Cu/ZnxAlyOz supported catalysts (ZnO: Al2O3 = 1, 2, 4) for methanol synthesis

Article abstract of DOI:10.1016/j.cattod.2011.06.009

The main goal of this work was determination of the dependence of the physicochemical properties of Cu/support catalysts (ZnO, Al₂O ₃, ZnAl₂O₄, ZnAlO_2.5, Zn ₂AlO_3.5) with their activity in methanol synthesis. The formation of spinel ZnAl₂O₄ structure during calcination process was proved by XRD technique. The mechanism of methanol synthesis was discussed. Activity tests show that the most active catalyst was system supported on binary oxide ZnAl₂O₄.

Full text of DOI:10.1016/j.cattod.2011.06.009

Catalysis Today 176 (2011) 21–27
Contents lists available at ScienceDirect
Catalysis Today
journal homepage: www.elsevier.com/locate/cattod
Cu/ZnxAlyOz supported catalysts (ZnO: Al2O3 = 1, 2, 4) for methanol synthesis
Pawel Mierczynski∗, Tomasz P. Maniecki, Karolina Chalupka, Waldemar Maniukiewicz,
Wojciech K. Jozwiak
Technical University of Lodz, Institute of General and Ecological Chemistry, 90-924 Łód´z, Zeromskiego 116, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The main goal of this work was determination of the dependence of the physicochemical properties of
Cu/support catalysts (ZnO, Al2O3, ZnAl2O4, ZnAlO2.5, Zn2AlO3.5) with their activity in methanol synthesis.
The formation of spinel ZnAl2O4 structure during calcination process was proved by XRD technique. The
mechanism of methanol synthesis was discussed. Activity tests show that the most active catalyst was
system supported on binary oxide ZnAl2O4.
Received 29 September 2010
Received in revised form 30 May 2011
Accepted 9 June 2011
Available online 14 July 2011
© 2011 Elsevier B.V. All rights reserved.
Keywords:
Copper catalysts
ZnAl2O4
Binary oxide
Methanol synthesis
1. Introduction
The rate-limiting step was hydrogenation of bidenate formates
surface species.
Methanol is industrially produced from synthesis gas
CO/CO2/H2 under rather low temperature and high pressure
conditions over a ternary CuO–ZnO–Al2O3 catalysts [1]. During
the last decades, CO2 hydrogenation to CH3OH has gained wide
interest as a mean to contribute to reduction of CO2 emissions.
Furthermore the direct conversion of CO2 and hydrogen to CH3OH
has already been demonstrated with higher selectivity than CO and
lower reaction temperature [2]. However, there is still controversy
concerning the mechanism of methanol synthesis [3,4]. Some
authors claimed that carbon monoxide is the main source for
methanol synthesis. But this viewpoint cannot explain the remark-
able improvement of activity after CO2 introduction [5]. Saussey
[6] and Fujita [7] claimed that methanol synthesis carried out
from CO and CO2 hydrogenation has different mechanisms. Fujita
thought that during methanol synthesis running form CO and H2
mixture, zinc formate was formed first, followed by hydrogenated
to zinc methoxy and then reacted with surface hydroxyl species
to form methanol. Whereas, CO2 hydrogenation lead to both zinc
formate and copper formate formation on the catalyst surface, then
these formates are hydrogenated to methoxide, and hydrolyzed
to methanol. Qi Sun [8] suggested that methanol was formed
directly from CO2 hydrogenation both for CO2 and for CO/CO2
hydrogenation, and b-HCOO− species were the key intermediate.
Many studies and discussions about the role of copper during
hydrogenation of CO or CO2 are available in literature. Particle
size, surface area, metallic copper surface area and composition
of Cu/ZnO/A12O3 catalyst are important factors influencing on the
catalytic process. Chinchen et al. proposed a linear relationship
between the catalytic activity in methanol synthesis and metallic
copper surface area of the catalyst [9,10]. Fujitani et al. [11] reported
that the activity of methanol synthesis from CO increases with the
concentration of Cu+ sites. The Cu+ as well as Cu0 could possibly be
active species during methanol synthesis from CO2, where carbon-
ate, formate and methoxy spices may be intermediates.
Lavalley et al. [12] reported that methanol is formed via an active
formate species adsorbed on metallic copper, which depends on
the copper dispersion and the ability of the mixed oxide phases
(Cu–ZnO) to generate and store active hydrogen.
Additionally, activity of copper based catalysts can be improved
by mixtures of metal oxides MOx (M: Cr, Zn, Al) which were usually
produced by co-precipitation or impregnation methods. Catalysts
containing these metal oxides have been found to be more active
than the individual component [13–16]. In addition some transi-
tion metals have been used as promoters to modify the activity of
Cu–ZnO/Al2O3 catalysts in methanol synthesis [16].
Various methods for Cu/ZnO/A12O3 catalysts preparation which
allow to achieve large copper surface, fine particle size and opti-
mized compositions leading to high catalytic activity and selectivity
of methanol synthesis through CO or/and CO2 hydrogenation were
investigated. Tanaka and co-workers [17] prepared Cu/ZnO catalyst
from a solution of copper and zinc nitrates dissolved in ethylene
∗
Corresponding author. Tel.: +48 42631 31 25; fax: +48 42631 31 28.
E-mail address: mierczyn25@wp.pl (P. Mierczynski).
0920-5861/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.cattod.2011.06.009

22
P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
Table 1
glycol. They found that the selectivity to methanol was highest
when the ratio of Cu/ZnO was 1. Deng et al. [18] reported that
catalytic activity of methanol synthesis through CO2 hydrogena-
tion increasing with increasing of the metallic surface area for
Cu/ZnO/Al2O3 system until it reaches a maximum at Cu/ZnO = 8
and then decreases at higher molar ratio.
In the present work copper supported catalysts containing
20 wt.%. Cu (Al2O3, ZnAl2O4, ZnAlO2.5, Zn2AlO3.5, ZnO) were pre-
pared by conventional impregnation method. The main goal of this
work was investigation the influence of support composition on
the structure of the catalyst and its catalytic activity in methanol
synthesis from CO2/H2. The physicochemical properties of the cata-
lysts were examined by BET, XRD, DRIFT, TPR-H2 methods. Catalytic
activity test in methanol synthesis by CO2 hydrogenation were car-
ried out under elevated pressure (4 MPa) in fixed bed reactor.
BET surface area measurements and average pore size for supports: ZnAl2O4,
ZnAlO2.5, Zn2AlO3.5, Al2O3 and ZnO calcined 3 h in air at various temperatures.
Support
Calcination
Specific surface
area (m2/g)
Average pore
size (Å)
temperature (◦C)
Al2O3
400
600
600
600
400
237
63
60
19
37
27
30
42
55
–
ZnAl2O4
ZnAlO2.5
Zn2AlO3.5
ZnO
during the analysis was subtracted using Sonneveld, E.J. and Visser
algorithm. The data was then smoothed using cubic polynomial.
All calculations were done with X’Pert HighScore Plus computer
program.
2. Experimental
2.2.4. Diffuse reflectance infrared fourier transform spectroscopy
(DRIFTS)
2.1. Catalysts preparation
Infrared spectra were recorded with a Thermo Scientific Nico-
let 6700 FTIR spectrometer equipped with a liquid nitrogen
cooled MCT detector. Before analysis the sample was reduced
at 300 ◦C in gas reduction mixture (5%H2–95%Ar for 1 h). A res-
olution of 4.0 cm−1 was used throughout the investigation. 64
scans were taken to achieve a satisfactory signal to noise ration.
The background spectrum was collected at 50 ◦C after reduction.
Then the reduction mixture was shifted to a reaction mixture of
approximately 20% CO2 and 80% H2. Reaction was carried out in
temperature range 50–280 ◦C under atmospheric pressure. Spectra
were taken in each temperature after 10 min in reaction mixture
flow.
Copper supported catalysts Cu/ZnxAlyOz were prepared by wet
aqueous impregnation method. Binary oxides of ZnxAlyOz (molar
ratio Zn: Al = 0.5, 1, 2) were prepared by co-precipitation. Aque-
ous solutions of 1 M zinc acetate and 1 M aluminium nitrate were
mixed in appreciate quantity under vigorous stirring at 80 ◦C. A con-
centrated ammonia solution was then added by dropwise addition
until the pH reached values between 10 and 11 and the mixtures
were stirred for another 30 min. The resulting fine precipitates were
washed two times in deionized water and then dried at 120 ◦C for
15 h and subsequently calcined for 3 h in air at 600, 700 and 900 ◦C,
respectively. Choice of the first temperature calcinaion was pre-
scribed by necessity of spinel structure creation and for removal of
the acetate precursor from catalytic systems. Higher temperature
calcination was imposed to investigate of the phase composition
during the calcination process.
2.2.5. Catalytic activity test
Carbon dioxide hydrogenation tests were carried out in a fixed
bed reactor using a gas mixture of H2 and CO2 with molar ratio
3:1, respectively. The process was carried out under elevated pres-
sure (4 MPa) at 180 and 260 ◦C. Before activity tests, the catalysts
were pre-reduced for 2 h in a flow of 5% H2–95% Ar at 300 ◦C under
atmospheric pressure. The catalysts were cooled to the reaction
temperature of 260 ◦C and then the inlet flow was switched to
reaction mixture. The steady-state activity measurements were
taken after at least 12 h on the stream. The analysis of the reac-
tion products were carried out by an on-line gas chromatograph
equipped with FID detector and 10% Carbowax 1500 on Graphpac
column. The CO and CO2 concentrations were monitored by GC
chromatograph equipped with TCD detector (120 ◦C, 130 mA), and
Carbopshere 60/80 (90 ◦C) column. CO conversion was calculated
by the following equation:
Metal phase (Cu) was introduced on support surface by wet
impregnation method with an aqueous solution of its nitrate and
then the supported catalysts were dried at 120 ◦C and finally cal-
cined for 4 h in air at 400 ◦C for removal of nitrates and at 700 ◦C for
elucidate the interaction between support and active phase. Copper
loading was 20 wt.% in all cases.
2.2. Methods of catalysts characterization
2.2.1. Specific surface area and porosity (BET)
The specific surface area and porosity of the catalysts and
their supports were determined with automatic sorptometer Sorp-
tomatic 1900. Samples were prepared at 250 ◦C and 12 h evacuation
followed by low temperature nitrogen adsorption–desorption
measurements were carried out using BET, liquid N2 method.
ꢀ
ꢁ
(CO2 in feed − CO2 in effluent)
CO2 conv. =
× 100
(CO2 in feed)
The selectivity of the products were calculated as follows:
2.2.2. Temperature programmed reduction (TPR-H2)
ꢂ
ꢄ
Pi yield
The TPR-H2 measurements were carried out in an automatic
TPR system AMI-1 in the temperature range 25–900 ◦C with linear
heating rate 10 ◦C/min. Samples (weight about 0.1 g) were reduced
in hydrogen stream (5% H2–95% Ar) with the gas volume velocity
of 40 cm3 per minute. The hydrogen consumption was monitored
by a thermal conductivity detector.
ꢃ
Pi selectivity =
× 100
Pi yield
Pi is the mol number of every product.
3. Results and discussion
2.2.3. XRD measurements
The BET results embracing surface area and dominant pore
size for the calcined at various temperature supports (Al2O3, ZnO,
ZnAl2O4, ZnAlO2.5, Zn2AlO3.5) are shown in Table 1. The individ-
ual Al2O3 calcined at 400 ◦C had the largest specific surface area
of 237 m2/g compared to the ZnO sample which had the lowest
surface area of 37 m2/g. The binary oxides ZnAl2O4 and ZnAlO2.5
showed intermediate specific surface area of about 60 m2/g. On the
Room temperature powder X-ray diffraction patterns were
collected using a PANalytical X’Pert Pro MPD diffractometer in
Bragg-Brentano reflecting geometry. Copper CuK␣ radiation from
a sealed tube was utilized. Data were collected in the range 5–90◦
2ꢀ with step 0.0167◦ and exposition per one step of 27 s. Due to the
fact that raw diffraction data contain some noise, the background

P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
23
A
B
Fig. 1. (A) XRD patterns for Cu/Al2O3, Cu/ZnO catalysts calcined 400 and and 700 ◦C. (B) XRD patterns for binary oxides and copper catalysts 20%Cu/support (support–ZnAl2O4,
ZnAlO2.5, Zn2AlO3.5) calcined at 400 and 700 ◦C. (C) TPR profiles for copper supported catalysts supported on Al2O3 or ZnO. (D) TPR profiles for copper supported on binary
oxides calcined at 400 and 700 ◦C.
contrary Zn2AlO3.5 had the smallest surface area in comparison to
remaining binary oxides. This result can be explained by the largest
content of zinc oxide entering in composition of this system (see
Fig. 1B).
formation of spinel structure phase (ZnAl2O4). Increasing of the cal-
cination temperature causes only growth of sample crystallization
(see our previous work [19]). This indicated that all content of zinc
converts into spinel structure (AB2X4 – the compounds related to
AIIBIII2X4 system – where A – metal, B – three – valency element, X
– halogen including oxygen [20]).
The X-ray patterns of binary oxides after calcinations at 600 ◦C
and copper catalysts supported on different support calcined at 400
and 700 ◦C are shown in Fig. 1A and B, respectively. The XRD data
for binary oxide ZnAl2O4 calcined at 600 and 700 ◦C confirmed the
The diffractogrames recorded for ZnAlO2.5 and Zn2AlO3.5 biox-
ides shows that in addition to ZnAl2O4 spinel structure, zinc oxide

24
P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
phase was also detected (see Fig. 1B). It appears that the rest of zinc
which did not convert into spinel structure exists as an individual
phase. This fact can explain the lower specific surface area observed
for Zn2AlO3.5 (see Table 1).
this stage is attributed to copper oxides reduction. The presence
of high reduction effect and growth of zinc oxide phase content
on the diffractogrames of 20%Cu/ZnAl2O4, 20%Cu/ZnAlO2,5 cata-
lysts calcined at 700 ◦C suggest that CuAl2O4 phase is formed by
substitution of zinc ions by copper ions in the ZnAl2O4 structure
[19].
Diffraction curves recorded for copper catalysts supported on
Al2O3 and ZnO are presented in Fig. 1A. On the difractogrames of
20%Cu/Al2O3 catalyst calcined at 400 ◦C the presence of ␥-Al2O3
and CuO as a major phase [21] and CuAl2O4 as a minor phase were
detected. Increasing calcination temperature to 700 ◦C manifested
sample crystallization and enlargement of CuAl2O4 phase. Copper
aluminate CuAl2O4 phase is stable above 600 ◦C [22], which is con-
firmed by our results, showing that in the case of 20%Cu/Al2O3
catalyst calcined at 700 ◦C CuAl2O4 spinel structure was a major
phase.
XRD measurements carried out for 20%Cu/ZnO show that only
zinc and copper oxides phases are present. Increasing temperature
of calcination causes only catalyst crystallization.
Diffraction curves recorded for 20 wt.%. Cu catalysts supported
on binary oxides show zinc oxide, copper oxide and spinel ZnAl2O4
structure phases (see Fig. 1B). In the case of catalysts calcined at
700 ◦C the formation of CuAl2O4 spinel structure by substitution of
zinc ions by copper ions in the ZnAl2O4 structure by increasing of
the zinc oxide phase content was confirmed.
Fig. 2 shows the part of the IR spectra obtained in flowing
CO2/H2 reaction mixture under atmospheric pressure in the tem-
perature range 50–280 ◦C for copper catalysts supported on binary
oxides. Many authors [28–33] claim that the formate and carbon-
ate species were formed when Cu-based catalyst was exposed
to CO2/H2 or CO/CO2/H2 at low temperatures. The hydrogena-
tion of carbonate species to formate species was proved in several
reports [33–36]. Our studies show that during temperature pro-
grammed reaction, a change of species adsorbed on the catalyst
surface was observed. An IR spectrum showed that copper for-
mate (HCOO–Cu: 2925, 2850, 1620, 1364, 1350 cm−1), zinc formate
(HCOO–Zn: 2970, 2880, 2700, 1591, 1372, 1365 cm−1) carbonate
(CO32−: 1620, 1570–1440, 1220 cm−1), zinc methoxide (CH3O–Zn:
2935, 2825, 1060 cm−1) and gaseous CO (CO: 2118, 2171 cm−1
)
were formed in the course of the CO2–H2 during growth of tem-
perature of reaction [37–39]. At the beginning of reaction from
50 to 120 ◦C we can easily distinguish only carbonate species
(CO32−: 1620, 1570–1440, 1220 cm−1). These carbonate species
are formed by the reaction of CO2 or CO (CO comes from disso-
ciative adsorption of CO2 with hydroxyl group situated on metal
[37,38], which are further hydrogenated to more stable monoden-
tate or bidentate formate species at higher temperature. Starting
at 160 ◦C can be observed methoxy species formation. However,
very interesting result observed for all catalysts was the fact that
appearance of methoxy species was accompanied with growth
of b-formates intensity bands on the spectrum and these species
disappeared during the reaction evidenced by decreasing inten-
Two spinel phases ZnAl2O4 and CuAl2O4 are isostructural and
distinction of these phases in the same sample by XRD technique is
rather impossible due to reflexes display nearly coincident in their
diffraction patterns [23].
The reducibility of catalysts was examined by temperature pro-
grammed reduction. TPR profiles of copper supported catalysts are
shown in Fig. 1C and D. For 20%Cu/Al2O3 supported catalysts (see
Fig. 1C) we observed two or three reduction stages which depend
on calcination temperature. Two overlapped TPR profiles situated
at lower temperature are attributed to copper oxides reduction
(CuO → Cu2O → Cu) [24]. For catalyst calcined at 700 ◦C hydro-
gen consumption peak observed at about 760 ◦C is assigned to
spinel phase CuAl2O4 reduction which was also visible in the XRD
pattern recorded for 20%Cu/Al2O3 after calcination at 700 ◦C (see
Fig. 1A).
TPR profiles recorded for copper catalysts supported on ZnO
shows two partially resolved reduction effects as well as for
20%Cu/Al2O3 system calcined at 400 ◦C. These reduction stages are
connected with copper oxides reduction (CuO → Cu2O → Cu).
Similar results were obtained by Pettersson and co-workers
[25] who studied Cu/ZnO catalysts impregnated on ␥-Al2O3.
They reported that the reduction of CuO proceeds stepwise
(Cu2+ → Cu+ → Cu0) judging from the TPR results. Turco et al. [26]
also confirmed easy reduction of Cu2+ to Cu+ and Cu0 in the case of
CuO/ZnO/Al2O3 catalyst.
Wang et al. [27] investigated the reduction of Cu/␥-Al2O3 cata-
lysts and suggested that when Cu content is low (5%Cu wt.) only one
reduction peak (␣) is observed in the TPR patterns. However, with
increasing the Cu content additional reduction peak (␤) appears.
They claimed that the first peak ␣ represents the reduction of highly
dispersed copper oxide, the second peak ␤ was assigned to the
reduction of CuO crystal phase.
TPR profiles of copper catalysts supported on binary oxides
(see Fig. 1D) show one, two or three regions of hydrogen con-
sumption depending on catalysts composition and calcination
temperature. At low reduction temperature we observed one or
two reduction stages for all catalysts. These reduction effects are
connected with copper oxide reduction directly to metallic copper
or through reduction of CuO to Cu2O as an intermediately stage.
However, high temperature reduction effect observed in the case
of copper catalyst supported on ZnAl2O4, ZnAlO2,5 catalysts after
calcination at 700 ◦C is connected with CuAl2O4 structure reduc-
tion. Whereas, 20%Cu/Zn2AlO3.5 catalyst reduces in one stage and
−
sity of the band assigned to b-HCOOs species. This observation
can suggest that bidentate formates are directly hydrogenated
to methanol through methoxy species and the main intermedi-
ate species during methanol synthesis are b-HCOO− groups, and
this is the stage of the reaction which determines the rate of
methanol synthesis. It is noteworthy that the hydrogenation of
−
b-HCOOs species is greater than that of monodentate formate
species [35].
The results above are in agreement with previous reports
[37,40,41] which described that methanol was formed directly
from CO2 hydrogenation both for CO2 and CO/CO2 hydrogenation
and also confirmed that b-HCOO− species is the key intermedi-
ate for methanol synthesis and hydrogenation of this species is the
rate-limiting step of the reaction.
The influence of different support on the activity of cop-
per catalysts in methanol synthesis was also studied in this
work. The temperature characteristics of catalytic activity of cop-
per supported catalysts in hydrogenation of CO2 expressed in g
CH3OH g−1 cat. h−1 are presented in Fig. 3. The results of CO2
conversion and selectivity of methanol synthesis reaction carried
out at 180 and 260 ◦C by using Cu/Al2O3, Cu/ZnxAlyOz, Cu/ZnO
catalysts with 20 wt.%Cu loading are presented in Table 2. It is
evident that the CO2 conversion increases with increasing of the
reaction temperature. The methanol yield increases with growth
of reaction temperature and the molar ratio between Cu and
ZnO (see Fig. 3). The highest yield of methanol formation was
observed in the case of 20%Cu/ZnAl2O4 for which Cu/ZnO was equal
0.72.
The lowest yield and selectivity to methanol was found for
the 20%Cu/ZnO catalysts. Very similar selectivity demonstrated
20%Cu/Zn2AlO3.5 system with Cu/ZnO = 0.43. Intermediate yield
was shown Cu/ZnAlO2.5 catalyst. These results suggest that Cu–Zn
site are the active sites in methanol synthesis. The Cu/ZnAl2O4

P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
25
A
B
C
Fig. 2. DRIFT spectra for methanol synthesis from CO2/H2 recorded during temperature – programmed – reaction under atmospheric pressure for 20%Cu/support catalysts
(support = ZnAl2O4, ZnAlO2.5, Zn2AlO3.5).

26
P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
Table 2
The reaction results for methanol synthesis from CO2/H2 with various Cu/ZnxAlyOz catalysts.
Catalyst
CO2 Conversion(%)
Selectivity
CO (%)
CH4 (%)
180
MeOH (%)
180
C2+ (%)
180
DME (%)
180
Temperature (◦C)
180
260
180
260
260
260
260
260
20%Cu/Al2O3
4
4
3
5
4
8
10
8
11
12
51
17
16
13
25
53
25
18
9
0.5
3
2
0.2
6
0.1
3
2
0.3
2
48.5
79
82
5
46.8
70
76
2
–
–
–
81.8
65
0.1
1
4
88.7
78
–
1
–
–
–
–
1
–
–
–
20%Cu/ZnAl2O4
20%Cu/ZnAlO2.5
20%Cu/Zn2AlO3.5
20%Cu/ZnO
19
4
1
Reaction condition: weight of catalyst = 2 g, H2/CO2 ratio in the feed = 3, temperature = 180 and 260 ◦C, total pressure = 4 MPa.
2. The catalytic activity depends on the kind of support which is
used in methanol synthesis. The highest activity showed catalyst
supported on ZnAl2O4 bioxide (Zn/Al = 0.5 and Cu/ZnO = 0.72).
3. The b-HCOO− group formation from hydrogenation of carbon-
ate surface species as a intermediate of methanol synthesis was
proven. Disappearance of the methoxy group together with b-
HCOO− species confirmed the proposed mechanism that the key
stage of the reaction is hydrogenation of bidentate formate to
methoxy species and finally to main product – methanol.
Acknowledgements
The financial support of this work by the Polish Scientific
Research Council supports (Grant No. N N209 011234) is gratefully
acknowledged.
References
[1] R. Yang, X. Yu, Y.I. Zhang, Wenze Li, Noritatsu Tsubaki, Fuel 87 (2008) 443.
[2] R. Raudaskoski, E. Turpeinen, R. Lenkkeri, E. Pongrácz, R.L. Keiski, Catal. Today
144 (2009) 318.
[3] T. Inui, H. Hara, M. Takeguchi, J.B. Kim, Catal. Today 36 (1997) 25.
[4] M. Saito, T. Fujitani, M. Takeuchi, T. Watanabe, Appl. Catal. A 138 (1996) 311.
[5] Xiaojuan Wang, Haipeng Zhang, Wei Li, Korean J. Chem. Eng. 27 (4) (2010) 1093.
[6] J. Saussey, J.C. Lavalley, J. Mol. Catal. 50 (1989) 343.
Fig. 3. Influence of different support on activity of copper supported catalysts after
calcination at 400 ◦C.
[7] S.I. Fujita, M. Usui, H. Ito, N. Takezawa, J. Catal. 157 (1995) 403.
[8] Q. Sun, C.W. Liu, W. Pan, Q.M. Zhu, J.F. Deng, Appl. Catal. A 171 (1998) 301.
[9] G.C. Chinchen, M.S. Spencer, K.C. Waugh, D.A. Whan, J. Chem. Soc. Faraday Trans.
83 (1987) 2193.
[10] G.C. Chinchen, K.C. Waugh, D.A. Whan, Appl. Catal. 25 (1986) 101.
[11] T. Fujitani, M. Saito, Y. Kanai, T. Kakumoto, T. Watanabe, J. Nakamura, T. Uchi-
jima, Catal. Lett. 25 (1994) 271.
[12] F. Le Peltier, P. Chaumette, A. Kiennemann, J. Saussey, J.C. Lavalley, J. Chim. Phys.
93 (1996) 1376.
[13] T. Shisido, M. Yamamoto, D.L. Li, Y. Tian, H. Morioka, M. Honda, T. Sanko, K.
Takehira, Appl. Catal. A: Gen. 303 (2006) 62.
[14] M. Saito, T. Fujitani, M. Takeuchi, T. Watanabe, Appl. Catal. A 138 (1996)
311–318.
[15] M. Saito, T. Fujitani, I. Takahara, T. Watanabe, M. Takeuchi, Y. Kanai, K. Moriya,
T. Kakumoto, Energy Convers. Manage. 36 (1995) 577.
[16] Y. Nitta, O. Suwata, Y. Ikeda, Y. Okamoto, T. Imanaka, Catal. Lett. 26 (1994) 345.
[17] Y. Tanaka, Ch. Kawanura, A. Ueno, Y. Kotera, K. Takeuchi, Y. Sugi, Appl. Catal. 8
(1983) 325.
[18] J.F. Deng, Q. Sun, Y.L. Zhang, D. Wu, S.Y. Chen, Appl. Catal. A 139 (1996) 75.
[19] T.P. Maniecki, P. Mierczynski, K. Bawolak-Olczak, W. Maniukiewicz, W.K.
Jozwiak, Polish J. Environ. Stud. 18 (No.1B) (2009) 120.
catalyst having the highest Cu/ZnO molar ratio, and thus high-
est quantity of CuAl2O4 is created during calcinations process.
This is confirmed by the intensity of high temperature reduction
effect visible in the TPR profile of 20%Cu/ZnAl2O4 after calcina-
tions at 700 ◦C (see Fig. 1D). The fact that methanol synthesis are
exothermic reaction caused that highest conversions – and thus the
highest methanol yield – are obtained at low temperatures and high
pressures. As it was possible to expect the selectivity of copper sup-
ported catalysts decrease with increasing of reaction temperature.
This is due to the limitation of methanol synthesis reaction equi-
librium, because increasing temperature disadvantages methanol
formation. In distinguishing from methanol selectivity, the yield of
other products (CH4, CO, C2+, DME) grow with increasing reaction
temperature, which is responsible for continuously increasing CO2
conversion and decreasing selectivity to methanol at high temper-
ature.
[20] A.S. Korotkov, N.M. Alexandrov, Comput. Mater. Sci. 35 (2006) 442.
[21] J. Sang Chai Kim, Hazard. Mater. B91 (2002) 285.
[22] F. Meyer, R. Hepelmann, S. Mathur, M. Veith, J. Mater. Chem. 9 (1999) 1755.
[23] M.N. Barroso, M.F. Gomez, J.A. Gamboa, L.A. Arrua, M.C. Abello, J. Phys. Chem.
Solids 67 (2006) 1583.
[24] M. Ferrandom, J. Carno, S. Jaras, E. Bjornbom, Appl. Catal. A 180 (1999) 141.
[25] B. lindström, L.J. Pettersson, P.G. Menon, Appl. Catal. A 234 (2002) 111.
[26] M. Turco, G. Bagnasco, U. Constantino, F. Marmottini, T. Montanari, G. Raims,
G. Busca, J. Catal. 228 (2004) 43.
4. Conclusions
1. XRD and TPR results confirmed the formation of CuAl2O4 spinel
phase during calcination in the case of 20%Cu/Al2O3. Remaining
above conclusion, high temperature reduction effect located in
the same temperature range as for Cu/Al2O3 system indicated
also copper aluminate formation for Cu/ZnxAlyOz systems.
[27] Ching-Huei Wang, Chemosphere 55 (2004) 11.
[28] Ruiguin Yang, Yilu Fu, Yi Zhang, Noritatsu Tsubaki, J. Catal 228 (2004) 23.
[29] T. Fujitani, J. Nakamura, Appl. Catal. A Gen. 191 (2000) 111.
[30] B. Dean, Clarkeand Alexis T. Bell, J. Catal. 154 (1995) 314.

P. Mierczynski et al. / Catalysis Today 176 (2011) 21–27
27
[31] Yi Zhang, Ruiqin Yang, Noritatsu Tsubaki, J. Catal. 132 (2008) 93.
[32] Ruiqin Yang, Yi Zhang, Noritatsu Tsubaki, Catal. Commun. 6 (2008) 275.
[33] H. Shin-ichiro, Fujita, Masahito Usui, Hiroto Ito, Nobutsune Takezawa, J. Catal.
157 (1995) 403.
[38] B. Frank, F.C. Jentoft, H. Soerijanto, J. Kröhnert, R. Schlögl, R. Schomäcker, J. Catal.
246 (2007) 177.
[39] F. Le Peltier, P. Chaumette, J. Saussey, M.M. Bettahar, J.C. Lavalley, J. Mol. Catal.
A Chem. 132 (1998) 91.
[34] K.C. Waugh, Catal. Today 15 (1992) 51.
[35] S. Fujita, M. Usui, H. Ito, N. Takezawa, J. Catal. 157 (1995) 403.
[36] I.A. Fisher, A.T. Bell, J. Catal. 178 (1998) 153.
[40] D.B. Clarke, A.T. Bell, J. Catal. 154 (1995) 314.
[41] M. Bowker, R.A. Hadden, H. Houghton, J.N.K. Hyland, K.C. Waugh, J. Catal. 109
(1988) 263.
[37] Qi Sun, Chong-Wei Liu, Wei Pan, Qi-Ming Zhu, Jing-Fa Deng, Appl. Catal. A 171
(1998) 301.