Comparative study of bio-oils generated at different temperature ranges from pyrolysis of waste cooking oil

Abstract

The study investigated the catalytic pyrolysis of waste frying oil using zeolite A + sodalite (0–20%) at 400 °C and 500 °C, aiming to optimize bio-oil production. Thermal monitoring revealed a linear variation in temperatures within the reactor and at the top, with a transition between the initial phase and the abrupt activation of pyrolysis. Liquid yields ranged from 33.71% (without catalyst, 400 °C) to 94.21% (10% zeolite, 500 °C), demonstrating the significant influence of both temperature and catalyst load on the process. Physicochemical analyses showed that the bio-oil produced with 5% zeolite at 500 °C exhibited the lowest acidity index (100.9 mg KOH/g), although still above the ANP standard, and FT-IR spectroscopy confirmed the reduction of O-H and C=O groups, indicating efficient oxygen removal. Additionally, this bio-oil was characterized by a high fraction of hydrocarbons (61.5%) and a reduction of carboxylic acids to 6.45%, evidencing catalytic deoxygenation via decarboxylation, in contrast to the 54.78% hydrocarbons and 20.25% carboxylic acids obtained with 10% catalyst at 400 °C, which suggests active site saturation. Thus, the use of 5% zeolite at 500 °C yields the best quality bio-oil, representing the optimal condition for waste valorization, while the application of 10% zeolite at this temperature maximizes the liquid yield, reinforcing the sustainable potential of catalytic pyrolysis.