Magnetic carbon nanotubes doped cadmium oxide as heterogeneous catalyst for biodiesel from waste cooking oil

Abstract

The exploration for innovative heterogeneous catalyst materials bearing unique chemical and physical properties has become a focal point in the field of biodiesel synthesis. In this study, a novel heterogeneous nanocatalyst composed of carbon nanotubes (CNT) coated with magnetic iron oxide and doped with cadmium oxide (CdO) nanoparticles denoted as MCNT@CdO was synthesized. This nanocatalyst was used in the production of biodiesel derived from Waste Cooking Oil (WCO). Several analytical techniques such as field-emission scanning electron microscopy (FESEM) for morphological assessment, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) for structural determination, Energy Dispersive X-ray Spectrometer (EDX) for chemical composition analysis, and vibrating sample magnetometer (VSM) for the evaluation of magnetic properties, were tested. Also, the effects of various parameters such as molar ratios of methanol to oil (1:1, 5:1, 10:1, 20:1, and 30:1), catalyst dosages ranging from 0.01 to 0.2 g, reaction times from 60 to 240 min, and reaction temperatures between 25 °C and 120 °C were studied. Based on the findings, the optimal reaction conditions were at the magnetic Carbon Nanotube (MCNT) to Cadmium Oxide Nanoparticles (CdO NPs) ratio of 1:0.5, a molar ratio of WCO to Methanol of 1:10, a reaction duration of 180 min, and a reaction temperature of 120 °C. Moreover, under the most favorable reaction conditions, the catalyst demonstrated satisfactory catalytic efficiency (> 92%) in transforming the triglycerides of WCO into fatty acid methyl esters (FAMEs) for biodiesel production. Therefore, these innovative heterogeneous composites are proposed as alternative catalysts for future biodiesel generation methodologies.