JP3328684B2 - Catalyst for methanol synthesis and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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, and various catalysts such as a catalyst obtained by adding chromium oxide, aluminum oxide, and the like, and a palladium catalyst have been proposed. ing.

[0003] 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.
Japanese Patent No. 90232 discloses an oxide catalyst containing copper, zinc and aluminum, and Japanese Patent Application Laid-Open No. Hei 4-122450 discloses five kinds of oxides: copper oxide, zinc oxide, chromium oxide, aluminum oxide, and aluminum oxide impregnated with silver. A catalyst consisting of a mixture, but for synthesizing a gas rich in methanol from hydrogen and carbon dioxide, is described respectively.

[0004]

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

[0005]

The inventor of the present invention has conducted various experiments and studies on such a problem, and as a result, has determined that a specific type of metal oxide is used as a carrier and silver is supported on the carrier. It has been found that high activity and selectivity can be obtained in such a case, and the present invention has been completed. Less than,
The invention according to each claim will be specifically described.

(Invention of Claim 1) The present invention provides a method for synthesizing methanol from hydrogen and carbon monoxide.
A catalyst for synthesizing methanol, comprising ceria, zirconia, and at least one metal oxide selected from multiple oxides containing Ce and Zr as a carrier, wherein silver is contained in the metal oxide-based carrier. it characterized in that it is carried.

The catalyst provides relatively high activity (conversion rate of carbon monoxide) and selectivity (yield of methanol). Although the reason is not clear, silver as a catalyst metal and an oxide of Ce or Zr as a carrier , or Ce and Zr
It is conceivable that silver is made finer or highly dispersed and supported by interaction with the contained double oxide .

(Invention according to claim 2) The present invention relates to the method for producing a catalyst for methanol synthesis according to claim 1, wherein a metal compound for forming the metal oxide-based support is used. A raw material solution prepared by dissolving a silver compound in a solvent is prepared, and by mixing the raw material solution and an alkaline solution, the metal is precipitated 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 in the precursor of the metal oxide carrier.

In the present invention, a so-called coprecipitation method is employed for the preparation of the catalyst for methanol synthesis. In this method, the dispersibility of silver in the metal oxide-based carrier is increased and the activity is improved. It will be advantageous.

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

The metal compound constituting the metal oxide-based carrier is preferably an electrolyte such as acetate, nitrate, sulfate, etc., especially a water-soluble one, and the same applies to a silver compound. Examples of the precipitation reagent include NaOH, NH4 OH, N
a2 CO3, etc., to thereby adjust the pH of the raw material solution
Will be adjusted. In addition, the obtained coprecipitate may be washed and dried, and then calcined at a temperature of about 300 to 600 ° C. In use, for example, by solidifying the catalyst powder and pulverizing it, Particles of an appropriate size may be packed in a column.

According to a third aspect of the present invention, there is provided a method for producing a catalyst for methanol synthesis according to the first aspect, wherein the metal oxide-based support is impregnated with a solution of a silver compound. Silver is deposited on the metal oxide-based carrier by evaporating the solvent of the silver compound solution.

That is, the present invention employs an impregnation method for the production of the catalyst. The present inventor has found that, in general, in the case of the impregnation method from various experiments and the like, even if the amount of the supported catalyst metal is increased, the dispersibility is high only by supporting the catalyst metal in a lump at a site where the carrier surface easily adheres. Instead, the inventors have found that the specific surface area of the catalyst is greatly reduced, and have come to the invention according to claim 2. However, this is not always the case in the case of a combination of a metal oxide as a carrier and silver as a catalyst metal, especially when the carrier is zirconia, the impregnation method rather improves the activity and selectivity of the catalyst. The present invention has been found to be advantageous, and the present invention has been completed.

[0014]

According to the first aspect of the present invention, hydrogen and hydrogen
Methanol for synthesizing methanol from carbon oxide
A catalyst for synthesis, comprising ceria, zirconia, and Ce
Since one or more metal oxides selected from multiple oxides containing Zr and Zr are used as a carrier and silver is carried on the metal oxide-based carrier, high activity and high selectivity can be obtained.

According to the second aspect of the present invention, a raw material solution is prepared by dissolving a metal compound and a silver compound for forming the metal oxide-based carrier in a solvent, and the raw material solution and the alkali solution are prepared. Is mixed, thereby precipitating the metal as a hydroxide or the like which is a precursor of the metal oxide carrier, and simultaneously co-precipitating the silver with the precursor of the metal oxide carrier. And silver can be supported on the metal oxide carrier in a highly dispersed state, which is advantageous for obtaining the highly active and highly selective catalyst for methanol synthesis according to the first aspect.

According to the third aspect of the present invention, after the metal oxide carrier is impregnated with the solution of the silver compound, the solvent of the silver compound solution is evaporated, whereby silver is deposited on the metal oxide carrier. Since the catalyst is deposited, a catalyst having high activity and high selectivity can be obtained.

[0017]

Embodiments of the present invention will be described below.

<Preparation of Catalyst> Example 1: Ag / ZrO2 catalyst- A predetermined amount of each of silver nitrate (AgNO3 manufactured by Kishida Chemical Co., Ltd.) and zirconium nitrate ZrO (NO3) 2.6H2O was weighed, and this was distilled water. This was dissolved to obtain solution A. On the other hand, an aqueous solution of sodium carbonate was prepared as a neutralizing solution (precipitation reagent), and this was used as solution B.

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

The obtained Ag / ZrO 2 catalyst is obtained by highly dispersing silver on zirconia (ZrO 2).
The atomic ratio Ag / Zr between silver and zirconium is 1/19.
It is.

Example 2 Ag / CeO2 catalyst- Silver nitrate and cerium nitrate Ce (NO3) 3.6H2O
Are weighed in predetermined amounts, and are dissolved in distilled water to obtain a solution A, and an aqueous solution of sodium hydroxide is used as a solution B, and Ag in which silver is supported on ceria (CeO2) is obtained in the same manner as in Example 1. / CeO2 catalyst was obtained. The atomic ratio Ag / Ce of silver and cerium is 1/19.

Comparative Example 1 Ag / ZnO Catalyst-- A solution prepared by dissolving the above silver nitrate and zinc nitrate Zn (NO 3) 2 .6H 2 O in distilled water was used as solution A, and zinc oxide ZnO was prepared in the same manner as in Example 1. Ag / silver supported
A ZnO catalyst was obtained. The atomic ratio Ag / Zn of silver and zinc is 1 /
19

Comparative Example 2: Ag / Al2 O3 catalyst-Silver nitrate and aluminum nitrate Al (NO3) 3.9H
Example 2 was prepared by dissolving 2 O in distilled water as solution A.
An Ag / Al2 O3 catalyst in which silver was supported on aluminum oxide Al2 O3 was obtained in the same manner as described above. The atomic ratio Ag / Al between silver and aluminum is 1/19.

Comparative Example 3 Ag / MnO2 Catalyst- The above silver nitrate and manganese nitrate Mn (NO3) 2.6H2O
Was dissolved in distilled water as solution A, and an Ag / MnO2 catalyst comprising manganese oxide MnO2 carrying silver was obtained in the same manner as in Example 1. The atomic ratio Ag / Mn of silver and manganese is 1/19.

Comparative Example 4 Ag / Ga 2 O 3 Catalyst— The above silver nitrate and gallium nitrate Ga (NO 3) 3 .8H 2 O
By dissolving these in distilled water as solution A, an Ag / Ga2 O3 catalyst comprising gallium oxide Ga2 O3 carrying silver Ag was obtained in the same manner as in Example 1. The atomic ratio Ag / Ga between silver and gallium is 1/19.

Comparative Example 5: Ag / Fe2 O3 Catalyst-A solution prepared by dissolving the above silver nitrate and iron nitrate Fe (NO3) 3.9H2 O in distilled water was used as solution A, and iron oxide Fe2 was prepared in the same manner as in Example 2. Ag / silver supported on O3 /
An Fe2 O3 catalyst was obtained. The atomic ratio of silver to iron is 1/19 for Ag / Fe.

Table 1 summarizes the catalysts of the above Examples and Comparative Examples.

[0028]

[Table 1]

<Evaluation of Catalyst> A test was conducted to synthesize methanol from synthesis gas (hydrogen and carbon monoxide) using each of the catalysts of the above Examples and Comparative Examples, and the temperature characteristics of CO conversion and methanol yield were measured. Was examined. FIG. 1 shows the CO conversion and FIG. 2 shows the methanol yield.

According to FIG. 1, the Ag / ZrO 2 of Example 1 was used.
The catalyst and the Ag / CeO2 catalyst of Example 2 were Ag / Zn
Although the conversion is higher than that of the O catalyst or the Ag / MnO2 catalyst, the conversion is almost the same as that of the Ag / Al2 O3 catalyst.
The conversion is lower than that of the Ag / Fe2 O3 catalyst or the Ag / Ga2 O3 catalyst. However, as is apparent from FIG. 2, the Ag / Fe2 O3 catalyst and the Ag / Ga2 O3 catalyst have lower methanol yields than the Ag / ZrO2 catalyst and the Ag / CeO2 catalyst of Examples 1 and 2. Therefore, it can be seen from the above results that the use of zirconia (ZrO2) or ceria (CeO2) as a carrier in a silver-based catalyst is advantageous for the synthesis of methanol from synthesis gas.

<Effect of Neutralizing Solution in Coprecipitation Method> In the preparation of the above Ag / CeO2 catalyst (Example 2), sodium hydroxide was used as a neutralizing solution, but a sodium carbonate aqueous solution of Na2 CO3 was used as a neutralizing solution. Was used to prepare an Ag / CeO2 catalyst by the same coprecipitation method, and its specific surface area and methanol yield at 300 DEG C. were examined.
The results are shown in Table 2 together with examples in which the neutralizing solution is sodium hydroxide.

[0032]

[Table 2]

According to the table, with respect to the Ag / CeO2 catalyst, the specific surface area and the methanol yield are higher when the aqueous solution of sodium hydroxide is used as the neutralizing solution than when the aqueous solution of sodium carbonate is used.

Ag using the above sodium hydroxide aqueous solution
The powder X-ray diffraction results of the / CeO2 catalyst are as shown in FIG. 3, and the results of the Ag / CeO2 catalyst using the aqueous sodium carbonate solution are as shown in FIG. According to both figures, the crystal structures of ceria (CeO2) of both catalysts are the same.
However, Ag / Ag using the aqueous sodium hydroxide solution of FIG.
Since no peak of silver is observed in the case of the CeO2 catalyst, when the sodium hydroxide is used as a neutralization solution, the silver particle size of the obtained catalyst is finer than when sodium carbonate is used. It can be said that this contributes to the difference between the activities of the two catalysts.

<Effects of Catalyst Preparation Method> In the above, the coprecipitation method was used for the preparation of the catalyst. The effect of the impregnation method on the above conversion and methanol yield was examined.

That is, zirconia (ZrO2) and ceria (CeO2) manufactured by Daiichi Kagaku Kagaku Kogyo Co., Ltd. were prepared.
Each was impregnated with an aqueous solution of silver nitrate AgNO3 manufactured by Kishida Chemical Co., Ltd., dried and calcined to obtain an Ag / ZrO2 catalyst (Ag / Zr = 1/19) and an Ag / CeO2 catalyst (Ag / Ce = 1). / 19). The temperature characteristics of the CO conversion and the methanol yield were examined for both catalysts. The results are shown in FIGS. 5 and 6 together with the results of the above-mentioned coprecipitation method.

Regarding the CO conversion and the methanol yield of the Ag / CeO2 catalyst, the impregnation method showed lower values than the coprecipitation method, but the CO conversion and the methanol yield of the Ag / ZrO2 catalyst were as follows: The impregnation method gave better results. From this, it can be seen that it is preferable to use the impregnation method for the preparation of the above Ag / ZrO2 catalyst.

-Effect of Composition Ratio- For the above Ag / CeO2 catalyst and Ag / ZrO2 catalyst, the methanol yield at a reaction temperature of 300 ° C. was examined in the test range shown in Table 3. FIG. 7 shows the results.

[0039]

[Table 3]

According to FIG. 7, the Ag / CeO 2 catalyst and A
When the g / ZrO2 catalyst is prepared by a coprecipitation method, the methanol yield tends to decrease as the composition ratio increases. On the other hand, the methanol yield of the Ag / ZrO2 catalyst prepared by the impregnation method is not so affected by the composition ratio. The above is for other reaction temperatures of 225 to 275 ° C.
But the same is true. Therefore, when each of the above catalysts is prepared by the coprecipitation method, it is understood that the composition ratio is preferably set to 3/7 or less, more preferably 1/9 or less. On the other hand, when the Ag / ZrO2 catalyst is prepared by the impregnation method, it can be seen that the supported amount of silver may be relatively large.

-Results of powder X-ray diffraction- In order to investigate the cause of the above-mentioned difference in the preparation method affecting 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 / ZrO2 catalyst, the former was as shown in FIG. 8 and the latter was as shown in FIG. As is clear from both figures, the zirconia (ZrO2) having a crystal structure completely different from that obtained by the impregnation method is generated in the catalyst by the coprecipitation method. Therefore, it is considered that this contributes to the difference in characteristics between the catalyst prepared by the coprecipitation method and the catalyst prepared by the impregnation method.

[Brief description of the drawings]

FIG. 1 is a graph showing temperature characteristics of CO conversion of each catalyst prepared by a 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 / CeO2 catalyst 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 / CeO2 catalyst by a coprecipitation method using an aqueous solution of Na2 CO3 as a neutralizing solution.

FIG. 5 is a graph showing a comparison between the coprecipitation method and the impregnation method regarding the CO conversion of the Ag / ZrO2 catalyst and the Ag / CeO2 catalyst.

FIG. 6 is a graph comparing the methanol precipitation of the Ag / ZrO2 catalyst and the Ag / CeO2 catalyst with the coprecipitation method and the impregnation method.

FIG. 7 is a graph showing the relationship between the composition ratio and the methanol yield for Ag / CeO2 catalyst and Ag / ZrO2 catalyst.

FIG. 8 is a powder X-ray diffraction pattern diagram of an Ag / ZrO2 catalyst prepared by a coprecipitation method.

FIG. 9 is a powder X-ray diffraction pattern diagram of an Ag / ZrO2 catalyst prepared by an impregnation method.

[Explanation of symbols]

 None

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shuji Ikegami 1304 Kanaokacho, Sakai City, Osaka Daikin Industries, Ltd.Sakai Factory Kanaoka Factory (72) Inventor Kenkichi Kagawa 1304, Kanaokacho, Sakai City, Osaka Daikin Industries Sakai Seisakusho Kanaoka Plant (72) Inventor Seiichi Usami 1304 Kanaokacho, Sakai City, Osaka Daikin Industries Co., Ltd.Sakai Seisakusho Kanaoka Plant (72) Inventor Masanobu Kawazoe 1304 Kanaokacho, Sakai City, Osaka Daikin Kogyo Investigator, Eiko Shigeta, Sakai Works Kanaoka Factory (56) References JP-A-8-215576 (JP, A) Baiker A, Hydrogenation of CO2 over copper, silver and gold / zirconia catalog: rative s tudy of catalyst p r, Studies in Surfa ce Sience and Cata lysis, 75 (New Fronti ers in Catalysis), 1257-1272 (58) investigated the field (Int.Cl. ^7, DB name) B01J 21/00 - 37/36 JICST File (JOIS) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. A method for synthesizing methanol from hydrogen and carbon monoxide.
A catalyst for synthesizing methanol , comprising at least one metal oxide selected from the group consisting of ceria, zirconia, and a complex oxide containing Ce and Zr. A catalyst for methanol synthesis, characterized in that is supported. 2. The method for producing a catalyst for methanol synthesis according to claim 1, wherein a metal compound and a silver compound for forming the metal oxide-based support are dissolved in a solvent. By mixing the raw material solution and the alkali solution, thereby precipitating the metal as a hydroxide or the like 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, comprising co-precipitating the above-mentioned silver into the mixture. 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. A method for producing a catalyst for methanol synthesis, comprising depositing silver on the metal oxide-based support by the above method.