| Membrane technology,a kind of separation technology,has been developed for nearly half a century.Due to the advantages of high separation efficiency,simple operation,and low energy consumption,etc.,membrane technology has been widely applied.However,the traditional commercially available polymeric membrane is usually suffered from the weakness of poor thermal and chemical resistance,and inferior separation performance.Therefore,it is urgent to develop novel and high performance membrane materials.In recent several decades,carbon membrane,as a novel inorganic membrane material,has been paid wide attention,which can conquer the weakness of organic membrane and present good separation performance.Nevertheless,the issues of high fabrication cost and fragile nature have strictly prohibited the application of carbon membranes for large-scale industries.Regarding this,supported carbon membrane with high mechanical strength was prepared in this thesis.Simultaneously,carbon materials were incorporated to optimize the microstructure and separation performance.In addition,a further investigation was conducted on the application of intensification of hydrogen production from methanol steam reforming.First of all,unsupported hybrid carbon membranes were prepared by using BTDA-ODA type polyimide as precursor materials and several carbon materials(i.e.,grapheme,carbon nanotube and activated carbon fiber)as additives.Some advanced characterization techniques,i.e.,TGA,FTIR,XRD,SEM,etc.,were applied to study the pyrolysis behavior of precursor during pyrolysis,the evolution of surface elements or functional groups,and the microstructural morphology and structure of the resultant carbon membranes.Besides,magnetic field was also adopted to optimize the microstructure and fabrication procedure of carbon membranes.Then,supported carbon membranes were also obtained by the processes of spin-coating,drying,membrane formation and pyrolysis on the support of high mechanical strength porous carbon plates.Moreover,the influences of molding pressure of supports,graphene usage,permeating temperature and pressure on the microstructure and gas separation performance of holing supported carbon membranes were investigated.Finally,the supported carbon membranes were utilized to intensify the hydrogen production reaction of methanol steam reforming.In addition,the effects of reaction temperature,reaction time,catalyst carrier,separation property of carbon membranes on the conversion and yield were studied.Results showed that:(1)During membrane formation,the application of external magnetic field is helpful for the improvement of gas permeability of the resultant carbon membranes.When the magnetic strength is 10 Gs,the gas permeability of carbon membranes reaches to 546Barrer(H2),349Barrer(CO2),148Barrer(O2),24Barrer(N2),together with the selectivities of 22.5(H2/N2),6.1(O2/N2),14.4(CO2/N2).(2)The carbon material hybrid unsupported cabron membranes are commercially attractive for their gas separation performance,which locates above the Robeson’s upper bound.(3)The resultant carbon membranes have excellent gas permeability due to the fairly well compatibility between graphene and membrane matrix.When the mass fraction of graphene is 0.3%,supported carbon membranes respectively present the permeability of 5229 Barrer,1315Barrer,1123 Barrer and 529 Barrer for H2,CO2,O2 and N2,along with the selectivities of 9.9,2.5 and 2.4 for H2/N2,CO2/N2 and O2/N2.(4)In the case of reaction of methanol steam reforming for hydrogen production,the optimum reaction temperature of fixed bed reactor is 260oC,in which the methanol conversion rate is 71.33% and the hydrogen yield is 21.39%.The optimum reaction temperature of the carbon membrane reactor is 280oC with the methanol conversion and hydrogen yield respectively being 93.29% and 29.15%. |
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