Ahmad Alhazeem
Biodiesel from Coffee Grounds
Introduction
Natural products are products of natural origin including an entire organism that has not
been processed, part of an organism, an extract of an organism or exudates and pure compounds
isolated from plants, animals, or microorganisms1. There are a number of methods available for
extraction and isolation of natural products from their various sources. In this experiment the
natural product of biodiesel is isolated from coffee by a process that involves brewing the coffee,
extracting the triglycerides and transesterification to yield the biodiesel. A lot of uses have been
derived from natural products, especially plants, which mostly include in modern medicine and
in the pharmaceutical industry1.
The product of this experiment biodiesel, also known as fatty acid methyl esters, is
obtained through transesterification of triglycerides with base and methanol. Biodiesel is the
most widely accepted alternative fuel for diesel engines since it enhances biodegradability,
reduces toxicity, improves lubricity and it is completely miscible with petroleum diesel2. There
are many factors in which biodiesel can impact us where it can reduce trade deficit, create new
jobs, contribute to reducing emissions to global warming, improve the quality of life by reducing
the environmental and economic hazards, and help the farming community since the oil used to
make biodiesel can be domestically grown3.
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Ahmad Alhazeem
The mechanism of the base catalyzed transesterification reaction of triglycerides to
biodiesel is shown in Scheme 1. Methanol would first be deprotonated by the potassium
carbonate base to form a methoxide ion, which is not shown in the mechanism. In the
transesterification reaction, the carbonyl carbons of the triglycerides undergo a nucleophilic
attack by the methoxide ions forming a tetrahedral intermediate. This intermediate would then
proceed to form three equivalent molecules of biodiesel by rearrangement and another molecule
that undergoes protonation to form glycerol.
Scheme 1
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Ahmad Alhazeem
The purpose of this experiment is to isolate biodiesel from coffee by extracting the
triglycerides first and then carrying out the synthesis of biodiesel through transesterification with
base (potassium carbonate) and alcohol (methanol). Then characterize the content of the
biodiesel obtained by IR, GC and GC-MS.
Experimental
Biodiesel. Coffee (75 g) was first brewed. The wet grounds were then spread onto some
tinfoil and dried for 2 days in a 50 °C oven. After 2 days the dried coffee grounds (48 g), hexanes
(150 mL) and a magnetic stir bar were placed in a 500 mL round bottom flask. The
coffee/hexanes suspension was then refluxed with stirring at around 85 °C for 1.5 hours. After
reflux the flask was first cooled to room temperature and the coffee grounds were separated from
the hexanes using vacuum filtration where the liquid was kept. A stream of nitrogen was then
used to isolate the pure/crude oil (2.855 g) which was later stored in a sealed container. Crude oil
(2.855 g), methanol (0.623 g) and potassium carbonate (0.214 g) were placed in a round bottom
flask and refluxed with stirring between 60-65 °C for 30 mins. When the reaction time ended,
1M acetic acid was slowly added until neutralization of the reaction mixture. Hexanes (10 mL)
was later added to the flask and the solution was transferred to a large test tube. A solution of
90% methanol/water (5 mL) was then added where the layers were thoroughly mixed to allow
them separate. A Pasteur pipette was used to extract the top hexanes layer where it was later
dried over sodium sulfate. Evaporation of the hexanes from the solution eventually left with the
final purified product of biodiesel (1.283 g, 44.9 %); IR
(cm-1) 2922.5, 2853.0, 1741.6, 1459.8,
1436.0, 1169.3. GC (dichloromethane, 125 °C to 275 °C at 10 °C per min) RT (minutes) 13.67,
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Ahmad Alhazeem
13.72, 15.34, 15.39, 15.61, 17.35; GC-MS (dichloromethane, 125 °C to 275 °C at 10 °C per min)
RT 11.07 min, m/z 270; RT 12.72 min, m/z 294; RT 12.77 min, m/z 296; RT 12.98 min, m/z
298; RT 14.74 min, m/z 326.
Results and Discussion
The content of the biodiesel product obtained after the evaporation of hexanes was
analyzed by IR, GC and GC-MS. The results of the IR analysis were compared with the expected
values to verify the biodiesel product while the results of the GC and GC-MS analysis were used
to calculate the composition of the biodiesel.
The data was first analyzed using IR, which is shown in Figure 1. There are two peaks
first seen at 2922.5 and 2853.0 cm-1which represent the alkane carbon-hydrogen bond expected
at 2960-2850 cm-1. There is also two parts of the ester group that can be seen, which are the
carbon-oxygen double bond expected at around 1735 cm-1 shown by a peak at 1741.6 cm-1 and
the carbon-oxygen single bond expected at 1150-1060 cm-1 shown by a peak at 1169.3 cm-1. The
last peaks that can be recognized are at 1459.8 and 1436.0 cm-1 that can either show the umbrella
bend with an expected range of 1470-1430 cm-1 or the scissor bend with an expected range of
1490-1440 cm-1.
The content of the biodiesel was also analyzed by GC followed by GC-MS. In the initial
analysis of GC, the results shown in Figure 2 indicate that there are 6 components in biodiesel
since there are 6 different peaks excluding the ones related to the solvent in the beginning. The
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Ahmad Alhazeem
peak at RT 15.34 min has the highest composition of 44.2% and the peak at RT 17.35 min has
the lowest composition of 2.6%. Using the GC results, the data was further analyzed by GC-MS
to identify the compounds of the different peaks using their mass spectrum where the results are
shown in Figure 3. Unlike GC, there were 5 components that could be identified by GC-MS
which were hexadecanoic acid, 9,12-Octadecanoic acid (Z,Z), 9-Octadecanoic acid (Z),
Octadecanoic acid and Eicosanoic acid which are all methyl ester. The results show that 9,12Octadecanoic acid (Z,Z) has the highest composition of 40.4% and Eicosanoic acid has the
lowest composition of 2.7%.
Retention Time
Area
% Composition
13.67
6385
22.6%
13.72
3822
13.6%
15.34
12458
44.2%
15.39
2967
10.5%
15.61
1842
6.5%
17.35
726
2.6%
Figure 2
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Ahmad Alhazeem
Component
RT
Area
m/z
%
Composition
Hexadecanoic
11.07
1969842
270
36.4%
12.72
2189506
294
40.4%
12.77
636143
296
11.8%
12.98
470446
298
8.7%
14.74
145777
326
2.7%
acid
9, 12Octadecanoic
acid (Z,Z)
9-Octadecanoic
acid (Z)
Octadecanoic
acid
Eicosanoic acid
Figure 3
This isolation experiment has proved to be efficient in retaining the biodiesel from the
crude oil through the transesterification reaction since it had a moderate yield of 44.9%. Some of
the reasons that might not have made this yield higher are errors when calculating the amount of
base and alcohol that need to be used, and when separating the layers of hexanes with glycerol
where some of the hexanes layer was left behind. However the recovery of crude oil from the
coffee grounds was low with 3.8% which was lower than usual since only 48g of coffee grounds
was left after it was dried for a couple of days. This shows the extraction part of this experiment
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Ahmad Alhazeem
was not very efficient in obtaining the oil or that there isn’t much of triglycerides in the coffee
grounds.
Conclusion
So in conclusion natural product isolation was used in this experiment to obtain the useful
alternative fuel of biodiesel from coffee. The coffee grounds were first brewed and then left to
dry for a couple of days. The dried coffee grounds were then used in extracting the triglycerides
oil crude product. This crude oil was later used in carrying out the synthesis of biodiesel through
transesterification with potassium carbonate and methanol where pure biodiesel was obtained as
the final product. The content of the biodiesel was then analyzed by IR, GC and GC-MS to
verify the identity of the biodiesel and determine its composition. The result of the IR analysis
have shown that product is indeed biodiesel by having peaks matching with the expected values
and the results of the GC with GC-MS analysis have shown that the biodiesel product has five
different components that were identified.
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Ahmad Alhazeem
References:
(1) Sarker, S., Latif, Z., Gray, A.; Natural Product Isolation, 2nd edition, Humana Press Inc.,
Totowa, NJ, 2006: pp 1-22.
(2) Benjumea, P., Agudelo, J., Agudelo, A.; Basic Properties of Palm Oil Biodiesel-Diesel
Blends, Fuel, Volume 87, Elsevier, Colombia, 2008: pp 2069-2075.
(3) Ahmad, M., Khan, M., Zafar, M., Sultana, S.; Practical Handbook on Biodiesel
Production and Properties, Taylor & Francis Group, FL, 2013: pp 1-8.
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