A polymeric membrane is widely studied for gas separation. In CO2 separation, membrane process has a great advantage due to its simplicity in installation and operation. However, one major setback is the presence of minor gases. In pre-combustion carbon capture, H2 is obtained as a byproduct, while syngas also contains various minor gases such as H2S. The effect of minor gas has been reported by a number of research. Nevertheless, a fundamental investigation for the interaction between them has not been thoroughly studied. This study will focus on the investigation of interaction between minor gases and a popular polymeric membrane. In this study, PEBAX 2533 membrane is mainly tested for permeability of CO2 and structural change. PEBAX 1657 and PDMS membranes are compared to evaluate the impact on different molecular structure. CO2 are used as a feed with trace amount of H2S (5-100ppm). H2 and N2 are added for further evaluation. Permeability test is conducted by various gas mixtures and temperature (15-70C). Every test is triplicated and measured at steady state. Gas composition is controlled using mass flow controller and GC. Surface analysis tools, such as AFM, FT-IR, XRF, and XPS, are used to analyze the membrane surface before and after the permeability test. At low concentration of H2S (less than 10ppm), the CO2 permeability increases, whereas high concentration of H2S causes decreased permeability. More H2S added, higher activation energy of CO2 permeation is observed. On the surface of the membrane which has less than 100 µm thickness, there is no sign of sulfur. However, qualitative analysis using XRF which requires a membrane thicker than 200µm shows the presence of sulfur. Therefore, the length of gas permeation path might affect the accumulation of sulfur on the membrane. In XPS analysis, bond energy of C-O bond shows notable change after 12 hours of CO2 permeation inferring that C-O bond might have changed. However, with 100ppm H2S, the change in bond energy is lessened compared to pure CO2 result, possibly due to the competitive permeation.

Fundamental study of interaction between minor gases and a polymeric membrane for carbon dioxide transport

2019 Spring National Meeting

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