Silver ions in facilitated transport membranes are often unstable under desirable operating conditions for facilitated transport of olefins. Upon exposure to hydrogen gas, the silver ions irreversibly reduce to elemental silver and become immobilized within the membrane, limiting the ability of these membranes to be effective for long-term use. Current technologies aimed at suppressing this problem involve adding small amounts of a hydrogen peroxide and nitric acid solution to the facilitated solvent to stabilize the silver ions against precipitation. However, this approach consumes the hydrogen peroxide and it must be replenished, presenting an additional cost.
Researchers at The University of Texas at Austin have developed a facilitated transport membrane wherein the silver ions are dissolved in an ionic liquid and immobilized in a porous support. An ionic liquid supported membrane with solvated silver ions can be used to effectively remove olefins from paraffin, as a part of a two-step separation following the catalytic dehydrogenation process. This strategy allows for the long-term use of silver ion carriers within the membrane without the fear of reducing them when exposed to hydrogen gas. Maintaining the silver ions within the membrane allows for its prolonged use for olefin/paraffin selectivity.