Synergistic Promotion of CO2 Hydrate Formation by Hydrophilic/Hydrophobic Amino Acids: Experiment and Mechanism

Abstract The development of environmentally friendly promoters is a critical frontier in hydrate-based carbon capture and storage technologies. In this study, the effects of hydrophilic glutamic acid and hydrophobic tryptophan on induction time and gas storage capacity were investigated. Experimental results demonstrate that glutamic acid significantly accelerates formation kinetics, shortening the induction time of to 23 min at 0.3 wt %, which represents an 80.83% reduction compared to pure water. Meanwhile, tryptophan excels in enhancing storage capacity, reaching a maximum of 129.00 m3/m3 at 0.5 wt %, which is 5.6 times that of the control. To address the limitations associated with single amino acids and explore the potential of a compound system, hydrate formation experiments were conducted using a combination of hydrophilic and hydrophobic amino acids. The optimal binary combination of 0.1 wt % glutamic acid and 0.1 wt % tryptophan exhibited a remarkable synergistic effect by reducing the induction time to 8.5 min, a 92.92% reduction, and increasing gas storage capacity to 135.25 m3/m3, which is 5.88 times that of the control. Spectroscopic analysis reveals that this enhancement stems from the formation of dense intermolecular hydrogen-bond networks and optimized gas–liquid interfacial properties. Furthermore, surface tension measurements confirm a significant reduction to 64.891 mN/m, effectively minimizing interfacial mass transfer resistance. Additionally, differential scanning calorimetry (DSC) provides thermodynamic evidence that this synergistic network substantially enhances the structural stability of the formed hydrates. This work elucidates the synergistic mechanism of amino acid blends and provides theoretical support for the development of efficient and eco-friendly promoters for hydrate-based carbon capture.