Regeneration of Alkanolamine Solutions in Membrane Contactor Based on Novel Polynorbornene

For the first time, a novel highly permeable glassy polymer, addition poly[bis(trimethylsilyl)tricyclononene] (PBTMST), was proposed for its use in a gas-liquid membrane contactor for the regeneration of CO2 absorption liquids (desorption of CO2). This membrane material possesses a good chemical stability and high barrier properties for a number of alkanolmines (30 wt% solutions of MEA, DEA, MDEA, AMP, DEAE or AEAE) under typical regeneration conditions (T = 100 degrees C). Studies on gas transport properties of PBTMST (100 degrees C and 1-40 bar) show that permeability coefficients of oxygen, nitrogen and carbon dioxide initially tend to decrease, and then level off after first 6-8 hours of operation. This behavior can be explained by partial relaxation of the free-volume structure of PBTMST, no chemical degradation of polymer material at high temperature was confirmed by IR analysis. At the same time, this membrane material preserves high gas permeability coefficients which are higher than those of conventional materials used in the membrane contactors. Gas-liquid membrane contactor based on dense PBTMST membrane shows a good, stable performance; particularly, CO2 loading in diethanolamine solution (30 wt%) can be reduced for 0.05-0.34 mole/mole by single pass through the membrane desorber at 100 degrees C and elevated pressure. It seems that desorption rate here is mainly controlled by liquid phase because decreasing of membrane thickness by 50% (from 31 to 21 mu m) leads to improvement of DEA regeneration only by 1.5-8.5%.