The construction of palladium and palladium-alloy supported membranes for hydrogen separation using supercritical fluid deposition
The separation of hydrogen from other light gases is of particular importance to the chemical process industry. Membrane based processes offer a cost effective alternative to traditional processing while allowing the combination of separation and reaction in a single unit. Dense palladium or palladium alloy films are a natural choice for hydrogen separation due to their potential infinite selectivity for hydrogen.
In this dissertation we investigated the construction of palladium-based supported hydrogen separation membranes using Supercritical Fluid Deposition (SFD). Compared to other deposition methods, SFD offers an effective metal deposition approach for porous materials due to its high precursor solubility, rapid mass transfer, and lack of surface tension. Three palladium precursors were evaluated for membrane construction in terms of thermal stability, reactivity and surface selectivity. Pd-X (X = Ag, Ni, or Cu) co-depositions were studied to determine the potential of SFD for direct alloy deposition.
Intrinsic to effective membrane construction is the control of membrane location and thickness. Several different reactor and reactants geometries were utilized to control membrane location. An opposed reactants geometry was used to produce sub-surface membranes at controlled depths (80–600 μm) in porous α-alumina. A same-sided reactants geometry was used to produce surface films ranging in thickness from 100 nm to 5 μm on numerous support materials. Membranes were characterized using a variety of techniques including: SEM, XPS, XRD, EPMA, and gas permeation.
0794: Materials science