Catalysed biodiesel synthesis from non-edible Nagkesar and Rubber seed oil blends using C1-C3 alcohol mixtures: Process optimization, kinetics and thermodynamics

Abstract

Biodiesel has gained worldwide attention due to an impending energy crisis, while a food-vs-fuel dispute prevents edible oils from usage in fuel synthesis. Therefore, blends of nagkesar (MFL) oil and rubber seed (RS) oil were studied for their two-step heterogeneous (doped MFL seed shell char) catalysed conversion into biodiesel. 96.87 % FFA conversion occurred from 2:3 MFL-RS ratio at 55 °C with 3%w/w H2SO4-doped catalyst using 50%w/w methanol under 850 rpm within 2 h. 98.97 % biodiesel yield was noted using 2:3 methanol to 2-propanol ratio at 60 °C with 4.5%w/w KOH-doped catalyst under 900 rpm within 2 h. From kinetics study revealed that FFA pre-treatment shows Ea of 3.26 kJ/mol and A = 2.52 min−1; base catalysed conversion shows Ea of 1.27 kJ/mol and A = 3.26 min−1. Thermodynamics study confirms non-spontaneity of processes, FFA pre-treatment being endothermic and final conversion being exothermic. Catalyst reuse showed that KOH-doped catalyst was more reusable than sulfonated catalyst.