Preparation and Application of Mixed Matrix Carbon Molecular Sieve Membrane Based on a Phenol Formaldehyde Novolac Resin

Abstract: Carbon molecular sieve membrane (CMSM), a new kind of inorganic membrane, has many excellent performances. Currently, in order to obtain the gas separation materials containning the excellent comprehensive performances, researchers mostly focus on developing the novel materials of membrane separation.In this paper, CMSM was prepared from PFNR by organic-inorganic hybrid materials, polymer blending and KOH activation to enhance the comprehensive performances of CMSM. The porous structures and the gas permeation properties of CMSM were systematically investigated through nitrogen adsorption, FTIR, XRD, SEM and gas permeation measurement etc. The CMSMs prepared were used to separate hydrogen from the coke gas and design the carbon membrane reactor for methanol steam reforming to produce hydrogen.Firstly, the PFNR was cured partly and ground followed by mixing into dough with additives and water. The dough was then extruded to form a green membrane support tube. CMSM was prepared by dip coating on the green membrane support tube with in a PFNR ethanol solution containing carbon molecular sieve (CMS). The top layer of CMSM is very smooth being almost defect-free and the homogeneous distribution of CMS. XRD and nitrogen adsorption isotherms were employed to characterize the carbon structures of CMSM obtained by coating solution of 50wt.% PFNR and 50wt.% PFNR+CMS. The results indicated that CMS in the coating solution can effectively improve the filming condition. The material has rigid aromatic graphitic planes with more ordered and better packed structure. The CMSM shows an increase in interlayer spacing due to the addition of CMS in the coating solution. Through the gas permeation measurement, the results indicated that the CMSM shows high selectivity for separation of gases like O_2/N_2 and H2/CH4 system from pure gas permeation experiments. The addition of CMS redounds to the permeation of O_2 and reduction of defect in the carbon membrane and the performances of enriching oxygen are head and shoulders above the Robeson’s Upper Bound and locate in the commercially available region at the same time. Therefore, CMSM is provided with best advantage and the application foreground.Secondly, a method of polymer blending was employed to control the microporous structure of CMSM. The characteristics of the carbon structures and the gas permeation properties of the CMSM were investigated in terms of the different weight ratio in a PFN…
Key words: Phenol formaldehyde novolac resin; Mixed matrix; PEG; Carbon molecular sieve membrane; Carbon membrane reactor; Methanol steam reforming

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