(352f) Study of Ethanol Decomposition Mechanism over Combustion Synthesized Bimetallic Cu-Co Nanoparticles

        Study
of ethanol decomposition mechanism over combustion synthesized bimetallic Cu-Co
nanoparticles

Anchu Ashok¹,
Anand Kumar², Faris Tarlochan¹

1.    
Department of
Mechanical and Industrial Engineering, Qatar University, Doha, Qatar

2.    
Department of
Chemical Engineering, Qatar University, Doha, Qatar

Introduction: It is well known
that bimetallic catalysts show distinct physical and chemical properties differing
from their constituent monometallic catalyst. In this study, we investigate CuCo
bimetallic catalyst for low temperature ethanol dehydrogenation reaction. Transition
metals have traditionally been used for C-C bond cleavage, making them
efficient catalysts for hydrocarbon and oxygenated hydrocarbon reforming
reactions. Steam reforming, partial oxidation, dehydrogenation and
decomposition are the main routes for the hydrogen generation from ethanol. We
follow decomposition route for H₂ production along with other
necessary byproducts. Our findings indicate that bimetallic CuCo catalyst show
good performance during ethanol decomposition for hydrogen production in the
temperature range of 50ºC - 400ºC.

Synthesis: Solution
combustion synthesis (SCS) method is used to prepare bimetallic CuCo from the
aqueous solution of copper nitrate (Cu(NO₃)₂·6H₂O),
cobalt nitrate (Co(NO₃)₂·6H₂O), and
glycine (C₂H₅NO₂) as fuel with a glycine to metal
nitrate ratio of φ=0.5. An aqueous homogenous solution containing
synthesis precursors in appropriate amount is heated over a hot plate heater to
initiate the combustion reaction generating CuCo nanopowders. The resulted
powder is ground using a mortar and pestle to get a uniform powder  that was used to make catalyst pellets of size
0.6-1mm. Ethanol decomposition over bimetallic CuCo were conducted using in
situ diffuse reflectance infrared fourier transform spectroscopy (DRIFT) study
under N₂ flow at different temperatures (50, 100, 200, 300, 400ºC).

Results: The presence of bimetallic
copper-cobalt and their oxidized states were confirmed using XRD. SEM study indicates
the agglomerated nanoparticles of high porosity that are randomly distributed. EDS
and XRD results indicates the presence of higher amount of oxide in the
synthesized sample indicating the form to be like CuCoO₂. SEM image
in Fig. 1 also shows the non-uniform sized particles of bimetallic CuCo along
with agglomeration that are common in solution combustion mode. Particle size is
in the range of 20-30 nm. Copper-cobalt oxide prepared using combustion
technique was reduced prior to the decomposition reaction by passing H₂
in the reaction chamber at 300ºC. The presence of adsorbed ethanol and ethoxy
species over the reduced catalyst was clear from the FTIR spectrum between
50-100^°C. Changes in IR peaks were followed with temperature to decipher
the reaction pathway. IR peak at 3669cm^-1 shows the clear presence of
adsorbed OH on the catalyst surface. Above 150^°C, adsorbed ethoxy
species is decomposed into acetate species along with carbonate compound. Increasing
the temperature above 200ºC intensifies the peak at 2335-2367 cm^-1 showing
formation CO₂ during the reaction. At that period, the acetate
species are possibly dehydrogenated to acetaldehyde and other intermediate
species. Some carbon formation was also observed at higher temperature.

Fig 1. SEM of bimetallic CuCo oxide

REFERENCES

1.     
Kumar, et al.,
Catalysis Letters, 146
(2016), 4, 778-787

2.     
Ashok, et al., International
Journal of Hydrogen Energy, 42 (2017), 37, 23464-23473

ACKNOWLEDGMENTS

This publication was made possible by NPRP
grant (NPRP8-145-2-066) from the Qatar national research fund (a member of
Qatar foundation). The statements made herein are solely the responsibility of
the author(s).