Improved Polymer Membranes for Sour Gas Filtration and Separation

Abstract

Abstract This paper contributes to the interest of natural gas industry. It is well known that a scientist continually faces challenge to purify the natural gas (NG) from impurities such as acid gases (CO2 and H2S). The polymer membrane based gas separation has materialized as a promising field of research. There is a need for stiff backboned polymer membranes that can withstand potential membrane swelling and degradation for a cost effective use of the material and the technology. The polymer used is thermoplastic elastomers poly(ether-b-amide); popularly known as PEBAX (P) that holds a number of properties that makes it potentially useful membrane materials. Room temperature ionic liquids with high selectivity towards acid gas were selected. The careful selection of cations includes 1-Butyl-3-methylimidazolium and 1-(2-etoxy-ethyl)-3-methylimidazolium whereas anions were selected from BF4, PF6. Subsequent supported ionic liquid membrane systems (SILMs) and SILM-nanocomposites were successfully prepared by incorporating nanofiller. The morphology, structure, and stability of these membrane materials were characterized by various techniques. The polymer has rigid polyamide segments which are spaced with malleable polyether segments. The amide segment delivers the mechanical strength, while the soft ether block contributes to the gas transport capabilities. Polymer SILM allows the freedom to effectively tune the structure-property relationship of polymer and ionic liquid in membranes towards its permeability and selectivity of sour gases. Our research discusses the effect of the incorporation of selective ionic liquids to polymer membranes. In particular, we focus on the structure-property relationship of the polymer and room temperature ionic liquids on the gas separation. The modulus values decreases on addition of ionic liquid. The flexible polyether phase of the polymer gets plasticized by ionic liquid and thereby the elongation also gets reduced. This polymer's backbone was further strengthened by successfully employing either of two strategies such as molecular chain extension/crosslinking or a bulk modification using nanofiller which can impart enhanced mechanical properties as given in figure 1a.