Catalytic pyrolysis of HDPE over WOx/Al2O3: Effect of tungsten content on the acidity and catalytic performance

Abstract

A series of WOx/Al2O3 catalysts with different tungsten contents were prepared by an incipient-wetness impregnation method for use in the pyrolysis of high density polyethylene (HDPE) to liquid oil. Physicochemical properties of the catalysts were investigated by N2 physisorption, field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy analyses. Acid properties of the catalysts were examined by FT-IR analyses of pyridine-adsorbed catalysts and NH3-TPD (temperature programmed desorption) experiments to elucidate the catalytic performance. The catalytic pyrolysis of HDPE was carried out over WOx/Al2O3 catalysts in a batch-type pyrex reactor at atmospheric pressure. It was found that HDPE conversion and oil yield showed volcano-shaped trends with respect to the tungsten content of the WOx/Al2O3 catalysts. Among the catalysts tested, the 6.25 wt% WOx/Al2O3 catalyst with the largest acidity showed the best catalytic performance. A correlation between the catalytic performance (HDPE conversion and oil yield) and acidity showed that the catalytic performance increased with the increasing acidity of the catalyst.