Carbon dioxide capture from model marine diesel engine exhaust by means of K2CO3-based sorbents

The on-board ship installation of a high-efficiency and low-cost CO2 separation unit seems to be an attractive option to comply with recent regulations aimed at reducing the carbon footprint derived from the maritime sector. Our research group is currently developing a capture and storage scheme based on the use of potassium carbonate for CO2 conversion into solid potassium bicarbonate. In this paper, we summarize preliminary CO2 capture tests on both raw and alumina-supported K2CO3 carried out in a fixed bed apparatus under typical model marine diesel engine exhaust composition (CO2 5 %, H2O 5 %, N2 90 % by vol.) and temperatures (60 - 105 °C). Carbonation data for the parent bulk K2CO3 showed a maximum capture capacity of 0.138 mmol g-1 corresponding to a nearly 2 % sorbent utilization factor. An increase in the operating temperature produced a reduction of the carbonation capacity and faster capture kinetics. The alumina-supported sorbent tested at 60 °C displayed enhanced CO2 capture capacity with a maximum conversion degree of 43 %. This testifies the positive effect derived by the dispersion of the active phase onto a substrate with large surface area in the CO2 capture process, likely for a remarkable reduction of diffusion limitations during the carbonation reaction in the case of nano-sized potassium carbonate with respect to granular sorbents.