煤焦油渣炭化过程中孔结构及表面分形特征

Structure and surface fractal characteristics of coal tar residue during carbonization

利用煤气化焦油渣为原料进行活性炭制备实验研究,对炭化过程焦油渣孔结构和表面特征进行研究,采用N2吸附/脱附等温实验和表面分形理论研究炭化对焦油渣孔结构和表面特征的影响。结果表明:炭化物的吸附等温线倾向于表征微孔吸附特征的Ⅰ类吸附等温线;炭化物中具有发达的微孔结构、过渡孔结构和极不发达的大孔结构;随着温度和升温速率的提高,微孔结构先增加后又逐渐发展为过渡孔和大孔;对炭化物表面的分形特征进行研究发现,表面分形维数与BET比表面积、总孔容、平均孔径不存在直接关系,但是与微孔面积占比和微孔容积占比存在较好的一致性;焦油渣在炭化处理过程中随着温度的升高和升温速率加快,经历了“立体发展-逐渐衰落”的过程。当炭化终温850℃、升温速率20℃/min时,可以得到最优的活化前体。

During the preparation of activated carbon from tar residue,the influence of carbonization process on the pore structure and the surface characteristics of tar residue was studied by isothermal N2 adsorption/desorption experiment and surface fractal theory.Results indicated that the adsorption isotherms were close to the type I which represented the microporous adsorption characteristics and indicated that the carbonized products had sub-microporous structure,transition pore structure and extremely undeveloped macroporous structure at the same time.With the increase of temperature and heating rate,the microporous structure increased at first and then gradually developed into transition pore and macropore.It was found that fractal dimension had no direct relationship to the BET specific surface area,total pore volume and average pore diameter.However,there was a good consistence between the proportion of the microporous area and that of the microporous volume.During the pre-carbonization treatment process,the tar residue experienced a process of“three dimensional development-gradual decline”.The optimal activated raw material can be obtained,when the final temperature of the pre-carbonization was 850℃and the heating rate was 20℃/min.