JP2695663B2 - Method for producing catalyst for methanol synthesis - Google Patents

Description

The present invention relates to a method for producing a methanol synthesis catalyst used for synthesizing methanol from H ₂ and CO.

[Conventional technology]

Research and development of a methanol synthesis catalyst has been carried out for a long time, and a catalyst having a composition such as zinc oxide-chromium oxide or copper oxide-zinc oxide is prepared by a coprecipitation method or the like. In particular, a catalyst having a ternary metal composition of copper oxide-zinc oxide- (aluminum oxide and / or chromium oxide) is widely used because of its high methanol synthesis activity.

However, the above ternary catalysts have completely different activities depending on the composition and the production method, and no study has been made on a detailed catalyst production method for having the highest activity.

On the other hand, demand for methanol is expected to increase further in the future as a gasoline and emergency gas production, and also as a petrochemical intermediate product, and a large-scale methanol synthesis plant is expected to be constructed worldwide.

However, the current methanol synthesis catalyst has a low initial activity, so it is necessary to recycle a large amount of synthesis gas (CO, H ₂ ), and it is difficult to say that the life is sufficient. Is eagerly awaited.

[Problems to be solved by the invention]

So far, the prepared catalyst containing copper, zinc, aluminum and / or chromium has been prepared by a coprecipitation method, but mainly a method of generating a precipitate by dropping the aqueous solution of a mixed metal salt into an alkaline precipitant. Alternatively, a method in which an aqueous solution of a metal salt and an alkaline precipitation solution are simultaneously dropped to obtain a precipitate in a constant pH range around neutrality is mentioned as an example. As a result, the former method differs in the pH range in which each metal precipitates,
Coprecipitation is unlikely to occur because precipitates of the three metals are separately precipitated, and the precipitates are composed of different crystal seeds, which is not preferable. On the other hand, in the latter method, three kinds of metals precipitate simultaneously,
It forms a crystal seed containing a seed metal, has a relatively large specific surface area and is a uniform catalyst, but does not have the activity to meet the target value.

The present invention has been made in view of the above-mentioned technical state, and aims to provide a method for obtaining a catalyst for methanol synthesis containing copper, zinc and (aluminum and / or chromium) which is highly active and has excellent durability.

[Means for solving the problem]

The present inventors have conducted intensive research on the development of a catalyst that exceeds the performance of existing methanol synthesis catalysts, and as a result, clarified that the main active species in the methanol synthesis reaction is Cu1 ^+. The invention has been completed.

That is, in the present invention, when producing a methanol synthesis catalyst containing at least copper, zinc and aluminum and / or chromium as a metal component, zinc is first added to an aqueous alkaline precipitant solution kept at a predetermined temperature while stirring the aqueous solution. And an aqueous solution containing aluminum and / or chromium is added dropwise to form a precipitate under alkaline conditions. After the completion of the addition, an aqueous solution containing copper is added dropwise and the precipitate is further added on the precipitate under alkaline conditions. To generate
A method for producing a catalyst for methanol synthesis, characterized by washing and firing the precipitate.

The composition ratio of the composite oxide which is the catalyst for methanol synthesis targeted in the present invention is as follows: Cu: 100 (atomic ratio), Zn: 10
250250, Al and / or Cr: 1〜100.

Hereinafter, the method for producing the methanol synthesis catalyst of the present invention will be described in more detail.

First, an aqueous solution of an alkaline precipitant is kept warm, and an aqueous solution containing A1 and / or Cr and Zn is added dropwise with stirring to precipitate a precipitate under alkaline conditions. After the addition, an aqueous solution containing Cu is added dropwise. To form a precipitate under alkaline conditions. The pH at the end of the dropping is adjusted to be alkaline, preferably 8 or more.

Precipitant solution is an alkali solution, typically 0.1~10M concentration of _{Na 2 CO 3, NaHCO 3,} NaOH, K 2 CO 3, NH 3 aqueous solution used by, inter alia aqueous Na ₂ CO ₃ are preferred. Further, it is preferable to maintain the temperature of the solution at the time of forming the precipitate in the range of 15 to 90 ° C.

Furthermore, the metal salts of Cu, Zn, and Al and / or Cr are used in the form of nitrates, chlorides, sulfates, and acetates as aqueous solutions having a concentration of 0.01 to 1.0 M, and are particularly preferably used as nitrates.

The dropping time and the aging time are not particularly affected, but may be any conditions under which the metal ions are uniformly dispersed and a precipitate is deposited, and usually the dropping time is 0.1 minute to 3 hours, and the aging time is 0.1 minute to 3 hours. Will be implemented.

Although the obtained precipitate has various crystal seeds, a methanol synthesis catalyst is obtained by sufficiently washing and removing alkali metals and anions and then calcining at 200 to 400 ° C. This catalyst is almost amorphous, although CuO and ZnO crystal seeds are observed. However, the ZnO-Al ₂ O ₃ composite oxide having a high specific surface area was first recognized by EXAFS (X-ray absorption wide area continuous fine structure), XANES (X-ray absorption edge structure), etc. It was found that CuO was uniformly dispersed in the sample.

A highly active methanol synthesis catalyst was obtained by the above production method, and the specific production method will be described in detail in the following Examples.

〔Example〕

Example 1 Dissolve 2.5 mol of sodium carbonate (Na ₂ CO ₃ ) in water 2
Keep at ℃. This alkaline aqueous solution is referred to as solution A. Dissolving zinc nitrate _{{Zn (NO 3) 2 ·} 6H 2 O} 0.225mol aluminum nitrate _{{Al (NO 3) 3 ·} 9H 2 O} 0.075mol water 600cc, maintained at 80 ° C., a solution of this acid solution B. Copper nitrate ｛Cu (NO ₃ ) ₂ 3H ₂ O｝ 0.3mol and dissolved in water 300cc, 80
The temperature was kept at 0 ° C., and this acidic solution was designated as solution C.

First, the solution B is uniformly dropped into the solution A over 30 minutes with stirring to obtain a suspension. Next, after dropping the solution B, the solution C was dropped into the suspension at a constant rate over 30 minutes,
A precipitate is obtained. The pH at the end of the dropwise addition was 8.

After dropping, aging was performed for 2 hours, and then the precipitate was filtered and Na
Wash so that ions and NO ₃ ions are not detected. Further, the resultant is dried at 100 ° C. for 24 hours and then calcined at 300 ° C. for 3 hours to obtain a methanol synthesis catalyst. This catalyst is referred to as catalyst 1.

Example 2 zinc nitrate _{{Zn (NO 3) 2 ·} 6H 2 O} in B solution 0.3 mol, except that the addition of aluminum nitrate _{{Al (NO 3) 3 ·} 9H 2 O} 0.05mol from Example 1 A methanol synthesis catalyst was produced by the same production method. This catalyst is referred to as catalyst 2.

Further zinc nitrate solution B _{{Zn (NO 3) 2 ·} 6H 2 O} 0.2mol
And aluminum nitrate _{{Al (NO 3) 3 ·} 9H 2 O} 0.075mol the C solution of copper nitrate _{{Cu (NO 3) 2 ·} 3H 2 O} to 0.325 mol, zinc nitrate solution B {Zn (NO _{3) 2} · 6H ₂ O} 0.225mol aluminum nitrate _{{Al (NO 3) 3 ·} 9H 2 O} 0.1mol and C solution of copper nitrate {C
u (NO ₃ ) ₂ .3H ₂ Omol0.275 mol was added, and the mixture was produced in the same manner as in Example 1 to obtain Catalyst 3 and Catalyst 4.

Example 3 B solution of zinc nitrate _{{Zn (NO 3) 2 ·} 6H 2 O} 0.225mol and chromium nitrate _{{Cr (NO 3) 3 ·} 9H 2 O} was added 0.075mol same as in Example 1 According to the production method, a catalyst 5 was obtained.

Further zinc nitrate solution B _{{Zn (NO 3) 2 ·} 6H 2 O} 0.225mo
l, chromium nitrate _{{Cr (NO 3) 3 ·} 9H 2 O} 0.05mol, adding aluminum nitrate _{{Al (NO 3) 3 ·} 9H 2 O} 0.05mol, prepared in the same production method as in Example 1 Thus, catalyst 6 was obtained.

Comparative Example 1 A conventional catalyst was produced using the solutions A, B, and C having the same composition as in Example 1 by the following method.

First, the solution C is added to the solution B at a time to obtain an acidic aqueous solution (pH = 3) containing zinc, aluminum, and copper ions. The solution A is added dropwise to this aqueous solution at a constant speed for 30 minutes while stirring. The pH at the end of the dropwise addition was 8. After dripping 2
After aging for a while, a catalyst 7 was obtained by the same production method as in Example 1.

[Experimental example 1] The activity evaluation test of the methanol synthesis reaction of catalysts 1 to 7 obtained in Examples 1 to 3 and Comparative example 1 was performed under the following conditions.

Raw material gas: H ₂ 67 mol%, CO 33 mol% GHSV: 8000 h ^-1 Reaction temperature: 250 ° C. Reaction pressure: 50 kg / cm ² G The catalyst sized to 16-28 mesh is filled in a ₂ cc microreactor, and H ₂ 3 After reduction treatment with a% / N ₂ base gas, a raw material gas was supplied, and an initial activity was evaluated.
Table 1 shows the results of the initial activity evaluation of each catalyst.

[Experimental example 2] The catalysts 1 and 7 used for the initial activity evaluation were used as catalysts for durability test. The reaction conditions were the same as in Experimental Example 1, and the activity results are shown in Table 2.

As shown in Table 2, the methanol synthesis catalyst prepared according to the present invention was found to be much more durable than the conventional catalyst.

〔The invention's effect〕

According to the present invention, a highly active and durable methanol synthesis catalyst containing copper, zinc, aluminum and / or chromium can be obtained.

Claims (1)

(57) [Claims] In producing a methanol synthesis catalyst containing at least copper, zinc, aluminum and / or chromium as a metal component, zinc is first added to an aqueous solution of an alkaline precipitant kept at a predetermined temperature while stirring the aqueous solution. And an aqueous solution containing aluminum and / or chromium is added dropwise to form a precipitate under alkaline conditions. After the completion of the addition, an aqueous solution containing copper is added dropwise and the precipitate is further added on the precipitate under alkaline conditions. A method for producing a catalyst for methanol synthesis comprising washing the precipitate and calcining the precipitate.