Synthesis, Characterization And Application In CO₂Adsorption Of Basic Porous Carbon Materials

Because of their remarkable properties such as high specific surface area, large pore volume, good chemical, hydrothermal and mechanical stability, wide spread raw sources and low cost, porous carbon materials have attracted great attention of researchers. At present, porous carbon materials have been widely used as adsorbents, gas storage and separation materials, catalysts and electrode materials in electrochemical double layer capacitors (EDLC). The issue of CO2capture using carbon based adsorbents has gained great attention since CO2is regarded as a greenhouse gas as well as a valuable carbon resource. Two main factors are considered to influence the CO2adsorption performance of the adsorbents:the micropore volume of the adsorbents and the basic groups on the surface of the absorbents. In order to get rich surface basic groups, many scientists devoted themselves to post-synthetic amine modification or ammonia treatment of activated carbon or zeolites. But these methods lead to materials lacking stability which limited their large-scale applications. It is of great importance to synthesize a kind of microporous carbon material with good hydrothermal stability and rich basic groups.In this paper, microporous carbon materials with basic groups were prepared by using the cetyl trimethyl ammonium bromide (CTAB) as the soft template and resorcinol (R)/formaldehyde (F) as the carbon sources through hydrothermal method under basic conditions. Different nitrogen sources (Ammonia, Ethylenediamine, Urea, Pyridine, Tripolycyanamide, etc) were added to the synthetic system to increase the surface basicity of the samples. The physical and chemical properties of the obtained carbon materials were characterized by N2physical adsorption, SEM, CO2-TPD, element analysis and Boehm titration. The results showed that ammonia was the most promising nitrogen source because it was used as both the catalyst and the nitrogen source.In addition, a quick, simple, environment friendly and low-cost method of synthesizing carbon monolith with high nitrogen content is introduced. Commercial soybeans were used as both the carbon and nitrogen sources. The basic carbon materials were prepared by simple carbonization and steam activation of the soybeans. The physical properties of the obtained carbons were characterized by N2physical adsorption and SEM. Boehm titration, FT-IR, CO2-TPD and element analysis were used to characterize the chemical properties of the carbon materials. The results showed that, the nitrogen element in soybeans was preserved in situ in the carbon matrix during carbonization and activation. It made a significant contribution to the surface basicity of the carbon materials. And the content of basic groups increased gradually with the extension of activation time. The obtained basic carbon materials were used as adsorbents for low concentration CO2capture. It was found that the basic carbon material BC-sa-800-5had a good result in separating the mixture gas of CO2and N2. The separation coefficient reached up to8.33. Results also showed that after recycling of BC-sa-800-5for6times, its CO2adsorption capacity remained stable.