JP2004345972A - Method for producing carboxylic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carboxylic ester, comprising reacting an alcohol with the same alcohol or reacting the alcohol with an aldehyde in the presence of oxygen, by which a high aldehyde or alcohol conversion and a high carboxylic ester selectivity can be realized. <P>SOLUTION: This method for producing the carboxylic ester, comprising reacting the alcohol with the same alcohol and oxygen or reacting the alcohol with the aldehyde and the oxygen in the presence of a solid catalyst, is characterized in that the absolute electric charge value of the solid catalyst in a powder state is &le;1 kV measured by a specific method. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a carboxylic acid ester by reacting alcohols with each other or an aldehyde and an alcohol in the presence of oxygen, and provides a method for producing a high aldehyde or alcohol conversion and a high carboxylic acid ester selectivity.
[0002]
[Prior art]
The reaction of synthesizing a carboxylic acid ester from two molecules of alcohol and oxygen using a palladium / activated carbon catalyst originated in 1968 by a research conducted by Prof. Katsuto of the University of Tokyo (Non-Patent Document 1). Prior to this study, in the 1960s, Russia's Moiseev et al. Devised the synthesis of acetaldehyde by the dehydrogenation of ethanol using a palladium chloride catalyst. He was studying ester synthesis from alcohol and oxygen. The group of Prof. Katsuto and others has evolved into the reaction between alcohols, and even the reaction between aldehydes and alcohols, and has dramatically increased the industrial utility of the reaction system, which has been a subject of academic interest.
[0003]
On the other hand, as a method for producing industrially useful methyl methacrylate or methyl acrylate, an oxidative esterification method of directly reacting methacrolein or acrolein with methanol to produce methyl methacrylate or methyl acrylate has been proposed. ing. This production method is performed by reacting methacrolein or acrolein with molecular oxygen in methanol, and examples using a catalyst containing palladium and lead, bismuth, thallium, and mercury are known (Patent Documents 1 to 4). . Further, an example is disclosed in which an intermetallic compound of palladium and these metals is used as a catalyst (Patent Document 5). Further, a catalyst using palladium and bismuth is disclosed (for example, Patent Document 6), and a catalyst using ruthenium and lead is known (Patent Document 7). Also, a catalyst using gold has been disclosed (Patent Documents 8 and 9).
[0004]
All the catalysts shown in these disclosure examples are solid catalysts supported on carriers such as calcium carbonate, silica, and alumina. The reaction is performed by dispersing these solid catalysts in a solution of an alcohol and an aldehyde (hereinafter, referred to as “catalyst”). This is generally performed by blowing a gas containing oxygen (which may be abbreviated as a catalyst slurry in some cases), and the present inventors also used a bubble column reactor to convert a gas containing oxygen into a slurry of methacrolein, methanol, and a solid catalyst. Has been continuously conducted over a long period of time to produce methyl methacrylate. However, in spite of using the solid catalyst produced by the same preparation method, there are cases where high aldehyde or alcohol conversion and high carboxylate ester selectivity are exhibited or not, and the reproducibility of the solid catalyst preparation method is increased. It was a big problem for industrialization.
[0005]
Therefore, the inventors of the present invention have compared solid catalysts having excellent catalytic performance with solid catalysts having poor catalytic performance. As a result, it has been found that the solid catalyst having excellent catalytic performance has a small charge amount. However, although the charge amount should be small, the solid catalyst used in the present invention is a metal catalyst, and it is inevitable that the solid catalyst is more or less charged with static electricity. However, in order to carry out the reaction with good reproducibility, it was a problem that had to be solved without fail.
[0006]
[Non-patent document 1]
Togiko Industrial Chemistry Magazine (1968), 71, p. 1517
[Patent Document 1]
JP-B-57-35856 [Patent Document 2]
JP-B-57-35857 [Patent Document 3]
Japanese Patent Publication No. 57-35858 [Patent Document 4]
JP-B-57-35859 [Patent Document 5]
Japanese Patent Publication No. 62-7902 [Patent Document 6]
JP-A-9-216850 [Patent Document 7]
JP 2001-220367 A [Patent Document 8]
JP 2000-156164 A [Patent Document 9]
JP-A-2002-361086
[Problems to be solved by the invention]
The present invention relates to a method for producing a carboxylic acid ester by reacting alcohols with each other or an aldehyde and an alcohol in the presence of oxygen, and provides a method for producing a high aldehyde or alcohol conversion and a high carboxylic acid ester selectivity.
[0008]
[Means for Solving the Problems]
As a result of intensive studies by the present inventors, it has been found that, even with a solid catalyst produced by the same preparation method, the difference in the amount of charge defined in the following description has a great effect on the catalyst performance, and the starting point of the present invention was obtained.
It is unclear how the charge amount of the solid catalyst as a powder affects the catalyst performance. It is considered that the charge amount of the solid catalyst is largely related to the hydrophilicity and hydrophobicity of the surface of the solid catalyst. For example, as shown in JP-A-11-43456, in the hydration reaction of olefins, solid catalyst particles are suspended in a reaction substrate and a gas is blown into the suspension in the same manner as in the present reaction system. It is said that a solid catalyst having a small charge amount, that is, a solid catalyst having a hydrophilic surface is preferable. In this reaction system, since the reaction substrate is water, a solid catalyst having a small charge amount and a hydrophilic surface is considered to be preferable.
[0009]
However, as shown in JP-A-5-148184, the reaction system of the present invention has a water-inhibiting effect, so that a solid catalyst having a hydrophobic surface, that is, JP-A-11-43456. According to the interpretation of the publication, a solid catalyst having a large charge amount should have been a preferable reaction. Nevertheless, the smaller the charge amount, the better the catalytic performance is, which is a completely opposite tendency to the known facts known so far in this reaction system and similar reaction systems. Yes, the present inventors have found out a fact that could not be expected, and completed the present invention.
[0010]
That is, the present invention
1. When reacting alcohols or aldehydes and alcohols with a solid catalyst in the presence of oxygen to produce a carboxylic acid ester, the charge amount A of the solid catalyst in a powder state is measured by the method described in the specification. The present invention relates to a method for producing a carboxylic acid ester, wherein an absolute value of 1 kV or less is used.
2. (1) The solid catalyst as described in (1) above, wherein the solid catalyst contains at least one selected from palladium, ruthenium, and gold. The present invention relates to a method for producing the carboxylic ester described in the above.
3. The above-mentioned 1., wherein the alcohol is methanol and / or ethanol and the aldehyde is acrolein or methacrolein. And 2. The present invention relates to a method for producing the carboxylic acid ester described in the above.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The aldehyde used in the present invention includes, for example, aliphatic saturated aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde and glyoxal; aliphatic unsaturated aldehydes such as acrolein, methacrolein and crotonaldehyde; benzaldehyde, tolylaldehyde, benzyl Aromatic aldehydes such as aldehydes and phthalaldehyde; and derivatives of these aldehydes. These aldehydes can be used alone or as a mixture of two or more kinds. In particular, acrolein and methacrolein are preferably used.
[0012]
Examples of the alcohol used in the present invention include aliphatic saturated alcohols such as methanol, ethanol, isopropanol and octanol; diols such as ethylene glycol and butanediol; aliphatic unsaturated alcohols such as allyl alcohol and methallyl alcohol; And aromatic alcohols such as alcohols. Particularly, lower alcohols such as methyl alcohol and ethyl alcohol are preferable because the reaction is rapid. These alcohols can be used alone or as a mixture of two or more kinds.
[0013]
The ratio of the amount of aldehyde to the amount of alcohol used in the reaction of the present invention is not particularly limited, and the reaction can be carried out in a wide range, for example, in a molar ratio of aldehyde / alcohol of 10 to 1/1000. Preferably, it is set in the range of 1/2 to 1/50.
The oxygen used in the present invention may be molecular oxygen, that is, oxygen gas itself or a mixed gas obtained by diluting oxygen gas with a diluent inert to the reaction, for example, nitrogen or carbon dioxide gas, and using air. You can also. The amount of oxygen to be present in the reaction system is not less than the stoichiometric amount necessary for the reaction, that is, at a preferable condition of a molar ratio of aldehyde / alcohol of か ら to 1/50, １ ／ mole or more to aldehyde. Oxygen. Preferably, at least 1.2 times the stoichiometric amount of oxygen is sufficient.
[0014]
Although the total pressure of the reaction can be carried out in a wide range of pressure from reduced pressure to increased pressure, it is usually carried out at a pressure of 1 to ²⁰ kg / cm ² . The partial pressure of oxygen supplied to the reaction system is preferably controlled so that the oxygen partial pressure at the outlet of the reactor is 0.8 kg / cm ² or less, more preferably 0.4 kg / cm ² or less. On the other hand, the total pressure may be set so that the oxygen concentration of the gas discharged from the reactor does not exceed the explosion range (8%). The reaction of the present invention can be carried out by any conventionally known method such as a gas phase reaction, a liquid phase reaction, and a perfusion reaction. For example, when the reaction is carried out in a liquid phase, any reactor type such as a bubble column reactor, a draft tube reactor, a stirred tank reactor, etc. can be used. The reactor can be of any type known in the art, such as a fixed bed type, a fluidized bed type, or a stirred tank type.
[0015]
The reaction can be carried out without a solvent, but can be carried out using a solvent inert to the reaction components, for example, hexane, decane, benzene, dioxane and the like. The solid catalyst used in the present invention preferably contains at least one selected from palladium, ruthenium, and gold, and contains X (X is at least one metal selected from lead, bismuth, mercury, and thallium). Is also good. Palladium, ruthenium, gold and X may form an alloy or an intermetallic compound.
[0016]
Further, the solid catalyst used in the present invention includes Fe, Te, Ni, Cr, Co, Cd, In, Ta, Cu, Zn, Zr, Hf, W, Mn, As, Ag, Re, Sb, and Sn as different elements. , Rh, Ir, Pt, Ti, Al, B, Si, Ge, Se, Ta, and the like. These different elements can be expected to have favorable effects such as increasing the selectivity of the carboxylic acid ester. These different elements can usually be contained in an amount not exceeding 5% by weight, preferably not exceeding 1% by weight, based on the total weight of the catalyst. Hereinafter, in the present invention, the weight% indicates a value when the total weight of the catalyst is 100% by weight.
[0017]
Further, those containing at least one member selected from an alkali metal compound and an alkaline earth metal compound have the advantage that the reaction activity is increased. The alkali metal and alkaline earth metal are usually selected from the range of 0.01 to 30% by weight, preferably 0.01 to 5% by weight.
These dissimilar elements, alkali metals, alkaline earth metal compounds, and the like may penetrate a small amount between crystal lattices, or may be substituted for some of the crystal lattice metals. Further, the alkali metal and / or alkaline earth metal compound may be added to a solution containing a palladium compound, a ruthenium compound, a gold compound or a compound of X at the time of preparation of the solid catalyst, and may be adsorbed or adhered to a carrier. A solid catalyst can also be prepared using a carrier carrying the compound. It is also possible to add to the reaction system under the reaction conditions.
[0018]
These solid catalyst components may be present in the reaction system alone in the form of fine metal particles without being supported on a carrier or the like, or silica, alumina, silica alumina, titanium, carbonate, hydroxide, Those supported on carriers such as activated carbon and zirconia may also be used.
The supported amount of the palladium, ruthenium, and gold supported catalyst in the present invention is not particularly limited, but is usually 0.1 to 20% by weight, preferably 1 to 10% by weight. When used, the loading amount is usually 0.01 to 30% by weight, preferably 0.01 to 15% by weight.
[0019]
The solid catalyst of the present invention can be prepared by a known preparation method. A typical method for preparing a solid catalyst will be described. For example, a carrier is added to an aqueous solution containing a soluble lead compound and a soluble palladium salt such as palladium chloride, followed by heating and impregnation to impregnate palladium and lead. Next, reduction is carried out with formalin, formic acid, hydrazine or hydrogen gas. As shown in this example, lead may be loaded before loading palladium, or palladium and lead may be loaded simultaneously.
[0020]
Palladium compounds, ruthenium compounds, gold compounds used for the preparation of the solid catalyst include, for example, organic acid salts such as formate and acetate, sulfates, hydrochlorides, inorganic acid salts such as nitrates, ammine complexes, benzonitrile complexes, An acetylacetonate complex, an organometallic complex such as a carbonyl complex, an oxide, a hydroxide or the like are appropriately selected.As the palladium compound, palladium chloride, palladium acetate, and the like, and as the ruthenium compound, ruthenium chloride and the like are used. As the compound, chloroauric acid is preferred.
[0021]
As the compound of X, inorganic salts such as nitrates and acetates, and organic metal complexes such as phosphine complexes can be used, and nitrates and acetates are preferable.
The alkali metal compound and alkaline earth metal compound are also selected from organic acid salts, inorganic acid salts, hydroxides and the like.
The amount of the solid catalyst used can be largely changed depending on the type of the reaction raw material, the composition and the preparation method of the solid catalyst, the reaction conditions, the reaction type, and the like, and is not particularly limited, but the solid catalyst is reacted in a slurry state. In this case, it is preferable to use 0.04 to 0.5 kg per liter of the reaction solution.
[0022]
In the reaction of the present invention, an alkali metal or alkaline earth metal compound (eg, oxide, hydroxide, carbonate, carboxylate, etc.) is added to the reaction system to maintain the pH of the reaction system at 6 to 9. Is preferred. In particular, setting the pH to 6 or more has an effect of preventing the dissolution of the X component in the solid catalyst. These alkali metal or alkaline earth metal compounds can be used alone or in combination of two or more.
The reaction of the present invention can be carried out at a high temperature of 100 ° C or higher, but preferably 30 to 100 ° C, more preferably 60 to 90 ° C.
[0023]
The reaction time is not particularly limited and cannot be uniquely determined because it varies depending on the set conditions, but is usually 1 to 20 hours.
In the present invention, it is essential that the absolute value of the charge amount A when the solid catalyst is measured in a powder state by a predetermined method described below is 1 kV or less. The upper limit of the charge amount A is 1 kV, preferably 0.1 kV or less. When the absolute value of the charge amount A exceeds 1 kV, excellent catalytic performance is not exhibited, which is not preferable.
[0024]
In particular, in the case of a solid catalyst supporting palladium, palladium exhibits paramagnetism, so that it is easily charged, and it is preferable to take multiple danger predictions and take precautions.
It is well known that the human body is charged with static electricity in the dry winter season, etc., but the critical charging voltage in this case is said to be about 1.4 kV (High Pressure Gas Safety Association, edited by High Pressure Gas Security Technology, revised in 1989) 362), the upper limit of the charge amount A of the present invention can easily put the solid catalyst in an unfavorable state if carelessly neglects. As shown below, it is important to prevent the operator's clothing from being charged, remove the discharge to the ground with safety shoes, and ground and bond the operating plant.
[0025]
The inventors of the present invention still do not know what relationship exists between the charge amount A of the solid catalyst and the catalyst performance, and as described in the section of the related art, a result different from the known fact in the technical field is obtained. ing. That is, the charge amount of the solid catalyst in a powder state shows a large charge amount when the surface of the solid catalyst is hydrophobic, and shows a small charge amount when the surface of the solid catalyst is hydrophilic. The reason why the surface of the solid catalyst becomes hydrophobic is that the hydrophilic group on the outer surface is lost, and in the case of the hydrophobic solid catalyst preferred for the present reaction, the charge amount should be large. Is a solid catalyst having a small charge amount. Therefore, it is impossible to explain the present invention in terms of the effect of water. In the present invention, rather, even if the solid catalyst surface is hydrophilic, the balance between the adsorption and desorption of the reaction substrate and the product becomes more favorable for the present reaction, and water that will collect on the hydrophilic surface will be more favorable. It is presumed that they exert an excellent reaction promoting effect that is much more than the inhibitory effect.
[0026]
The state of the solid catalyst is not particularly limited as long as the solid catalyst is in a powder state. It is defined as a state in which a liquid such as a reaction liquid is not substantially contained and a slurry is not formed by a raw material alcohol or the like. For example, a solid catalyst before a slurry to be supplied to the reactor, a solid catalyst after a drying operation in a solid catalyst production and regeneration step, and the like can be exemplified.
The charge amount A specified in the present invention is measured by the following measuring method, and various other measuring methods are generally known. Specifically, a method using a principle such as a current collecting type, a rotary chopper type, a diaphragm type or the like, which can be measured in a non-contact state, can be used. As a specific measuring method, a method specified by a measuring instrument to be used is used.
In the range examined by the present inventors, there is no standard that stipulates a method for measuring the amount or potential of the solid catalyst powder, and the results are measured by a specified method of each measuring device. Will be compared.
[0027]
In the present invention, the solid catalyst to be measured has a thickness of 2 cm in a stainless steel dish that is not grounded in a 50% humidity atmosphere using a digital electrostatic meter KSD-0108 manufactured by Kasuga Electric Co., Ltd. As evenly spread as possible, by the potential measuring device of the main body detecting unit, so that the potential is measured correctly, the measurement distance 50 mm determined by the measuring device, between the solid catalyst to be measured and the potential detecting unit, At the same time, the electric charge is measured by reading the indicated value of the potential measuring instrument 5 seconds after the start of the measurement so that the surface of the tip of the probe is parallel to the surface of the solid catalyst to be measured. The surface of the solid catalyst with respect to the measurement surface of the detection unit needs to be made sufficiently wide. However, the condition in which the measurement can be performed by adjusting the above measurement conditions is set within 30 seconds, and the measurement is performed 30 seconds later. The grounding curl cord must be grounded. Further, it is necessary to have a condition that dew condensation does not occur at a humidity of 50%.
[0028]
In the present invention, as a method for setting the charge amount A of the solid catalyst to 1 kV or less, usually, a solid catalyst in an uncharged state is used as a raw material, and the solid catalyst is handled in an uncharged or hardly charged device. No.
It is also effective to remove the charge from the already charged solid catalyst particles. Examples of the method for removing the electric charge include grounding the device, performing bonding, setting the standing time on the conductor, and applying humidity.
The method of suppressing charging of the solid catalyst particles is also important in the present invention, and examples thereof include limiting the flow rate during handling and transfer of the solid catalyst particles, and suppressing contact and collision between the solid catalyst particles.
[0029]
【Example】
Hereinafter, embodiments of the present invention will be specifically described with reference to examples.
As a carrier, 3750 g of a solid catalyst having 5% by weight of palladium, 5% by weight of lead, and 4% by weight of magnesium supported on silica gel (Carrierct 10 (registered trademark) average particle size of 50 μm) manufactured by Fuji Silysia Ltd. , And 34 wt% of methacrolein / methanol were supplied at 1.35 l / h and NaOH / methanol at 0.15 l / h, at a temperature of 80 ° C and a pressure of 5. The reaction was performed while supplying air at 0 kg / cm ² .
[0030]
The NaOH concentration was adjusted so that the pH of the reaction solution was 7.1, and lead acetate was dissolved in methacrolein / methanol and supplied continuously so that the lead concentration in the feed solution was 20 ppm.
On the other hand, air was supplied to the reactor while adjusting the amount of air so that the oxygen concentration at the reactor outlet was 4% (oxygen partial pressure 0.20 kg / cm ² ).
The conversion rate of unsaturated aldehyde and selectivity of unsaturated carboxylic acid ester were evaluated as follows.
The reaction solution and the gas at the outlet of the reactor were analyzed by a normal gas chromatogram method, using a GC-8A machine manufactured by Shimadzu Corporation with a G-100 column manufactured by the Chemical Inspection Association (eluting almost in the order of boiling points), and a thermostat. Was heated using a hydrogen flame detector (FID).
[0031]
Embodiment 1
The solid catalyst was left in the air of 50% humidity for 5 hours and then subjected to the reaction. The charge amount A by the digital electrostatic meter KSD-0108 (produced by Kasuga Electric Co., Ltd.) described in the specification was zero.
Six hours after the start of the reaction, the reaction results obtained were a conversion of methacrolein of 61% and a selectivity of methyl methacrylate of 90%.
[0032]
[Comparative Example 1]
The solid catalyst was dried overnight at 60 ° C. in a vacuum dryer, and then subjected to a reaction without performing any demagnetizing operation or grounding operation. When the charge amount A of the solid catalyst particles was measured in the same manner as in Example 1, it was -1.3 kV.
Six hours after the start of the reaction, the reaction results obtained were a conversion of methacrolein of 41% and a selectivity of methyl methacrylate of 70%.
[0033]
【The invention's effect】
The production method of the present invention relates to a method for producing a carboxylic acid ester by reacting alcohols with each other or an aldehyde and an alcohol in the presence of oxygen. The nature is high.

Claims (3)

When the carboxylic acid ester is produced by reacting alcohols or aldehydes and alcohols with a solid catalyst in the presence of oxygen, the solid catalyst is required to have a charge amount A in a powder state of 1 kV or less in absolute value. A method for producing a carboxylic acid ester, which is used. The method for producing a carboxylate according to claim 1, wherein the solid catalyst is a solid catalyst containing at least one selected from palladium, ruthenium, and gold. 3. The solid catalyst and method according to claim 1, wherein the alcohol is methanol and / or ethanol and the aldehyde is acrolein or methacrolein.