Exploring the effects of different parameters on the incorporation of K+ ions in eggshell derived CaO reveals highly variable catalytic efficiency for biodiesel conversion

Abstract

This study was designed to observe the effects of temperature, impregnation time, and stirring rate on the structure of potassium ion-impregnated calcium oxide prepared from potassium hydroxide and waste eggshell-derived calcium oxide. A total of 18 reactions were carried out in different environments to impregnate K+. The catalyst products were analyzed using Infrared spectroscopy (IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), and Energy dispersive X-ray spectroscopy (EDX). The XRD and EDX results indicated that at higher temperatures calcium hydroxide tends to form as well a greater incorporation of K+ ions is achieved. Moreover, stirring speed was observed to affect the growth of specific phases in both calcium oxide and calcium hydroxide crystals. However, the impregnation time variation did not show any significant effect. The prepared catalysts were applied to the transesterification reaction using waste cooking oil as the fatty acid methyl ester (FAME) source, achieving a maximum of 98.28 % conversion to FAME calculated from 1H-NMR spectra. This indicates that tailoring of the catalyst may be carried out by changing these parameters in order to achieve a desired catalyst or sorbent structure which in turn may significantly improve catalytic efficiency.

Keywords

• Calcium oxide
• Impregnation parameters
• Temperature
• Stirring speed
• Surface characteristics
• High yield FAME conversion