JP3017568B2 - Methanol reforming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reforming methanol, and more particularly to a method for reforming methanol capable of increasing the yield of hydrogen and carbon monoxide.

[0002]

2. Description of the Related Art Hydrogen gas is widely used in petroleum refining, desulfurization, ammonia synthesis, synthesis of various chemical products, etc., and is also in great demand for metallurgy industry, semiconductor industry, food industry, and recently in the energy field such as fuel cells. The application to is expected.

As a conventional method for producing hydrogen, there is a method for steam reforming hydrocarbons such as LPG, LNG, and naphtha. However, this conventional method,
In general, there are problems such as a high reaction temperature (800 to 1000 ° C.) and necessity of desulfurization operation, which is suitable for large-scale production of hydrogen gas, but unsuitable for a medium- or small-scale production of hydrogen gas. It is supposed to be.

On the other hand, the production of hydrogen gas using methanol as a raw material has advantages such as easy transportation and storage of methanol as a raw material, the fact that the reaction can be performed at a relatively low temperature, and the desulfurization operation is not required. Not only is there an easy adaptation from large to small devices. Furthermore, since a reformer can be installed adjacent to the hydrogen consuming device and the production line can be integrated even if unmanned operation is performed, hydrogen gas production by methanol reforming is highly expected. . However, since this reaction is a large endothermic reaction, it is difficult to control the reaction temperature, and there is a disadvantage that a satisfactory result cannot always be obtained in terms of reaction efficiency and reaction selectivity.

On the other hand, since the catalytic activity is generally proportional to the size of the surface of the catalyst, it has heretofore been practiced to make the catalyst ultrafine or increase the surface area of the catalyst carrier. From such a viewpoint, the shape of the catalyst is usually powdery or granular. However, with the recent proposal of a heat conduction type catalyst body (Japanese Patent Application Laid-Open No. 47-33785), the wall of the reactor is catalyzed. A proposal for the surface (Japanese Utility Model Application Laid-Open No. 63-16835) was also made.
Attempts have been made to use the reaction heat as little as possible ("Raney-type contact reaction element", surface, secondary
4, pp. 143-153 (1986)).

However, in order to exhibit the function of heat conduction, the heat conduction type catalyst is obtained by supporting the catalyst on the surface of a heat conduction carrier having a planar shape capable of forming a reaction wall. The surface area of the catalyst is significantly smaller than that of the powdery or granular form, which is disadvantageous.

[0007]

On the other hand, in the case of performing a catalytic reaction industrially, if a granular or powdery catalyst is filled in the reaction tower, the temperature near the outer periphery of the reaction tower is high in the diameter direction of the reaction tower and the central part is high. Temperature may be low, so that satisfactory results may not be obtained in terms of the reaction efficiency and the selectivity of the reaction.In particular, in the reforming reaction of methanol, hydrogen and carbon monoxide may not be obtained. There was a drawback that the yield was low.

The inventors of the present invention have conducted intensive studies in order to solve the conventional disadvantages. As a result, when a planar catalyst was used for the methanol reforming reaction, the conventional granular catalyst or powdery catalyst was used. It has been found that the reforming reaction can be carried out more efficiently than in the case of using, and the ratio of hydrogen, which is a product, to carbon monoxide can be increased.

Accordingly, an object of the present invention is to provide a method for reforming methanol which can efficiently decompose methanol and easily increase the amounts of hydrogen and carbon monoxide in a product.

[0010]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
In the methanol reforming method using a catalyst, a continuous catalyst in which an ultrafine methanol decomposition catalyst material is supported on the surface of a continuous metal substrate having an anodized film is used as the catalyst , and methanol is decomposed. The reaction was achieved by a method for reforming methanol, characterized in that the reaction was carried out.

[0011] substrate as a catalyst carrier for use in the present invention,
Must have an anodic oxide coating on at least its surface
It is. Therefore, in the present invention, the substrate is prepared.
As a continuous shaped metal for, it is preferable to use those having at least 10μm aluminum layer on an aluminum or surface.

The surface of the continuous metal is roughened, especially by anodizing, in order to increase the amount of supported catalyst.
Is done .

[0013] and techniques anodized aluminum surface is known, the treatment liquid as for example an aqueous solution of chromic acid, 蓚 acid solution is also known to use a sulfuric acid aqueous solution or the like. The anodizing conditions are preferably set appropriately so as to increase the BET surface area of the aluminum. In the present invention, the temperature of the anodizing treatment liquid is from room temperature to 50 ° C., particularly 30 to 4 ° C.
The temperature is preferably set to 0 ° C. If the temperature is lower than normal temperature, the BET surface area is small. On the other hand, if the temperature exceeds 50 ° C., the dissolution is severe, and it is difficult to form an oxide film economically.

The anodic oxidation treatment time varies depending on the treatment conditions. For example, a 2.5 wt% chromic acid aqueous solution is used as the treatment liquid, the treatment bath temperature is 38 ° C., and the current density is 19.
When it is 0 A / m ² , it is preferably at least 2 hours, particularly preferably at least 4 hours.

The surface of the substrate provided with the alumina surface formed by anodic oxidation as described above can be further treated with hot water or steam at 50 to 350 ° C. to further increase the surface area of the catalyst. In this case, the pH of the hot water is preferably 7 or more, particularly 10 to 12, in order to shorten the processing time.

Although the treatment time of the hot water treatment varies depending on the pH of the hot water, it is preferably at least 1 hour. By treating for about 2 hours, the BET surface area can be significantly increased substantially irrespective of the pH value. it can. After the hot water treatment, baking at 400 to 550 ° C. for 10 minutes to 3 hours is preferable.

In the present invention, an ultra-fine particle catalyst is supported on the surface of the substrate prepared as described above by a known impregnation method or an electrodeposition method to obtain a desired highly active continuous catalyst. Can be. In particular, in the hot water treatment,
70-90 ° C. containing a fine-particle catalyst, preferably 80-90 ° C.
When hot water of 85 ° C. is used, the catalyst can be supported on the substrate surface at the same time as the hot water treatment, so that not only the process of manufacturing a continuous catalyst can be simplified, but also the catalyst activity is particularly excellent. Continuous catalyst body can be obtained,
A method of treating with hot water containing a particulate catalyst, drying, and then calcining at 400 to 550 ° C. is particularly preferred.

In this case, the amount of the ultrafine catalyst contained in the hot water is not particularly limited, but is 0.25 g /
The range is preferably from liter to 1.0 g / liter. If the concentration is too high, it becomes uneconomical, and if it is too low, the required processing time becomes long.

The ultrafine particle catalyst used in the present invention is methanol
Although it is not particularly limited as long as it functions as a catalyst for decomposing hydrogen, it is preferable to select from platinum, palladium, chromium, manganese, zinc, iron, nickel and cobalt. Also, these catalyst substances can be combined.

The particle diameter of the ultrafine catalyst is about 1 nm to 10 nm.
0 nm, preferably in the range of about 1 nm to 50 nm. In addition, the BET surface area of the continuous catalyst is preferably 3000 times or more the apparent surface area of the metal substrate from the viewpoint of catalytic activity.

In the present invention, as described above,
Since a continuous catalyst such as a ribbon, a tube, or a honeycomb can be obtained, these catalysts are appropriately filled in a reaction tower, or a reaction chamber is formed using these catalysts to form methanol. Perform a decomposition reaction. Particularly, a gas phase reaction is preferable.

The pressure of methanol in the reaction chamber is from normal pressure to 30
a kg / m ^2, preferably atmospheric pressure to 20 kg / m ^2. The reaction temperature is from 250C to 800C, preferably from 300C to 450C. The products in this case are hydrogen, carbon monoxide, water and methane. When the reaction temperature is about 400 ° C., hydrogen and carbon monoxide are higher than when a conventional granular catalyst or powdery catalyst is used. The yield of carbon oxide can be greatly increased.

The reason why the yield of hydrogen and carbon monoxide increases as described above in the case of the method of the present invention is not necessarily clear, but can be estimated as follows. Generally, heating for the reaction is performed from the outer wall of the reaction tube.However, when a normal granular catalyst or a powdery catalyst is filled in the reaction tube, the heat conductivity of the filled catalyst is low, so that the vicinity of the outer wall of the reaction tube is low. The temperature is higher than the temperature at the center, and a temperature distribution occurs in the diameter direction of the reaction tube. Therefore, conventionally, the reaction in a considerably wide temperature range proceeds simultaneously, and the selectivity of the reaction is not improved.

On the other hand, when a continuous catalyst is used after being processed into a honeycomb catalyst, for example, since the honeycomb has good thermal conductivity, the temperature distribution does not occur as described above, and the temperature at which the reaction is extremely narrow is obtained. Since the reaction proceeds within the range, the selectivity of the reaction is improved. Further, since it is clear that the contact time of the reaction gas and the product gas with the catalyst (residence time in the reaction chamber) is different between the two, these factors also contribute to the difference in the selectivity of the two reactions. It is estimated to be.

[0025]

According to the present invention, hydrogen and carbon monoxide can be obtained in a high yield by thermally decomposing methanol, and since these products have extremely high purity unlike water gas, It is useful for the synthesis of value-added organic substances and fuel cells.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Embodiment 1 FIG. Computer simulations were performed and compared for the case of the present invention using a continuous catalyst body and the conventional case using a granular catalyst as follows.

FIG. 1A shows a reactor using a continuous catalyst body.
A fin type reactor as shown in FIG. The reactor had a height of each fin of 12 mm, a fin spacing of 5 mm,
The thickness of the fin is 2 mm (FIG. 1b), and the length of the reaction chamber is 3 m in which 20 reaction chambers each having a width of 40 cm are stacked, and a heating medium such as a molten salt for heating is passed between the respective layers. On the other hand, as a conventional type, a fixed-bed reactor having a length of 3 m (FIG. 2 a) was used in which 780 pipes each having a diameter of 24 mm filled with a flow catalyst and embedded in a tube having a diameter of 1 m were used.

In each case, the temperature at the inlet of the reactor is equal to the temperature of the outer wall of the reactor, and the gas flow rate is 7 kg / m ² ···
The relationship between the distance from the inlet of the reactor and the temperature or the conversion was estimated for the reforming reaction of methanol when the reaction temperature was 400 ° C. in seconds. The results of the fin-type reactor at each temperature are as shown in FIG. 3, and those of the conventional reactor are as shown in FIG.

In each figure, the dotted line indicates the vicinity of the outer wall of the reactor,
The lower line is a simulation of the vicinity of the center of the reactor, and the lower line shows the overall conversion.

As is clear from these results, in the case of the reactor of the present invention, the temperature difference between the vicinity of the outer wall and the central portion was small, whereas in the case of the conventional reactor, the temperature difference was small. Is very large. Also, the conversion of methanol is higher in the present invention than in the conventional type. In the simulation, r = kP ₁ / (1 + K ₁ P ₁ + K ₂ P ₂ ) ² was used as a reaction rate equation (Journal of the Petroleum Institute, Vol. 33, No. 3, page 173 (1990)). However, in the above equation, r is the reaction rate (mol / g-cat · time) methanol, k is the rate constant (mol / g-cat · time), P ₁ is partial partial pressure of methanol, P ₂ is the CO pressure, K ₁ is the adsorption equilibrium constant of methanol, K ₂ is the adsorption equilibrium constant of CO.

Embodiment 2 FIG. The aluminum plate substrate having a thickness of 0.1 mm was washed with 5% by weight of sodium hydroxide for 5 minutes, washed with water, then with 30% by weight of nitric acid, and further washed with water. The substrate pretreated as described above was treated with a 2.5% by weight chromic acid aqueous solution at a liquid temperature of 30 ° C. and a current density of 19.0 A.
/ M ² was carried out.

The obtained substrate having an anodized alumina surface was immersed in a solution containing 1.0 g / l of ultrafine platinum catalyst at pH 11.0 and 80 ° C. for 2 hours, and subjected to hot water treatment. The substrate is taken out and dried, then 5
It was calcined at 50 ° C. for 2 hours to obtain a catalyst.

The apparent surface area (apparent surface area of the metal substrate) of the obtained catalyst was 2.78 × 10 ⁻³ m ² / g,
The ET surface area was 20 m ² / g, and the amount of supported platinum was 0.56% by weight. The diameter of the platinum particles was 2-3 nm.

After 0.32 g of the obtained catalyst was pretreated at 400 ° C. for 1 hour in a hydrogen stream flowing at 40 cc / min, it was placed in a reactor in which nitrogen gas flowed at 50 ml / min, and 1 μl of methanol (〜2 (6 × 10 ⁻⁵ mol) to carry out a reforming reaction.

The reaction temperature is 300 ° C., 350 ° C. and 400 ° C.
Table 1 shows the results of the reforming at a temperature of ° C.

[Table 1]

Comparative Example 1 The pelletized alumina was impregnated with an aqueous solution of chloroplatinic acid having a predetermined concentration to support platinum, and had an apparent surface area of 1.27 × 10 ⁻³ m ² / g and a BET surface area of 25.
0 m ² / g: A granular catalyst having a platinum loading of 0.67% by weight was prepared. The results in Table 2 were obtained in exactly the same manner as in Example 1 except that 0.34 g of the above-mentioned granular catalyst was used instead of the plate-like catalyst used in Example 1.

[0038]

[Table 2]

Comparative Example 2 A granular catalyst obtained in the same manner as in Comparative Example 1 except that the amount of supported platinum was 6.27% by weight was 0.2%.
Except that 35 g was used, the results in Table 3 were obtained in the same manner as in Comparative Example 1.

[0040]

[Table 3]

The results of Example 2 and Comparative Examples 1 and 2 show that in the methanol reforming reaction of the present invention, more hydrogen and carbon monoxide are produced than before, and especially at about 400 ° C. Is extremely large.

[Brief description of the drawings]

FIG. 1 shows a reactor having a plate-shaped catalyst body in a fin shape (FIG. 1a).
FIG. 4 is an enlarged view of the fin portion (FIG. 5B).

FIG. 2 is a conceptual diagram of a conventional fixed-bed reactor (FIG. A).
FIG. 3 is a partially enlarged cross-sectional view (b diagram) of a catalyst-filled pipe.

FIG. 3 shows a reaction temperature of 40 when a plate-like catalyst is used.
FIG. 5 is a diagram showing changes in the temperature near the outer wall of the reactor and the center thereof and the conversion in the methanol reforming reaction at 0 ° C. with respect to the distance from the reactor inlet. In the figure, the dotted line shows the temperature near the outer wall of the reactor, the solid line below it shows the temperature at the center of the reactor, and the bottom solid line shows the conversion of methanol.

FIG. 4 shows the results of a methanol reforming reaction at a reaction temperature of 400 ° C. using a conventional fixed-bed reactor.
It is a figure which shows the change of the temperature of the outer wall of a reactor, and the center part with respect to the distance from a reactor inlet, and a conversion. In the figure, the dotted line shows the temperature near the outer wall of the reactor, the solid line below it shows the temperature at the center of the reactor, and the bottom solid line shows the conversion of methanol.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshimi Kawashima 1280 Kamiizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd. (56) References JP-A-2-68144 (JP, A) JP-A-2-143010 (JP, A) JP-A-2-144154 (JP, A) JP-A-49-36594 (JP, A) JP-A-63-16835 (JP, U)

Claims (2)

(57) [Claims] 1. A method for reforming methanol using a catalyst body, wherein a continuous catalyst body having an ultrafine methanol decomposition catalyst material supported on a surface of a continuous metal substrate having an anodized film is used as the catalyst body. And decomposition of methanol
A method for reforming methanol, which comprises conducting a reaction . 2. The method for reforming methanol according to claim 1, wherein the BET surface area of the catalyst body is 3000 times or more the apparent surface area of the metal substrate.