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

Hydrate-based H2 purification, taking advantage of the different phase-equilibrium characteristics exhibited by H2 and impurity gases, presents a potential technological avenue with considerable implications for engineering-oriented pursuits. This review encompasses critical aspects relating to H2 gas purification techniques, including a rigorous comparative analysis between established H2 purification approaches and the hydrate-based method. Hydrate-based H2 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 H2-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 H2 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 H2 purification, focusing prominently on the hydrate-based method as the forefront of investigation.