Poly(1-trimethylsilyl-1-propyne) of cis-Enrich Configuration as a Membrane Material for the Separation of Butane/Methane Mixtures as Natural Gas Components

The permeability of individual lower hydrocarbons and in a С₁/С₄ mixture is studied for the first time for films based on PTMSP of the new cis-enrich configurational composition (the content of cis-units in the samples is 80 and 90%). The methane permeability of freshly prepared cis-regular PTMSP films (90% cis-units) and exposed to air for a month is higher than the corresponding values of PTMSP films containing 80% cis-units. The X-ray diffraction data indicate a looser packing of cis-regular PTMSP. The introduction of antioxidant Irganox 1076 into the PTMSP films leads to a decrease in the initial level of methane flux. At the same time, the permeability of the films with the added Irganox decreases much more slowly over time (for a month) compared with the films without the added antioxidant. The permeability of individual lower hydrocarbons through PTMSP films without and with the added Irganox 1076 increases in the sequence С₁ < C₂ < C₃ < C₄. The value of the separation factor in the n-butane/methane mixture attains 33, which is almost 7 times higher than selectivity for individual components. A high level of n-butane permeability for cis-enrich PTMSP is maintained at least for a month of film storage in air.