JP3225078B2 - Catalyst for syngas production - 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 used in a catalytic reaction for producing methane by reacting methane with carbon dioxide.

[0002] The emission of carbon dioxide from the burning of fossil fuels is expected to be a major cause of global warming and a threat to human survival. For this reason, if carbon dioxide generated by combustion can be separated and recovered and used effectively, carbon dioxide emission will be reduced or suppressed, and establishment of a utilization technique for that purpose is strongly desired. The present invention provides a carbon dioxide utilization technology for that purpose.

[0003]

2. Description of the Related Art Methane is a major component of natural gas and is an abundant hydrocarbon resource on the earth. The main use of methane is fuel, but in addition, synthesis gas (carbon monoxide +
Hydrogen), methanol and FT as C ₁ chemical raw materials
Synthetic oils and oxo alcohols are produced.

[0004] As a method for producing synthesis gas from methane, a steam reforming method using steam as a gasifying agent has become mainstream.

CH ₄ + H ₂ O = CO + 3H ₂ (1) On the other hand, for effective use of carbon dioxide, a so-called carbon dioxide gas reforming method using carbon dioxide as a gasifying agent has been studied.

CH ₄ + CO ₂ = 2CO + 2H ₂ (2) For example, Ashcroft et al. Equimolarly convert methane and CO ₂ to a catalyst in which Ni ₂ is supported on Al ₂ O ₃ (manufactured by British Gas, CRG'F 'steam reforming catalyst). At normal pressure, 777 ° C, W / F (= catalyst weight / raw material flow rate) 0.0
Reaction at 05 g / (Ncc / min), methane conversion 88%
To obtain synthesis gas. However, it states that carbon was deposited on the catalyst and the catalytic activity was reduced. Also, R instead of Ni
It was stated that when a catalyst supporting 1% of a noble metal such as h or Ir was used, the methane conversion was almost the same and no carbon was deposited (Nature Vol. 352, 18 July 1991, 225-226).
page).

[0007] Gustafson & Walden reported that P
methane and CO ₂ at a molar ratio of 0.9: 1.0, 1 atm, 850 ° C., on a catalyst supporting 1% of t or 0.5% of Pd.
W / F 0.007 g / (Ncc / min) to react 96
% Or more of methane conversion (US-5,068,
057).

[0008] When reforming methane with carbon dioxide using a catalyst supporting a noble metal as described above,
Achieving high conversion requires a high temperature of 800 ° C. or higher. On the other hand, Uchijima et al. Supplied a equimolar amount of methane and CO ₂ to a catalyst having a large amount of Ru and Rh supported on silica at 5%,
From the test results obtained by reacting while changing the temperature at 0.0056 g / (Ncc / min) of W / F, about 94% and about 74% of methane conversion were obtained at 700 ° C. (Catalyst Vol. 33, No.
2, pp. 99-102, FIG. 5).

When the amount of supported catalyst is increased, the conversion can be improved even at a relatively low temperature of about 700 ° C., but the activity is still not sufficient.

[0010]

Reducing the reaction temperature makes it possible to reduce the heat resistance required of the reactor material, and also to increase the externally applied heat flux through the walls of the reactor. Since there is an extremely great benefit as a practical device, such as the miniaturization of the catalyst, it has been desired to develop a catalyst that is highly active at low temperatures.

[0011]

The inventor of the present invention has studied a catalyst which suppresses carbon deposition as much as possible, has high activity at a low temperature, and requires a small amount of a noble metal component carried thereon. Composite catalyst supporting a small amount of platinum group metal reacts with methane and carbon dioxide 6
The present invention has been found to exhibit extremely high activity in a low temperature range of about 00 ° C. and to have no carbon deposition.

That is, the present invention provides a silica-alumina
To a carrier coated with 15 wt% alumina on ivever ,
0 wt% platinum, 10 wt% nickel, 5.6 wt%
This is a synthesis gas production catalyst for synthesizing hydrogen and carbon monoxide by reacting methane with CeO ₂ and carbon dioxide.

Examples of the rare earth metal oxide in the present invention include oxides of metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), and samarium (Sm). . Of these, lanthanum and cerium oxides are particularly desirable.

The platinum group metals in the present invention include platinum (Pt), palladium (Pd), iridium (Ir),
Osmium (Os) is preferred. Ruthenium (Ru),
Rhodium (Rh) can be used, but the methanation activity is strong and the conditions of use are limited.

As the carrier in the present invention, alumina (A
l ₂ O ₃ ) are suitable. Silica (SiO ₂ ) has low heat resistance and is not suitable for practical use.

As a preferable composition range of each component constituting the catalyst of the present invention, the molar ratio of nickel to the rare earth oxide is preferably in the range of 1/10 to 1/3, and particularly preferably 1/5. . The molar ratio of the platinum group metal to the rare earth oxide is preferably in the range of 1/50 to 1/10,
Particularly preferably, it is in the range of 1/30 to 1/10. Further, the weight ratio of the total of nickel, platinum group metal and rare earth oxide to the carrier is suitably from 1/100 to 1/3.

The concentration ratio of carbon dioxide to methane in the raw material is often determined by the fact that, in the case of a conventional catalyst, a phenomenon in which carbon precipitates on the surface of the catalyst during the reaction and the catalytic activity is reduced is often observed. Has been determined to be appropriate, but there is no particular limitation when using the catalyst of the present invention.

Although the synthesis conditions of the present invention can be used under the reaction conditions of conventional catalysts, milder conditions can also be selected.

That is, the reaction temperature is 400 to 1000 ° C.
Is preferable. If the temperature is lower than 400 ° C., smooth progress of the reaction may not be ensured, and if it exceeds 1000 ° C., the catalyst is liable to be deteriorated.

The reaction can be carried out under reduced pressure, normal pressure or increased pressure. Particularly in the present invention, the reaction pressure is preferably in the range of 1 to 100 atm.

The contact time of methane and carbon dioxide (or a diluent gas when a diluent gas is used) to the entire raw material gas is usually 0.0001 to 1.
0 g / (Ncc / min).

[0022]

Example 1 (Preparation of catalyst) Disc-shaped fiber flux having a diameter of 8 mm (heat-resistant silica-alumina fiber manufactured by Carborundum, thickness 1)
mm) was immersed in an aqueous solution of aluminum nitrate, contacted with ammonia gas to gel, and further heated and denitrated to form an alumina layer on the surface of the fiber flux, which was used as a carrier. The generated Al ₂ O ₃ was 15% by weight based on the fiber flux. Next, the carrier was immersed in an aqueous chloroplatinic acid solution and dried. Next, it was immersed in a mixed aqueous solution of nickel nitrate and cerium nitrate and dried. As a result of the analysis, the loading amount of each component as Pt, Ni and CeO ₂ was 1. It was 0 % by weight, 10.0% by weight, and 5.6% by weight. That is, Pt / CeO ₂
Is 1/30, and the molar ratio of Ni / CeO ₂ is 1/5.
Met.

(Pretreatment of Catalyst) The above-mentioned three catalysts were charged into a quartz flow-through reactor having an inner diameter of 8 mm, and heated at 400 ° C. to flow hydrogen for 30 minutes to reduce (the weight after the reduction was 7%).
2 mg. The Pt carrying amount is 0.98 mg).

(Reaction test) Methane (10 vol%) and carbon dioxide (120 vol) were charged into the reactor filled with the catalyst.
%) And nitrogen (80 vol%) at a rate of 25 Ncc /
The reaction mixture was separated and reacted at a reaction temperature of 350 to 700 ° C. at normal pressure. The space velocity was 10,000 h ^-1 . Also, no precipitation of carbon on the catalyst was observed. Table 1 shows the results of the reaction test.

Comparative Example 1 Example 1 was repeated except that the operation of supporting Ni and CeO ₂ was not performed, and that a honeycomb (made of cordierite, an outer diameter of 8 mm) was used instead of the fiber flux.
A reaction test was carried out using a catalyst prepared by the same method as above and supporting only 1.0% of Pt (14.7 mg as a supported amount of Pt). The reactor and reaction conditions were the same as in Example 1. Also, no precipitation of carbon on the catalyst was observed. Table 2 shows the results of the reaction test.

[0026]

[Table 1]

[0027]

[Table 2] The production rates of CO and hydrogen are values obtained by converting the respective production amounts based on the reaction formula (2) when methane reacts 100%.

[0028]

According to the syngas production method of the present invention, 700
At 90 ° C. a conversion of more than 90% is achieved and the reaction temperature is 100
° C or more. When the required amount of the catalyst and the required amount of the expensive platinum group metal were compared between Example 1 and Comparative Example 1, the amount of Pt supported on the catalyst was reduced to 1/15. It can be seen that the activity is significantly improved as compared with the catalyst.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 23/89 C01B 3/40

Claims (1)

(57) [Claims] (1) 15 wt% silica / alumina fiber
% Alumina on a carrier coated with 1.0% by weight of platinum,
A synthesis gas production catalyst for synthesizing hydrogen and carbon monoxide by reacting methane and carbon dioxide supporting 10 wt% of nickel and 5.6 wt% of CeO ₂ .