Evaluation of Leucine in Hydrate-based CO2 Separation Technology for Synthesized Mixture Gas

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To increase the combustion calorific value, reduce the greenhouse effect of CO2, and prevent corrosion to pipelines, impurity gases such as CO2 and N2 in biogas must be effectively removed. This study investigates the effects of leucine (Leu) on the kinetics and gas separation efficiency of synthesized ternary (CH4/CO2/N2) gas hydrate formation. The experimental work involved monitoring pressure drop, gas consumption, CH4 recovery, CO2 capture, and separation factor under various conditions of pressure, temperature, and Leu concentration. Advanced characterization techniques, including powder X-ray diffraction, Raman spectroscopy, and Cryo-SEM, were employed to analyze hydrate structure, cage occupancy, and crystal morphology. The key findings indicate that 0.5 wt % Leu optimally promotes formation kinetics and enhances gas separation at medium pressures and high supercooling. A trade-off relationship between CH4 recovery and CO2 capture was observed, influenced by Leu concentration and the degree of supercooling. Structural analysis confirmed the formation of sI hydrate with co-occupancy of gas molecules, while morphological studies showed that increased Leu concentration leads to a denser, more uniform crystal arrangement. The promotion mechanism is attributed to the adsorption of Leu’s hydrophobic groups at the hydrate interface, which enhances gas–liquid mass transfer and facilitates nucleation and growth, thereby improving overall kinetic performance and separation effectiveness.