Preparation of potassium intercalated carbons by in-situ activation and speciation for CO2 capture from flue gas

Abstract

Nitrogen and/or sulfur doped carbons were extensively investigated as CO2 adsorbents, however their performance in CO2 capture from combustion flue gas, which is the largest stationary emission source, was less promising. Herein, potassium was used as a dopant for carbon, and a new series of materials, namely potassium intercalated carbons (PICs), were prepared sequentially by oxidation of mesoporous carbon, potassium ion exchange, and calcination. Based on results from FT-IR, XPS, TG-MS, etc., it was found the pre-loaded potassium interacted with the carbon matrix during calcination, enabled great flexibility in: (1) porosity adjustment by “in-situ activation”, and (2) surface chemistry manipulation by potassium intercalation. Taking together, the optimized sample (PIC-700) showed fast and stable CO2 uptake of 5.23 wt.% in flue gas conditions (40 °C, 1 bar, 15%CO2), which is among the highest for carbon-based adsorbents. Such promising performance is directly related to the enhanced CO2 affinity due to the presence of potassium dopants. Dynamic separation of CO2 from 15%CO2/85%N2 showed similar adsorption capacity, and no performance decay could be observed during temperature swing cycles, demonstrating the great potential for the PICs for practical CO2 capture applications.