Production of hydrogen from dimethyl ether on supported Au catalysts

Article abstract of DOI:10.1016/j.apcata.2010.04.054

The adsorption and reactions of dimethyl ether (DME) were investigated on Au nanoparticles supported by various oxides and carbon Norit. Infrared spectroscopic and temperature programmed desorption studies revealed that DME adsorbs readily on most oxidic supports. A limited dissociation of DME to methoxy species was established on Au particles by IR spectroscopy. As regards the formation of hydrogen, Au/CeO₂ is the most effective catalyst. On Au/Al₂O₃ catalyst the main process was the formation of methanol with a very small amount of hydrogen. Deposition of Au on CeO ₂-Al₂O₃ mixed oxide resulted in a very active catalyst for H₂ production. The yield for H₂ in the reforming of DME approached the value of 73% at 723-773 K. This feature was explained by the hydrolysis of DME to methanol on alumina, and the fast decomposition of methanol at the Au/CeO₂ interface. Adding potassium promoter to Au/CeO₂-Al₂O₃ catalyst further enhanced the production of hydrogen as indicated by the increase of the yield to ～87%. No deactivation of the catalyst was experienced at 773 K for the measured time, ～10 h.

Full text of DOI:10.1016/j.apcata.2010.04.054

Applied Catalysis A: General 391 (2011) 360–366
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Production of hydrogen from dimethyl ether on supported Au catalysts
∗
A. Gazsi, I. Ugrai, F. Solymosi
Reaction Kinetics Research Group, Chemical Research Centre of the Hungarian Academy of Sciences, Department of Physical Chemistry and Materials Science,
University of Szeged, P.O. Box 168, H-6701 Szeged, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
The adsorption and reactions of dimethyl ether (DME) were investigated on Au nanoparticles supported
by various oxides and carbon Norit. Infrared spectroscopic and temperature programmed desorption
studies revealed that DME adsorbs readily on most oxidic supports. A limited dissociation of DME to
methoxy species was established on Au particles by IR spectroscopy. As regards the formation of hydro-
gen, Au/CeO2 is the most effective catalyst. On Au/Al2O3 catalyst the main process was the formation of
methanol with a very small amount of hydrogen. Deposition of Au on CeO2–Al2O3 mixed oxide resulted in
a very active catalyst for H2 production. The yield for H2 in the reforming of DME approached the value of
Received 17 February 2010
Received in revised form 31 March 2010
Accepted 26 April 2010
Available online 5 May 2010
Keywords:
IR spectra of adsorbed dimethyl ether
Decomposition of dimethyl ether
Reforming of dimethyl ether
Hydrogen production
Au catalyst
7
3% at 723–773 K. This feature was explained by the hydrolysis of DME to methanol on alumina, and the
fast decomposition of methanol at the Au/CeO2 interface. Adding potassium promoter to Au/CeO2–Al2O3
catalyst further enhanced the production of hydrogen as indicated by the increase of the yield to ∼87%.
No deactivation of the catalyst was experienced at 773 K for the measured time, ∼10 h.
© 2010 Elsevier B.V. All rights reserved.
CeO2 support
1
. Introduction
A great effort is being made nowadays to develop catalytic pro-
Recently it was demonstrated that the gold metal also catalyses
the decomposition and reforming of methanol [21–28] and ethanol
[
[
29,30]. The highest yield for hydrogen was obtained on Au/CeO2
27,30].
cesses for the generation of hydrogen [1,2]. Ethanol and methanol
are the most generally used materials. However, an increasing
interest can be observed in the use of dimethyl ether (DME), which
also contains a large amount of hydrogen, and appears to be a
suitable compound for the source of hydrogen. DME possesses sev-
eral advantageous properties and applications. It is considered as
an alternative fuel replacing diesel, as its burning produces much
less pollutant [3–5]. In the last decade, several catalytic reactions
of DME including its combustion, dehydrogenation, hydrolysis,
selective oxidation, transformation to hydrocarbons [6] and even
aromatization have been studied [7]. As it is non-toxic, thus more
preferable compared to methanol to use it as a hydrogen carrier for
fuel cells. The decomposition and reforming of DME to hydrogen
were also investigated on various catalysts [8–18]. The more effec-
tive ones are the Pt metals, which are able to rupture the C–C bond.
An alternative solution for the use of cheaper but less active cata-
lyst is to apply a composite catalyst [16,18]. In this way we were
2. Experimental
2.1. Materials and preparation of the catalysts
The following compounds were used as supports. CeO2 (ALFA
2
2
AESAR, 50 m /g), Al2O3 (Degussa P 110 C1, 100 m /g), MgO (DAB 6,
2
2
2
170 m /g), TiO2 (Degussa P25, 50 m /g), SiO2 (CAB-O-SiL, 198 m /g)
and activated carbon Norit (ALFA AESAR, 859 m /g). Carbon Norit
2
was purified by treatment with HCl (10%) for 12 h at room tempera-
ture. SupportedAucatalysts withagoldloading of1, 2 or5 wt%were
prepared by a deposition–precipitation method. HAuCl4·aq. (p.a.,
49% Au, Fluka AG) was first dissolved in triply distilled water. After
the pH of the aqueous HAuCl4 solution had been adjusted to 7.5
by the addition of 1 M NaOH solution, a suspension was prepared
with the finely powdered oxidic support, and the system was kept
at 343 K for 1 h under continuous stirring. The suspension was then
aged for 24 h at room temperature, washed repeatedly with dis-
tilled water, dried at 353 K and calcined in air at 573 K for 4 h. Similar
method was used for the preparation of Au/CeO2 + Al2O3. In this
case the oxide-mixture (1:1) was impregnated in the HAuCl4·aq.
solution. We mark this composite catalyst: “co-impregnated”. The
fragments of catalyst pellets were oxidized at 673 K and reduced
at 673 K for 1 h in situ. DME was the product of Gerling Holz +CO
able to enhance the catalytic activity of Mo C prepared on carbon
Norit in the production of H2 from DME [16].
In the present work we report the adsorption, decomposition
and reforming of DME on supported Au catalysts. Following the
pioneering work of Haruta et al. [19] the supported Au nanoparti-
cles exhibited a surprisingly high activity in many reactions [20].
2
∗ Corresponding author. Tel.: +36 62 420 678; fax: +36 62 420 678.
E-mail address: fsolym@chem.u-szeged.hu (F. Solymosi).
(99.9%). Other gases were of commercial purity (Linde).
0
926-860X/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcata.2010.04.054

A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
361
2.2. Methods
3.2. Infrared spectroscopic measurements
Catalytic reactions were carried out at 1 atm in a quartz tube
8 mm id) that served as a fixed-bed, continuous flow reactor. The
Fig. 1A depicts the IR spectra of DME adsorbed on 1% Au/CeO2
(TR = 673 K) at 300 K and heated to different temperatures under
continuous degassing. At 300 K, intense absorption bands were
(
flow rate was in general 40 ml/min. The carrier gas was Ar, which
was mixed with DME at room temperature. The DME content was
approximately 10%. In general, 0.3 g of loosely compressed cata-
lyst sample was used. After reduction of the catalyst, the reactor
was flushed with argon for 15 min, and the sample was cooled in
an Ar flow to the lowest reaction temperature investigated. After
the Ar had been replaced by the reacting gas mixture, the reac-
tor was gradually heated to selected temperatures, at which the
gases were analyzed with an HP 5890 gas chromatograph fitted
with PORAPAK Q and PORAPAK S packed columns. In the study of
−
1
observed at 2955, 2894, 2883, and 2838 cm and weaker bands or
−
1
shoulders appeared at ∼2999 and 2923 cm in the C–H stretching
region. In the low-frequency range, absorption bands were iden-
tified at 1583, 1519, 1473, 1457, 1375, 1315, 1253, 1158, 1071
−
1
and 1035 cm . Heating the sample caused the attenuation of all
the bands. Virtually identical spectra were measured following the
adsorption of DME on pure CeO . The difference is that the absorp-
2
tion bands were more stable than those identified on Au/CeO2.
Similar spectral features were found for Au/Al O3 with a very
2
the reaction of DME + H O mixtures of different compositions, the
slight deviation in the position of the bands. The results obtained
for Au/SiO2 deserve special mention. The advantage of this sam-
ple is that DME adsorbs only weakly and non-dissociatively on
silica and it may therefore be expected that the vibration bands
observed at higher temperatures are due to the species attached
to Au particles. In order to eliminate the absorption bands arising
from weakly adsorbed DME, the adsorbed layer was heated to 473 K
under continuous degassing. The TPD experiments (see next sec-
tion) indicated that this treatment is sufficient for the desorption
of DME. The IR spectrum for pure SiO2 contained no detectable
spectra features after this treatment. In the presence of 5% Au
2
reactants were introduced into an evaporator with the aid of an
infusion pump (MEDICOR ASSISTOR PCI flow rate: 0.3 ml liquid/h):
the evaporator was flushed with an Ar flow (36 ml/min). The DME or
DME + H O mixture containing Ar flow entered the reactor through
2
an externally heated tube in order to avoid condensation. The con-
version of DME was calculated by taking into account the amount
consumed.
FTIR spectra of adsorbed DME were recorded with a BioRad
−
1
FTS-155 spectrometer with a wavenumber accuracy of ± 4 cm
.
The spectrum of the sample after the reduction step was used
as background. Thermal desorption measurements (TPD) were
carried out in the catalytic reactor. The catalysts were treated
with DME/Ar containing 10% DME at ∼300 K for 60 min, and then
flushed with Ar for 30 min. The TPD was carried out in an Ar
flow (20 ml/min) with a ramp at ∼2 K/min from ∼300 to ∼900 K.
Desorbing products were analyzed by gas chromatography. Trans-
mission electron microscopy (TEM) images were taken with a
Philips CM 20 and a Morgagni 268 D electron microscope at 300 K.
Approximately 1 mg of catalyst was placed on a TEM grid. X-ray
photoelectron spectroscopy (XPS) images were taken with a Kratos
−
1
absorption bands appeared at 2958, 2925, 2912, and 2859 cm
at 373 K, which attenuated after evacuation of the sample at higher
temperature. Nevertheless, most of them can be identified even
after heat-treatment at 473–573 K. No peaks were detected below
−
1
1300 cm due to the low transmittance of SiO . IR spectra are dis-
2
played in Fig. 1B. Table 1 lists the characteristic vibrations of DME
and its possible dissociation products on different solids.
3.3. Thermal desorption measurement
XSAM 800 instrument, using non-monochromatic Al K␣ radiation
TPD spectra for the various products after the adsorption of
DME on the Au catalysts at ∼300 K are presented in Fig. 2. For
1% Au/CeO2 the release of adsorbed DME started slightly above
◦
(
hv = 1486.6 eV) and a 180 hemispherical analyzer at a base pres-
−9
sure of 1 × 10 mbar.
3
H
00 K and peaked at ∼370 K. At Tp = 560–580 K, the desorption of
and CH4 was detected. A very small amount of ethane des-
2
3
. Results
orption between 480 and 560 K was also observed (Fig. 2A). Very
similar TPD spectra were registered for pure CeO . The desorp-
2
3
.1. Characterization of Au samples
tion of DME from 1% Au/Al O3 occurred with a Tp ∼ 370 and 510 K.
2
In addition, the release of methanol (Tp = 510 K), H , CO and CH
2
4
The sizes of Au nanoparticles were measured with an elec-
with identical peak temperatures, Tp ∼ 650 K was also identified
tron microscope. We obtained the following values: 2–3 nm for 1%
Au/CeO , 3–4 nm for 1% Au/SiO , 6–7 nm for 1% Au/TiO , 5–6 nm
for 1% Au/Norit and 6–7 nm for 1% Au/Al O . The XP spectra of sup-
ported Au catalysts used in the present work have been previously
determined [30]. The spectrum for the oxidized 1% Au/CeO2 sam-
(
Fig. 2B). When DME was adsorbed on 1% Au/CeO –Al O catalyst
2
2
3
2
2
2
(co-impregnated), the desorption of DME (Tp ∼ 380 and 500 K), CO
2
3
and H (Tp ∼ 590 K) was registered (Fig. 2C). From 2% Au/SiO only
2
2
the desorption of DME (Tp = 350 K) was observed.
ple in the Au 4f
region showed that most of the Au was in the
7
/2
3.4. Catalytic studies
+
3+
Au and Au states. After reduction of the sample at 673 K, the
3+
0
intensity of the BE for Au decreased and that of Au developed.
As concerns the XPS region of cerium in the oxidized catalyst, the
dominant peaks at 882.6 and 898.4 eV were due to Ce4 . The shoul-
ders at 885.1 and 900.4 eV, however, revealed the presence of Ce3
in the starting material [31–33]. This indicated that the deposition
of Au on the CeO2 leads to a partial reduction of the Ce4+ on the
surface. These features became more evident after the reduction of
the Au/CeO2 at higher temperatures. After the oxidation of the 2%
Au nanoparticles deposited on SiO , MgO and carbon Norit
exhibited very slight catalytic effect on the decomposition of DME.
Even at 773 K, the conversion was less than 2–3%. Somewhat higher
activity was measured on 1% Au/TiO sample, where an appreciable
decomposition occurred above 573 K, and the conversion attained
2
+
+
2
30% at 873 K. The products were CH , CH OH, H , CO and a very
4
3
2
small amount of C H . The yield of H formation, however, was very
2
6
2
low, less than 10% even at 773 K. 1% Au/CeO2 catalyst exhibited a
similar catalytic performance than the Au/TiO2 with the difference
that the percentage of H was much higher, 50–60% (Fig. 3A). How-
Au/SiO , the peaks in the Au 4f region demonstrated the presence
2
of Au3+ and Au . The reduction at 673 K increased the intensity of
+
2
0
the peak for Au , but, similarly as for 1% Au/CeO , did not eliminate
Au on the surface. On the oxidized Au/Norit sample, there were
2
ever due to the low conversion (∼20%) the yield of H was less than
2
+
1
5% even at 773 K. A disadvantageous property of Au/CeO2 is the
3
+
+
equal amounts of Au and Au . After reduction, the BE peak for
fast deactivation at 773 K. An increase of Au loading to 5% enhanced
only slightly the conversion of DME, which reached the value of
0
Au also appeared.

3
62
A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
Fig. 1. FTIR spectra following the adsorption of DME on 1% Au/CeO2 (A) and 1% Au/Al2O3 (B) at 300 K and after subsequent degassing at different temperatures. a, 300 K; b,
73 K; c, 423 K; d, 473 K.
3
∼
25% at 773 K. Note that pure CeO2 reduced at 673 K exhibited a
with alumina the selectivity for H2 above 600 K fell in the range
of 30–35% and the yield for H2 was 37% at 773 K. Higher values
for H2 production were obtained, when following the preparation
method Au was deposited on Al O –CeO mixed oxides. The selec-
very little activity, even at 773 K we measured only less than 1%
conversion. The situation was basically different on Al O -based
2
3
catalysts. On 1% Au/Al O3 the conversion of DME was about 80%
2
2
3
2
at 723 K and the total conversion was reached at 773 K, but the
production of hydrogen remained at low level in the whole tem-
perature range (Fig. 3B). At lower temperature methanol was the
main product. Above 673 K CH , CO, H2 and CH OH were deter-
tivity value for H2 was 35–40%, and the H2 yield exceeded a value
of 40% at 773 K. The product distribution is presented in Fig. 4A and
B, whereas the values for the selectivity and yields of H2 formation
are plotted in Fig. 5A and B.
4
3
mined in decreasing quantities. The yield of H2 did not exceed 20%
Adding water to DME (H O/DME = 1) exerted a dramatic influ-
2
even at 723–773 K. No deactivation of Au/Al O3 was observed in
ence on the product distribution. The amount of CH4 and CO
decreased and more hydrogen were produced (Fig. 4C and D). The
selectivity for H2 was almost 80%, while the yield for hydrogen
formation approached the value of 73% (Fig. 5C and D). Follow-
ing the reaction in time on stream at 773 K for 10 h we experienced
2
1
0 h at 773 K. Note that the pure Al O3 also exhibited relatively
2
high activity towards DME. The conversion was ∼68% at 723 K and
increased to ∼88% at 773 K. The product distribution was practi-
cally the same as measured for Au/Al O , but less hydrogen was
2
3
formed.
no deactivation. When H O/DME ratio was increased to 3, only a
2
Taking into account the results obtained for different catalysts,
an attempt was made to combine the advantageous catalytic prop-
erties of alumina- and ceria-supported Au. When 1% Au/CeO2 and
Al O was separated by glass wool, the extent of the decomposition
slight further enhancement was measured, occurred in the values
for hydrogen production.
In the study of the decomposition and reforming of ethanol [38]
and DME [16] on Mo C/Norit catalysts we found that the presence
2
3
2
of DME was ∼90% at 723 K and ∼100% at 773 K. The selectivity for H2
production scattered between 22 and 26% and the yield reached the
value of 23% at 773 K. When 1% Au/CeO2 was mechanically mixed
of potassium markedly promoted the formation of hydrogen. We
performed similar experiments in the present case. It appeared that
the addition of 1% potassium to 1% Au/CeO –Al O catalyst exerted
2
2
3
Table 1
Characteristic absorption bands of gaseous and adsorbed dimethyl ether and methanol on various solids.
Vibrational DME(g) [34,35]
mode
DME(a) Al2O3 at
150 K [35]
CH3O(a) Al2O3 at
150 K [35]
CH3O(a) CeO2 at DME(a) CeO2 at
CH3O(a) Rh/CeO2 DME(a) Au/CeO2 DME(a) Au/SiO2
523 K [36]
300 K [17]
at 300 K [17]
at 300 K [present at 373 K [present
study]
study]
ꢀ
a(CH3)
2996
925
2984
2922
2960
2849
2911
2953
2948
2955
2958
2925
2
ꢀ
2
s(CH3)
ı(CH3)
2817
2887
2821
2890
2803
2883
2841
2884
2838
2838
2889
2912
2859
ı(CH3)
1470
1477
1459
1475
1420
1434
1436
1463
1473
1457
1456
ꢁ
(CH3)
as(CO)
1244
1252
1116
1081
1229
1159
1253
1158
1179
1190
1095
ꢀ
1102
1092
1055
1108
1066
1071

A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
363
Fig. 2. TPD spectra following the adsorption of DME on 1% Au/CeO2 (A), 1% Au/Al2O3 (B), and 1% Au/CeO2 + Al2O3 (co-impregnated) (C) at 300 K.
a positive influence on the formation of hydrogen in the reforming
of DME. In this case we measured the highest yield (86–87%) for
hydrogen at 773 K. As shown in Fig. 6 this value remained unaltered
in time on stream in the measured time, ∼10 h.
perature. After the decomposition of DME on 1% Au/CeO + Al O
2 2 3
catalysts at 773 K for 15 h, the surface carbon reacted with
hydrogen only above 700 K, resulting in the formation of a
large amount of methane (Tp ≈ 830 K) and much less ethane
and ethylene (Tp = 705–730 K) (Fig. 7A). After reforming of DME
on the same catalyst under identical experimental conditions
we identified the production of same compounds, but in much
smaller quantities. The peak temperatures remained practically
unaltered (Fig. 7B). This result suggests that the water pre-
vents the deposition of carbonaceous species very likely reacting
3.5. TPR measurements
After completion of the catalytic experiments, TPR measure-
ments were carried out (Fig. 7). The amount and the reactivity of
the surface carbonaceous deposit depended on the reaction tem-
Fig. 3. Product distribution in the decomposition and reforming of DME on 1% Au/CeO2 (A) and 1% Au/Al2O3 (B) at different temperatures.

3
64
A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
Fig. 4. Product distribution of the decomposition of DME on 1% Au/CeO2 mixed with Al2O3 (A), 1% Au/CeO2 + Al2O3 (co-impregnated) (B) and reforming of DME on 1% Au/CeO2
mixed with Al2O3 (C), 1% Au/CeO2 + Al2O3 (co-impregnated) (D).
with the surface species yielding the carbon-containing mate-
rial.
DME were not found. On an oxygen-dosed surface, however,
methoxy species were clearly identified by HREEL spectroscopy
[
37].
We suppose that bulk Au should not be more reactive towards
4
. Discussion
DME than the Rh. The situation is, however, could be different on
gold nanoparticles, which may exhibit a much higher reactivity.
However, it is not easy to prove this expectation as most of the oxi-
dic supports can activate alone the adsorbed DME molecule. This is
illustrated by the identical IR spectra for pure and Au-containing
4.1. Interaction of DME with supported Au
The adsorption of DME with pure Au single crystal has not
been studied, yet. In the case of Rh(1 1 1) we found that DME
decreases the work function of the Rh maximum with 1.2 eV indi-
cating that adsorbed DME has a positive outward dipole moment
CeO . The situation is different on silica-supported Au as silica
2
is inert towards DME. TPD and FTIR measurements revealed that
DME adsorbs weakly and non-dissociatively on silica at 300 K: it
desorbs with a Tp = 373 K. Following the adsorption of DME on 5%
Au/SiO2 at 300 K weak absorption bands can be identified at 2958
[
37]. The vibrational modes of adsorbed DME on clean Rh(1 1 1)
corresponded well to the gas-phase values. From the analysis of
HREEL spectra of an annealed layer following DME adsorption at
−
1
and 2853 cm
(Fig. 1B), which we attribute to the vibration of
1
00 K, spectral features indicative of the dissociation of adsorbed
Fig. 5. The selectivity and yield of H2 formation in the decomposition (A and B) and reforming of DME (C and D) on 1% Au/CeO2 + Al2O3 catalyst. 1% Au/CeO2 and Al2O3 is
separated; (᭹) 1% Au/CeO2 mixed with Al2O3; (ꢀ) 1% Au/CeO2 + Al2O3 (co-impregnated).

A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
365
Fig. 6. Product distribution in the reforming of DME on 1% K + 1% Au/CeO2 + Al2O3 (co-impregnated) catalyst at different temperatures (A). The selectivity and yield of H2
formation in time on stream at 773 K (B).
methoxy species formed in the reaction
CH ) O = CH O + CH3(a)
methoxy from the ceria onto the Au, and its faster decomposition on
the metal. The development of the spectral features at 1583, 1375,
and 1315 cm are tentatively attributed to the formate formed in
the reaction on ceria
−
1
(
(1)
3
2
(a)
3
(a)
Accordingly, Au can promote the scission of one of the C–O bond
in DME resulting in Au–OCH surface complex. The vibration at
OH(a) + CO(a) = HCOO(a)
(2)
3
−1
2
925 cm is very likely due to the ꢀa of undissociated DME. This
absorption band was observed in the IR spectrum of gaseous DME
4.2. Reactions of DME
and also in that adsorbed DME on Al O3 at 150 K [34,35]. The more
2
intense absorption bands at around 2955, 2838, 2889, 1473, 1457,
In our previous studies it was found that the decomposition and
reforming of methanol and ethanol on supported Au nanoparticles
sensitively depends on the nature of the supports [27,30]. Au/CeO2
represented the most effective catalyst in both cases. The yield of
hydrogen production from methanol reached the value of 93% at
773 K. As the C–C bond cleavage in the adsorbed ethanol occurs to
−1
and 1071 cm established on CeO -based samples are also due to
2
methoxy species, very likely located on ceria. As there is no indi-
cation of the spectral feature determined for adsorbed CH3 species
[
39,40], it is very likely that it is attached to the oxygen atom of
CeO , also yielding a Ce–OCH surface compound. The effect of gold
2
3
in Au/CeO is manifested in the lower stability of the above absorp-
only a limited extent even on Au/CeO , the production of H2 from
2
2
tion bands, indicating the occurrence of the migration of adsorbed
ethanol was much less. This feature appeared in the present case,
Fig. 7. TPR spectra for 1% Au/CeO2 + Al2O3 (co-impregnated) after decomposition (A) and reforming (B) of DME at 773 K for 13 h.

3
66
A. Gazsi et al. / Applied Catalysis A: General 391 (2011) 360–366
when the rupture of C–C bond is probably the slowest step in the
(iv) The high activity is attributed to the easy formation of methanol
from DME on alumina and to the high reactivity of Au–CeO2
interface in the decomposition of methanol.
decomposition of DME Au/CeO : the conversion of DME remained
2
relatively at low level, around 20% even at 773 K (Fig. 3A). Never-
theless, concerning the production of hydrogen, Au/CeO exhibited
(v) Adding potassium to this catalyst promoted the production of
hydrogen.
2
the highest activity among the Au samples studied. In contrast,
on Au/Al O , which catalyzed effectively the conversion of DME
2
3
(
Fig. 3B), the main reaction pathway was basically different. The pri-
Acknowledgements
mary product was methanol, which suggests the occurrence of the
hydrolysis of DME with the participation of OH groups of alumina
This work was supported by OTKA under contract number NI
6
9327 and K 81517.
CH –O–CH
+ OH(a) = 2CH OH
(3)
3
3(g)
3
(g)
The use of CeO + Al O mixed oxide as a support for Au, how-
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high reactivity of Au–CeO2 interface in the activation and decom-
position of methanol [27]
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[
(
2
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3
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(
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2
2
3
erated the formation of hydrogen in the reforming of DME, which
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7
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2
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[
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2
activate these molecules resulting in higher rates of their reaction
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(
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(
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(
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