STUDY ON THE CONCENTRATION EFFECT OF Nb2O5-ZAA CATALYST TOWARDS TOTAL CONVERSION OF BIODIESEL IN TRANSESTERIFICATION OF WASTED COOKING OIL

Abstract

Study on the concentration effect of Nb₂O₅-ZAAcatalyst towards total conversion of biodiesel has been conducted. The natural zeolite (ZA) was activated by dipping in NH₄Cl solution and was calcined using N₂ atmosphere at 500 °C for 5h to produce the ZAA sample. The Nb₂O₅-ZAA catalyst was made by mixing the activated natural zeolite (ZAA), Nb₂O₅ 3 % (w/w) and oxalic acid 10 % (w/w) solution, until the paste was formed, followed by drying and calcining the catalyst for 3 h at 500 °C under N₂ atmosphere. Catalyst characterizations were conducted by measuring acidity with NH₃ gas using gravimetric method and porosimetric analysis using N₂ gas adsorption based on the BET equation by surface area analyzer instrument. The Nb₂O₅-ZAA catalyst was then used as an acid catalyst in free fatty acid esterification reaction of wasted cooking oil in methanol medium with variation of catalyst concentration: 1.25%; 2.5%; 3.75% and 5% towards the weight of oil+methanol. The reaction was continued by transesterification of triglyceride in the used cooking oil using NaOH catalyst in methanol medium. For comparison, the esterification reaction using H₂SO₄ catalyst 1.25% towards the weight of oil+methanol has been conducted as well. Methyl ester (biodiesel) product was analyzed using Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GC-MS). The characters of biodiesel were analyzed using American Society for Testing and Materials (ASTM) method. The results showed that modification of ZAA by impregning Nb₂O₅ 3% (w/w) increased the total catalyst acidity from 5.00 mmol/g to 5.65 mmol/g. The Nb₂O₅-ZAA catalyst has specific surface area of 60.61 m²/g, total pore volume of 37.62x10^-3 cc/g and average pore radius of 12.41 Å. The Nb₂O₅-ZAAcatalyst with concentration of 1.25%-5% produced higher total conversion of biodiesel than that of H₂SO₄ catalyst 1.25%. The Nb₂O₅-ZAA catalyst with concentration of 3.75% produced the highest total conversion of biodiesel, i.e. 76.76 %. Based on the ASTM data analysis, the product has a qualification as diesel fuel.