Preparation Of Nano-structured Porous Carbon Monoliths And Its Application In CO₂Adsorption And Separation

Predictions of future climate change have triggered extensive researches for ways to mitigate the emissions of "greenhouse" carbon dioxide (CO2). Among the various technologies and processes that have been developed for the capture of CO2, sorption based separation by using solid CO2sorbents has attracted much attention over several years. Porous carbon material is considered to be one of the most promising candidates for CO2capture due to its low cost, high thermal and chemical stability, excellent CO2adsorption capacity and facile regeneration ability.Inheriting our previous work, according to the mancini reaction and polymerization system of phenolic-amine, we have successfully synthesized nan-structured porous carbon monoliths, which exhibit excellent CO2adsorption ability.Through the experiment, we get some conclusion. Firstly, if the nitrogen riched melamine is added into the resorcinol, formaldehyde polymerization system, it is helpful to form nano-structured porous carbon with higher surface area and larger microspore volume, and the surface chemistry also got modified. Secondly, the amount of melamine obviously affects the pore structural of the as-synthesized porous carbon. Thirdly, different pyrolyzing temperatures show great influence in the structural qualitative. Fourthly, it is beneficial to form a nano-structured porous carbon with high surface area and microspore volume when glutamic acid is added, and its capacity of gas adsorption is also improved.For the practical application, volumetric based CO2capture ability is seriously important. Based on this consideration, we designed to optimize the structure features of HCM by using the original porosity of porous carbon and repeated dipping-crystallization method. The HCM-Cu3(BTC)2composites were synthesized by in situ restrictively incorporate MOFs crystal inside the matrix of HCM. The composite shows high CO2uptakes of22.7cm3cm-3on a volumetric basis, which is nearly as twice as the uptakes of original HCM. In addition, the dynamic gas separation measurement was carried out and illustrated that CO2could be easily separated from N2under the ambient conditions by the composite. Further, it achieves a high separation factor for CO2over N2, ranging from67to100, reflecting a strongly competitive CO2adsorption. A facile CO2release can be realized by purging an argon flow through the fixed-bed adsorber at25℃, indicating the good regeneration ability.It is well known in adsorption science that CO2adsorption processes require porous materials with high specific surface area (SSA), specially micropore SSA, accessible to CO2molecules. Clearly, in order to maximize the CO2sorption at the desired conditions, one needs not only to maximize the number of adsorption sites, but also tune the pore size and the CO2-solid interaction energy that would allow more sorption sites to adsorb CO2molecules. In the fifth chapter, using an innovative method by in suit etching to create micropore for the enhancement of CO2capture, we synthesized microporous carbon materials with high micropore SSA and excellent CO2capture ability. HCM-ZC-1shows a high CO2adsorption capacity of5.4mmol g-1(23.8wt%) at273K and3.8mmol g-1(16.7wt%) at298K. The excellent CO2storage performance of HCM-ZC-1was compared with the capacities of those carbon and MOFs materials described in the recent literature, which yielded the best known performance under identical conditions. In addition, using the DFT method, we have systematically investigated the relationship between the pore size and CO2adsorption capacity in different test conditions. We conclude that under room temperature,0.7nm is the most suitable pore size for CO2adsorption under the CO2partial pressure of0.15bar. Lower temperature or higher pressure relates to the optimal pore size of larger than0.7nm.