Conversion of Used Cooking Oil into Biodiesel by Utilizing Zirconia Catalyst as Acid Catalyst (SO₄/ZrO₂) and Base Catalyst (ZrO₂/CaO)

Zirconium (ZrO₂) was synthesized from Zirconium Oxychloride (ZrOCl₂.8H₂O) using hydrothermal method. Modification of ZrO₂ as an acid catalyst (SO₄/ZrO₂) was made by adding 0.5; 1; and 1.5 M sulfuric acid solutions to ZrO₂. The sulfation process was confirmed by formation of SO₄²⁻ ion spectrum in 1238–1001 cm⁻¹ region and resulted presence of elemental sulfur with mass percentage of 1.36%. The catalyst acidity test showed 1.5 M SO₄/ZrO₂ catalyst as catalyst with the highest acidity value. The application of 1.5 M SO₄/ZrO₂ catalyst in the esterification reaction of used cooking oil resulted decreasing of free fatty acid content up to 55.33%. In the another, preparation of basic catalyst, ZrO₂/CaO was carried out by the addition of Calcium oxide (CaO) to ZrO₂ in three concentrations group of 25, 30, and 35%. The results, we found the catalyst with optimal basicity value in group 30% ZrO₂/CaO. In addition, the 30% ZrO₂/CaO catalyst has CaZrO₃ and lime-CaO crystal phases; exfoliated surface morphology and result Zirconium and Calcium of 7.41 and 42.83%, respectively. Furthermore, biodiesel production from used cooking oil using 30% ZrO₂/CaO catalyst produces biodiesel with good conversion percentage of 94.00%.