Silver(I) Supported Liquid Membranes for Selective Ethylene Recovery from Mixed-Gas Streams of Tandem CO2 Electrolysis

Large-scale olefin separations from unreacted paraffins and other by-product gases is 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 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 by strategically utilizing reduced titania compounds, such as titanium (III) oxide (Ti2O3). We found that embedding Ti2O3 in polydimethylsiloxane layer of Ag SLM assisted in selectively separating C2H4 from mixed-gas feed streams related to CO2 electrolysis containing H2. We unveil that 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 seven days of continuous operation. This demonstrates effective separation of C2H4 from CO (at detection limits), CH4 [separation ratio (a) = 20-30], and H2 [a = ~20]. However, C2H4 selectivity over CO2 (a = 2-4) revealed slightly lower separation. This shows that aqueous Ag(I) solution(s) used in the SLMs can separate C2H4 for extended periods, even under highly reducing gas conditions. Essentially, we report an easily-fabricated composite Ag SLM that can provide C2H4 recovery in mixed-gas streams, such as EC CO2 reduction to C2H4 production. The use of Ag SLM allowing such high C2H4 selective separation from a five-component complex mixed-gas stream, relevant to tandem CO2 electrolysis, in the presence of 50 vol% of H2 remains hitherto unprecedented.. Authors: Klaehn, John R [Idaho National Laboratory] (ORCID:0000000270774509); Mukhopadhyay, Arindam [Idaho National Laboratory] (ORCID:0000000206204157); Orme, Christopher J [Idaho National Laboratory] (ORCID:0000000225985737); Diaz,, Luis A. [Redwood Materials]; Molina Montes de Oca, Daniel Ernesto [Idaho National Laboratory] (ORCID:0000000232249631). DOE Contract: AC07-05ID14517. Subjects: 37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Olefin facilitation; carbon dioxide; electrochemical ethylene production; ethylene; ethylene separation; facilitated transport; hydrogen; mixed-gas permeance; silver; supported liquid membrane