(131c) Contaminant Resistant High-Temperature Hydrogen Purification Membrane

Hydrogen is a key building block of many chemical processes. Hydrogen can be produced in several ways, but economically the most important processes involve producing hydrogen from hydrocarbons. Fossil fuels including coal, oil and natural gas currently are the main sources of hydrocarbons for hydrogen production and biomass is an emerging one. Gas streams generated by hydrogen production from all of these hydrocarbon sources contain corrosive gases such as hydrogen sulfide (H₂S) and halides that attack metals on contact. Competitive hydrogen purification technologies such as pressure swing adsorption require high capital and operating cost. Membrane technology is the method-of-choice because of its low energy requirement, simplicity and a well established process. The most promising membrane materials for hydrogen purification are palladium and its alloys because of their high selectivity and permeability and high temperature tolerance.  However, the critical downside is low tolerance for impurities, hydrogen sulfide, in particular.  Conventional approaches to sulfur resistance improvement such as binary (e.g. Pd-Cu) or tertiary (e.g. Pd-Cu-Au) alloy often result in moderate gain at the expense of loss of permeance. The reason why these metals are active enough to transport hydrogen is also the reason why they react with reactive gases in the gas stream.

MembraGuard^TM technology is a different approach. MembraGuard^TM technology is a protective coating for hydrogen permeable metal membranes. MembraGuard^TM coating provides protection not only for sulfur componds, but for other reactive gases, such as halides and carbon monoxide. MembraGuard^TM coated membrane has high hydrogen selectivity and permeance under elevated temperature and yet is highly resistant to hydrogen sulfide. MembraGuard coated membrane was tested under elevated temperatures and pressures. Thermal resistance was demonstrated under repeated thermal cycles. Palladium membrane without any protective coating lost half of its permeability within 1 hour of contact with hydrogen sulfide. MembraGuard coated palladium membrane was demonstrated to resist hydrogen sulfide at high level with no degradation of performance for extended period. Mixed gas condition including H₂, CO, CO₂, H₂O and H₂S was also tested and MembraGuard coating was proved to be effective under the mixed gas condition.