(220j) Algal FAME Production With A NOVEL Surfactant Based Catalyst In A Reactive Extraction

ALGAL FAME PRODUCTION WITH A NOVEL SURFACTANT
BASED CATALYST IN

A REACTIVE EXTRACTION

*Kamoru A. Salam, **Sharon B. Velasquez-Orta, ***Adam
P. Harvey

*Kamoru.salam@ncl.ac.uk,
**Sharon.velasquez-orta@ncl.ac.uk, ***adam.harvey@ncl.ac.uk

School of Chemical Engineering and Advanced Materials
(CEAM), Newcastle University,

NE1 7RU, United Kingdom.

ABSTRACT

One major
challenge in conventional algal biodiesel production is the high energy
requirement of the drying and solvent extraction steps. The high solvent
requirement, (usually hexane) for the oil extraction in this process also has a
significant environmental impact. Alternatively,
biodiesel production could take place via in situ transesterification
(?reactive extraction?). In this process fatty acid methyl ester (FAME) is produced
directly from micro-algal biomass using methanol containing a catalyst. This
approach is simpler and potentially more cost-effective, because of its
elimination of the solvent extraction. The current study involved development
of a novel surfactant catalyst (zirconium dodecyl sulphate) for usage in the ?reactive
extraction? of FAME from Chlorella vulgaris and Nannochloropsis occulata. Additionally, the FAME yield produced
when using sodium dodecyl sulphate and H₂SO₄ catalyst was
investigated. Microalgae was also characterised before and after the reactive
extraction in terms of carbohydrate and protein
content. For Chlorella strains a
maximum 67wt% FAME yield was reached at 24 hours by the sodium dodecyl sulphate
and H₂SO₄ catalyst; 54wt%  FAME yield by the H₂SO₄
catalyst. For the Nannochloropsis a
maximum 75wt% FAME yield was reached at 12 hours by the sodium dodecyl sulphate
and H₂SO₄ catalyst; 44wt%  FAME yield by the H₂SO₄
catalyst. At 12 hours the FAME yields produced by the zirconium dodecyl
sulphate were 67wt% for Nannochloropsis
and 8wt% for the Chlorella. In
conclusion this finding shows that:

·        
The inclusion
of sodium dodecyl sulphate in H₂SO₄ significantly
improved the FAME yields obtained from Nannochloropsis
and Chlorella.

·        
A zirconium
dodecyl sulphate catalyst performed better
with Nannochloropsis than in Chlorella.

·        
The
micro-algae maintains almost all the protein content and some of the

Carbohydrate
after the in situ transesterification

·        
The reaction time and yields
were significant function of algae strain and catalyst.

Key words:
reactive extraction, microalgae, catalyst, FAME, H₂SO₄,
surfactant

INTRODUCTION

During plant photosynthesis, bio-oils are produced
as triglycerides which have a high combustion heat.. One
way of utilising this energy is trans esterification.
The use of refined oil for trans esterification is however not economical as ~
88% of total production cost of this conventional two steps biodiesel
production is ascribed to refined oil feedstock (Haas, 2006). Similarly
biodiesel production from non-food oil crops is not sustainable. Microalgae are
one of the sustainable biofuel feed stocks because of their compelling
advantages. They are non-food biofuel feed stocks. They
can be cultivated on non-arable land. Algae can be grown on the sea or
wastewater. They can also be used for capture highly concentrated CO_{2 .}

Production of FAME from micro-algae via in situ trans
esterification is simple and potentially more economical since ~90% of the
process energy is accounted for by the solvent extraction and drying steps in
the conventional trans esterification (Lardon et al., 2009). Previous studies have demonstrated the feasibility
of obtaining greater FAME conversion from such in situ trans esterification than from a conventional two-step
approach (Lewis et al., 2000; Vicente et al., 2009. The major
drawback of this method is the requirement of a large amount of methanol. This
is necessary since methanol plays a dual role: it acts as an oil extractor and
as a reactant. Moreover, the need to recover methanol from the products streams
may add additional cost to the process.

This present research may render the process more
economical by producing co-associating value products such as carbohydrate,
protein and other components in the micro-algal residue after in situ trans esterification.

MATERIALS
AND METHOD

Procedure
for in situ trans
esterification

This is a modification of
Velasquez-Orta et al. (2012). The
following process conditions were maintained in the in situ trans esterification: 100 milligram of microalgae,
temperature: 60^oC, mixing rate: 450 rpm, mole ratio of catalyst to
oil: 8.5:1, mole ratio of methanol to oil: 600:1 (Either the surfactant
catalyst, Sodium dodecyl sulphate and H₂SO₄ or H₂SO₄  catalyst) and methanol was added to
each tube consecutively and it was transferred to a shaking incubator (IKA KS 4000i control). The in situ trans
esterification was run for time ranged from 30minutes - 36hours. After each
completed reaction the tube was kept in a freezer for at least 6 hours to stop
the reaction. The algae residues were separated from the bulk liquid by
centrifugation. The bulk liquid mixture of methanol, FAME and by-products was
transferred in pre-weighed tubes. The final weight of the bulk liquid was
recorded for each tube and the FAME concentration was measured by gas
chromatography.

RESULTS AND
DISCUSSION

FAME
yield profiles obtained in an in situ
trans esterification of freeze dried cells of Nannochloropsis occulata is shown figure
1. It was observed that the FAME profiles for the three catalysts used general
increased with reaction time. This is the general trend of a normal reaction.
However, a drop in the FAME yield after 12 hours was observed with the SDS and
H₂SO₄ catalyst. This could be due to conversion of FAME
to free fatty acid by a side reaction. It was also observed that ~70% increase
in FAME yield was produced by SDS and H₂SO₄  more than that of H₂SO₄  at 12 hour. FAME yield produced by the
Zirconium dodecyl sulphate catalyst was also more than that of H₂SO₄
catalyst at 24 hours.

Fig.1: Reactive
Extracted FAME Yield Profiles of the Nannochloropsis

Molar ratio of methanol to oil = 600;
molar ratio of catalyst to oil = 8.4; Agitation rate = 450 rpm; Temperature =
60^oC; SDS: Sodium dodecyl sulphate; ZDS: Zirconium dodecyl sulphate

FAME yield profiles obtained in an in situ trans
esterification of spray dried cells of Chlorella
vulgaris is shown figure 2. It was observed that the FAME profiles for the
three catalysts used general increased with reaction time. However, after 4
hours the FAME yield produced by the ZDS decreased with reaction time.
Similarly, a relatively low performance of the ZDS catalyst was observed in
this strain. This could be due to the difference in the cell wall Chemistry
between the two strains. The inclusion of SDS with H₂SO₄ enhanced
the FAME yield obtained from this species. At 24 hours ~24% increase in FAME
yield was obtained by Sodium dodecyl sulphate and H₂SO₄ than
that of H₂SO₄ catalyst.

Fig2. : Reactive
Extracted FAME Yield Profiles of the Chlorella vulgaris

Molar ratio of methanol to oil = 600;
molar ratio of catalyst to oil = 8.4; Agitation rate = 450 rpm; Temperature =
60^oC; SDS: Sodium dodecyl sulphate; ZDS: Zirconium dodecyl sulphate

The
protein and carbohydrate content of the Nannochloropsis
residue was measured after the reactive extraction. The results of the
quantification are shown in Figure 3 and 4 respectively. It can be seen from the
figure 3 that the biomass maintains almost all the protein content after the
reactive extraction. The residual carbohydrate in contrast was lower than their
original values before the reactive extraction. This shows that some of the carbohydrates
have been hydrolysed during the reaction to simple sugars and other co-associated
products.

Fig.3: Protein content of the Nannochloropsis
before and after the reactive extraction

\s

Fig. 4: Carbohydrate content of the Nannochloropsis
before and after the reactive extraction

The
protein and carbohydrate content of the Chlorella
residue was also measured after the reactive extraction. The results of the
quantification are shown in Figure 5 and 6 respectively. It can be seen from the
figure 5 that the biomass maintains almost all the protein content after the
reactive extraction. The residual carbohydrate however was lower than their
original values before the reactive extraction. This also shows that some of
the carbohydrate has been hydrolysed during the reaction to simple sugars and
other co associated products.

Fig.5: Protein content of the Chlorella  before and after the reactive extraction

Fig.6: Carbohydrate content of the Chlorella  before and after reactive extraction

Table 1: Initial Biochemical Content of the
microalgae strains

^aMeasured
using acid digest by Gerhardt et al. [1]

^bMeasured
using Nitrogen protein conversion factor for microalgae by Lourenc et al. [2]

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