JP2006212571A - Method for suppressing deterioration of au catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To locate a cause of performance deterioration of an Au catalyst in which if the Au catalyst is used, a reaction such as, for example, oxygen oxidation of an alcohol, progresses efficiently, but when it is scaled up to a practical operation level, reaction efficiency such as a raw material conversion rate and a selection rate to an object material is deteriorated relatively in a short time; and to find a method for suppressing such the performance deterioration. <P>SOLUTION: When a liquid phase reaction is carried out using the Au catalyst, to suppress the poisoning of the Au catalyst by Fe, the method for suppressing the deterioration of the Au catalyst makes present a metal element of one kind or more selected from the group consisting of a group 7A, a group 8 excluding Fe, a group 1B excluding Au, a group 2B, a group 3B and a group 4B in a reaction system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing deterioration of an Au catalyst used in, for example, a reaction of oxidizing alcohol with oxygen by poisoning with Fe.

The applicant of the present application has found that a reaction such as oxygen oxidation of alcohol proceeds efficiently by using an Au catalyst, and has already filed numerous applications (for example, Patent Document 1). However, while conducting various studies using the Au catalyst, it has been found that the reaction efficiency, that is, the raw material conversion rate and the selectivity to the target product are reduced in a relatively short period of time. It became necessary to find out the cause. The applicant of the present application has found that the deterioration of the Au catalyst over time is suppressed by the addition of a basic compound, and this knowledge has already been filed. Cannot be suppressed, and the mechanism of poisoning is considered to be different.
JP 2003-93876 A JP 2004-137180 A

  In the case of an expensive catalyst such as an Au catalyst, replacement with a new catalyst every time performance deteriorates greatly affects the product cost. Accordingly, the present inventors have raised the problem of finding out the cause of the performance deterioration of the Au catalyst and finding a method for suppressing such performance deterioration.

  The Au catalyst deterioration suppressing method of the present invention that has been able to solve the above-mentioned problems is that, in performing a liquid phase reaction using an Au catalyst, in order to suppress poisoning of the Au catalyst by Fe, The gist is that one or more metal elements selected from the group consisting of Group 8 except Fe, Group 1B, Group 2B, Group 3B, and Group 4B except Au are present. The metal element is present in the reaction system in a state of being supported on the support together with Au, and that the liquid phase reaction is a reaction between one or more alcohols and oxygen. This is a preferred embodiment of the present invention.

  According to the present invention, the deterioration of the Au catalyst over time can be suppressed, so that the replacement frequency of the expensive catalyst can be reduced, and the target product can be produced at a low cost.

  As a result of the inventors pursuing the cause of the deterioration of the Au catalyst over time, Fe elutes from the stainless steel used in the reactor and distillation equipment, and this is adsorbed and accumulated on the Au catalyst. It was found that the activity deteriorated. That is, when an experiment was conducted in which Fe ions were positively added to the reaction system, it was confirmed that the catalyst deteriorated. It was also confirmed that such catalyst deterioration did not occur in Ni, Cr, Mo, etc. contained in stainless steel. The poisoning of the catalyst by Fe has become more prominent when, for example, a part of the raw material alcohol is circulated when the alcohol is oxidized with oxygen.

  Since the cause of poisoning of the Au catalyst has been found, the present inventors have conducted further studies and found that this deterioration phenomenon can be suppressed by the presence of a specific metal element in the reaction system, and the present invention has been reached. did. Hereinafter, the present invention will be described in detail.

  In the present invention, it is assumed that the reaction is a liquid phase reaction using an Au catalyst. Examples of the form of the liquid phase reaction include a form in which the reaction raw material is liquid and does not contain a solvent, and the reaction raw material may be any of gas, liquid, and solid, but a form in which a liquid phase reaction is performed using a solvent. In particular, the production method in which the reaction raw material is liquid and the unreacted raw material is reused (circulated), that is, the reaction product and the unreacted raw material are separated by a distillation means and then used again as the reaction raw material. When it is adopted, accumulation of Fe in the catalyst becomes remarkable, and the significance of adopting the method of the present invention is great, which is preferable.

  Examples of liquid phase reactions that can be carried out using an Au catalyst include (1) a carboxylic acid ester synthesis reaction using one or more alcohols and oxygen, (2) a carboxylic acid ester synthesis reaction using an aldehyde compound and an alcohol, (3 ) A synthetic reaction in which an alkyl substituent of an aromatic compound having an alkyl substituent is oxidized to an aldehyde group or a ketone group, and (4) a synthetic reaction of an aromatic carboxylic acid ester by an aromatic compound having an alkyl substituent and an alcohol. These are all oxidation reactions using oxygen.

  The alcohol that can be used in the above carboxylic acid ester synthesis reaction (1) may be a monohydric alcohol or a polyhydric alcohol. The alcohol is preferably a primary alcohol, and in the case of a polyhydric alcohol, it preferably contains one or more primary alcohols in the molecule. Specifically, C1-C10 aliphatic alcohols such as methanol, ethanol, n-propanol, and octanol; ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol Diols having 2 to 10 carbon atoms such as C2-10 alcohols having an ether bond in the molecule such as diethylene glycol and triethylene glycol.

  Specific examples of the synthesis reaction of (1) include synthesis of ethyl acetate from ethanol, synthesis of 2-hydroxyethyl hydroxyacetate from ethylene glycol, synthesis of 1,4-dioxane-2-one from diethylene glycol, ethylene glycol Synthesis of methyl glycolate from methanol and methanol, synthesis of methyl pyruvate and methyl lactate from propylene glycol and methanol, synthesis of ε-caprolactone from 1,6-hexanediol, and the like.

  In these reactions, the alcohol used can be used in excess as a solvent. In addition, water; ethers such as diethyl ether, diisopropyl ether, and dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and known solvents such as aromatic hydrocarbons such as toluene, xylene, and benzene You can also. These reactions are usually carried out at 0 to 180 ° C. and 0.05 to 2 MPa (gauge pressure).

  As the aldehyde compound in the reaction of synthesizing a carboxylic acid ester from the aldehyde compound (2) and an alcohol, an aliphatic aldehyde having 1 to 10 carbon atoms such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, glyoxal, pyruvic aldehyde; Α, β-unsaturated aldehydes having 3 to 10 carbon atoms such as acrolein, methacrolein and crotonaldehyde; aromatic aldehydes having 6 to 20 carbon atoms such as benzaldehyde, phenylglyoxal, p-methoxybenzaldehyde, tolualdehyde and phthalaldehyde In addition to these, derivatives of these aldehydes can be mentioned. Although alcohol is not specifically limited, A C1-C10 aliphatic alcohol is preferable.

  Specific examples of the reaction for oxidizing the alkyl substituent of the aromatic compound (3) to an aldehyde group include synthesis of benzaldehyde from toluene, synthesis of salicylaldehyde from o-cresol, and p-hydroxy from p-cresol. Examples include synthesis of benzaldehyde, synthesis of acetophenone from ethylbenzene, synthesis of ethylphenylketone from n-propylbenzene, synthesis of diphenylketone from diphenylmethane, and the like. These reactions include ethers such as diethyl ether, diisopropyl ether, methyl-t-butyl ether and diethylene glycol diethyl ether; cyclic ethers such as 1,4-dioxane, 1,3-dioxane and 1,3-dioxolane; acetone, It is preferable to use an aprotic and highly polar solvent such as ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. A high yield is obtained. In addition, these reaction is normally performed at 0-300 degreeC and 0-5 MPa (gauge pressure).

  As a specific example of the aromatic carboxylic acid ester synthesis reaction (4) above, when various alcohols and alkylbenzenes such as toluene are used as raw materials, benzoic acid esters may be o-, m-, p-cresol, etc. When alkylphenols are used as raw materials, hydroxybenzoic acids are synthesized. When alkylnaphthalene such as 1- and 2-methylnaphthalene is used as raw materials, naphthoic acid esters are synthesized. In these reactions, an excessive amount of alcohol can be added and recycled. These reactions are usually carried out at 0 to 300 ° C. and 0 to 5 MPa (gauge pressure).

  The Au catalyst is not particularly limited as long as it is a catalyst having Au as an active component, but a catalyst in which Au is supported on a carrier is preferable. In particular, it is preferable that Au is supported as fine particles having an average particle diameter of 10 nm or less. The amount of Au supported on the carrier is preferably 0.1 to 30% by mass with respect to the carrier. This is because within this range, the catalyst performance is excellent and a catalyst excellent in cost can be obtained. A more preferable loading is in the range of 0.1 to 10% by mass.

  The carrier is not particularly limited as long as it can stably support Au fine particles and is excellent in physical and chemical durability under use conditions and can withstand long-term use. For example, (1) representative metal oxides such as silica, alumina, titania, zirconia, and magnesia, (2) composite oxides such as silica-alumina, silica-titania, silica-zirconia, titania-zirconia, (3) Silica support on which various elements (for example, one or more elements selected from aluminum, titanium, zirconium, lanthanoids or actinoids) and their oxides are supported on a silica support, (4) Various on an alumina support (For example, one or more elements selected from silicon, titanium, zirconium, lanthanoids or actinoids) and oxides thereof, (5) ZSM-5, MCM-41, etc. And mesoporous silicate support having regular pores of (6) activated carbon, hula Ren, carbon materials such as carbon nanotubes, and the like are preferably used. Among these carriers, titania, zirconia, silica-titania, silica-zirconia, and those in which titania and zirconia are supported on a silica carrier can be particularly preferably used.

  Metal elements (poisoning suppression elements) that can prevent poisoning by Fe of Au catalyst are metal elements contained in 7A group, 8 group except Fe, 1B group, 2B group, 3B group and 4B group except Au It is 1 or more types. However, it is not clear why these elements suppress the accumulation of Fe in the Au catalyst.

  Specific examples of metal elements included in Group 7A are Mn, Tc, and Re. Group 8 elements other than Fe include Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt. The reason why Fe is removed from the Group 8 element is because, of course, Fe is a cause of catalyst performance deterioration. Examples of the 1B group element other than Au include Cu and Ag. The reason why Au is removed from the group 1B element is that addition of Au to the Au catalyst does not lead to suppression of Fe poisoning. Examples of metal elements included in Group 2B include Zn, Cd, and Hg. Examples of the metal element included in Group 3B include AlGa, In, and Tl. Since B is non-metallic, it is not included. Examples of metal elements included in Group 4B include Ge, Sn, and Pb. C and Si are not included because they are non-metallic. Of these metal elements, Group 7A and Group 8 elements are preferable from the viewpoint of poisoning suppression ability, and among them, Mn, Ru, and Rh have high performance. Mn is most preferable from the viewpoint of availability, cost, poisoning suppression ability, global environment, and the like.

  The presence state of these poisoning suppression elements in the reaction system is not particularly limited. It may be present in an ionic state in the liquid phase, or may be supported on an Au catalyst. If the reaction system is present in an ionic state, it is considered that the phenomenon in which Fe is adsorbed on the Au catalyst and the phenomenon in which these poisoning suppression elements are adsorbed to inhibit the adsorption of Fe are competitive. Therefore, it is reliable to prevent poisoning by Fe by a method in which a poisoning suppression element is supported on an Au catalyst in advance, either of which may be used, or both of them may be used in combination.

  The compound used when the poisoning suppression element is present in an ion state in the reaction system is not particularly limited as long as it is a compound that can be dissolved in the liquid phase of the reaction system. Even when the reaction is carried out in an organic solvent having high hydrophobicity, it only needs to be dissolved slightly, and water is generated in the oxidation reaction using the Au catalyst, so that the application range of the water-soluble compound is wide. The water-soluble compounds include, for example, nitrates, sulfates, halides (chlorides, bromides, iodides), carboxylates (acetates, formates, etc.), acetylacetonate salts, ammines. And a complex, a phosphine complex, and the like. When the poisoning suppression element is present in the liquid phase in an ionic state, 1 to 1000 ppm (mass basis) is preferable. If it is this range, since the effect which suppresses the poisoning of the catalyst by Fe fully expresses and a metal element does not mix in a final product, it is preferable.

On the other hand, the method of supporting the poisoning suppression element on the Au catalyst is surely effective in preventing poisoning by Fe. The poisoning suppression element may be supported on the above-described carrier simultaneously with Au, before Au, or after Au. To support Au on the carrier, tetrachloroauric acid HAuCl ₄ , sodium tetrachloroaurate NaAuCl ₄ , potassium dicyanoaurate KAu (CN) ₂ , diethylamine gold trichloride (C ₂ H ₅ ) ₂ NH · AuCl ₃ An aqueous solution containing one or more gold cyanide AuCN or an alcohol solution such as methanol is used. The concentration is preferably about 0.1 to 10 mmol / L. In addition, when a poisoning suppression element is supported, an aqueous solution containing one or more of the above water-soluble compounds or an alcohol solution such as methanol is used. Also in this case, the concentration is preferably about 0.1 to 10 mmol / L. A carrier is added to these solutions (in the case of simultaneous loading, a solution containing both Au and a poisoning suppression element) to impregnate (or precipitate) a desired metal element, and then a drying process is performed as necessary. For example, by baking at about 200 to 700 ° C., an Au catalyst carrying a poisoning suppression element can be obtained. If necessary, a reduction treatment may be performed.

  When the poisoning suppression element is supported on the Au catalyst, the amount of the poisoning suppression element is preferably in the range of 0.01 to 10% by mass in 100% by mass of the catalyst. If it is this range, the poisoning suppression effect is fully exhibited, and there is no waste in cost. Note that the poisoning suppression element may be supported on a carrier other than the Au catalyst.

  The form of the liquid phase reaction using the Au catalyst in the present invention may be any of continuous type, batch type, semi-batch type, etc., and is not particularly limited. In the batch system, when the poisoning suppression element is present in the reaction system as ions, the Au catalyst and the above-mentioned water-soluble poisoning suppression element-containing compound are bundled together with the raw materials and, if necessary, the solvent in the reactor. It is good to prepare. In addition, when the poisoning suppression element is supported on the Au catalyst, the reaction apparatus may be charged first. On the other hand, in the continuous type, when the poisoning suppression element is present in the reaction system as ions, a method of adding it to the reaction system first and / or a method of continuously adding it can be adopted. Good. Further, when the poisoning suppression element is supported on the Au catalyst, a method of adding it to the reaction system first and / or a method of adding it continuously can also be adopted. The catalyst may be in any form such as a fixed bed, a fluidized bed, and a suspension bed. Although the usage-amount of Au catalyst is not specifically limited, About 0.01-5 mass parts is preferable with respect to 100 mass parts of reaction raw materials.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. In the following examples, “%” means “% by mass” unless otherwise specified.

Experiment 1
-Carrier preparation method 200 ml of 2-propanol solution in which 17.8 g of titanium isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 100 g of commercially available silica carrier powder (Fuji Silysia Chemical; "CARIACT Q-6") was added. After stirring well, titania was supported on the silica support by distilling off the solvent under heating. Then dried at 110 ° C. 10 hours, 4 hours at 600 ° C., and calcined in air, to obtain a TiO ₂ -SiO ₂ carrier.

-Preparation method of Au catalyst It neutralized with 14% sodium hydroxide, stirring 600 ml of gold chloride (III) acid aqueous solution with a density | concentration of 17 mmol / L, hold | maintaining at 65-70 degreeC. Here, 20 g of the TiO ₂ —SiO ₂ carrier was added, and stirring was continued for another hour while maintaining the pH in the system at 6.5 to 6.9. Then, solid content was separated by filtration and washing with 80 ml of water was repeated 5 times. Subsequently, it was dried at 120 ° C. for 6 hours and calcined in the air at 400 ° C. for 3 hours to obtain an Au catalyst (Au / TiO ₂ / SiO ₂ ) in which Au was supported on a TiO ₂ —SiO ₂ carrier.

-Preparation method of Au catalyst supporting Mn (Part 1)
While stirring 600 ml of a gold chloride (III) acid aqueous solution having a concentration of 17 mmol / L while maintaining at 65 to 70 ° C., the solution was neutralized with 14% sodium hydroxide. To this, 20 g of the above TiO ₂ —SiO ₂ carrier was added and stirred for 5 minutes, and then 0.43 g of acetic acid (II) manganese tetrahydrate was added and stirred for 1 hour. During this time, the pH in the system was in the range of 7.2 to 7.3. Thereafter, Au was supported in the same manner as described above to obtain an Au catalyst supporting Mn (Mn—Au / TiO ₂ / SiO ₂ ).

-Continuous experiment method 1.15 mol of ethylene glycol, 5.75 mol of methanol and 9.55 g of the above Au catalyst were added to a stainless steel continuous reaction vessel (volume: 500 ml), and methyl glycolate (MGC) by oxygen oxidation was added. A continuous synthesis experiment was conducted. In this reaction, MGC is mainly produced, 2-hydroxyethyl glycolate (HEGC) is produced as a by-product although it is a by-product, and dimethyl oxalate (DMO) is produced as an undesirable by-product. The synthesis reaction was performed at 110 ° C. under a pressure of 1 MPa while feeding air at 95 ml / min (2 to 3 mol% in terms of oxygen). In this system, the product is discharged while supplying the raw material (a mixture of 1.15 mol of ethylene glycol and 5.75 mol of methanol) so that the residence time is 8 hours. As shown in Table 1, instead of supplying a mixture of ethylene glycol and methanol as a raw material after 123 hours had elapsed after the start of the reaction, a mixture of iron (II) acetylacetonate, ethylene glycol and methanol was placed in a container. It supplied so that Fe might be 1 ppm (mass reference | standard) with respect to the inside reaction liquid.

  Table 1 shows the conversion rate (%) of ethylene glycol (EG), the selectivity (%) of MGC, HEGC and DMO, and the yield (%) of MGC, HEGC and DMO. The selectivity is the mol% of the target compound when the reaction product generated by the conversion of EG is 100 mol%, and the value obtained by multiplying the conversion rate and the yield is the yield (mol%) of the target compound. ). Each compound in the sample was quantified by gas chromatography. The reaction time and the yield of MGC are shown in FIG.

  In the same manner as described above, a continuous synthesis experiment was performed using an Au catalyst supporting Mn. In this example, a mixture of iron (II) acetylacetonate, ethylene glycol, and methanol is used after 113 hours have elapsed from the start of the reaction so that Fe becomes 1 ppm (mass basis) with respect to the reaction solution in the container. Supplied. The results are shown in Table 2, and the MGC yield is also shown in FIG.

  As is apparent from Table 1 and FIG. 1, before adding Fe, in the case of an Au catalyst not containing Mn (● in FIG. 1) and in the case of using an Au catalyst supporting Mn (♦ in FIG. 1) In MGC yield, there is not much difference, but when Fe is added, in the case of Au catalyst without Mn, the yield dropped to 19.6% in 19 hours after Fe addition, When an Au catalyst supporting Mn is used, the yield is finally 20.0% when 361 hours have elapsed after the addition of Fe. That is, it was confirmed that Mn suppressed poisoning by Fe and maintained the catalytic ability at a high level for a long time.

  Separately, all the Fe accumulated on the catalyst was eluted into aqua regia, and the amount of Fe was quantified by ICP (inductively coupled plasma) emission spectrometry. As a result, in the case of the Au catalyst not having Mn, the Fe concentration in the catalyst was 143 ppm in the reaction time of 101 hours, whereas in the case of the Au catalyst supporting Mn, the reaction time was 185 hours. The Fe concentration in the catalyst was as low as 60 ppm. From this value, the Fe adsorption rate (average value) is calculated to be 1.4 ppm / hour for an Au catalyst not having Mn, whereas 0.31 ppm / hour for an Au catalyst supporting Mn. Met. From these results, it is clear that the Au catalyst supporting Mn has an effect of suppressing poisoning by Fe, and this effect is because Fe is less likely to accumulate than an Au catalyst not having Mn. It was. That is, it is considered that suppressing accumulation of Fe on the catalyst led to suppression of poisoning.

Experiment 2 (Effect of each element)
As a result of the above continuous experiment, the correlation between the amount of accumulation (concentration) of Fe in the catalyst and the poisoning suppression effect by Fe has been clarified. The poisoning inhibitory effect of was examined.

-Preparation method of Au catalyst supporting Mn (Part 2)
To 5 g of the Au catalyst obtained by the preparation of the Au catalyst having no Mn as described above, 15 ml of methanol in which 0.1 g of manganese (II) acetate tetrahydrate was dissolved was added and stirred well. By distilling off the solvent, Mn was supported on the Au catalyst. Thereafter, the mixture was heated at 400 ° C. for 3 hours while feeding a mixed gas of hydrogen and nitrogen (volume ratio: hydrogen / nitrogen = 1/3) at 90 ml / min, and Au catalyst supporting Mn (Mn—Au / TiO 2). ₂ / SiO ₂ ).

-Preparation method of Au catalyst supporting other elements In the same manner as the preparation method of Mn-supported Au catalyst (Part 2) except that the following compound was used instead of 0.1 g of manganese acetate tetrahydrate. Thus, each catalyst was manufactured. The concentration of each element in the catalyst is all 0.5%.

Cr: Chromium (III) acetylacetonate: 0.5 mmol
Co: Cobalt (III) acetylacetonate: 0.4 mmol
Ru ... ruthenium (III) acetylacetonate: 0.2 mmol
Rh ... rhodium (III) acetylacetonate: 0.2 mmol
Ir ... Iridium (III) acetylacetonate: 0.1 mmol
Cu: Copper (II) acetylacetonate: 0.4 mmol
Ag ... silver acetate (I): 0.2 mmol
Pb: Lead acetate (II): 0.1 mmol
In a batch-type experiment, 1 g of catalyst, 3.8 g of ethylene glycol, 9.9 g of methanol, and 26 mg of iron (II) acetylacetonate were placed in a 100 ml autoclave and sealed, and then nitrogen was added at 0.3 MPa, oxygen Was stirred at 110 ° C. for 2 hours while pressure was added at 0.3 to 0.4 MPa. After the batch experiment, the amount of Fe accumulated in the catalyst was quantified in the same manner as in the continuous reaction, and the increase (mass%) of Fe is shown in Table 3.

  In the Au catalyst (No. 3 to 10) carrying the metal element defined in the present invention, the value is lower than the Fe accumulation amount of the Au catalyst (No. 1), and the effect of preventing the poisoning of Fe is exhibited. It could be confirmed. On the other hand, it was confirmed that the Au catalyst (No. 2) on which Cr outside the scope of the present invention was supported was larger than the Fe accumulation amount of the Au catalyst, and there was no effect of preventing the poisoning of Fe.

  According to the method for inhibiting deterioration of an Au catalyst of the present invention, for example, an Au catalyst effective for an oxygen oxidation reaction such as alcohol can be poisoned by Fe eluted from the reaction equipment, and the rate at which the catalyst performance deteriorates can be significantly reduced. When the target product is synthesized using an Au catalyst at an industrial production level, it has become possible to stably operate at a low cost.

It is a graph which shows the influence of Fe which acts on the yield of methyl glycolate (MGC).

Claims (3)

  In performing liquid phase reaction using Au catalyst, in order to suppress poisoning of Au catalyst by Fe, 7A group, 8 group except Fe, 1B group except Au, 2B group, 3B group and 4B A method for inhibiting deterioration of an Au catalyst, wherein one or more metal elements selected from the group consisting of a group are present.   The method for suppressing deterioration of an Au catalyst according to claim 1, wherein the metal element is present in the reaction system in a state of being supported on the support together with Au. The method for inhibiting deterioration of an Au catalyst according to claim 1, wherein the liquid phase reaction is a reaction of one or more alcohols with oxygen.

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