Evaluation of activation, performance and reusability between eggshell-derived heterogenous and homogenous catalysts for neem oil biodiesel

• Waste eggshells are utilized to prepare heterogenous catalysts of CaO and CaO-SiO 2 • Heterogenous and conventional homogenous catalysts are compared for the neem oil biodiesel • Ultrasonic activation has enhanced catalytic activity and biodiesel conversion efficiency • Catalyst of CaO-SiO 2 exhibits stable performance relative to CaO after reuse of three cycles • SiO 2 has reduced leaching of Ca ion from CaO catalyst and improved biodiesel yield This research investigates the catalytic efficacy between two homogeneous and two heterogeneous catalysts for biodiesel production from neem oil. Eggshell-derived heterogeneous catalysts of CaO and a mixed CaO-SiO 2 are compared to traditional homogeneous catalysts of NaOH and KOH, The CaO catalyst is obtained by calcining chicken eggshells at 900°C for 3 hours and the CaO-SiO 2 catalyst is prepared by combining CaO and SiO 2 in a 2:1 ratio in methanol prior to transesterification. Reaction parameters are varied for a methanol to oil molar ratio of 9:1 to 20:1, catalyst concentration from 1% to 3%, temperature form 60°C to 65°C, and time from 60 to 120 minutes. The yield of biodiesel with the increase in reaction parameters for homogeneous catalysts declines from 74.63 % to 22.65 % for KOH and from 70.87 % to 28.69 % for NaOH, whereas, for heterogeneous catalysts increases from 37.50 % to 73.24 % for CaO and from 44.37 % to 91.13 % for CaO-SiO 2 . The incorporation of SiO 2 serves as a barrier on the catalyst surface to reduce leaching of Ca 2+ by 23% compare to CaO catalyst and enhances biodiesel yield to 91.13%. Ultrasonication before transesterification has been found as a vital activation step that significantly enhance the catalytic activity relative to conventional stirring methods. CaO retains catalytic activity for two months with only 1.71% decline in yield and CaO-SiO 2 exhibits superior reusability with yields decreasing from 83.03% to 69.04% after three cycles. Findings indicate that eggshell-derived heterogeneous catalysts are cost-effective and sustainable for the production of neem oil biodiesel having properties similar to ASTM D 6751.