http://www.greencarcongress.com/2014/02/20140226-ecodiesel.html
[Image and links in on-line article]
Researchers use CaO catalyst to produce biodiesel/monoglyceride blend;
avoiding waste glycerol
26 February 2014
A team led by researchers at the University of Cordoba (Spain) have
used a CaO alkaline heterogeneous catalyst to produce what they call a
“second-generation biodiesel” blend composed of 2:1 molar mixture of
conventional fatty acid methyl esters (FAME, or regular biodiesel) and
monoglyceride (MG). The process integrates glycerol—the conventional
by-product of the transesterification process used to produce FAME—as MG.
The resulting blend exhibits properties similar to conventional
biodiesel, while reducing waste and improving conversion. As reported in
their paper in the journal Fuel, the FAME/MG blend they produced using
the CaO alkaline heterogeneous catalyst was similar to such blends
produced by more expensive lipases.
Biodiesel is produced from vegetable oils or animal fats via a
transesterification reaction with a short chain alcohol and a basic
catalyst such as sodium or potassium methoxide. Regardless of the
specifics of a given conventional transesterification process, the
researchers note, in all cases, glycerol is collected as a byproduct.
The generation of glycerol not only represents a notable performance
loss in the process, it is also creating an enormous waste problem.
Thus, the transformation of waste glycerol into oxygen-containing
branched compounds … is currently being considered as an interesting
solution to provide an outlet for increasing glycerol stocks.
… In this respect, several oxygenated compounds, obtained by
glycerol transformation by etherification, esterification and
acetalisation, have been assessed as additives or additional components
for biodiesel formulation. The addition of these compounds has not only
improved the low-temperature properties of biodiesel (i.e., pour point
and cold filter plugging point) and viscosity, but also they did not
impair any other important biodiesel analyzed quality parameters.
… another target of great interest currently is the production, in
only one reaction, of new biofuels that integrate the glycerol as a
derivative product, miscible with the fatty acid methyl or ethyl esters
(FAME or FAEE) obtained in a unique transesterification process. … This
methodology avoids the glycerol separation before its transformation
and, in a similar way as previously obtained with derivatives of
glycerol, these biofuels not only prevent the waste generation of waste,
but also increase the yield of the process, always higher than nominal
10%, by incorporating some glycerol derivatives into the reaction products.
… In general, these techniques are based on the use of various
lipases, where instead of using methanol, the lipase-catalyzed synthesis
of FAME can also be performed using alternative alcohol donors such as
methyl or ethyl (alkyl) acetate or dimethyl carbonate. … However, the
current existing limitations to use industrial lipases are mainly
associated with their high costs, so that in order to achieve a further
increase in the viability and competitiveness [with] respect to the
enzymatic process, the present study aims to achieve the partial
transesterification reaction, through the kinetic control of the
chemical reaction, the obtain the same results previously described in
stereoselective enzymatic processes. Thus, this research aims to get the
same kind of biodiesel by using CaO like alkaline heterogeneous catalyst
as an alternative to the more expensive lipases.
—Calero et al.
In their study, the researchers found that the CaO catalyst was very
suitable for the partial transesterification of triglycerides, despite
the lower catalytic activity compared to conventional full
transesterification catalysts such as NaOH or KOH (resulting in the
production of three FAME and one glycerol molecules).
If used for conventional biodiesel, CaO needs to be operated at higher
pressures and temperatures; however the team obtained the new biodiesel
blend with CaO at atmospheric pressure; 6:1 molar ratio of methanol to
oil; 7% CaO loading; and 65 °C reaction temperature.
The CaO catalyst maintained sustained activity after being repeatedly
used for 20 cycles.
In this way, under the optimized experimental conditions, the
partial transesterification reaction was achieved through the kinetic
control of the chemical reaction to obtain the same results previously
described in stereoselective enzymatic processes. Thus, the same type of
biodiesel that integrates glycerol is obtained by using CaO, instead of
the more expensive lipases.
—Calero et al.
Resources
Juan Calero, Diego Luna, Enrique D. Sancho, Carlos Luna, Felipa M.
Bautista, Antonio A. Romero, Alejandro Posadillo, Cristóbal Verdugo
(2014) “Development of a new biodiesel that integrates glycerol, by
using CaO as heterogeneous catalyst, in the partial methanolysis of
sunflower oil,” Fuel, Volume 122, Pages 94-102, doi:
10.1016/j.fuel.2014.01.033
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