Designing internal container architectures to control methane hydrate formation with high energy density

Using sodium dodecyl sulfate (SDS) as a promoter has proven to be one of the most successful strategies for overcoming the inherently low kinetic efficiency of hydrate-based methane storage. However, the porous structure and surface-growth behavior of methane hydrates in the presence of SDS lead to loosely packed hydrate formation within the reactor, resulting in low energy density. In this work, novel containers (33 mm in diameter and 25 mm in height) with specially designed internal walls were fabricated using 3D printing to guide the hydrate growth path and thereby enhance energy density. Distinct from the conventional methane storage capacity in hydrates, we introduce the apparent methane storage capacity of the container—a metric more representative of engineering practice. In experiments conducted with the containers placed inside a sapphire autoclave (7 MPa, 275.15 K) using 1 mmol/L SDS, vertical walls improved methane storage capacity in hydrates but increased the percentage of hydrate growing outside the container. In contrast, horizontal walls effectively prevented hydrate outgrowth but reduced water-to-hydrate conversion efficiency. Interestingly, constructing helical walls successfully combined the benefits of both vertical and horizontal designs. This configuration allowed the methane storage capacity in hydrates to reach 145 ± 5.2 v/v, while reducing the outgrowth to 18.75 %, resulting in an apparent methane storage capacity of 94 ± 7.1 v/v within the container. Even more promising, when the container was optimized into a “labyrinth” structure, the entire hydrate formation process was confined within the reactor. This led to a methane storage capacity in hydrates of 145 ± 5.2 v/v and the highest apparent storage capacity in the container of 104 ± 9.9 v/v. This work demonstrates the feasibility of designing reactors that can simultaneously function as high-density methane storage tanks.