Promoted ternary CuO-ZrO2-Al2O3 catalysts for methanol synthesis

Article abstract of DOI:10.2478/s11532-013-0368-3

Ternary CuO-ZrO₂-Al₂O₃ catalysts promoted by palladium or gold were prepared and tested in CO hydrogenation reaction at 260 C under elevated pressure (4.8 MPa). The promotion effect of palladium or gold addition on the physicochemical and catalytical properties of CuO-ZrO ₂-Al₂O₃ catalysts in methanol synthesis (MS) was studied. The catalysts were characterized by BET, XRD, TPR-H₂, TPD-NH₃ methods. The BET results showed that the ternary system CuO-ZrO₂-Al₂O₃ had the largest specific surface area, cumulative pore volume and average pore size in comparison with the promoted catalysts. The yield of methanol can be given through the following sequence: 5%Pd/CuO-ZrO₂-Al₂O₃ > CuO-ZrO ₂-Al₂O₃ > 2%Au/CuO-ZrO₂-Al ₂O₃. We also found that the presence of gold or palladium on catalyst surface has strong influence on the reaction selectivity. The high selectivity of gold doped ternary catalyst is explained by the gold-oxide interface sites created on the catalyst surface and the acidity of those systems. The higher selectivity to methanol in the case of the palladium catalyst is explained by the spillover effect between Pd and CuO. [Figure not available: see fulltext.]

Full text of DOI:10.2478/s11532-013-0368-3

Cent. Eur. J. Chem. • 12(2) • 2014 • 206-212
DOI: 10.2478/s11532-013-0368-3
Central European Journal of Chemistry
Promoted ternary CuO-ZrO -Al O
2
2
3
catalysts for methanol synthesis
Research Article
*
Paweł Mierczynski , Piotr Kaczorowski, Agnieszka Ura,
Waldemar Maniukiewicz, Marcin Zaborowski,
Radoslaw Ciesielski, Adam Kedziora, Tomasz P. Maniecki
Lodz University of Technology,
Institute of General and Ecological Chemistry,
9
0-924 Lodz
Received 6 May 2013; Accepted 4 October 2013
Abstract: Ternary CuO-ZrO -Al O catalysts promoted by palladium or gold were prepared and tested in CO hydrogenation reaction at 260°C under
2
2
3
elevated pressure (4.8 MPa). The promotion effect of palladium or gold addition on the physicochemical and catalytical properties of
CuO-ZrO -Al O catalysts in methanol synthesis (MS) was studied. The catalysts were characterized by BET, XRD, TPR-H , TPD-NH
2
2
3
2
3
methods. The BET results showed that the ternary system CuO-ZrO -Al O had the largest specific surface area, cumulative pore volume
2
2
3
and average pore size in comparison with the promoted catalysts. The yield of methanol can be given through the following sequence:
%Pd/CuO-ZrO -Al O > CuO-ZrO -Al O > 2%Au/CuO-ZrO -Al O . We also found that the presence of gold or palladium on catalyst
5
2
2
3
2
2
3
2
2
3
surface has strong influence on the reaction selectivity. The high selectivity of gold doped ternary catalyst is explained by the gold-oxide
interface sites created on the catalyst surface and the acidity of those systems. The higher selectivity to methanol in the case of the
palladium catalyst is explained by the spillover effect between Pd and CuO .
Keywords: Methanol synthesis • Ternary systems • Copper catalyst • CuZrAl • Bimetallic catalysts
©
Versita Sp. z o.o.
adsorption of CO and CO over those centres compared
to Cu or ZnO systems [5].
1
. Introduction
2
Methanol is a very important chemical compound
Many researches [7-10] also reported that the
with a wide range of applications (e.g. as a kind of addition of ZrO to copper catalysts increases their
2
transportation fuel or source of hydrogen for fuel cells). specific surface area and thermal stability [5,7].
Industrially, methanol is produced from synthesis gas
Rhodes et al. [6] suggest that the ZrO structure plays
2
CO/CO /H under elevated and high pressure conditions. an important role in methanol synthesis. They claimed
2
2
The best known catalysts for methanol synthesis and that the catalysts containing the monoclinic structure of
reformation of methanol are copper/zinc/alumina based ZrO were five or six times more active than those crafted
2
oxide catalyst [1-3].
from ZrO tetragonal structure. This effect was explained
2
It should be noted that Cu/ZnO/ZrO and Cu/ZrO2 by an increase in the content of acid groups Zr - OH on
2
catalysts are also extensively studied in the methanol the catalyst surface and by increasing the adsorption
synthesis reaction (MS) showing high activity and capacity of CO.
stability compared to a Cu/ZnO catalyst [4-10]. The yield
The effect of different oxide promoters such as: Ba,
of methanol synthesis reaction carried out over copper Cs, Fe, Ga, La, Mg, Mn on catalytic activity of Cu/ZrO2
catalysts deposited on ZrO2 is comparable or even in methanol synthesis was also studied. The addition of
higher in comparison with the Cu/ZnO catalyst.
various oxide-like Cs, Ga, La, Mg, and Mn increases the
High activity of copper catalysts promoted by ZrO can degree of dispersion of the copper supported catalysts
2
be explained by several factors. Firstly, the participation after reduction. Magnesium and manganese oxides
of acid centers originating from ZrO2 improve the accumulate on the copper surface and facilitate the
*
E-mail: mierczyn25@wp.pl
206

P. Mierczynski et al.
enrichment of the catalyst surface of the Zn and Zr 2.2. Catalysts characterization
oxides. Lanthanum oxide increases the strength of the 2.2.1. Specific surface area and porosity (BET)
interaction between Cu and ZrO and induces a spillover The specific surface areas of catalysts were determined
2
effect between these phases. In addition, the formation by the BET method based on low temperature (77 K)
of solid solutions between La and Ce oxides results in nitrogen adsorption in ASAP 2020 apparatus.
stabilization of ZrO2.
On the other hand, the promotion of copper catalysts 2.2.2. Temperature programmed reduction (TPR-H2)
by Ba and Cs oxides increases the amount of methoxyl The TPR-H2 measurements were carried out in an
and formaldehyde groups formed on the catalysts automatic TPR system AMI-1 in the temperature range
-1
surface during the process compared to the reaction of 25 - 900°C with a linear heating rate of 10°C min .
carried out with the unpromoted catalysts [11].
Samples (weight about 0.1 g) were reduced in hydrogen
In spite of numerous works dealing with various stream (5% H - 95% Ar) with a volumetric flow rate of
2
3
-1
promotersthatareusedtoimproveactivityandselectivity 40 cm min . Hydrogen consumption was monitored by
of copper supported catalysts CuO/ZrO and CuO/ZnO/ a thermal conductivity detector.
2
ZrO in methanol synthesis, there is still a great deal
2
of ongoing research concerned with developing new 2.2.3. X-ray diffraction (XRD) measurements
methods of improving catalyst activity, selectivity and Room temperature powder X-ray diffraction patterns
stability. Taking into account the above mentioned were collected using a PANalytical X’Pert Pro MPD
suggestions, we decided to prepare doped palladium diffractometer in Bragg-Brentano reflecting geometry.
and gold ternary systems. We characterized all catalyst Copper CuK radiation from a sealed tube was used.
a
systems by BET, TPR-H , TPD-NH and XRD methods Data was collected in the range 5 - 90° 2q with a step of
2
3
and examined in carbon monoxide hydrogenation to 0.0167° and exposure per step of 27 s. Due to the fact that
elucidate the interaction between all components of the raw diffraction data contains some noise, the background
ternary system and promoters (Pd, Au) and its effect on during the analysis was subtracted using Sonneveld, E.J.
catalytic activity in methanol synthesis reaction.
and Visser’s algorithm. The data was then smoothed
using a cubic polynomial. All calculations were done
using X'Pert HighScore Plus computer software.
2
. Experimental procedure
2.2.4. Temperature programmed desorption of
2
.1. Catalysts preparation
ammonia-(TPD-NH3)
The nitrates of copper, chromium and aluminum were The procedure of catalyst surface acidity measurement
used as material precursors. The ternary systems were include: purification of catalyst surface, adsorption of
prepared by co-precipitation method of appropriate ammonia and temperature programmed desorption.
hydroxides using ammonia hydroxide as a precipitating Catalyst sample purification (about 0.15 g)
-
agent. The mixtures were dried (T = 100°C for 24 h) removal of water from the system leading to surface
and calcined for 3.5 h in air atmosphere at 400ºC. dehydroxylation was completed in pure argon stream
3
Appropriate amounts of aqueous solutions of copper, with a volume velocity of 40 cm per minute at 400°C
aluminum and zyrconyl nitrate(V) were taken to obtain for 2 h and, after cooling the sample to 100°C, the argon
formulas of ternary system CuO-ZrO -Al O (name used stream was switched into a gaseous ammonia flowing
2
2
3
in the work CuZrAl) with the following molar ratios of 0.5 h through the catalyst sample to entirely saturate
oxides 1:2:1. Palladium catalysts 5%Pd/CuO-ZrO -Al O
its surface. After NH adsorption, the excessive amount
2
2
3
3
(name used in the work 5%Pd/CuZrAl) were prepared of weakly and physically adsorbed ammonia on the
by a wet impregnation method using aqueous solutions catalyst surface had been removed by flushing of the
of palladium nitrate(V). Deposition-precipitation method catalyst in pure argon stream with a volume velocity
3
was applied to prepare gold catalyst (name used in the 40 cm per minute.
A temperature programmed
work 2%Au/CuZrAl). An aqueous solution of HAuCl was desorption of ammonia- TPD-NH run - was done in a
4
3
heated to 70°C with stirring. Then the ternary system temperature range of 100-500°C with a linear heating
-1
was slurried into the solution, followed by the addition rate of 27°C min and a thermo-conductivity detector to
of appropriate amounts of urea to obtained a pH value obtain a TPD-NH profile.
3
around 9. After washing in deionized water and filtration,
the sample was dried at 120°C overnight and calcined 2.2.5. Catalytic activity tests
4
h in air at 400°C. The Pd and Au loading in catalytic Activity tests in the methanol synthesis reaction were
systems was 5% and 2% wt., respectively. carried out using the high pressure fixed bed reactor
2
07

Promoted ternary CuO-ZrO -Al O
3
2
2
catalysts for methanol synthesis
Table 1. Results of BET surface area, monolayer capacity and
average pore radius.
Catalytic
material
BET surface Monolayer
area capacity
Average
pore radius
[nm]
2
-1]
3
-1
[
m
g
[cm g ]
Al O3
237
54.5
57.5
52.3
54.1
2.50
2.12
2.25
2.18
2
CuZrAl
250
227
235
2
5
%Au/CuZrAl
%Pd/CuZrAl
using a gas mixture of H and CO with a molar ratio
2
of 2:1, respectively. The process was carried out under
elevated pressure (4.8 MPa) at 260°C and products were
analyzed by GC (gas chromatograph). Before activity
tests, all catalysts were pre-reduced for 2 h in a flow
of 5% H - 95% Ar mixture at 300°C under atmospheric
2
pressure. The steady-state activity measurements were
taken after at least 12 h on the stream. The analysis of
the reaction products were carried out by an on-line gas
chromatograph equipped with a 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 (65°C) column. CO conversion was
calculated by the following equation:
The selectivity of the products was calculated as follows:
Figure 1. Pore size distribution for CuZrAl, 2%Au/CuZrAl and 5%
Pd/CuZrAl.








Pi yield
Pi selectivity =
×100
∑Pi yield
significantly the specific surface area of CuZrAl catalyst.
The surface area of catalysts promoted by gold or
palladium decreases slightly compared to the ternary
catalyst, as a result of pore block by PdO [13] and Au
P is the mol number of every product.
i
[
14,15] species.
3
. Results and discussion
The value of monolayer capacity and average pore
radius are similar for all systems, with the exception of
Al O whose average pore radius is slightly higher and
equals 2.50 nm.
3
.1. Surface area measurement and pore size
distribution
2
3
The specified values of catalyst surface area (BET),
Pore size distribution characteristic for all catalysts
monolayer capacity and average pore radius are is presented on Fig. 1. The small difference in pore size
presented in Table 1 for ternary CuO-ZrO -Al O
distribution ranges can be observed and the average
2
2
3
system and promoted by gold and palladium catalysts, dominant pore radii were: 2.12, 2.25 and 2.18 nm for
respectively. As a reference material, BET results of CuZrAl, 2%Au/CuZrAl and 5%Pd/CuZrAl, respectively.
precipitated Al O were also added. Ternary CuZrAl
2
3
catalyst prepared by co-precipitation method exhibited 3.2. X-ray diffraction (XRD) measurements
higher specific surface area in comparison to single XRD measurements for CuZrAl system and promoted
phase Al O . The similar results were observed by catalysts calcined in air at 400°C are presented in
2
3
Yu et al. [12]. A further addition of a small amount of Fig. 2. The XRD measurements for all catalytic systems
gold (2% Au) or palladium (5% Pd) does not influence were performed in the range of 2q angle 20-90°. XRD
208

P. Mierczynski et al.
to the ZrO , to become broader and more diffused
2
suggesting the existence of smaller or higher dispersed
zirconia.
3
.3. Temperature programmed reduction TPR-H2
The reduction behaviour of ternary and doped gold
or palladium ternary catalysts was also studied in this
work. The TPR profiles of all catalytic systems are given
on Fig. 3. The results of the TPR analysis carried out for
ternary CuZrAl and gold doped ternary catalysts 2%Au/
CuZrAl showed that those catalysts are reduced in one
single stage, and this reduction stage is connected with
the copper (II) oxide reduction. It is worth emphasizing
Figure 2. XRD patterns for CuZrAl, 2%Au/CuZrAl, 5%Pd/CuZrAl
catalysts calcined in air at 400°C for 3.5 h.
analysis confirmed the rather amorphous nature of all that in the case of the gold doped catalyst, we observed
systems (see Fig. 2).
a shift of this reduction peak into a lower temperature
The XRD curve of CuZrAl sample (see Fig. 2) range, which means that the addition of gold facilitates
showed only two small characteristic peaks positioned at the reduction of copper (II) oxide. It is suggested that
2
q = 46 and 67° which are attributed to g-Al O structure the reduction of copper oxide is also promoted due to
2 3
[
2
16,17] and one wide diffraction peak situated between the synergistic effect between copper oxide and zirconia
7 and 38° assigned to amorphous ZrO . The phase [24].
2
composition studies performed for CuZrAl catalyst did
Only on the TPR of 5%Pd/CuZrAl catalyst can we
not confirm any diffractions peaks attributed to copper easily observe three reduction peaks. The first reduction
oxide. The absence of CuO diffraction peaks indicated stage observed in the initial stage of reduction located
the formation of highly dispersed copper species, which in the temperature range 50 - 100°C is assigned to
were not detectable by XRD technique (~ 5 nm) [12,18]. the PdO reduction. Whereas, the next two reduction
The X-ray diffraction patterns of promoted ternary peaks are attributed to the copper oxides reduction
systems present the same tendency as for CuZrAl according to the following scheme: CuO → Cu O →
2
catalyst. It is worth noticing that for all studied catalysts Cu. It is worth emphasizing that the reduction peaks
a characteristic peak attributed to amorphous zirconia recorded for palladium catalyst were shifted towards
ZrO is visible [19].
lower temperatures in comparison to ternary catalyst.
2
Only in the case of 2%Au/CuZrAl calcined at 400°C This indicates that the addition of Pd into the copper
additional diffraction peaks at 2θ = 38, 44, 64.5 and catalyst facilitates the reduction of copper species by
7
7.5° are observed and those peaks are characteristic spillover effect between Pd and CuO (see Fig. 3). The
for metallic gold phase [14,15].
enhancement of CuO reduction in the 5%Pd/CuZrAl
Diffraction pattern of 5%Pd/CuZrAl sample calcined system is explained on the basis that hydrogen is easily
at 400°C exhibits mainly extremely small characteristic dissociated on Pd metal particles and then split on the
peaks located at 2θ = 29.5 and 45.4° assigned to the surface of CuO phase.
palladium oxide like structure [20,21].
The presence of various copper (II) oxide crystallite
The XRD measurements of CuO/ZrO2 catalysts sizes on the catalyst surface is excluded because the
prepared by impregnation and co-precipitation methods, phase composition study of 5%Pd/CuZrAl catalyst did
containing various ranges of copper content, were also not confirm the presence of CuO phase on the diffraction
performed by Luo et al. [22]. The phase composition pattern recorded for this system. This result confirms the
study of copper catalyst with low copper loading (10%) high dispersion of copper oxide on the catalyst surface
prepared by the impregnation method showed the (see Fig. 2) and suggests a two-step reduction of the
presence on the XRD pattern only diffraction reflexes catalyst.
originating from the tetragonal phase of ZrO2 (2θ =
In our previous work [20], we investigated palladium
3
0 and 34.8°) [23]. On the other hand, the catalyst catalysts supported on zinc aluminate spinel structure
prepared by the co-precipitation method possesses a and we also observed the reduction profile at a low
smaller and broader peak in the range 20-50°, which temperature range. TPR-H profiles of 2% Pd/ZnAl O
4
2
2
is a characteristic of the typical amorphous structure of catalyst are characterized by two hydrogen consumption
tetragonal ZrO . These similar results were obtained in peaks situated at 30 and 80°C. The first profile we
2
our study. Increasing the copper content in the case of attributed to the reduction of highly dispersed palladium
both catalysts caused the diffraction peaks, attributed oxide, the second profile indicates reduction of small
2
09

Promoted ternary CuO-ZrO -Al O
3
2
2
catalysts for methanol synthesis
Table 2. Distribution of acid centers for ternary and doped ternary catalysts calcined in air for 3.5 h at 400°C.
Catalyst
Weak centers
[
medium centers
[mmol g cat]
strong centers
[mmol g cat]
450-550°C
Total amount
mmol g- cat]
1
-1
-1
of desorbed NH
3
-
1
100-300°C
300-450°C
[mmol g cat]
CuZrAl
0.05
0.08
0.08
0.11
0.08
0.08
0.09
0.07
0.05
0.25
0.23
0.21
2
%Au/CuZrAl
%Pd/CuZrAl
5
the b peak grew continuously with the copper load. The
a peak is connected with copper species that interact
strongly with the oxygen vacancies in the ZrO . The b
2
peak is attributed to the bulk CuO species reduction [27].
Shimokawabe et al. [28] also investigated the reduction
behaviour of Cu/ZrO2 and they also observed two
reduction steps. Those reduction peaks are attributed
2+
to the reduction of highly dispersed CuO and/or Cu
ions in an octahedral environment and in bulk CuO,
respectively.
Reduction studies of CuO/ZrO2 catalyst have
also been reported by Zhou et al. [29]. Those authors
attributed those two peaks to the reduction of highly
dispersed copper species and the second peak located
at higher temperatures were attributed to the TPR peak
where the reduction of bulk CuO does not interact with
Figure 3. TPR of CuZrAl, 2%Au/CuZrAl and 5%Pd/CuZrAl catalysts
after calcination in air at 400°C for 3.5 h.
the ZrO support.
2
3
.4. Temperature programmed desorption of
ammonia - (TPD-NH )
3
Temperature-programmed desorption of ammonia is
a conventional method for characterizing acidity in
catalytic systems [30,31]. The acidity of ternary and
doped ternary catalysts with gold or palladium was
evaluated by the TPD-NH3 method, and ammonia
desorption profiles are shown in Fig. 4.
Figure 4. TPD-NH3 profiles for CuZrAl, 5%Pd/CuZrAl and 2%
Au/CuZrAl catalysts calcined in air for 4 h at 400°C.
Table 2 presents data illustrating the distribution of
palladium crystallites interacting with the surface of acid centers based on TPD of ammonia from catalytic
ZnAl O , respectively. systems. It can be easily observed from the Fig. 4
2
4
Reduction of Pd/ZnO systems were studied by and Table 2 that all catalytic systems exhibited three
Cubeiro et al. [25]. They reported that PdO is an easily desorption regions on the TPD-NH3 profile. Weak,
reducible oxide, even at room temperature. They also medium and strong acid sites are visible on TPD curves,
observed reduction peaks situated between 30 and respectively. The highest total amount of desorbed
-1
1
50°C which was attributed to the reduction of PdO to NH exhibited CuZrAl catalyst (0.25 NH mmol g ). It
3
3
metallic palladium.
is worth noticing that the ternary catalysts also showed
The TPR studies of the CuZrAl catalysts were also the lowest content of weak centers (see Table 2 and
performed by Bellido [26] and co-workers. The authors Fig. 4). The next difference observed for CuZrAl catalyst
note that all profiles exhibit two reduction peaks: one in comparison to other systems was a higher amount of
around 200°C (a peak) and the other around 300°C (b acidic centers desorbing ammonia at the temperature
peak).
Similar results were observed by Dow et al. [27]. They
range 300-450°C.
Introduction of gold or palladium into ternary systems
also reported about two a and b reduction peaks on the caused the increase of the ammonia desorbed in the
TPR-H curve in CuZr samples. Authors observed that temperature range 100-300°C. This result can explain
2
210

P. Mierczynski et al.
Table 3. The activity results for methanol synthesis from CO/H over promoted and unpromoted CuZrAl catalysts.
2
Catalyst
CO Conversion [%]
Selectivity
CO [%]
CH [%]
MeOH [%]
2
4
Temperature = 260°C
CuZrAl
13.7
9.9
15
45.7
30.5
27
1
5
4
53.3
64.5
69
2
5
%Au/CuZrAl
%Pd/CuZrAl
Reaction condition: weight of catalyst = 2 g, H /CO ratio in the feed = 2, temperature = 260°C, total pressure = 4.8 MPa.
2
catalysts are related with the acidity and reducibility
of investigated catalysts. Promoted CuZrAl catalysts
showed the highest amount of weak acidity centers on
the catalyst surface.
Haruta et al. [32] studied gold catalysts in methanol
reaction and they claimed that the activity of gold
catalysts strongly depends on the nature of support oxide
and requires high dispersion of gold. They reported that
the high activity of gold catalysts is ascribed to the gold-
oxide interface sites.
In our work, we also confirmed the higher selectivity
of palladium and gold doped catalysts in comparison
to CuZrAl system. This result can also be explained by
the gold-oxide interface sites, the existence of which
was confirmed by the TPR method. Reduction studies
performed for this catalyst confirmed the interaction
between those two active components that were
visualized by facilitated reduction of copper species in
Figure 5. Catalytic activity for ternary CuZrAl and promoted by Pd
and Au ternary catalysts at 260°C under 4.8 MPa.
the differences in the activity observed for all systems the case of promoted gold catalysts. This result confirms
in methanol synthesis. The only difference in the acidity the interaction between gold and copper, and the ability
of the promoted catalyst was the fact that the palladium to create an interface between gold and copper oxide
catalyst exhibited a lower amount of strong centres and while the activity and selectivity of palladium catalyst is
lower total acidity that can explain the differences in explained by the spillover effect between Pd and CuO.
activity between those two catalytic systems.
3
.5. Catalytic activity
4. Conclusions
The CO hydrogenation to methanol was also studied
in this work. The catalytic activity of ternary and doped In this work, the ternary and doped ternary catalysts were
-1
–1
ternary catalysts expressed in g CH OH kg cat
h
prepared using co-precipitation, deposition-precipitation
3
are presented in Fig. 5. Carbon monoxide conversion and wet impregnation methods and tested in
a
and selectivity to methanol and other reaction products methanol synthesis reaction. XRD analysis confirmed
obtained in the studied reaction are shown in Table 3. the low crystrallinity of all samples that suggest a high
From the activity results we can easily observe that dispersion of copper species on the catalyst surface.
the highest methanol formation and carbon monoxide The reduction measurements suggested an interaction
conversion (15%) had ternary catalysts promoted by between copper species and promoters like Au or Pd
palladium. A little bit lower activity exhibited copper as evidenced by the reduction effects visible on the
catalyst. It is worth noticing that the addition of TPR curve. Additionally, it is worth noticing that those
palladium and gold improves the selectivity of ternary interactions may play a crucial role in the methanol
copper catalyst. Both promoted catalysts exhibited synthesis reaction.
higher selectivity to methanol formation in comparison
The activity results performed for all systems in
to ternary catalyst. The differences in selectivity hydrogenation of CO showed that the highest yield
observed for CuZrAl and promoted palladium and gold in methanol formation exhibited 5%Pd/CuZrAl. The
2
11

Promoted ternary CuO-ZrO -Al O
3
2
2
catalysts for methanol synthesis
selectivity results can be explained by the differences
in acidity and reducibility of studied catalysts. The
Acknowledgements
catalytic systems which posses the highest amount Partially financed from grant number 0680/B/
of weak acidic centers (2%Au/CuZrAl and 5%Pd/ H03/2011/40 is gratefully acknowledged. Paweł
CuZrAl) exhibited highest methanol selectivity during Mierczyski is a participant of START Programme.
the reaction. These results could suggests that those
centres play an important role in the methanol synthesis
reaction. The highest methanol yield in the case of
5%Pd/ CuZrAl system is explain by spillover effect
between Pd and CuO.
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