Separation behavior of amorphous amino-modified silica nanoparticle/polyimide mixed matrix membranes for gas separation

In this work, amorphous amino-modified silica nanoparticles (AAMSN) were successfully synthesized via the sol-gel method and combined with the polyimide (PI) 4,4'-oxydiphthalic anhydride-2,2'-bis(trifluoromethyl) benzidine (ODPA-TFMB) to prepare mixed matrix membranes (MMMs) for gas separation. The physicochemical properties of the AAMSNs were characterized by thermogravimetric analysis, X-ray diffraction, FTIR spectroscopy, and scanning electron microscopy, and the CO2 capture and O-2 enrichment behaviors of MMMs with different AAMSN contents were compared with those of a control PI membrane. The sorption isotherm and permeation data revealed that addition of AAMSNs not only increases the diffusion coefficient of the resulting membranes but also increases their adsorption coefficient due to the amorphous characteristics of the nanoparticles and good adhesion between these particles and the PI. The CO2 permeation properties and CO2/N-2 selectivity of the MMM with 20 wt% AAMSN were 210.1 barrer and 30.8, respectively, while those of the control membrane were 66.7 barrer and 27.8, respectively. Mixed gas permeation results also showed that the gas permeability of the MMMs improves and their gas selectivity is maintained compared with those of the control PI membrane. The unique structure of the AAMSN/PI membrane makes it an attractive candidate for CO2 capture and O-2 enrichment applications.