(157f) High Performance He Enrichment Membranes Obtained By Directly Fluorination

Helium is considered as a noble resource due to its versatile advantages such as extremely low density, melting point and viscosity behaviors, which makes it in drastic demand in both industrial and academic research. The only resources of He is from natural gas, however, the majority of the natural gas containing the He with the concentration of less than 1% or even 0.1%, how to efficiently recover He from those extremely low concentrated natural gas is a great challenge. Here, we adopted an interesting method by direct fluorination the microporous polymer membranes to achieve both high He permeable and high He/CH4 selective membrane, in which, the fluorinated CMSM for 1 min showed a He permeability of 3432 Barrer and He/CH4 selectivity of 5329. After aging for 120 days, the permeability of He decreased to 2648 Barrer, and the selectivity for He/CH4 reached as much as 7157. When this membrane is used to enrich the He/CH4(1/99) mixed-gas, we can find that even under 20 bar upstream pressure, the He/CH4 selectivity can still reach as much as 4100 with the downstream He concentration of 80%. The barometric sorption results showed that the sharply enhanced He/CH4 selectivity after this direct fluorination is attributed to the improved diffusivity selectivity, which is proposed by the substitution reaction of C-F to C-H that re-shaping the ultra-micropore of the CMSM. This result showed that the direct fluorination technique is a very powerful molecular engineering technique for He enrichment.