Microwave-assisted biodiesel production using ZIF-8 MOF-derived nanocatalyst: A process optimization, kinetics, thermodynamics and life cycle cost analysis

Abstract

In this study a novel, high surface area, and recyclable nano-size solid basic catalyst is developed for the first time from ZIF-8 MOF-derived CaO/ZnO for the high-yielding transesterification of soybean oil (SO) to biodiesel with methanol under microwave irradiation. The chemical composition, texture and morphology of the catalyst were comprehensively characterized by FT-IR, SEM-EDS, XRD, TGA, XPS and BET. In addition, 1H NMR analyses were performed to confirm the conversion of soybean oil to biodiesel, whereas, GC–MS spectrum provide information about the chemical composition of the produced biodiesel. Kinetic studies are performed for the optimized catalyst and it follows the pseudo-first-order reaction. Thermodynamic analyses show that the transesterification of soybean oil to biodiesel reaction is endothermic and not spontaneous. By using Response surface methodology (RSM), the optimization of parameters that affect the biodiesel yield is studied. The transformation of 1:20 soybean oil with methanol using CaO/ZnO catalyst (7 wt%) gives 97.4 % biodiesel yield for the transesterification at 90 °C for 50 min. The catalyst shows good reusability after 5 successive cycles demonstrating its industrial-scale applications. According to Life cycle cost analysis (LCCA) the estimated price of 1 kg of biodiesel produced in this work is merely $1.11 showing high commercial applicability.