(268d) Development of Dense Cermet Membranes for Hydrogen Separation

Argonne National Laboratory (ANL) is developing dense ceramic membranes for separating hydrogen from mixed gases, particularly product streams generated during coal gasification and/or methane reforming. Hydrogen separation with these membranes is nongalvanic, i.e., it does not use electrodes or an external power supply to drive the separation, and hydrogen separated from the feed stream is of high purity, so post separation purification steps are unnecessary. Dense cermet (i.e., ceramic-metal composite) membranes have been developed to separate hydrogen from gas mixtures at high temperature and pressure. The hydrogen permeation rate, or flux, measured at atmospheric pressure in the temperature range of 500-900°C, varied linearly with the inverse of membrane thickness, and reached ≈19 cm³[STP]/min-cm²at 900°C for an ≈20-μm-thick membrane when 100% H₂was the feed gas. The effects of membrane thickness and hydrogen partial pressure on flux indicated that bulk diffusion of hydrogen is the rate-limiting step. A thin film of the cermet membrane on a porous support structure gave a flux of ≈33 cm³[STP]/min-cm² at 900°C when 100% H₂ was the feed gas. The hydrogen flux also varied with the microstructure of the cermet. When some of the membranes were tested in a gas mixture that contained high concentrations of CH₄, CO and CO₂ for times that approached ≈500 h, no performance degradation was observed. Hydrogen flux measurements in H₂S-containing atmospheres show that the cermet membranes are stable for up to 1200 h in gases that contain 400 ppm H₂S. These results suggest that the membranes are chemically stable and may be suitable for long-term operation. The present status of membrane development at ANL will be presented in this talk. Work supported by U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory's Hydrogen and Gasification Technologies Program, under Contract W-31-109-Eng-38.