Highly permeable and selective sepiolite hybrid mixed matrix carbon membranes supported on plate carbon substrates for gas separation

Abstract

The development of promising dopants is essential for fabricating mixed matrix membranes with high gas separation performance. Here, mixed matrix carbon membranes (MMCMs) were produced by using polyimide as precursor and sepiolite as dopants on plate phenolic resin-based carbon supports via the processes of membrane formation and pyrolysis. The thermal stability, surface functional groups, microstructure and morphology of membrane samples were characterized by the thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscope, respectively. The effects of sepiolite amount on the microstructure and property of MMCMs were investigated. Besides, the change tendency of gas permeation with permeation temperature and permeation pressure was further examined. The results showed that the addition of sepiolite enhanced the thermal stability of the precursor membranes and the microstructural compactness of resultant MMCMs. Especially, it greatly improved the gas permeability and selectivity of MMCMs. The maximum separation performance was reached for MMCMs made by the sepiolite content of 0.2%, with the gas permeabilities of 8412.9Barrer (H2), 6711.5Barrer (CO2), 6062.0 Barrer (O2) and 220.9 Barrer (N2), and the selectivities of 38.1 (H2/N2), 30.4 (CO2/N2) and 27.4 (O2/N2). Moreover, the MMCMs can directly concentrate the mole fraction of O2 from compressed air to 93%.