Dissolution-driven CO₂/CH₄ separation via gas hydrates: Mechanism-guided process optimisation

Efficient gas capture and separation are critical for improving energy efficiency and mitigating greenhouse gas emissions. Among various technologies, hydrate-based gas separation represents a promising low-carbon approach because of its potential for selective gas capture under relatively mild conditions. Although this topic has been widely investigated, clear guidelines for defining optimal operating conditions and process-level control strategies remain unavailable, hindering their large-scale practical application. Here, a CH₄/CO₂ mixed-gas system is investigated using an integrated molecular dynamics and experimental framework to identify the operating parameters governing separation efficiency. The results indicated that efficient CO₂ separation can be achieved in water–gas separated systems where a strong interfacial dissolution gradient is maintained. CO₂ is preferentially captured at the early stage of hydrate formation due to its higher solubility and faster dissolution into water, resulting in a higher CO₂ fraction in the hydrate phase than in the gas phase. The hydrate formation rate is also closely related to this dissolution-driven process. Temperature and bubble size were found to strongly regulate the separation performance with an optimal operational window identified at 260 K and a specific gas concentration, defined as a methane/water mole ratio of 0.1231. In contrast, well-mixed gas–water systems eliminate dissolution differences, causing CO₂ and CH₄ to exhibit similar dissolution and capture behaviors and resulting in poor selectivity. By integrating these performance-regulating factors into a Weighted Sum Model (WSM), this work provides a systematic basis for evaluating operating conditions, supporting the development of hydrate-based gas purification and storage processes from a process-intensification perspective. • Dissolution-driven mechanism governs CO₂/CH₄ separation selectivity. • CO₂ solubility and dissolution kinetics promote CO₂ enrichment during hydrate formation. • An optimal temperature and gas concentration window balances gas selectivity and capture flux. • Interfacial dissolution gradients control separation performance under operating conditions.