Partially Carbonized Polyimide Membranes with High Permeability for Air Separation.

Abstract

Partially carbonized polyimide (CPI) membranes were prepared from a solution of 30 wt% polyamic acid in N,N-dimethylacetamide. The polymer membranes formed on an alumina support were thermally treated, involving imidization in air at 180°C and carbonization in N 2 at relatively low temperature (400-500°C). The cross-sectional views of the supported CPI membranes show that the membranes consist of a top layer (thickness, 10 µ µ µ µ µm) on the support and a CPI/alumina thin layer in the support. The CPI membranes carbonized at 500°C showed high permeability for O 2 of 1000-30000 barrer and permselectivity for O 2 /N 2 of 3-6. The permeability of the CPI membranes was much higher than that of the reported polymer membranes and the carbon membranes. The pores formed under carbonization at 500°C and 400°C were effective for separating O 2 /N 2 and CO 2 /CH 4 mixtures, respectively. TG analysis indicated that the carbonization proceeds even at a constant temperature of 500°C. The successive generation of flexible pores before the formation of graphite structure with rigid pores seems to contribute to the higher permeability of the CPI membranes.

Porous Inorganic Membranes for CO2 Capture: Present and Prospects

“…poly(ether imide)/HSSZ-13,62 and polyimide/carbon,63 ) due to a low symbiosis between the solid nanoparticles and the polymer matrix. Even if the field of MMMs has experienced a sustained development in the past years, this is still less active than the field of polymer membranes, with about 90 and 175 published papers covering, respectively, H 2 and CO 2 separations.…”

Preparation and Gas Permeation Properties of Composite Carbon Molecular Sieve Membranes Derived from Polyimides with Thermally Decomposable Sulfonic Acid Salt and/or Hexafluoroisopropylidene Group

“…This suggests the decomposition of sulfonic acid groups followed by the decomposition of -C(CF 3 ) 2 -groups just before the substantial decomposition of the polyimide backbone significantly enhanced the micropore structure of the resultant pyrolytic layer. Figure 6 shows the comparison of the gas separation performance for the present CMS membranes with that for the CMS membranes reported in the literature (Hayashi et al, 1995;Kusuki et al, 1997;Shiflett and Foley, 1999;Okamoto et al, 1999Okamoto et al, , 2000Fuertes, 1999, 2000;Nishiyama et al, 2003;Yoshino et al, 2003;Zhou et al, 2003). There seems to be a trade-off relationship between the gas selectivity and permeance for every separation system.…”

“…Each solid line in Figure 6 is the upper bound line indicating the upper limit of the separation performance for each separation system of CMS membranes developed up to now. Recently, there have been reported CMS composite membranes displaying extremely high gas permeance (Nishiyama et al, 2003). The permeance and ideal separation factor only for the O 2 /N 2 separation system could be read numerically from a figure of the article, as plotted in Figure 6(a).…”

“…There are many articles reporting CMS membranes derived from various precursors (Hayashi et al, 1995;Kusuki et al, 1997;Shiflett and Foley, 1999;Fuertes, 1999, 2000;Okamoto et al, 1999Okamoto et al, , 2000Nishiyama et al, 2003;Yoshino et al, 2003;Zhou et al, 2003). We have reported that flat pyrolytic membranes prepared by pyrolyzing 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA)-based polyimides with pendant sulfonic acid groups at 723 K displayed higher performance for CO 2 /N 2 and C 3 H 6 /C 3 H 8 separation systems (Islam et al, 2005).…”

A review of oxygen removal from oxygen-bearing coal-mine methane

“…The process enables the nitrogen content of the gas to be substantially reduced, without requiring the membranes to be operated at very low temperatures. In the other studies, the researchers reported that partially carbonized polyimide (CPI) membranes carbonized at 500°C showed high permeability for O 2 , about 1000-30,000 barrer, but the permselectivity for O 2 /N 2 was only 3-6 (Momose et al 2004;Nishiyama et al 2003). Wang et al (2012) studied the separation and purification to oxygen CMM under constant temperature with a hollow fiber membrane separator.…”