Cu-TDPAT, an rht-type dual-functional metal–organic framework offering significant potential for use in H₂ and natural gas purification processes operating at high pressures

Abstract

The separations of CO₂/CO/CH₄/H₂, CO₂/H₂, CH₄/H₂ and CO₂/CH₄ mixtures at pressures ranging to 7 MPa are important in a variety of contexts, including H₂ production, natural gas purification, and fuel-gas processing. The primary objective of this study is to demonstrate the selective adsorption potential of an rht-type metal–organic framework [Cu₃(TDPAT)(H₂O) ₂]•10H₂O•5DMA (Cu-TDPAT), possessing a high density of both open metal sites and Lewis basic sites. Experimental high pressure pure component isotherm data for CO₂, CO, CH₄ and H₂ are combined with the Ideal Adsorbed Solution Theory (IAST) for estimation of mixture adsorption equilibrium. The separation performance of Cu-TDPAT is compared with four other microporous materials, specifically chosen in order to span a wide range of physicochemical characteristics: MgMOF-74, MIL-101, LTA-5A and NaX. For all mixtures investigated, the capacity of Cu-TDPAT to produce the desired product, H₂ or CH₄, satisfying stringent purity requirements, in a fixed bed operating at pressures exceeding about 4 MPa, is either comparable to, or exceeds, that of other materials.