Fabrication and gas permeation of CMS/C composite membranes based on polyimide and phenolic resin

Abstract

Supported carbon molecular sieving membranes were prepared by a novel precursor 6FAPB-CBDA type polyimide on the surface of carbon sheets, which have a most promising potential for gas separation applications.

Process Intensification of the Hydrogen Production Reaction Using a Carbon Membrane Reactor: Kinetics Analysis

“…The gas permeability (H 2 , CO 2 , and N 2 ) and selectivity (H 2 /N 2 and CO 2 /N 2 ) of the carbon membranes decrease dramatically with the increase of the pyrolysis temperature from 650 to 850 °C. During pyrolysis, the microstructure of the carbon membranes undergoes two significant pyrolysis processes: thermal degradation and thermal polycondensation . At a lower pyrolysis temperature (below 650 °C), the pyrolysis is dominated mainly by the first process for a polyimide‐generating porous structure.…”

“…The coating was performed by spin‐coating the PAA solution on a compressed plate phenolic resin disc supports at a spinning rate of 900 r min − for 30 s, coating six times, and drying at ambient temperature for 5 days. The detailed procedures of coating and support formation have been reported previously …”

“…During pyrolysis, the microstructure of the carbon membranesu ndergoes two significant pyrolysis processes:t hermal degradation and thermal polycondensation. [40] At al ower pyrolysis temperature( below 650 8C), the pyrolysis is dominated mainly by the first process for ap olyimide-generating porous structure.I ft he pyrolysis temperaturei sg reater than 650 8C, the microstructure would become more compacta nd pyrolysis progresses because of the takeover of thermal rearrangement and polycondensation reactionsi nt he carbon matrix. [40,41] However, this is as tep-by-step process as the microstructural evolutiono fc arbon membranes would slowd own as the pyrolysist emperature increases,e specially in the high-temperature range (750-850 8C), which results in ar eduction of gas permeability to be less clear than that in the low-temperature range (650-750 8C).…”

“…Thep reparation of carbon membranes comprises two major steps:c oating and pyrolysis.T he coating was performed by spincoating the PA As olution on ac ompressed plate phenolic resin disc supports at as pinning rate of 900 rmin À for 30 s, coating six times,a nd drying at ambient temperature for 5days.T he detailed procedures of coating and support formation have been reported previously. [40] After coating,t he pyrolysis of the membranes was undertaken in at ubular furnace.T he membranes were first heated at ar ate of 2 8Cmin À1 from RT to 400 8Ca nd held at this temperature for 3h,t hen elevated to the final pyrolysis temperature (650, 750, or 850 8C) at ar ate of 1 8Cmin À1 and held at this temperature for 60 min. Throughout the pyrolysis,a ni nert atmosphere was maintained by purging the furnace with highly purified N 2 gas of 200 mL min À1 .E ventually,s upported carbon membranes with ad iameter of 2cma nd an overall thickness of 0.5 cm were collected after cooling to RT.T he membranes were denoted as CM-T,inw hich T represents the pyrolysis temperature [8C].…”

Uniformity control and ultra‐micropore development of tubular carbon membrane for light gas separation

“…The dip‐coating method is widely used to synthesize tubular‐type membranes and hollow fiber‐type membranes as it is economical and easy for industrial applications, 33‐35 as compared to other methods, such as spin‐coating, 35,36 spray‐coating, 37,38 drop‐coating, 39 ultrasonic deposition, 40 and chemical vapor deposition 41‐43 . However, the dip‐coating process involves dynamic changes in dope concentration, viscosity gradient, and surface tension due to solvent evaporation and gravity, thus influencing the final structure of the supported membranes 44‐47 .…”