results in the continuous production of pure oxygen. The ITM SEOS process enables the production of high-purity oxygen at elevated pressure from a feed stream of ambient pressure air. Stack ComponentsElectrolyte.-The core of ITM SEOS technology is an electrochemical stack fabricated from high-temperature conductive ceramic materials. 2 The solid electrolyte is based on cerium oxide, with dopants added to enhance both ion transport and membrane processability. To achieve sufficient oxygen ion conductivity through the electrolyte, the device must be operated at a temperature above approximately 600°C. At these temperatures, doped ceria exhibits a significant performance advantage over ...

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This paper outlines the development status, issues, and applications of several solid electrolyte electrochemical devices currently being developed by Ceramatec and its partners. Ceramatec and its commercial partner Air Products and Chemicals, Inc., (APCI) have successfully developed and demonstrated an electrochemical device that utilizes a ceria-based, solid electrolyte to separate oxygen from air [1,2]. Other oxygen separator projects utilize ion transport membrane(s) (ITM) composed of mixed ionic and electronic conductors to transport oxygen ions across the membrane by means of a pressure differential driving force to generate high purity oxygen or a chemical reaction driving force to produce synthesis gas from methane (ITM Syngas).Ceramatec, in partnership with SOFCo, demonstrated kilowatt class solid oxide fuel cell (SOFC) stacks operating on a variety of fuels such as pipeline natural gas and reformed diesel. Ceramatec is presently working with Cummins and SOFCo to develop low cost modular fuel cells under the Department of Energy's Solid-state Energy Conversion Alliance (SECA) initiative. Some of Ceramatec's other programs are focused on development of gallate electrolyte based fuel cells [3] and metallic bipolar plates [4] for lower temperature operation.