Highly efficient catalytic degradation of low-density polyethylene Using a novel tungstophosphoric acid/kaolin clay composite catalyst

Abstract

In order to take advantage of the Bronsted acidity of tungstophosphoric acid (TPA) and Lewis acidity of kaolin, TPA-loaded kaolin catalysts with varying percentages of TPA (10-50 wt.-%) were prepared by wet impregnation method. Fourier transform infrared spectrometer, X-ray diffractometer, Brunauer-Emmett-Teller surface area analyzer, and scanning electron microscope characterizations were performed to confirm the successful loading of TPA on kaolin. Catalytic cracking of low-density polyethylene (LDPE), by employing TPA-loaded kaolin as the catalyst, produced a higher percentage of fuel oil (liquid and gaseous hydrocarbons) with a negligible amount of semisolid wax (1.0 wt.-%). The wax amount was significantly lower compared to the thermal cracking, which produced $\sim $22 wt.-% solid black residue. Moreover, GC-MS analysis of oil showed that thermal cracking produced mainly higher hydrocarbons (C$_{22})$ as compared to the catalytic cracking where larger fraction of lower hydrocarbons were obtained. We purpose that the higher performance of prepared catalysts was due to the presence of both Bronsted and Lewis acid sites, which increase their catalytic efficiency and degraded LDPE at the relatively lower temperatures. These results suggest that prepared materials were effective catalysts with low cost and easily scalable production method, suitable for large-scale high performance catalytic cracking of polymers.