Predictions of Sulfur Resistance in Metal Membranes for H₂ Purification Using First-Principles Calculations

Abstract

Contamination of metal films by sulfur-containing compounds presents a major challenge to using metal membranes for H 2 purification in processes involving large-scale gasification of coal or biomass. Formation of bulk sulfide phases in these applications is typically associated with irreversible loss of performance and ultimately membrane failure. The concept of using metal alloys to reduce sensitivity to sulfide formation has been explored in a variety of experiments, but development of alloys for this purpose has been hampered by a lack of thermodynamic data on formation of the relevant sulfide phases. We show that first principles calculations using density functional theory can be used to predict the formation of bulk sulfide phases from metal alloys under conditions that are relevant for operation of metal membranes. Our methods are illustrated by assessing the formation of sulfides for PdAg, PdAu, and PdCu alloys of all possible binary compositions.

Selection of Surface Coatings for High H2 Permeability Group 5 Metal Membranes Using First-Principles Calculations

“…Historically, Pd-based membranes dominate research and industrial practice for metal membranes applied to H 2 purification because they can naturally catalyze H 2 dissociation/recombination on the surface and have high H 2 permeability across a wide range of temperatures. − Pure Pd membranes have limitations, including being prone to H 2 -induced embrittlement below 300 °C and poisoning by S-containing species . To reduce the embrittlement problem and improve resistance to poisoning, Pd–Ag, Pd–Au, Pd–Cu, and other alloys have been investigated. − Experimental and theoretical methods have also been employed to develop and screen amorphous metal membranes. − The search for durable and cost-effective metal membranes with high H 2 permeability continues to be an active area . Among non-Pd metals considered as candidates for membranes, group 5 metals (V, Nb, and Ta) and related alloys have greater theoretical H 2 permeability than Pd.…”

First-Principles Models of Facilitating H2 Transport through Metal Films Using Spillover

“…Pure Pd membranes, however, are prone to H 2 -induced embrittlement at temperatures below 300 °C and to sulfur poisoning. To improve the performance of pure metal membranes, alloying Pd with other metals such as Ag, Au, or Cu has been tested to reduce the embrittlement problem and in some cases improve resistance to poisoning. − Work has also been performed to develop amorphous metal membranes. , One important feature of amorphous metal membranes is that the short-range order structure may intrinsically reduce problems associated with embrittlement. Theoretical methods have been used to screen amorphous materials for better permeability of hydrogen. − Even though a large number of crystalline and amorphous alloys have been considered with theoretical and experimental methods, the search for durable and cost-effective metal membranes that show high permeability for H 2 continues to be an active area …”