Preparation Of Microporous Carbon And Adsorption Properties Of CH₄/N₂

Coalbed methane?CBM?attracts much attentionand it is of great significance to utilize CBM for improving the energy structure and easing air pollution.The challenge of CBM recovery is the separation of methane and nitrogen economically and effectively.Pressure swing adsorption is an attractive technology because of strong applicability,flexible operation and the key point is to develop efficient adsorbent.Porous carbon materials,with abundant pore structure,adjustable surface properties,good stability,become the attaactive CH₄/N₂separation adsorbent.This paper is focused on the research of the preparation of microporous carbon and the related adsorption properties of CH₄/N₂.First,the microporous carbonaceous adsorbent was synthesized via polymer pyrolysis and template method.The effect of preparation conditions on the pore structure and adsorption property of the adsorbant was examined.N₂ adsorption,XRD,FT-IR and SEM were used to characterize the microstructure.Adsorption isotherms of CH₄/N₂ of the sample were examined.The Langmuir and Freundlich model were used to fit the experimental data and the selectivity was calculated.The results showed that the adsorbents prepared by polymer pyrolysis existed developed pore structure.The optimum preparation conditions were 800°C at the heating rate of 10°C/min for 1 h and the surface area,pore volume,microporosity of the sample under this condition were 1086 m²/g,0.5248 cm³/g,95.71%respectively.The optimum activation process preparation conditions were the ratio of KOH and carbon 4,800°C at the heating rate of 5°C/min for 1 h and the surface area,pore volume,microporosity of the sample under this condition were 2138 m²/g,1.0987 cm³/g,87.49%respectively.The CH₄ and N₂ adsorption isotherm on PC-8-10-1 showed that the equilibrium adsorption capacity of CH₄ is greater than N₂ and the fitting results of Langmuir and Freundlich were accurate.The adsorption heat of CH₄ was greater than N₂ and both near20²5 kJ/mol.The selectivity?calculated by Henry constant increased with the increasing of temperature and?reached 4.59 at 318 K.The microporous carbonaceous adsorbents prepared by template method existed large surface area and pore structure and the double-impregnation was better than single-impregnation.The Langmuir and Freundlich fitting of adsorption isotherms of CH₄/N₂on the sample TPC-9-2 were accurate.The adsorption heat of CH₄ was greater than N₂ and both of them increased with increasing of adsorbed capacity.The selectivity calculated by the ratio of adsorbed capacity reached the maximum at 100 kPa and increased with the increasing of temperature.And S_ijj reached near 5.5 at 323 K,so atmospheric absorption and low pressure desorption were considered.The selectivity?calculated by Henry constant increased with the increasing of temperature and?reached 5.0077 at 323 K.Two kind of carbonaceous adsorbents have obvious advantages than other zeolite-like and MOFs.The study of adsorption equilibrium can provide basic data for PSA process development.