Effects of activated carbon pore distribution on CH4 adsorption

ZHANG Shuangquan; QING Tao; YU Delei; HOU Shuai; WEI Wenxuan; LI Xiaoshen; ZHANG Yu

Abstract：To separate and concentrate CH4 in coal mine gas,Taixi anthracite was used as raw material and steam as activation medium to explore the effects of technological conditions under the action of additive on the pore structure of the activated carbon and its CH4 adsorption performances.The results show that the key factor influencing the CH4 adsorption capacity is the pore volume with the pore diameter between 0.6 and 0.8 nm,and no matter how technological condition changes,as long as the pore volume within the range of 0.6-0.8 nm rises,the CH4 adsorption capacity increases.Taking NH4Cl and KNO3 as additives,the technological conditions such as activation degree,carbonization heating rate,carbonization temperature,activation temperature and so on have little influence on the microporosities of the activated carbons,which maintain at about 91％,but have great influence on the micropore distribution.NH4Cl and KNO3 can increase the formation of small micropores (＜1 nm),especially the micropores within 0.6-0.8 nm,which can improve the CH4 adsorption capacity effectively.Too low or too high burn off of the activated carbon does harm to the formation of the pores within 0.6-0.8 nm,the suitable burn off is 30％-40％.High carbonization heating rate is not helpful to improve the pore volume within the range of 0.6-0.8 nm,and the suitable heating rate is 3 to 5 ℃/min.Too low or too high carbonization temperature hinders the formation of the pores within the range of 0.6-0.8 nm,and the suitable carbonization temperature is 650 ℃.Generally,activation temperature has little influence on forming the pores within the range of 0.6 to 0.8 nm,the suitable activation temperature is 880 ℃.The activated carbon prepared under the optimum conditions mentioned above can reach a CH4 adsorption capacity of 24.31 mL/g.