Enhanced Methane Purification from Biogas by Industrial PSA Utilizing a Pebax-Supported ZIF-67 Nanosheet Composite

Biogas is a renewable and environmentally friendly energy source with a strong potential to replace fossil-derived natural gas. However, it must be upgraded to methane purities of >95% to meet fuel-quality standards. This study reports, for the first time, the application of a Pebax-supported ZIF-67 nanosheet composite as a structured adsorbent for biogas upgrading via a pressure swing adsorption (PSA) process combined with response surface methodology (RSM) optimization under industrially strict conditions. The composite adsorbent was synthesized and characterized using HR FE-SEM, FTIR, X-ray diffraction, and N₂ adsorption–desorption analyses. Breakthrough experiments with CO₂ and CH₄ were conducted to evaluate adsorption selectivity and were used to validate a dynamic PSA model developed in Aspen Adsorption. A systemic parametric study examined the effects of length-to-diameter (L/D) ratio, operating pressure, and adsorption time on the separation performance for a biogas feed of 500 m³ STP h^–1 containing 40% CO₂ and 60% CH₄. RSM analysis revealed strong interactions among these parameters and enabled the identification of optimal operating conditions. The optimal conditions were an L/D ratio of 5.1, an adsorption pressure of 7.8 bara, and an adsorption time of 62 s. Under these conditions, the PSA cycle achieved a biomethane purity of 98.67% with a recovery of 91.20%, exceeding the minimum pipeline specification of 95% CH₄, with a compression energy requirement of 8.674 kJ mol^–1 (75% efficiency). These results establish the fundamental feasibility and process-level advantages of the Pebax-supported ZIF-67 nanosheet composite for high-performance biogas upgrading, providing a new pathway for integrating anisotropic MOF-based composites into industrial PSA systems.