UiO-66-NH2@MnFe2O4 as a novel and retrievable MOF nanocatalyst for biodiesel synthesis from utilized edible oil in a microwave reactor: RSM design and CI engine studies

Abstract

UiO-66-NH2@MnFe2O4 was synthesized and used as a novel nanocatalyst to generate biodiesel from utilized edible oil (UEO) in a microwave reactor. Several analyses were utilized to characterize the catalyst structure, including SEM, EDX, FTIR, Raman, CO2-TPD, TGA, VSM, BET, TEM, and XRD. Central composite design (CCD) was employed for optimizing impressive variables on biodiesel synthesis. The utmost biodiesel yield using UiO-66-NH2@MnFe2O4 under optimal conditions (e.g., nanocatalyst concentration of 2.89%, methanol/UEO proportion of 9.43:1, stirring rate of 833.89 rpm, and microwave time of 6.37 min) was 97.81%, which is a considerable yield. Moreover, the aforementioned nanocatalyst was utilized in 7 reusing cycles with high performance, so that after the 7th cycle, its biodiesel yield was more than 90%, demonstrating the high recyclability of the nanocatalyst. Furthermore, the activation energy (47.32 kJ/mol) and frequency factor (10.2 × 105) demonstrate that the UiO-66-NH2@MnFe2O4 nanocatalyst has sufficient kinetic energy to do the transesterification reaction. Besides, the reaction between alcohol and UEO was endothermic. The influence of adding biodiesel to petrodiesel in various ratios (B0–B20) on a CI diesel engine was investigated, and satisfactory outcomes were attained in terms of emissions (e.g., reducing CO and UHC concentrations) as well as engine performance.