Silver(I) Supported Liquid Membranes for Selective Ethylene Recovery from Mixed-Gas Streams of Tandem CO ₂ Electrolysis

Large-scale olefin separations from unreacted paraffins and other byproduct gases are primarily done by energy-intensive cryogenic distillation processes at refineries. Silver(I) supported liquid membranes (Ag SLMs) can be implemented at smaller production scales of ethylene (C2H4), a critical industrial chemical, such as its electrocatalytic (EC) production from CO2. Challenges of EC C2H4 production mainly stem from reducing gases like hydrogen (H2), where the redox reactions pertinent to Ag(I) facilitators diminish olefin transport. Herein we report that aqueous Ag(I) solution in a composite Ag SLM can operate in mixed-gas conditions containing H2 gas utilizing reduced titania compounds, such as titanium(III) oxide (Ti2O3). Embedding Ti2O3 in the polydimethylsiloxane layer of Ag SLM assisted in selectively separating C2H4 from mixed-gas feed streams related to CO2 electrolysis containing H2. The direct exposure of a mixed-gas stream containing C2H4, CO2, CO, N2, and CH4 with as high as 50 vol % H2 maintained excellent C2H4 separations for 7 days of continuous operation. The Ag SLM provided effective separations of C2H4 from CO (at detection limits), CH4 (selectivity ratio (α) = 20–30), and H2 (α = ∼20), but C2H4 from CO2 (α = 2–4) revealed a slightly lower separation. These data show that aqueous Ag(I) solution(s) used in the SLMs can separate C2H4 for extended periods, even under highly reducing gas conditions. Also, we report C2H4 recovery from the gas mixture produced in the EC CO2 reduction process. The Ag SLM gave C2H4 selective separation from a five-component complex mixed-gas stream, relevant to tandem CO2 electrolysis.