Abstract
With the ever-increasing demand for natural gas (NG) in the current century, solidified natural gas (SNG) technology is bound to play an indispensable role in enhancing energy resilience and ensuring sufficient energy supply globally. Herein, dioxane was employed as not only an environmentally benign additive but also a dual-function (thermodynamic and kinetic) promoter for hydrate formation in simulated seawater. This approach helps bypass the issue of water scarcity, avoids the utilization of toxic and volatile chemicals, and carries the potential to enhance the methane storage capacity. The three-phase (gas, liquid, and hydrate) equilibrium conditions were measured for mixed CH4/dioxane hydrate formation in simulated seawater. Extensive experiments were conducted at a constant temperature of 283.2 K and various initial pressures (7.5, 9.5, and 11.5 MPa) to investigate the impact of the initial experimental pressure on the kinetics of mixed CH4/dioxane hydrate formation in simulated seawater. Additionally, the application of l-tryptophan (1000 ppm) as a co-promoter or an additional kinetic promoter for the process was studied. At an initial pressure of 11.5 MPa, up to 93.57 (±4.33) v/v methane storage capacity was achieved in simulated seawater containing 5.56 mol % dioxane, while upon the addition of l-tryptophan to the system, the hydrate formation rate at the same initial pressure was increased over 6-fold from 0.51 (±0.08) to 3.13 (±0.06) v/v min–1. The analysis of in situ Raman spectra confirmed the exclusive formation of structure II methane hydrate, despite the formation of structure I methane hydrate being possible from the thermodynamic point of view. The results obtained in the current work contribute to the development of SNG technology via the utilization of seawater.
Published Version
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