高品质低阶煤基活性炭的制备与表征

Preparation and characterization of high quality low-rank coal based activated carbon

以国内外8种低阶煤为原料,在相同工艺条件下采用KOH活化法制备低阶煤基活性炭,利用低温N2吸附、傅里叶红外光谱(FTIR)及X射线光电子能谱(XPS)等对活性炭的孔结构及表面化学性质进行表征,考察原料煤的物理化学特性对低阶煤基活性炭孔结构的影响及其表面化学性质。结果表明:在碱炭质量比为3∶1、活化温度为650℃、活化时间为0.5 h、升温速率为10℃/min、保护气流量为200 mL/min的条件下,可制备出比表面积为1 694～2 956 m2/g、总孔容为0.909～1.949 cm3/g、中孔率为37.3%～71.1%的高品质低阶煤基活性炭;低阶煤自身固有的物理化学特性对活性炭的孔结构具有重要影响,原料煤原生孔隙丰富、挥发分高有利于活性炭中孔的发育;煤中无机矿物成分不仅会削弱活化反应的剧烈程度,而且会降低活性炭的质量及性能;低阶煤基活性炭表面含有丰富的含氧官能团,其中以羰基及酚羟基(或醚类)为主,其次为内酯基和羧基。

Low-rank coal based activated carbons were prepared from eight kinds of low-rank coal in home and abroad market with KOH as activation agent under the same technological condition.The pore structure and surface chemical properties of activated carbon were characterized by nitrogen adsorption at 77 K,Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectroscopy（XPS）.In addition,the surface chemical properties of low-rank coal based activated carbon and the influence of the physiochemical characteristics of raw coal on pore structure of activated carbon were investigated.The results show that high quality low-rank coal based activated carbon can be prepared under the condition：the ratio of KOH to low-rank coal is 3∶1,the activation temperature is 650 ℃,activation time is 0.5 h,heating rate is 10 ℃/min and nitrogen flow rate is 200 mL/min.The carbon＇s specific surface area is 1 694-2 956 m2/g,total pore volume is 0.909-1.949 cm3/g and the ratio of mesopore is 37.3%-71.1%.The inherent physiochemical characteristics of low-rank coal have important effects on the pore structure of activated carbon.Abundant primitive pores and high volatile of raw coal are advantageous to develop mesopore,and the mineral not only weakens the activation reaction intensity,but also degrades the quality and performance of activated carbon.There are abundant oxygen-containing functional groups on the surface of low-rank coal based activated carbon,therein,the carbonyl and phenolic hydroxyl groups（or ethers） are dominant,while the lactones and carboxyl groups are less.