Influence of the temperature on the composition of the coke obtained in the catalytic cracking of low density polyethylene in the presence of USY and HZSM-5 zeolites

In this work, the influence of the temperature on the nature of the coke obtained in the cracking of LDPE (Low Density Polyethylene) in the presence of HZSM-5 and USY zeolites is studied. The polyaromatic nature of the coke increases for both zeolites studied, as the temperature increases. The comparison between the soluble and insoluble content of the coke formed in the presence of USY and HZSM-5 zeolites reflects the different composition of the coke produced in both zeolites. GC–MS analysis of the soluble coke obtained at high temperature has revealed the cracking of certain coke molecules, especially in the case of HZSM-5. In these cases, a drastic change in the soluble coke composition in comparison with the samples obtained at lower temperature has been observed. For the higher temperature coked HZSM-5 samples, the soluble coke is mainly composed of naphthalene derivate compounds. This work has permitted study the effect of the final cracking temperature on the coke nature of two different zeolites during the pyrolysis of a polymer, a study that, to our knowledge, has never been reported.