Preparation Of Porous Carbon GSs/MF@Cs And Its Separation And Enrichment Of Low-concentration Coalbed Methan

Although porous carbon usually exhibits a higher specific surface area and well-developed pore structure than other adsorbent materials（MOFs,Zeolites,Porous Polymers）,it is cost effective and environmentally friendly.However,the prevalent low selectivity and low adsorption capacity cannot achieve effective separation and enrichment of low concentration CBM CH₄,mainly attributed to the inactive surface chemistry and wide pore size distribution of porous carbon materials.It is shown that the synthesis of carbon materials with ultra-microporous structure or modified by functional groups can significantly improve the gas selectivity and adsorption capacity of porous carbon materials,which can facilitate the separation and enrichment of CH₄ from low-concentration CBM CH₄.In this paper,cheap grape seed（G）and starch（A）biomass were used as carbon sources,and high N doped grape seed based carbon material GSs and starch based carbon material MF@Cs with ultrafine pore structure were prepared by Na NH₂ chemical activation method and KOH chemical activation method respectively.Moreover,physical adsorption apparatus and competitive adsorption apparatus were used to detect their effect on CH₄/N₂/CO₂ gas Adsorption and separation performance.The main research contents and results are as follows:1.The influences of hydrothermal concentration H（C）and temperature H（T）on the yield of carbon Precursor G-precursor was explored,and the conclusion is as follows:The hydrothermal carbon synthesized at 200℃@6g/60m L（HC/DIW）has the best yield of 55.11%,which is higher than that reported in most literatures.The prepared GSs porous carbon materials through Na NH₂low-temperature activation,the SEM images clearly showed that GSs possessed abundant pores.BET show that GSs is a typical microporous and mesoporous graded carbon material with a pore size distribution of 0.3-4 nm.GSs porous carbon material has prominent pore structure parameters,with a maximum specific surface area of 3909 cm²/g and a total pore volume of 1.85 cm³/g.It has high adsorption capacity for CO₂,CH₄ and N₂,and the adsorption capacity for CO₂ exceeds 5 mmol/g at 273K.The selectivity of GSs for CO₂/N₂,CO₂/CH₄ and CH₄/N₂ separation was predicted by IAST,and the highest selectivity values of GSs were 71.4,21.3 and 6.0,respectively,which were higher than those of carbon adsorbents reported in most literatures.In addition,the thermodynamic equations of Na NH₂ in different temperature ranges were systematically explored with the help of thermodynamic analysis software HSC and TG-IR,which provided certain theoretical and technical support for exploring the activation mechanism and pore-forming mechanism of Na NH₂.Linear regression analysis was made on the pore volume of GSs with different pore sizes and the adsorption capacity of CH₄,N₂and CO₂,respectively.It was found that the adsorption capacity of CH₄,N₂ and CO₂ mainly depends on the ultrafine pore volume（<1 nm）of GSs.2.The effects of activation temperature（T）,alkal-carbon ratio（n）and activation time（t）on CH₄/N₂ adsorption performance of porous carbon MF@Cs were explored,and the following results were obtained:When the activation temperature T=750℃,the alkal-carbon ratio n=1,and the activation time T=1.5h,the carbon material MF@C-1-750 shows good competitive adsorption and separation performance for CH₄/N₂ of low concentration coalbed methane.The penetration time of CH₄ was10.12min,which was larger than that of N₂（8.97min）,and the separation factor of CH₄ on N₂ was 3.2.The prepared MF@Cs carbon materials were characterized by SEM with nanosphere structure,which was conducive to the uniform distribution of active adsorption sites and to promote the separation and enrichment of low-concentration coalbed methane CH₄.BET test shows that MF@Cs is a typical microporous carbon material with a pore size of 0.3-2nm and a maximum pore size of0.6nm,close to the kinetic diameter of CH4（0.36nm）,which is conducive to the separation and enrichment of low-concentration coalbed methane CH₄.The BET specific surface area(S_BET)of MF@Cs is as high as2415.9 cm²/g,the total pore volume V_T is 1.36 cm³/g,and the ultrafine pore volume V_{0.3-1.0 nm} is 0.42cm³/g.According to ASAP 2460 physical adsorption apparatus,the static adsorption capacity of MF@Cs for CH₄ at273K and 100k Pa is as high as 2.8 mmol/g,which is higher than the CH₄adsorption capacity of carbon materials reported in most literatures.3.The application of porous carbon MF@Cs for CO₂ adsorption is expanded,the adsorption performance of porous carbon MF@Cs for CO₂is explored,and the potential and value of porous carbon material MF@Cs in the field of gas adsorption and separation is comprehensively analyzed and explored.Through the detection of ASAP 2460 physical adsorption apparatus,the static adsorption capacity of MF@C-1-750 to CO₂is as high as 6.5 mmol/g at 273K and 100k Pa.MF@C-2-700 is also excellent.Under the same test conditions,its static adsorption capacity for CO₂ is as high as 6.1 mmol/g,which is higher than that of most adsorbent materials reported in the literature.Through the linear regression analysis of the ultrapore capacity of MF@Cs porous carbon material and the static adsorption capacity of CO₂,it is found that the static adsorption capacity of CO₂ largely depends on the ultrapore capacity of carbon material,and its correlation R²=0.82.The competitive adsorption properties of carbon materials for CO₂/N₂ and CO₂/CH₄ were tested by penetration experiments.Compared with CH₄and N₂,CO₂showed longer penetration time and more prominent dynamic adsorption capacity.The simple preparation process,low preparation cost,excellent specific surface area and pore volume,and excellent CO₂ gas adsorption performance of MF@Cs porous carbon material are expected to play a huge application potential in the future adsorption and separation of mixed gas.