The Preparation Of Nitrogen-doped Porous Carbon Materials For Carbon Dioxide Capture And Conversion

The rapid development of human society has led to the acceleration of energy consumption,and the result of energy consumption is the emission of excessive CO₂ into the atmosphere,which leads to an out-of-balance in the earth’s carbon cycle.In order to achieve the purpose of CO₂ emission reduction:on the one hand,reduce carbon emissions by improving energy use efficiency;on the other hand,CO₂ is captured and converted into fine chemicals to meet social needs.At present,porous carbon materials are regarded as a promising CO₂ adsorbent due to their excellent environmental protection,hydrophobicity,adjustable pore structure,thermodynamic stability,comprehensive resource availability,and non-uniform doping.There are still many shortcomings in CO₂ capture performance.Therefore,improving the CO₂adsorption performance of porous carbon materials is a problem that needs to be solved urgently.The introduction of nitrogen not only improves the hydrophilicity of the carbon material surface,but also allows the carbon material to obtain a porous structure while forming a large number of nitrogen-containing basic groups on the surface,which not only improves its adsorption performance for CO₂,but also possess certain application value in the field of CO₂ catalytic conversion.Therefore,the preparation of nitrogen-doped porous carbon materials is of great significance for CO₂ capture and conversion.In this paper,three different nitrogen-doped porous carbon materials are synthesized for CO₂ capture and conversion.The main research content is divided into the following three aspects:（1）We use glucose as the carbon source,urea as the nitrogen source,and potassium acetate as the activator to synthesize a series of glucose-based nitrogen-doped porous carbon materials GUC-x（x is the mass ratio of potassium acetate to glucose）.By adjusting the amount of potassium acetate,the structural parameters and nitrogen content of the nitrogen-based porous material are controlled to achieve high nitrogen content while having a high specific surface area.Characterizated by BET,XRD,XPS,elemental analysis and proves that GUC-0.5 has a high specific surface area and a rich nitrogen content.It has the best adsorption performance for CO₂ and the highest efficiency for CO₂ cycloaddition.There is no obvious loss of catalytic activity after the cycle experiment,indicating that nitrogen doping is very important for catalytic activity.（2）By pyrolyzing vitamin B9 as a dual source of carbon and nitrogen,and then using the activator KOH to activate the vitamin B9 carbonaceous material,a series of porous activated carbon materials PAC-n are prepared（n is the mass ratio of KOH to vitamin B9 carbonaceous material）.The specific surface area and nitrogen content of the porous activated carbon material are controlled by adjusting the amount of KOH,so as to realize the coexistence of the specific surface area and high nitrogen content in the porous activated carbon.Through BET,XRD,Raman,XPS,elemental analysis and other characterizations,the effects of specific surface area and nitrogen on CO₂ adsorption are explored,and the results shows that the adsorption is a physical adsorption process.Then PAC-n is applied to the atmospheric pressure CO₂cycloaddition reaction.After catalyst screening and reaction factor optimization,the results show that when the reaction temperature is 100℃,the time is 8 h,the tetrabutylammonium bromide（TBAB）is 0.03 g and the amount of PAC-2 is 0.05 g,the yield of CO₂ cycloaddition can reach 89-94%.Subsequently,the cycle stability of the catalyst is explored,and it is found that the XRD spectrum and Raman spectrum of the catalyst after 5 times of use were basically unchanged from the original,indicating that the performance of the catalyst was stable.（3）Using niacin as the carbon source and KOH as the activator,a nitrogen-doped porous carbon material NAC-700 is prepared by a two-step method.The structure and morphology are characterized by BET,XRD,XPS,SEM and TEM,and it is found that NAC-700 has good CO₂adsorption performance.Using NAC-700 as the catalyst for the cycloaddition of CO₂ and styrene oxide,and tetrabutylammonium bromide（TBAB）as the co-catalyst,the results show that under relatively mild conditions（100℃,8 h,1 bar CO₂）,it can It catalyzes the cycloaddition reaction of CO₂ and styrene oxide,and after repeated use for 5 times,it still has quite high catalytic activity.