Effects of Process Parameters on Co₂/H₂ Separation Performance of 3D-Printed Mof-74 Monoliths

Structuring metal-organic frameworks (MOFs) into monolithic contactors by 3D printing has become an increasingly attractive area of research; however, the process performances of these materials have rarely been investigated. In this study, we evaluated the CO ₂ /H ₂ separation performance of a 3D-printed MOF-74 (Ni) monolith at varied adsorption pressure, superficial velocity, feed composition, and adsorption time. This was accomplished using breakthrough and cyclic adsorption-desorption experiments, where the adsorption pressure was varied between 1 and 10 bar, the superficial velocity of 60% H ₂ /40% CO ₂ was varied from 0.44 to 1.80 cm/s, and different CO/CO ₂ /H ₂ feed compositions were introduced. The adsorption time was also varied from 45 to 120 s in the cyclic experiments. The breakthrough experiments indicated that higher pressures enhance the degree of CO ₂ /H ₂ wavefront separation, whereas elevating the superficial velocity leads to broadened breakthrough profiles. Moreover, the multicomponent breakthrough experiments indicated that increasing the CO concentration leads to higher competitive adsorption with CO ₂ and broader wavefronts. Therefore, the breakthrough experiments indicated that the wavefronts become increasingly broadened as the flow rate, pressure, and CO concentration increase. The cyclic adsorption-desorption experiments revealed that increasing the adsorption pressure enhances the CO ₂ /H ₂ separation at the expense of H ₂ productivity, whereas increasing the feed superficial velocity and lengthening the adsorption time give rise to lower H ₂ purity but increased productivity. Optimizing these heuristics revealed that the monolith displayed its best performance with 1.80 cm/s superficial velocity, 10 bar pressure, and 60 s sorption time, where it achieved 98% H ₂ purity and 18 mmol H ₂ /h·g _monolith productivity. Overall, this study provides a thorough assessment of the process parameters that impact the CO ₂ /H ₂ separation performance of 3D-printed MOF-74 (Ni) monoliths which could be applied for future scale-up.