JPH08294627A - Catalyst for synthesizing methanol and its preparation - Google Patents

Abstract

PURPOSE: To prepare a silver-based catalyst for synthesizing methanol of high activity and high selectivity. CONSTITUTION: To prepare a silver-based catalyst for synthesizing methanol by using at least one kind of metallic oxide selected out of ceria (CeO2 ), zirconia (ZrO2 ), and a double oxide containing at least either Ce or Zr as a carrier, and causing the metallic oxide carrier to carry silver.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver catalyst for methanol synthesis for synthesizing methanol from synthesis gas and a method for producing the same.

[0002]

2. Description of the Related Art A technique for producing methanol by catalytic conversion of a mixed gas (synthesis gas) of hydrogen and carbon monoxide has been known for a long time. As a catalyst in this reaction, a catalyst in which copper is supported on zinc oxide is typical, but various catalysts such as those to which chromium oxide, aluminum oxide and the like are added and further palladium catalysts have been proposed. ing.

For example, JP-A-58-79939 discloses a catalyst in which rhodium, silver, zirconium and molybdenum are supported on a carrier such as silica or alumina, and JP-A-60-1.
Japanese Patent No. 90232 discloses an oxide catalyst containing copper, zinc and aluminum, and Japanese Patent Application Laid-Open No. 4-122450 discloses five types of oxide catalysts: copper oxide, zinc oxide, chromium oxide, aluminum oxide, and aluminum oxide impregnated with silver oxide. Each is described as a catalyst consisting of a mixture, but for synthesizing a gas rich in methanol from hydrogen and carbon dioxide.

[0004]

An object of the present invention is to provide a new silver-based catalyst as a catalyst for methanol synthesis. That is, as for the catalyst for synthesizing methanol containing silver, there are few reports as a catalyst for synthesizing methanol from hydrogen and carbon monoxide, and the conventional silver-based catalyst has a problem that the activity and the selectivity are low. .

[0005]

The inventors of the present invention have conducted various experiments and researches to solve the above problems, and as a result, have used a specific type of metal oxide as a carrier and supporting silver thereon. It was found that high activity and selectivity can be obtained in the case of being allowed to complete the present invention. Less than,
The invention according to each claim will be specifically described.

(Invention of Claim 1) The present invention uses, as a carrier, one or more metal oxides selected from the group consisting of ceria, zirconia, and multiple oxides containing at least one metal of Ce and Zr. A catalyst for methanol synthesis characterized in that silver is supported on this metal oxide-based carrier.

The catalyst provides relatively high activity (carbon monoxide conversion) and selectivity (methanol yield). Although the reason is not clear, it is conceivable that the silver as a catalyst metal interacts with the oxide of Ce or Zr as a carrier to make the silver finer or to carry it in a highly dispersed state.

(Invention of Claim 2) The present invention is a method for producing the catalyst for synthesizing methanol according to claim 1, which comprises a metal compound for forming the metal oxide-based carrier. A raw material solution prepared by dissolving a silver compound in a solvent is prepared, and the raw material solution and an alkaline solution are mixed to precipitate the metal as a hydroxide or the like which is a precursor of the metal oxide-based carrier. At the same time, the silver is co-precipitated on the precursor of the metal oxide-based carrier.

The present invention employs a so-called coprecipitation method for preparing the above-mentioned catalyst for synthesizing methanol. In this method, the dispersibility of silver in the above-mentioned metal oxide type carrier is increased and the activity is improved. Be advantageous

That is, since silver is also co-precipitated as hydroxide or the like at the same time when the precursor of the metal oxide-based carrier is precipitated as hydroxide or the like, the metal oxide-based carrier and silver are closely packed. And silver is highly dispersed and supported on the metal oxide-based carrier. Therefore, a relatively large amount of silver can be supported on the metal oxide-based carrier.

Here, as the metal compound constituting the above-mentioned metal oxide type carrier, electrolytes such as acetates, nitrates and sulfates, especially water-soluble ones are preferable, and silver compounds are also the same. Examples of the precipitation reagent include NaOH, NH ₄ OH, N
a ₂ CO _{3 and the} like, and the pH of the raw material solution
Will be adjusted. The obtained coprecipitate may be washed, dried, and fired at a temperature of about 300 to 600 ° C. In use, for example, by solidifying the catalyst powder and crushing it, Particles of appropriate size may be prepared and packed in a column.

(Invention of Claim 3) The present invention relates to a method for producing the catalyst for methanol synthesis described in claim 1, wherein the metal oxide-based carrier is impregnated with a solution of a silver compound. Characterized in that silver is deposited on the metal oxide-based carrier by evaporating the solvent of the silver compound solution.

That is, the present invention employs the impregnation method for producing the above catalyst. According to various experiments and the like, in general, in the case of the impregnation method, even if the supported amount of the catalyst metal is increased, the catalyst metal is lumped and supported on a portion of the carrier surface where the catalyst metal is easily attached, and thus the dispersibility is high. Therefore, the knowledge that the specific surface area of the catalyst is greatly reduced was obtained, and the invention according to claim 2 was conceived. However, this is not always the case in the case of a combination of a metal oxide as a support and silver as a catalyst metal, especially when the support is zirconia, the impregnation method rather improves the activity and selectivity of the catalyst. Therefore, the present invention has been completed and the present invention has been completed.

[0014]

According to the invention of claim 1, ceria,
Since one or more metal oxides selected from zirconia and multiple oxides containing at least one metal of Ce and Zr are used as a carrier and silver is supported on the metal oxide-based carrier, high activity is obtained. And high selectivity is obtained.

According to the invention of claim 2, a raw material solution is prepared by dissolving a metal compound for forming the metal oxide-based carrier and a silver compound in a solvent, and the raw material solution and an alkaline solution are prepared. By precipitating the metal as a hydroxide or the like which is a precursor of the metal oxide-based carrier, the silver is co-precipitated on the precursor of the metal oxide-based carrier by mixing , Silver can be supported on a metal oxide-based carrier in a highly dispersed manner, which is advantageous in obtaining the catalyst for methanol synthesis with high activity and high selectivity described in claim 1.

According to the third aspect of the invention, the metal oxide carrier is impregnated with the solution of the silver compound, and then the solvent of the silver compound solution is evaporated to deposit silver on the metal oxide carrier. Since it is made to precipitate, a catalyst with high activity and high selectivity can be obtained.

[0017]

Embodiments of the present invention will be described below.

[0018] <Preparation of Catalyst> - Example 1; Ag / ZrO ₂ catalyst - silver nitrate (Kishida Chemical Co., Ltd. AgNO ₃₎ and zirconium nitrate _{ZrO (NO 3) 2 · 6H} 2 O and were weighed predetermined amounts, which Was dissolved in distilled water to prepare a solution A. On the other hand, an aqueous solution of sodium carbonate was prepared as a neutralizing solution (precipitation reagent), and this was designated as solution B.

Then, while stirring the solution A, the solution B
A coprecipitate was formed by dropping the liquid. A similar coprecipitate can be obtained by pouring the solution A into the diluted solution B. The coprecipitate thus obtained was stirred for 1 hour, washed thoroughly with water and dried,
Firing was performed at 00 ° C. for 5 hours.

The obtained Ag / ZrO ₂ catalyst is one in which silver is supported in high dispersion on zirconia (ZrO ₂ ),
The atomic ratio Ag / Zr of silver and zirconium is 1/19.
Is.

[0021] - Example _2; Ag / CeO 2 catalyst - the silver nitrate and cerium nitrate _{Ce (NO 3) 3 · 6H} 2 O
In the same manner as in Example 1, ceria (CeO ₂ ) was loaded with silver by weighing each of a predetermined amount and dissolving them in distilled water to obtain a liquid A and using an aqueous solution of sodium hydroxide as a liquid B. An Ag / CeO ₂ catalyst was obtained. The atomic ratio Ag / Ce of silver and cerium is 1/19.

[0022] - Comparative Example 1; Ag / ZnO catalyst - those between the silver nitrate and zinc nitrate _{Zn (NO 3) 2 · 6H} 2 O was dissolved in distilled water as the A solution, zinc oxide by the same method as in Example 1 Ag / ZnO in which silver is supported
A ZnO catalyst was obtained. The atomic ratio Ag / Zn of silver and zinc is 1 /
It is 19.

[0023] - Comparative Example _2; Ag / Al 2 O ₃ catalyst - the silver nitrate and aluminum nitrate Al (NO _{3) 3} · 9H
Example 2 was prepared by dissolving ₂ O and distilled water in solution A.
By the same method as described above, an Ag / Al ₂ O ₃ catalyst in which silver was supported on aluminum oxide Al ₂ O ₃ was obtained. The atomic ratio Ag / Al of silver and aluminum is 1/19.

[0024] - Comparative Example 3; Ag / MnO ₂ catalyst - the silver nitrate and manganese nitrate _{Mn (NO 3) 2 · 6H} 2 O
Using the solution of and dissolved in distilled water as solution A, an Ag / MnO ₂ catalyst in which silver was supported on manganese oxide MnO ₂ was obtained by the same method as in Example 1. The atomic ratio Ag / Mn of silver and manganese is 1/19.

[0025] - Comparative Example 4; Ag / Ga ₂ O ₃ catalyst - the silver nitrate and gallium nitrate _{Ga (NO 3) 3 · 8H} 2 O
Using a solution of and dissolved in distilled water as solution A, an Ag / Ga ₂ O ₃ catalyst in which silver Ag was supported on gallium oxide Ga ₂ O ₃ was obtained by the same method as in Example 1. The atomic ratio Ag / Ga between silver and gallium is 1/19.

[0026] - Comparative Example 5; Ag / Fe ₂ O ₃ catalyst - those of the above-mentioned silver nitrate and iron nitrate _{Fe (NO 3) 3 · 9H} 2 O was dissolved in distilled water as the A solution, the same method as in Example 2 By means of iron oxide Fe ₂ O ₃ loaded with silver Ag /
An Fe ₂ O ₃ catalyst was obtained. The atomic ratio of silver to iron is 1/19 for Ag / Fe.

Table 1 shows the respective catalysts of the above Examples and Comparative Examples.

[0028]

[Table 1]

<Evaluation of Catalyst> Using each of the catalysts of the above-mentioned Examples and Comparative Examples, a test for synthesizing methanol from synthesis gas (hydrogen and carbon monoxide) was conducted, and each temperature characteristic of CO conversion and methanol yield was examined. I checked. The CO conversion is shown in FIG. 1 and the methanol yield is shown in FIG.

According to FIG. 1, Ag / ZrO _{2 of} Example 1 was used.
The catalyst and the Ag / CeO ₂ catalyst of Example 2 were Ag / Zn
Although the conversion rate is higher than O catalyst and Ag / MnO ₂ catalyst, it shows almost the same conversion rate as Ag / Al ₂ O ₃ catalyst,
The conversion rate is lower than that of Ag / Fe ₂ O ₃ catalyst and Ag / Ga ₂ O ₃ catalyst. However, as is clear from FIG. 2, the Ag / Fe ₂ O ₃ catalyst and Ag / Ga ₂ O ₃ catalyst have lower methanol yields than the Ag / ZrO ₂ catalyst and Ag / CeO ₂ catalyst of Examples 1 and _2. Has become. Therefore, from the above results, it is found that the use of zirconia (ZrO ₂ ) or ceria (CeO ₂ ) as a carrier in the silver-based catalyst is advantageous for the synthesis of methanol from the synthesis gas.

<Influence of Neutralizing Solution in Coprecipitation Method> Although sodium hydroxide was used as the neutralizing solution in the preparation of the above Ag / CeO ₂ catalyst (Example 2), sodium carbonate Na ₂ was used as the neutralizing solution. An Ag / CeO ₂ catalyst was prepared by the same coprecipitation method as above using an aqueous CO ₃ solution,
The specific surface area and the methanol yield at 300 ° C. were examined. The results are shown in Table 2 together with an example in which the neutralizing solution is sodium hydroxide.

[0032]

[Table 2]

According to the table, regarding the Ag / CeO ₂ catalyst, the specific surface area and the methanol yield are higher when the sodium hydroxide aqueous solution is used as the neutralizing solution than when the sodium carbonate aqueous solution is used.

Ag using the above aqueous sodium hydroxide solution
The powder X-ray diffraction result of the / CeO ₂ catalyst is shown in FIG. 3, and the same result of the Ag / CeO ₂ catalyst using the aqueous sodium carbonate solution is shown in FIG. According to both figures, the crystal structure of ceria (CeO ₂ ) of both catalysts is the same.
However, the Ag /
Since no peak of silver was observed in the CeO ₂ catalyst, when using sodium hydroxide as the neutralizing solution, the particle size of silver of the obtained catalyst was smaller than that when using sodium carbonate. It can be said that this is one of the reasons for the difference in activity between the two catalysts.

<Influence of catalyst preparation method> In the above, the coprecipitation method was adopted for the preparation of the catalyst, but the effect on the conversion rate and methanol yield when the impregnation method was adopted was investigated.

That is, zirconia (ZrO ₂ ) and ceria (CeO ₂ ) manufactured by Daiichi Rare Element Chemical Industry Co., Ltd. were prepared,
Each of them was impregnated with an aqueous solution of silver nitrate AgNO ₃ manufactured by Kishida Chemical Co., Ltd., dried and calcined to obtain an Ag / ZrO ₂ catalyst (atomic ratio Ag / Zr = 1/19) and an Ag / CeO ₂ catalyst (atomic ratio Ag / Ce = 1/19) was obtained. Then, the temperature characteristics of the CO conversion rate and the methanol yield of the both catalysts were examined. The results are shown in FIGS. 5 and 6 together with the results of the above coprecipitation method.

Regarding the CO conversion rate and the methanol yield of the Ag / CeO ₂ catalyst, the impregnation method showed lower values than the coprecipitation method, but regarding the CO conversion rate and the methanol yield of the Ag / ZrO ₂ catalyst, The impregnation method gave better results. From this, it is understood that it is preferable to adopt the impregnation method for the preparation of the above Ag / ZrO ₂ catalyst.

-Effect of Composition Ratio-Methanol yield at the reaction temperature of 300 ° C. was examined in the test range shown in Table 3 for the above Ag / CeO ₂ catalyst and Ag / ZrO ₂ catalyst. FIG. 7 shows the results.

[0039]

[Table 3]

According to FIG. 7, Ag / CeO ₂ catalyst and A
When the g / ZrO ₂ catalyst is prepared by the coprecipitation method, the methanol yield tends to decrease as the composition ratio increases. On the other hand, the methanol yield of the Ag / ZrO ₂ catalyst prepared by the impregnation method is not so affected by the composition ratio. The above is other reaction temperature 225-275 degreeC.
But the same is true. Therefore, when the above catalysts are prepared by the coprecipitation method, it is preferable to set the composition ratio to 3/7 or less, and further to 1/9 or less. On the other hand, when the Ag / ZrO ₂ catalyst is prepared by the impregnation method, the amount of silver supported may be relatively large.

-Powder X-ray Diffraction Results-In order to investigate the reason why the difference in the above-mentioned preparation methods affects the catalytic activity, A prepared by each of the coprecipitation method and the impregnation method was used.
As a result of examining the powder X-ray diffraction of the g / ZrO ₂ catalyst, the former was as shown in FIG. 8 and the latter was as shown in FIG. 9. As is clear from both figures, the catalyst obtained by the coprecipitation method produces zirconia (ZrO ₂ ) having a crystal structure which is completely different from that obtained by the impregnation method. Therefore, it is considered that this contributes to the difference in the characteristics between the catalyst prepared by the coprecipitation method and the catalyst prepared by the impregnation method.

[Brief description of drawings]

FIG. 1 is a graph showing the temperature characteristics of CO conversion of each catalyst prepared by the coprecipitation method.

FIG. 2 is a graph showing temperature characteristics of methanol yield of each catalyst prepared by a coprecipitation method.

FIG. 3 is an X-ray diffraction pattern diagram of an Ag / CeO ₂ catalyst prepared by a coprecipitation method using an aqueous NaOH solution as a neutralizing solution.

FIG. 4 is an X-ray diffraction pattern diagram of an Ag / CeO ₂ catalyst by a coprecipitation method using an aqueous Na ₂ CO ₃ solution as a neutralizing solution.

FIG. 5 is a graph comparing the CO conversion of Ag / ZrO ₂ catalyst and Ag / CeO ₂ catalyst between the coprecipitation method and the impregnation method.

FIG. 6 is a graph comparing the methanol yields of Ag / ZrO ₂ catalyst and Ag / CeO ₂ catalyst between the coprecipitation method and the impregnation method.

FIG. 7 is a graph showing the relationship between composition ratio and methanol yield for Ag / CeO ₂ catalyst and Ag / ZrO ₂ catalyst.

FIG. 8: Powder X-ray diffraction pattern diagram of Ag / ZrO ₂ catalyst prepared by coprecipitation method

FIG. 9: Powder X-ray diffraction pattern diagram of Ag / ZrO ₂ catalyst prepared by impregnation method

[Explanation of symbols]

 None

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Sakurai 1-831 Midorigaoka, Ikeda City, Osaka Prefecture Industrial Technology Research Institute Osaka Institute of Industrial Technology (72) Inventor Shuji Ikegami, 1304 Kanaokacho, Sakai City, Osaka Daikin Industrial Co., Ltd.Kanaoka Plant, Sakai Works (72) Kenkichi Kagawa, 1304 Kanaoka-cho, Sakai City, Osaka Prefecture Daikin Industries, Ltd.Kanaoka Plant, Sakai Co., Ltd. (72) Sadakazu Usami, 1304, Kanaoka-cho, Sakai City, Osaka Daikin Industries Sakai Plant Kanaoka Plant (72) Inventor Masanobu Kawazoe 1304 Kanaoka Town, Sakai City, Osaka Prefecture Daikin Industries Ltd. Kanaoka Plant, Sakai Plant

Claims (3)

[Claims] 1. Ceria, zirconia, and Ce and Z
A catalyst for methanol synthesis characterized in that one or more metal oxides selected from complex oxides containing at least one metal of r are used as a carrier, and silver is supported on the metal oxide-based carrier. . 2. The method for producing a catalyst for methanol synthesis according to claim 1, wherein the raw material solution is obtained by dissolving a metal compound for forming the metal oxide-based carrier and a silver compound in a solvent. And by mixing the raw material solution with an alkaline solution to precipitate the metal as a hydroxide, which is a precursor of the metal oxide-based carrier, and at the same time, a precursor of the metal oxide-based carrier. A method for producing a catalyst for methanol synthesis, which comprises coprecipitating the above silver with. 3. The method for producing a catalyst for methanol synthesis according to claim 1, wherein the metal oxide-based carrier is impregnated with a solution of a silver compound, and then the solvent of the silver compound solution is evaporated. By so doing, silver is deposited on the above-mentioned metal oxide-based carrier, and a method for producing a catalyst for synthesizing methanol.