Study On Preparation And Adsorption Properties Of Coal-based Activated Carbon By Steam Activation

The CH₄ concentration of coalbed methane extracted from underground coal mine is low,generally 18%～32%.The commercial use of coalbed methane requires the separation of CO2,N2 and other gases,and the purification and concentration of coalbed methane.Pressure swing adsorption（PSA）is one of the important methods to purify CH₄.The key of purification is to develop adsorbents.In this paper,anthracite was used as raw material,and the preparation process,pore structure and adsorption performance of coal based activated carbon were studied based on steam activation method.Through theoretical and experimental analysis,the main results are as follows:① The optimal preparation process of coal based activated carbon in N2 atmosphere was obtained,that is,the preoxidation temperature was 430℃,The pre oxidation time is 1h,The carbonization temperature is 600℃ and the carbonization time is 2.5h,activation temperature 900℃,activation time 2.5h,the activation rate is 1.33ml/min;The BET specific surface area of coal based activated carbon prepared by the above method is 782.04m2/g.The total pore volume is 0.468cm3/g.The micropore volume accounted for 81.9%.②In the process of preparing coal based activated carbon by steam activation,preoxidation and activation have great influence on the properties of coal based activated carbon,while carbonization has little influence on the pore structure of coal based activated carbon.③ When the steam rate increases to a certain extent,the microstructure of coal based activated carbon will collapse to a certain extent,resulting in the decrease of micropore volume;in addition,the stability of activated carbon crystal structure can be enhanced to a certain extent by appropriately increasing the pre oxidation temperature in the preparation process.④ In the series of coal based activated carbon samples,the separation coefficient s of LN-2 is the highest that is 3.17,the separation effect is the best,which indicates that the activation rate is moderate in the preparation process parameters,and appropriate increase of activation time is helpful to the formation of micropores.⑤Langmuir model and pseudo second order adsorption kinetic equation can well reflect the adsorption law and adsorption kinetic characteristics of coal based activated carbon.The research results enrich the theory and technology of adsorbent research and development,and have important scientific significance and engineering practical value.