Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Development of analytical methods to characterise biodiesel has become central to the
overall success of the marketing of biodiesel fuel. In this regard, different bodies including
the American Society for Testing and Materials (ASTM) and the European normalization
(EN) have come up with various methods to determine important biodiesel parameters such
as total glycerol, methanol and the fatty acid methyl esters (FAMEs), etc. Various studies
have been conducted on the parameters mentioned above using a variety of instrumentation
and sample preparations. The best methods reported are those that have been adopted by
both the ASTM and EN standards.
The purpose of this study was to develop alternative analytical methods to both the
recommended ASTM and EN methods and, in some cases, to make modifications to both
standards (ASTM D 6571 and EN 14214) and methods to determine total and bound
glycerol, the ester content and also methanol content in biodiesel. Moreover, water washing
after transesterification and the effect this practice has on biodiesel cold flow properties such
as kinematic viscosity, cloud and pour point and density were evaluated. The possibility of
using the iodine value to predict the feedstock source of an unknown biodiesel was also
investigated. Six different vegetable oil samples were transesterified with methanol and used
for this study. The six samples used were palm, crown, sunflower, waste vegetable oil (wvo),
peanut and rapeseed biodiesel.
Quantitative results indicated that the use of programmable temperature volatilisation (PTV)
for total glycerol did not produce the required repeatability of between 1-4% relative standard
deviation(RSD) for total glycerol analyses in biodiesel with precision of 25%, 86%, 25% and
56% for free glycerol (FG), monoglycerides (MG), diglycerides (DG), and triglycerides (TG)
respectively. The standard requires a relative standard of between 1-4%
As an alternative to the method using gas chromatography, normal phase high performance
chromatography (HPLC) with binary gradient elution was used to determine the bound
glycerol content. This method proved accurate and repeatable with RSD % of 0.33, 1.12,
and 1.2 for TG, DG and MG respectively.
Following the EN14103 protocol (European standard ester determination), the Zebron ZBWAX
column which is comparable to the specification recommended by EN14103 but
afforded the determination of ester content from the esters of myristic acid (C14:0) to behenic acid (C22:0) with reproducibility with RSD % of 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96,
and 5.21 for methyl esters of myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidoic,
gadoleic and behenic acid respectively.
Solid phase micro extraction (SPME) using GC-MS was developed as an alternative to both
the EN14110 and ASTM D93 protocols for determining the methanol content in biodiesel.
For this method, polyethylene glycol fibre (PEG) was used together with a deuterated
methanol internal standard and a DB-FFAP (60m×0.25um×0.25um) column. Less volume of
sample was required as compared to the EN14214 method. This method was found to be
sensitive, accurate and repeatable with a RSD % of 4.82.
The Iodine number of biodiesel decrease compared to their corresponding feed stock and
therefore predicting the feed stock of an unknown biodiesel was going to be difficult .Results
from this study indicated that it is not possible to predict the feed stock source of an
unknown biodiesel from its iodine value.
The effect of water washing after phase separation on biodiesel cold flow properties such as
kinematic viscosity, density, cloud and pour point depended on the type of biodiesel
produced. We observed that water washing after transesterification caused an increase in all
the cold flow properties of sunflower biodiesel, whereas only the densities and kinematic
viscosities increased in the case of palm and waste vegetable oil biodiesel. The cloud and
pour point of the latter two diesel samples remained unchanged after water washing. Thus,
the effect of water washing on biodiesel cold flow depended on the type of biodiesel.
Blending a highly saturated biodiesel (fewer numbers of double bonds) with a less saturated
biodiesel (higher number of double bonds) resulted in an improvement of both the pour and
cloud points of the resultant biodiesel blend. / AFRIKAANSE OPSOMMING: Die ontwikkeling van analitiese metodes om biodiesel te karakteriseer word tans as ‘n
kernmaatstaf gesien om biodiesel suksesvol te bemark. Hiervoor het verskeie liggame wat
die Amerikaanse Vereniging vir Toetsing van Materiale (AVTM) en die Europese
Normalisering (EN) insluit met verskeie standaard analitiese metodes vorendag gekom om
belangrike biodiesel parameters soos bv. totale gliserol, metanol en vetsuur metielesters te
meet. Om hierdie parameters te bepaal is van ‘n wye verskeidenheid toetse met
verskillende instrumente en monsterbereidings gebruik gemaak. Die beste metodes is deur
beide die AVTM en EN aanvaar.
Die doel van hierdie studie was om metodes te ontwikkel wat as alternatiewe kan dien tot die
wat deur die AVTM en EN voorsgeskryf is. In sommige gevalle is aanpassings tot beide die
standaarde (AVTM en EN) en metodes aangebring om die totale en gebonde gliserol-, esteren
metanolinhoud te bepaal. Verder is die effek van ‘n water wasstap na transesterifikasie
op biodiesel se kouevloei eienskappe gevalueer wat eienskappe soos kinematiese
viskositeit, vertroebelingspunt, gietingspunt en digtheid insluit. Die moontlike gebruik van die
Jodiumpunt om die bron van die voerstof van ‘n onbekende diesel te bepaal is ook
ondersoek. In hierdie studie is ses verskillende oliemonsters van plantaardige oorsprong
gebruik wat d.m.v. metanol getransesterifiseer is. Hierdie monsters het palm-, kroon-,
sonneblom-, afvalplant-, grondboontjie- en raapsaadolie ingelsuit.
Tydens die studie is programmeerbare temperatuur vervlugtiging (PTV) vergelyk met inkolom
inspuiting soos deur AVTM D6584/EN14214 vir totale gliserol analise voorgeskryf.
Kwantitatiewe resultate het getoon dat die PTV metode nie die verlangde akkuraatheid van
‘n relatiewe standaardafwyking (RS) van 1-4% vir beide vrye en gebonde gliserol kon
handhaaf nie. Die akkuraatheid was in die omgewing van 25%, 86%, 25% en 56% vir vrye
gliserol (VG), monogliseriede (MG), digliseriede (DG) en trigliseriede (TG), onderskeidelik.
Normale fase hoë werkverrigting vloeistofchromatografie met ‘n binêre elueeringsgradiënt is
as alternatief tot gaschromatografie (GC) ondersoek om die gebonde gliserolinhoud te
bepaal. Al was die GC metode meer sensitief, het die vloeistofchromatografie metode ‘n
hoë graad van akuraatheid en herhaalbaarheid getoon met RS% waardes van 0.33, 1.12 en
1.2 wat vir TG, DG en MG, onderskeidelik, verkry is. ‘n Zebron ZB-WAX kolom is vir die EN14103 protokol gebruik. Behalwe vir ‘n groter lengte
kon hierdie kolom met spesifikasies soos deur EN14103 voorgeskryf vergelyk word. Met die
gebruik van hierdie kolom kon die esterinhoud van miristiensuur (C14:0) tot behensuur (C14:0)
bepaal word. ‘n Hoë graad van herhaalbaarheid met RS% waardes van 6.81, 1.91, 7.27,
0.64, 1.18, 1.55, 6.03, 1.96 en 5.21 vir die metielesters van miristien-, palmitien-, stearien-,
oleïn-, linoleïn-, linoleen-, aragidoon-, gadoleïen- en behensuur is onderskeidelik verkry.
Om die metanolinhoud van die biodiesel te bepaal is soliede fase mikroekstraksie (SFME)
m.b.v. gaschromatografie-massaspektrometrie (GC-MS) as alternatiewe tot EN14110 en
AVTM D93 ontwikkel. In hierdie metode is daar van poliëtileenglikolvesels (PEG) en
gedeutereerde metanol saam met ‘n DB-FFAP kolom (60 mm x 0.25 mm x 0.25 mm) gebruik
gemaak. Hierdie metode het ‘n kleiner monstervolume as die EN14214 metode benodig en
was sensitief, akkuraat en hehaalbaar wat tot ‘n RS% waarde van 4.82 gelei het.
Op grond van die Jodiumwaarde van biodiesel en hul ooreenstemmende voerstowwe het
hierdie studie bevind dat die Jodiumwaarde nie gebruik kan word om die voerstof van ‘n
onbekende diesel kan voorspel nie.
Die effek van ‘n water wasstap na faseskeiding op verskeie kouevloei eienskappe soos
kinematiese viskositeit, vertroebelingspunt, gietingspunt en digtheid het van die tipe diesel
afgehang. Dit is bevind dat ‘n water wasstap na transesterifikasie ‘n toename in al die
kouevloeieienskappe van sonneblomdiesel tot gevolg gehad het. In teenstelling hiermee het
slegs die kinematiese viskositeit en digtheid van palm- en afvalplantdiesel vermeerder terwyl
hul vertroebelings- en gietingspunte onveranderd gebly het. Die hipotese dat ‘n water
wasstap na transesterifikasie tot swak kouevloei eienskappe lei is dus as onwaar bevind
aangesien hierdie eienskappe deur die tipe biodiesel bepaal word.
Deur ‘n hoogs versadigde biodiesel (lae aantal dubbelbindings) met ‘n minder versadigde
biodiesel (hoë aantal dubbelbindings) te vermeng het tot ‘n verbetering van beide die
vertroebelings- en gietingspunte gelei. / Centre for Renewable and Sustainable Energy Studies
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4245 |
| Date | 03 1900 |
| Creators | Prah, Ebenezer |
| Contributors | Callanan, L. H., Lorenzen, L., University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 102 p. : ill. |
| Rights | University of Stellenbosch |
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