Preperation And Performance Of The Hybrid Functional Carbon Membranes With High CO₂ Permeaselecticity

As a major greenhouse gas, CO2 has increasingly serious threaten to human production and life with producing a "greenhouse effect". How to reduce carbon dioxide emissions and their separation, recovery, purification, has become a common concern of mankind. Carbon membrane is developed rapidly in recent decades as a new type of porous carbon-based membrane material, which can separate gases with similar diameters with "molecular sieving" mechanism and shows high gas permeability and selectivity. Although the seperation of CO2 can be achieved from CO2/CH4, CO2/N2 systems, the permeability of carbon membranes prepared for CO2 still relatively small and difficult to meet industrial application requirements. Therefore, how to increase the permeability of CO2 and maintain a ralative high selectivity is a critical factor to prepare a high-performance carbon membrane for separation of CO2.In this paper, functional carbon membranes for CO2 separation were designed and prepared by incorporating titanium silicalite nanoparticles, nano-toner and carbon nanotube into polyimide, which is used as the precursor of carbon membrane in this work, respectively. The characterizations of the as-synthesized membranes were studied by XRD, TEM, and FTIRand TG. The effects of doping agents and amount, permeating temperature and pyrolytic temperature on the gas permeation of functional carbon membranes were mainly investigated by gas permeation GC coupling technique.Gas permeation test results show the permeability of functional carbon membranes incorperating with TS-1 is improved a lot compared to pure carbon membrane, especially to absorbing gas such as CO2 whose permeability is enhanced by nearly 30 times at most. The permeabilities of membranes dopped with 20.wt% TS-1 and carbonized at 600℃for pure gas CO2,H2,O2,N2,CH4 are 9087,8111,2017,426 and 357 Barrer(1 Barrer=10-10 cm3(STP)·cm·cm-2·s-1·cmHg-1), respectively. The permeability of CO2(0.33 nm) exceeds that of H2 whose molecular diameter is about 0.289nm.With the increase of the dopant amount, gas permeability of the prepared membranes increases. Results also indicate the permeability of prepaerd membranes is affected significantly by the pyrolysis temperature. When the temperature is above 700℃, the gas permeability exhibites a drastic drop, while the selectivity decreases seriously.The performance is also influenced by permeating temperature, not related to feed pressure. The functional membrane prepared with nano-charcoal powders improves the CO2 permeability more or less, but has little effect on other gases. Compared with nano-charcoal powders, incorporating nano-charcoal raw powders enhances the gas permeability a little,while the slectivy has no change. The prepared composite functional memebranes dopped with MWNT exhibit high CO2 peameability and selectivity.As a result, membranes with high CO2 permeaselecticity can be prepared through controlling the doping agents, amount and conditions of carbonization.