Biofuels are becoming more attractive worldwide because of the high energy
demands and the fossil fuel resources that are being depleted. Biodiesel is one of the most
attractive alternative energy sources to petroleum diesel fuel and it is renewable, non toxic,
biodegradable, has low sulphur content and has a high flash point. Biodiesel can be generated
from domestic natural resources such as coconuts, rapeseeds, soybeans, sunflower, and waste
cooking oil through a commonly used method called transesterification. Transesterification is a
reaction whereby oil (e.g. sunflower oil) or fats react with alcohol (e.g. methanol) with or
without the presence of a catalyst (e.g. potassium hydroxide) to form fatty acid alkyl esters
(biodiesel) and glycerol. The high-energy input for biodiesel production remains a concern for the
competitive production of bio-based transportation fuels. However, microwave radiation is a method
that can be used in the production of biodiesel to reduce the reaction time as well as to improve
product yields. Sunflower oil is one of the biodiesel feedstocks that are used in South Africa and
is widely used in cooking and for frying purposes.
This study aims to use microwave irradiation to reduce the energy input for biodiesel production.
The effect of various reaction variables, including reaction time (10 – 60 seconds), microwave
power (300 – 900 watts), catalyst (potassium hydroxide) loading (0.5 – 1.5 wt%) and methanol
to oil molar ratio (1:3 – 1:9) on the yield of fatty acid methyl ester (biodiesel) was
investigated. The quality of biodiesel produced was analysed by Gas Chromatography (GC), Fourier
Transform Infrared Spectroscopy (FTIR) and viscometry. The FTIR results confirmed the
presence of functional groups of the FAME produced during transesterification.
The results showed that transesterification can proceed much faster under microwave
irradiation than when using traditional heating methods. The interaction between the alcohol and
oil molecules is significantly improved, leading to shorter reaction times (seconds instead of
hours) and improved diesel yields. The highest biodiesel yield obtained was 98% at 1:6
oil-to-methanol molar ratio for both 1 wt% and 1.5 wt% potassium hydroxide (KOH) at a reduced
reaction time (30 seconds). The chemical composition of FAME (biodiesel) obtained from different
conditions
i
contained palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1) and 70% linoleic acid
(C18:2). The physical properties (cetane number, viscosity, density and FAME content) of biodiesel
produced met the SANS 1935 specification. The energy consumption was reduced from 1.2 kWh with the
traditional transesterification to
0.0067 kWh with the microwave transesterification.
Microwave irradiation was shown to be effective in significantly lowering the energy consumption
for production of biodiesel with good quality for small scale producers. / Thesis (MSc (Engineering Sciences in Chemical Engineering))--North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/8768 |
| Date | January 2013 |
| Creators | Magida, Nokuthula Ethel |
| Publisher | North-West University |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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