Mixed-gas permeation of syngas components in poly(dimethylsiloxane) and poly(1-trimethylsilyl-1-propyne) at elevated temperatures

The permeability of poly(dimethylsiloxane) (PDMS) and poly(1-trimethylsilyl-1-propyne) (PTMSP) to a simulated syngas feed containing H2, CO, CO2, and H2S was determined as a function of temperature up to 240°C (464°F). The permeation properties of rarely studied CO and H2S were found to be consistent with their molecular properties (i.e. critical temperature) in both rubbery PDMS and high free volume, glassy PTMSP. At room temperature, PDMS and PTMSP are more permeable to the more condensable gases CO2 and H2S than to H2. However, both polymers become hydrogen selective at elevated temperatures. Activation energies of permeation are highest for H2 in both polymers and decrease regularly with increasing gas condensability. PTMSP exhibits evidence of accelerated physical aging at high temperature.