Study of the conversion of low-density polyethylene over Nb2O5/HY composite materials

Abstract

Due to the increase in the production of plastic waste, inadequate disposal and the long period of elimination of polymers, Brazil has been affected by serious environmental impacts. In order to avoid an expansion of the problem, catalytic pyrolysis has become a very attractive process in relation to the chemical treatment of these materials, promoting processes that require lower energy expenditure. Therefore, in this work, heterogeneous composite catalysts based on zeolite Y in acidic form, impregnated with different levels of calcined niobium oxide (10% Nb₂O₅/HY and 20% Nb₂O₅/HY) were developed via mechanosynthesis. The obtained catalysts were characterized by X ray diffraction (XRD) and nitrogen adsorption at 77 K. Through these characterization techniques, it was possible to determine the structural and textural properties of the catalysts and thus be able to correlate them with their catalytic activity. The thermal and catalytic pyrolysis reactions of LDPE were carried out via Thermogravimetry (TG) at different heating rates (5, 10 and 20 ºC.min^-1) using LDPE and LDPE + catalysts mixtures. Conversion data were correlated using the Flynn-Wall-Ozawa (FWO) and Vyazovkin (VZK) kinetic models. It was observed that the catalytic conversion curves presented lower temperature ranges than those proposed by the pure polymer and that the activation energies estimated by the two models were similar showing a good correlation of the data. As observed by the catalytic tests, the results indicated that the production of the Nb₂O₅/HY composite materials can be a good strategy to generate increased catalytic activity in the LDPE conversion process.