Catalyst for steam reforming of hydrocarbon

The present invention provides a catalyst for steam reforming of hydrocarbons which comprises ruthenium supported on a zirconia carrier; and a catalyst for steam reforming of hydrocarbons which comprises (A) at least one element selected from the group consisting of rhodium and rutheniuim as an element imparting mainly reforming activity and (B) at least one element selected from the group consisting of nickel, lanthanum, praseodymium, neodymium, samarium, thorium, uranium, chromium, magnesium, calcium, and yttrium as an element for imparting co-catalyst function which are supported on a zirconia carrier; and furthermore a catalyst for steam reforming of hydrocarbons which comprises at least one element selected from the group consisting of rhodium and ruthenium which is supported on a partially stabilized zirconia carrier.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a catalyst for steam reforming of 
hydrocarbon and more particularly to a catalyst for steam reforming of 
hydrocarbon which has superior properties such as high catalyst activity, 
high heat resistance and mechanical strength and long life and which can 
be suitably utilized, for example, in a hydrogen producing plant for fuel 
cells and a small size hydrogen producing plant. 
2. Description of the Related Art 
Hitherto, as catalysts for acceleration of steam reforming reaction 
comprising reacting a hydrocarbon with steam to form hydrogen, carbon 
monoxide, methane and carbon dioxide, there have been catalyst systems as 
disclosed in (1) Japanese Patent Kokoku No. 12917/78, (2) Japanese Patent 
Kokai No. 91844/81 and (3) Japanese Patent Kokai No. 4232/82. 
The catalyst system disclosed in Japanese Patent Kokoku No. 12917/78 
comprises an alumina carrier which supports metallic nickel as a catalyst 
active component and, as co-catalysts, metallic silver in an amount of at 
least 2 mg atom per 100 g of catalyst and at least one of oxides of 
yttrium, lanthanum, cerium, praseodymium, neodymium and samarium in an 
amount of at least 2 mg atom per 100 g of catalyst and at a ratio in 
number of atom to silver of 10 or less. 
The catalyst system disclosed in the above Japanese Patent Kokai No. 
91844/81 comprises rhodium and zirconium oxide. 
The catalyst system disclosed in the above Japanese Patent Kokai No. 
4232/82 comprises an active alumina containing 0.5-10% by weight of silica 
and 1% by weight or less, in terms of oxide, of an alkali metal or an 
alkaline earth metal and 0.05-20% by weight of ruthenium supported on the 
active alumina. 
However, the alumina-supported catalyst systems disclosed in the first and 
the third patent publications suffer from the problems that they have 
activity at temperatures of higher than about 500.degree. C. and if the 
temperature is raised in order to further increase activity carbon is 
deposited on the catalyst and that when firing temperature is raised, 
surface area is conspicuously reduced resulting in reduction of catalyst 
activity or mechanical strength decreases due to shrinking or pressure 
loss of catalyst layer increases due to powdering to make the operation 
difficult. 
With reference to the catalyst system disclosed in the second patent 
publication, the reaction temperature may be lower than for the above 
alumina supported catalyst systems, for example, 500.degree. C., but 
catalyst activity is not sufficient and besides steam/carbon ratio is 
high, namely, 24 mol/mol and thus such catalyst system is not necessarily 
advantageous for industrial process for reforming hydrocarbons with steam. 
The inventors have already found that a catalyst system comprising rhodium 
metal supported on a zirconium carrier is a catalyst effective for 
reforming hydrocarbons with steam, which has high activity and can be 
controlled in the amount of formation of carbon on the catalyst. [cf. 
Igarashi et al: The 58th Catalyst Forum (A), 4 Ren B12, Nagoya]. 
This catalyst system is still not enough to be an industrial catalyst owing 
to its short life and insufficient activity. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a long life catalyst for 
steam reforming which is free from the above-mentioned problems and which 
has high activity even at a reaction temperature lower than 500.degree. C. 
and can perform steam reforming with low steam/carbon ratio. 
Another object of the present invention is to provide a catalyst for steam 
reforming of hydrocarbons which is free from the above-mentioned problems 
and which is high in catalyst activity, excellent in heat resistance and 
mechanical strength and improved in stability, reformability and catalyst 
life. 
The present invention for attaining the above objects resides in: 
a catalyst for steam reforming of hydrocarbons (catalyst I) which is 
characterized by comprising a zirconia carrier on which ruthenium is 
supported; 
a catalyst for steam reforming of hydrocarbons (catalyst II) which is 
characterized by comprising a zirconia carrier on which are supported (A) 
at least one metal selected from the group consisting of rhodium and 
ruthenium as an element to impart mainly reforming activity and (B) at 
least one element selected from the group consisting of nickel, lanthanum, 
praseodymium, neodymium, samarium, thorium, uranium, chromium, magnesium, 
calcium and yttrium as an element to impart co-catalyst function; and 
a catalyst for steam reforming of hydrocarbons (catalyst III) which is 
characterized by comprising a partially stabilized zirconia carrier on 
which is supported at least one element selected from the group consisting 
of rhodium and ruthenium. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
(1) Catalyst I 
Zirconia carrier 
It is especially important that zirconia is selected as a carrier in the 
present invention. This is because this zirconia carrier is especially 
high in reactivity with water, performs improvement of ability to reform 
hydrocarbons with steam and restrains deposition of carbon on the 
catalyst. 
Such zirconia carrier includes zirconium oxide and a substance capable of 
being converted to zirconium oxide at the time of preparation of catalyst 
or at steam reforming. 
The above zirconium oxide may be commercially available one. 
As the substance capable of being converted to zirconium oxide at the time 
of preparation of catalyst or at steam reforming, mention may be made of, 
for example, zirconium hydroxide, zirconium halide, zirconium nitrate, 
zirconyl nitrate, zirconium acetate, zirconium oxalate, zirconium 
alkoxide, zirconium oxychloride and organozirconium compound. 
Sparingly soluble salts may be solubilized and used by adding, for example, 
an acid. 
The above various zirconium compounds may be used alone or in combination 
of two or more. 
Among them, zirconyl nitrate is especially preferred. 
When zirconyl nitrate is used, zirconium oxide can be prepared by 
subjecting zirconyl nitrate to precipitation with ammonia water and 
thermally decomposing the precipitate. This may also be prepared by 
hydrolysis of an alkoxide compound of zirconium. 
The zirconium oxide used as a carrier may be anhydrous or may contain water 
of crystallization. 
Most preferred is zirconium oxide. 
In the present invention, other carriers may also be used together with the 
aforementioned zirconium compounds as zirconia carriers as far as 
attainment of the object of the present invention is not obstructed. 
Other carriers include silica, alumina and zeolite. 
The above-mentioned zirconium compounds and other carriers can be used as 
mixtures, or compositions such as composite oxides or composites 
comprising said zirconium compounds supported or coated on other carriers. 
Shape of the zirconia carrier is not critical and may have optional shapes 
such as fine powders, beads, pellets, plates, films and monolith. 
Metal to be supported; ruthenium 
As ruthenium sources for supporting ruthenium, mention may be made of, for 
example, ruthenium halides such as ruthenium iodide and ruthenium 
chloride, haloruthenates such as ammonium chlororuthenate, haloruthenic 
acids such as chlororuthenic acid, ruthenium oxides such as ruthenium 
hydroxide, ruthenium dioxide and ruthenium tetraoxide, ruthenates such as 
potassium ruthenate and organic ruthenium compounds such as ruthenium 
carbonyl. 
Such ruthenium sources may be used alone or in combination of two or more. 
Amount of ruthenium supported is generally 0.1-5% by weight, preferably 
0.3-3% by weight of zirconia carrier. 
In this case, if amount of ruthenium is too much, the carrier is covered 
with the supported metal and effects corresponding to the supporting 
amount cannot be obtained. 
Preparation of catalyst 
Process for preparation of catalyst I has no special limitation and there 
may be optionally employed, for example, impregnation process, dipping 
process, wet adsorption process, dry adsorption process, CVD process, 
solvent evaporation process dry mixing process, wet mixing process, spray 
coating process and combination of them. Operation method for supporting 
also includes any of stationary method, stirring method, solution passing 
method, solvent refluxing method and the like. An example of suitable 
preparation of catalyst is explained below. 
That is, zirconium hydroxide is fired, for example, at 
500.degree.-800.degree. C. for 1 hour to several hours and the resulting 
fired product is dipped in a solution or colloidal dispersion of the 
above-mentioned ruthenium compound normally for 0.1-10 hours, preferably 
0.5-5 hours, followed by mixing or kneading and evaporating to dryness. 
Then, the product is dried at 100.degree.-200.degree. C. over 0.1-24 hours 
and fired at 500.degree.-800.degree. C. for 0.1-20 hours in air or 
nitrogen stream. If necessary, the fired product is molded into desired 
shape and subjected to reducing treatment to obtain a catalyst for steam 
reforming of the present invention. 
Solvents used for solution or colloidal dispersion of the ruthenium 
compound are not limitative as far as they can dissolve the ruthenium 
compound or can keep stably as a uniform colloid solution. Aqueous 
solvents, non-aqueous solvents and mixed solvents thereof can be used. 
In carrying out the dipping, if necessary, various acids, bases, salts, 
oxidizing agents, reducing agents, pH modifiers, buffers and resolution 
accelerators can be added to the solution or colloidal dispersion of the 
ruthenium compound. 
Preferably, the reducing treatment mentioned above is performed by 
contacting the catalyst precursor packed in a reaction tube with hydrogen 
under heating. 
(2) Catalyst II 
Catalyst II comprises a zirconia carrier on which are supported at least 
one element selected from the group consisting of rhodium and ruthenium as 
an active metal and at least one element selected from the group 
consisting of nickel, lanthanum, praseodymium, neodymium, samarium, 
thorium, uranium, chromium, magnesium, calcium and yttrium as a 
co-catalyst. 
The catalyst II comprises combination of the specific active metal and the 
specific co-catalyst and can further improve ability of steam reforming of 
hydrocarbons together with employment of zirconia carrier. Besides, 
catalyst life can be further prolonged. 
Zirconia carrier: 
The same zirconia carrier as used in preparation of catalyst I can be used 
and so explanation thereof is omitted. 
Elements used as those of group (A) 
With reference to ruthenium, the same explanation as in catalyst I 
mentioned above can be made. 
As rhodium source for supporting rhodium metal, mention may be made of, for 
example, rhodium halides such as rhodium chloride, halorhodates such as 
sodium chlororhodate and ammonium chlororhodate, halorhodic acids such as 
chlororhodic acid, rhodium (III) hydroxide, rhodium (IV) hydroxide, 
rhodium nitrate, rhodium oxide and organorhodium compounds such as rhodium 
carbonyl. 
Such rhodium sources may be used alone or in combination of two or more. 
Preferred are rhodium halides and especially preferred in rhodium 
trichloride. 
In the catalyst II, elements of group (A) can be supported on a zirconia 
carrier. In this case, amount of the metal supported is normally 0.1-5% by 
weight, preferably 0.3-3% by weight of zirconia carrier and there is no 
limitation in ratio of two elements when two elements of group (A) are 
supported. 
Elements used as those of group (B) 
As nickel sources for supporting nickel, mention may be made of, for 
example, nickel chloride (hexahydrate), nickel chloride (anhydride), 
nickel bromide (hexahydrate), nickel bromide (anhydride), nickel iodide 
(hexahydrate), nickel iodide (anhydride), nickel nitrate, nickel sulfate, 
nickel acetate, nickel formate, nickel oxalate, nickel hydroxide, nickel 
oxide, nickel carbonate, nickel acetylacetonate and nickel carbonyl. 
Lanthanum sources, praseodymium sources, neodymium sources, samarium 
sources, chromium sources, uranium sources, thorium sources, magnesium 
sources, calcium sources, or yttrium sources for supporting lanthanum, 
praseodymium, neodymium, samarium, chromium, uranium, thorium, magnesium, 
calcium or yttrium include nitrates, sulfates, carbonates, acetates, 
hydroxides, oxides, basic salts, alkoxides and organic compounds of these 
metals. 
These sources may be used alone or in combination of two or more. 
Amount of element of group (B) obtained from the above metal sources can 
vary depending on kind of metal and cannot be indiscriminately specified, 
but normally 0.1-10% by weight, preferably 0.3-5% by weight of metals 
supported. Preparation of catalyst: 
Process for preparation of catalyst II is similar to that for catalyst I 
and has no special limitation. One suitable example of preparation of 
catalyst II is shown below. 
That is, zirconium oxide is fired in the same manner as in preparation of 
catalyst I and the resulting fired product is dipped in a solution or a 
colloidal dispersion containing compounds of elements selected from group 
(A) and (B) and is treated in the same manner as in preparation of 
catalyst I to obtain a catalyst for steam reformation. 
The fired product of zirconium oxide may be dipped in a solution or a 
colloidal dispersion of compounds of elements of group (A) and then in a 
solution or a colloidal dispersion of compounds of elements of group (B) 
or vice versa. 
(3) Catalyst (III) 
Partilly stabilized zirconia carrier 
It is especially important that a partially stabilized zirconia carrier is 
selected as a carrier in the present invention. 
This is because this partially stabilized zirconia carrier has inherited 
excellent properties as carrier such as especially high reactivity of 
zirconia per se with water, enhancement of ability to reform hydrocarbons 
with steam and prevention of deposition of carbon on catalyst and in 
addition to these properties, it is excellent in properties specific to 
partially stabilized zirconia resulting from addition of a stabilizer, 
namely, heat resistance and mechanical strength and is little in reduction 
of surface area even under a high temperature of at least 500.degree. C. 
and can be stably used. 
Such partially stabilized zirconia carrier can be obtained by modifying and 
stabilizing zirconia component with addition of a stabilizer. 
Zirconium source used as raw material for zirconia component of this 
partially stabilized zirconia carrier includes zirconium oxide and 
substances capable of being converted into zirconium oxide (zirconia 
component) at the time of preparation of catalyst or at steam reforming. 
The above zirconium oxide is the same as in catalyst I. 
Zirconium alkoxide is especially preferred as zirconium source in catalyst 
III. 
As stabilizers used as components of the partially stabilized zirconia 
carrier, mention may be made of, for example, yttrium oxide component, 
magnesium oxide component, cerium oxide component and other known various 
oxide components used as stabilizing components for so-called stabilized 
zirconia used in various fields of materials. 
Among them, especially preferred are yttrium oxide component, magnesium 
oxide component and cerium oxide component. 
These yttrium oxide component, magnesium oxide component and cerium oxide 
component can be formally expressed by Y.sub.2 O.sub.3, MgO and CeO.sub.2 
, respectively. 
Yttrium source used as raw material for preparation of the yttrium oxide 
component includes yttrium oxide and substances capable of being converted 
into yttrium oxide (yttrium oxide component) at the time of preparation of 
catalyst or at steam reforming. As the substances capable of being 
converted into yttrium oxide component, mention may be made of, for 
example, yttrium hydroxide, yttrium halides, yttrium oxyhalides, yttrium 
nitrate, yttrium carbonate, yttrium acetate, yttrium oxalate, and yttrium 
alkoxides such as yttrium trimethoxide, yttrium triethoxide, yttrium 
tripropoxide, yttrium triisopropoxide, and yttrium tributoxide. 
Among them, yttrium alkoxides are especially preferred. 
Magnesium source used as raw material for preparing the magnesium oxide 
component includes magnesium oxide and substances capable of being 
converted into magnesium oxide (magnesium oxide component) at the time of 
preparation of catalyst or at stem reforming. 
As the substances capable of being converted into magnesium oxide 
component, mention may be made of, for example, magnesium hydroxide, 
magnesium halides, magnesium oxyhalides, magnesium nitrate, magnesium 
carbonate, magnesium acetate, magnesium oxalate, and magnesium alkoxides 
such as magnesium methoxide, magnesium ethoxide, magnesium propoxide, 
magnesium isopropoxide, and magnesium butoxide. 
Among them, magnesium alkoxides are especially preferred. 
Cerium source used as raw material used for preparation of the cerium oxide 
component includes cerium oxide and substances capable of being converted 
into cerium oxide (cerium oxide component) at the time of preparation of 
catalyst or at steam reforming. As the substances capable of being 
converted into cerium oxide component, mention may be made of, for 
example, cerium hydroxide, cerium halides, cerium oxyhalides, cerium 
nitrate, cerium carbonate, cerium acetate, cerium oxalate, and cerium 
alkoxides such as cerium methoxide, cerium ethoxide, cerium propoxide, 
cerium isopropoxide and cerium butoxide. 
Among them, cerium alkoxides are especially preferred. 
These yttrium compounds, magnesium compounds and cerium compounds may be 
used alone or in combination of two or more. 
Sparingly soluble compounds can be used by solubilizing with addition of 
alcohol or acid. 
The partially stabilized zirconia carrier can be used as a mixture or 
composition with other carriers. 
Such other carriers include zirconia, silica, alumina and zeolite. 
Shape of the partially stabilized zirconia carrier is not critical and may 
be any of, for example, fine powders, beads, pellets, plates, films and 
monoliths. 
Preparation of partially stabilized zirconia carrier 
Process for preparation of partially stabilized zirconia carrier used as a 
carrier of catalyst for steam reforming of hydrocarbons according to the 
present invention is not limitative and, for example, coprecipitation 
process, wet kneading process, dry kneading process and combination 
thereof can be optionally employed. A suitable example of preparation is 
shown below. 
That is, the above-mentioned zirconium source, yttrium source, magnesium 
source and cerium source, for example, alkoxide compounds are used as raw 
material for preparation. These are precipitated as composite oxide or 
hydrate thereof comprising fine primary particles and having a large 
surface area by alkoxide hydrolysis process normally used for preparation 
of composite oxide in the field of preparation of catalysts. Then, the 
resulting precipitate is properly washed, thereafter dried and then, fired 
at a given temperature to obtain the partially stabilized zirconia 
carrier. 
Firing temperature here is usually 400.degree.-1,000.degree. C., preferably 
500.degree.-850.degree. C. 
Firing atmosphere is preferably air. 
If desired, the above firing step can be omitted. Metals to be supported; 
ruthenium and rhodium: 
The same explanation as in catalyst II can be made on ruthenium and 
rhodium. 
Preparation of catalyst 
Process for preparation of catalyst III is the same as for catalyst I and 
catalyst II. 
A suitable example of preparation of catalyst is shown below. 
That is, the partially stabilized zirconia carrier obtained above is dipped 
in a solution or a colloidal dispersion of the above-mentioned ruthenium 
compound and/or rhodium compound normally for about 0.1-10 hours, 
preferably 0.5-5 hours, followed by mixing or kneading and evaporating to 
dryness. Then, the product is dried at 100.degree.-200.degree. C. for 
0.1-24 hours and then fired at 500.degree.-850.degree. C. for 0.1-20 hours 
in air or nitrogen stream and, if necessary, molded into a desired shape, 
for example, by a tablet compressing method, followed by reduction 
treatment to obtain the catalyst for steam reforming of the present 
invention. 
Steam reforming of hydrocarbon 
The above-mentioned catalyst I, catalyst II and catalyst III which are 
catalysts for steam reforming are used for accelerating steam reforming of 
hydrocarbons. 
The hydrocarbons to be reformed are not limitative and include, for 
example, straight chain or branched chain saturated aliphatic hydrocarbons 
such as methane, ethane, propane, butane, pentane, hexane, heptane, 
octane, nonane, and decane and cycloaliphatic saturated hydrocarbons such 
as cyclohexane, methylcyclohexane and cyclooctane. 
These hydrocarbons are used alone or in combination of two or more or may 
be various purified petroleum fractions. 
Steam to be reacted with hydrocarbons is not limitative. 
The above hydrocarbons are considered to react with steam in accordance 
with the following reaction formulas. 
EQU C.sub.n H.sub.m +nH.sub.2 O.fwdarw.nCO+(n+m/2)H.sub.2 (I) 
EQU C.sub.n H.sub.m +2nH.sub.2 O.fwdarw.nCO.sub.2 +(2n+m/2)H.sub.2(II) 
[n in the formulas (I) and (II) represents a real number of 1 or more and m 
represents a real number of 2 or more.] 
In addition to the above formulas, reaction (III) of formation of CH.sub.4 
by hydrogenolysis of hydrocarbon and the following equilibrium reactions 
can be considered to occur jointly. 
EQU CH.sub.4 +H.sub.2 O.revreaction.CO+3H.sub.2 (IV) 
EQU CO+H.sub.2 O.revreaction.CO.sub.2 +H.sub.2 (V) 
Therefore, theoretically amounts of hydrocarbon and steam used can be 
determined in stoichiometric amounts which satisfy the above reaction 
formulas (I)-(V), but when the catalyst of the present invention is used, 
amounts of hydrocarbon and steam are preferably determined so that the 
steam/carbon ratio is 3-12, preferably 3-8. 
By employing such steam/carbon ratio, gases rich in hydrogen can be 
efficiently and stably obtained. Reaction temperature is normally 
300.degree.-950.degree. C., preferably 400.degree.-850.degree. C. 
It is worth notice that the catalyst of the present invention has 
sufficiently high catalytic activity even at a reaction temperature of 
500.degree. C. or lower. 
Reaction pressure is normally 0-50 kg/cm.sup.2 G, preferably 0-20 
kg/cm.sup.2 G. 
Reaction method may be any of continuous flowing method, batch method, and 
the like, but the continuous flowing method is suitable. 
When the continuous flowing method is employed, gas space velocity (GHSV) 
of mixed gas of hydrocarbon and steam is usually 1,000-40,000 h.sup.-1, 
preferably 2,000-20,000 h.sup.-1. 
What is worth notice when the catalyst of the present invention is used is 
that continuous operation is possible even at such high gas space 
velocity. 
Reaction type is not limitative and may be any of fixed bed type, moving 
bed type, fluidized bed type, etc. 
Type of reaction apparatus is also not limitative and, for example, a tube 
type reactor may be employed. 
In this way, when hydrocarbon and steam are allowed to react in the 
presence of the catalyst of the present invention, the reaction proceeds 
normally and mainly in accordance with the above reaction formula (I), but 
since the reaction of the reaction formula (II), the equilibrium reaction 
(V) where produced carbon monoxide and water react to produce carbon 
dioxide and hydrogen and the equilibrium reaction (IV) where carbon 
monoxide and hydrogen react to produce methane and water also take place 
simultaneously, as a result there is obtained a mixture of hydrogen, 
methane, carbon monoxide and carbon dioxide, although main product is 
hydrogen. 
The resulting mixed gas can be used as it is or can be separated into 
respective gas components, which are used for respective purposes. 
The present invention is explained by the following examples.

EXAMPLE 1 
A catalyst for steam reforming (Ru/ZrO.sub.2) was prepared by supporting 
0.5% by weight of RuCl.sub.3 in terms of Ru on a ZrO.sub.2 carrier 
obtained by firing ZrO.sub.2.xH.sub.2 O and subjecting this catalyst to 
reducing treatment with hydrogen in a reaction tube. 
Steam reforming was carried out using a normal-pressure fixed-bed flow type 
reaction apparatus, n-butane as a starting material and the following 
conditions; reaction temperature: 450.degree. C., reaction time factor: 
622.7 (g-cat.min/n-butane mol) and a steam/carbon ratio (feeding ratio of 
steam and n-butane calculated from molar ratio): 12. 
Continuous analyses by a gas chromatography gave total conversion rate of 
60.6% as a catalyst activity after 10 hours from initiation of the 
reaction and the following composition of the resulting gas: carbon 
monoxide: 1.1 mol %, methane: 20.7 mol %, carbon dioxide: 18.5 mol % and 
hydrogen: 59.7 mol %. 
EXAMPLES 2-13 
Procedure of Example 1 was repeated except that catalysts having the metals 
as shown in Table 1 supported were used. The results are shown in Table 1 
together with those in Example 1. 
COMATIVE EXAMPLE 1 
Procedure of Example 1 was repeated except that a catalyst comprising 
zirconia carrier and rhodium supported thereon was used. The results are 
also shown in Table 1. 
TABLE 1 
______________________________________ 
Total 
conver- 
Dry gas composition 
sion rate 
(mol %) 
Catalyst system (%) CO CH.sub.4 
CO.sub.2 
H.sub.2 
______________________________________ 
Example 1 
Ru/ZrO.sub.2 
60.6 1.1 20.7 18.5 59.7 
Example 2 
Rh-Ni/ZrO.sub.2 * 
70.9 1.8 21.8 19.1 57.4 
Example 3 
Rh-Cr/ZrO.sub.2 * 
61.3 1.9 17.2 20.0 60.8 
Example 4 
Rh-La/ZrO.sub.2 * 
61.0 2.0 17.5 19.2 61.3 
Example 5 
Rh-Pr/ZrO.sub.2 * 
57.6 2.2 15.1 20.2 62.5 
Example 6 
Rh-Nd/ZrO.sub.2 * 
68.3 2.5 16.1 19.7 61.8 
Example 7 
Rh-Sm/ZrO.sub.2 * 
84.9 2.8 19.6 19.7 58.0 
Example 8 
Ru-Th/ZrO.sub.2 * 
68.2 2.1 13.9 20.1 63.8 
Example 9 
Rh-U/ZrO.sub.2 * 
75.1 1.9 20.5 20.0 57.8 
Example 10 
Rh-Mg/ZrO.sub.2 * 
69.9 1.9 17.5 20.4 60.1 
Example 11 
Rh-Ca/ZrO.sub.2 * 
59.1 1.9 13.7 20.0 64.4 
Example 12 
Rh-Y/ZrO.sub.2 * 
71.2 2.0 17.4 20.4 60.1 
Example 13 
Rh-Th/ZrO.sub.2 * 
73.0 1.9 22.1 18.8 57.2 
Comp. Rh/ZrO.sub.2 
50.6 2.1 12.4 19.2 66.4 
Ex. 1 
______________________________________ 
*: Supporting amount of Rh or Ru was 0.5% by weight and that of other 
elements was 1% by weight. 
EXAMPLES 14-15 
Life of catalyst systems shown in Table 2 was evaluated using 
normal-pressure fixed bed flow type reaction apparatus and n-butane as a 
starting material. 
Reaction conditions were the following; reaction temperature: 450.degree. 
C., reaction time factor: 622.7 (g-Cat.min./n-butane mol) and a 
steam/carbon ratio: 12. 
The results are shown in Table 2. 
COMATIVE EXAMPLE 2 
Procedure of Examples 14-15 was repeated except that Rh/ZrO was used as a 
catalyst. 
TABLE 2 
______________________________________ 
Total conversion rate (%) 
Catalyst system 
Initial After 1,000 hr 
______________________________________ 
Example 14 
Rh-Th/ZrO.sub.2 
68.2 68.1 
Example 15 
Rh-La/ZrO.sub.2 
61.0 60.5 
Comparative 
Rh/ZrO.sub.2 
50.7 47.0 
Example 2 
______________________________________ 
EXAMPLES 16-20 
Preparation of partially stabilized zirconia carrier 
Zirconium alkoxide as zirconium source for zirconia component (formally 
ZrO.sub.2) and an alkoxide of yttrium, magnesium or cerium as yttrium 
source, magnesium source or cerium source for yttrium oxide component 
(formally Y.sub.2 O.sub.3), magnesium oxide component (formally MgO) or 
cerium oxide component (formally CeO.sub.2) were respectively dissolved in 
isopropyl alcohol and water was added thereto with well stirring to effect 
hydrolysis to precipitate a composite oxide (hydrate) of large surface 
area comprising ultrafine particles of 0.03 .mu.m in primary particle 
size. The resulting precipitate was washed, then dried at 120.degree. C. 
for 24 hours and thereafter, fired for 3 hours in air to obtain a 
partially stabilized zirconia carrier having a composition desired as a 
carrier for partially stabilized zirconia supporting catalysts as shown in 
Table 3. 
Preparation of catalyst 
On the partially stabilized zirconia carrier was supported RuCl.sub.3 or 
RhCl.sub.3 in an amount of 0.5% by weight in terms of metal, followed by 
reducing treating with hydrogen in a reaction tube to prepare steam 
reforming catalyst supported on the partially stabilized zirconia as shown 
in Table 3. 
Using the catalyst obtained above, steam reforming was carried out by 
normal-pressure fixed bed flow type reaction apparatus using n-butene as a 
starting material and employing the reaction conditions of reaction 
temperature: 450.degree. C., reaction time factor: 622.7 (g-cat 
min./n-butane mol) and steam/carbon ratio of 12 (feeding ratio of steam 
and n-butane calculated from molar ratio). 
Continuous analyses by a gas chromatography gave the results as shown in 
Table 3 on catalyst activity (total conversion rate) after 10 hours from 
initiation of the reaction and composition of the resulting gas (carbon 
monoxide, methane, carbon dioxide and hydrogen). 
COMATIVE EXAMPLE 3 
The catalyst Rh/ZrO.sub.2 shown in Table 3 was obtained by supporting RhCl 
in an amount of 0.5% by weight of rhodium supported on ZrO carrier 
prepared by firing ZrO.sub.2.xH.sub.2 O at 500.degree. C. for 1 hour in 
air. 
Reaction was carried out in the same manner as in Example 16 using the 
Rh/ZrO.sub.2 catalyst. 
The results are shown in Table 3. 
EXAMPLE 21 AND COMATIVE EXAMPLE 4 
As shown in Table 4, the same catalysts as used in Example 16 and 
Comparative Example 3 were subjected to long period life test under the 
same conditions as in Example 16. 
Total conversion rates, pressure loss (relative value) of catalyst layer 
and change in surface area of catalyst according to BET method at the 
initial stage of reaction and after 1,000 hours onstream are shown in 
Table 4. 
From the results as shown in Tables 3 and 4, it can be seen that the 
catalyst comprising the partially stabilized zirconia carrier of the 
present invention is an excellent catalyst for stream reforming of 
hydrocarbons, showing excellent catalyst activity, heat resistance, 
mechanical strength, less in reduction of surface area even at high 
temperatures, very hard to be powdered or broken due to shrink and 
improved in stability, reforming ability and life as compared with the 
catalysts comprising a zirconia carrier. 
TABLE 3 
______________________________________ 
Total 
conver- 
Catalyst sion rate 
Dry gas composition 
system (%) CO CH.sub.4 
CO.sub.2 
H.sub.2 
______________________________________ 
Example 16 
Rh/partially 
67.8 2.7 19.4 19.7 58.3 
stabilized 
ZrO.sub.2 (1) 
Example 17 
Rh/partially 
68.5 1.4 20.2 18.0 60.4 
stabilized 
ZrO.sub.2 (1) 
Example 18 
Rh/partially 
71.0 2.6 19.3 19.6 60.4 
stabilized 
ZrO.sub.2 (2) 
Example 19 
Rh/partially 
69.0 2.6 14.7 19.5 63.2 
stabilized 
ZrO.sub.2 (3) 
Example 20 
Rh/partially 
65.0 2.4 16.5 19.3 61.8 
stabilized 
ZrO.sub.2 (4) 
Comparative 
Rh/ZrO.sub.2 
50.1 2.1 12.3 19.2 66.4 
Example 3 
______________________________________ 
Amount of support Rh 0.5 wt % 
Partially stabilized ZrO.sub.2 (1) Y.sub.2 O.sub.3 4.4% 
Partially stabilized ZrO.sub.2 (2) Y.sub.2 O.sub.3 8.0% 
Partially stabilized ZrO.sub.2 (3) CeO.sub.2 12.0% 
Partially stabilized ZrO.sub.2 (4) MgO 3.4% 
TABLE 4 
__________________________________________________________________________ 
Total conversion 
Pressure loss of catalyst 
Surface area of 
rate (%) layer (relative value) 
catalyst (m.sup.2 /g) 
Catalyst system 
Initial 
After 1000 hr 
Initial 
After 1000 hr 
Initial 
After 1000 hr 
__________________________________________________________________________ 
Comparative 
Rh/ZrO.sub.2 
50.7 
47.0 1.0 2.2 60 20 
Example 4 
Example 21 
Rh/partially 
67.0 
65.8 1.0 1.3 70 45 
stabilized 
ZrO.sub.2 (1) 
__________________________________________________________________________ 
The present invention can provide a catalyst for steam reforming which 
maintains high catalyst activity even at a temperature of lower than 
500.degree. C., shows no reduction in catalyst activity even after 
long-term reaction, can efficiently reform hydrocarbons with steam even at 
low steam/carbon ratio and even when raw material gas is flowed at a high 
gas space velocity and can produce a mixed gas rich in hydrogen. 
Furthermore, since the specific carrier of partially stabilized zirconia is 
used, the present invention can provide a catalyst for steam reforming of 
hydrocarbons having excellent merits such as high catalyst activity, 
superior heat resistance and mechanical strength and improved stability, 
reforming ability and catalyst life. 
The catalyst of the present invention has good efficiency and is a catalyst 
suitable, for example, for small sized plant for preparation of hydrogen 
and for production of hydrogen for fuel cells.