A comprehensive review of hydrogen purification using a hydrate-based method

Hydrate-based H purification, taking advantage of the different phase-equilibrium characteristics exhibited by H and impurity gases, presents a potential technological avenue with considerable implications for engineering-oriented pursuits. This review encompasses critical aspects relating to H gas purification techniques, including a rigorous comparative analysis between established H purification approaches and the hydrate-based method. Hydrate-based H purification has the advantage of having a low cost of raw materials, but the harsh thermodynamic and kinetic conditions of hydrate formation have hindered the development of this technology. Researchers are endeavoring to devise solutions for these challenges by exploring aspects such as hydrate crystal microstructure, hydrate thermodynamics, kinetics, and more. An extensive investigation has been conducted into the microstructure of H-involved hydrate, coupled with an examination of the thermodynamics governing the hydrate phase equilibrium. It is suggested that the prudent selection of an appropriate additive type and concentration, balancing hydrate formation conditions and impurity gas occupancy, is paramount. Furthermore, the kinetics properties of hydrate nucleation, formation, and H purification are summarized. Although additives, the physical method, and synergistic approaches demonstrated a notable enhancement in kinetic performance, the associated expenditure was overlooked inadvertently. The primary objective of this review is to facilitate a comprehensive understanding of the advances and challenges in H purification, focusing prominently on the hydrate-based method as the forefront of investigation.