Improving bio-oil quality from durian husk pyrolysis: optimization of esterification process using K2CO3/talc catalyst for sustainable biofuel production

Abstract

This study focuses on optimizing the ratio of bio-oil:methanol to improve the quality of fuel obtained from durian husk pyrolysis through an esterification process assisted by a K₂CO₃/talc catalyst. This study involved several stages, starting with the pyrolysis of durian husk biomass without the aid of a catalyst (350–500 °C), the distillation process (70–150 °C), and the esterification process using the reflux method at a temperature of 75 °C. This study explored different ratios of bio-oil:methanol (1:8, 1:10, and 1:12) and found that the highest esterification yield was at a ratio of 1:8, reaching 72.22 ± 1.11%. Higher methanol ratios decreased the esterification yield, possibly due to reaction inefficiency. The esterification process demonstrated the success of K₂CO₃/talc as a catalyst, producing components such as methyl acetate, methyl ethyl ketone, and methyl 2-methylbutyrate found in esterified bio-oil. The physicochemical properties of bio-oil, including water content, pH, density, viscosity, specific gravity, API specific gravity, and calorific value, were significantly improved through esterification. The water content decreased from 4.76% in crude bio-oil to 3.38% after esterification, while the density decreased from 1.01 to 0.77 g/cm³, and the viscosity decreased from 2.68 to 0.51 cSt. The calorific value increased from 43.27 to 47.26 MJ/kg. These improvements indicate that esterification substantially improves bio-oil quality, making it a more viable and efficient renewable fuel source.