Abstract
The polycrystalline CHA-type zeolite layer with Si/Al = 18 was formed on the porous α-Al2O3 tube in this study, and the gas permeation properties were determined using single-component H2, CO2, N2, CH4, n-C4H10, and SF6 at 303–473 K. The membrane showed permeation behavior, wherein the permeance reduced with the molecular size, attributed to the effect of molecular sieving. The separation performances were also determined using the equimolar mixtures of N2–SF6, CO2–N2, and CO2–CH4. As a result, the N2/SF6 and CO2/CH4 selectivities were as high as 710 and 240, respectively. However, the CO2/N2 selectivity was only 25. These results propose that the high-silica CHA-type zeolite membrane is suitable for the separation of CO2 from CH4 by the effect of molecular sieving.
Highlights
Zeolites are microporous aluminosilicate compounds, and they have been attracted much attention as the potential material for membranes
Zeolite membranes have been studied since the 1990s, and the MFI-type zeolite membranes were formed on the substrates by deposition and intergrowth of crystallites, which were nucleated in synthesis mixtures [1,2,3,4,5,6,7,8,9,10]
The CO2 permeance and selectivity of our membrane were relatively high for CO2–CH4 mixtures, and the performances could be plotted on the trade-off line of SAPO-34, CHA, and AEI-type zeolite membranes [27,28,32,33,34]
Summary
Zeolites are microporous aluminosilicate compounds, and they have been attracted much attention as the potential material for membranes. Some kinds of zeolite membranes are available for the dehydration of many kinds of organic solvents in industries [18,19,20,21,22] These mechanism studies have established that DDR-, CHA-, and AEI-type zeolite has favorable characteristics for the membrane material, such as small micropore diameter, large micropore volume, and the composition variability [23]. These features correspond to the permeation and separation performances and the acid and thermal stabilities of the membrane [24]. The gas permeation and separation mechanisms of the CHA-type zeolite membrane were discussed in this paper
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