Exploring the Potentials of Membrane Gas Separation for CO Concentration After Plasma Catalytic CO2 Splitting.

Today, reducing carbon footprints requires the development of technologies to utilize CO2, particularly by converting it into valuable chemical products. One approach is plasma-catalytic CO2 splitting into CO and O2. The task of separating such a ternary mixture is nontrivial and requires the development of an efficient method. In this paper, we have developed a comprehensive scheme for the separation of a CO2/CO/O2 mixture using membrane technology. The novelty of this work lies in the development of a complete scheme for separating the products of plasma-chemical decomposition of CO2 to produce a CO concentrate. The calculations utilized the principle of a reasonable balance between the recovery rate and the energy consumption of the separation process. This scheme allows production of a CO stream with a purity of 99%. To achieve this goal, we have proposed the sequential use of CO2-selective membranes based on polysiloxane with oligoethyleneoxide side groups (M-PEG), followed by polysulfone (PSF) hollow-fiber membranes to separate CO and O2. For these membranes, we measured the CO permeability for the first time and obtained the selectivity for CO2/CO and O2/CO. The potential of membrane separation was demonstrated through a three-stage process, which includes recycling of the CO removal stream and concentration after CO2 plasmolysis. This process was calculated to yield a highly pure CO stream containing 99 mol% with a recovery rate of 47.9-69.4%. The specific energy consumption for the separation process was 30.31-0.83 kWh per 1 m3 of feed mixture, and the required membrane area was between 0.1 m2 for M-PEG and 42.5-107 m2 for PSF, respectively.