JP2002079102A - Catalyst for shift reaction and reaction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a novel catalyst for shift reaction, which is capable of satisfying both of the catalytic activity and durability, and an efficient method for transforming carbon monoxide using the catalyst. SOLUTION: The shift reaction catalyst contains copper, palladium and/or platinum and has an atomic ratio, copper to palladium and/or platinum, of 0.2-20 and in the method for transforming carbon monoxide, carbon monoxide is transformed in the presence of the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for a shift reaction which is useful in converting carbon monoxide and water into hydrogen and carbon dioxide, and a method for converting carbon monoxide using the catalyst. .

[0002]

2. Description of the Related Art Conventionally, synthesis gas has been used not only for synthesizing compounds such as methanol and aldehydes but also for producing ammonia and pure hydrogen. However, synthesis gas produced by steam reforming of methanol or hydrocarbons generally has a relatively high content of carbon monoxide, so that hydrogen is usually generated by a shift reaction in which this is reacted with steam,
There is a need to reduce the carbon monoxide content.

The above reaction is an exothermic reaction as shown in the following formula (1) [formula 1] and is greatly restricted in equilibrium.
Catalysts with high activity at low temperatures are advantageous.

[0004]

(Equation 1)

[0005] Usually, the above-mentioned shift reaction is generally performed in two stages of a high-temperature reaction of about 350 to 400 ° C and a low-temperature reaction of about 180 to 240 ° C in order to further increase the conversion efficiency.

[0006] A catalyst usually used for an industrial water gas shift reaction at a relatively low temperature (so-called low-temperature shift reaction) has a basic composition of copper oxide, zinc oxide, or aluminum oxide. Further improvements have been made regarding their catalytic activity and stability. For example, in the description of JP-A-8-229399,
Attempts have been made to add a titanium group element to a catalyst composed of copper, zinc, and aluminum, thereby stabilizing copper as an active ingredient.

[0007] Also, "Catalyst VOL42, No. 2" (2
(Issued on March 10, 000) P96-98 discloses known copper-based catalysts and noble metal-based catalysts, and furthermore, known shift reaction catalysts containing copper oxide, zinc oxide, and aluminum oxide are widely used. It is disclosed that it shows conversion activity for various carbon monoxide concentrations. On the other hand, it is disclosed that noble metal-supported catalysts (platinum, ruthenium) are highly active against low concentrations of carbon monoxide.

Further, Appl. Catal. A General., 194-195 (2
000) 21-26 describes a catalyst using a copper-based catalyst in a source gas system containing oxygen and further containing gold, palladium, platinum, rhodium, or ruthenium as a noble metal. However, none of these satisfies both the catalytic activity and durability during the shift reaction, and further practical ones are required.

As described above, a catalyst containing a copper-based element is generally considered to have a problem in heat resistance, which is considered to be because the catalyst is deactivated by water vapor contained in a feedstock. . From these viewpoints, not only the activity of the catalyst,
There is a strong demand for the development of more practical shift reaction catalysts that are sufficiently excellent in durability.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventionally known catalysts and provides a novel catalyst for shift reaction which can sufficiently satisfy both the catalytic activity and the durability. And an efficient method for converting carbon monoxide using the catalyst.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, it has been found that those containing palladium and / or platinum elements together with copper elements are effective.
In particular, those containing elemental palladium and / or platinum in a specific range have markedly improved not only catalytic activity but also their durability. Particularly, in a shift reaction in the presence of water vapor, the durability of the catalyst is dramatically increased. The inventors have found that the present invention is improved, and have completed the present invention.

That is, the present invention provides (1) a shift reaction comprising copper and palladium and / or platinum, and having an atomic ratio of copper to palladium and / or platinum of 0.5 to 20. Catalyst for
(2) The catalyst according to (1) further comprises zinc,
(3) The catalyst according to (2), wherein the atomic ratio of zinc to copper is 0.1 to 10.
(4) above (1) ~
A method for converting carbon monoxide, which comprises converting carbon monoxide in the presence of the catalyst according to any one of (3).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst for shift reaction in the present invention comprises palladium and / or platinum as essential components in addition to copper. In this catalyst, the atomic ratio of copper to palladium or platinum is preferably in the range of 0.5 to 20, more preferably 1 to 10. When the catalyst is configured to contain both palladium and platinum, the atomic ratio of copper to the total of these is preferably in the range of 0.5 to 20, and more preferably in the range of 1 to 10. Is more preferable.

That is, when the atomic ratio of copper to palladium and / or platinum is less than 0.5, the durability of the catalyst is good, but the activity becomes inferior, and the above atomic ratio exceeds 20. Although the initial activity of the catalyst is increased, sufficient results are not obtained in the durability thereof.In particular, in order to sufficiently satisfy both the activity and the durability, the catalyst should have the content ratio range described above. Is preferred.

[0015] In the shift reaction catalyst of the present invention, it is more preferable that the catalyst further contains zinc in addition to the above components, since the catalytic activity is further enhanced. The content ratio of zinc is preferably such that the atomic ratio of copper / zinc is 0.1 to 10, more preferably 0.2 to 4. Further, a configuration containing another metal element may be used as long as the object of the present invention is not impaired.

For obtaining the catalyst for the shift reaction of the present invention, no particular formulation is required, and the catalyst can be produced by a usual method. For example, it can be prepared by a general method, as described in "Catalyst Course, Vol. 5" (published November 1, 1986, Kodansha) edited by the Catalysis Society of Japan.
Specifically, it can be obtained by a method such as a coprecipitation method, a deposition method, or an impregnation method. The catalyst precursor obtained by these methods is subjected to a reduction treatment using hydrogen or a reducing agent in a liquid phase, or after a treatment such as baking under a gas phase, and then subjected to a hydrogen treatment to form an alloy catalyst. It can also be prepared.

The catalyst of the present invention can be used by being supported on or mixed with an inorganic carrier such as silica, silica alumina, titania, alumina, silicon carbide, zeolite, aluminum phosphate, montmorillonite and mica.

Furthermore, after the catalyst of the present invention is produced by the above-mentioned method, it can be used as a molded catalyst by tableting or extrusion molding.
It is also possible to use a honeycomb support supported on a ceramic carrier such as mullite or cordierite, a silica cloth, a sponge-shaped sintered metal porous plate, or the like.

Next, the shift reaction in the present invention is usually carried out in the presence of the above-mentioned catalyst by contacting carbon monoxide and water (steam). The reaction conditions at this time are usually a reaction temperature of 150 to 350 ° C. and a reaction pressure of 70 kg / cm ² G or less, preferably 30 kg / cm ² G to normal pressure.

The ratio of water to carbon monoxide is in the range of 0.5 to 30 mol of water per mol of carbon monoxide, and the space velocity of these mixed vapors is 50 to 50,000 hr ^-1 , more preferably. The range is from 3000 to 30,000 hr ^-1 . In addition, if necessary, hydrogen gas, carbon dioxide gas, nitrogen, and the reaction can be performed by adding air and the like, so that the method of the present invention can be used after steam reforming hydrocarbons or methanol. is there.

The shift reaction in the present invention is possible by bringing carbon monoxide and water into contact with a catalyst, and is not particularly limited by the scale of the apparatus. The reaction can be carried out by any conventionally known reaction mode such as a fixed bed system and a fluidized bed system.

[0022]

The present invention will be further described below with reference to examples, comparative examples and catalyst activity test examples, but the scope of the present invention is not limited by these descriptions. In the following,% is based on mass, unless otherwise specified.

1) Preparation of catalyst Example 1 14.3 g of 10% aqueous solution of palladium nitrate [Pd (NO ₃ ) ₂ ], copper nitrate
Trihydrate _{[Cu (NO 3) 2 ·} 3H 2 O] 3.76g, zinc nitrate hexahydrate [Z
10.06 g of [n (NO ₃ ) ₂ .6H ₂ O] was dissolved in 200 ml of pure water to obtain an aqueous solution. Next, 1N sodium carbonate [Na ₂ CO ₃ ] was added to this aqueous solution.
Was added under stirring at room temperature until the pH of the solution reached 6.6 to 6.8. After the produced slurry was stirred at 50 ° C. for 150 minutes, the produced precipitate was filtered under reduced pressure and washed sufficiently with distilled water. Thereafter, the precipitate separated by filtration is dried at 80 ° C.
After drying for 12 hours, it was baked in an electric furnace at 350 ° C. for 3 hours in the air. After tableting and pulverizing the obtained oxide,
1 ml thereof was collected. This was filled in a small reaction tube, H ₂ / N
_A reduction treatment was performed with a mixed gas of ₂ = 1/9 GHSV = 6000 [hr ^-1 ] to obtain a catalyst.

Example 2 In Example 1, 2.53 g of chloroplatinic acid hexahydrate, 2.95 g of copper nitrate trihydrate was used instead of the 10% aqueous palladium nitrate solution.
g and the copper / platinum atomic ratio = 2.5. These reagents were dissolved in 200 ml of pure water to form an aqueous solution, and an aqueous ammonia solution was stirred and mixed at room temperature, and added until the pH of the solution became 6.6 to 6.8. Other procedures were prepared in the same manner as in Example 1.

[0025] In Example 3 Example 1, 10% palladium nitrate [Pd (NO _{3) 2]} aqueous solution 10.06 g, copper nitrate trihydrate _{[Cu (NO 3) 2 ·} 3H 2 O] 4.39g of pure It was dissolved in 200 ml of water to make an aqueous solution. Next, 1N Na ₂ CO ₃ was stirred and mixed at room temperature, and added until the pH of the solution reached 6.6 to 6.8. Subsequent operations were prepared in the same manner as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that 6.07 g of copper nitrate trihydrate was added without using a 10% aqueous solution of palladium nitrate.
It was prepared in the same manner as described above.

Comparative Example 2 In Example 1, 1.1 g of a 10% aqueous palladium nitrate solution and 5.89 g of copper nitrate trihydrate were added, and a copper / palladium ratio = 50.
Was prepared in the same manner as in Example 1, except that

Comparative Example 3 In Example 1, 33.3 g of a 10% aqueous solution of palladium nitrate and 0.70 g of copper nitrate trihydrate were added, and the copper / palladium ratio was 0.3.
Except for changing it to 2, it was prepared in the same manner as in Example 1.

2) Activity test The activity of the shift reaction was measured for the copper / palladium catalyst and the copper / platinum catalyst prepared by the above method. The reaction gas composition is H ₂ , 42.86 vol%; CO, 8 vol%; CO ₂ , 6.29 vol
%; N ₂ , 14.29 vol%; H ₂ O, 28.57%, at a reaction temperature of 230 ° C. under normal pressure, the raw material gas was converted to 30,000 (L-solv./L- cat · h). The reaction gas was analyzed by gas chromatography, the CO concentration in the produced gas was measured, and the carbon monoxide content in the produced gas was measured from the CO conversion shown by the following equation.

[0030]

(Equation 2)

The activity reduction rate was calculated from the conversion rate reduction rate 100 hours after the start of the reaction. Table 1 shows the results of the activity test.

[0032]

[Table 1]

[0033]

As is clear from the catalysts shown in the above Examples and Comparative Examples, and the results of the activity tests of the catalysts, the catalysts of the present invention are sufficiently excellent not only in activity but also in durability. I understand.

Further, according to the method for converting carbon monoxide of the present invention, the use of the catalyst of the present invention enables efficient production of hydrogen over a long period of time.

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Claims (4)

[Claims] 1. A catalyst for shift reaction, comprising copper and palladium and / or platinum, and having an atomic ratio of copper to palladium and / or platinum of 0.5 to 20. 2. The catalyst for a shift reaction according to claim 1, further comprising zinc. 3. An atomic ratio of zinc to copper of 0.1-10.
The catalyst for a shift reaction according to claim 2, wherein 4. A method for converting carbon monoxide, which comprises converting carbon monoxide in the presence of the catalyst according to claim 1. Description: