Capturing and In-Situ Conversion of CO2 into Carbonates from Simulated Marine Engine Exhaust Gases via Various Amino Acid Salts

Onboard carbon capture has been recognized as a crucial strategy for mitigating CO₂ emissions in the maritime sector. In the present paper, an integrated absorption and mineralization method using a blend of amino acid salts with alkaline minerals was employed to capture and directly convert CO₂ into carbonate from simulated marine engine exhaust gas. The primary objective of this study is to evaluate the effects of various amino acid salt categories on the performance of CO₂ capture, conversion, and the formation of carbonate polymorphs. The results reveal that specific amino acid salts, particularly the linear potassium glycinate and cyclic potassium proline, in conjunction with magnesium hydroxide, exhibit CO₂ capture efficiencies surpassing 80%, accompanied by conversion efficiencies exceeding 95%. Poly amino acid salt potassium arginate, when paired with calcium hydroxide, yields a CO₂ capture efficiency of 96.5% and achieves 100% conversion. However, regardless of the type of amino acid salt, the crystallographic forms of magnesium or calcium carbonates exhibit a remarkable uniformity, specifically as nesquhonite and calcite, respectively. Notably, certain sterically hindered amino acid salts, such as potassium valinate and potassium isoleucinate, exhibit a capacity to direct the oriented growth of carbonates, leading to the formation of crystalline particles of substantial size. The research outcomes presented herein offer significant insights for the selection of absorbents within the context of shipborne CO₂ capture and mineralization integration technologies, with the objective of achieving high-efficiency absorption and conversion processes alongside the attainment of controllable product morphologies.