Thermal pyrolysis of polyolefins in a two-step process: Role of secondary reactions

Thermal cracking of HDPE has been investigated in a two-step process. The primary pyrolysis takes place in the first reactor while the second reactor allows vapor phase secondary reactions to take place. The effect of residence time (RT) and temperature in the secondary reactor on the liquid product (LP) profile has been elucidated. The change in RT does not significantly alter the B.P. distribution of the LP; however, an increase in the RT leads to a reduction in the total olefinic content but with a simultaneous increase in the percentage of lower olefins (C6-C8). An increase in temperature from 350 to 450 degrees C results in the shifting of carbon number distribution to lower values along with an increase in total olefinic content. Thus the second reactor conditions, in a two-step process, plays a major in controlling the LP profile and a suitable choice of the same can help in obtaining desirable products.