Methane purification by adsorptive processes on MIL-53(Al)

Abstract The main polluting compound in natural gas and biogas is CO 2 . Therefore, the removal of CO 2 from these fuels is a major process in the industry for upgrading their energy content. The separation by Pressure Swing Adsorption (PSA) is energy-wise efficient and the porous aluminium terephthalate – MIL-53(Al) MOF has been pointed out as a promising adsorbent to carry out this separation. In this work, MIL-53(Al) tablets (Basolite ® A100) provided by BASF are evaluated to carry out CO 2 /CH 4 separation by adsorption. The adsorption capacity of CO 2 and CH 4 was assessed by dynamic experiments in a fixed-bed reactor, carried out at 303 K and pressures up to 3.5 bar. The evaluated material presents an adsorption capacity of 4.3 mol kg −1 at 3.5 bar for CO 2 . Fixed-bed experiments adsorption and desorption in helium flow revealed high selectivity of MIL-53(Al) material for CO 2 , with a separation factor of 4.1 at 303 K and pressures of 0.1–3.5 bar, thus showing to be promising for a PSA process. The measured single and binary breakthrough curves were simulated with a mathematical model for fixed bed column. Two VSA cycles, both with 4-steps but with different pressurization types were designed to produce 96.5% CH 4 from a 40:60 CO 2 /CH 4 mixture; experimental validation confirms a good model prediction. Two industrial-scale PSA processes were designed and optimized by simulations, a case similar to natural gas upgrade (but lower inlet pressure) and biogas upgrade. The CH 4 recoveries were determined as 92.8% and 72.9%. The productivities were estimated as 2.09 and 2.78 mol kg ads −1  h −1 and the power consumptions as 17.0 and 5.1 W h mol −1 CH 4 . The obtained purity values allow the distribution via pipelines of upgraded CH 4 .