Catalytic cracking of HDPE over hybrid zeolitic-mesoporous materials

Abstract

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 a standard Al-MCM-41 sample. 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 ºC) and catalyst loadings used (plastic/catalyst mass ratio =100), leading to polyolefin conversions higher than Al-MCM-41. The product distribution observed with the hybrid materials is closer to that typically obtained in the HDPE cracking over HZSM-5 zeolite, with a high proportion of light hydrocarbons. Moreover, the products present a high content of C2-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.