Preparation and morphology study of carbon molecular sieve membrane derived from polyimide

Abstract

Carbon molecular sieve (CMS) membranes were prepared by pyrolysis of polyimide films at three different temperatures (600, 900, and 1100 °C). The physico‐chemical structure and morphology of the derived samples were characterized by a number of techniques. FTIR spectra and SEM/EDX revealed changes in surface chemistry and overall compositions. Raman spectroscopy indicated the co‐existence of ordered graphite and amorphous domains. TEM and XRD suggested that the samples possess a ‘turbostratic’ structure. With the increase of the pyrolytic temperature, the evolution of the microstructure was clearly evidenced. It was observed qualitatively in TEM images and reflected by the d‐spacing. The surface area, pore volume, and size distribution of micropores/small micropores were derived from the standard N2 and CO2 isotherms, respectively, and compared for their roles in determining mesopore, micropore, and small micropores. These surface characteristics were analyzed and compared with the gas adsorption/permeation properties.

Carbon molecular sieve membranes for natural gas purification: Role of surface flow

“…Compared with Kapton polyimide (O: 78.3%; C: 21.7%), the carbon content of the CMSMs increases and oxygen content decreases progressively with an increase in the pyrolysis temperature. Such a change corresponds to the decomposition of the polymer, and it confirms the progressive evolution of graphite‐like structures at higher pyrolysis temperatures …”

“…Figure shows the FTIR (ATR) spectra of the three membrane samples as well as that of the Kapton polyimide precursor. It is seen that the characteristic peaks of polyimide (C═O stretching of imide at 1707 and 1770 cm −1 ; stretching vibration of aromatic rings at 1501 cm −1 ; C─N stretching at 1350 cm −1 , 1100‐1200 cm −1 of aliphatic C─N bond; 720 cm −1 for the deformation of imide ring) virtually diminished on CMSM 700 and 800, though are still largely visible on CMSM 600. On the other hand, the three CMSM membrane samples showed a new peak at 2350 cm −1 , which may be attributed to the C≡C bond vibrations due to the heteroatoms and aromatic C─H out‐of‐plane deformation …”

“…The CMSM was prepared by pyrolysis of the polymer precursor in an inert atmosphere . The Carbolite furnace (Model No.…”

“…While molecular sieving has been the main separation mechanism in most studies, the surface flow was also found to play an important role in the overall separation process. In one of our previous studies, CMSM membranes were produced from Kapton polyimide films with thicknesses of 250 μm that were pyrolyzed at 600°C, 900°C, and 1100°C, respectively. The membranes were characterized and tested for the permeation of pure CO 2 and N 2 gases.…”

Experimental methods in chemical engineering: X‐ray diffraction spectroscopy—XRD

“…Eng . mention XRD to characterize polymers, composite materials, catalysts, membranes, minerals, and medicinal drugs, which makes it one of the most used spectrometries.…”