With natural gas demand growing rapidly in this century, solidified natural gas technology holds great potential for strengthening energy resilience and delivering secure global gas supply. However, this technology is still impeded by insufficient gas uptake capacity and sluggish hydrate formation rate. Environmentally benign peptides have recently emerged as a novel class of green hydrate promoters. Different from single amino acids, peptides exhibit significant structural diversity owing to their varying sequences and combinations of their constituent amino acid monomers, showing great potential in hydrate-based applications. In this work, a unique tripeptide promoter, L-glutathione reduced (GSH), was employed, and the thermodynamic influence factors in methane hydrate formation were systematically investigated. Furthermore, as a highly hydrophilic amino acid, L-arginine was chosen for a comparative kinetic investigation with extremely hydrophilic GSH. The results revealed that experimental pressure showed a strong effect on the methane uptake rate, while it presented little influence on final methane storage capacity. The initial temperature greatly affected the average induction time, the rate of hydrate growth, and the yields of hydrates promoted by GSH. Increasing temperature resulted in a significant reduction in both the hydrate formation rate and methane uptake at 3 h. Therefore, in the GSH-promoted hydrate formation process, suitable pressure and temperature should be carefully chosen for desirable hydrate performance. Furthermore, the initial 15 min hydrate formation rate of 0.3 wt% L-arginine is 52.4% lower than that of 0.3 wt% GSH. The final methane uptake of 0.3 wt% arginine is substantially smaller than that of 0.3 wt% GSH. Although both GSH and arginine exhibit strong hydrophilic properties, the tripeptide GSH is more effective than the amino acid arginine in enhancing methane hydrate formation. The insights gained from this work offer a theoretical foundation for the application of peptide-based promoters in solidified natural gas technology.
Wan et al. (Thu,) studied this question.