Comparison of CO2/H2/H2O Hydrate Formation Processes with Different Promoters

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Hydrate-based gas separation or storage has been proposed and developed as one of the most promising technologies due to the high efficiency and low cost, but promoters are crucial for the hydrate formation process. In this work, the CO2/H2/H2O hydrate formation processes with tetra-n-butyl ammonium bromide (TBAB), tetrahydrofuran (THF) and cyclopentane (CP) with or without memory effect were compared in terms of both kinetic curves and Raman spectrum, respectively. All the hydrates were formed with similar concentration at the same temperature and pressure with and without memory effect. It was found that, among the three additives with fresh water, THF has the best promotion effect on the hydrate formation rate while TBAB has the best promotion effect on the hydrate formation amount. Among the three additives with memory water, TBAB has the best promotion effect on both the hydrate formation rate and hydrate formation amount. Furthermore, the Raman spectrum reveals that the CO2 molecules are enclathrated in the S-cages of structure-II hydrate for the CO2/H2/H2O hydrate formed with THF or CP.