Abstract:
The ever-increasing population growth and economic developments have led to a
demand for energy. Therefore, this has resulted in a depletion and ever rising prices of
petroleum diesel, hence increasing environmental degradation. These complications
have motivated this study for the search of an alternative eco-friendly and renewable
source of energy such as biodiesel. Biodiesel has been found to be a potential alternative
fuel for diesel. It has the potential to solve the energy crisis depending on the availability
of feedstock and catalyst. In this study, biodiesel was produced by transesterification of
the mongongo (Schinziophyton rautanenii) nut oil in the presence of a heterogeneous
catalyst CaO. CaO is used in this study because it is highly active and is the commonly
used solid catalyst for transesterification reaction. CaO was derived from eggshell ash
and synthesized CaO-nanoparticles. The catalyst from eggshell ash and synthetic CaO nanoparticles were calcined at a temperature of 800 °C and characterized through;
Scanning Electron microscope- Energy Dispersive X-Ray Analyzer (SEM-EDX) where
both catalysts showed agglomerated and porous particles and high elemental
composition of Ca and O. Powder X-ray Diffraction (XRD) showed that CaO was present
in both catalysts and the average crystalline size calculated was 42 and 50 nm for CaO nanoparticles and eggshell ash respectively. Finally, Fourier Transmission-Infrared
(FTIR) spectrometer showed the absorption bands of CaO from both catalysts which were
at 875 and 713 cm-1 for CaO-nanoparticles and eggshell ash respectively.
Schinziophyton rautanenii (mongongo) is a multipurpose plant species in Southern Africa
with an ecosystem that provides a variety of goods and services such as food security,
employment and source of income to people from rural communities in Southern Africa.
The Schinziophyton rautanenii generally contains at least 60% of oil extracted from its nut
which has potential to produce biodiesel. The characterization of mongongo nut oil and
mongongo methyl esters (biodiesel) was done according to the European biodiesel
specification (EN 1421) and American society for testing and material (ASTM D675)
which are the standards set for biodiesel. The measured physicochemical properties of
the biodiesel were in the range of these international standards. The analysis of ii
mongongo methyl ester was through Gas chromatography-mass spectrometry (GC-MS)
and the methyl esters were identified using mass spectrometric libraries. Statistically,
there was no significant difference between CaO-NPs and eggshell (P>0.05). However,
in terms of catalyst loading, the eggshell was a better catalyst as it required a low catalyst
load to obtain an optimum yield of 83% at 6 wt.% compared to CaO-NPs with an optimum
yield of 85% at 12 wt.%. The reactions were all performed at constant reaction conditions
of 9:1 methanol to oil ratio, 3 h reaction time and 65 ֯C reaction temperature.
