Fig. 5 and Fig. 6 show the changes in the total Raman areas between 800 and 1800 cm−1 and the band area ratio of I(Gr+Vl+Vr) to ID as a function of holding time during the fast pyrolysis/gasification of Collie coal. In Fig. 5, similar to Loy Yang coal, Collie coal also showed a generally higher total Raman area during the gasification in CO2 than the pyrolysis in He. It indicates the formation of O-containing functional groups during holding in CO2 at 1000 and 1200 °C. However, at 1000 °C, the increase in total Raman area for Collie coal was from ∼450 (in He) to ∼900 (in CO2), which was much less than that BAY 80-6946 for Loy Yang coal from ∼450 (in He) to ∼1650 (in CO2). The difference can be mainly due to the relatively slow gasification rate at 1000 °C for Collie coal, which formed less O-containing functional groups with the same holding time . When the temperature was increased to 1200 °C in CO2, the total Raman area increased rapidly within 2.5 s and then levelled off during further holding from 2.5 to 5 s. It suggests eyespot the rapid formation of O-containing functional groups in CO2 occurs at 1200 °C and reaches a dynamic balance with the breakage of O-containing functional groups during holding from 2.5 to 5 s.