Studies On The Effect Of N Doping On Adsorption And Dehydrogenation Properties Of Humic Acid-based Porous Carbon

Porous carbon has attracted people’s attention due to its high specific surface area,developed pore structure and abundant surface functional groups.The design and control of porous carbon pore structure is the key to improve its adsorption performance.In this paper,low-rank coal was used as raw material to extract humic acid from lignite,and humic acid-based porous carbon was prepared by doping modification.The preparation method of nitrogen-doped humic acid-based porous carbon was studied.Porous carbon with different pore size and specific surface area was prepared by activation method under different preparation conditions.The physical structure and surface morphology of porous carbon materials were characterized by means of surface area analyzer,infrared spectrometer and thermogravimetric analyzer.The adsorption performance of dyes and the catalytic performance of propane dehydrogenation were studied.The main results of this paper are as follows:（1）Using lignite as raw material,the extraction and separation of humic acid were achieved by alkali-soluble acid precipitation method.Nitrogen-doped porous carbon was prepared by activation method using black humic acid and fulvic acid as carbon sources,respectively.The effects of different preparation conditions on the structure and properties of nitrogen-doped porous carbon were investigated by changing the doping nitrogen content,calcination temperature and calcination atmosphere.The experimental results show that when the mass ratio of humic acid to melamine is 5:1,the prepared black humic acid-based porous carbon C-D-1 has the largest pore volume and specific surface area of 0.46 cm³/g and 706 m²/g,respectively.When the calcination temperature was 900°C,the prepared black humic acid-based porous carbon C-D-900 had the largest pore volume and specific surface area of 0.46cm³/g and 730 m²/g,respectively.When the calcination atmosphere was argon gas and carbon dioxide,the prepared black humic acid-based porous carbon C-D-Ar+CO₂ had the largest pore volume and specific surface area of 0.49 cm³/g and 797 m²/g,respectively.When the mass ratio of humic acid to melamine was 5:3,the prepared fulvic acid-based porous carbon C-U-3 had the largest pore volume and specific surface area of 1.13 cm³/g and 1886 m²/g,respectively.It is indicated that under the same preparation conditions,the fulvic acid group has a larger pore volume and specific surface area.（2）The adsorption performance of porous carbon on Congo red,Rhodamine B and Basic orange 2 dyes was studied by using the porous carbon prepared above as the adsorbent.Studies have shown that black humic acid based porous carbon C-D-1has the best adsorption effect on Congo red,Rhodamine B and Basic orange 2 dyes when the dye concentration is 200 mg/L.The corresponding adsorption amounts were78.74 mg/g,90.37 mg/g and 179.34 mg/g,respectively.The black humic acid-based porous carbon C-D-900 has the best adsorption effect on Congo red,Rhodamine B and Basic orange 2 dyes when the dye concentration is 200 mg/L.The adsorption capacities were 104.22 mg/g,105.80 mg/g and 193.37 mg/g,respectively.When the dye with a concentration of 200 mg/L was adsorbed under the condition of changing the calcination atmosphere,the black humic acid-based porous carbon C-D-Ar+CO₂had the best adsorption effect on Congo red,Rhodamine B and Basic orange 2 dyes.The corresponding adsorption amounts were 136.20 mg/g,116.67 mg/g and 196.41mg/g,respectively.When the dye concentration is 200 mg/L under the condition of changing the nitrogen content,the fulvic acid-based porous carbon C-U-3 has the best adsorption effect on Congo red,Rhodamine B and Basic orange 2 dyes.The corresponding adsorption amounts were 196.43 mg/g,180.64 mg/g and 198.80 mg/g,respectively.The fulvic acid-based porous carbon has the largest adsorption capacity for dyes.It shows that the pore volume and specific surface area of porous carbon are larger,and the microporous pore structure is more developed,and the adsorption effect is better.（3）The catalytic effect of dehydrogenation of propane was investigated by using different nitrogen-doped porous carbon as dehydrogenation catalyst.The experimental results show that when the dehydrogenation temperature of propane is 320°C,350°C,370°C and 400°C,the propylene formation concentration of undoped porous carbon C-D is 1.69%,3.84%,4.86%and 5.67%,respectively.The propylene formation concentration of the doped porous carbon C-D-1 was 2.75%,4.07%,5.30%,and6.62%,respectively.It can be concluded from the experimental data that the concentration of propylene is continuously increased as the temperature of the dehydrogenation reaction of propane increases.When the nitrogen-doped porous carbon C-D-1 catalyzes the reaction,the target product propylene is formed at the highest concentration.