Magnetic induction heating-assisted synthesis of biodiesel using an alumina/iron oxide nanocatalyst

Abstract

While generating biodiesel from vegetable oils presents various advantages over fossil fuels, ongoing actions aim to improve the efficiency of this production process. Emphasis is placed on optimizing experimental conditions, including the catalyst selection, reaction media and the energy source for heating and mixing, thereby revealing existing research gaps in biodiesel production. In this sense, we have designed a magnetic nanocatalyst based on iron oxide nanoparticles (IONPs) of 18 nm in diameter incorporated within an alumina matrix of around 500 nm infused with potassium hydroxide that provides the catalyst's mesoporosity and basicity. Magnetization analyses confirmed the superparamagnetic behaviour of the nanocatalyst at room temperature and a saturation magnetisation high enough to ease magnetic recovery for reuse. Additionally, magnetic nanoparticles can serve as nanoheaters when subjected to an alternating magnetic field. The heating efficiency of the isolated IONPs was assessed under various frequency and field conditions, yielding specific absorption rate values of up to 80 W/g. Such heating capacity has allowed the synthesis of fatty acid methyl ester (FAMEs), which constitute the biodiesel at 65 °C under optimal field conditions (100 kHz and 48 kA/m) and ideal reaction parameters: 5 % catalyst, methanol/oil ratio 12:1 and 6 h of reaction, with a conversion of up to 98.6 % determined through NMR characterization of the FAMEs and a 95.6 % yield. FAMEs presence was confirmed by optimizing a swift and efficient FTIR method and their purity by TLC. Overall, the designed nanocatalyst presented for FAME synthesis, which incorporates magnetic separability and effective heating capabilities, holds great promise for cost reduction and process efficiency.