JP2003192301A - Method for producing hydrogen from lower hydrocarbons - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for decomposing hydrocarbons capable of producing hydrogen efficiently in a relatively short period of time using a highly active catalyst. <P>SOLUTION: This method for producing hydrogen by a decomposition reaction of a lower hydrocarbon comprises bringing a 1-4C lower hydrocarbon-containing gas into contact with an H-β type zeolite or H-ZSM-5 type zeolite catalyst at 400 to 800°C. AS a raw material lower hydrocarbon-containing gas, it is preferable to use methane or a mixed gas of methane and an inert gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing hydrogen by a decomposition reaction of hydrocarbons.

[0002]

2. Description of the Related Art Hydrogen is widely used as a raw material for the production of chemical substances widely used in the chemical industry.
With the increasing environmental problems in recent years, it has become important as a clean energy source. Conventionally,
Known methods for producing hydrogen from hydrocarbons include steam reforming of hydrocarbons and partial oxidation of the hydrocarbons with air. However, these methods produce a large amount of carbon dioxide that causes global warming. There is a problem of living.

Recently, as another method of producing hydrogen from hydrocarbons, a method of producing hydrogen and solid carbon by a decomposition reaction of methane or the like has been investigated. This method is a method for producing hydrogen, which attracts attention because it does not generate carbon dioxide, and in this decomposition reaction, a nickel catalyst supported on a metal oxide is mainly used. Among them, silica (Cab-O-
Sil) -supported catalysts have been reported to have high activity and long life [Chemistry Letters, 1179-1180 (1999)].
However, this method has problems that it takes a long time to generate hydrogen, carbon by-produced by decomposition of methane accumulates on the catalyst, and eventually the catalytic activity decreases.

[0004]

The present invention has been made based on the above-mentioned actual situation in the prior art. That is, it is an object of the present invention to provide a hydrocarbon decomposition method capable of efficiently producing hydrogen in a relatively short time using a highly active catalyst.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on a method for producing hydrogen by decomposing hydrocarbons, and as a result, when a catalyst in which nickel is supported on a specific carrier is used, the decomposition of hydrocarbons is Found that hydrogen is obtained in high yield while being promoted, the catalytic activity is retained for a long time,
The present invention has been completed. That is, according to the present invention, a lower hydrocarbon-containing gas having 1 to 4 carbon atoms is supported on nickel by an H-beta type zeolite catalyst or by a nickel supported H-ZSM-5 type zeolite catalyst and 400- There is provided a method for producing hydrogen, which comprises contacting at 800 ° C. to obtain hydrogen by a decomposition reaction of a lower hydrocarbon. At that time, it is preferable to use methane or a mixed gas of methane and an inert gas as the lower hydrocarbon-containing gas having 1 to 4 carbon atoms as a raw material.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a lower hydrocarbon is brought into contact with a catalyst having nickel supported as an active component on a catalyst carrier under heating conditions to decompose it into hydrogen and carbon.
In the present invention, zeolite which is an aluminosilicate is used as the catalyst carrier. Generally, zeolite has
Various types of zeolites such as type, X type, Y type, etc. are known, but in the present invention, ZSM-5 type zeolite represented by MFI in the structural code established by the International Zeolite Association or beta also represented by ^* BEA. Type zeolite, which may contain Na or the like as an exchangeable cation, is used after being exchanged into a proton type (H type). The silica / alumina ratio of this zeolite is
Although not particularly limited, a preferable range is from 20 to 200.

The nickel compound used as a nickel precursor to be supported on the above zeolite carrier as a catalytically active component is not particularly limited, but readily available water-soluble nitrates, acetates, chlorides, It is preferable to use sulfate or the like, and nitrate is more preferable. As a method for supporting nickel, any conventionally known method can be used, and, for example, an impregnation method, a precipitation method, an ion exchange method or the like is used. Among them, the impregnation method is preferable. The amount of nickel supported on the catalyst carrier is not particularly limited as long as the desired catalyst activity can be obtained.
A range of 3 to 15 mmol of nickel atom is preferable with respect to g.

Next, it is desirable that the zeolite carrier carrying the nickel compound is heated and calcined in an oxygen-containing gas such as air or oxygen. The firing temperature is usually in the range of 300 to 900 ° C, preferably 500 to 800 ° C. The heating time is usually 10 minutes to 24 hours, preferably 1 to 10 hours.
It's time.

The reaction raw material used in the present invention is a lower hydrocarbon-containing gas having 1 to 4 carbon atoms and having 1 to 4 carbon atoms.
It is a single gas or a mixed gas of two or more kinds of lower hydrocarbons having one or a mixed gas of these lower hydrocarbons and an inert gas. Examples of the lower hydrocarbon include methane, ethane, ethylene, propane, propylene, normal butane, isobutane, 1-butene, 2-butene, isobutene, butadiene and the like, and these may be used alone or in combination of two or more thereof. The one used is preferably methane. In addition, examples of the inert gas include helium, argon, neon, nitrogen, and the like, and these are used alone or in combination of two or more thereof. Further, the above raw materials may contain 5% or less of water vapor, oxygen, air and the like.

Any conventionally known catalytic reaction system can be employed to carry out the reaction of the present invention. Specifically, a flow system, a batch system, a fixed bed, a fluidized bed, etc. can be used alone or appropriately. It can be performed in combination. In addition, it is desirable that the catalyst be brought into contact with hydrogen or a mixed gas of hydrogen and an inert gas in advance before the reaction is started to perform the reduction activation treatment. The treatment is preferably performed at a temperature of 400 to 800 ° C. for 10 minutes to 10 hours.

In the reaction in which lower hydrocarbons are decomposed in the presence of a catalyst to produce hydrogen, carbon gradually accumulates on the surface of the catalyst, so that it is necessary to pay sufficient attention to the accompanying clogging of the reactor. In the present invention, the temperature for carrying out the decomposition reaction is
It is necessary to be in the range of 400 to 800 ° C. 40
If the temperature is lower than 0 ° C, a sufficient conversion cannot be achieved.
If the temperature exceeds 0 ° C., carbon is more likely to be deposited on the catalyst, which causes a problem such as deactivation of the catalyst when a sufficient amount of hydrogen cannot be obtained. In this decomposition reaction, the catalyst activity decreases after 6 to 10 hours and the reaction hardly progresses. Therefore, in order to continuously obtain hydrogen for a long time, a plurality of catalyst layers are arranged and these are appropriately switched. Therefore, it is desirable to use an apparatus provided with a system capable of always supplying the raw material gas to the active catalyst, or an apparatus which continuously supplies the active catalyst by applying a fluidized bed or the like. The catalyst whose activity has been reduced after use in this reaction can be reused because it is regenerated by removing carbonaceous substances when heat-treated in air or an oxygen-containing gas.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 (Preparation of catalyst) 0.1 g of H-beta type zeolite carrier having a silica-alumina ratio of 25 or 150 H-beta type zeolite carrier having a silica-alumina ratio of 25 was placed in a ceramic reaction dish (diameter 2 cm, depth 5 mm). In it, nickel nitrate solution (2mo
(1/1) 0.25 ml was added dropwise, and the mixture was thoroughly mixed with the carrier using a glass rod and then dried at 100 ° C. Then, the catalyst was obtained by performing heating and calcination in air at 750 ° C. for 5 hours. The nickel supporting rate of this catalyst was 5 mmol per 1 g of the carrier. (Reaction operation) Quartz cup (inner diameter 5.5 mm, outer diameter 7.0 m
m, height 11.0 mm) was filled with about 4 mg of the catalyst and placed in a ceramic boat with both ends open. The boat on which the cup was placed was placed in a quartz reaction tube (outer diameter 28 mm, inner diameter 24 mm) having both ends opened, and a reactor of a system of heating in a tubular electric furnace was prepared. After that, the catalyst is flown at a flow rate of 50.
The catalyst was subjected to reductive activation treatment by bringing it into contact with a mixed gas of hydrogen (10 vol%) and argon (90 vol%) at 600 ml for 1 hour. The inside of the reactor is heated to 500 ° C, and a mixed gas of methane (10 vol%) and helium (90 vol%) is caused to flow from one opening at a flow rate of 150 ml / min for 30 minutes to progress the decomposition reaction of methane. Let After the reaction,
The supply of methane gas was stopped, and it was cooled to 100 ° C. or lower while flowing only helium. Then, the catalyst in the cup was taken out, and the weights of carbon and catalyst were precisely measured using a thermogravimetric analyzer. From the carbon weight obtained in this measurement, the amount of hydrogen produced was calculated and the average hydrogen production rate for 30 minutes from the start of the reaction was calculated. As a result, silica /
A catalyst using an H-beta zeolite carrier with an alumina ratio of 25 has a hydrogen generation rate of 11.68 mmol / catalyst.
It was a minute. On the other hand, with a catalyst using a H-beta zeolite carrier with a silica / alumina ratio of 150, 13.05 mmo
It was lg / catalyst · minute.

Example 2 The catalyst carrier used in Example 1 was used with a silica / alumina ratio of 90.
The reaction was performed in the same manner as in Example 1 except that the H-ZSM-5 was replaced with H-ZSM-5, and the resulting catalyst was subjected to activity measurement to calculate the average hydrogen generation rate. As a result, the average initial reaction rate within 30 minutes from the start of the reaction was 14.56 mmolg /
It was a catalyst / minute.

Comparative Example 1 The catalyst carrier used in Example 1 was used in a silica / alumina ratio of 36.
USY carrier of 0 (FAU structure) or silica / alumina ratio of 2
The reaction was carried out in the same manner as in Example 1 except that H-mordenite (having a MOR structure) of 0 was used, and the resulting catalyst was subjected to activity measurement to calculate the average hydrogen generation rate. As a result, the average initial reaction rate within 30 minutes from the start of the reaction was 8.48 mmo in the former case (using USY).
It was lg / catalyst-minute, and the latter (using H-mordenite) was 7.86 mmolg / catalyst-minute.

Comparative Example 2 Ni / Si was used as a catalyst for the decomposition reaction of methane.
O ₂ , Ni / TiO ₂ or Ni / graphite [Appl
In a conventional experiment carried out using ied Catalysis Vol.217.p101-110 (2001)], the conversion of methane was only 6-7% even at the maximum activity at 500 ° C (see Fig. 1). In addition, the reaction rate is not maintained for a long time and is rapidly decreasing, and the hydrogen production rate is about 7.3 to 8.5 mmol / catalyst · minute even if the hydrogen production rate is calculated under the condition of showing the maximum value.

Example 3 The decomposition reaction of methane using the catalysts shown in Examples 1 and 2 was continued for 4 hours, and the total amount of hydrogen produced during that period was determined. H-ZSM-5 was used as a carrier. 1 for catalyst
The amount of hydrogen per gram is 1.91 mol, and the amount of hydrogen per gram is 1.95 mol for the catalyst using the H-beta zeolite carrier with a silica / alumina ratio of 25.
The amount of hydrogen per gram of the catalyst using the H-beta zeolite carrier with an alumina ratio of 150 was 2.06 mol.
The average hydrogen production rate for 4 hours was H-ZS.
The catalyst using M-5 as a carrier has a concentration of 7.96 mmol / catalyst / min, and the catalyst using the H-beta zeolite carrier having a silica / alumina ratio of 25 has a value of 8.13 mmol / catalyst / min and a silica / alumina ratio of 150. The catalyst using the H-beta zeolite carrier of No. 8 was 8.58 mmol / catalyst · min. These values are almost the same as those shown in Comparative Example 2, but the activity of Comparative Example 2 is the initial maximum value at the initial stage, and decreases to 3 to 4.5% after 4 hours. This means that the catalyst of which the average value for 4 hours is almost equal to the instantaneous maximum value of Comparative Example 2 is extremely excellent.

Comparative Example 3 Using the catalyst of the catalyst carrier shown in Comparative Example 1, the reaction was carried out for 4 hours in the same manner as in Example 3 to find the total amount of produced hydrogen. USY (FAU) having a silica / alumina ratio of 360 was obtained. In the case of a catalyst having a structure) as a carrier, the amount of hydrogen produced per 1 g of the catalyst is 1.68 mol, and the silica / alumina ratio 20
In the catalyst using mordenite (MOR structure) as a carrier, the amount of produced hydrogen was 1.01 mol per 1 g of the catalyst. From the comparison between each of the above-mentioned Examples and each of the Comparative Examples, it was revealed that the catalysts shown in the Examples are excellent in the decomposition reaction of methane.

[0018]

According to the present invention, since a specific zeolite is used as a catalyst carrier in a hydrocarbon decomposition reaction, the catalytic activity is improved, the reaction rate is accelerated, and the deactivation of the catalyst is reduced. It is possible to efficiently produce hydrogen.

[Brief description of drawings]

FIG. 1 is a graph showing the results of a conventional experiment in which a decomposition reaction of methane at 500 ° C. was performed using nickel catalysts supported on different carriers.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Takahara             1-1-1 Higashi 1-1-1 Tsukuba City, Ibaraki Prefecture             Inside the Tsukuba Center, National Institute of Advanced Industrial Science and Technology (72) Inventor Masahiro Saito             1-1-1 Higashi 1-1-1 Tsukuba City, Ibaraki Prefecture             Inside the Tsukuba Center, National Institute of Advanced Industrial Science and Technology F-term (reference) 4G040 DA03 DC01                 4G069 AA03 BA07A BA07B BB02A                       BB02B BC68A BC68B CC17                       ZA11A ZA11B ZA19A ZA19B                       ZF05A ZF05B

Claims (2)

[Claims] 1. A H-beta type zeolite or H-ZSM-5 type zeolite catalyst supporting nickel with a lower hydrocarbon-containing gas having 1 to 4 carbon atoms and 400 to 800 ° C.
A method for producing hydrogen, characterized in that the hydrogen is obtained by the decomposition reaction of lower hydrocarbons by contacting with each other. 2. The method for producing hydrogen according to claim 1, wherein the lower hydrocarbon-containing gas is methane or a mixed gas of methane and an inert gas.