Methane Storage in Simulated Seawater Enabled by 1,3-Dioxane as an Environmentally Benign Promoter

With the ever-increasing demand for natural gas (NG)in the currentcentury, solidified natural gas (SNG) technology is bound to playan indispensable role in enhancing energy resilience and ensuringsufficient energy supply globally. Herein, dioxane was employed asnot only an environmentally benign additive but also a dual-function(thermodynamic and kinetic) promoter for hydrate formation in simulatedseawater. This approach helps bypass the issue of water scarcity,avoids the utilization of toxic and volatile chemicals, and carriesthe potential to enhance the methane storage capacity. The three-phase(gas, liquid, and hydrate) equilibrium conditions were measured formixed CH4/dioxane hydrate formation in simulated seawater.Extensive experiments were conducted at a constant temperature of283.2 K and various initial pressures (7.5, 9.5, and 11.5 MPa) toinvestigate the impact of the initial experimental pressure on thekinetics of mixed CH4/dioxane hydrate formation in simulatedseawater. Additionally, the application of l-tryptophan (1000ppm) as a co-promoter or an additional kinetic promoter for the processwas 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 containing5.56 mol % dioxane, while upon the addition of l-tryptophanto the system, the hydrate formation rate at the same initial pressurewas 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 IImethane hydrate, despite the formation of structure I methane hydratebeing possible from the thermodynamic point of view. The results obtainedin the current work contribute to the development of SNG technologyvia the utilization of seawater.

Automated summary

With the increasing demand for natural gas in the current century, solidified natural gas technology is expected to play a vital role in enhancing energy resilience and ensuring sufficient energy supply globally. In this study, dioxane was used as an environmentally friendly additive and a dual-function promoter for hydrate formation in simulated seawater, addressing the issues of water scarcity and the use of toxic chemicals, and potentially increasing methane storage capacity.