Review of H2/CH4 separation via pressure swing adsorption: Separation characteristics, competitive adsorption exploration, and functionalised methods on adsorbents

[Display omitted] •Integrate competitive adsorption information on adsorbents for H2/CH4 separation mechanisms.•Integrate mass transfer phenomenon in columns to reveal H2/CH4 separation mechanisms.•Analysis of influence of adsorbent physical and chemical properties (particle size, voids, framework, etc.)•Analysis of influence of operating conditions on H2/CH4 separation characteristics.•Process and molecular simulations, and experimental measurements to explore gas adsorptionauto.•Summary of methods used for adsorbent modification. Grey hydrogen purification is crucial in the H2 industry, with the majority of grey hydrogen(H2) purification processes requiring H2 and methane(CH4) separation. CH4 is the primary impurity in scenarios involving ethylene tail and refinery tail gases. The process operation is contingent upon the adsorption characteristics of H2 and CH4, including the mass transfer and thermal effects within the column. Additionally, the physicochemical properties of the adsorbents, such as particle size, void ratio, framework, active sites, and the operating conditions, jointly determine the gas adsorption characteristics. However, the extant research on the H2/CH4 adorption and separation characteristics does not analyse the gas mass transfer process in conjunction with information on the adsorbents. This omission results in a failure to illustrate the H2/CH4 separation mechanism in the column. Herein, the existing research on H2/CH4 separation adsorbents and their adsorption characteristics is presented. Furthermore, the inherent challenges in elucidating the H2/CH4 adsorption-separation mechanism are analysed. Subsequently, simulation and experimental methods used for gas adsorption and separation are described. Solutions that integrate the analysis of competitive adsorption on adsorbents and mass transfer phenomena in the column are presented to elucidate the mechanisms of H2/CH4 adsorption and separation in these methods. Finally, modification methods for activated carbon and zeolite adsorbents are summarised. This review should provide a theoretical basis for the design of H2/CH4 separation processes and preparation or modification of adsorbents.