JPH05186203A - Catalytic element for steam reforming - Google Patents

Abstract

PURPOSE:To provide the subject catalytic element capable of retaining catalytic activity even under the conditions for steam reforming reaction, designed to resolve the temperature difference between a reforming tube and catalytic granular layer, which has been a problem in conventional steam reforming techniques. CONSTITUTION:A porous alumina catalytic carrier layer 2 is attached to the inner surface of a metallic reforming tube 1 and nickel fine particles as catalytically active substance 3 is carried on the layer through impregnation process. The method for forming the catalytic carrier layer of the present invention is e.g. as follows: a metallic material is coated with a pasty coating agent consisting mainly of ceramics/followed by heating and drying; ceramic spray coating; a baked ceramic porous form is jointed to a metallic material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic element used in a steam reforming reaction operation for reacting a hydrocarbon with steam to produce hydrogen, syngas and the like.

[0002]

2. Description of the Related Art The steam reforming of hydrocarbons is an operation in which hydrocarbons such as natural gas and naphtha are reacted with steam in the presence of a catalyst at a temperature of about 400 to 850 ° C to produce hydrogen and synthesis gas. is there. Although this reaction has been used for a long time, it has recently been used for the production of hydrogen for fuel cells due to its excellent energy balance.

Since this steam reforming reaction is an endothermic reaction that requires a large amount of heat to be supplied from the outside, the structure of the reformer has so far been modified by filling the inside of the reforming tube with catalyst particles. A method has been adopted in which heat is radiated or convectively transferred from the outside of the tube by combustion gas or the like. At that time, the catalyst particles to be filled in the reforming tube are those obtained by impregnating a particulate porous catalyst carrier made of alumina, magnesia, etc. with fine particles such as nickel and ruthenium which are catalytically active components by an impregnation method or the like. It is used. Since these use a porous carrier such as alumina, they are relatively stable even at the operating temperature of the steam reforming operation. FIG. 2 is a diagram schematically showing the inside of a conventional filling type reforming tube using the above catalyst particles.

The process gas 4, which is a mixture of hydrocarbon and steam, receives heat from the outside of the reforming tube 1 while passing through the gap between the catalyst particles 5 filled in the metal reforming tube 1. It is reformed into a hydrogen-rich gas by being heated. However, in this case, although the turbulence of the gas flow is amplified due to the presence of the catalyst particles and the heat transfer characteristic in the reforming tube 1 is realized as a considerably high value for gas heating, the reaction heat of steam reforming is extremely large. Therefore, a large temperature difference occurs between the inner surface of the reforming tube 1 and the center of the catalyst layer due to the heat transfer resistance inside the catalyst particle layer and the heat transfer resistance near the inner wall of the reforming tube 1. The existence of this temperature difference means that the surface temperature of the reforming tube 1 has to be increased by an extra amount in order to obtain the desired reactivity, which is a big problem in the design of the apparatus. In addition, since the packed bed of catalyst particles has a large heat capacity, it has been a limiting condition for improving the startup speed and reaction load dynamic characteristics.

By the way, also in the reactions other than the steam reforming described above, the same problem exists in the reactor of the catalyst particle filling system involving heat exchange. In order to eliminate the drawback, a concept called a catalyst element that simultaneously performs heat exchange and reaction has been proposed in recent years. The catalyst element referred to here is one in which the catalyst is directly attached to the metal material, and specifically, the catalyst is attached to the wall surface of the reaction tube or the metal fin to which the catalyst is attached is attached to the surface of the reaction tube. Are being considered. According to this, since it is possible to eliminate the heat transfer resistance in the bed and the heat transfer resistance in the vicinity of the tube wall as in the case of the catalyst particle packed bed, the temperature between the reaction tube and the catalyst particle layer, which has occurred conventionally, can be eliminated. Most of the difference can be eliminated. In addition, heat can be directly supplied from the surface of the reaction tube to the part where the catalytic reaction occurs by heat conduction, and conversely, heat can be removed from the catalytic reaction part to the reaction tube, so that the load dynamic characteristics of the reaction can be improved. It is also advantageous in terms of improvement.

[0006]

However, the catalyst element in which the catalyst is directly adhered to the metal material has a great advantage as compared with the conventional catalyst particle filling method as described above. It has not reached the established level like the particulate catalysts commonly used in industry. Although methods for producing catalyst elements for methane synthesis reaction and methanol decomposition reaction have been proposed so far, catalyst elements that can be used in the steam reforming reaction targeted by the present invention have been tried so far. Absent. As a specific example, a method of depositing a nickel porous body on a metal surface by utilizing the difference in ionization tendency has been proposed for a methane synthesis reaction. When it is used at such a high temperature level, a so-called sintering phenomenon occurs, in which nickel agglomerates, and as a result, the surface area of nickel decreases and the catalyst function is lost. This is because the porous body of the catalyst element is composed of nickel itself and does not have a catalyst carrier such as alumina. Therefore, an object of the present invention is to provide a catalytic element that can maintain catalytic activity even under conditions of steam reforming reaction.

[0007]

The above object of the present invention is to form a porous catalyst carrier layer on the surface of a metal material by adhesion.
This can be achieved by supporting a catalyst active substance on the catalyst carrier layer by an impregnation method to form a steam reforming catalyst element.

As a method for forming the catalyst carrier layer of the present invention, a paste-like coating material containing ceramic as a main component is applied to the surface of a metal material and then heated and dried, a method by ceramic spraying, and a firing method. There is a method of joining a ceramic porous body to a metal material.

[0009]

Since the catalyst element having the above-mentioned structure has the catalyst carrier layer, sintering can be suppressed as compared with the case where the porous body is composed of only the catalytically active substance, and the steam reforming reaction can be suppressed. It can be used even under high temperature conditions such as.

[0010]

EXAMPLE FIG. 1 is a diagram showing a steam reforming catalyst element according to the present invention. A porous alumina catalyst carrier layer 2 is adhered and formed on the inner surface of a reforming tube 1 made of a metal material,
A large number of nickel fine particles are supported as the catalytically active substance 3 on the catalyst carrier layer 2. The process gas 4, which is a mixture of hydrocarbon and steam, is reformed into a hydrogen-rich gas by the catalyst carried on the catalyst carrier layer 2 while being heated while passing through the reforming pipe 1 of the metal material. ..

The catalyst is carried by a known impregnation method. That is, the metal material having the catalyst carrier layer adhered was dipped in an aqueous nickel nitrate solution having a predetermined concentration, dried and then fired. At this stage, nickel, which is a catalytically active substance, exists in the state of nickel oxide, so it is used after being reduced in use.

According to the catalytic element of the present invention as shown in FIG. 1, the surface of the reforming tube 1 is formed so that the catalytically active substance 3 capable of maintaining the activity under the reaction conditions of steam reforming is carried on the catalyst carrier layer 2. The heat is directly supplied from the surface of the reforming tube 1 to the portion of the catalytically active substance 3 where the reforming reaction has occurred by heat conduction. Effect of Example

As a result, the temperature difference between the reforming tube 1 and the catalyst particle layer, which has been a problem in the conventional steam reforming, can be eliminated, and even if the reforming tube temperature is lower than in the conventional case, it is about the same. The reactivity of will be obtained. The fact that the temperature of the reforming tube can be lowered while maintaining the reactivity has a great significance in the design of the apparatus, and thereby a highly safe and inexpensive reformer can be provided. Further, since heat can be directly supplied from the surface of the reforming tube to the portion where the catalytic reaction is occurring by heat conduction, it is extremely advantageous in terms of improvement of load dynamic characteristics. The steam reforming catalyst element can be used in a form other than the above.

For example, when a catalyst carrier layer is formed on a plate-shaped metal material to manufacture a catalyst element, a plate type reformer can be realized by stacking the catalyst elements with a predetermined gap. Further, it is also effective to use a corrugated plate-shaped metal material to configure the catalyst element and use it as an internal fin of the reformer.

As a method of forming the catalyst carrier layer, a paste-like coating material containing ceramic as a main component is applied to the surface of the metal material, followed by heating and drying, a method by ceramic spraying, and a ceramic porous formed by firing. There is a method of joining the body to a metal material.

[0016]

According to the catalytic element for steam reforming of the present invention, the catalyst whose activity is maintained even under the reaction conditions of steam reforming can be formed in a state of being in close contact with the surface of the reforming tube, and the heating surface Therefore, it is possible to realize a reaction system in which heat can be directly supplied to the catalyst portion where the reforming reaction is occurring by heat conduction. If a reformer is constructed by using the catalyst element, a reformer having high safety and good load response can be provided at low cost, and its industrial utility is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a steam reforming catalyst element according to the present invention.

FIG. 2 is a schematic diagram showing a conventional catalyst particle filling type reforming tube filled with catalyst particles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reforming tube 2 ... Catalyst carrier layer 3 ... Catalyst active substance 4 ... Process gas 5 ... Catalyst particles

Claims (4)

[Claims] 1. A catalytic element for steam reforming, characterized in that a porous catalyst carrier layer is adhered and formed on the surface of a metal material, and a catalytically active substance is carried on the catalyst carrier layer by an impregnation method. 2. The steam reforming agent according to claim 1, wherein a catalyst carrier layer is formed by applying a paste-like coating agent containing ceramic as a main component on the surface of the metal material, and then heating and drying. Catalytic element. 3. The catalyst element for steam reforming according to claim 1, wherein the catalyst carrier layer is formed by ceramic spraying. 4. The catalyst element for steam reforming according to claim 1, wherein the catalyst support layer is formed by joining the fired ceramic porous body to a metal material.