Exploring the Morphological Effect of Zeolite Beta on Catalytic Cracking of Polyethylene

Abstract

Two types of zeolite catalysts, namely, nanosized Beta-N and micrometer-sized Beta-M, were used to crack lowdensity polyethylene (LDPE) with three different molecular weights: 4000, 200,000, and 3,000,000. The structural and acidic properties were analyzed by N 2 physisorption, transmission electron microscopy, X-ray diffraction, temperature-programmed desorption of isopropylamine (IPA-TPD), and pyridine-adsorbed FTIR. The catalytic activity was tested at 623 K and 3.5 N 2 MPa in an autoclave batch reactor for PE cracking. High Mw PE required higher decomposition activation energy due to transfer limitation. Beta-N showed better activity in PE cracking than Beta-M, with PE conversion of 82.7 and 62.0% for Beta-N and Beta-M, respectively. In addition, the nanosized Beta-N exhibited quite lower activation energy of catalytic PE decomposition than Beta-M, obtained by the Kissinger method in TGA measurement. The characterization results demonstrated that the Beta-N has abundant interparticulate mesopores to provide better dispersion for the catalysts into PE melt and the proximity of the cracking active sites. These results revealed that the Beta-N catalyst shows superior activity for the cracking of polyolefins.