A huge amount of spent oils is produced in the world every day. These oils contain some toxic aldehydes, which affect human health. The disposal of used oils in sewers and drains not only raises the blockage and aesthetic problems but also pollutes the water resources. In the present work, spent fat oil (SFO) was converted into a combustible liquid and gaseous fuels by using a batch type reactor. For catalytic pyrolysis, the Portland cement raw mix, white cement raw mix, and powdered nonbrick or clay catalysts were used to convert SFO into useful fuels. The uncatalyzed pyrolysis took 60 min to convert SFO into liquid and gaseous fuels. The pyrolysis time was reduced to 30 min after catalyzing the reaction with a suitable catalyst. The white cement raw mix and clay catalysts promoted the formation of gaseous products, whereas the Portland cement raw mix promoted the formation of liquid fuel. The uncatalyzed pyrolysis of SFO produced only 3.527 hydrocarbons. Among the catalyzed reactions, the highest percentage of hydrocarbons (67.884) was obtained with clay catalyst followed by the white cement (55.24) and Portland cement (35.893) formulations. The uncatalyzed reaction mainly produced fatty acids, the Portland cement and clay/burnt brick catalyzed reactions produced only esters, and the white cement catalyzed reaction produced a single fatty acid. © 2019 Author(s).