JP2002177783A - Catalyst and method for manufacturing synthetic gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a synthetic gas while reaction at high temperature and carbon deposition are kept under control. SOLUTION: The production of the synthetic gas by partial oxidation of methane is carried out by filling a reaction tube with 60 mg catalyst containing 5 wt.% metal nickel in diamond oxide and reacting methane of 25 ml/minute flow velocity with oxygen of 5 ml/minute flow velocity at 550-700 deg.C. As a result, the synthetic gas of hydrogen and carbon monoxide is obtained as a product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing synthesis gas from lower saturated hydrocarbons such as methane, ethane and propane, and a catalyst used in the method. Hydrogen and carbon monoxide are not only raw materials for the chemical industry, but hydrogen is also important as a raw material for future fuel cells.

[0002]

2. Description of the Related Art Synthesis gas (mixed gas of carbon monoxide and hydrogen), which is an important raw material in the chemical industry, is produced by the reaction of light hydrocarbons such as methane, which is the main component of natural gas, with water vapor (1). Manufactured and usually aluminum oxide
The reaction is performed under the reaction conditions of 20 to 40 atm and 800 to 1000 ° C. using a nickel catalyst supported on (Al ₂ O ₃ ) or magnesium oxide (MgO) carrier. However, since the practical process is operated at a high temperature due to a large endothermic reaction, it is desired to develop a more efficient production method from the viewpoint of energy saving. CH ₄ + H ₂ O = CO + 3H ₂ ΔH ⁰ 298 = +206 kJ / mol (1)

[0003] In addition, in this reaction, the partial pressure ratio of methane and water is stoichiometrically 1. However, at this partial pressure ratio, carbon is deposited on the catalyst and the catalyst is easily deactivated. In, water is introduced 1.5 to 5 times with respect to methane to suppress carbon deposition. For this reason, even if the thermal energy of the produced gas is recovered, the energy consumption is still large and it is necessary to further improve the economic efficiency. The challenge in developing a catalyst for this reaction is to suppress carbon deposition rather than promote activity. Carbon deposition is an important problem that causes not only a decrease in catalyst activity but also clogging of the reactor and destruction of the physical structure of the catalyst.

Therefore, oxygen oxidation of methane (partial oxidation reaction)
Has recently been reexamined from the viewpoint of energy saving process. CH ₄ + (1/2) O ₂ → CO + 2H ₂ ΔH ⁰ 298 = -36 kJ / mol (2)

Ashcroft et al. Reported that using Ln ₂ Ru ₂ O ₇ (Ln = lanthanoid) as a catalyst, CO and H ₂ were obtained at a higher yield and higher selectivity than CH ₄ and O ₂ at 777 ° C. (AT Achcro
ft, AK Cheetham, JS Food, MLH Green, CP Gr
ey, AJ Murrel, PDF Vermon, Nature, 344 (1990)
319.).

Have performed a partial oxidation reaction of CH ₄ using a Ni / Al ₂ O ₃ catalyst and obtained CO 2 with a selectivity of 95% or more at 750 ° C. or more.
It has reported that it is possible to a obtain a H ₂ (D. Dissan
ayake, MP Rosynek, KCC Kharas, JH Lunsford,
J. Catal, 132 (1991) 117.). However, oxygen oxidation by these catalysts also requires a high temperature of 750 ° C. or more, and when nickel is used as a catalytically active species, carbon deposition is a problem as in steam reforming.

The present inventors have proposed iridium and several kinds of carriers for the purpose of developing a new catalyst in order to efficiently produce a synthesis gas at a lower temperature by an oxygen oxidation (partial oxidation) reaction of methane. A detailed study was conducted using the iridium / titanium oxide catalyst, and it was found that the iridium / titanium oxide catalyst exhibited a syngas generation activity comparable to a conventionally known catalyst and no carbon deposition was observed (K. Nakagawa, T. Suz
uki, T. Kobayashi and M. Haruta, Chem. Lett, (199
6) 1029). However, iridium used for this catalyst is an expensive rare precious metal, and there is a problem of cost as a practical process.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the reaction and carbon deposition at a high temperature, which are problems of the conventional synthesis gas production from methane, to stabilize the catalytic activity and extend the life. It is intended.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, as a carrier for nickel and some other metal catalysts, a diamond oxide which has not been conventionally used has been used. The use has led to overcoming the problem. Furthermore, when the catalyst of the present invention is used, not only can synthesis gas being a mixed gas of hydrogen and carbon monoxide be produced from methane as a raw material, but also synthesis gas can be produced from lower saturated hydrocarbons such as ethane and propane. . In either case, carbon dioxide is contained in the reaction product, but the carbon dioxide can be easily removed, so that the reaction product can be taken out as a synthesis gas.

The synthesis gas production catalyst of the present invention uses diamond oxide as a carrier, and carries on its surface any metal selected from the group consisting of nickel, rhodium, palladium, ruthenium, iridium and cobalt.

One aspect of the present invention for producing a hydrogen-containing mixed gas is to produce a synthesis gas from a lower saturated hydrocarbon and oxygen by a partial oxidation reaction in a temperature range of 550 to 700 ° C. in the presence of a catalyst. The catalyst used for this partial oxidation reaction is
It has diamond oxide as a carrier, and carries on its surface any metal selected from the group consisting of nickel, rhodium, palladium, ruthenium and iridium.

Another aspect of the present invention for producing a mixed gas containing hydrogen is to produce a synthesis gas by a steam reforming reaction from a lower saturated hydrocarbon and steam at a temperature in the range of 600 to 800 ° C. in the presence of a catalyst. . The catalyst used in the steam reforming reaction is a catalyst in which diamond oxide is used as a carrier, and a metal selected from the group consisting of nickel, rhodium, palladium, ruthenium, iridium and rhodium is supported on the surface thereof.

[0013] The catalyst used in the steam reforming reaction may not be subjected to the hydrogen reduction treatment. Of course, this does not exclude the application of the hydrogen reduction treatment. In the production method of the present invention, when methane is used as a lower saturated hydrocarbon, the resulting synthesis gas is a synthesis gas comprising hydrogen and carbon monoxide, which are important raw materials in the chemical industry.
When diamond whose surface is oxidized is used as a catalyst carrier, the interaction between the active metal species and the carrier is weakened, and the redox of the supported active species easily occurs. The present invention utilizes this property effectively.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The diamond used here is a fine grain diamond for industrial use and is commercially available, but its surface is not constant depending on the manufacturing process and has various structures. Oxidized diamond is prepared by air oxidation for 1 hour and used. When preparing a nickel catalyst supported on oxidized diamond, nickel nitrate 0.04
9-0.495 g dissolved in 20 mL of water was added to 1.99-1.90 g of oxidized diamond (particle size 0.5 micrometer or less),
After standing overnight with stirring, excess water was evaporated to dryness. The dried sample was placed on a magnetic boat, heated in an electric furnace at a rate of 10 ° C / min to 450 ° C under air circulation, and held at the same temperature for 3 hours to convert nitrate to nickel oxide. Was. This catalyst has a nickel metal weight of 0.5
Contains ~ 5%.

Other metal catalysts were prepared in the same manner using a water-soluble salt to prepare a catalyst supported on diamond oxide. 60 to 100 mg of the catalyst thus prepared was precisely weighed,
After filling into a quartz glass reaction tube having a length of 0 mm and a length of 250 mm, the reaction tube was set in a vertical electric furnace. The temperature of the catalyst layer was measured with a thermocouple inserted inside the reaction tube, and at the same time, the temperature of the electric furnace was controlled. Hydrocarbons and oxygen were introduced into the reaction tube through a mass flow control valve and reacted in the catalyst layer. The product at the outlet of the reaction tube was collected, analyzed for its components by gas chromatography, and quantified by a previously prepared calibration curve. In the reaction with steam, the introduction of hydrocarbons is as described above, but water is supplied to the syringe pump, water is supplied at a constant flow rate from the upper part of the reactor, and the water is heated by alumina balls filled in the upper part of the catalyst layer. Then, it was reacted with hydrocarbons in the catalyst layer as steam. The reaction product was collected after condensing water vapor with a water separator provided at the outlet, and analyzed by gas chromatography.

Example 1 Synthesis gas generation by partial oxidation of methane (reaction formula 2) was carried out. 60 mg of a catalyst containing 5 wt% of nickel metal in oxidized diamond was charged into the above reaction tube, and methane 25 was added.
The reaction was carried out at a flow rate of mL / min and oxygen of 5 mL / min, each set at a higher temperature from 400 ° C. to 50 ° C. After 2 hours from the start of the reaction, 4
The catalyst layer was kept at a constant temperature for 30 minutes at each of 00, 450, 500, 550, 600, 650, and 700 ° C., and the products were analyzed to determine the hydrogen and carbon monoxide yields. The results are shown in Table 1 as Experiment Nos. 1-4.
Shown in

[0017]

[Table 1]

It is apparent from the experimental numbers 2 to 4 in Table 1 that the temperature is 600 ° C.
From 700 to 700 ° C, the yield of hydrogen and carbon monoxide increased
At ℃, a hydrogen yield of 530 mmol / hr · g-catalyst and a carbon monoxide yield of 315 mmol / hr · g-catalyst were obtained, and no carbon deposition was observed. In order to examine the stability of the catalyst, data after 7 hours from the start of the reaction was measured. The results are shown in Table 1, Experiment No. 5. A value almost equal to that of Experiment No. 4 was obtained, and no apparent change in the color of the catalyst was observed, and no carbon deposition was observed.

(Example 2) The reaction temperature was 600 ° C under the same conditions as in Experiment No. 2 of Example 1 except that the amount of nickel metal supported on diamond oxide was changed to 0.5, 1, 3, and 5 wt%.
Table 2 shows the results of the reaction.

[0020]

[Table 2]

In Experiment No. 3, when the amount of nickel supported was 3 wt%, the largest hydrogen yield of 498 mmol / hr · g-catalyst and the yield of carbon monoxide of 183 mmol / hr · g-catalyst were obtained. Experiment number 1
Hydrogen yield at 0.5wt% nickel metal with low loading
358 mmol / hrg-catalyst, carbon monoxide yield 147 mmol / hr
High yields of g-catalyst were obtained.

Example 3 The catalyst carrier was diamond oxide, and the active metal species was nickel to rhodium (Rh).
Palladium (Pd), ruthenium (Ru), iridium (I
r), using a catalyst supporting 5 wt% of metal instead of iron (Fe), platinum (Pt), and cobalt (Co), to investigate synthesis gas generation by partial oxidation of methane in the same manner as in Example 2. Was. Table 3 shows the results.

[0023]

[Table 3]

The hydrogen and carbon monoxide yields in Example 2 which were the highest in nickel were shown.
Generation of hydrogen and carbon monoxide was observed in the order of 2, 3, and 4 rhodium, palladium, ruthenium, and iridium. However, hydrogen generation was not recognized in iron, platinum, and cobalt of Experiment Nos. 5, 6, and 7 in Table 3.

Example 4 Synthesis gas generation by steam reforming of methane (reaction formula 1) was carried out. 100 mg of a catalyst containing 5 wt% of nickel metal in diamond oxide was charged into the above reaction tube, and methane 5
The reaction was carried out at a flow rate of mL / min, a supply rate of steam of 15 mL / min, and a flow rate of argon at 25 mL / min, each set to a higher temperature from 600 ° C to 100 ° C. After 2 hours from the start of the reaction, the product is analyzed by keeping the catalyst layer at a constant temperature for 30 minutes at each of 600, 700, and 800 ° C,
The hydrogen and carbon monoxide yields were measured. Table 4 shows the results.

[0026]

[Table 4]

It is clear from Experiment Nos. 1-3 that the yield of hydrogen and carbon monoxide increases from 600 to 800 ° C., and at 800 ° C., the yield of hydrogen is 438 mmol / hr · g-catalyst, and the yield of carbon monoxide is 99.8 mmo.
l / hr · g-catalyst was obtained, and no carbon deposition was observed.

(Example 5) The catalyst carrier was diamond oxide, and the active metal species was changed from nickel to rhodium, iridium, platinum, palladium, ruthenium, and cobalt, and pretreatment was performed using a catalyst carrying 5 wt% of metal. Hydrogen reduction of catalyst usually performed by steam reforming is performed at 5 mL / mi of hydrogen.
After performing the reaction at 600 ° C. for 1 hour under a flow of n and 30 mL / min of argon, the synthesis gas generation by steam reforming of methane was examined in the same manner as in Experiment No. 1 of Example 4. Table 5 shows the results.

[0029]

[Table 5]

Nickel of Run No. 1 (no hydrogen reduction) (same as Run No. 1 of Example 4) showed the highest hydrogen and carbon monoxide yields, followed by Ruthenium, Cobalt of Run Nos. 3-8 Production of hydrogen and carbon monoxide was observed in the order of iridium, rhodium, palladium, and platinum. However, iron shows little catalytic activity. Experiment number 2
As for nickel, hydrogen yield is reduced by hydrogen reduction. This indicates that the use of diamond oxide as a carrier does not require hydrogen reduction as a catalyst pretreatment step.

(Comparative Example 1) Magnesium oxide (MgO) and aluminum oxide (A) which are generally used as nickel catalyst carriers instead of diamond oxide
l ₂ O ₃ ), titanium oxide (TiO ₂ ), lanthanum oxide (La
₂ O ₃ ), activated carbon, silicon oxide (SiO ₂ ) with nickel metal
Using a catalyst containing wt%, 60 mg of the catalyst was charged into the reaction tube, and the reaction temperature was 6 at a flow rate of methane of 25 mL / min and oxygen of 5 mL / min.
At 00 ° C, the synthesis gas generation by the partial oxidation reaction of methane was studied. Table 6 shows the results.

[0032]

[Table 6]

Magnesium oxides of Experiment Nos. 1, 2, and 3
Aluminum oxide, slightly hydrogen in titanium oxide,
Although generation of carbon monoxide was observed, a carrier having performance comparable to that of the diamond oxide of Experiment No. 2 of Example 1 could not be obtained. In addition, when aluminum oxide was used, remarkable carbon deposition occurred in the reaction for 10 hours, and the reaction tube was closed.

Comparative Example 2 Aluminum oxide, titanium oxide, magnesium oxide, silicon oxide, and lanthanum oxide, which are commonly used as a nickel catalyst carrier instead of diamond oxide, contain 5 wt% of nickel metal. Using a catalyst, 100 mg of the catalyst is filled in the reaction tube,
Hydrogen reduction of the catalyst usually performed by steam reforming as pretreatment is performed at 600 ° C under a flow of 5 mL / min of hydrogen and 30 mL / min of argon.
After the time, synthesis gas was produced by steam reforming of methane under the same reaction conditions as in Example 4 and Experiment No. 1. Table 7 shows the results.

[0035]

[Table 7]

Aluminum oxide, titanium oxide, magnesium oxide, silicon oxide of Experiment Nos. 1, 2, 3, 4, 5
In lanthanum oxide, generation of hydrogen and carbon monoxide was observed, but carbon deposition was also observed, and a carrier comparable to the diamond oxide of Example 4, Experiment No. 1 could not be obtained.

[0037]

According to the present invention, there is provided a catalyst in which nickel or another metal is supported on the surface of diamond oxide. By using this catalyst, a synthesis gas can be produced from a lower saturated hydrocarbon as a raw material. Further, the production method of the present invention is a method for producing a synthesis gas using the catalyst,
Nickel, rhodium, palladium, ruthenium and iridium on the surface of the diamond oxide in the presence of a catalyst supporting any metal selected from the group consisting of iridium and 550 ~ 700 ° C ...
Catalyst in which a metal selected from the group consisting of nickel, rhodium, palladium, ruthenium, iridium and rhodium is supported by a partial oxidation reaction from a lower saturated hydrocarbon and oxygen in the temperature range of A mixed gas containing hydrogen is produced from a lower saturated hydrocarbon and steam by a steam reforming reaction in a temperature range of 600 to 800 ° C. in the presence of hydrogen. This allows
The reaction at high temperature and carbon deposition can be suppressed, and the catalyst activity can be stabilized and the life can be extended.

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Claims (7)

[Claims] 1. A synthesis gas production catalyst comprising diamond oxide as a carrier and nickel supported on the surface thereof. 2. A synthesis gas production catalyst comprising: diamond oxide as a carrier; and a metal selected from the group consisting of rhodium, palladium, ruthenium and iridium supported on the surface thereof. 3. A synthesis gas production catalyst comprising diamond oxide as a carrier and cobalt supported on the surface thereof. 4. Use of the catalyst according to claim 1 or 2
A method for producing a synthesis gas from a lower saturated hydrocarbon and oxygen in a temperature range of 0 to 700 ° C. 5. A method for producing a synthesis gas from a lower saturated hydrocarbon and steam at a temperature in the range of 600 to 800 ° C. using the catalyst according to claim 1, 2, or 3. 6. The method according to claim 5, wherein the catalyst is used without being subjected to a hydrogen reduction treatment. 7. The lower saturated hydrocarbon is methane,
7. The method according to claim 4, wherein the synthesis gas is a mixed gas of hydrogen and carbon monoxide.