CATALYTIC PYROLYSIS OF HIGH-DENSITY POLYETHYLENE WASTE: PHASE DISTRIBUTION OF PRODUCTS AND CHEMICAL COMPOSITION

The dynamics of global plastic production reflects the growing needs of society for this material. However, the increase in production volumes creates the problem of increasing plastic waste, which in the form of microplastics enters the environment. Therefore, research aimed at the recycling of such waste with the priority use of recycling products as valuable secondary raw materials is relevant. The aim of this research is to study the catalytic pyrolysis of high-density polyethylene waste, taking into account the possibilities of increasing the efficiency of the process and obtaining alternative energy sources. The study was conducted in two stages. At the first stage, catalysts were prepared (Fe₂O₃, Fe₃O₄, Ni/MgO, Ni/CaO, zeolite Y in hydrogen form, ascarite). At the second stage, the pyrolysis process was implemented in a laboratory pyrolysis reactor with a temperature sensor and a laboratory autotransformer. The gas phase was investigated using a chromatographic analysis method, which confirmed the high sensitivity of the composition of the gaseous product to the type of catalyst. The analysis of the distribution of pyrolysis products by phase composition (gas, liquid, solid residue) and gas chromatographic analysis of the gas phase composition made it possible to assess the qualitative and quantitative characteristics of each fraction. It was found that the yield of the main products, in particular pyrolysis liquid (within 63–71%), gases (12–21%) and solid residue (11–21%), is in good agreement with existing data reflecting the conditions of slow pyrolysis of polyethylene in the presence of solid catalysts. This gives grounds to argue that catalytic pyrolysis can be considered as a promising alternative for the processing of polymer waste. This will allow obtaining valuable gaseous, liquid and solid hydrocarbon products suitable for further energy or technological use.