Ahn et al.
Catalytic Activity of Nanosized CuO–ZnO Supported on TC in Hydrogenation of CO2 to CH3OH
Table I. Preparation conditions and physical parameters of CuO–
ZnO/TiO2 catalysts prepared by CP method.
and the reaction properties for catalytic hydrogenation of
CO2 to CH3OH were investigated.
Catalyst
aTCalꢂ (ꢀC) bDTC (mesh) cSBET (m2 g−1
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2. EXPERIMENTAL DETAILS
2.1. Catalysts Preparation
CuO–ZnO/TiO2 (900-4)
CuO–ZnO/TiO2 (900-2)
CuO–ZnO/TiO2 (900-4)
CuO–ZnO/TiO2 (900-6)
CuO–ZnO/TiO2 (1100-4)
900
1000
1000
1000
1100
40–60
20–30
40–60
60–80
40–60
7ꢂ8
23ꢂ6
16ꢂ8
14ꢂ3
12ꢂ4
Thermal treatment of TC to form TiO2 was performed at
900, 1000, 1100 ꢀC under air atmosphere. CP method was
used to prepare CuO–ZnO/TiO2 catalyst containing weight
ratio copper, zinc and TC (40.6:50.3:9.1 wt%). Aqueous
solution of Cu(NO3ꢁ2 ·3H2O, Zn(NO3ꢁ2 ·6H2O, and TiO2
powder were mixed, and the mixture was add to the deion-
ized water with vigorous stirring as well as the aqueous
solution of Na2CO3 as a precipitant and pH of the sus-
pension liquid was kept constant at the value of 8.0. After
filtration and washing, the catalyst was dried at 100 ꢀC for
Notes: aTemperature of thermal treatment. bParticle size of catalysts. cBET specific
surface area.
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is readily decreased above 1100 C. The sieved different
particles had similar values in the range of 14∼23 m2 g−1
.
SEM images of as-prepared CuO–ZnO on different size
of treated TC are shown in Figures 1(A)–(C). It can be
seen that well dispersed nanosized CuO and ZnO parti-
cles are formed on treated TC surface and the particles
contained Cu, Zn, and Ti species (Fig. 1(D)). TEM image
(Fig. 1(E)) shows that the well-dispersed small particles
are CuO–ZnO species, indicating that strong adhesion of
CuO–ZnO nanoparticles on thermally treated TC could be
obtained by improving superficial roughness, which could
enhance the both catalytic activity and selectivity toward
CH3OH synthesis.
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24 hrs, calcined at 200 C for 1 hr and then at 300 C
for 3 hrs.
The prepared CuO–ZnO/TiO2 catalysts were character-
ized by using N2 gas adsorption analyzer (ASAP-2010,
Micromeritics), scanning electron microscopy (SEM,
S-3500N, Hotachi) and transmission electron microscopy
(TEM, JEM-2100F, Jeol). The chemical composition of
representative surface particles was analyzed by energy
dispersive spectroscopy (EDS).
Activity results for CH3OH synthesis from CO2 hydro-
genation over the CuO–ZnO/TiO2 catalysts prepared
from treated TC at different temperature are shown in
2.2. Catalytic Activity
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Figure 2(A). Maximum treatment temperature of TC
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Catalytic activities were tested for CH3OH synthesis using
a fixed-bed down stream flow reactor. Catalyst was loaded
in the reactor and the reduced in a stream of a gas H2 at
300 ꢀC for 3 hrs. The temperature of pre-heater and reactor
were controlled by PID controller, and total reaction pres-
sure was regulated with a back pressure regulator. After
cooling the catalyst bed to the reaction temperature 250 ꢀC,
the reaction gas, which consisted of CO2 (27 mol%) and
H2 (73 mol%), was fed at 40 mL min−1 using a mass flow
controller. The exit line from the reactor to the gas sampler
was heated to prevent condensation of any volatile prod-
ucts. Reactant and product gas mixtures were analyzed by
using the gas chromatograph (GC-2014, Shimadzu) with a
thermal conductivity detector, in which two parallel con-
nected columns, Porapak-Q and MS-5A, were used to sep-
arate reaction products. Gas chromatograph was equipped
with a two 6-way valves for on-line sampling.
was performed at 1100 ꢀC because TC became to be
so brittle when it was treated at above 1100 ꢀC. The
CuO–ZnO/TiO2 (1100-4) catalyst shows over 20% CO2
Copyright: American Scientific Publishers
(A)
(C)
(E)
(B)
(D)
3. RESULTS AND DISCUSSION
Table I shows the BET specific surface area of all samples
tested in this study. Untreated TC used as a raw material
exhibited very low surface area with near zero and it was
increased when it was treated by thermal oxidation (data
not shown), which would expect to improved adhesive
ability of metal oxide active species to treated TC surface.
BET surface area of CuO–ZnO/TiO2 catalyst is increased
Figure 1. SEM imagꢀes of CuO–ZnO/TꢀiO2 catalysts using TC treated at
(A) 900 ꢀC, (B) 1000 C, and (C) 1100 C. (D) EDS spectrum of dotted
square in (C). (E) TEM image of CuO–ZnO nanoparticles prepared by
CP method (Insert of EDS spectrum).
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with increasing the treated temperature up to 1000 C and
J. Nanosci. Nanotechnol. 16, 2024–2027, 2016
2025