A minimum in the total

A minimum in Purmorphamine total Raman intensity was observed for char produced at 1 s holding at 1000 °C in Fig. 2. For the char produced by pyrolysis at 1000 °C, the total Raman area significantly decreased within 1 s holding, which should be mainly due to the thermal annealing (aromatic ring condensation and loss of O-containing functional groups). Therefore, the minimal total Raman area at 1 s should be mainly attributed to the counteraction of two opposite effects: oxygenation and thermal annealing. As the thermal annealing during pyrolysis is chemical equilibrium almost completed within 1 s, the total Raman area gradually increased from 1 to 3 s in CO2 with the continuous formation of O-containing functional groups at 1000 °C. Very slow increases in total Raman area were observed with further holding from 3 to 10 s in CO2. The nearly constant total Raman area from 3 to 10 s holding in CO2 should be due to the dynamic balance between the thermal cracking and the formation of O-containing functional groups.