Adsorption-based separation of refrigerant blends using ZIF-7 and ZIF-8: Isothermal high-pressure gravimetric sorption measurements

A high-pressure gravimetric sorption analyzer incorporating a magnetic suspension balance was set up for simultaneous density and sorption measurements in the temperature range of (273.15–368.15) K and pressures up to 15 MPa. The reliability of the apparatus was first examined by density measurements of four pure gases (nitrogen, carbon dioxide, argon, and methane) at temperatures of (283.15–333.15) K with pressures up to 12 MPa. The expanded uncertainties (k = 2) were estimated to be 60 mK for temperature, 0.2 or 3.0 kPa for pressure, and 0.1 % for pure fluid density determination. The density data measured with the newly commissioned apparatus were compared to values calculated with reference equations of state as implemented in the NIST REFPROP database version 10.0, with relative deviations mostly within 0.1 % after calibration. The apparatus was further validated through methane sorption measurements on ZIF-7, showing excellent agreement with data obtained from another well-calibrated gravimetric adsorption analyzer that has been extensively used for accurate measurements. Following this validation, the adsorption of six pure refrigerant gases (R-32, R-125, R-1234yf, R-134a, R-1234ze(E), and R-290) on ZIF-7 and ZIF-8 was studied to explore their potential for refrigerant blend separation (e.g., R-410A and R-513A). The results indicate that ZIF-8 could effectively separate R-32 from R-410A, while ZIF-7 has the potential to separate both R-32 from R-410A and R-1234yf from R-513A.