The Role of Stirring and Amino Acid Mixtures to Surpass the Sluggishness of CO_2 Hydrates

摘要

Clathrate hydrates are attractive materials for storing greenhouse gases such as methane (CH4) and carbon dioxide (CO2). Inefficient water-to-hydrate conversion and sluggishness in kinetics are significant impeding factors. Some additives in lower dosages help accelerate the hydrate conversion process. The aqueous solution with amino acids (0.5 wt %), lphenylalanine (l-phe), and l-threonine (l-thr) inhibits the CO2 hydrate formation in static (0 rpm) conditions. However, l-methionine (l-met) and l-valine (l-val) are promoters under these conditions. A mild stirring (= 100 rpm) of the aqueous solution favored the hydrate conversion. The overall gas uptake, under continuous stirring, progressively increased by about 15-20%. Another way to improve the storage capacity in l-phe and l-thr aqueous systems in the static reactor is by adding a small quantity of aqueous solutions of l-met or l-val (20% by volume). The overall gas uptake and kinetics under static conditions significantly improved in the l-thr dominant system. However, the gas uptake synergistically improved in mixed solutions with l-phe and l-met, while the gas uptake was insignificant in solution with l-phe and l-val.