(122d) Preventing H2s Poisoning of Pd Membranes for H2 Purification Using Applied Electric Fields
AIChE Annual Meeting
2022
2022 Annual Meeting
Fuels and Petrochemicals Division
Advances in Petroleum Production and Refining
Monday, November 14, 2022 - 1:13pm to 1:28pm
Petroleum refining annually consumes approximately 26 million tons of Hydrogen at a cost of $30 billion. Most of this hydrogen is produced by methane or naphtha reformation, which simultaneously produces several contaminants (H2S, H2O, etc.). This H2 then requires purification which constitutes roughly 1/5 of the total dollar cost and accounts for ~15% of total efficiency losses in the H2 production process. Theoretically, the best separation process would consist of a single step, which could be achieved by a dense Pd metal membrane. However, the prevalence of contaminants, particularly H2S, which poisons and corrodes Pd membranes, prevents their widespread adoption in petroleum refining despite their high H2 flux and selectivity. Here, we use density functional theory to demonstrate a proof of concept for using an applied electric field (AEF) to prevent the decomposition of H2S on the Pd(111) surface. We find that strong (2 V/Å) AEFs oriented toward and away from the Pd surface similarly reduce the adsorption energy of H2S but have conflicting effects on the barrier of S-H scission such that a strong field oriented toward the surface reduces the rate of H2S decomposition. These findings are integrated into a microkinetic analysis which shows no significant surface coverage of Sulfur adatoms at this field strength and orientation. Here, the overall effects of the AEF strength and orientation on the surface electronic density, reaction thermodynamics and kinetics, and surface coverage over time are reported.