Generation of biodiesel from edible waste oil using ZIF-67-KOH modified Luffa cylindrica biomass catalyst

Abstract

To produce biodiesel from edible waste oil, a new heterogeneous catalyst based on Luffa cylindrica biomass was used. For this purpose, first, Luffa cylindrica carbon was modified using zeolite imidazole metal-organic framework (ZIF-67) and KOH and used in the biodiesel production. Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Powder Diffraction (XRD), Brunauer–Emmett–Teller (BET), Transmission Electron Microscopy (TEM), Raman, and Thermogravimetric Analysis (TGA) techniques were used to investigate the properties of the synthesized catalyst. BET values for activated carbon of Luffa cylindrica (ACL), ZIF-67, ACL/ZIF-67, and ACL/ZIF-67/KOH samples were determined to be 99.714, 1695.7, 956.99, and 2.322 m2/g, respectively, indicating that modification of biomass using ZIF-67 improved its specific active surface, which can retain more KOH in the pores of catalyst. To evaluate the ability of the synthesized catalyst, the effect of various parameters such as reaction time, temperature, amount of catalyst, the molar ratio of oil to methanol, and mixing speed were investigated. The results showed good catalytic activity in converting edible waste oil to biodiesel and maximum efficiency of biodiesel production (98.31%) in laboratory conditions such as a temperature of 65 °C, a catalyst concentration of 3 wt%, a reaction time 3 h, a methanol: oil ratio of 15:1 and a mixing speed of 600 rpm. After determining the optimal laboratory conditions, the study of regeneration and reuse of the catalyst showed that the catalyst had a suitable catalytic activity and can use more than 4 steps in the biodiesel production process. The properties of biodiesel obtained under optimal conditions were evaluated according to the international standards (ASTM D6751 and EN-14214). The results showed that the produced biodiesel possess suitable properties and can replace fuels derived from fossil fuels.