Efficient Facilitated Transport Polymer Membrane for CO₂/CH₄ Separation from Oilfield Associated Gas

CO₂ enhanced oil recovery (CO₂-EOR) technology is a competitive strategy to improve oil field economic returns and reduce greenhouse gas emissions. However, the arbitrary emissions or combustion of the associated gas, which mainly consists of CO₂ and CH₄, will cause the aggravation of the greenhouse effect and a huge waste of resources. In this paper, the high-performance facilitated transport multilayer composite membrane for CO₂/CH₄ separation was prepared by individually adjusting the membrane structure of each layer. The effect of test conditions on the CO₂/CH₄ separation performance was systematically investigated. The membrane exhibits high CO₂ permeance of 3.451 × 10^-7 mol·m^-2·s^-1·Pa^-1 and CO₂/CH₄ selectivity of 62 at 298 K and 0.15 MPa feed gas pressure. The cost analysis was investigated by simulating the two-stage system. When the recovery rate and purity of CH₄ are 98%, the minimum specific cost of separating CO₂/CH₄ (45/55 vol%) can be reduced to 0.046 $·Nm^-3 CH₄. The excellent short-to-mid-term stability indicates the great potential of large industrial application in the CH₄ recovery and CO₂ reinjection from oilfield associated gas.