Glass frit sealing method for macroscopic defects in Pd-based composite membranes with application in catalytic membrane reactors

Abstract

A method of sealing defects in thin-film Pd-alloy composite membranes using commercially available glass frit powder is detailed. This technique involves application of a low melting point glass frit and in situ firing in inert gas to seal defects on the order of 1 mm in diameter. In this case, a glass frit with a melting point of 560 °C was found to produce stable seals at 520 °C during a 150 h stability test under pure hydrogen. Changing the feed mixture to 50 % H 2 , 25 % Ar and 25 % steam, however, caused softening and subsequent seal failure at 520 °C. However, stable operation was achieved with water gas-shift mixtures when the temperature was reduced to 400 ºC. The seal is demonstrated to be very robust within ammonia decomposition membrane reactors. Even though the frit seal had direct contact with the catalyst bed, it was observed to be stable in an ammonia decomposition reactor at 520 °C. The catalytic membrane reactor obtained 98 % conversion, producing above 99 % purity hydrogen with a flux of 0.11 mol m-2 s-1 for 150 h with no signs of seal degradation.

Efficient Ammonia Decomposition in a Catalytic Membrane Reactor To Enable Hydrogen Storage and Utilization

“…However, with sufficient hydrogen removal, higher pressure enhances both kinetics and thermodynamics. The ability of membrane reactors to accelerate decomposition kinetics has been demonstrated by a number of investigators. ,− In the typical packed-bed membrane reactor (PBMR) configuration, catalyst particles are packed within the interior or in the annulus surrounding a tubular hydrogen permeable membrane. , Using a 200 μm thick Pd tube, Itoh et al achieved higher conversion in a PBMR relative to a PBR . However, the gains were quite modest, and modeling showed that hydrogen recovery was limited by the low permeance of the thick Pd tube.…”

Microstructural Investigation and On-Site Repair of Thin Pd-Ag Alloy Membranes

“…Lu et al [27] followed metal bonding to repair the palladium film. Lundin et al [28] sealed the defects on the palladium film with glass powder. Zheng et al [29] used homemade "modified" liquid-liquid displacement porometry (MLLDP) to characterize the defect size, followed by the repair of defects in the palladium composite film by filling with high-temperature-resistant silicate gel (HTRSG) composite ceramic particles.…”

Confined and in-situ zeolite synthesis: A novel strategy for defect reparation over dense Pd membranes for hydrogen separation

“…Those large defects can be repaired by filling materials, such as Al 2 O 3 particles [33], glass frit [34] and Pd(OH) 2 colloid [35].…”