Production of valuable chemicals through the catalytic pyrolysis of harmful oil sludge over metal-loaded HZSM-5 catalysts

This research studied the catalytic pyrolysis of oil sludge (OS) over metal-loaded HZSM-5 catalysts, an eco-friendly and cost-effective technology to produce value-added aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEXs). In particular, it evaluated the respective effects of the experimental parameters: the type and amount of the metal loaded, the reaction temperature, and the OS/catalyst ratio, on the BTEXs yield sequentially to achieve optimum conditions. This evaluation showed that the highest yields of the BTEXs (6.61 wt%) and other aromatics were achieved when Ni was incorporated into the HZSM-5 (Ni/HZSM-5) followed by the corresponding yields of Ga/HZSM-5 and Fe/HZSM-5, due to a better distribution of Ni on the support surface and an enhanced acidity strength of this catalyst. Further, increase in Ni loading (up to 10 wt% Ni/HZSM-5) increased the BTEXs yield to 13.48 wt%. However, the excessive Ni loading (15 wt% Ni/HZSM-5) resulted in a reduced BTEXs yield due to the blockage of the zeolite channels. Next, an increase in the reaction temperature from 500 °C to 600 °C increased the yield of the BTEXs and other aromatics. However, a further increase in the reaction temperature to 650 °C decreased slightly their yield because of the stimulating secondary reactions at high temperatures. The increase of catalyst amount (OS/catalyst of 1/3) also maximized the BTEXs yield (30.50 wt%).