Chemically Modified Biopromoters Based on Amino Acids and Gluconic Acid for Enhanced Methane Hydrate Formation

The formation of methane hydrates is a promising route for safe and efficient natural gas storage, but slow nucleation kinetics and foaming from surfactant promoters hinder their practical use. To address these challenges, this study evaluates a new class of highly effective kinetic biopromoters synthesized from d-glucono-1,5-lactone and 11 amino acids (GDL+AA). Methane hydrate formation was investigated in high-pressure autoclaves under static and dynamic conditions, complemented by differential scanning calorimetry (DSC), visual observation, pelletization, stability testing, molecular dynamics, and quantum chemical simulations. GDL+AA compounds exhibited a pronounced promoting effect at low concentration (0.05 wt %), initiating hydrate formation in 19–25 min compared with 54 min for sodium dodecyl sulfate (SDS) and 45 min for the unmodified amino acids. Methane uptake reached 0.160 mol/mol, and water-to-hydrate conversion was 88–96% in high-pressure autoclave tests. DSC experiments confirmed higher hydrate formation onset temperature (−9 °C for GDL+Met vs SDS: −16 °C; Met: −16 °C) and higher water to hydrate conversion (99.3% for GDL+Met vs SDS: 70.0%; Met: 28.7%). Visual observations under static conditions corroborated accelerated hydrate growth. Molecular dynamics and quantum-chemical calculations elucidated the mechanism of action of the GDL+AA derivatives. No foaming occurred in the GDL+AA systems during formation or dissociation. Hydrate pellets from GDL+AA showed high density and mechanical strength and high methane retention stability for engineering applications. Chemical modification with gluconic acid significantly enhanced the kinetic performance compared with unmodified amino acids. The synthesis is water-based and mild and uses biocompatible, biodegradable materials, aligning with green chemistry principles. GDL+AA compounds are scalable, efficient, and environmentally sustainable promoters of solidified natural gas.