Robust high-permeance PTMSP composite membranes for CO2 membrane gas desorption at elevated temperatures and pressures

Abstract

This work covers the development of robust and stable in time poly[1-(trimethylsilyl)-1-propyne] (PTMSP) thin film composite (TFC) membranes with high CO2 permeance for its application in high pressure/temperature gas–liquid membrane contactors used for amine-based solvents regeneration. For the first time, a novel technique of two-layers coating was proposed and successfully implemented to apply thin top-layer on microfiltration support by adjusting PTMSP solubility in organic solvents. By using different catalytic systems such as NbCl5 and TaCl5/TIBA, it was possible to synthesize two polymer samples (“PTMSP-Nb” and “PTMSP-Ta”), which are insoluble and soluble in hexane, respectively. The first intermediate layer made of “PTMSP-Nb” was cast on the microfiltration porous support from a toluene solution in order to form a PTMSP-coated porous support. The solution of “PTMSP-Ta” in n-hexane was used for subsequent formation of a thin defect-free selective layer (second layer). By using two commercial polymeric (MFFK-1) and metal-ceramic (MC) supports with high surface porosity of 85% and 60%, respectively, it was possible to fabricate the tailor-made TFC membranes “PTMSP/MFFK” (top-layer – 0.5µm) and “PTMSP/MC” (top-layer – 1.2µm) with an initial CO2 permeance of 50 and 36.3m3(STP)/(m2hbar), respectively, and CO2/N2 selectivity of 3.5. A preliminary conditioning of the PTMSP/MC membrane at 100°C for 100h in air was applied for the accelerated relaxation of PTMSP top layer. The resulting robust PTMSP/MC TFC membranes still provided a high CO2 permeance of 1.6m3(STP)/(m2hbar) (~600GPU) without a noticeable decline of membrane performance within the long-term gas permeation testing (at least 250h) at 100°C. The PTMSP/MC membranes were further successfully utilized in HPT MGD for regeneration of 50wt% methyldiethanolamine (MDEA) at elevated temperature (100°C) and pressures (up to 30bar). A stable TFC membrane performance was demonstrated and no solvent leakage through the membranes was observed.