- Email: [email protected]
The effect of chlorine in the hydrogenation of carbon monoxide to oxygenated products at elevated pressure on Rh and Ir on SiO2 and Al2O3
Applied Catalysis, 25 (1986) 43-50 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
THE EFFECT PRODUCTS
B.J.
OF CHLORINE
AT ELEVATED
Kip, F.W.A.
Laboratory
IN THE HYDROGENATION PRESSURE
Dirne,
MONOXIDE
TO OXYGENATED
ON Rh AND Ir ON SiO2 AND Al20B
J. van Grondelle
for Inorganic
Technology,
OF CARBON
43
Chemistry
and R. Prins
and Catalysis,
P.O. Box 513, 5600 MB Eindhoven,
Eindhoven
University
of
The Netherlands.
ABSTRACT The catalytic behaviour of silica- and alumina-supported rhodium and iridium catalysts in synthesis gas reaction at elevated pressures was investigated. Temperature programmed reduction and hydrogen chemisorption measurements were used to characterize the catalysts. Rhodium was more active than iridium and had a better selectivity to higher hydrocarbons and C -oxygenates. For rhodium on silica high oxo-selectivities were obtained {40X), while on chlorine containing alumina this selectivity was rather low. ljhen a chlorine-free metal precursor was used or when special pretreatments were applied to a RhCl /Al 0 catalyst, oxo-selectivities of rhodium on alumina were also rather high 33og3.3
INTRODUCTION The reaction ducts, most
of CO and H:, over group
such as alkanes,
interesting
supported
rhodium
reported
catalysts
or below.
Rh/ZnO
mainly
produced
and Rh/Si02 can &so
selectivities
assists
in shifting
produce
C2-oxygenates
up to 80%
equilibria
ana platinum
be of interest
the formation
Ichikawa
C2-oxygenates [8] at higher
while
was reported
Bhasin
pressures
and va-
pressures the main
and O'Connor
acetaldehyde
ob-
and acetic
( 7 i4Pa, high pressure side).
to produce
to also investigate
has been
selectivities
on Rh/La20S
(ethanol,
products
on
(2-41,used
at atmospheric
hydrocarbons.
to the oxygenated
large
iridium
Since
rhodium
amounts
can
of metha-
in synthesis
gas reac-
pressures.
The mechanism for the formation so far. Recently
methanol,
only produced
produce
oxides
being the
[l-7]. The activity
and found better
and Rh/MgO
that Rh/SiO2
tion at elevated
clusters,
pro-
investigations hydrocarbons
acid)
and promotors.
than on acidic
served
[9], it might
carbonyl
the latter
of oxygenated
oxides
was ethanol
nol
metal
on the support
a wide range of
In recent
and acetic
on basic
product
acid) with
markedly
to support
oxygenates
acetaldehyde
yields
hydrocarbons,
point of view.
a large percentage
ethanol,
depended
rious oxides towards
and oxygenated
from an economical
~methanol,
selectivity
olefins
VIII metals
Takeuchi
of methanol
0166-983~/86~$03.60
Q
of oxygenated
and Katzer takes
products
[lOI and Tamaru
has not been elucidated
et al.
place by hydrogenation
1986 Eisevier Science Publishers B.V.
[ll] demonstrated
of nondissociatively
that adsorbed
44
carbon monoxide. According
to Matson
and Somorjai
the active sites for this reaction are metal chanisms have been proposed. Takeuchi chanism
involving
CO insertion
and oxygenates
supports
!l] and Tamaru
et al.
in CHx-Rh"+
pressure
the catalytic
(4 MPa)
been studied.
of A1203-
Special
on the support
after
sors. This chlorine metal ions present
a colon
in which
leading
and SiO2-supported
of catalysts
influence
in the reduced
prepared
catalyst
for
of hydrocarbons
hand Van den Berg et al. monoxide
insertion
In this mechanism
intermediate. gas reaction
rhodium
the acidity
me-
in an adsor-
C2-intermediate
carbon
and iridium
has been paid to the effect
reduction
me-
a complicated
to C2-oxygenates.
have a common
~121,
different
resulting
distribution
behaviotir in synthesis
attention
might
species
[14]. On the other
a mechanism
place,
and C2-oxygenates
In this work,
indicating
this conclusion
takes
[13] suggested
carbene
The Schulz-Flory
[7] proposed
intermediates
CI-hydrocarbons
and Katzer
thus
and C2-oxygenates.
et al.
ions, For C2-oxygenates
into adsorbed
bed ketene or oxirette intermediate, C2-hydrocarbons
15-61 and Driessen
catalysts
of chlorine
with metal
of the catalyst
and therefore
at elevated has
remaining
chloride
precur-
and the amount
the catalytic
of
behaviour.
EXPERIMENTAL Catalyst
preparation
Catalysts
were
prepared
by the incipient
Rh(tl03}3.xH20, H2IrC16.xH20,
IrC13.xH20
wetness
technique
using
RhCl3exH20,
in aqueous solution. -1 SiO2 from Grace (Type S.D. Z-324.382, surface area 290 m* g , pore volume 1.2 -1 ml g-l) and y-Al 0 from Ketjen (Type OOO-1.5E, surface area 200 m2 g , pore -P 3 volume 0.6 ml g ) were used as support material. Impregnated catalysts were dried rate 2 K min -I)* some catalysts
in air at 395 K for 16 h {heating air at 723 I( for 2 h. In-situ pressure
reactor
reduction
in pure hydrogen
Reducibility
of the catalysts
at 0.1 MPa, using
between 298 K and 623 K, and holding
Characterization
and Ir(N03j3.xH2O
min-l),
measurements
was studied
described
room temperature,
obtained
for 0.6 h.
extensively
performed
purified
by temperature-programmed
desorption
by extrapolating
admission
were measured
higher
Reduction
glass
was hydrogen
system
at 298 K.
rate 8 K
at 473 K and cooling
at room temperature.
amount
pressure
reduction
Volumetric
for 1 h at 673 K (heating
[17] the total
the linear
to zero pressure.
[15-Z].
in a conventional
hydrogen
isotherms
and Boudart
in ref.
rate of 5 K min_I,
at 673 K for 0.5 h, hydrogen
of Benson
of the isotherm
were
in flowing
evacuation
the method
in
out in a high -1 ramp of 6 K min
techniques of the catalysts
(TPR) using the apparatus
After reduction
a temperature
that final t~perature
done in a flow of 4% H2 in Ar at a heating chemisorption
were calcined
was carried
of chemisorbed
region
to
Following
H atoms was
(0.02 < P < 0.1 MPa)
45
The CO-H2 reaction Hydrogenation steel
ofcarbon
high pressure
(see catalyst
out in a continuous
in-situ
was cooled
were measured
of CO was around
under
was adjusted
was analyzed
T (0.6 m) in series Analytical
CO
conditions
temperature
effluent
out with a Nelson
temperature
an additional
the same reaction
2.0 5. The reactor
was carried
flow stainless-
of the catalysts
stabilisation
The reaction
102 (3 m) and Porapack
integration
reduction
down to the reaction
level. After
1 1-I h-I, HZ/CO = 3, P = 4 MPa).
with Chromosorb
K. Peak area
reactor. the reactor
All catalysts
so that conversion a column
After
with H2 to the desired
flow was started, (GHSV = 4000
fixed-bed
preparation),
and pressurized
carried
monoxidewas
using
operated
at 423
Interface-
IBM PC
configuration,
RESULTS
AND DISCUSSION
Characterization tiydrogen chemisorption well dispersed alumina-supported H/Rh=1.6 exceed
measurements
(H/Ir=0.7
for 2.5 wt%
systems
were even highly
for 1.5 wt% Rh) as shown
unity,
it is impossible
chemisorption
data and use
the H/M values
the reduction
473
I
573
Temperature
TPR profiles
(a) ~hCl3~Al*O~. (e) IrClj/SiO2.
catalysts
catalysts
673
dispersed
particle
of the H/M ratios
frequencies.
from
Therefore
dispersions. in Figure
at significant
catalysts.
Figure
higher
1. The reduction temperatures
l-c shows that when
773 Temperature
catalysts
dried
2 fl3. (c) Rh(N~3)3/A~~O3. calcined
were
for 2.5 wtE$ Ir and
sizes and dispersions
are presented
occurred
of impregnated
(b) IrCl$Al
(H/fr=1.7
turnover
(K)
(f) RhC13/A1203,
systems
for 1.5 wt.% Rh), and that the
1 and 2. Since most
for calculating
of the alu~lina-supported
I
1
to calculate
these
of several
of the silica-supported
FIGURE
in Tables
were only used to compare
The TPR profiles
373
show that the silica-supported Ir and H/Rh=0.6
(X)
at 393 E for 16 h. (d) RhClS,'Si02.
at 723 K, 2 h.
than a
46 metal-nitrate
precursor
sing a huge hydrogen reduction reduce
for which
reduction
The CO-H2
reaction
The catalytic synthesis
0.5%
during
TPR was complete
properties
between
RhC13/A1203
l-1) mainly
produced
115:. The ethers
are believed
while
after
deactivation
constant
served
in activity pressure.
methane,
synthesis rature
Since
it is capable
kedly alter Poutsma while
et al.
study suggest conditions
dimethylether,
of alcohols a marked
ethanol,
on aci-
deactivation
a small and constant
increased
at 383 K before catalyst.
during
the first
in-situ
reduction,
To obtain
by Vannice
the formation of synthesizing There
an acti-
different
and higher
he measured
selectivity.
hydrocarbons,
while
was 11%. The chain-growth
dissociate
catalysts.
CO catalyze
CO non-dissociatively
(i.e. Cu, Pd and Pt)[ZO].
of both alcohols
is no consensus
adsorb
CO more
between
adsorption
than
The results
Ir. Vannice
Rh and Ir is caused
activity
Ru
from CO and H2.
about
CO nondissociatively
easily
The ob-
at room tenpe-
can nar-
iridium.
of carbon monoxide
adsorption.
C2-
hydrocarbon
small effects
in literature
It
probabi-
Rh lies between
and hydrocarbons
both types of compounds,
that both Rh and Ir partly
in activity
[18], although
a completely
that adsorb
dissociative
and that Rh dissociates
than Ir/A1203.
on the basis of the CO dissociation
non-dissociative
[211 reported
active
than for the iridium
that easily
of methanol
[ZO] reported
that the difference
showed
is 15 times more
for the rhodium
be explained
its selectivity.
van den Berg
reduction
catalyst
dimethylether
[19]. Metals
synthesis
and Pd and catalyzes
dried
also showed
(i.e. Ru and Fe), metals
catalyze
Ir,
The total oxo-selectivity
might
metals
in-situ
by dehydratation
from the rhodium
was also reported
Ir/A1203
to be higher
differences
and above
at different
The total oxo-selectivity
oxo-selectivity
that Rh/Al,O,
methanol,
were absent.
of transition
tested
in
the reaction temperature had to be in-1 a value of 100 kJ mol for the total activation energy [l,
to 593 K. Using
lity was found
in the are shown
4 h.
(2.5 wt%
to that of the rhodium
produced
sample,
conditions)
were
hours of reaction
hours all catalysts
significantly
it can be calculated
oxygenates
hydrocarbons.
the first
after about
catalyst
2-l) differed
at atmospheric only
catalysts
but also some methanol,
(O-Z% h-I). Total
The H21rC16/A1203
This difference
catalysts
11 h time on stream
5% (differential
to be formed
several
7,181,
below
and higher
was observed,
creased
to completely RhC13/A1203
and iridium
after
analysis),
methane,
During
vity similar
cauthat
506 and 633 K.
acetaldehyde
hours and became
the TPR-run,
be sufficient
rhodium
conditions
product
dic sites of the support.
cf. Table
will
(1.5 wt% Rh), dried at 383 K for 16 h before
ethylmethylether,
relative
during
it can be concluded
only at 773 K.
of the various
at standard
for accurate
reduces
except may be for the calcined
1 and 2. To keep the conversion
temperatures
was
consumption.
gas reaction
(necessary
(Table
also
From these experiments
at 6'23 K for 0.5 h in pure hydrogen
the Rh and Ir catalysts,
Tables
the nitrate
is used,
on Ir,
of the present under reaction
[18] suggested
by a difference
in heat
TABLE
1
CO + H2 reaction no. catalyst
over various
1.5 wt% rhodium
systemb
catalysts
H/Rh
supported
Acti-
vityC
G-i4
on Al,_&
Selectivity
(agild
c;e
t0t.g
toLf C,,-OH
I
RhC13/Al2031,
1.8 mol % Cl
2
RhCl3/Si02j,
3
R~~N~~)~/~~~~~
4
WN0+&/A1203,
calcined
5
Rh(~O3)3/Al2~3,
calcined
1.6
2.3
72.0
0.6
0.6
1.3
0.6
at 723 K
1.6
at 723 K
16.3
3.5
48.0
11.3
45.4
14.4
1.8
50.8
1.4
0.9
61.3
0.4
1.1
1.6
2.6
, 1.8 mol % Cl 1.6
0.2 mol ?; Cl
HCl treated, Rh(N03)3/Si02k
7
RhCl3/A1203,
4% H201
8
RhC13/A1203,
1% H20
9
RhC13/Al203,
1% H20, heating rate
reduction
ICI RhC13/A1203, reduction,
tot. h
&-OH
0x0
3.7
11.1
26.7
14.0
40.7
27.5
11.1
38,6
11.9
19.5
14.1
35.3
24.9
9.3
8.0
11.7
44.2
7.1
35.6
13.1
48.6
63.9
4.1
14.7
14.8
29.5
1.5
72.8
15.3
4.9
4.9
11.9
2.2
60.1
7.3
16.0
12.6
30.8
1.3
4.0
57.0
5.8
9.5
17.0
29.6
1.6
3.1
65.7
4.7
13.1
12.1
26.4
1.6
1.9
60.1
14.7
8.5
11.9
22.0
1.4 mol % Cl
5
during
and Sig,a
30 K min -1, 1.5
H20 injection
1.6 5 Cl
SlOl
during
0.9 mol C: Cl
II
RhC13/A12ff3, calcined
12
RhCQW203,
calcined,
reduction
at 723 K
ia) Treact = tal).
523 K, unless
(c) Activity
stated
in mmole
(e) C += C 2+C 3+C 4 hydrocarbons. (g) t:t.C2-OH (i) dried
= $-OH
in-situ
628 #. (I> Treact
of adsorption
lyst,
much
better,
thylether
even though
The observed ported
formed
catalysts.
might
XPS showed
heating
rate 5 K min
content.
The surface
Table
f C2=0.
= 623 K. (k) Treact
(RhC73/Si02,
for Rh around
temperature
=
amounts
in oxo-selectivity
reduction
a was
disfavours
formation
ethanol
and ethylme-
Rh/Ali03
of
W-41%. between
the alumina-
in chlorine
of the dried
contained
and silica-sup-
content
RhCl3/A~203
, 0.5 h at 623 K) there was a large difference
of the reduced
cata-
its oxo-selectivity
dimethylether,
be due to the difference
that after
-1
at 383 K for 16 h
up to 623 # to obtain
high temperature
of methanol,
kJ m01-~}.
than the 1.5 wt% Rh/Al2~3
had to be increased
thermodynamically
185
1.5 wt% Rh, dried
1-2) was less active
and total oxo-selectivity
difference
Rh catalyst
efficiency.
+ I/3 C2-O-Cl.
+ tot.C2-OH
(j) Treact
In spite of this high temperature,
Considerable were
210 kJ mol -I,
around
Rh catalyst
reduction,
conversion.
oxygenates.
= tot.C1-OH
reduction.
(see experimen-
by carbon
= 506 K*
since the reaction
comparable
reduction
= Cl-OH + CI-O-CI
jh) tot.oxo
at 383 K, I6 h before
of CO {for Ir
in-situ
(b) standard
(f) tot.C1-OH
+ Z/3 C2-O-Cl.
The silica-supported before
otherwise,
CO (mole Rh) -I s -I. (d) calculated
of the reduced
and RhCl3/SjO2 in chlorine
1.8 1~01%Cl, whereas
the
48 TABLE
2
CO + H2 reaction no. catalyst
over various
iridium
catalysts
wt%
systema
supported
H/Ir
Ir 1
H21rC16/A1203e
2
H21rC16/A1203,
4% H20, ligating
rate reduction
30 K min
on A1203
and SiO2.
Temp.
Acti-
Selectivity
(K)
vityb
CH4
CT+
(%)' tot.oxod
2.5
1.7
593
2.5
73.2
15.6
11.2
2.5
--
591
1.8
69.1
18.4
12.5
3
IrC13/A1203, 4% H20, heating rate reduction 30 K min -1
2.6
--
563
3.6
58.8
22.6
18.6
4
Ir(N03)3/A1203
1.3
1.2
598
0.8
64.5
17.7
17.8
72.6
16.3
11.1
70.4
19.8
9.8
5
IrC13/Si02
2.5
0.7
633
1.0
6
Ir(N03)3/Si02
1.0
0.6
633
0.9
(a) Reduced converted
in pure H2, heating
CI-OH + Cl-0-CI.
surface
rate 5 K min-I,
CO (mole Ir) -I s-I. (c) Calculated (e) dried
of the reduced
this chlorine lyst showed
effect,
in-situ
Rh/Si02 A1203
a dispersion
was impregnated
catalyst
before
amount
Thus, when
to about
dried
lectivity.
a catalyst
before
procedure
before
(Table
in an increased
were
higher
not formed
synthesis
a relatively
activity
with gaseous
a dramatic
without was in-
gas reaction Normal
can
decrease
in the oxo-se-
and acetaldehyde
(Table
were
for-
oxo-selecti-
l-6) also resulted
investigations
showed
has an important reduction
623 K) of a rather wet RhC13/A1203
with
HCl at 423 K in
at all and the total
Further
low
Rh(N03)3/A1203
than the 10% obtained
Rh(N03)3
l-7,8,9,10,11,12).
l-3). This cata-
to C2-oxygenates
dimethylether
of SiO, with
investigate
is used, the oxo-selectivity
l-5) caused
of methanol,
Impregnation
, final temperature
and containing
influence
(heating
(stored
in
that the on
rate 5 K
for half a year
4 wt% H20) resulted
in a high oxo-selectivity (30%). RhC13/A1203 only -1 (1% H 0) and reduced at 5 K min showed a low oxo-selectivity 2 -1 reduction of this catalyst at 30 K min improved the oxo-selectivity
for one week
(12%), while
to 31%. Reduction jection Table
(Table
(Table
of the dried
Rh(NO,),/Al,O3
with a high oxo-selectivity-(49%).
pretreatment
stored
precursor
the calcined
reduction
Rh(N03)3
the selectivity
significantly
and ethylmethylether
the oxo-selectivity
-1
a chlorine-free
Only small amounts
ethanol
l-4) resulted
=
reduction.
to that of RhC13,
(39%). Calcination
(35%), while
Treating
vity was only 12%.
min
(Table
40% on Rh/A1203,
RhC13/A1203.
IV2 atmosphere
med,
reduction
loss of oxo-selectivity
creased.
with
in mole
(d) tot.oxo
only 0.1 mol% Cl. To further
(H/Rh = 1.3) comparable
and a high oxo-selectivity
efficiency.
at 383 K, 16 h before
contained
activity
much
0.5 h at 623 K (b) Activity
by carbon
l-10). These
tion of RhC13/A1203 plained
of a dried
in the reactor
during
results
RhC13/A1203 reduction)
indicate
is an important
by differences
in metal
in the presence also
increased
that the water factor.
dispersions
of water
vapour
The observed
vapour
(water
the oxo-selectivity pressure differences
as can be seen in Table
during
in-
(30%, the reduc-
can not be ex1. RhC13/A1203,
49
calcined tively
at 723 K for 2 h followed
high oxo-selectivity
somewhat
lower oxo-selectivity
caused
For the alumina-supported were
smaller.
Reduction
oxo-selectivity higher
the presence
During
by a decreased catalysts
that the
effect
precursor
iridium
gives
catalysts
catalysts
can be understood
catalyst,
an a
in
of 13% and 19% (Table
of iridium
of the RhC13/A1203
623
(Table 2-4) showed
containing
in oxo-selectivities
chlorine
observed
the reduction
l-12).
in oxo-selectivity
the chlorine-free
on SiO, the oxo-selectivities
a
(Table
, final temperature
Ir(N03),/A1203
of the chlorine
resulted
selectivity
at 5 K min
also for iridium
vapour
CI-OH
l-11) had a rela-
at 723 K showed
the differences -1
H21rC16/A1203
Reduction
of water
However,
We think way.
of 18%. Thus,
at 623 K (Table
of this catalyst
in 11% oxo-selectivity.
oxo-selectivity.
2-2,3).
iridium
of dried
K (Table 2-l) resulted
by reduction
(26%), reduction
were
low (10%).
in the following
the following
reactions
take
place: RhC13
+ 1.5 H2
2 Al-OH Al-D
+ Al-0
+ HCl
When the reduction
of RhClj
<--->
Rh
+ 3 HCl
<--->
Al-0
+ Al-O
<--->
Al-Cl + Al-OH
water
rhodium
vapour
pressure
the trapping reduction
shifts
were
the second
might
can be trapped
equilibrium
surface
of the catalyst
be given
next to
chloride
a high
to the left and thus prevents
no chlorine
increased
OH-groups
by the alumina
of the metal
was trapped
as shown by the XPS measurements.
and therefore
explanations
of alumina
the reduction
On Si02 almost
chlorides
high. Calcination
the chlorine
Several
(3). During
of the chlorine.
of the metal
selectivities removed
particles
(2) (3)
(1) and the dehydroxylation
(2) take place at the same time, the chloride the reduced
(I) t H20
before
during
the
Therefore
reduction
oxo-
probably
the oxo-selectivity.
for the observed
influence
of chlorine
on the
0x0-selectivity: - Secondary might
reactions
decompose
hydrocarbons favours
are favoured
the decomposition
- The different different
- C2-oxygenates
to methanol might
ning on the support
Ir/A1203.
ether,
(which
Chlorine
Once oxygenates
increases
and the presence
is supposed
catalyst
are formed,
they
(thermodynamically this acidity
and thus
of chlorine
might
on metal
ions
that have a structure
atom of the support
particles
after
cause
and thus cause different
to be formed
by intermediates
one oxygen
of these
[5-6,121). like acetate
[7]. The chlorine
reduction
remai-
of the RhC13 may
intermediates.
was more
Rh catalysts
acetaldehyde
procedures
next to the rhodium
Rh/A12D3
role.
sites of the alumina
ions in the reduced
be formed with
the formation
In summary, than
on acidic
of oxygenates.
of metal
(CH3C-- 0 -; M) .. 0'
inhibit
play an important
over oxygenates).
pretreatment
amounts
selectivities
ions
might
to hydrocarbons
active
produced
and hydrocarbons,
and had a higher
methanol, while
chain-growth
dimethylether,
Ir catalysts
ethanol,
produced
probability ethylmethyl-
only methanol,
50 dimethylether surface, genates vapour
and hydrocarbons.
Chlorine,
formed by dehydroxylation in the hydrogenation
pressure
trapping
of the metal
and high oxo-selectivities
nation of the RhC13/Al203
by vacancies disfavoured
on the alumina
the formation
of CO. On SiO2 this effect was not observed.
during the reduction
of chlorine
trapped
of OH-groups,
chloride
on alumina
were measured
of oxyHigh water
prevented
the
in that case. Calci-
system caused removal of the chlorine,
resulting
in high
0x0-selectivities. The negative Possibly
influence
chlorine
of chlorine
enhances
on the activity
the formation
is not completely
of coke, or alternatively
understood.
it covers
part
of the active metal area. Although described
the influences
in literature,
study demonstrates metal
catalysts
the pretreatments
of several
supports
the here observed
that, in comparing
for CO hydrogenation
[Z-6,9] and promotors
[3] have been
effect has not been mentioned
the catalytic the influence
activity
yet. Our
and selectivity
of the metal
of
salt precursor
and
should be taken into account.
ACKNOWLEDGEMENTS This research
was supported
(SON) with financial Pure Research
by the Netherlands
aid from the Netherlands
(ZWO). The authors
Foundation
Organization
for Chemical
Research
for the Advancement
thank Dr. J.W. Niemantsverdriet
for recording
of the
XPS spectra.
REFERENCES
9 :: 12
:: 15 16 17 18 19 20 21
F.G.A. van den B,erg, J.H.E. Glezer and W.M.H. Sachtler, J. Catal., 93 (1985) 340. M. Ichikawa, Bull. Chem. Sot. Jap., 51 (1978) 2268. M. Ichikawa, Bull. Chem. Sot. Jap., 51 (1978) 2273. M. Ichikawa, J.C.S. Chem. Comm., (1978) 566. P.R. Watson and G.A. Somorjai, J. Catal., 72 (1981) 347. P.R. Watson and G.A. Somorjai, J. Catal., 74 (1982) 282. H. Orita, S. Naito and K. Tamaru, J. Catal., 90 (1984) 183. M.M. Bhasin and G.L. O'Connor, Belgian Pattent 824822, to Union Carbide Corp., 1975. M. Ichikawa and K. Shikakura, Proc. 7th Int. Congr. Catal., Tokyo (1980) 925. A. Takeuchi and J.R. Katzer, J. Phys. Chem., 85 (1981) 937. Y. Kobori, H. Yamasaki, S. Naito, T. Onishi and K. Tamaru, Chem. Lett. (1983) 553. J.M. Driessen, E.K. Poels, J.P. Hindermann and V. Ponec, J. Catal., 82 (1983) 20. A. Takeuchi and J.R. Katzer, J. Phys. Chem., 86 (1983) 2438. A. Takeuchi, J.R. Katzer and R.W. Crecely, J. Catal., 82 (1983) 479. H. Boer, W.J. Boersma and N. Wagstaff, Rev. Sci. Instr., 53 (1982) 439. T.. Huizinga, J. van Grondelle and R. Prins, Appl. Catal., 10 (1984) 199. J.E. Benson and M. Boudart, J. Catal., 4 (1965) 704. M.A. Vannice, J. Catal., 37 (1975) 462. J.R. Katzer,.A.W. Sleight, PI Gajardo, J.B. Michel, E.F. Gleason and S. McMillan Far. Disc. Chem. Sot., 72 (1981) 121. L. Poutsma, L.F. Elek, P.A. Ibarbia, A.P. Risch and J.A. Rabo, J. Catal., 52 (1978) 157. F.G.A. van den Berg, Thesis, Leiden University (1983).
’
THE EFFECT PRODUCTS
B.J.
OF CHLORINE
AT ELEVATED
Kip, F.W.A.
Laboratory
IN THE HYDROGENATION PRESSURE
Dirne,
MONOXIDE
TO OXYGENATED
ON Rh AND Ir ON SiO2 AND Al20B
J. van Grondelle
for Inorganic
Technology,
OF CARBON
43
Chemistry
and R. Prins
and Catalysis,
P.O. Box 513, 5600 MB Eindhoven,
Eindhoven
University
of
The Netherlands.
ABSTRACT The catalytic behaviour of silica- and alumina-supported rhodium and iridium catalysts in synthesis gas reaction at elevated pressures was investigated. Temperature programmed reduction and hydrogen chemisorption measurements were used to characterize the catalysts. Rhodium was more active than iridium and had a better selectivity to higher hydrocarbons and C -oxygenates. For rhodium on silica high oxo-selectivities were obtained {40X), while on chlorine containing alumina this selectivity was rather low. ljhen a chlorine-free metal precursor was used or when special pretreatments were applied to a RhCl /Al 0 catalyst, oxo-selectivities of rhodium on alumina were also rather high 33og3.3
INTRODUCTION The reaction ducts, most
of CO and H:, over group
such as alkanes,
interesting
supported
rhodium
reported
catalysts
or below.
Rh/ZnO
mainly
produced
and Rh/Si02 can &so
selectivities
assists
in shifting
produce
C2-oxygenates
up to 80%
equilibria
ana platinum
be of interest
the formation
Ichikawa
C2-oxygenates [8] at higher
while
was reported
Bhasin
pressures
and va-
pressures the main
and O'Connor
acetaldehyde
ob-
and acetic
( 7 i4Pa, high pressure side).
to produce
to also investigate
has been
selectivities
on Rh/La20S
(ethanol,
products
on
(2-41,used
at atmospheric
hydrocarbons.
to the oxygenated
large
iridium
Since
rhodium
amounts
can
of metha-
in synthesis
gas reac-
pressures.
The mechanism for the formation so far. Recently
methanol,
only produced
produce
oxides
being the
[l-7]. The activity
and found better
and Rh/MgO
that Rh/SiO2
tion at elevated
clusters,
pro-
investigations hydrocarbons
acid)
and promotors.
than on acidic
served
[9], it might
carbonyl
the latter
of oxygenated
oxides
was ethanol
nol
metal
on the support
a wide range of
In recent
and acetic
on basic
product
acid) with
markedly
to support
oxygenates
acetaldehyde
yields
hydrocarbons,
point of view.
a large percentage
ethanol,
depended
rious oxides towards
and oxygenated
from an economical
~methanol,
selectivity
olefins
VIII metals
Takeuchi
of methanol
0166-983~/86~$03.60
Q
of oxygenated
and Katzer takes
products
[lOI and Tamaru
has not been elucidated
et al.
place by hydrogenation
1986 Eisevier Science Publishers B.V.
[ll] demonstrated
of nondissociatively
that adsorbed
44
carbon monoxide. According
to Matson
and Somorjai
the active sites for this reaction are metal chanisms have been proposed. Takeuchi chanism
involving
CO insertion
and oxygenates
supports
!l] and Tamaru
et al.
in CHx-Rh"+
pressure
the catalytic
(4 MPa)
been studied.
of A1203-
Special
on the support
after
sors. This chlorine metal ions present
a colon
in which
leading
and SiO2-supported
of catalysts
influence
in the reduced
prepared
catalyst
for
of hydrocarbons
hand Van den Berg et al. monoxide
insertion
In this mechanism
intermediate. gas reaction
rhodium
the acidity
me-
in an adsor-
C2-intermediate
carbon
and iridium
has been paid to the effect
reduction
me-
a complicated
to C2-oxygenates.
have a common
~121,
different
resulting
distribution
behaviotir in synthesis
attention
might
species
[14]. On the other
a mechanism
place,
and C2-oxygenates
In this work,
indicating
this conclusion
takes
[13] suggested
carbene
The Schulz-Flory
[7] proposed
intermediates
CI-hydrocarbons
and Katzer
thus
and C2-oxygenates.
et al.
ions, For C2-oxygenates
into adsorbed
bed ketene or oxirette intermediate, C2-hydrocarbons
15-61 and Driessen
catalysts
of chlorine
with metal
of the catalyst
and therefore
at elevated has
remaining
chloride
precur-
and the amount
the catalytic
of
behaviour.
EXPERIMENTAL Catalyst
preparation
Catalysts
were
prepared
by the incipient
Rh(tl03}3.xH20, H2IrC16.xH20,
IrC13.xH20
wetness
technique
using
RhCl3exH20,
in aqueous solution. -1 SiO2 from Grace (Type S.D. Z-324.382, surface area 290 m* g , pore volume 1.2 -1 ml g-l) and y-Al 0 from Ketjen (Type OOO-1.5E, surface area 200 m2 g , pore -P 3 volume 0.6 ml g ) were used as support material. Impregnated catalysts were dried rate 2 K min -I)* some catalysts
in air at 395 K for 16 h {heating air at 723 I( for 2 h. In-situ pressure
reactor
reduction
in pure hydrogen
Reducibility
of the catalysts
at 0.1 MPa, using
between 298 K and 623 K, and holding
Characterization
and Ir(N03j3.xH2O
min-l),
measurements
was studied
described
room temperature,
obtained
for 0.6 h.
extensively
performed
purified
by temperature-programmed
desorption
by extrapolating
admission
were measured
higher
Reduction
glass
was hydrogen
system
at 298 K.
rate 8 K
at 473 K and cooling
at room temperature.
amount
pressure
reduction
Volumetric
for 1 h at 673 K (heating
[17] the total
the linear
to zero pressure.
[15-Z].
in a conventional
hydrogen
isotherms
and Boudart
in ref.
rate of 5 K min_I,
at 673 K for 0.5 h, hydrogen
of Benson
of the isotherm
were
in flowing
evacuation
the method
in
out in a high -1 ramp of 6 K min
techniques of the catalysts
(TPR) using the apparatus
After reduction
a temperature
that final t~perature
done in a flow of 4% H2 in Ar at a heating chemisorption
were calcined
was carried
of chemisorbed
region
to
Following
H atoms was
(0.02 < P < 0.1 MPa)
45
The CO-H2 reaction Hydrogenation steel
ofcarbon
high pressure
(see catalyst
out in a continuous
in-situ
was cooled
were measured
of CO was around
under
was adjusted
was analyzed
T (0.6 m) in series Analytical
CO
conditions
temperature
effluent
out with a Nelson
temperature
an additional
the same reaction
2.0 5. The reactor
was carried
flow stainless-
of the catalysts
stabilisation
The reaction
102 (3 m) and Porapack
integration
reduction
down to the reaction
level. After
1 1-I h-I, HZ/CO = 3, P = 4 MPa).
with Chromosorb
K. Peak area
reactor. the reactor
All catalysts
so that conversion a column
After
with H2 to the desired
flow was started, (GHSV = 4000
fixed-bed
preparation),
and pressurized
carried
monoxidewas
using
operated
at 423
Interface-
IBM PC
configuration,
RESULTS
AND DISCUSSION
Characterization tiydrogen chemisorption well dispersed alumina-supported H/Rh=1.6 exceed
measurements
(H/Ir=0.7
for 2.5 wt%
systems
were even highly
for 1.5 wt% Rh) as shown
unity,
it is impossible
chemisorption
data and use
the H/M values
the reduction
473
I
573
Temperature
TPR profiles
(a) ~hCl3~Al*O~. (e) IrClj/SiO2.
catalysts
catalysts
673
dispersed
particle
of the H/M ratios
frequencies.
from
Therefore
dispersions. in Figure
at significant
catalysts.
Figure
higher
1. The reduction temperatures
l-c shows that when
773 Temperature
catalysts
dried
2 fl3. (c) Rh(N~3)3/A~~O3. calcined
were
for 2.5 wtE$ Ir and
sizes and dispersions
are presented
occurred
of impregnated
(b) IrCl$Al
(H/fr=1.7
turnover
(K)
(f) RhC13/A1203,
systems
for 1.5 wt.% Rh), and that the
1 and 2. Since most
for calculating
of the alu~lina-supported
I
1
to calculate
these
of several
of the silica-supported
FIGURE
in Tables
were only used to compare
The TPR profiles
373
show that the silica-supported Ir and H/Rh=0.6
(X)
at 393 E for 16 h. (d) RhClS,'Si02.
at 723 K, 2 h.
than a
46 metal-nitrate
precursor
sing a huge hydrogen reduction reduce
for which
reduction
The CO-H2
reaction
The catalytic synthesis
0.5%
during
TPR was complete
properties
between
RhC13/A1203
l-1) mainly
produced
115:. The ethers
are believed
while
after
deactivation
constant
served
in activity pressure.
methane,
synthesis rature
Since
it is capable
kedly alter Poutsma while
et al.
study suggest conditions
dimethylether,
of alcohols a marked
ethanol,
on aci-
deactivation
a small and constant
increased
at 383 K before catalyst.
during
the first
in-situ
reduction,
To obtain
by Vannice
the formation of synthesizing There
an acti-
different
and higher
he measured
selectivity.
hydrocarbons,
while
was 11%. The chain-growth
dissociate
catalysts.
CO catalyze
CO non-dissociatively
(i.e. Cu, Pd and Pt)[ZO].
of both alcohols
is no consensus
adsorb
CO more
between
adsorption
than
The results
Ir. Vannice
Rh and Ir is caused
activity
Ru
from CO and H2.
about
CO nondissociatively
easily
The ob-
at room tenpe-
can nar-
iridium.
of carbon monoxide
adsorption.
C2-
hydrocarbon
small effects
in literature
It
probabi-
Rh lies between
and hydrocarbons
both types of compounds,
that both Rh and Ir partly
in activity
[18], although
a completely
that adsorb
dissociative
and that Rh dissociates
than Ir/A1203.
on the basis of the CO dissociation
non-dissociative
[211 reported
active
than for the iridium
that easily
of methanol
[ZO] reported
that the difference
showed
is 15 times more
for the rhodium
be explained
its selectivity.
van den Berg
reduction
catalyst
dimethylether
[19]. Metals
synthesis
and Pd and catalyzes
dried
also showed
(i.e. Ru and Fe), metals
catalyze
Ir,
The total oxo-selectivity
might
metals
in-situ
by dehydratation
from the rhodium
was also reported
Ir/A1203
to be higher
differences
and above
at different
The total oxo-selectivity
oxo-selectivity
that Rh/Al,O,
methanol,
were absent.
of transition
tested
in
the reaction temperature had to be in-1 a value of 100 kJ mol for the total activation energy [l,
to 593 K. Using
lity was found
in the are shown
4 h.
(2.5 wt%
to that of the rhodium
produced
sample,
conditions)
were
hours of reaction
hours all catalysts
significantly
it can be calculated
oxygenates
hydrocarbons.
the first
after about
catalyst
2-l) differed
at atmospheric only
catalysts
but also some methanol,
(O-Z% h-I). Total
The H21rC16/A1203
This difference
catalysts
11 h time on stream
5% (differential
to be formed
several
7,181,
below
and higher
was observed,
creased
to completely RhC13/A1203
and iridium
after
analysis),
methane,
During
vity similar
cauthat
506 and 633 K.
acetaldehyde
hours and became
the TPR-run,
be sufficient
rhodium
conditions
product
dic sites of the support.
cf. Table
will
(1.5 wt% Rh), dried at 383 K for 16 h before
ethylmethylether,
relative
during
it can be concluded
only at 773 K.
of the various
at standard
for accurate
reduces
except may be for the calcined
1 and 2. To keep the conversion
temperatures
was
consumption.
gas reaction
(necessary
(Table
also
From these experiments
at 6'23 K for 0.5 h in pure hydrogen
the Rh and Ir catalysts,
Tables
the nitrate
is used,
on Ir,
of the present under reaction
[18] suggested
by a difference
in heat
TABLE
1
CO + H2 reaction no. catalyst
over various
1.5 wt% rhodium
systemb
catalysts
H/Rh
supported
Acti-
vityC
G-i4
on Al,_&
Selectivity
(agild
c;e
t0t.g
toLf C,,-OH
I
RhC13/Al2031,
1.8 mol % Cl
2
RhCl3/Si02j,
3
R~~N~~)~/~~~~~
4
WN0+&/A1203,
calcined
5
Rh(~O3)3/Al2~3,
calcined
1.6
2.3
72.0
0.6
0.6
1.3
0.6
at 723 K
1.6
at 723 K
16.3
3.5
48.0
11.3
45.4
14.4
1.8
50.8
1.4
0.9
61.3
0.4
1.1
1.6
2.6
, 1.8 mol % Cl 1.6
0.2 mol ?; Cl
HCl treated, Rh(N03)3/Si02k
7
RhCl3/A1203,
4% H201
8
RhC13/A1203,
1% H20
9
RhC13/Al203,
1% H20, heating rate
reduction
ICI RhC13/A1203, reduction,
tot. h
&-OH
0x0
3.7
11.1
26.7
14.0
40.7
27.5
11.1
38,6
11.9
19.5
14.1
35.3
24.9
9.3
8.0
11.7
44.2
7.1
35.6
13.1
48.6
63.9
4.1
14.7
14.8
29.5
1.5
72.8
15.3
4.9
4.9
11.9
2.2
60.1
7.3
16.0
12.6
30.8
1.3
4.0
57.0
5.8
9.5
17.0
29.6
1.6
3.1
65.7
4.7
13.1
12.1
26.4
1.6
1.9
60.1
14.7
8.5
11.9
22.0
1.4 mol % Cl
5
during
and Sig,a
30 K min -1, 1.5
H20 injection
1.6 5 Cl
SlOl
during
0.9 mol C: Cl
II
RhC13/A12ff3, calcined
12
RhCQW203,
calcined,
reduction
at 723 K
ia) Treact = tal).
523 K, unless
(c) Activity
stated
in mmole
(e) C += C 2+C 3+C 4 hydrocarbons. (g) t:t.C2-OH (i) dried
= $-OH
in-situ
628 #. (I> Treact
of adsorption
lyst,
much
better,
thylether
even though
The observed ported
formed
catalysts.
might
XPS showed
heating
rate 5 K min
content.
The surface
Table
f C2=0.
= 623 K. (k) Treact
(RhC73/Si02,
for Rh around
temperature
=
amounts
in oxo-selectivity
reduction
a was
disfavours
formation
ethanol
and ethylme-
Rh/Ali03
of
W-41%. between
the alumina-
in chlorine
of the dried
contained
and silica-sup-
content
RhCl3/A~203
, 0.5 h at 623 K) there was a large difference
of the reduced
cata-
its oxo-selectivity
dimethylether,
be due to the difference
that after
-1
at 383 K for 16 h
up to 623 # to obtain
high temperature
of methanol,
kJ m01-~}.
than the 1.5 wt% Rh/Al2~3
had to be increased
thermodynamically
185
1.5 wt% Rh, dried
1-2) was less active
and total oxo-selectivity
difference
Rh catalyst
efficiency.
+ I/3 C2-O-Cl.
+ tot.C2-OH
(j) Treact
In spite of this high temperature,
Considerable were
210 kJ mol -I,
around
Rh catalyst
reduction,
conversion.
oxygenates.
= tot.C1-OH
reduction.
(see experimen-
by carbon
= 506 K*
since the reaction
comparable
reduction
= Cl-OH + CI-O-CI
jh) tot.oxo
at 383 K, I6 h before
of CO {for Ir
in-situ
(b) standard
(f) tot.C1-OH
+ Z/3 C2-O-Cl.
The silica-supported before
otherwise,
CO (mole Rh) -I s -I. (d) calculated
of the reduced
and RhCl3/SjO2 in chlorine
1.8 1~01%Cl, whereas
the
48 TABLE
2
CO + H2 reaction no. catalyst
over various
iridium
catalysts
wt%
systema
supported
H/Ir
Ir 1
H21rC16/A1203e
2
H21rC16/A1203,
4% H20, ligating
rate reduction
30 K min
on A1203
and SiO2.
Temp.
Acti-
Selectivity
(K)
vityb
CH4
CT+
(%)' tot.oxod
2.5
1.7
593
2.5
73.2
15.6
11.2
2.5
--
591
1.8
69.1
18.4
12.5
3
IrC13/A1203, 4% H20, heating rate reduction 30 K min -1
2.6
--
563
3.6
58.8
22.6
18.6
4
Ir(N03)3/A1203
1.3
1.2
598
0.8
64.5
17.7
17.8
72.6
16.3
11.1
70.4
19.8
9.8
5
IrC13/Si02
2.5
0.7
633
1.0
6
Ir(N03)3/Si02
1.0
0.6
633
0.9
(a) Reduced converted
in pure H2, heating
CI-OH + Cl-0-CI.
surface
rate 5 K min-I,
CO (mole Ir) -I s-I. (c) Calculated (e) dried
of the reduced
this chlorine lyst showed
effect,
in-situ
Rh/Si02 A1203
a dispersion
was impregnated
catalyst
before
amount
Thus, when
to about
dried
lectivity.
a catalyst
before
procedure
before
(Table
in an increased
were
higher
not formed
synthesis
a relatively
activity
with gaseous
a dramatic
without was in-
gas reaction Normal
can
decrease
in the oxo-se-
and acetaldehyde
(Table
were
for-
oxo-selecti-
l-6) also resulted
investigations
showed
has an important reduction
623 K) of a rather wet RhC13/A1203
with
HCl at 423 K in
at all and the total
Further
low
Rh(N03)3/A1203
than the 10% obtained
Rh(N03)3
l-7,8,9,10,11,12).
l-3). This cata-
to C2-oxygenates
dimethylether
of SiO, with
investigate
is used, the oxo-selectivity
l-5) caused
of methanol,
Impregnation
, final temperature
and containing
influence
(heating
(stored
in
that the on
rate 5 K
for half a year
4 wt% H20) resulted
in a high oxo-selectivity (30%). RhC13/A1203 only -1 (1% H 0) and reduced at 5 K min showed a low oxo-selectivity 2 -1 reduction of this catalyst at 30 K min improved the oxo-selectivity
for one week
(12%), while
to 31%. Reduction jection Table
(Table
(Table
of the dried
Rh(NO,),/Al,O3
with a high oxo-selectivity-(49%).
pretreatment
stored
precursor
the calcined
reduction
Rh(N03)3
the selectivity
significantly
and ethylmethylether
the oxo-selectivity
-1
a chlorine-free
Only small amounts
ethanol
l-4) resulted
=
reduction.
to that of RhC13,
(39%). Calcination
(35%), while
Treating
vity was only 12%.
min
(Table
40% on Rh/A1203,
RhC13/A1203.
IV2 atmosphere
med,
reduction
loss of oxo-selectivity
creased.
with
in mole
(d) tot.oxo
only 0.1 mol% Cl. To further
(H/Rh = 1.3) comparable
and a high oxo-selectivity
efficiency.
at 383 K, 16 h before
contained
activity
much
0.5 h at 623 K (b) Activity
by carbon
l-10). These
tion of RhC13/A1203 plained
of a dried
in the reactor
during
results
RhC13/A1203 reduction)
indicate
is an important
by differences
in metal
in the presence also
increased
that the water factor.
dispersions
of water
vapour
The observed
vapour
(water
the oxo-selectivity pressure differences
as can be seen in Table
during
in-
(30%, the reduc-
can not be ex1. RhC13/A1203,
49
calcined tively
at 723 K for 2 h followed
high oxo-selectivity
somewhat
lower oxo-selectivity
caused
For the alumina-supported were
smaller.
Reduction
oxo-selectivity higher
the presence
During
by a decreased catalysts
that the
effect
precursor
iridium
gives
catalysts
catalysts
can be understood
catalyst,
an a
in
of 13% and 19% (Table
of iridium
of the RhC13/A1203
623
(Table 2-4) showed
containing
in oxo-selectivities
chlorine
observed
the reduction
l-12).
in oxo-selectivity
the chlorine-free
on SiO, the oxo-selectivities
a
(Table
, final temperature
Ir(N03),/A1203
of the chlorine
resulted
selectivity
at 5 K min
also for iridium
vapour
CI-OH
l-11) had a rela-
at 723 K showed
the differences -1
H21rC16/A1203
Reduction
of water
However,
We think way.
of 18%. Thus,
at 623 K (Table
of this catalyst
in 11% oxo-selectivity.
oxo-selectivity.
2-2,3).
iridium
of dried
K (Table 2-l) resulted
by reduction
(26%), reduction
were
low (10%).
in the following
the following
reactions
take
place: RhC13
+ 1.5 H2
2 Al-OH Al-D
+ Al-0
+ HCl
When the reduction
of RhClj
<--->
Rh
+ 3 HCl
<--->
Al-0
+ Al-O
<--->
Al-Cl + Al-OH
water
rhodium
vapour
pressure
the trapping reduction
shifts
were
the second
might
can be trapped
equilibrium
surface
of the catalyst
be given
next to
chloride
a high
to the left and thus prevents
no chlorine
increased
OH-groups
by the alumina
of the metal
was trapped
as shown by the XPS measurements.
and therefore
explanations
of alumina
the reduction
On Si02 almost
chlorides
high. Calcination
the chlorine
Several
(3). During
of the chlorine.
of the metal
selectivities removed
particles
(2) (3)
(1) and the dehydroxylation
(2) take place at the same time, the chloride the reduced
(I) t H20
before
during
the
Therefore
reduction
oxo-
probably
the oxo-selectivity.
for the observed
influence
of chlorine
on the
0x0-selectivity: - Secondary might
reactions
decompose
hydrocarbons favours
are favoured
the decomposition
- The different different
- C2-oxygenates
to methanol might
ning on the support
Ir/A1203.
ether,
(which
Chlorine
Once oxygenates
increases
and the presence
is supposed
catalyst
are formed,
they
(thermodynamically this acidity
and thus
of chlorine
might
on metal
ions
that have a structure
atom of the support
particles
after
cause
and thus cause different
to be formed
by intermediates
one oxygen
of these
[5-6,121). like acetate
[7]. The chlorine
reduction
remai-
of the RhC13 may
intermediates.
was more
Rh catalysts
acetaldehyde
procedures
next to the rhodium
Rh/A12D3
role.
sites of the alumina
ions in the reduced
be formed with
the formation
In summary, than
on acidic
of oxygenates.
of metal
(CH3C-- 0 -; M) .. 0'
inhibit
play an important
over oxygenates).
pretreatment
amounts
selectivities
ions
might
to hydrocarbons
active
produced
and hydrocarbons,
and had a higher
methanol, while
chain-growth
dimethylether,
Ir catalysts
ethanol,
produced
probability ethylmethyl-
only methanol,
50 dimethylether surface, genates vapour
and hydrocarbons.
Chlorine,
formed by dehydroxylation in the hydrogenation
pressure
trapping
of the metal
and high oxo-selectivities
nation of the RhC13/Al203
by vacancies disfavoured
on the alumina
the formation
of CO. On SiO2 this effect was not observed.
during the reduction
of chlorine
trapped
of OH-groups,
chloride
on alumina
were measured
of oxyHigh water
prevented
the
in that case. Calci-
system caused removal of the chlorine,
resulting
in high
0x0-selectivities. The negative Possibly
influence
chlorine
of chlorine
enhances
on the activity
the formation
is not completely
of coke, or alternatively
understood.
it covers
part
of the active metal area. Although described
the influences
in literature,
study demonstrates metal
catalysts
the pretreatments
of several
supports
the here observed
that, in comparing
for CO hydrogenation
[Z-6,9] and promotors
[3] have been
effect has not been mentioned
the catalytic the influence
activity
yet. Our
and selectivity
of the metal
of
salt precursor
and
should be taken into account.
ACKNOWLEDGEMENTS This research
was supported
(SON) with financial Pure Research
by the Netherlands
aid from the Netherlands
(ZWO). The authors
Foundation
Organization
for Chemical
Research
for the Advancement
thank Dr. J.W. Niemantsverdriet
for recording
of the
XPS spectra.
REFERENCES
9 :: 12
:: 15 16 17 18 19 20 21
F.G.A. van den B,erg, J.H.E. Glezer and W.M.H. Sachtler, J. Catal., 93 (1985) 340. M. Ichikawa, Bull. Chem. Sot. Jap., 51 (1978) 2268. M. Ichikawa, Bull. Chem. Sot. Jap., 51 (1978) 2273. M. Ichikawa, J.C.S. Chem. Comm., (1978) 566. P.R. Watson and G.A. Somorjai, J. Catal., 72 (1981) 347. P.R. Watson and G.A. Somorjai, J. Catal., 74 (1982) 282. H. Orita, S. Naito and K. Tamaru, J. Catal., 90 (1984) 183. M.M. Bhasin and G.L. O'Connor, Belgian Pattent 824822, to Union Carbide Corp., 1975. M. Ichikawa and K. Shikakura, Proc. 7th Int. Congr. Catal., Tokyo (1980) 925. A. Takeuchi and J.R. Katzer, J. Phys. Chem., 85 (1981) 937. Y. Kobori, H. Yamasaki, S. Naito, T. Onishi and K. Tamaru, Chem. Lett. (1983) 553. J.M. Driessen, E.K. Poels, J.P. Hindermann and V. Ponec, J. Catal., 82 (1983) 20. A. Takeuchi and J.R. Katzer, J. Phys. Chem., 86 (1983) 2438. A. Takeuchi, J.R. Katzer and R.W. Crecely, J. Catal., 82 (1983) 479. H. Boer, W.J. Boersma and N. Wagstaff, Rev. Sci. Instr., 53 (1982) 439. T.. Huizinga, J. van Grondelle and R. Prins, Appl. Catal., 10 (1984) 199. J.E. Benson and M. Boudart, J. Catal., 4 (1965) 704. M.A. Vannice, J. Catal., 37 (1975) 462. J.R. Katzer,.A.W. Sleight, PI Gajardo, J.B. Michel, E.F. Gleason and S. McMillan Far. Disc. Chem. Sot., 72 (1981) 121. L. Poutsma, L.F. Elek, P.A. Ibarbia, A.P. Risch and J.A. Rabo, J. Catal., 52 (1978) 157. F.G.A. van den Berg, Thesis, Leiden University (1983).
’