Kim et al. Hydrogenolysis of Glycerol to Propylene Glycol on Nanosized Cu–Zn–Al Catalysts Prepared Using Microwave Process
using co-precipitation methods for comparing the effect
of preparation method. The synthesized metal oxides
were characterized and their catalytic activity on the
hydrogenolysis of glycerol to propylene glycol in the pres-
ence of hydrogen was also examined along with the effect
of reaction conditions.
reaction. Selectivity to propylene glycol, acetol and ethy-
lene glycol were discussed in this study by considering
both the amounts detected and commercial importance.
3
. RESULTS AND DISCUSSION
Figure 1 shows the XRD patterns of Cu/Zn/Al (2/2/1) cat-
alysts prepared by different method. The XRD patterns
shows CuO and ZnO crystalline phase regardless of prepa-
ration method. CuO crystalline phase was observed at
2
. EXPERIMENTAL DETAILS
Cu(NO ) ·2.5H O, Zn(NO ) ·6H O and Al(NO ) ·9H O
3
2
2
3 2
2
3 3
2
ꢀ
ꢀ
(
>98%, Sigma-Aldrich) were dissolved 50 ml of distilled
2ꢁ = 35ꢂ5 and 38.5 corresponding to the most intense
17
water and then, 2.0∼6.0 M of malic acid was added to the
reflection of tenorite CuO. When the catalyst is prepared
by microwave process, a mixed oxide phase is detected at
solution. The solution was irradiated by microwave during
ꢀ
1
5 min with stirring. Microwave synthesis was performed
2ꢁ = 11ꢂ2 and 24.2 . Corresponding to JCPDS data, it is
using 600 W, 2.45 GHz home-made microwave digestion
system (LG Electronic Co.). After irradiation, the sam-
identified to have a crystalline phase of Cu Al Zn O .
0
ꢂ4
0ꢂ7
1ꢂ85
5
As shown in Figure 2, the catalysts reduced by hydro-
ꢀ
ꢀ
ples were calcined in an atmosphere of air at 450 C for
gen shows Cu crystallite diffraction peak at 43.1 and 50.1
6
h. The hydrotalcite type catalysts were prepared by typ-
instead of CuO peaks. This result indicates the active Cu
metallic species can be obtained from the hydrogen reduc-
tion at 300 C for 3 h.
ical co-precipitation method at constant pH as a reference
catalysts.
ꢀ
The metal composition of the catalysts was determined
by X-ray Fluorescence Spectrometer (XRF). The crystal
structures of the prepared mixed oxides were examined
by powder X-ray diffraction (XRD) with Cu-Kꢀ radiation
The BET surface areas of Cu/Zn/Al catalysts are mea-
sured and are shown in Table I. The surface areas of cata-
lysts increase with an increase of the amount of aluminum
oxide regardless of the preparation method. In addition, the
catalysts prepared by co-prepitation method have higher
surface area than those prepared by microwave process.
Table I shows glycerol hydrogenolysis conversion and
selectivities to acetol, propylene glycol and ethylene glycol
at 473 K on various catalysts used in this study.
(Rigaku Co. Model DMax). The BET surface area of the
prepared catalysts was determined by nitrogen physisorp-
tion data at 77 K using a NOVA 1000 e (Quantachrome
Delivered by Publishing Technology to: University of Waterloo
Co., USA). Temperature-programmed desorption (TPD) of
IP: 208.75.97.2 On: Fri, 30 Oct 2015 08:52:37
ammonia experiments were carried out using 100 mg cat-
Copyright: American Scientific Publishers
alysts under a gas flow (100 ml/min) of NH (2000 ppm)
3
Bulk CuO and ZnO show very poor activity for gly-
cerol hydrogenolysis. It is well known that the conversion
of glycerol via a dehydration reaction to acetol (hydrox-
ylacetone) followed by a hydrogenation reaction to selec-
diluted with helium. Mass spectrometer (HPR 20) was
used to monitor the ammonia desorption amount.
The hydrogenolysis of glycerol to propylene glycol was
carried out in a home-made glass-lined stainless steel auto-
clave reactor (Hanwoul Co., Korea). Each reactor with a
capacity 150 mL is equipped a stirrer, a heater and a tem-
perature controller. The reactor were flushed several times
with nitrogen followed by hydrogen. Then the reactor was
heated to the desired reaction temperature and pressurized
with hydrogen to the necessary pressure. The speed of the
stirrer was set constant 700 rpm throughout the reaction.
Unless specially mentioned, all catalysts without pretreat-
ment by hydrogen stream were used in this work.
11
tively produce propylene glycol. The catalyst for the
dehydration of alcohol should have either strong Lewis
or Bronsted acid sites. ZnO shows an activity solely for
glycerol dehydration without forming any hydrogenolysis
Reactants and products were analyzed by VARIAN
3800 Gas Chromatography (U.S.A) equipped with a flame
ionization detector (FID). The separation of reactant and
products were performed on an Agilent HP-FFAP capillary
column (25 m×0.32 mm×0.5 um) with the oven isother-
ꢀ
mal at 180 C. Detected liquid products mainly include
propylene glycol, ethylene glycol, and trace of amounts
of 1,3-propanediol, 1-propanol, 2-propanol, methanol and
ethanol. Conversion of glycerol is defined as the ratio of
the number of moles of glycerol consumed in the reaction
to the total moles of glycerol initially present. Selectiv-
ity is defined as the ratio of the number of moles of the
product formation to that of the glycerol consumed in the
Figure 1. X-ray diffraction patterns of Cu/Zn/Al (2/2/1) catalysts pre-
pared different method.
J. Nanosci. Nanotechnol. 15, 656–659, 2015
657
Kim, Dong Won
