Repeated heating of fat oil may result in the formation of highly toxic aldehyde compounds. The oils having such compounds are considered as health hazards and therefore their repeated use is banned in many countries. Since huge quantities of the used oil need urgent disposal, this work is focused on the disposal of used oil for the resource recovery. The waste fat oil was converted into useful fuel through catalytic and non-catalytic pyrolysis. The catalyst was used to lower the oxygen content and to increase the amount of the hydrocarbons in the oil product. The pyrolysis reaction was catalyzed by three catalysts of the clinker type, namely ordinary Portland cement, white cement and burnt clay/clinker powder. The pyrolysis reactions were performed using a custom-made furnace and stainless steel pyrolyzer. Optimum temperature, time and catalyst quantity were identified for high liquid and gaseous fractions and low solid residue. The oil obtained during each reaction was characterized for chemical composition by using GC-MS technique. The oil product of simple pyrolysis, cement catalyzed, white cement catalyzed and clinker catalyzed pyrolysis had the hydrocarbon contents of 3, 19, 51 and 93, respectively. © 2019 Assoc. Brasiliera de Eng. Quimica / Braz. Soc. Chem. Eng.. All rights reserved.