Note: Descriptions are shown in the official language in which they were submitted.
21~~(~8
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T 9091
PROCESS FOR THE CATALYTIC PARTIAL OXIDATION OF HYDROCARBONS
The present invention relates to a process for the catalytic
partial oxidation of of hydrocarbons, in particular a process for -
the preparation of a mixture of carbon monoxide and hydrogen from a
methane-containing feed, for example natural gas or associated gas.
The partial oxidation of hydrocarbons, for example methane or
natural gas, in the presence of a catalyst is an attractive route
for the preparation of mixtures of carbon monoxide and hydrogen,
known in the art as synthesis gas. The mixture so-produced may be
converted into valuable hydrocarbon products, for example fuels
boiling in the middle distillate range and hydrocarbon waxes, by
such processes as the Fischer-Tropsch synthesis well known in the
art. Alternatively, the mixture may be converted into products such
as methanol by synthesis processes equally well known in the art.
The optimum catalytic partial oxidation process for commercial
application would give high levels of conversion of the hydrocarbon
feedstock with a high level of selectivities to carbon monoxide and
hydrogen.
The literature contains a number of documents disclosing
details of experiments conducted into the catalytic partial
oxidation of hydrocarbons, in particular methane, employing a wide
range of catalysts. Typically, these catalysts have comprised an
active metal selected from Group VIII of the Periodic Table of the
Elements (CAS version as given in the Handbook of Chemistry and
Physics, 68th Edition) supported on a refractory oxide carrier, such
as alumina or silica.
Thus, European patent application publication No. 0 262 997
(EP-A-0 262 947) discloses a process for the catalytic partial
oxidation of methane using a catalyst comprising platinum and
chromium oxide supported on a refractory oxide carrier. The
catalyst specifically exemplified in EP-A-0 262 947 comprises silica
as the carrier material.
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A.T. Ashcroft, et al ("Selective oxidation of methane to
synthesis gas using transition metal catalysts", Nature, Vol. 344,
No. 6264. pp. 319 to 321, March 1990) disclose experiments conducted
using lanthanide ruthenium oxides of formula Ln2sn207 for the
partial oxidation of methane. A range of lanthanides were tested at
a temperature of 777°C, a gas hourly space velocity of 40000 h-1 and
a pressure of 1 atmosphere. It was concluded by the authors that,
under the prevailing process conditions, the active catalyst
comprised ruthenium metal supported on a metal oxide carrier.
Similarly, R.H. Jones, et al (°'Catalytic conversion of methane
to synthesis gas over europium iridate, Eu2Ir207", Catalysis
Letters 8 (1991) 169 to 174) describe the selective partial
oxidation of methane over the europium iridium pyrochlore, Eu2Ir207,
at a pressure of 1 atmosphere and at a temperature of 873 K (600°C).
IS The active catalyst was shown to comprise particles of iridium metal
supported on europium oxide. Similar results are disclosed by
P.D.F. Vernon, et al ("Partial oxidation of methane to synthesis
gas", Catalysis Letters 6 (1990) 181 to 18F, and Catalysis Today, 13
(1992) 417 to 426) for nickel, ruthenium, rhodium, palladium,
iridium and platinum, either supported on alumina carriers or
present as the metals in oxides derived from mixed oxide precursors.
More generally, United States Patent No. 5,149,464 (US-A-
5,149,464) is directed to a method for selectively oxygenating
methane to carbon monoxide and hydrogen by bringing the reactant gas
mixture at a temperature of about 650°C to 900°C into contact
with a
solid catalyst which is generally described as being either:
a) a catalyst of the formula MXM'yOz, where:
M is at least one element selected from Mg, B, A1, Ln, Ga, Si,
Ti, Zr and Hf; Ln is at least one member of lanthanum and the
lanthanide series of elements;
M' is a d-block transition metal,
and each of the ratios x/y and y/z and (x+y)/z is independently
from 0.1 to 8; or
b) an oxide of a d-block transition metal; or
c) a d-block transition metal on a refractory support; or
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d) a catalyst formed by heating a) or b) under the conditions of
the reaction or under non-oxidizing conditions.
The d-block transition metals are said in US-A-5,149,964 to be
selected from those having atomic number 21 to 29, 40 to 97 and 72
to 79, the metals scandium, titanium, vanadium, chromium, manganese,
iron, cobalt, nickel, copper, zirconium, niobium, molybdenum,
technetium, ruthenium, rhodium, palladium, silver, hafnium,
tantalum, tungsten, rhenium, osmium, iridium, platinum and gold. It
is stated in US-A-5,149,469 that the preferred metals are those in
Group VIII of the Periodic Table of the Elements, that is iran,
osmium, cobalt, rhenium, iridium, palladium platinum, nickel and
ruthenium.
The process described in US-A-5,199,464 is operated at a
temperature in the range of from 650°C to 900°C, with a range of
from
700°C to 800°C being preferred. A range of experiments are
described
in US-A-5,149,464 in which a variety of catalysts comprising Group
VIII metals were tested, including ruthenium oxide,
praesidium/ruthenium oxides, pyrochlores, ruthenium on alumina,
rhodium on alumina, palladium on alumina, platinum on alumina,
nickel/aluminium oxide, perovskites and nickel oxide.
A similar general disclosure of a catalyst for use in the
catalytic partial oxidation process is made in International Patent
Application publication No. WO 92/11199. WO 92/11199 specifically
discloses experiments in which catalysts comprising iridium,
palladium, ruthenium, rhodium, nickel and platinum supported on
alumina were applied. All the experiments were conducted under mild
process conditions, with typical conditions being a pressure of 1
atmosphere, a temperature of 1050 K (777°C) and a gas hourly space
velocity of about 20,000 /hr. In the text of WO 92/11199 it is
stated that extended life tests of the catalysts were underway, but
that most catalysts should be expected to show no deterioration in
activity after 80 hours, and possibly much longer.
Japanese patent application publication No. 58-207946 (JP-A-58-
207946) discloses a catalyst for the partial oxidation of
hydrocarbons, which catalyst comprises either a combination of an
s- s~ ~ ; r~ ~;
iv e.J ~ U
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alumina-magnesia spinel, cobalt aluminate, barium carbonate and
barium aluminate, or a combination of an alumina-magnesia spinel,
cobalt, cobalt oxide and barium aluminate. It is suggested in JP-A-
58-207946 that the catalyst is suitable for the partial oxidation of
hydrocarbons such as natural gas, methane, ethane, propane and
butane. However, the specification of JP-A-58-207946 is concerned
primarily with a process for producing cementation gas containing
carbon monoxide and hydrogen, for the surface hardening of steel.
In this respect, the examples of JP-A-58-0207946 are limited to the
partial oxidation of butane, yielding a mixture of carbon monoxide
and hydrogen having a hydrogen/carbon monoxide ratio of about 1.3.
The experiments were conducted at a space velocity of 12,000 hr-1
using as feed a mixture of air and butane, with the amount of air
being 1.025 times the theoretical amount required to oxidise butane
to carbon monoxide and hydrogen (that is an oxygen/carbon ratio of
0.51). There is no disclosure in JP-A-58-207946 of suitable
operating pressures for the partial oxidation process. It is stated
in JP-A-58-207946 that the catalysts allow the partial oxidation
process to be operated with a good efficiency at low temperatures,
that is below 1000°C. To this end, all the experiments testing the
catalysts Were conducted at 980°C.
Finally, International patent application publication No.
WO 93/01130 discloses a process for the partial oxidation of methane
using a catalyst comprising a platinum group metal and/or metal
oxide supported on a lanthanide oxide, and/or an oxide of a metal
from Group IIIB and/or an oxide of a metal from Group IVB of the
Periodic Table and/or alumina. A range of experiments are described
in WO 93/01130, in which catalysts consisting of palladium supported
on oxides of scandium, yttrium, lanthanum, titanium, zirconium,
hafnium, cerium, samarium, aluminium, silicon and mixed oxides of
barium/cerium and strontium/cerium. The experiments were conducted
at a temperature of 750°C and a gas hourly space velocity of
5000 hr-1 using a feed composition of 95~ methane : 5?s oxygen
55~ argon. No operating pressure is specified in WO 93/01130. The
results disclosed in WO 93/01130 show that, under the operating
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conditions selected, catalysts comprising carriers consisting of an
oxide of a metal from Groups IIIB or IVB of the Periodic Table,
aluminium and the lanthanide cerium exhibited a high selectivity to
carbon monoxide. In contrast, the results also show that catalysts
comprising as carrier samarium oxide, silica and the mixed oxides of
barium/cerium and strontium/cerium exhibited only very poor
selectivities to carbon monoxide, instead producing large quantities
of carbon dioxide.
As mentioned hereinbefore, an important commercial process is
the preparation of mixtures of carbon monoxide and hydrogen, which
mixture is then used as the feedstock for a hydrocarbon or organic
chemical synthesis process. The catalytic partial oxidation of
hydrocarbons is one possible method of carrying out this
preparation. However, to be commercially attractive, the process
IS would need to be able to operate at elevated pressures, for example
from 30 bare to 1S0 tiara, with very high gas hourly space
velocities, for example of the order of 1,000,000 N1/kg/hr. For
thermodynamic reasons, in order to obtain the necessary
selectivities to carbon monoxide and hydrogen, it is necessary to
operate the partial oxidation process at high temperatures.
Accordingly, for a partial oxidation process to be viable on.a
commercial scale, it is essential that the catalyst employed
maintains its level of activity and selectivity to the desired
products over the prolonged periods of operation demanded of
commercial processes.
Further, a most attractive mixture of carbon monoxide and
hydrogen for use as feedstock for a commercial synthesis process,
such as the Fischer-Tropsch synthesis of paraffins or the synthesis
of methanol, is a mixture having a hydrogen to carbon monoxide ratio
of about 2Ø Such a mixture may be prepared by the partial
oxidation of methane or methane-containing feeds, such as natural
gas or associated gas.
Thus, it can be seen that there is a need for a process for the
catalytic partial oxidation of methane or methane-containing feeds,
in which the catalyst retains a high level of activity and
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selectivity to both carbon monoxide and hydrogen under conditions of
high gas space velocity, elevated pressure and high temperature.
Most surprisingly, in contrast to the teachings of the prior art
documents, in particular WO 93/01130 it has been found that a
process in which catalysts comprising a metal selected from
Group VIII of the Periodic Table of the Elements supported on a
refractory oxide having at least two rations yields both carbon
monoxide and hydrogen under the aforementioned conditions in high
yields for prolonged periods of time.
Accordingly, the present invention provides a process for the
catalytic partial oxidation of a methane-containing feed, which
process comprises contacting a mixture of the feed and an oxygen
containing gas, which mixture has an oxygen to carbon ratio in the
range of from 0.3 to 0.8, at a temperature of greater than 900°C and
at elevated pressure with a catalyst comprising a metal selected
from Group VIII of the Periodic Table supported on a refractory
oxide having at least two rations.
The process of the present invention is suitable for the
preparation of a mixture of carbon monoxide and hydrogen from any
methane-containing feed. The feed may comprise substantially pure
methane. However, typical feeds will comprise methane in
combination with one or more other hydrocarbons and gases. The feed
preferably comprises methane in an amount of at least 50~ by volume,
more preferably at least 75$ by volume, especially at least 80$ by
volume. The methane may be in combination with other hydrocarbons,
for example light hydrocarbons having from 2 to 4 carbon atoms. The
process is particularly suitable for the partial oxidation of
natural gas and associated gas.
The feed is contacted with the catalyst as a mixture with an
oxygen-containing gas. Air is suitable for use as the oxygen-
containing gas. However, the use of substantially pure oxygen as
the oxygen-containing gas may be preferred. In this way, the need
for handling a large volume of inert gas, for example nitrogen when
using air as the oxygen-containing gas, is avoided. The feed may
optionally comprise steam.
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The methane-containing feed and the oxygen-containing gas are
mixed in such amounts as to give an oxygen-to-carbon ratio in the
range of from 0.3 to 0.8, more preferably, in the range of from 0.45
to 0.75. References to the oxygen-to-carbon ratio refer to the
ratio of oxygen in the form of molecules (02) to carbon atoms
present in the methane-containing feed. Preferably the oxygen-to-
carbon ratio is in the range of from 0.45 to 0.65, with oxygen-to-
carbon ratios in the region of the stoichiometric ratio of 0.5, that
is in a range of from 0.95 to 0.6, being especially preferred. If
steam is present in the feed, the steam-to-carbon ratio is
preferably in the range of from above 0.0 to 3.0, more preferably
from 0.0 to 2Ø The methane-containing feed, oxygen-containing gas
and steam, if present, are preferably well mixed prior to being
contacted with the catalyst.
The process of the present invention is operated at elevated
pressures, that is pressures significantly above atmospheric
pressure. The process may be operated at pressures in the range of
up to 150 bara. More preferably, the process is operated at
pressures in the range of from 5 to 100 bara, especially from 10 to
75 bara.
Under the conditions of high pressure prevailing in the
process, the feed must be contacted with the catalyst at high
temperatures in order to obtain the desired degree of conversion.
Accordingly, the mixture of methane-containing feed and oxygen-
containing gas are contacted with catalyst at a temperature greater
than 900°C, more preferably a temperature in the range of from 1000
to 1300°C, especially from 1000 to 1200°C. The methane-
containing
feed and the oxygen-containing gas are preferably preheated prior to
being contacted with the catalyst.
The mixture of the methane-containing feed and the oxygen-,
containing gas may be provided during the process at any suitable
space velocity. It is an advantage of the process of this invention
that very high gas space velocities can be achieved. Thus, typical
space velocities for the process (expressed as normal litres of gas
per kilogram of catalyst per hour) are in the range of from 20,000
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to 100,000,000 N1/kg/hr, more preferably in the range of from 50,000
to 50,000,000 N1/kg/hr. Space velocities in the range of from
500,000 to 30,000,000 N1/kg/hr are particularly suitable.
The catalyst employed in the process of the present invention
comprises a metal of Group VIII of the Periodic Table of the
Elements supported on a refractory oxide having at least two
cations. The catalyst has a structure arising from the deposition
of the Group VIII metal onto the refractory oxide support, for
example by means of such techniques as impregnation. Thus, the
catalysts comprise the Group VIII metal supported on the surface of
the refractory oxide support. This structure is to be contrasted
with the structure arising from the use of catalysts as described in
the prior art, in which a refractory oxide is applied directly in
the partial oxidation process, the prevailing conditions of which
reduce oxides present in the refractory material to the
corresponding metal, which metal is the catalytically active
species.
The catalyst comprises a metal of Group VIII of the Periodic
Table of the Elements, with a metal selected from ruthenium,
rhodium, palladium, osmium, iridium and platinum being preferred.
Catalysts comprising ruthenium, rhodium or iridium as the
catalytically active metal are especially preferred for use in the
process.
The Group VIII metal is supported on a refractory oxide
carrier, which refractory oxide comprises at least two cations. The
refractory oxide is preferably a binary or a ternary oxide,
consisting of two or three cations respectively, with binary oxides
being preferred. The two or more cations of the refractory oxide
are preferably each selected from Groups IA, IIA, IIIA and IVA of
the Periodic Table of the Elements or the transition metals. More
preferably, the two or more cations are each selected from Groups
IA, IIA, IIIA, IIIB, IVA and IVB and the lanthanides. A preferred
catalyst comprises a refractory oxide having at least one cation
selected from Groups IA, IIA and IIIB and the lanthanides and at
least one cation selected from Groups IIIA, IVA and IVB. More
_ g _
preferably, the catalyst comprises a refractory oxide having at
least one can on from Group IIA or IIIB and at least one cation from
Group IIIA or IVB. Barium is a particularly preferred cation
selected from Group IIA. Aluminium is a particularly preferred
cation selected from Group IIIA. Lanthanum is a most suitable
cation selected from Group IIIB. Zirconium is a most suitable
cation selected from Group IVB. One most suitable refractory oxide
for use as a support in the catalyst is a binary oxide of barium and
aluminium, in particular barium hexa-aluminate. A second most
suitable refractory oxide for use as a support in the catalyst is a
binary oxide of lanthanum and zirconium.
The refractory oxide materials for use as supports in the
catalysts are available commercially, or may be prepared by
techniques well known in the art.
The catalyst may be prepared using techniques well established
in the art, of which impregnation is a preferred technique. The
preparation of the catalyst by impregnation comprises contacting the
refractory oxide with a solution of a salt of the metal of Group
VIII of the Periodic Table. The thus impregnated refractory oxide
is then dried and calcined.
Any suitable reaction regime may be applied in 'the process of
the present invention in order~to contact the reactants with the
catalyst. One suitable regime is a fluidised bed, in which the
catalyst is employed in the form of particles fluidised by a stream
of gas. A preferred reaction regime for use in the process is a
fixed bed reaction regime, in which the catalyst is retained within
a reaction zone in a fixed arrangement. Particles of catalyst may
be employed in the fixed bed regime, retained using fixed bed
reaction techniques well known in the art. Alternatively, the
catalyst may be in the form of a foam, prepared, for example, by the
impregnation of a ceramic foam of the refractory oxide by the
techniques described hereinbefore. Suitable foams for use in the
preparation of the catalyst include those having from 30 to 150
pores per inch (12 to 60 pores per centimeter). Further,
alternative forms for the catalyst include refractory oxide
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honeycomb monolith structures.
In a preferred embodiment of the process of this invention, the
feed is contacted with a catalyst retained in a fixed bed
arrangement, Which arrangement has a high tortuosity. The term
'°tortuosity" is a common term in the art which, when referring to a
fixed catalyst bed, can be defined as the ratio of the length of the
path taken by a gas flowing through the bed to the length of the
shortest straight line path through the bed. Thus, the honeycomb
monolith structures have a tortuosity of 1Ø For the purposes of
the present invention, the term "high tortuosity" is a reference to
arrangements having a tortuosity substantially greater than that of
the honeycomb monolith structures, in particular a tortuosity of at
least 1.1. A fixed bed of catalyst particles typically has a
tortuosity of 1.5, whilst ceramic foams may be prepared having a
tortuosity in the range of from 3.0 to 4.0, or even higher. In
general, the tortuosity of the fixed bed arrangement is preferably
in the range of from 1.1 to 10.0, more preferably to 5Ø A most
suitable range of tortuosity is from 1.3 to 4Ø
It has been found that by employing the catalyst in a fixed bed
arrangement having a high tortuosity allows the required conversion
to be achieved with only a relatively very short contact time
between the reacting gases and the catalyst. In this way, only a
very low volume of catalyst is required, which in turn allows the
very high gas space velocities desirable for operating a commercial
process to be achieved.
The feed is preferably contacted with the catalyst under
adiabatic conditions. For the purposes of this specification, the
term '°adiabatic" is a reference to reaction conditions in which
substantially all heat loss and radiation from the reaction zone is
prevented, with the exception of heat leaving in the gaseous
effluent stream of the reactor.
In a further aspect, the present invention relates to carbon
monoxide or hydrogen whenever prepared by a process as hereinbefore
described.
The mixture of carbon monoxide and hydrogen prepared by the
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process of this invention is particularly suitable for use in the
synthesis of hydrocarbons, for example by means of the Fischer-
Tropsch synthesis, or the synthesis of oxygenates, for example
methanol. Processes for the conversion of the mixture of carbon
monoxide and hydrogen into such products are well known in the art.
The process of the present invention is further described by
way of the following illustrative examples, in which Examples 1, 3
and 4 relate to a process according to the present invention and
Examples 2 and 5 are for comparative purposes only.
Example 1
Catalyst Preparation
Barium hexa-aluminate (BaA112019) was prepared as follows:
Barium (21.0 g) was added to isopropyl alcohol (1500 ml) under
an atmosphere of nitrogen and the resultant mixture heated under
1; reflux for 1.5 hours. Further isopropyl alcohol (1000 ml) was added
to the resulting solution. Thereafter, aluminium isopropylate
(379.65 g) was added stepwise and the mixture heated under reflux
for a period of 5 hours. The resulting mixture (601.87 g) was
combined with demineralised water (22.5 g) and heated under reflux
whilst stirring for a further 1 hour. The resulting solution was
subsequently heated to evaporate the solvent to leave a solid
residue. The solid was dried by heating to 120°C and maintained at
that temperature for 4 hours. Thereafter, the solid was calcined in
a first stage by heating to 450°C over a period of 4 hours and being
held at that temperature for 1 hour and in a second stage by heating
to 1300°C over a period of 1 hour and being held at that temperature
for 5 hours.
An aqueous solution was prepared by dissolving rhodium chloride
(RhCl3, 2.0 g) and hydrochloric acid (37$, 1.0 g) in demineralised
Water (6.83 g) to give a rhodium concentration of 10$ by weight.
The barium hexa-aluminate prepared as described hereabove (30/80
mesh, 2.0 g) was immersed in the aforementioned aqueous solution
(1.07 g). The resulting mixture was agitated firstly in a rolling
mill for 1 hour and thereafter in a rotary drier for 1 hour. The
resulting material was dried in an oven by heating for 1 hour and
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being held at a temperature of 120°C for 5 hours and subsequently
calcined by heating for 5 hours and being held at a temperature of
500°C for 1 hour. The resulting catalyst comprised 5.0~ by weight
rhodium.
Catalytic Partial Oxidation
A reactor was constructed comprising a transparent sapphire
tube mounted concentrically within an outer transparent poly-
carbonate tube. The rhodium-containing catalyst prepared as
hereinbefore described was loaded into the sapphire tube and
retained in the form of a fixed bed of catalyst particles having a
tortuosity of 1.5. Methane and oxygen, in sufficient amounts to
give an oxygen-to-carbon ratio of 0.59, were thoroughly mixed just
before being introduced into the reactor to contact the fixed bed of
catalyst. The mixture of methane and oxygen was fed to the reactor
IS at a pressure of 5 bara and at a gas hourly space velocity (GHSV) of
1,240,000 N1/kg/hr.
The operating temperature of the catalyst bed was measured by
optical pyrometry. The composition of the gas mixture leaving the
reactor was measured by gas chromatography. The conversion and the
selectivity of the process to carbon monoxide and hydrogen (on the
basis of methane converted) was determined. The operating
conditions of the reactor and the results of the experiment are
summarised in Table 1 hereinbelow.
Example 2
Catalyst Preparation
An aqueous solution containing rhodium chloride was prepared as
described in Example 1. The solution contained rhodium in an amount
of 10~ by weight. Alpha alumina extrudates (commercially available
ex. Engelhard, crushed to 30/80 mesh size, 10.0 g) were immersed in
the aforementioned solution (5.33 g). The resulting mixture was
agitated firstly on a rolling mill for 1 hour and thereafter in a
rotary drier for 1 hour. The resulting material was dried in an
oven by heating for 1 hour and being held at a temperature of 120°C
for 5 hours and subsequently calcined by heating for 5 hours and
being held at a temperature of 500°C for 1 hour. The resulting
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catalyst comprised S.O~S by weight rhodium.
Catalytic Partial Oxidation
The catalyst prepared as described hereinbefore was loaded into
the apparatus and tested for activity in the partial oxidation of
methane using the same general procedure described in Example 1.
The operating conditions of the reactor and the results of the
experiment are summarised in Table 1 hereinbelow.
Example 3
A catalyst comprising 5.0$ by weight rhodium supported on
barium hexa-aluminate was prepared as described in Example 1
hereinbefore. The catalyst was loaded into the apparatus and tested
for activity in the catalytic partial oxidation of methane using the
same general procedure described in Example 1. The operating
conditions of the reactor and the results of the experiment are
summarised in Table 2 hereinbelow.
Example 4
Catalyst Pr~aration
Lanthanum zirconate (La2Zr207) was prepared using the following
method:
Lanthanum nitrate (La(N03)3.6H20, 27.07 g) and zirconium
oxychloride (ZrOC12.8H20, 20.19 g) were dissolved in demineralised
water (200 ml). Citric acid (30 g) was added to the resulting
solution. The resulting mixture Was heated to evaporate the
solvent, leaving a solid material as residue. The solid material
was dried by heating in an oven to 140°C and being held at that
temperature for 7 hours. Thereafter, the resulting material Was
calcined in an oven by heating to 700°C over a period of 5 hours and
being held at that temperature for 2 hours. Finally, the solid
material was heated at 1100°C for 5 hours.
An aqueous solution containing rhodium chloride was prepared as
described in Example 1. The solution contained rhodium in an amount
of 10$ by weight. The lanthanum zirconate prepared as described
hereabove (1.4 g) was immersed in the aforementioned solution
(1.7 ml). The resulting mixture was agitated firstly on a rolling
mill fox 1 hour and thereafter in a rotary drier for 1 hour. The
2129?~~
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resulting material was dried in an oven by heating for 1 hour and
being held at a temperature of 120°C for 5 hours and subsequently
calcined by heating for 5 hours and being held at a temperature of
500°C for Z hour. The resulting catalyst comprised 5.0> by weight
rhodium.
Catalytic Partial Oxidation
The catalyst prepared as described hereinbefore was loaded into
the apparatus and tested for activity in the partial oxidation of
methane using the same general procedure described in Example 1.
The operating conditions of the reactor and the results of the
experiment are summarised in Table 2 hereinbelow.
Example 5
A catalyst comprising 5.0~ by weight rhodium supported on
alpha-alumina was prepared as described in Example 2 hereinbefore.
The catalyst was loaded into the apparatus and tested for activity
in the catalytic partial oxidation of methane using the same general
procedure described in Example 1, The operating conditions of the
reactor and the results of the experiment are summarised in Table 2
hereinbelow.
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Table 1
Example 1 Example 2
Catalyst Rh/BaA112019 Rh/alpha-A1203
Operating Conditions
Temperature (°C) 1030 1040
Pressure (bara) 5 S
GHSV (1000 N1/kg/hr) 1240 1240
oxygen/carbon ratio 0.59 0.59
Initial Performance
CH4 conversion ($) 89.6 89.0
CO selectivity ($)1 91.0 91.5
H2 selectivity ($)2 90.4 88.8
Performance after 100 hours
CH4 conversion ($) 89.4 85.8
CO selectivity ($)1 91.0 91.2
H2 selectivity ($)2 90.0 87.5
Deactivation ($)3
CH4 conversion ($) 0.15 3.63
CO selectivity ($) 0.07 0.29
H2 selectivity ($) 0.46 1.52
1 selectivity to CO based on CH4 conversion
2 selectivity to H2 based on CH4 conversion
calculated by linear regression of the data for the first
100 hours
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Table 2
Example 3 Example 4 Example 5
Catalyst Rh/BaAll2olg Rh/La2Zr207 Rh/alpha-A1203
Operating Conditions
Temperature (C) 1055 1100 1060
Pressure (tiara) 10 10 10
GHSV (1000 N1/kg/hr)3300 3300 3300
oxygen/carbon 0.59 0.59 0.59
ratio
Initial Performance
CHq conversion (i) 90.4 86.6 89.0
CO selectivity (?s)1 92.1 91.8 93.7
H2 selectivity ($)2 89.6 87.0 88.5
Performance after 100 hours3
CH4 conversion ($) 89.3 86.3 79.3
CO selectivity (?s)1 92.1 91.8 93.0
H2 selectivity (~)2 89.6 86.0 80.4
Deactivation ($)3
CH4 conversion (~) 1.20 0.30 10.90
CO selectivity (~) 0.00 0.00 0.80
H2 selectivity (Fs) 0.00 1.10 9.20
1 selectivity to CO based on CH4 conversion
2 selectivity to H2 based on CH4 conversion
3 calculated by linear regression of the data for the first
60 hours for Examples 3 and 4 and for the first 46 hours for
Example 5
