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Title: Mixed Ionic and Electonic Conductors for Hydrogen Generation and Separation: A New Approach

Abstract

Composite mixed conductors comprising one electronic conducting phase, and one ionic conducting phase (MIECs) have been developed in this work. Such MIECs have applications in generating and separating hydrogen from hydrocarbon fuels at high process rates and high purities. The ionic conducting phase comprises of rare-earth doped ceria and the electronic conducting phase of rare-earth doped strontium titanate. These compositions are ideally suited for the hydrogen separation application. In the process studied in this project, steam at high temperatures is fed to one side of the MIEC membrane and hydrocarbon fuel or reformed hydrocarbon fuel to the other side of the membrane. Oxygen is transported from the steam side to the fuel side down the electrochemical potential gradient thereby enriching the steam side flow in hydrogen. The remnant water vapor can then be condensed to obtain high purity hydrogen. In this work we have shown that two-phase MIECs comprising rare-earth ceria as the ionic conductor and doped-strontium titanate as the electronic conductor are stable in the operating environment of the MIEC. Further, no adverse reaction products are formed when these phases are in contact at elevated temperatures. The composite MIECs have been characterized using a transient electrical conductivity relaxation techniquemore » to measure the oxygen chemical diffusivity and the surface exchange coefficient. Oxygen permeation and hydrogen generation rates have been measured under a range of process conditions and the results have been fit to a model which incorporates the oxygen chemical diffusivity and the surface exchange coefficient from the transient measurements.« less

Authors:
Publication Date:
Research Org.:
Trustees Of Boston University
Sponsoring Org.:
USDOE
OSTI Identifier:
949960
DOE Contract Number:  
FC26-03NT41958
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ELECTRIC CONDUCTIVITY; HYDROCARBONS; HYDROGEN; MEMBRANES; OXYGEN; RELAXATION; STEAM; STRONTIUM TITANATES; TITANATES; TRANSIENTS; WATER VAPOR

Citation Formats

Srikanth Gopalan. Mixed Ionic and Electonic Conductors for Hydrogen Generation and Separation: A New Approach. United States: N. p., 2006. Web. doi:10.2172/949960.
Srikanth Gopalan. Mixed Ionic and Electonic Conductors for Hydrogen Generation and Separation: A New Approach. United States. doi:10.2172/949960.
Srikanth Gopalan. Sun . "Mixed Ionic and Electonic Conductors for Hydrogen Generation and Separation: A New Approach". United States. doi:10.2172/949960. https://www.osti.gov/servlets/purl/949960.
@article{osti_949960,
title = {Mixed Ionic and Electonic Conductors for Hydrogen Generation and Separation: A New Approach},
author = {Srikanth Gopalan},
abstractNote = {Composite mixed conductors comprising one electronic conducting phase, and one ionic conducting phase (MIECs) have been developed in this work. Such MIECs have applications in generating and separating hydrogen from hydrocarbon fuels at high process rates and high purities. The ionic conducting phase comprises of rare-earth doped ceria and the electronic conducting phase of rare-earth doped strontium titanate. These compositions are ideally suited for the hydrogen separation application. In the process studied in this project, steam at high temperatures is fed to one side of the MIEC membrane and hydrocarbon fuel or reformed hydrocarbon fuel to the other side of the membrane. Oxygen is transported from the steam side to the fuel side down the electrochemical potential gradient thereby enriching the steam side flow in hydrogen. The remnant water vapor can then be condensed to obtain high purity hydrogen. In this work we have shown that two-phase MIECs comprising rare-earth ceria as the ionic conductor and doped-strontium titanate as the electronic conductor are stable in the operating environment of the MIEC. Further, no adverse reaction products are formed when these phases are in contact at elevated temperatures. The composite MIECs have been characterized using a transient electrical conductivity relaxation technique to measure the oxygen chemical diffusivity and the surface exchange coefficient. Oxygen permeation and hydrogen generation rates have been measured under a range of process conditions and the results have been fit to a model which incorporates the oxygen chemical diffusivity and the surface exchange coefficient from the transient measurements.},
doi = {10.2172/949960},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 2006},
month = {Sun Dec 31 00:00:00 EST 2006}
}

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