High-Capacity Amine-Imidazole Solvent Blends for CO2 Capture

The CO2 absorption performance of aqueous solvent blends containing four imidazoles (2-MeIm, 2-Et-4-MeIm, 2,4,5-MeIm and 1,2,4,5-MeIm) and four promoters (MEA, DEA, PZ, and MAPA) were investigated using a small-scale screening apparatus. Exceptionally high absorption capacity of 14 and 16 wt % was obtained for 2,4,5-MeIm/PZ and 2,4,5-MeIm/MAPA solutions, respectively. Cyclic capacities as high as 12 wt % were obtained for 3 M 2,4,5-MeIm + 1 M PZ solutions between 40 and 80 °C at 10 kPa CO2. The outstanding performance is the result of selective precipitation of 2,4,5-MeImH+ bicarbonate, allowing the formation of a highly loaded slurry solution. 2,4,5-MeIm/diamine solutions are proposed as a novel type of absorption blend for CO2 capture.