Pyrolysis and in Line Oxidative Steam Reforming of Hdpe

The environmental concern associated with waste plastics is growing due to the persistent impact of plastics on oceans, freshwater and terrestrial environments. Within this scenario, the development of feasible processes for waste plastic management is an urgent matter to which increasing attention has been paid in recent years. Thermochemical conversion technologies for plastics are promising alternatives, as they allow producing fuel and high value-added chemicals. Recently, the combination of pyrolysis and in line steam reforming was proposed as a new strategy for the selective H₂ production.

Pyrolysis and in line oxidative steam reforming for H₂ production from high density polyethylene (HDPE) was carried out in a conical spouted bed reactor (CSBR) and a fluidized bed reactor (FBR). Operating under oxidative conditions can reduce or even avoid the energy requirements of the endothermic reactions of the reforming stage, as well as contribute to the in situ combustion of the coke deposited on the catalyst, and therefore improve its stability.

A parametric study was carried out in a wide range of operating conditions: reforming temperature (550, 600, 650, 700, 750 °C); the steam/plastic ratio (S/P) (2, 3, 4, 5) and the equivalence ratio (ER, ratio between the oxygen introduced in the reforming and that required for complete combustion) (0, 0.1, 0.2, 0.3).

In general, the S/P ratio is the most influential parameter on H₂ production, followed by ER and temperature. Thus, H₂ yields of around 24 wt% are obtained with S/P values of 2 and 3; H₂ yields of around 28 wt% with ER between 0 and 0.1 and 24 wt% with ER between 0.2 and 0.3; and H₂ yields of 18-23 wt% when the reforming temperature is between 550-650 ºC and around 25 wt% when it is between 700-750 ºC.