Preparation Of Porous Carbon Materials By Catalytic Carbonation On Magnesium Oxide Template

The preparation of carbon materials by hard-template method has the advantages of controllable morphology and easy removal of the template.Different carbon precursors can be used to fabricate porous carbon materials with high specific surface area when MgO as the template.Carbon source not only affects the yield of porous carbon materials,but also has an important influence on the morphology,pore structure,and surface properties,thereby affecting its applications.In this paper,the MgO as a template,the porous carbon sheets were carbonized in a closed autoclave using mixed polymers and several typical aromatic compounds as carbon sources,respectively.The effects of carbon sources on the yield,morphology,pore structure and surface composition of porous carbon were studied.The application of porous carbon materials in methylene blue adsorption,CO₂ adsorption,and electrode materials of supercapacitors were explored.Details are as follows:1.The mixed polymer consists of polypropylene,high density polyethylene,low density polyethylene,polystyrene,polyethylene terephthalate and polyvinyl chloride was used to carbonize the porous carbon sheets on the sheet MgO template at 500°C.As the weight ratio of MgO/mixed polymer increased,the yield of carbon sheets increased gradually,and the carbon yield reached a maximum of 26.5 wt%when the weight ratio was 6.As the weight ratio of MgO/mixed polymer continues to increase to 8,the yield of carbon sheets decreases slightly.MgO plays a role in shape control during the growth of carbon sheets.When the MgO/mixed polymer mass ratio was 6,the specific surface area of the obtained porous carbon sheets reached 713 m²/g,and the pore volume of the porous carbon sheets was up to5.27 cm³/g at the weight ratio of 4.The weight ratio of MgO/mixed polymer has no significant effect on the pore size distribution of the carbon sheets.In addition,the mechanism of carbonization reaction was explored by analyzing the effect of reaction time on the distribution of carbonized products and the components of gas and liquid products.The results show that the aromatic compounds produced by the pyrolysis of the mixed polymer are the main reactants for the formation of porous carbon sheets.Model experiments using small-molecule aromatic compounds further validated this rule and found that the carbon-forming rate of polycyclic aromatic hydrocarbons,especially acene,was higher.This method provides a theoretical basis for the conversion of waste mixed plastics into porous carbon materials in municipal solid waste.2.In order to study the influence of N element on the porous carbon material in the carbon source,the ternary aromatic compounds with similar structure of carbazole,phenanthrene,and acridine were used as the carbon source when MgO was used as the template and the reaction temperature was 500°C.The N-doped carbon materials prepared by using carbazole and acridine as the carbon sources.The porous carbon sheets were further activated with KOH under an argon atmosphere at 800°C.The carbon materials have a richer pore structure,higher specific surface area as well as larger pore volume after KOH activation.The porous carbon sheets obtained derived from carbazole has an ultra-high specific surface area?3115 m²/g?and a large pore volume?2.64 cm³/g?.The porous carbon sheets were used as the adsorbents and anode materials for CO₂,methylene blue and supercapacitors,respectively.The porous carbon sheets obtained with phenanthrene as the carbon source had the highest uptake capacity of 4.82 mmol/g at 273 K among all carbon sheets,indicating that the smaller pore size was in favored of CO₂ adsorption.The porous carbon sheets were obtained from carbazole has the largest adsorption capacity for methylene blue,reaching 952 mg/g.When the porous carbon sheets were derived from carbazole as the electrode materials,with the maximum specific capacitance of 230 F/g for 1 mol/L H₂SO₄electrolyte at the current density of 1 A/g.The defect that N in the N-doped porous carbon sheets escapes after activation may be the main reason for the increase of its methylene blue adsorption capacity and specific capacitance.