JP2851406B2 - Methanol reforming catalyst - Google Patents

Description

The present invention relates to a catalyst for methanol reforming, and more particularly, to a method for producing a gas containing hydrogen using methanol or a mixture of methanol and water as a raw material. Highly active, high selectivity, long life catalyst for methanol reforming.

[Conventional technology]

Due to the diversification of fuels, methanol that can be synthesized from fossil fuels other than crude oil has been receiving attention. In addition, since methanol is decomposed into a hydrogen-containing gas at a much lower temperature than naphtha, it has an advantage that waste heat can be used as a heat source for a methanol decomposition reaction and a steam reforming reaction.

The methanol decomposition reaction is as shown in the following equations (1) and (2).

CH ₃ OH → CO + 2H ₂ ΔH 25 ° C. = 21.7 kcal / mol (1) CH ₃ OH + nH ₂ O → (2 + n) H ₂ + (1-n) CO + nCO ₂ (2) where 0 <n <1 or The methanol steam reforming reaction is as shown in the following equation (3).

CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ ΔH25 ° C. = 11.8 kcal / mol …………………………………………………………………………………………………………………………………………………… (3)
Catalysts supporting base metal elements such as chromium and zinc and oxides thereof have been proposed, but these catalysts have poor low-temperature activity and have a large amount of by-products of dimethyl ether and methane. Leaving a point.

In addition to the above-described catalyst using a metal loading method, there is a preparation method using a precipitation method. A typical example of a catalyst prepared by this method is a methanol reforming catalyst containing zinc, chromium, and copper. . However, these catalysts have a problem that they have relatively high low-temperature activity but poor heat resistance.

[Problems to be solved by the invention]

Conventionally, when using the sensible heat of exhaust gas from engines, gas turbines, etc. as a heat source, and performing a decomposition or steam reforming reaction using methanol or a mixture of methanol and water as a raw material, the temperature of the exhaust gas is 200 to 700 ° C. as is well known. Because it changes to a degree, it can be reformed with a small amount of catalyst that can be mounted on an internal combustion engine over a wide temperature range, and even if it is kept at a high temperature of, for example, about 700 ° C., the reforming performance is stable and does not deteriorate A catalyst is required.

Conventional catalysts for reforming methanol have been proposed that are prepared by the metal loading method or precipitation method described above.However, these catalysts have poor low-temperature activity and are susceptible to thermal degradation at present. Many problems remain.

[Means for solving the problem]

In order to solve the above problems, the present inventors have previously prepared a catalyst comprising one or more oxides or hydroxides thereof of the group consisting of copper, zinc and chromium and oxides of nickel or hydroxides thereof. The headline has already proposed. (Japanese Patent Publication No. 62-4757
However, this catalyst has room for improvement in heat resistance, and as a result of intensive experiments and studies, it has been found that one or more oxides of the group consisting of copper, zinc, and chromium and an oxide of nickel contain zirconia. The present inventors have found that the catalyst contained in the composite oxide has high activity and extremely excellent selectivity with respect to the methanol reforming reaction of the catalyst, and has a long service life.

That is, the present invention is a methanol reforming catalyst characterized in that at least one oxide of the group consisting of copper, zinc, and chromium and an oxide of nickel are contained in a composite oxide containing zirconia.

[Action]

Here, the zirconia-containing composite oxide is alumina, titania, a composite oxide composed of one or more of the group consisting of silica and zirconia, and usually a mixed aqueous solution of a salt of each metal is hydrolyzed with aqueous ammonia. It is prepared by firing things, and the specific surface area is 0.1 to 500 m ² / g
Points to

To prepare the methanol reforming catalyst of the present invention, the hydroxide or carbonate of an alkali metal element or an alkaline earth metal element is directly used as a precipitant in an aqueous solution of a composite oxide containing the above metal compound and zirconia. Alternatively, a method in which an aqueous solution or aqueous ammonia is mixed to form a precipitate, followed by drying and baking is used.

The composition of the zirconia-containing composite oxide of the present invention is:
Al ₂ O ₃ / ZrO ₂ , TiO ₂ / Zr
O ₂ , SiO ₂ / ZrO ₂ in the range of 10/90 to 90/10 (hereinafter expressed by a molar ratio) is appropriate, and in combination with two kinds of Al ₂ O ₃ , TiO ₂ , SiO ₂ , Al ₂ O ₃・ TiO ₂ , Al ₂ O ₃・ SiO ₂ , TiO ₂・ SiO ₂
It is preferably in the range of the ratio at 10 / 90-90 / 10 with ZrO _2, also, Al
_{In combination} with three kinds of ₂ O ₃ , TiO ₂ and SiO ₂ , the ratio to ZrO ₂ is preferably in the range of 10/90 to 90/10.

The composition of the catalyst component of the present invention, copper, zinc, in combination with one or more oxides of the group consisting of chromium and nickel oxides, CuO / NiO, ZnO / NiO , with Cr ₂ O ₃ / NiO 10 / 90〜90 / 1
A range of 0 (hereinafter, represented by a molar ratio) is appropriate, and in particular, 20 /
A range from 80 to 60/40 is preferred. CuO, ZnO, in combination with a group of two or more composed of Cr ₂ O ₃ is, CuO · ZnO, CuO · Cr
₂ O ₃ , the ratio of ZnOCr ₂ O ₃ to NiO is preferably in the range of 10/90 to 90/10, and in combination with CuO, ZnO, Cr ₂ O ₃ , in combination with NiO The ratio is preferably in the range of 10/90 to 90/10.

The composition of the catalyst of the present invention is the same as that of the above catalyst component (CuO, ZnO, Cr ₂ O
Preferably in the range of 20 / 80-95 / 5 in ₃ of one or more a mixture of NiO) and the weight ratio of the composite oxide containing zirconia is preferably in the range particularly 30 / 70-80 / 20.

The methanol or a mixture of methanol and water referred to in the present invention has a molar ratio of H ₂ O / CH ₃ OH in the range of 0 to 100, and is used as a reaction condition for the methanol reforming reaction using the catalyst of the present invention. Preferably, the pressure ranges from 0 to 50 kg / cm ² and the temperature ranges from 150 to 600 ° C.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to examples.

Example 1 A 1 mol / molar aqueous solution of nickel nitrate 1 was mixed with 1 mol / mol of an aqueous solution of copper or zinc nitrate or 1 mol / mol of chromium nitrate and further contained a predetermined amount of zirconia having the composition shown in Table 1. The slurry containing the composite oxide to be added is added, and the precipitate of the hydroxide obtained by stirring and mixing for 30 minutes is reduced to 110
After drying at 300 ° C, it was calcined at 300 ° C for 3 hours to obtain catalyst 1 (NiO
CuO system), catalyst 2 (NiO / ZnO system), catalyst 3 (NiO / Cr ₂ O ₃₎
Was prepared.

Further, catalysts 4 having different compositions in the same manner as described above.
~ 6,9 (NiO / CuO system), catalyst 7 (NiO / ZnO system), catalyst 8
(NiO.Cr ₂ O ₃ system) was prepared.

After hydrogen reduction treatment of the above catalysts 1 to 9 at 200 ° C. to 350 ° C. for 12 hours, methanol (purity: 99%) or a mixture of methanol and water (H ₂ O / CH ₃ OH = 1.0 mol / mol) was added. An activity evaluation test was performed on the raw materials at normal pressure, LHSV (liquid hourly space velocity) of 5 h ^-1 and a reaction temperature of 300 ° C. Table 1 shows the results.

The composition of the generated gas (mol% -excluding unreacted methanol on a dry basis, the same applies hereinafter) was as follows.

(1) Methanol feed _{H 2: 64~67%, CO:} 31~33%, CO 2: 0.1~2%, CH 4: 0.02~2% (2) Methanol water mixture feed H _2: 66-71 %, CO: 14~33%, CO 2: 0.5~14%, CH 4: 0.01~1% Example 2 In the same manner as in Example 1, Catalysts 10 to 13 shown in Table 2 were prepared. After hydrogen reduction treatment of these catalysts at 350 ° C. for 12 hours, a mixture of methanol and water (H ₂ O / CH ₃ OH = 2.0 mol /
mol) as raw material, pressure 10 kg / cm ² G, LHSV5h ^-1 , reaction temperature 25
An activity evaluation test was performed at 0 to 350 ° C. Table 2 shows the results.

The composition of the generated gas at each temperature was as follows.

(1) Reaction _{Temperature: 250 ℃, 300 ℃ H 2} : 66~72%, CO: 13~33%, CO 2: 1~15%, CH 4: 0.01~0.1% (2) reaction temperature: 350 ° C. H _{2: 66~73%, CO: 8~33} %, CO 2: 1~19%, CH 4: 0.01~1% Furthermore, the catalyst the reaction conditions (reaction temperature 350 ° C.)
The result of a continuous test for 1000 hours was that the methanol conversion rate was
It was constant at 100%.

[Example 3] Except that in the powder preparation step of the catalyst 6 of Example 1, zirconia-containing composite oxides having various compositions shown in Table 3 were used instead of Al ₂ O ₃ / ZrO _2. In the same way, catalyst 14
-18 (NiO: CuO 70:30 molar ratio, content of the zirconia-containing composite oxide in the catalyst was 20% by weight).

The activity of these catalysts was evaluated after hydrogen reduction in the same manner as in Example 1. The results are shown in Table 3.

The composition of the generated gas was as follows.

(1) Methanol feed _{H 2: 63~67%, CO:} 30~32%, CO 2: 0.5~3%, CH 4: 0.1~3% (2) Methanol water mixture feed H _2: 64 to 71 %, CO: 14 to 32%, CO ₂ : 1 to 14%, CH ₄ : 0.05 to 2% [Effects of the Invention] As is clear from the results of Examples and Comparative Examples, the methanol reforming product of the present invention is The catalyst is a very excellent catalyst having high activity, high selectivity and long life at low temperature in a reaction for producing a hydrogen-containing gas from methanol or a mixture of methanol and water as a raw material.

Claims (1)

(57) [Claims] 1. A catalyst for methanol reforming, characterized in that a composite oxide containing zirconia contains at least one oxide of the group consisting of copper, zinc and chromium and an oxide of nickel.