DOI: https://doi.org/10.55373/mjchem.v25i3.331

Keywords: Calcium oxide; waste oyster; transesterification; glycerol carbonate

Abstract

Glycerol, the main by-product of biodiesel production, has experienced saturation in the market, hence affecting the biodiesel industry. Conversion of glycerol into value-added products, such as glycerol carbonate (GC), should be implemented to overcome this issue. Besides, the use of heterogeneous catalysts obtained from waste can reduce the cost and impact on the environment. Although basic homogeneous catalysts show high catalytic activity, they are hard to separate and unrecoverable. Hence, calcium oxide (CaO) was used as the catalyst in this research. The CaO catalyst derived from waste oyster shells (CaO-WOS) was prepared through calcination at 950 ℃ for 3 h, and TGA, BET, FTIR, XRD, and SEM were conducted for the characterisation of the catalyst. In this study, CaO-WOS and commercial CaO were used as the catalysts for synthesising GC through the transesterification of glycerol and dimethyl carbonate (DMC). The reaction was conducted under identical conditions (DMC-to-glycerol molar ratio of 2.5:1, reaction temperature of 40–60 ℃, reaction time of 3 h, and catalyst loading of 4% molar ratio of the initial amount of glycerol). The crystallinity of both catalysts is identical as similar peaks appeared. The XRD and FTIR results confirmed the presence of CaO in the catalyst. The catalytic activity was compared by analysing the 1H NMR spectra of the GC produced to obtain the predicted percentage molar concentration of GC. The predicted molar concentrations of GC for the transesterification conducted using commercial CaO and CaO-WOS are 97.0% and 72.5%, respectively. Hence, CaO-WOS is a good potential catalyst in the transesterification of glycerol into GC.