Abstract: 

“Novel carbon molecular sieve membranes (CMSM) were produced from an ionic liquid-regenerated cellulose precursor in a single carbonization step. The so-called ionic liquid process allows the tailoring of the precursor films with carbonization conditions needed for producing a selective CMSM, which does not block when humid gas streams are used (ca. 80 % relative humidity). As a result, CMSM with extraordinary separation performances, mechanical resistance and stability can be prepared. The present membranes are stable and have a great potential for gas separation. Hence, they might be considered in relevant industrial applications such as separation of nitrogen from air, air dehumidification and separation of hydrogen from syngas.

Background: 

CMSM are a very promising technology for gas separation, exhibiting simultaneously high permeabilities and selectivities. However, all reported and disclosed CMSM suffer pore blockage in the presence of water vapour, normally above 30 % of relative humidity (RH), and display oxygen chemisorption that severely impairs the performance of the membranes.

Competing technologies for gas separations are polymer membranes, adsorption based processes, cryogenic distillation and gas absorption, with their known drawbacks and high costs.

Benefits: 

These membranes show no pore blockage in presence of humidified gas mixtures (up to ca. 80 % RH). Previous state of the art show no pore blockage only for RH up to ca. 30 %. They present extraordinary separation performances, mechanical resistance and stability.

With regard to their production, by tailoring the precursor material it is possible to control CMSM properties and increase their performance for a given gas separation. In addition, CMSM are prepared in a single step which decreases considerable the cost of production if compared with other solutions.

Potential comercial use/applications: 

This is a breakthrough technology that promises to replace most of the polymer membrane modules for gas separation. Furthermore these membranes have the potential to be applied: in the natural gas business for efficiently removing CO2 from the natural gas coming out the wells; in the hydrogen economy new era by recovering quite efficiently hydrogen from natural gas; in the fossil fuel business by removing CO2 from flue gas, facilitating the CO2 sequestration; in the petrochemical industry for oleffin/paraphin separations; in special gas separations, for recovering xenon and helium from gas mixtures and for performing very efficiently the oxygen/nitrogen gas separation.