Gas phase oxidation of aqueous ethanol using gold supported cerium oxide catalyst
Paresh H. Rana1, Parimal A. Parikh2*
1
Department of Chemical Engineering, Government Engineering College, Bhuj 370001
2
Department of Chemical Engineering, S.V. National Institute of technology, Surat 395007
E-mail:- ranaph78@gmail.com1, parimal.svr@gmail.com2*
1.
Introduction:
The constant exhaustion and uneven price of the available fossil resources implies new challenges to the future chemical
industries, as majority of the (>90%) all carbonaceous chemicals are produced from oil. The product derived from the
fossil fuels depends on the cost of fuels.1 Biomass can be a useful alternative for the production of high value commodity
chemicals and fuels.
Bioethanol, along with increased water content, is now being considered as a key renewable chemical raw material that is
alternatives to hydrocarbons. The increase in fundamental studies devoted to investigating the selective conversion of
ethanol into added value products like acetic acid, acetaldehyde, acetone etc. 2At the end of 2013 ethanol production
reached to 87.2 billion L a year all over world. 3 The catalytic gas phase oxidation of ethanol and other alcohols by such
available and environmentally friendly oxidizing agents as molecular oxygen (in air) for the purpose of devising new green
technologies for obtaining the corresponding aldehydes, carboxylic acids, and other derivatives is a high priority line of
study.
Various
heterogeneous
catalyst
have
been
reported
for
the
oxidation
of
ethanol
in
gas
phase;
Mo0.61V0.31Nb0.08Ox/TiO2,V2O5/TiO2,V-Mo-Te-Nb,Sn & Mo oxide, Au/TiO2,Co and Ni supported on mixed oxides and AuCu/SiO2. This paper describes the synthesis, characterization and use of Au supported cerium oxide for the gas oxidation of
aqueous ethanol.
2.
Material and Methods:
2.1 Materials: The gold precursor HAuCl4.xH2O was obtained from Finar chemicals, India contained 49.0 ± 0.5% by
weight of gold, Ceria Oxide (CeO2) was obtained from Sigma Aldrich, Banglore, India with particle size
approximately 25 nm.
2.2 Synthesis of catalyst: Au/CeO2 synthesized by wet impregnation method.
2.3 Catalyst characterization: IR spectra of sample were collected in reflection mode using Zn-Se optics in Bruker Alpha
Eco-ATR spectrometer. Catalyst structures were examined by X-ray diffraction (XRD) on a Bruker - D8 discover
equipped with a Ni-filtered Cu Kα radiation source (λ = 1.542 Å) of 40 kV and 30 mA. Scanning electron microscopy
(SEM) studies were performed using HITACHI VP SEM S-3400N.
2.4 Catalytic testing: Catalytic gas phase reactions were conducted in all heated stainless steel continuous fixed bed flow
system using 1gm of Au/CeO2 catalyst and 10 wt % aqueous ethanol solutions as feedstock. The liquid (aq. Ethanol)
was mixed with air (21 % O2, 79% N2) prior to enter in the reactor. The mixer was allowed to flow through catalyst
bed for 60 min before monitoring reaction products.
1
3.
Results and Discussions:
3.1 X-ray Diffraction: - A very small diffraction line at 2Ѳ = 38.34◦, that can be attributed to the (1 1 1) plane of Au was
seen in the case of Au/CeO2 (Fig. 1); this is not unusual and indicates that the small Au atoms loading are of small
clusters (if not a sharp peak would be present).
Expected
Au (111)
Figure 1: XRD Pattern of Au/CeO2
3.2 Catalytic activity: - The catalytic activities were tested at temperature range from 175 – 275 °C at constant pressure of
10 bars. As shown in fig. 2, ethanol conversion increased up to 20% with increased temperature. The selectivity of
acetaldehyde remains 100 % up to 225°C. Then it was decreased to 85 % at 275°C. However, increased selectivity of
acetone was observed between 225 to 275°C.This may be due to presence of oxygen of cerium oxide on the surface.
110
100
90
80
70
60
50
40
30
20
10
0
25
20
15
10
5
% Conversion
% selectivity
No formation of acetic acid and other gases like CO2 were found.
0
150 175 200 225 250 275 300
Temperature°C
Figure 2: Ethanol oxidation at different temperature and constant pressure of 10 bars and mole ratio of O2/Ethanol- 1:1.
Product selectivities of ( ) acetaldehyde,( ) acetone and (◊) ethanol conversion
4.
Conclusion: The Au supported cerium oxide was successfully synthesized and characterized by XRD and FTIR. It
shows the good activity for the conversion of aqueous ethanol (10 % wt). Maximum 20 % conversion was achieved at
lower mole ratio of O2/Ethanol (1:1) and lower residence time of 300 sec. The formation of acetone taking place
between 225 to 275°C where never been mentioned.
References:[1]
Tembe, S.; Patrick, G.; Scurrell, M., Gold Bull, 42(4), 2009, 321-327
[2]
Gorbanev, Y. Y.; Kegnæs, S.; Hanning, C. W.; Hansen, T. W.; Riisager, A., ACS Catal., 2 (4), 2012, 604–612
[3]
Takei, T.; Suenaga, J.; Ishida, T.; Haruta, M., Top. Catal., 58 (4-6), 2015 , 295–301
2