Model Based Analysis of Plasticization Behaviour of Polymeric Membranes Used for High Pressure CO2 Separation in Natural Gas Processing

Plasticization resistant property is very important in measuring the performance of polymer membranes for high pressure CO₂ separation from natural gas or separation in aggressive environment. Many polymeric membranes have been synthesized and tested for high pressure CO₂ separation. A quick qualitative comparison is often necessary in the early phases of membrane gas separator design to facilitate material selection. In this paper, a procedure that integrates experimental and mathematical model was developed to determine the plasticization pressure from permeability measurement data. It was demonstrated that the plasticization behaviour of the current generation of polymer membranes can be successfully described by a quadratic (2^nd order) empirical equation. A theoretical justification was then proposed to support this model.  The model was tested on more than ninety polymer membrane samples and results correlate well with experimental results that have been reported in the literature. Three model parameters (a₁, a₂ and a₃ ) were obtained. Their values range from 0.0001 to 2.9175, -62.083 to -0.0055 and 0.7862 to 786.62 respectively. Values of these parameters were observed to be an indication of the extent of their resistance to penetrant-induced plasticization and performance stability in aggressive feed streams. For example lower values of  a₁revealed a relatively higher plasticization pressure and consequently better stability.

Samples application of the model is considered and recommendations for their use to design polymer membranes and evaluation of their performance under a penetrant induced plasticization environment are provided. The results of analysis from the model provide consistent set of parameters that can be included in simulation software for modeling and optimization of membrane gas separation involving aggressive feed streams.