Catalyst waste from the residue fluid catalytic cracking (RFCC) plant process can still be utilized to catalyze the catalytic cracking of palm oil to fuels. However, we should regenerate the active sites of the catalyst waste. This paper focuses on enhancement of Brønsted and Lewis acid sites on the spent RFCC catalyst waste through various acid treatments in order to regenerate its catalyst active sites. In order to regenerate the Brønsted and the Lewis acid sites as active sites in the palm oil catalytic cracking, the spent RFCC catalyst was treated by citric acid, sulfuric acid, and mixture of both acids. The catalysts were characterized by X-ray fluorescence, X-ray diffraction, Brunauer–Emmett–Teller-Barrett–Joyner–Halenda, and pyridine-FTIR analysis. The modified catalyst performance was tested over a fixed bed reactor for the catalytic cracking process of palm oil to liquid fuels. It was found that the acid treatment on the spent RFCC catalyst can increase surface area, pore volume, and Brønsted to Lewis acid site ratio of catalysts. The Brønsted acid sites of the spent RFCC catalyst strongly increase by the treatment using sulfuric acid, which is because of the proton transfer from acid to catalyst and because of the formation of sulfate groups (HOSO3−) in the catalysts. It was found that the Brønsted acid site leads to the formation of long-chain hydrocarbon, while the Lewis acid site pronounces the formation of short-chain hydrocarbon and coke. Moreover, the total acidity and the Lewis acid site amount on the catalyst have roles in the formation of hydrocarbon fraction in the liquid product.

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