Hydrogen rich products from waste HDPE/LDPE/PP/PET over Me/Ni-ZSM-5 catalysts combined with dolomite

Abstract

This work focuses on the pyrolysis-gasification of real waste polymers in one stage tubular reactor with and without catalyst at 550 °C and 850 °C. Moreover, the possibility for dry reforming by in situ CO2 generation was also investigated using dolomite. To enhance the syngas production from waste plastics, Ni/ZSM-5 catalyst was synthetized by wet impregnation with 4.82% of Ni, then the catalyst was loaded by further elements in ~2% concentration (Ca, Ce, La, Mg, and Mn). The composition of gases and liquid products was measured by gas-chromatography, while the coke deposition on the spent catalysts was followed by temperature-programmed oxidation. It was found that a large amount of amorphous carbons was produced at 550 °C with Ni/ZSM-5 catalyst. The in-situ addition of the carbon-dioxide can enhance the production of syngas because both the hydrogen and carbon-monoxide concentration can drastically increase. Furthermore, the carbon deposition on the catalyst surface can be reduced by using dolomite. Based on the results of the various Me/Ni/ZSM-5 catalysts, the Ce/Ni/ZSM-5 was the most promising catalyst for the production of syngas (122.6 mmol/g at 850 °C). While, Mg/Ni/ZSM-5 showed less effect on the decomposition reaction, as low syngas yield was produced (62.8 mmol/g at 850 °C). The maximum yield of pyrolysis oil was achieved at 550 °C for the process without the catalyst.

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