(305b) Electrochemical Conversion of Fatty Acids to Produce Green Diesel | AIChE

(305b) Electrochemical Conversion of Fatty Acids to Produce Green Diesel

Authors 

Coronella, C. J. - Presenter, University of Nevada, Reno
Wagner, C. - Presenter, University of Nevada, Reno
Busch, R. - Presenter, Pacific Propellants

Electrochemical
conversion of fatty acids to produce green diesel (aka renewable
diesel)

We are developing an
electrochemical process to convert fatty acids to green diesel. Under
appropriate conditions of temperature, current density, solvent
mixtures etc., free fatty acid salts can be decarboxylated in a
specialized electrolysis cell. The resulting alkyl fragments form
hydrocarbons with a carbon chain shortened by one atom, producing C
15
and C
17
hydrocarbons
from typical, lipid-based fatty acid feedstocks.

The
chemistry is relatively straightforward. An unsaturated fatty acid,
e.g. oleic acid, subjected to this process is transformed into
unsaturated C17-hydrocarbons:

CH3(CH2)7CH=CH(CH2)7COO-
→ CH3(CH2)7CH=CH(CH2)5CH=
CH2 + CO2 + H+ + 2e-

Traditional
refining and upgrading processes, such as “hydrotreating”,
are commonly being run at 300-500 Celsius as well as thousands of psi
of pressure. The process under development permits the
stereospecificity (i.e. cis-double bonds) in oleic and other
unsaturated acids to be retained. This contributes to the excellent
low-temperature performance of the hydrocarbons so produced. Thus,
this fuel has properties that easily meets or even exceeds those of
fossil-derived diesel fuel.

As
shown in the equation above, the process also produces molecular
hydrogen as well as carbon dioxide as byproducts. Hydrogen is a
valuable byproduct, useful in other areas of a biorefinery, or
directly as a fuel or salable commodity. The carbon dioxide can be
easily separated and used as is, or fed back to an algae colony or
other CO2-consumer.

The
talk presents results from experiments with a prototypical reactor,
that has processed pure oleic acid, palmitic acid and commercially
available mixtures to produce high quality hydrocarbon fuel products.
The effects of pH, temperature, and current density are evaluated.