New Amine-Based Membranes for Post- and Pre-Combustion CO2 Capture

This presentation covers new advances in amine-containing membranes for post-combustion CO₂ capture from flue gas in coal- and/or natural gas-fired power plants and pre-combustion CO₂ capture from synthesis gas derived from coal and/or natural gas. We have synthesized highly CO₂-selective membranes comprising fixed-site and mobile carriers, involving the facilitated transport mechanism based on reversible CO₂ reactions with amine carriers. The membranes remove H₂S even faster than CO₂. In general, the membranes need to be tailor-made and tuned specifically for those applications. For example, post-combustion carbon capture requires a high CO₂/N₂ selectivity of 140 together with a very high CO₂ permeance of greater than 700 GPU in order to use a stand-alone membrane process. We have synthesized composite membranes showing a high CO₂ permeance of about 1500 GPU and a high CO₂/N₂ selectivity of more than 180, which are well above the 2008 Robeson upper bound. The membrane was scaled up successfully to 14 inches in width, and it was fabricated into spiral-wound membrane modules up to a membrane area of about 3 m². Three modules each with 1.4 m² were tested at NCCC, and they showed the same performance as those tested at OSU using simulated flue gas, including excellent membrane stability. The modules are promising for meeting the DOE cost target set for 2025. On the other hand, pre-combustion carbon capture demands the membrane with a very high CO₂/H₂ selectivity of 100 along with a modest CO₂ permeance of about 200 GPU. We have synthesized composite membranes exhibiting 206 GPU CO₂ permeance with 103 CO₂/H₂ selectivity. Based on the synthesized membranes with tuned H₂S/CO₂ selectivities, a one-stage membrane process for pre-combustion carbon capture has been proposed and designed, indicating 6 ppm H₂S in the H₂ product achievable and an attractive increase in the cost of electricity (15.66%).