Preparation Of Ultramicroporous Carbon And Its Separation And Enrichment Of Low Concentration Coalbed Methane CH₄

Guizhou Province has a large reserve of low concentration coalbed methane,which is less than 30%of coalbed methane,ranking second in the country in total.Increasing CH₄ concentration in low-concentration coalbed methane is a major direction to improve its utilization.Based on atmospheric pressure adsorption vacuum desorption is more suitable for the separation and enrichment of low concentration coalbed methane CH₄ in Guizhou.The adsorbent is the key to this technology.Activated carbon is used as an adsorbent because of its high specific surface area,low cost,and recycling.However,it has problems such as uneven distribution of pore structure,low ultramicroporous ratio of pore size<1 nm,and excessive acidity of surface oxygen.The effect of concentration and separation of CH₄ is not good.In order to improve the concentration of CH₄ in low-concentration coalbed methane in Guizhou,the adsorbent with a high specific surface area and a microporous pore size concentrated in less than 1 nm is not required to be successfully developed.Aiming at this problem,this paper starts with the separation and enrichment mechanism of low concentration coalbed methane CH₄,with the aid of N₂adsorption/desorption isotherms,FTIR and Boehm titration.Analyze the specific surface area of the adsorbent,the microporous structure,the surface acidity and alkalinity,and the performance of the modified ions on the separation and enrichment of low concentration coalbed methane CH₄ on microporous carbon.The effects of various preparation conditions and modification methods on the performance of microporous carbon separation and enrichment of low concentration coalbed methane CH₄ were investigated,and the optimal preparation scheme for low concentration coalbed gas CH₄ separation and enrichment adsorbent was obtained.The specific research contents are as follows:The effect of grape seed-based microporous carbon(GAC_K-X)on the separation and enrichment performance of low concentration coalbed methane CH₄ was studied.The effects of activation time,heating rate and alkali-carbon ratio on the adsorption performance of microporous carbon were discussed.The results show that the ratio of alkali to carbon has the greatest influence on the performance of microporous carbon,and the activation time and heating rate have little effect on microporous carbon.As the ratio of alkali to carbon increases,the specific surface area and ultramicroporous pore volume（<1 nm）of GAC_K-X increase first and then decrease.When the ratio of alkali to carbon is 3.5,the specific surface area and microporous pore volume of PAC_K-3.5 are the highest,which are 897.32m²/g and 0.29cm³/g,respectively,which has the highest selective adsorption amount to low concentration coalbed methane CH₄.25.08 ml/g.The effects of activation time,heating rate and alkali-carbon ratio on the adsorption performance of polyvinylidene chloride microporous carbon PAC_K-X-X were investigated.The results show that the ratio of alkali to carbon has the greatest influence on the performance of microporous carbon,and the activation time and heating rate have little effect on microporous carbon.As the ratio of alkali to carbon increases,the specific surface area of PAC_K-X and the pore volume of the microporous pores increase first and then decrease.When the ratio of alkali to carbon is 3,the specific surface area and microporous pore volume of PAC_K-3.5 are the highest,which are 1999.24m²/g and 0.39cm³/g,respectively,which has the highest selective adsorption amount to low concentration coalbed methane CH₄.38.00 ml/g.The effect of PAC_K-T-X%microporous carbon on the separation and enrichment performance of low concentration coalbed methane CH₄ was studied by using Ni（Ⅱ）ion modified polyvinylidene chloride microporous carbon(PAC_K-3.5).II)Effect of ion and activation temperature on the adsorption properties of microporous carbon.The results show that both Ni（Ⅱ）ion and activation temperature have a certain effect on the performance of microporous carbon.With the increase of Ni（Ⅱ）ion and activation temperature,PAC_K-T-X%micropore specific surface area and ultramicroporous pore volume There is a slight decrease,When the Ni（Ⅱ）ion mass fraction is 6%and the activation temperature is 750°C,the PAC_K-T-X%micropore specific surface area and ultramicroporous pore volume are 1929.58 m²/g and 0.34 cm³/g,respectively,for low concentration coal seams.The selective adsorption capacity of gas CH₄ is the largest,reaching 50.67 ml/g.