Abstract:

With differential thermal balance, and by taking a comparative study of DTA/TG curves of Phosphoric acid and Zinc chloride, as well as the curves during pyrolysis of wood dust, separated cellulose and separated lignin which have H₃PO₄ and ZnCl 2 added respectively, It found that: H₃PO₄ and ZnCl₂ demonstrate similar DTA/TG curves, also both of these two testing agents function stable. However, at high temperature of evaporation, H₃PO₄'s initial evaporation temperature, final temperature of pyrolysis and the remains are all obviously higher than that of ZnCl₂. For wood dust with the two testing agents, their DTA/TG curves during pyrolysis show similar. At the beginning, they catalyze carbonization and almost finish carbonization at around 200℃. As the temperature goes higher and higher, they enter into main activation duration. At high temperature duration, both of them have evaporation reaction. Besides, there exist differences between them. The suitable activation duration of H₃PO₄-dust is obviously wider than that of ZnCl₂-dust. Meanwhile, the initial evaporation temperature, final temperature of pyrolysis and the remains of the former are higher. All of these approve that the function of H₃PO₄ protection for carbon is stronger than ZnCl₂. For the influences to cellulose pyrolysis, the two testing agents function as the same as to wood dust. Meanwhile, we got that the effects to the cellulose pyrolysis are less different, while those to lignin pyrolysis are more different. H₃PO₄ affect the whole duration of lignin pyrolysis. However, the effect is less than that to cellulose or wood dust. At the beginning of lignin pyrolysis, ZnCl₂ catalyze carbonization reaction, while in medium and later duration little effect is achieved. From the DTA/TG curves and combined with minor carbonization experiment, we got that under this experiment, the best temperature by H₃PO₄ method is about 400℃, and by ZnCl₂ method is about 500℃.

Key words: Activated carbon, Phosphorylation, Zinc chloration, Differential thermal analysis(DTA), Thermogravimetric analysis(TG)