Reaction mechanism of ethylene tar in the air atmosphere

The reaction process of ethylene tar in the air atmosphere is very complex and contains numerous changes, which can be divided into three stages and should be further studied to guide the production of specific pitches. In the first stage, before about 310 °C, hydrogen at the benzylic position is firstly transformed into alcoholic hydroxyl, which is partly oxidized into CO and COOH/C–O–CO afterward. Most side chains except the CO groups are gradually converted into COOH and –CH2-. Continuous dehydrogenation indicates highly condensed structures in the next stage, from 310 °C to around 380 °C. With the deprivation of CO2, further oxidization leads to the form of –CH2–, which becomes the critical linkage to create larger molecules. In the third stage, the weight of the sample is close to zero at about 550 °C. Under the direction of theory, getting pitches with the needed properties may be more accessible.