Abstract

Pyrolysis and hydropyrolysis have emerged as an efficient and sustainable solution for valorizing municipal solid wastes (MSW) into value-added products. However, the effectivity of these thermochemical processes is hindered by low yields, high water content and low calorific value of pyro-oils, thus requiring for catalytic materials. Here, we report on the effectiveness of using natural zeolites and Ni and Cu-doped zeolites to produce fuels via pyrolysis and hydropyrolysis of MSW. A systematic analysis of the temperature effect, Cu-doped and Ni-doped catalysts, MSW-to-catalyst ratio, and reaction atmosphere (He or H2) on the product distribution from pyrolysis and hydropyrolysis was carried out. The chemical composition of pyro-oil precursors was investigated using a micropyrolyzer coupled to a gas chromatograph and mass spectrometer (Py-GC-MS). The most significant parameters for reducing oxygenated compounds in pyro-oil were the reaction atmosphere, temperature, and catalyst type, with the sample-to-catalyst ratio showing no statistically significant effect. Hydropyrolysis at 14 bar and 550 ºC reduced the oxygenated compounds content in pyro-oils by approximately 36 % compared to non-catalytic pyrolysis. Under these reaction conditions, Ni-doped natural zeolite (HZNHZ-Ni15R) led to a sharp increase in hydrocarbon selectivity, reaching a maximum of 88.2 %, while O-containing species were reduced to 5.1 %. The HZNHZ-Ni15R exhibited a high selectivity towards benzene, toluene, ethylbenzene, and xylene via a complex pyrolysis and hydropyrolysis reaction mechanism. In addition, the study proposed and exhaustively discussed the reaction mechanism governing the catalytic pyrolysis and catalytic hydropyrolysis of MSW. © 2024 The Authors