不同热解温度制备的烟秆生物炭理化特征分析

分别对100 ~ 800 ℃下于马弗炉中低氧炭化制备的烟秆生物炭进行研究，分析其基础理化性质的变化。结果表明，烟草秸秆生物炭微量元素含量在热解温度为100 ~ 400 ℃时呈逐渐上升的趋势，在400 ~ 500 ℃时较为稳定；大量元素含量增加；C含量和N元素含量在100 ~ 300 ℃时逐渐增加，在400 ~ 800 ℃时先增加后下降，C/N在300 ~ 500 ℃时较为稳定。随着热解温度的升高，烟草秸秆生物炭表面水分子、甲基和亚甲基等官能团减少，C＝C含量逐渐增多；烟草秸秆生物炭的BET比表面积、孔径、比孔容均在400 ~ 500 ℃时较大。烟草秸秆生物炭的中孔较多，孔隙内部特征多为墨水瓶状孔。热解温度为400 ~ 500 ℃时，烟杆生物炭大量和微量元素含量相对较高，C/N较为稳定，孔隙结构最为复杂。

Physico-chemical Characteristics of Biochars Prepared by Pyrolysis of Tobacco-stalk under Different Temperatures

The tobacco stalk was carbonized under different temperatures from 100 ℃ to 800 ℃, and then the basic physical and chemical properties of biochars were measured. The results showed that the mineral micro-element contents of tobacco-stalk biochar were increased with the increase of pyrolysis temperature at 100-400 ℃ and kept relatively stable at 400-500 ℃. Mineral macro-element contents were showed overall an increased trend with the pyrolysis temperature rise. The contents of carbon (C) and nitrogen (N) were increased gradually from 100 ℃ to 300 ℃ and then were declined from 400 ℃ to 800 ℃, and the C/N ratio was relatively stable at 300-500 ℃. With the increase of pyrolysis temperature, surface functional groups of tobacco-stalk biochar get condensed and its aromatization degree was heightened. With the pyrolysis temperature rise, the porosity of tobacco-stalk biochar was increased first and then decreased. The BET specific surface area, pore size and pore volume of tobacco-stalk biochar were the highest at 400-500 ℃. The mesopores were the main type of pores in tobacco-stalk biochar and mainly consisted of ink-bottle-like pores. The tobacco-stalk-biochar had higher macro- and micro elements, stable C/N, and complex pore structure at 400-500 ℃.