Abstract
Separation of low boiling gas mixtures is widely concerned in process industries. Now their separations heavily rely upon energy-intensive cryogenic processes. Here, we report a pseudo-absorption process for separating low boiling gas mixtures near normal temperature. In this process, absorption-membrane-adsorption is integrated by suspending suitable porous ZIF material in suitable solvent and forming selectively permeable liquid membrane around ZIF particles. Green solvents like water and glycol were used to form ZIF-8 slurry and tune the permeability of liquid membrane surrounding ZIF-8 particles. We found glycol molecules form tighter membrane while water molecules form looser membrane because of the hydrophobicity of ZIF-8. When using mixing solvents composed of glycol and water, the permeability of liquid membrane becomes tunable. It is shown that ZIF-8/water slurry always manifests remarkable higher separation selectivity than solid ZIF-8 and it could be tuned to further enhance the capture of light hydrocarbons by adding suitable quantity of glycol to water. Because of its lower viscosity and higher sorption/desorption rate, tunable ZIF-8/water-glycol slurry could be readily used as liquid absorbent to separate different kinds of low boiling gas mixtures by applying a multistage separation process in one traditional absorption tower, especially for the capture of light hydrocarbons.
Highlights
The enthusiasm of the scientific community about metal-organic frameworks (MOFs) and other nano-porous materials as solid-adsorbents, does not yet resonate in the process engineering community[2,32,33]
In this work we demonstrate that the key factor affecting the separation selectivity of absorption-adsorption hybrid method is the penetration selectivity of liquid membrane formed by solvent molecules around the ZIF-8 particles for different gas species
By comparing them with the isotherms on pure solid ZIF-8 (Supplementary Fig. S1), we see that most gas species become more difficult to enter the pores of ZIF-8 suspended in glycol
Summary
The enthusiasm of the scientific community about MOFs and other nano-porous materials as solid-adsorbents, does not yet resonate in the process engineering community[2,32,33]. The most remarkable advantage of distillation is multistage separations can be realized in a single equipment and very high purities of products could be achieved In these points, pressure-swing adsorption (PSA) is uncompetitive. Green solvents like water and glycol were used to adjust the penetration selectivity of liquid membrane aiming at enhancing the separation selectivity of ZIF-8 slurry for different kinds of low boiling gas mixtures. By this way, ZIF-8/water-glycol slurry could be tuned to integrate absorption, membrane, and adsorption into a pseudo-absorption process with enhanced separation efficiency over single absorption, membrane or adsorption process and applied in traditional multistage separation process like distillation for separating low boiling gas mixtures near normal temperature
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call