Production of hydrogen-rich gaseous product from pyrolysis of polypropylene wastes using bauxite ore catalyst: yield analysis of various products

Abstract

The article investigates the extraction of superior-quality pyrolytic oil (PO) with considerable yield and hydrogen-rich gaseous mixtures from the pyrolysis of polypropylene waste (PPW) with and without a catalyst. Considering the presence of a mixture of metal oxides in low-cost bauxite ore, its catalytic activity towards the quality and quantity of PO and the composition of syngas has been explored experimentally. A positive selectivity towards the reduced temperature (about 10 °C) degradation of PPW with catalysts has been identified during the thermogravimetric (TGA) study. A batch reactor study was conducted with PPW with varied proportions of catalyst, temperatures (525 °C–600 °C), and heating rates (5, 10, and 15 °C/min) to quantify the effects of process conditions on end products’ characteristics and to identify the optimal process parameters. The pyrolysis temperature of 575 °C at 15 °C/min with 10 % catalyst produced the superior quality PO. The corresponding yields of PO and gaseous products were 75.14 % and 17.16 %, respectively. The analysis of PO by FTIR and GC-MS showed higher concentrations of lighter hydrocarbons suitable for gasoline range fuel, namely 2, 4-dimethyl heptane, 2, 6-dimethyl-nonane, and 2, 4-dimethyl-1-heptene, in addition to aromatics. The GC test of gaseous products showed that the presence of bauxite ore significantly enhanced the hydrogen recovery in gaseous products compared to thermal pyrolysis alone. Under optimum conditions, the hydrogen content in the gaseous product reached up to 9.8 %, fulfilling the primary aim of the study. Bauxite ore has a promising catalytic activity, making the process sustainable for hydrogen-rich gaseous products and gasoline range PO from PPW. The study backs circular economy activities by promoting the scientific use of plastic garbage for converting it into value-added clean fuels.