Crosslinking and stabilization of nanoparticle filled poly(1‐trimethylsilyl‐1‐propyne) nanocomposite membranes for gas separations

Abstract

Poly(1-trimethylsilyl-1-propyne) (PTMSP) has been crosslinked using 4,4 0 -diazidobenzophenone bisazide to improve its chemical and physical stability over time. Crosslinking PTMSP renders it insoluble in good solvents for the uncrosslinked polymer. Gas permeability and fractional free volume decreased as crosslinker content increased, while gas sorption was unaffected by crosslinking. Therefore, the reduction in permeability upon crosslinking PTMSP was due to decrease in diffusion coefficient. Compared with the pure PTMSP membrane, the permeability of the crosslinked membrane is initially reduced for all gases tested due to the crosslinking. By adding nanoparticles (fumed silica, titanium dioxide), the permeability is again increased; permeability reductions due to crosslinking could be offset by adding nanoparticles to the membranes. Increased selectivity is documented for the gas pairs O 2 /N 2 , H 2 /N 2 , CO 2 /N 2 , CO 2 /CH 4 , and H 2 /CH 4 using crosslinking and addition of nanoparticles. Crosslinking is successful in maintaining the permeability and selectivity of PTMSP membranes and PTMSP/filler nanocomposites over time.

Selective, Room-Temperature Transformation of Methane to C1 Oxygenates by Deep UV Photolysis over Zeolites

“…O 2 permeability decreases from 10,083˘936 Barrer at 298 K to 7024˘1050 Barrer at 333 K, while O 2 diffusivity diminishes from 5.47ˆ10´8˘1.36ˆ10´8 cm 2¨s´1 at 298 K to 3.46ˆ10´8˘7.72ˆ10´9 cm 2¨s´1 at 333 K. These values are in good agreement with those reported in the literature [17,[22][23][24][25]32,33]. However, in spite of the high oxygen permeability, the ideal O 2 /N 2 selectivity of pure PTMSP is very low, ranging from 1.32˘0.12 at 298 K to 0.94˘0.41 at 333 K. This is a characteristic behavior of PTMSP due to its high free volume and the fact that the weakly and rigid molecular sieving framework is more prone to changes in solubility than diffusivity [24,32].…”

Mixed Matrix Membranes for O2/N2 Separation: The Influence of Temperature

“…O 2 permeability decreases from 10,083 ± 936 Barrer at 298 K to 7024 ± 1050 Barrer at 333 K, while O 2 diffusivity diminishes from 5.47 × 10 −8 ± 1.36 × 10 −8 cm 2 ·s −1 at 298 K to 3.46 × 10 −8 ± 7.72 × 10 −9 cm 2 ·s −1 at 333 K. These values are in good agreement with those reported in the literature [17,22,23,24,25,32,33]. However, in spite of the high oxygen permeability, the ideal O 2 /N 2 selectivity of pure PTMSP is very low, ranging from 1.32 ± 0.12 at 298 K to 0.94 ± 0.41 at 333 K. This is a characteristic behavior of PTMSP due to its high free volume and the fact that the weakly and rigid molecular sieving framework is more prone to changes in solubility than diffusivity [24,32].…”

“…The MMMs that showed the best separation ability were the 5 wt % CHA-PTMSP, the 5 wt % LTA5-PTMSP, the 5 wt % Rho-PTMSP, and the 20 wt % LTA1-PTMSP, with a slight decrease in permeability but a considerable enhancement in selectivity, surpassing the Robeson’s upper bound, even increasing the temperature up to 333 K. The O 2 permeability of PTMSP reported in the literature covers a range between 6000 and 10,000 Barrer at 308 K, decreasing with temperature. However, its high permeability is accompanied with a very low O 2 /N 2 selectivity, with values between 1.30 and 1.70 at 308 K [22,23,24,25]. Consequently, the incorporation of suitable chosen inorganic fillers is likely to improve the selectivity of a defect-free membrane [17,26,27,28,29].…”

Effects of aging on poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet radiation for gas separation

“…Various modification technologies have been used extensively in the materials industry. Physical blending, graft or random copolymerization, composite membrane synthesis, and surface modification have been used to improve the gas‐separation performance of these membranes …”