SORPTION OF SO2 – N2 GAS MIXTURES IN PIM-1
Recently, several published studies on the gas and vapour mixture sorption in glassy polymers revealed the sorption competitiveness and plasticisation 1-3 as governing phenomena. Moreover, the studied systems qualitatively followed the Dual Mode Sorption model for gas mixtures 4. However, they frequently focus on concentrated binary mixtures (e.g. CO2 – CH4) containing tens of per cent of the diluted components, and thus do not correspond to the conditions in industrial applications in which traces of sour gases are to be removed. In this study, we report on the sorption of SO2 – N2 gas mixtures at high dilutions of SO2, which model the composition of the sour flue gas.
Sorption of SO2 – N2 gas mixtures in PIM-1 was studied at 25, 35 and 45 °C, 1 to 9 bar within 1000 to 3000 ppm SO2 using a barometric (pressure-decay) system. Under such conditions, the sorption mass uptakes of the individual components were comparable, while the SO2/N2 sorption selectivity ranged from 180 to 1300, depending mainly on the SO2 concentration in the gas phase. Interestingly, a competitive sorption character was not observed – the uptakes of N2 from the mixtures were comparable to those from the pure N2 gas. In other words, sorption of the SO2 – N2 gas mixtures in PIM-1 showed principally different isotherms than predicted using the Dual Mode Sorption model for gas mixtures. It can thus be hypothesised that the two sorptives do not essentially compete for the same sorption sites in bulk PIM-1 at high SO2 dilutions.