JPH05161848A - Preparation of high-activity and high-strength nickel/ magnesia catalyst - Google Patents

Abstract

PURPOSE:To provide the preparation method of a high-activity and high-strength nickel/magnesia catalyst useful for the steam reforming of hydrocarbons and the methanation of synthetic gas. CONSTITUTION:In the preparation of a nickel/magnesia (Ni/MgO) catalyst consisting of high-purity, ultrafine particulate monocrystalline magnesia of an average particle size of 100-2000Angstrom (diameter from BET specific surface) and nickel of 0.1-50wt.% of magnesia, the nickel compound, after being supported on the magnesia, is heat-treated to obtain the powder of magnesia carrying nickel oxide. The magnesia powder, after being added with 0.2-3.0wt.% of magnesium stearate, is molded into a desired shape to be heat-treated at 550-800 deg.C in a reducing gas atmosphere.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for preparing a catalyst useful for steam reforming of hydrocarbons, methanation of synthesis gas, hydrogenation of cyclic and alicyclic unsaturated hydrocarbons and the like.

More specifically, by reforming hydrocarbons with steam, raw material gases for various synthesis such as ammonia synthesis, methanol synthesis and oxo synthesis, city gas, various fuel gases such as fuel cells, reducing gas for iron making, and high purity. The present invention relates to a method for preparing a catalyst particularly suitable for producing hydrogen gas, hydrogen, carbon monoxide and / or carbon dioxide, a synthesis gas containing methane as a main component, and the like.

Further, various gases such as high-purity methane gas and high calorific value city gas are produced by methanizing a synthetic gas containing hydrogen, carbon monoxide and / or carbon dioxide as main components,
Alternatively, the present invention relates to a method for preparing a catalyst suitable for removing a trace amount of carbon monoxide remaining in an ammonia synthesis raw material.

[0004]

BACKGROUND OF THE INVENTION The present invention relates to a method for preparing a catalyst useful for steam reforming of hydrocarbons, methanation of synthesis gas and the like. In general, nickel-based catalysts are most frequently used for these reactions in terms of activity and economy. Most commercially available nickel-based catalysts are those in which nickel is supported on a carrier such as an alumina-based, heat-resistant oxide, or spinel.

The nickel / alumina-based catalysts most frequently used in the past (for example, Japanese Examined Patent Publication No. Sho 49-9312) are
Since the alumina phase changes to the α-alumina phase in the high temperature region and the crystal growth proceeds, there is a problem that the specific surface area sharply decreases and the activity decreases accordingly.

Further, a potassium compound is often added to these catalysts as an alkaline component in order to prevent the precipitation of carbon. In this case, there is a problem that the potassium compound scatters in the reactor, pipes and the like during use and corrosion occurs.

Furthermore, when the alumina-based carrier comes into contact with the high temperature vapor of alkali carbonate, which is the electrolyte of the fuel cell, the problem of chemical corrosion also occurs [US DOE Rep. P43 (1984), M. Tarj.
anyiet al., Fuel Cell Seminar, Tucson, Arizona (USA), p
177 (1985)].

On the other hand, a method using a heat-resistant carrier which is made into a composite oxide by adding other components to alumina has also been reported. For example, one prepared by impregnating alumina with lanthanum, lithium or strontium (US Pat. No. 39.
No. 66391, No. 4021185, No. 40615.
No. 94, etc.), or those prepared by coprecipitating hydroxides of rare earth salts on alumina (Japanese Patent Application No. 59-807).
No. 52), which is prepared by hydrolyzing aluminum alkoxide and lanthanum alkoxide to form a mixed sol of hydroxide (Japanese Patent Laid-Open No. 175642/1988), and a spinel-based material obtained by adding magnesia to alumina and firing. (Japanese Patent Laid-Open No. 55-139836) and the like.

Each of these is based on the premise that a porous carrier is first prepared, and a nickel active component is loaded in the pores of the porous body by an impregnation method (intrapore impregnation method). Inferior in terms of catalytic activity. There is also a problem with respect to chemical attack by high temperature steam of alkali carbonate.

Under these circumstances, nickel / magnesia-based catalysts have recently attracted attention and many reports and patents have been reported [Japanese Patent Publication No. 46-43363, Japanese Patent Publication No. 55-55].
50080, JP-A-63-137754, JP-A-6
No. 3-248444, pollution resource Research稾報12 No.3 p1 (1983)
, Proceedings of Catalysis Debate, 52 p38 (1983), Report of Masterpiece Test 35 p
77 (1986)].

However, the only drawback of this nickel / magnesia catalyst is that the catalyst has a low mechanical strength. This type of catalyst, particularly a steam reforming catalyst, is generally filled in a reforming tube having a length of more than 10 m and is required to withstand long-term use under severe conditions of high temperature and high pressure. Therefore, it is said that this type of catalyst is required to have an axial compressive strength (in the case of a cylinder or a ring) of 500 kgf / cm ² or more.

No catalyst has yet been reported that has achieved the above strength target value while maintaining the specific activity of the nickel / magnesia catalyst. The reason is considered as follows. That is, the most general method for increasing the strength of nickel / magnesia catalyst pellets is by calcination, which requires a calcination temperature of 600 ° C. or higher.

[0013] However, this way is baked at a high temperature, heretofore many published reports [pollution resource Labs稾報12 No.3 p1 (1983), the catalyst debate Preprint 52 p38 (1983), NIT trial reported 34 No .6
p165 (1985)], magnesia and nickel oxide are solid-solved to form a nickel complex oxide that is difficult to reduce, so the nickel component, which is the catalytically active component, does not play its role and the catalytic activity is It is widely known to decrease. Therefore, it has been difficult to maintain the catalyst activity and the catalyst strength at a high level at the same time.

Under these circumstances, although it is admitted that it is desirable to use only magnesia as a carrier material from the viewpoint of catalytic activity, it is abandoned to use only magnesia as a carrier material. 2 methods have been adopted.

One of them is a method in which a binder such as alumina cement, magnesium chloride or magnesium phosphate is used in combination (Japanese Patent Publication Nos. 49-9312 and 46-4).
3363 and JP-A-63-137754). The other method is to add a third substance such as alumina, chromium oxide, and iron oxide to magnesia to measure the firing temperature decrease (Japanese Patent Publication Nos. 48-13828 and 48-265).
96, Japanese Patent Publication No. 52-22640, etc.).

These methods have simultaneously improved activity and strength to considerable levels. However, it is still insufficient and much room for improvement remains. Further, as mentioned above, no example is found in which only magnesia is used as the carrier. Moreover, all of the magnesia used in the above catalysts are ordinary magnesia produced by the liquid phase method or the thermal decomposition method, and are of high purity and ultrafine single crystalline magnesia as described in detail below. is not.

[0017]

SUMMARY OF THE INVENTION The present invention relates to a method for preparing a nickel / magnesia catalyst suitable for steam reforming of hydrocarbons and the like. There are various problems in the technology of.

That is, the catalytic activity is superior to other systems, but there is still room for improvement, carbon precipitation occurs, the life is short, the heat resistance is low, and the catalyst is deactivated by sintering. However, there are problems such as scattering of alkali and the like causing corrosion of reactors and piping, weakness against chemical corrosion by high temperature steam of alkali carbonate, and low mechanical strength of catalyst pellets. The present invention solves these problems all at once.

[0019]

The present invention provides a highly active, high-strength nickel / magnesia system under the following specific conditions using high-purity ultrafine single crystal magnesia, a nickel compound and, if necessary, an organic solvent. The present invention relates to a method for preparing a catalyst, which is suitable for steam reforming of hydrocarbons, methanation of synthesis gas, and the like. The catalyst prepared according to the present invention can solve all the above problems.
The method for preparing the catalyst of the present invention will be described in detail below.

The carrier raw material for catalyst preparation useful in the present invention is high-purity ultrafine single crystal magnesia (purity 99.9% or more) having an average particle diameter of 100 to 2000Å (BET specific surface area diameter).

As such magnesia, for example, magnesia produced by a vapor phase oxidation method, which is synthesized by oxidizing magnesium vapor and an oxygen-containing gas in a turbulent diffusion state, is suitable. Although it is possible to produce magnesia having an average particle size of 100Å or less and is also useful in the present invention, it is currently not practical because of the high production cost and the difficulty in handling ordinary powder. .. When the average particle size is 2000 Å or more, the specific surface area of the carrier is 5 m ² / g.
The following is not preferable because the catalyst activity is reduced. Therefore, the preferable range of the average particle size of the high-purity ultrafine single crystal magnesia is 100 to 2000Å (BET specific surface area 6 to 170 m ² / g), and particularly 300 to 700Å
The range of (BET specific surface area 20 to 80 m ² / g) is suitable.

The nickel compound raw material for preparing the catalyst of the present invention is generally one that dissolves in an organic solvent and thermally decomposes at a temperature of 400 ° C. or less to produce nickel oxide, or generally at a relatively low temperature, for example, 300 ° C. or less. It is desirable that it melts at 1, and thermally decomposes at 400 ° C. or less to produce nickel oxide.

For example, as the former, bisacetylacetonato nickel, bisdimethylglyoximato nickel, dicarbonylbistriphenylphosphine nickel, dicarbonylbiscyclopentadienyl nickel,
Examples thereof include biscyclopentadienyl nickel, acetylene biscyclopentadienyl nickel, biscyclooctadiene nickel, nickel alkoxide, nickel acetate, nickel nitrate, and their crystalline hydrates.

Further, as the latter, bisacetylacetonato nickel, diethyl bipyridine nickel, dicarbonylbistriphenylphosphine nickel, dicarbonylbiscyclopentadienyl nickel, tetrakisisocyanobutyl nickel, dibromobisallyl nickel, nickel nitrate and their compounds. Crystal water salt can be mentioned.

If necessary, an organic solvent is used. In that case, any organic solvent may be used as long as it does not contain 1% or more of water and dissolves the former nickel compound.

For example, alcohols such as methanol, ethanol and propanol, hydrocarbons such as hexane, heptane, cyclohexane and ether, benzene,
Aromatic compounds such as toluene and xylene are preferable,
From the viewpoint of economy, it is more preferable that the nickel compound is dissolved in a large amount.

Using these materials, the steps from supporting to tablet forming are the supporting method (solvent supporting method: JP-A-2-2).
45239 or solvent-free supporting method: Japanese Patent Application No. 2-275
No. 371), so it will be described separately.

(1) Solvent loading method Using the above three kinds of raw materials, that is, high-purity ultrafine single crystal magnesia, the former nickel compound and an organic solvent, a nickel compound is loaded on the surface of magnesia particles by the incipient wetness method. , Prepare the catalyst.

In this case, the amount of nickel compound supported is 0.1 as metal nickel on the magnesia carrier.
The range of ˜50% by weight is preferred. If it is less than 0.1% by weight, the catalytic activity is low, and if it is more than 50% by weight, the corresponding catalytic activity cannot be obtained and it is economically disadvantageous.

50 to 1 of a slurry containing magnesia, a nickel compound and an organic solvent thus prepared was used.
Dry at 50 ° C. to remove organic solvent. At that time, it is desirable to recover and reuse the organic solvent from the economical aspect.

Next, the obtained nickel compound-supported magnesia powder is subjected to a thermal decomposition treatment in air at a relatively low temperature of 400 ° C. or lower. This temperature is determined in consideration of the thermal decomposition temperature of the nickel compound, its rate, and safety.
At a temperature of 400 ° C. or higher, a strong solid solution of nickel and magnesia is formed, which makes it difficult to carry out reduction treatment with hydrogen in the following steps.

Magnesia powder carrying nickel oxide prepared in this manner is mixed with magnesium stearate in an amount of 0.2 to
Add 3.0% by weight, mix, and mold (tablet) into small particles, pellets, cylinders, or rings to form nickel oxide / magnesia (NiO / M
gO) based catalyst material tablets are obtained.

The magnesium stearate is not particularly limited as long as it is commercially available, but fine powder is desirable. When the amount of magnesium stearate added is less than 0.2% by weight, the effect of the addition is small and it is difficult to obtain a normal tablet, and the yield is reduced. Further, if it exceeds 3.0% by weight, there is no problem in the moldability of the tablet, but the stearic acid component removed in the subsequent heat treatment step becomes too much and the strength is lowered, which is not preferable.

(2) Solvent-Free Support Method The above-mentioned two kinds of raw materials, that is, high-purity ultrafine single crystal magnesia and the nickel compound of the latter are first sufficiently mixed.
At this time, as long as it is well mixed, the mixing method is not limited,
A normal dry mixing method may be used.

Next, the obtained mixed powder is molded by using a usual dry molding machine. Any molding machine may be used as the molding machine in this case, for example, a dry compression molding machine such as a tableting machine or a briquetting machine. Also, the shape of the molded body (tablet) at that time is
It may be spherical, cylindrical, ring-shaped or small granular, and the size is usually within 20 mm. In this case as well, the preferable range of the amount of nickel supported is the same as in (1).

The tablets thus obtained are heated and held in the air at a temperature higher than and close to the melting point of the nickel compound to uniformly melt and disperse the nickel compound component on the surface of magnesia. Further, in the same atmosphere, the thermal decomposition treatment is carried out at a temperature higher than the thermal decomposition temperature of the nickel compound raw material and at a temperature of 400 ° C. or lower until complete decomposition.

For example, the magnesia (100 to 20)
00 Å) and bisacetylacetonato nickel, after thoroughly mixing and molding them by dry method,
It is heated and held in air at 250 ° C. for at least 10 minutes, and further heat-treated in the same atmosphere at a temperature of 300 to 400 ° C. for at least 10 minutes.

The thus-prepared magnesia material supporting nickel oxide is pulverized if necessary, and then 0.2 to 3.0% by weight of magnesium stearate is added and mixed, and this is mixed into small particles, pellets or cylinders. To obtain nickel oxide / magnesia (NiO / MgO) -based catalyst material tablets by molding into a ring shape or a ring shape. In addition, the range of the kind and addition amount of magnesium stearate in this case is the same as that of (1).

The NiO / MgO-based catalyst material tablet obtained as described in (1) or (2) above is subjected to a heat treatment at 550 to 800 ° C. for at least 10 minutes in a reducing gas atmosphere such as hydrogen gas to obtain the object. A highly active and high strength nickel / magnesia catalyst is obtained.

If the temperature is lower than 550 ° C., the mechanical strength of the catalyst, for example, in the case of a cylinder, the axial compressive strength does not reach the target of 500 kgf / cm ² . On the other hand, when the temperature exceeds 800 ° C, the strength becomes unnecessarily high and the activity decreases due to the decrease in porosity. Further, when the heat treatment time is 10 minutes or less, the effect of the heat treatment is small, so that normally 1 to 3 hours is most suitable.

If desired, in order to obtain higher catalytic activity, it is desirable to carry out the following reduction treatment immediately before use in the reactor. That is, in a reducing gas atmosphere such as hydrogen gas, activation is performed by performing a first reduction treatment at a temperature of 350 to 450 ° C. and a second reduction treatment at a temperature of 600 to 750 ° C.

When the catalyst of the present invention is used in a steam reforming reaction or the like, an ordinary reactor such as a tubular flow reactor (fixed bed type) or a fluidized bed type reactor is used, and the ordinary reaction is carried out. Although it can be carried out under the conditions, and is not particularly limited, since the catalyst of the present invention has extremely high activity, it is possible to lower the reaction temperature than usual, and also the space velocity (GHSV) is extremely increased. Alternatively, in the case of steam reforming, it is possible to reduce the steam / carbon ratio.

[0043]

[Function] High-purity ultrafine single crystal magnesia particles are cubic crystals, and Mg ²⁺ ions and O ^2-
The ion is in the activated state as a tri-coordinated unsaturated ion. The smaller the magnesia particles are, the more Mg ²⁺ ions and O ²⁻ ions in this state increase, and this directly affects the catalytic activity.

The high basicity of magnesia also makes the carbon deposition rate extremely low without the need for the addition of alkali compounds (potassium compounds) that are commonly used in conventional catalysts. Even if there is carbon deposition, since magnesia is an ultrafine powder, the deposited carbon particles are also extremely fine, and the deposited carbon is easily gasified and does not accumulate on the catalyst.

Further, since magnesia is highly basic, it also has a strong resistance to chemical attack by high temperature steam of alkali carbonate.

On the other hand, in the case of the solvent loading method, since the nickel compound is loaded on the magnesia surface using an organic solvent,
It does not undergo a chemical change due to hydration, etc., and the shape and size of magnesia do not change even after the catalyst preparation, and the activated state can be maintained. Further, since the nickel compound is supported by the incipient wetness method, the nickel dispersion is very good and the active nickel surface area per unit weight of the catalyst is large. The same applies to the solvent-free supporting method.

Further, the nickel compound is added at a relatively low temperature of 4
Since it is thermally decomposed at a temperature of 00 ° C. or lower to generate nickel oxide (NiO), free NiO is uniformly supported on the magnesia surface. Further, by adding magnesium stearate to the nickel oxide-supported magnesia powder, the moldability of the catalyst material tablet is improved, and a strong tablet can be obtained.

Furthermore, since the NiO / MgO-based catalyst material tablet in this state is subjected to heat treatment in a reducing gas atmosphere such as H ₂ gas in the range of 550 to 800 ° C. for at least 10 minutes, NiO is completely reduced to metallic Ni. ,
The solidification of MgO and NiO does not proceed, the catalyst activity is maintained as it is, and the catalyst strength increases as the heat treatment temperature increases by sintering.

The nickel / magnesia (Ni / MgO) -based catalyst prepared as described above has characteristics of high activity and high strength, but when left in the air, metallic nickel (Ni) on the surface is left. Is nickel oxide (NiO) again
As described above, it is desirably subjected to reduction treatment in the reaction tube immediately before use.

[0050]

【Example】

[Examples and Comparative Examples] Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples. Example 1 A high-purity ultrafine powder single crystal magnesia (average particle size 500Å, BET specific surface area size) 100 g produced by a gas phase oxidation method was added with a toluene solution of bisacetylacetonato nickel (commercially available product), and by an incipient wetness method. After supporting the nickel compound, the toluene was removed while suctioning at 90 ° C. The dried product was pyrolyzed at 400 ° C. for 6 hours in the air to completely decompose the acetylacetone component. The amount of nickel supported on the NiO / MgO catalyst thus obtained was analyzed by an atomic absorption method. As a result, it was 18% by weight as metallic nickel with respect to magnesia.

Further, 0.5% by weight of commercially available magnesium stearate was added to and mixed with this NiO / MgO-based catalyst material, and the mixed powder was compression molded into φ10 × 10 mm at 650 ° C. under H ₂ gas atmosphere. Heat treatment was performed for 2 hours. An axial compressive strength test of this cylindrical tablet was performed.

Next, a part of the obtained molded catalyst was roughly crushed into particles of about 2 mm, and about 20 g of this was set in an ordinary fixed bed type flow reactor (φ10 × 300 mm). First, H ₂ gas 3
First reduction treatment under the conditions of 00 Nml / min, 400 ° C., pressure 1 atm., 2 hours, and H ₂ gas 300 Nml / min, 725
After the second reduction treatment under the conditions of ℃, pressure of 1 atm. And 1 hour, a mixed gas of H ₂ O / CH ₄ molar ratio of 2.5 was added to 4000.
Flow was carried out under the conditions of Nml / min, reforming temperature of 670 ° C. and pressure of 1 atm. The obtained reformed gas was analyzed by gas chromatography. The results and strength test results are shown in Table 1 together.
Shown in. The equilibrium conversion rate under these reforming conditions was 91.2%.
Is.

[0053]

Example 2 High-purity ultrafine single crystal magnesia (average particle size: 500Å) and bisacetylacetonato nickel (commercially available) powder were weighed in predetermined amounts, and sufficiently dry-mixed using a ball mill type mixer. It was molded into a cylinder of φ5 × 5 mm using a conventional tableting machine. At this time, the amount of nickel supported was 18% by weight as metallic nickel with respect to magnesia. This was once heat-treated in air at 230 ° C. for 30 minutes, further heated to 300 ° C. in the same atmosphere gas and subjected to thermal decomposition treatment for 6 hours. 590 this heat-treated product
After pulverizing to less than μm, 0.5% by weight of commercially available magnesium stearate was added to and mixed with this powder, and the mixed powder was molded into a tablet of φ10 × 10 mm using a compression molding machine. Thereafter, as in Example 1, heat treatment in H ₂ gas, compressive strength test, reduction treatment and steam reforming test were performed. The results are shown in Table 2.

Comparative Example 1 Catalyst preparation, reduction treatment and steam reforming test were conducted in the same manner as in Example 1 except that commercially available liquid phase magnesia (average particle size 500Å) was used in place of the high purity ultrafine powder single crystal magnesia. And a catalyst strength test was conducted. The results are shown in Table 3.

[0056]

[0057]

Examples 3 to 4 High-purity ultrafine powder single crystal magnesia average particle size of 100Å or 2000Å instead of 500Å
Catalyst preparation, reduction treatment, steam reforming test and strength test were conducted in the same manner as in Example 2 except that (Example 3 or 4 respectively) was used. The results are shown in Table 4.

Examples 5 to 6 and Comparative Examples 2 to 3 A nickel loading of 18% by weight was adjusted to 0 (Comparative Example 2), 0.
1 (Example 5), 49.9 (Example 6) or 60.
Catalyst preparation, reduction treatment, reforming test and strength test were conducted in the same manner as in Example 2 except that the amount was changed to 0 (Comparative Example 3)% by weight. The results are shown in Table 5.

[0060]

[0061]

Examples 7 to 9 and Comparative Examples 4 to 5 The amount of magnesium stearate added was 0.5% by weight.
(Comparative Example 4), 0.3 (Example 7), 1.0 (Example 8), 3.0 (Example 9) or 5.0 (Comparative Example 5)
Catalyst preparation, reduction treatment, reforming test and strength test were conducted in the same manner as in Example 2 except that the content was changed to% by weight. The results are shown in Table 6.

[0063]

Examples 10 to 11 and Comparative Examples 6 to 7 The heat treatment temperature of 650 ° C. under H ₂ gas atmosphere was changed to 500 ° C.
(Comparative Example 6), 550 ° C (Example 10), 800 ° C (Example 11) or 850 ° C (Comparative Example 7), except that the catalyst preparation, reduction treatment and reforming test were carried out in the same manner as in Example 2. And a strength test was conducted. The results are shown in Table 7.

[0065]

[0066]

Comparative Examples 8 to 9 Except that the heat treatment in H ₂ gas atmosphere was replaced with heat treatment in air (Comparative Example 8) which was an oxidizing gas atmosphere or nitrogen (Comparative Example 9) which was a neutral gas atmosphere. In the same manner as in Example 2, catalyst preparation, reduction treatment, reforming test and strength test were conducted. The results are shown in Table 8.

In any of the above examples, no catalyst pulverization due to carbon deposition and strength reduction was observed in the catalyst after the reaction.

[0069]

Industrial Applicability The catalyst preparation method of the present invention relates to an improved preparation method of a nickel / magnesia-based catalyst suitable for steam reforming of hydrocarbons, methanation of synthesis gas, and the like. When prepared, the following effects are noticeable. That is, the catalytic activity is high,
It is close to the equilibrium conversion, even though it is much more severe than normal reaction conditions. No carbon deposition is observed and the life is long. High heat resistance and no deactivation. No scattering of alkali, etc., and corrosion of reaction tubes and piping does not occur. No chemical attack by high temperature steam of alkali carbonate. The mechanical strength of the catalyst pellets is high, and pulverization does not occur even after long-term use.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Oue 5 1978, Kozugushi, Ube City, Yamaguchi Prefecture Ube Kosan Co., Ltd.

Claims (1)

[Claims] 1. A high-purity ultrafine single-crystal magnesia having an average particle diameter of 100 to 2000Å (BET specific surface area diameter) and a nickel / magnesia (Ni / MgO) system consisting of 0.1 to 50% by weight of nickel with respect to magnesia. In the method for preparing a catalyst, a nickel compound is supported on a carrier magnesia, and then the nickel compound is subjected to a thermal decomposition treatment to obtain a nickel oxide-supported magnesia powder, and then 0.2 to 3.0 parts by weight of magnesium stearate is added to the magnesia powder. %, And after shaping into the desired shape, add 5% in a reducing gas atmosphere.
A method for preparing a highly active and high-strength nickel / magnesia-based catalyst, which comprises performing heat treatment at 50 to 800 ° C.