The effect of temperature, catalyst, different carrier gases and stirrer on the produced transportation hydrocarbons of LLDPE degradation in a stirred reactor

The pyrolysis of linear low density polyethylene (LLDPE) by used fluid catalytic cracking (FCC) catalyst was studied in a stirred reactor to reach the appropriate transportation hydrocarbons. In this work, the effect of process parameters such as degradation temperature, catalyst/polymer ratio (%), carrier gas type and stirring rate on the condensed yield, product composition and residence time were considered. Product evaluation was performed by GC analyzer and paraffin, naphthene, olefin and aromatic plus carbon number and average molecular weight of the products were measured under different process parameters.Temperature and catalyst as the basic parameters show remarkable effect on the LLDPE cracking. The maximum transportation condensate yield reaches at 450 °C and 20% catalyst respectively although increase of temperature and catalyst content, decrease the residence time patently. Based on the results, molecular weight and reactivity of the carrier gas as mass transfer factor also play a key role in the process. A decrease in molecular weight of the carrier gas led to increase the condensate yield and decrease the residence time. Meanwhile increasing of the carrier gas reactivity could increase the condensate hydrocarbons. Hydrogen as reactive and lower molecular weight carrier gas increases the condensed yield patently. The study showed that stirring rate as a function of heat transfer and temperature homogenizer also affects on the condensate hydrocarbons positively. The maximum condensate yield was found to occur at 50 rpm although the residence time decreases with stirring rate increasing.

► The effect of different carrier gas such as hydrogen, nitrogen, ethylene, propylene, Argon, helium and the system without carrier gas on the mass transfer has been studied.
► The effect of reactivity and molecular weight of carrier gas on the LLDPE degradation has been studied.
► The effect of agitator speed and the presence of agitator on the degradation and heat transfer have been studied.
► The effect of different process parameters such as temperature, catalyst/polymer ratio and agitator speed and carrier gas on the pyrolysis product quality and quantity have been studied.