JP3260411B2 - Hydrocarbon steam reforming catalyst and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for producing synthesis gas or hydrogen by steam reforming hydrocarbons.

[0002]

2. Description of the Related Art The reaction of reforming hydrocarbons with steam is industrially carried out on a large scale as a reaction for producing synthesis gas or hydrogen. Nickel-based catalysts are generally used in this reaction. However, when higher hydrocarbons are reformed with steam, the steam / carbon ratio (e.g., (Molar ratio) also tends to cause carbon deposition, and thus improvements have been attempted.

On the other hand, noble metal-based catalysts are considered to be less likely to cause carbon deposition, and their development has been attempted as a substitute for nickel-based catalysts. Catalysts containing rhodium or ruthenium as a main component have been mainly studied, and are particularly effective. As such, various ruthenium-based catalysts have been proposed.

[0004] Ruthenium is usually used by supporting a metal on a carrier, because it is an expensive metal or its surface area must be increased for its effective use.
Alumina, zirconia, or the like is used as the carrier. Alumina has long been used as a catalyst carrier for many years, has a track record of being industrially used as a nickel catalyst carrier for hydrocarbon steam reforming, and many studies have been conducted as ruthenium-based catalyst carriers. Has been done,
Its performance is at the same level as that of a normal nickel-based catalyst. Further, in order to utilize it for steam reforming of higher hydrocarbons, it is necessary to take measures for preventing carbon deposition, and the addition of various cocatalyst components is being studied.

[0005] For example, as a co-catalyst component for forming a catalyst resistant to steam reforming of higher hydrocarbons, JP-A-56-813
Japanese Patent Application Laid-Open No. 92-3192 discloses the addition of cerium oxide.
No. 8239 discloses the addition of barium oxide, and British Patent GB1301836 discloses the addition of an alkaline earth metal oxide as a co-catalyst component for providing a catalyst for suppressing carbon deposition. JP-A-57-4232 proposes addition of alkali, alkaline earth metal oxide and silica, and JP-A-60-147242 proposes addition of lanthanum oxide and silver oxide, respectively. Inferior to zirconia supported catalysts.

[0006] On the other hand, zirconia has no industrial achievement as a catalyst carrier, but is said to have an effect of activating H ₂ O. Particularly, zirconia is used for fuel cells by steam reforming hydrocarbons. Various studies have been made on the use of ruthenium catalyst carriers as hydrogen production catalysts. Among them, various co-catalyst components are added to make the catalyst highly active, durable in high-grade hydrocarbon steam reforming, or low in carbon deposition. For example, the addition of cobalt or manganese is disclosed in EP-A-406896, and the EP-A-4 EP 406,896 discloses the addition of cobalt or manganese.
The addition of yttrium oxide to 14573 is disclosed in
JP-A-2879 proposes the addition of nickel, lanthanum and other metals, and JP-A-2-43950 proposes the addition of yttrium oxide, magnesium oxide and cerium oxide. However, there are problems such as inferior properties or low mechanical strength.

[0007]

The alumina carrier is inexpensive,
It has properties suitable for a hydrocarbon steam reforming catalyst carrier such as high heat resistance and excellent mechanical strength, and its use as a ruthenium catalyst carrier for reforming has been studied.
Its reforming activity is at the same level as nickel-based catalysts, and for practical use, it is necessary to form a catalyst with characteristics that nickel-based catalysts do not have. On the other hand, when the zirconia carrier is used as a hydrocarbon steam reforming catalyst, the zirconia carrier has a property of activating H ₂ O and thus exhibits an excellent effect in performance, but is expensive and inferior. It has problems such as poor moldability and poor mechanical strength, so it is not suitable for use as an industrial catalyst except for special applications, and in order to obtain a preferred hydrocarbon steam reforming catalyst carrier, it has properties as zirconia. It is desired to develop a carrier which does not lose its properties, is inexpensive like alumina, and has excellent mechanical strength.

[0008]

Means for Solving the Problems The inventor of the present invention has been studying hydrocarbon steam reforming catalysts for some time, but as one of them, noble metal catalysts are less likely to cause carbon deposition than nickel catalysts. Focusing on the fact that it has a tendency, we have been conducting research for its practical use, and among them, alumina and zirconia as hydrocarbon steam reforming catalyst carriers have advantages and disadvantages, respectively. In view of this, studies have been repeated to make use of the advantages of both carriers, but using alumina as a carrier and adding zirconia as a co-catalyst, a carrier having excellent properties of both carriers can be obtained, The catalyst in which ruthenium is impregnated on this carrier not only exhibits almost the same performance as the catalyst in which zirconia itself is used as a carrier, but also shows that when a rare earth metal oxide is further added as a co-catalyst component. On to become a highly active catalyst, it has been found that thermal excellent catalysts with improved durability of activity against impact is obtained.

Addition of zirconia to an alumina carrier cannot provide a carrier having excellent performance simply by using zirconia itself or a zirconia compound as an arbitrary zirconia precursor. A ruthenium-supported catalyst with zirconyl nitrate added to alumina is not only low in activity for hydrocarbon steam reforming reaction, but also has a negative co-catalyst that tends to decrease its activity when the reaction temperature is increased. Although the catalyst exhibited an effect, the catalyst obtained by supporting ruthenium on a carrier to which zirconia sol was added was highly active, having not only performance almost comparable to a catalyst using zirconia itself as a carrier, but also a further component. Of ruthenium on a carrier obtained by adding a rare earth metal oxide to zirconia-added alumina as a catalyst It represents an even higher activity, not only a high activity especially at high temperatures, confirmed to be excellent catalysts durability of activity against thermal effects, thereby completing the present invention.

The amount of zirconia sol added is 0.2 to 20.% when expressed as zirconia with respect to the total weight of the catalyst.
0 wt%, and preferably 0.5 to 10.0 wt%. If the addition amount is 0.2 wt% or less, the effect of zirconia as a cocatalyst is insufficient.
If the content is 0.0 wt% or more, not only the cocatalyst effect corresponding to the added amount cannot be expected, but also the carrier becomes expensive, and peeling of the supported zirconia cannot be ignored.

Since zirconia sol is added as a co-catalyst, it is preferably present on the surface of the catalyst. By selectively attaching the zirconia sol to the surface, expensive zirconia sol can be effectively used. It is preferable to add by immersing in zirconia sol or spraying zirconia sol on an alumina carrier. It is also possible to add alumina or alumina precursor powder by kneading with zirconia sol, but this is not practically preferable.

The zirconia sol has a spherical particle shape or a particle shape in which spheres are linearly connected.
Although sols of any shape can be used, sols of the latter shape are preferred, and the size of the particles is 50 to
2,000 angstroms, preferably 100 to 1,
In the PH region where the zirconia sol is stabilized, any sol on the acidic side, neutral or alkaline side can be used.

The zirconia sol can be added to the carrier simply by dipping the carrier in the zirconia sol or spraying the zirconia sol on the carrier. Usually, a 30 wt% sol aqueous solution can be used as it is. For this purpose, the immersion of the carrier in the sol or the spraying of the sol onto the carrier may be repeated by adding a drying operation in the middle, or if a small amount is sufficient, dilute the zirconia sol with pure water before use. After a predetermined amount of zirconia sol has been applied, it is dried and then fired at 400 to 900 ° C. for several hours.

A rare earth metal oxide is added as another co-catalyst component. The amount of addition is 0.1 to 10% by weight, preferably 0.2 to 10% by weight, when all the catalyst components are converted to oxides.
It needs to be 10.0 wt%, and the amount of addition is 0.1 wt%.
If the content is less than 1 wt%, the effect of improving the performance is insufficient, and if the content is more than 10.0 wt%, no further improvement in performance can be expected because the addition effect reaches a limit, and an economically favorable catalyst cannot be obtained. .

As the rare earth metal oxide, oxides such as lanthanum, cerium, yttrium and the like can be added and used, and the addition is carried out by immersing the carrier in a rare earth metal salt aqueous solution or spraying the aqueous solution on the carrier. The salts that can be used as a raw material are water-soluble, and any salts can be used as long as they do not leave any components that would become catalyst poisons after thermal decomposition on the carrier. Alternatively, nitrates or halides are preferably used for economical reasons. After supporting rare earth metal salts, the support is calcined at 400 to 900 ° C.

The order of addition of zirconia and rare earth metal oxide to alumina has an effect on catalytic performance. It is preferable to add zirconia first and then add rare earth metal oxide. Since the effect of improving the performance is considerably recognized even if the substance is added first, a method for producing a carrier by prior addition of a rare earth metal oxide can also be included in the present method for producing a catalyst.

As the carrier, an ordinary inorganic heat-resistant oxide other than alumina can be used, but an alumina carrier is preferred in consideration of the price or the industrial achievement as a hydrocarbon steam reforming reaction catalyst carrier. Alumina having any crystal structure can be used as long as it is a commonly used alumina carrier, but it is preferably α-alumina, which does not change its structure even at high temperatures, and is inert. The carrier is used as a tablet, extruded or spherical molded product.

The catalyst is produced by supporting ruthenium on a carrier in which zirconia and a rare earth metal oxide are added to α-alumina, and improving the mechanical strength of the carrier or making the carrier itself basic. In order to improve the ability to prevent precipitation, an alkaline earth metal oxide as a third promoter component can be added to the alumina carrier in advance.

The alkaline earth metal oxide as the third co-catalyst component is an oxide such as calcium, barium or magnesium, preferably calcium or barium oxide, and its addition amount is 2.0 to 50.0 wt%. , Preferably 5.0 to 30.0 wt%, and 2.0 wt%
%, The effect is insufficient, and 50.0 wt%
In the above, a carrier having sufficient mechanical strength cannot be obtained. On the other hand, the addition of the alkaline earth metal oxide to the alumina carrier requires that the precursor aluminum hydroxide be added to the alkaline earth metal before the alumina carrier is molded. A method of adding and mixing a compound, a method of immersing a carrier in an aqueous solution of an alkaline earth metal compound before adding zirconia to a molded carrier, or a method of dissolving an alkaline earth metal compound in an aqueous solution of a sol when adding a zirconia sol and simultaneously adding alumina. The method can be carried out by adding to the carrier, drying after the end of the attachment operation,
Bake at ~ 1350 ° C for several hours.

It is preferable that the alkaline earth metal oxide and the alumina form a compound. At a temperature of 700 ° C. or lower, the compound is insufficient to form a compound and cannot be a good carrier. , The surface area becomes too small, so that an excellent carrier cannot be obtained.

Ruthenium is impregnated next to the alumina carrier to which zirconia, rare earth metal oxide and, if necessary, the alkaline earth metal compound are added. Ruthenium as a catalytically active component is intensively impregnated on the surface of the carrier. It is essential for effective utilization, and any method can be used as long as it enables ruthenium to be attached to the surface, such as an impregnation method, an immersion method, and a spray method. It is necessary to use water-soluble compounds such as halogen compounds and ruthenates, and any compound can be used as long as it does not leave a catalyst poison after firing in the catalyst. It is dried after impregnation, and then calcined at 400 to 700 ° C. for 2 to 4 hours.
02-5.0 wt%, preferably 0.05-2.0 wt%
%, And if the amount is less than 0.02 wt%, the activity is insufficient, and if the amount is more than 5.0 wt%, the catalyst becomes more expensive than is required to improve the activity and is not economical.

The catalyst must be reduced before it is subjected to the reaction, but may be reduced in the liquid phase or gas phase. In the case of the liquid phase reduction, an aqueous solution of potassium formate, formalin, hydrazine, sodium boron hydride or the like is used. 40 ~
The catalyst can be reduced under heating at 80 ° C. In the case of gas phase reduction, the catalyst can be maintained at 100 to 600 ° C and reduced while flowing hydrogen gas. Packed in a pressure-flow reactor and evaluated for its performance by methane steam reforming reaction, it shows excellent performance and has higher activity than a catalyst using alumina or alumina / alkaline earth metal oxide with zirconia added. In particular, the catalyst exhibited excellent activity at high temperatures and also had durability against the thermal influence of the activity.

In other words, the catalyst performance evaluation starts the reaction at a low temperature, and usually ends with the performance measurement at a high temperature. However, in the catalyst of the present invention, after the performance measurement at a high temperature, the reaction temperature is lowered again to reduce the low temperature. When the performance was measured at a low temperature, the re-measured activity at the low temperature was equal to or higher than the activity at the start of the reaction, and the addition of the rare earth metal oxide not only improved the activity of the ruthenium catalyst, but also It was confirmed that the durability against the thermal influence of the activity was also increased, and the present invention was completed.

[0024]

EXAMPLES Next, the contents of the present invention will be described in detail with reference to examples. The performance evaluation described therein was carried out under the following conditions. Conditions for evaluating methane steam reforming reaction performance Amount of catalyst used 25 cc Catalyst size 3/16 in × 3/16 in (tablet product) CH ₄ space velocity 1,200 hr ⁻¹ steam / CH ₄ 3.0 (molar ratio) Pressure Normal pressure reaction Temperature 550-750 ° C. Reaction time Maintained at each measured temperature for 2 hours CH ₄ conversion (%) indicating the performance of the catalyst was calculated by the following formula.

[0025] Here, CO _out : CO concentration (%) at the catalyst layer outlet side CO _{2 out} : CO ₂ concentration (%) at the catalyst layer outlet side CH _{4 out} : CH ₄ concentration (%) at the catalyst layer outlet side Before starting, the catalyst converts H ₂ to space velocity, 500 h
It was reduced at 500 ° C. × 2 hrs while flowing at r ⁻¹ .

Example 1 An appropriate amount of pure water was added to 500 g of aluminum hydroxide, kneaded in a kneader, dried, and then 15 g of graphite was added to the crushed product of a 10 mesh pass.
After mixing, the mixture is tableted into a 3/16 inch × 3/16 inch size, and the tablet is placed in an electric furnace at 1,100 ° C. for 4 hours.
s. A catalyst carrier precursor is prepared by calcining (referred to as carrier A). Separately, 150 cc of 30 wt% zirconia sol stabilized on the acidic side is weighed in a 300 cc beaker, and 60 g of carrier A is weighed. 1. In the sol.
5 hrs. After immersing and then taking out, 110 ° C x 20
hrs. After drying in an electric furnace at 500 ° C. × 1 hr.
It was fired (support B).

Next, an aqueous lanthanum nitrate solution prepared by dissolving 1.6 g of lanthanum nitrate in 8 cc of pure water was attached to 60 g of the carrier B by a spray method, and the mixture was heated at 110 ° C. × 20 hrs.
After drying, 450 ° C. × 1 hr. It was calcined (referred to as carrier C). A catalyst is formed by finally supporting ruthenium on an alumina carrier to which zirconia and lanthanum oxide as a rare earth metal oxide are added. Ruthenium is supported by 1.5 wt.
5% aqueous ruthenium chloride solution was sprayed onto 38 g of the carrier C. After the spraying operation, 110 ° C.
× 20 hrs. Dry, then 500 ° C x 1 in an electric furnace
hr. The catalyst of Example 1 was obtained by calcining, but part of the alumina was converted to α-alumina by X-rays.

This catalyst has the following composition after hydrogen reduction: Ru 0.21 wt% ZrO ₂ 3.20 wt% La ₂ O ₃ 1.04 wt% Al ₂ O ₃ BALANCE Evaluation result of steam reforming performance of methane Was as shown in Table 1.

Example 2 In the preparation of carrier A in Example 1, aluminum hydroxide 5
A catalyst of Example 2 was prepared in the same manner as in Example 1, except that 30 g of calcium carbonate was added in addition to 00 g, and the firing temperature of the tablet was 900 ° C. This catalyst has the following composition after hydrogen reduction: Ru 0.22 wt% ZrO ₂ 3.17 wt% La ₂ O ₃ 1.09 wt% CaO 5.25 wt% Al ₂ O ₃ BALANCE Its methane steam reforming The performance evaluation results are as shown in Table 1.

Example 3 A catalyst of Example 3 was prepared in the same manner as in Example 1 except that the amount of lanthanum nitrate used was changed to 7.0 g in the preparation of the carrier C in Example 1. This catalyst has the following composition after hydrogen reduction: Ru 0.19 wt% ZrO ₂ 3.12 wt% La ₂ O ₃ 4.78 wt% Al ₂ O ₃ BALANCE The methane steam reforming performance evaluation results are shown in Table 1. 1

Example 4 A catalyst of Example 3 was prepared in the same manner as in Example 1 except that 1.6 g of cerium nitrate was used in place of lanthanum nitrate in the preparation of carrier C in Example 1. This catalyst has the following composition after hydrogen reduction: Ru 0.19 wt% ZrO ₂ 3.12 wt% Ce ₂ O ₃ 1.04 wt% Al ₂ O ₃ BALANCE The methane steam reforming performance evaluation results are shown in Table 1. 1

Comparative Example 1 A catalyst of Comparative Example 1 was prepared in the same manner as in Example 1, except that lanthanum oxide as a rare earth metal oxide was not added to carrier B. This catalyst had the following composition after hydrogen reduction. Ru 0.19 wt% ZrO ₂ 3.22 wt% Al ₂ O ₃ BALANCE Table 1 shows the evaluation results of the methane steam reforming performance.

[0033]

[0034]

According to the present invention, zirconia as a co-catalyst is added to an alumina carrier by using zirconia sol as a precursor, and if necessary, an alkaline earth metal oxide is added. The ruthenium catalyst using a carrier to which rare earth metal oxides are added has higher activity than the catalysts to which rare earth metal oxides are not added, especially at high temperatures, and the thermal effect of the activity. The catalyst was also excellent in durability against the catalyst.

Claims (6)

(57) [Claims] A zirconia having a zirconia sol as a precursor, and lanthanum oxide and / or cerium oxide supported thereon as a co-catalyst, wherein the carrier is aluminum oxide containing aluminum oxide or alkaline earth metal aluminate. A hydrocarbon steam reforming catalyst, characterized in that it contains ruthenium as an active ingredient. 2. The hydrocarbon steam reforming catalyst according to claim 1, wherein the content of zirconia is 0.2 to 20 parts by weight per 100 parts by weight of the catalyst. 3. The catalyst according to claim 1, wherein the content of lanthanum oxide and / or cerium oxide is 0.1 to 10.0 parts by weight per 100 parts by weight of the catalyst. 4. The catalyst for hydrocarbon steam reforming according to claim 1, wherein the ruthenium content is 0.02 to 5.0 parts by weight per 100 parts by weight of the catalyst. 5. The alkaline earth metal component in the alkaline earth metal aluminate comprises at least one selected from the group consisting of calcium, barium and magnesium, and the amount of the alkaline earth metal is 100 parts by weight of the carrier in terms of oxide. 2.0-5
The hydrocarbon steam reforming catalyst according to claim 1, which is 0.0 parts by weight. 6. A hydrocarbon steam reforming method comprising: using aluminum oxide or aluminum oxide containing alkaline earth metal alumina as a carrier, carrying a zirconia sol and a rare earth metal compound, and then impregnating a ruthenium compound. For the production of quality catalysts.