JP4103069B2 - Method for producing dimethyl ether synthesis catalyst and dimethyl ether synthesis catalyst - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dimethyl ether synthesis catalyst for synthesizing dimethyl ether (DME) from carbon monoxide (CO) and hydrogen (H ₂ ), and a method for producing the same.
[0002]
[Prior art]
Dimethyl ether (also referred to as DME in the present specification) has recently attracted high interest as a clean and easy-to-handle new fuel, and is expected to increase in demand as an alternative fuel for LPG and light oil.
Conventionally, as a method for preparing a DME synthesis catalyst, a coprecipitation method described in JP-A-2001-70793, JP-A-2001-179103, JP-A-2001-314769, and the like can be exemplified.
[0003]
For example, in the coprecipitation method, a metal oxide or a metal hydroxide is precipitated by adding an acid or an alkali to an aqueous solution of an inorganic metal salt. However, when the coprecipitation method is used, the dispersibility of the catalytically active component is poor, and the catalytically active component is sintered (aggregated) by heat, which may cause a reduction in reforming performance. In addition, it is difficult to eliminate impurities contained in the raw material, the salts used during precipitation are likely to be taken up as impurities, and there is a tendency to cause problems such as difficulty in preparing a homogeneous product due to variations in pH during the growth of the precipitate. .
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and is obtained by a method for producing a dimethyl ether synthesis catalyst capable of obtaining a homogeneous catalyst with good dispersibility of catalytically active components, low impurity incorporation, and the production method. An object is to provide a catalyst for synthesis of dimethyl ether.
[0005]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a method for producing a dimethyl ether synthesis catalyst for synthesizing dimethyl ether from carbon monoxide and hydrogen.
Obtaining a dispersion of metal alkoxide;
Adding an acid to the dispersion to hydrolyze the gold alkoxide to form a sol;
A step of adding Cu and Zn used as catalytic active components as an aqueous solution to the sol obtained in the step of solification;
Evaporating and drying the sol solution to obtain a gel;
The obtained gel is dried, calcined, and hydrogen reduced to obtain a DME synthesis catalyst, and a dimethyl ether synthesis catalyst is produced by a sol-gel method.
In the method for producing a dimethyl ether synthesis catalyst according to the present invention, a carrier for supporting a catalytically active component is also prepared when the sol-gel method is carried out . The carrier has a Lewis acid action . The Lewis acid action is an action of dehydrating methanol, which is an intermediate of the dimethyl ether synthesis reaction, to promote the dimethyl ether synthesis reaction. The carrier content is preferably 40% by weight or more and 95% by weight or less.
The method for producing a dimethyl ether synthesis catalyst according to the present invention includes the above-described steps, and a supplementary explanation is given below for some steps.
[0006]
Step of obtaining metal alkoxide dispersion In this step, the metal alkoxide is generally dispersed in hot water at 65 to 75 ° C. to obtain a dispersion.
Step of adding acid to the dispersion to hydrolyze the metal alkoxide to form a sol In this step, generally, nitric acid is added to the dispersion to adjust the pH to 2-3.
The sol obtained in the step of the sol, in Step of adding Cu and Zn is used as the catalytically active component as an aqueous solution, generally, it added Cu and Zn as an acid solution, stirred warmed.
[0007]
In another aspect, the present invention is a dimethyl ether synthesis catalyst produced by the above production method. The dimethyl ether synthesis catalyst preferably contains 5 to 60% by weight of Cu and Zn as catalytic active components, and Cu / Zn is preferably in the range of 100/0 to 40/60 by weight ratio.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the dimethyl ether synthesis catalyst and the production method thereof according to the present invention will be described in more detail with respect to the embodiments thereof.
In the present invention, a DME synthesis catalyst is prepared by a sol-gel method. Examples of the metal alkoxide that can be employed as a raw material for catalyst preparation include aluminum isopropoxide (Al [OCH (CH ₃ ) ₂ ] ₃ ), aluminum ethoxide, and aluminum butoxide. The metal component contained in the metal alkoxide is generally present in the form of an oxide in the DME synthesis catalyst, and mainly serves as a carrier for supporting the catalytically active component and to promote the dehydration condensation reaction of methanol. .
[0009]
In the sol-gel method, a metal alkoxide is dispersed in a solvent (water or the like), and an acid is added thereto to adjust the pH to 2-3. Examples of the acid used include nitric acid, hydrochloric acid, and sulfuric acid. This causes a hydrolysis reaction to form a uniform sol. To this sol, a solution containing a catalytically active component, that is, a catalytic metal aqueous solution is added and sufficiently stirred. As the catalytic metal aqueous solution, a copper nitrate aqueous solution is used for Cu, and a zinc nitrate aqueous solution is used for Zn. In addition, since it can employ | adopt for this invention if it can become a catalyst active component of a DME synthesis catalyst, other metals other than Cu and Zn can be used as a catalyst metal candidate. For such other metals, the present invention can be carried out by using a predetermined aqueous solution.
[0010]
The sol to which the catalytic metal aqueous solution is added is gelled. In the gelation, it is preferable to evaporate and dry the mixed solution. Generally, gelation is performed by evaporating and drying the mixed solution with an evaporator. Further, the gel is dried, calcined, and then subjected to a reduction treatment to prepare a DME synthesis catalyst.
[0011]
The DME synthesis catalyst prepared by the sol-gel method has a high degree of dispersion of the catalyst metal supported on the carrier, and can suppress the particle diameter of the metal small. In addition, since the catalyst metal is supported in a state in which it is incorporated in the support, cindering of the catalyst itself is less likely to occur, and a catalyst having excellent thermal durability can be obtained. Conventionally, as described above, in the coprecipitation method, salts used at the time of precipitation have been easily taken up as impurities. However, when a DME synthesis catalyst is prepared by the sol-gel method as in the present invention, a material that is easily decomposed or sublimated during firing is used as a raw material. A DME synthesis catalyst in which is uniformly dispersed can be obtained.
[0012]
In addition, when a carrier such as γ-Al ₂ O ₃ is prepared by a sol-gel method, it is possible to control so as to increase the number of pores that are homogeneous and contribute to catalytic activity. For this reason, a very highly active DME synthesis catalyst can be obtained.
[0013]
The reaction for synthesizing DME from carbon monoxide and hydrogen is represented by the following formula (1).
3H ₂ + 3CO⇔CH ₃ OCH ₃ + CO ₂ (1)
However, in practice, CO + 2H ₂ ⇔CH ₃ OH (2) Methanol synthesis reaction 2CH ₃ OH ⇔CH ₃ OCH ₃ + H ₂ O (3) Dehydration reaction CO + H ₂ O ⇔H ₂ + CO ₂ (4) Water gas shift reaction First, methanol is produced from carbon monoxide and hydrogen, and then dimethyl ether is produced by dehydration condensation of methanol. Furthermore, water reacts with carbon monoxide by the water gas shift reaction to produce hydrogen and carbon dioxide.
[0014]
In order to advance these reactions, generally, a methanol synthesis catalyst, a methanol dehydration catalyst, and a water gas shift catalyst are required. However, in the DME synthesis catalyst obtained by the present invention, these reactions can be performed with one kind of catalyst.
[0015]
That is, by containing copper (Cu) as the catalyst metal, the methanol synthesis reaction of the above formula (2) is promoted. Furthermore, by containing zinc (Zn), the reverse shift reaction (formation of carbon monoxide and water from hydrogen and carbon dioxide) of the above formula (4) can be suppressed. At this time, the ratio of Cu and Zn is preferably contained in the range of 100/0 to 40/60. Further, if the total amount of Cu and Zn is less than 5% by weight of the total catalyst, the reaction of the above formula (2) hardly occurs, and if it exceeds 60% by weight, the amount of Al ₂ O ₃ decreases and high dispersibility is obtained. I can't keep it. For this reason, reaction of said (3) type | formula becomes difficult to occur, and reforming performance will fall. Therefore, the total amount of Cu and Zn as the catalytically active components is preferably in the range of 5 to 60% by weight in the DME synthesis catalyst. Thereby, a very excellent catalytic activity can be obtained.
[0016]
Furthermore, carriers such as γ-Al ₂ O ₃ prepared by the sol-gel method have many Lewis acid sites suitable for synthesizing DME by dehydrating methanol (reaction of the above formula (3)). have. That is, it has a Lewis acid action. For this reason, there exists a function which accelerates | stimulates the above-mentioned stepwise DME synthesis reaction, and it can synthesize | combine efficiently from low temperature. Therefore, a very excellent catalyst having a high DME production rate and high selectivity can be obtained. In addition, very high reforming performance can be obtained when the carrier such as γ-Al ₂ O ₃ is contained in the DME synthesis catalyst in an amount of 40 wt% or more and 95 wt%.
[0017]
Example 1
Add 9.7901 g of aluminum isopropoxide (Al [OCH (CH ₃ ) ₂ ] ₃ hereinafter referred to as AIP) crushed in a mortar into 100 ml of hot water at 70 ° C., and stir and heat the dispersion of AIP. Obtained. Nitric acid was added little by little to this dispersion, and the pH was adjusted to 2-3 while dissolving AIP. This solution was stirred at 70 ° C. for 10 minutes or more to cause hydrolysis to form a clear sol. To this sol solution, 31.95 ml of 167.42 g / liter copper nitrate trihydrate aqueous solution and 9.00 ml of 79.02 g / liter zinc nitrate hexahydrate aqueous solution were added and kept at 70 ° C. for 10 minutes or more. Stir. Furthermore, nitric acid was added to this solution, and finally adjusted to pH 1-2. Thereafter, this sol solution was evaporated and dried using an evaporator and an 80 ° C. hot water bath to obtain about 8 g of a gelled powder. This gel was dried at 150 ° C. for 12 hours, further calcined at 500 ° C. for 5 hours, and then subjected to reduction treatment in a hydrogen atmosphere at 450 ° C. for 10 hours.
[0018]
This reduction condition is a condition in which a certain degree of sintering is caused in the pretreatment stage in order to prevent the sintering of the catalyst during the reaction in consideration of comparison of the catalyst activity. In practice, it is sufficient to perform the reduction at 250 to 300 ° C. for 4 to 5 hours.
Thus, 3.9 g of Cu—Zn (36-4 wt%) / Al ₂ O ₃ catalyst was produced. At this time, the total amount of Cu and Zn was 40% by weight, and the Cu / Zn was adjusted to 9/1.
[0019]
Comparative Example 1
Commercially available Cu-Zn (50-50 wt%) catalyst (Nikki Chemical ■ Ltd. N211) 2 g and Al ₂ O ₃ (manufactured by Sumitomo Chemical ■ manufactured BK103) 2 g The physically mixed Cu-Zn (25-25 wt %) / Al ₂ O ₃ catalyst 4 g was produced. At this time, Cu—Zn and Al ₂ O ₃ were mixed at a ratio of 1/1.
[0020]
DME synthesis reaction test <br/> was prepared according to Example 1 and Comparative Example 1 Cu-Zn (36-4 wt%) / Al ₂ O ₃ (sol-gel) catalyst and Cu-Zn (25-25 wt%) / Al ₂ O ₃ (commercially available) catalyst was placed in the reaction tube of the atmospheric pressure fixed bed flow system reactor. Carbon monoxide, hydrogen, and argon as an internal standard gas (H ₂ /CO/Ar=7.5/7.5/1.5 ml / min) were introduced into the reaction tube and allowed to flow. The amount of DME produced (Rate of DME production / μmol / g / h) was measured by analyzing the produced gas after passing through the catalyst with a gas chromatograph. At this time, the reaction tube in which the catalyst was arranged was heated by an electric furnace, and the reaction temperature was controlled at 150 ° C to 350 ° C. Each sample amount was 0.5 g.
[0021]
FIG. 1 shows a Cu—Zn (36-4 wt%) / Al ₂ O ₃ (sol-gel) catalyst and Cu—Zn (25-25 wt%) / Al ₂ O ₃ (Example 1 and Comparative Example 1). The amount of DME produced with respect to the reaction temperature of a commercially available catalyst is shown. As a result, the maximum production amount of the commercial product is about 9 μmol / g / h, whereas the sol-gel catalyst of the present invention is about 24 μmol / g / h, which is 2.5 times or more of DME production amount. It was.
From this, it was understood that the catalyst (Example 1) produced by the sol-gel method of the present invention has a function of greatly promoting the DME synthesis reaction.
[0022]
The commercial product (Comparative Example 1) was activated at 300 to 325 ° C., whereas the sol-gel catalyst of the present invention (Example 1) was 200 to 250 ° C., and the commercial product ( It was active at a temperature about 100 ° C. lower than Comparative Example 1). Therefore, it is understood that the DME synthesis catalyst according to the present invention is very excellent in low temperature activity.
[0023]
FIG. 2 shows the amount of DME produced with respect to the reaction time of the Cu—Zn (36-4 wt%) / Al ₂ O ₃ (sol-gel) catalyst shown in Example 1. The test method was the same as the DME synthesis reaction test described above, and only the reaction temperature was kept constant at 220 ° C., and the amount of DME produced when continuously in contact with the raw material gas for 75 hours was measured.
[0024]
As a result, the production amount of the sol-gel catalyst according to the present invention (Example 1) hardly decreased until 75 hours after it was once activated. This shows that the DME synthesis catalyst according to the present invention is very excellent in durability.
From these results, the DME synthesis catalyst according to the present invention produced by the sol-gel method has a very high activity because the supported catalyst metal has a high degree of dispersion and the metal particle size can be controlled small. It is understood that the catalyst is excellent in low temperature activity.
Further, as understood from the above results, according to the present invention, since the catalytic metal is supported in a state of being incorporated in the carrier, the metal itself is less likely to be sintered, and the heat durability In addition, a very excellent catalyst can be obtained.
[0025]
【The invention's effect】
As is apparent from the above description, according to the present invention, a method for producing a dimethyl ether synthesis catalyst capable of obtaining a homogeneous catalyst with good dispersibility of the catalytically active component, little uptake of impurities, and the production method can be obtained. A dimethyl ether synthesis catalyst is provided.
[Brief description of the drawings]
FIG. 1 Cu—Zn (36-4 wt%) / Al ₂ O ₃ (sol-gel) catalyst (Example 1) and Cu—Zn (25-25 wt%) / Al ₂ O ₃ (commercially available) catalyst It is a graph which shows the DME production amount with respect to the reaction temperature of (Comparative Example 1).
FIG. 2 is a graph showing the amount of DME produced with respect to the reaction time of a Cu—Zn (36-4 wt%) / Al ₂ O ₃ (sol-gel) catalyst (Example 1).

Claims (3)

In a method for producing a dimethyl ether synthesis catalyst for synthesizing dimethyl ether from carbon monoxide and hydrogen,
Obtaining a dispersion of metal alkoxide;
Adding an acid to the dispersion to hydrolyze the metal alkoxide to form a sol;
A step of adding Cu and Zn used as catalytic active components as an aqueous solution to the sol obtained in the step of solification;
Evaporating and drying the sol solution to obtain a gel;
A method for producing a dimethyl ether synthesis catalyst, comprising: drying, calcining, and hydrogen reduction to obtain a DME synthesis catalyst, and producing a dimethyl ether synthesis catalyst by a sol-gel method.   The method for producing a dimethyl ether synthesis catalyst according to claim 1, wherein the metal alkoxide is an aluminum alkoxide.   The dimethyl ether synthesis according to claim 1 or 2, characterized in that it contains 5 to 60% by weight of Cu and Zn as catalytic active components, and Cu / Zn is in the range of 100/0 to 40/60 by weight ratio. A dimethyl ether synthesis catalyst produced by a method for producing a catalyst.

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