Catalytic cracking of HDPE over hybrid zeolitic-mesoporous materials

The potential application of hybrid ZSM-5/MCM-41 materials for the catalytic degradation of high-density polyethylene (HDPE) has been investigated and compared with the behavior of standard Al-MCM-41 and HZSM-5 samples. Hybrid zeolitic-mesoporous materials were prepared from zeolite seeds obtained in different stages of ZSM-5 crystallization by variation of the synthesis time. The seeds were assembled around cetyltrimethyl ammonium bromide (CTAB) micelles to obtain hybrid materials having a combination of both zeolitic and mesostructured features. The samples so obtained have exhibited remarkable catalytic activity in the HDPE cracking despite the low temperatures (380 °C) and catalyst loadings used (plastic/catalyst mass ratio = 100), leading to polyolefin conversions higher than both Al-MCM-41 and HZSM-5. The product distribution observed with the hybrid materials are closer to that obtained in the HDPE cracking over HZSM-5 zeolite, with a high proportion of light hydrocarbons. Moreover, the products present a high content of C3-C5 olefins, which is an interesting result regarding its possible use as raw chemicals. Increasing the zeolitic crystallinity of the hybrid materials causes an enhancement in the production of heavier products with boiling points within the gasoline range and a higher content of aromatic hydrocarbons.