Preparation of Na2O supported CNTs nanocatalyst for efficient biodiesel production from waste-oil

Abstract

The present work demonstrated the preparation of sodium oxide impregnated on carbon nanotubes (CNTs) and its application as a heterogeneous catalyst for transesterification of waste cooking oil. The catalyst was prepared by impregnation of metal oxide such as sodium oxide, Na2O on the CNTs by calcination at 500 °C for 3 h. It was assumed that the positive metal ion which is Na+ (cations) possess Lewis acidity, whereby, high negativity of oxygen ions can acts as the Brønsted bases, which could enhance the activity of the catalyst. The characterization of synthesized Na2O impregnated-CNTs nanocatalyst was performed using Temperature-programmed desorption of carbon dioxide (TPD-CO2), X-ray diffraction (XRD), infrared spectroscopy and Field emission scanning electron microscope (FESEM). Herein, the mechanism of the transesterification process assisted by the Lewis acidic metal oxide on carbon support was proposed and explained. Series of reactions were carried out to determine the performance of the catalyst. It was found that the prepared Na2O(20 wt%)/CNTs catalysts yielded above 97% of FAME yield at 65 °C assisted by 3 wt% of catalyst amount and 20:1 of methanol-to-oil molar ratio in 3 h of reaction time. Moreover, the results on catalyst's reusability indicated that the catalyst could last for 3 subsequent reaction cycles due to deactivation of the catalyst caused by leaching of metal oxides and poisioning effect on the active sites. It can be concluded that the prepared Lewis acidic carbon catalyst has a potential to catalyse the production of biodiesel from waste cooking oil (WCO).

Fabrication and Optimization of Nanocatalyst for Biodiesel Production: An Overview

“…While acid catalyzed reactions require high temperature and longer reaction times. It is also proven that triglycerides conversion was maximally achieved by homogenous catalysis owing to good catalytic activity and high reaction rate (Ibrahim et al, 2020). However, it shows serious issues related to separation and purification of catalyst and product.…”

“…The regeneration process is important in retaining the lost sulphonic group during the leaching process . Ibrahim et al (2020) reported the impregnation of sodium oxide over carbon nanotubes for trans-esterification of waste cocking oil. The nanocatalysts have shown excellent catalytic activity due to the presence of sodium ions and oxide ions.…”

“…The cation imparts lewis acidity while the anion acts as a Brønsted base, thus overall enhancing the catalytic activity with biodiesel production of 97%. It is found to be unstable after 3 cycles because of leaching, which causes deactivation of active sites (Ibrahim et al, 2020).…”

“…Involvement of a nanocatalyst also leads to reduction in reaction temperatures, catalyst weight and alcohol to oil ratio. Ibrahim et al (2020) have reported the role and amount of the nanocatalyst in biodiesel production. It was found that nanocatalysts play a prominent role in increasing the rate of reaction without being self-deteriorated.…”

“…It also significantly lowers the activation energy of the reaction profiles. Additionally, the amount of nanocatalyst is also a critical parameter in determining the yield of biodiesel production (Ibrahim et al, 2020). Another researcher has also investigated the role of nanocatalysts especially in biodiesel production.…”