JP5479939B2 - Process for producing α, β-unsaturated carboxylic acid - Google Patents

Description

  The present invention relates to a process for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of an alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen in the presence of a catalyst containing palladium and tellurium.

  As a method for producing α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin with molecular oxygen, palladium metal or an intermetallic compound of palladium metal and other metals (lead, bismuth, thallium, mercury, etc.) A method using a palladium catalyst composed of a low-order oxidation state compound is known (Patent Document 1). The method described in Patent Document 1 oxidizes an olefin in the presence of an aqueous solution of at least one molybdenum compound selected from the group consisting of molybdenum oxides, heteropolymolybdic acid and heteropolymolybdate, and the palladium catalyst. It is characterized by that. Here, Patent Document 1 describes that “the amount of molybdenum compound to be used is not particularly limited, but an amount having a concentration in an aqueous solution of 0.1 g / l or more and a solubility in water or less is usually used”. The lower limit of 0.1 g / l is, for example, 69 ppm for molybdenum oxide anhydride, 59 ppm for molybdenum oxide hydrate, 49 ppm for silicomolybdic acid, 49 ppm for phosphomolybdic acid, etc. .

  In addition, as a method for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin with molecular oxygen, palladium containing 0.001 to 0.40 mol of tellurium metal with respect to 1.0 mol of palladium metal A method using a catalyst is known (Patent Document 2).

JP 56-59722 A International Publication No. 2005/118134 Pamphlet

  However, in the method described in Patent Document 1 or 2, the productivity and selectivity of the target product α, β-unsaturated carboxylic acid are greatly reduced when used for a long time, and the catalyst life is satisfactory. It wasn't. Thus, in the prior art, further improvement of the catalyst life has been desired. Moreover, it is preferable to have the same performance in the production of α, β-unsaturated carboxylic acid by liquid phase oxidation of alcohol or α, β-unsaturated aldehyde.

  Therefore, the present invention provides an α, β-unsaturated product which is the target product in the production of α, β-unsaturated carboxylic acid by liquid phase oxidation of alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen. It aims at stabilizing the catalyst life of saturated carboxylic acid (suppressing productivity and selectivity reduction).

The present invention is a process for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of an alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen in the presence of a catalyst containing palladium and tellurium. And supplying a molybdenum supply liquid containing the molybdenum compound in a dissolved and / or dispersed state and having a molybdenum element mass ratio of 1 mass ppm or more and 40 mass ppm or less into the reaction system for performing the liquid phase oxidation. In addition, the liquid phase oxidation is performed under the condition that the mass ratio of the molybdenum element present in the reaction system to the mass of the liquid present in the reaction system does not exceed 270 mass ppm. -A method for producing an unsaturated carboxylic acid.

  According to the present invention, when α, β-unsaturated carboxylic acid is produced by liquid phase oxidation of alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen, the target product α, β-unsaturated is produced. The catalyst life of the saturated carboxylic acid can be stabilized (inhibition of productivity and selectivity reduction).

It is a graph which shows the time-dependent change of methacrylic acid productivity in the reaction evaluation of Examples 1-5 and Comparative Examples 1-6. It is a graph which shows the time-dependent change of the selectivity total of methacrolein, methacrylic acid, and methacrylic anhydride in the reaction evaluation of Examples 1-5 and Comparative Examples 1-6.

(Liquid phase oxidation reaction)
In the present invention, α, β-unsaturated carboxylic acid is produced by liquid phase oxidation of alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen.

  As the raw material alcohol, 2-propanol, t-butanol, 2-butanol and the like can be used. Of these, 2-propanol and t-butanol are preferable. The raw material alcohol may contain a small amount of water, saturated hydrocarbons and / or lower saturated aldehydes as impurities. When alcohol is used as a raw material, it goes through a dehydration reaction, so that the α, β-unsaturated carboxylic acid produced is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin produced by the dehydration reaction. It is an acid. For example, when the raw material is 2-propanol, propylene is produced by a dehydration reaction, so that acrylic acid having the same carbon skeleton as that of propylene is produced. When the raw material is t-butyl alcohol, isobutylene is produced by the dehydration reaction, so that methacrylic acid having the same carbon skeleton as that of isobutylene is obtained.

  Propylene, isobutylene, 2-butene and the like can be used as the raw material olefin. Of these, propylene and isobutylene are preferable. The raw material olefin may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities. The α, β-unsaturated carboxylic acid produced is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin. For example, acrylic acid is produced when the raw material is propylene, and methacrylic acid is produced when the raw material is isobutylene.

  As the raw material α, β-unsaturated aldehyde, acrolein, methacrolein, crotonaldehyde (β-methylacrolein), cinnamaldehyde (β-phenylacrolein) and the like can be used. Of these, acrolein and methacrolein are preferable. The raw α, β-unsaturated aldehyde may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities. The α, β-unsaturated carboxylic acid produced is an α, β-unsaturated carboxylic acid in which the aldehyde group of the α, β-unsaturated aldehyde is changed to a carboxyl group. For example, acrylic acid is produced when the raw material is acrolein, and methacrylic acid is produced when the raw material is methacrolein.

  One kind of alcohol, olefin and α, β-unsaturated aldehyde as raw materials for the liquid phase oxidation reaction may be used, or two or more kinds may be used in combination.

  The liquid phase oxidation reaction may be performed in either a continuous type or a batch type, but in view of productivity, the continuous type is preferred industrially.

  As the source of molecular oxygen used in the liquid phase oxidation reaction, air is economical and preferable, but pure oxygen or a mixed gas of pure oxygen and air can also be used. These gases, nitrogen, carbon dioxide, water vapor, etc. A mixed gas diluted with can also be used. The gas serving as the source of molecular oxygen is preferably supplied in a pressurized state into a reaction vessel such as an autoclave.

  As a solvent used for the liquid phase oxidation reaction, t-butanol, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid, iso-valeric acid, ethyl acetate An organic solvent such as methyl propionate can be used. Among these, t-butanol, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid, and iso-valeric acid are preferable. 1 type may be used for an organic solvent and it may use 2 or more types together. In order to produce the α, β-unsaturated carboxylic acid with higher selectivity, it is preferable to use a mixed solvent of an organic solvent and water. The content of water in the mixed solvent is preferably 2 to 70% by mass, and more preferably 5 to 50% by mass. The mixed solvent is preferably in a uniform state, but may be in a non-uniform state. When alcohol is used as a raw material, the alcohol can also serve as a solvent.

  0.1-30 mass% is preferable with respect to the solvent which exists in a reactor, and the density | concentration of a raw material has more preferable 0.5-20 mass%.

  The amount of molecular oxygen used is preferably 0.1 to 20 mol, more preferably 0.2 to 15 mol, and still more preferably 0.3 to 10 mol with respect to 1 mol of the raw material.

  The reaction temperature and reaction pressure are appropriately selected depending on the solvent and raw materials used. The reaction temperature is preferably 30 to 200 ° C, more preferably 50 to 150 ° C. The reaction pressure is preferably 0 to 10 MPa (gauge pressure; hereinafter, pressure is expressed as gauge pressure), more preferably 0.5 to 5 MPa.

[Molybdenum compound]
In the present invention, when performing the liquid phase oxidation reaction, the molybdenum compound is dissolved and / or dispersed and the mass ratio of molybdenum element (hereinafter referred to as “Mo element”) is 1 mass ppm or more and 40 mass ppm. Molybdenum supply liquid (hereinafter referred to as “Mo supply liquid”) is supplied to the reaction system for performing the liquid phase oxidation, and the mass of the liquid present in the reaction system is as follows: The liquid phase oxidation is performed under the condition that the mass ratio of the Mo element present in the reaction system does not exceed 270 mass ppm (hereinafter, “mass ppm” is simply expressed as “ppm”).

  Examples of the molybdenum compound include molybdenum oxides such as molybdenum dioxide and molybdenum trioxide; heteropolymolybdic acids such as phosphomolybdic acid and silicomolybdic acid; and salts of the heteropolymolybdic acid. Examples of the salt of heteropolymolybdic acid include alkali metal salts such as Li salt, Na salt and K salt, and alkaline earth metal salts such as Ca salt, Sr salt and Ba salt. A molybdenum compound may be used alone or in combination of two or more.

  Examples of the liquid for dissolving and / or dispersing the molybdenum compound when preparing the Mo supply liquid include raw materials such as a reaction solvent and alcohol. The method of supplying the Mo supply liquid to the reaction liquid may be either a continuous type or a batch type, but a continuous type is preferred industrially. The mass ratio of the Mo element in the Mo supply liquid is in the range of 1 ppm to 40 ppm, more preferably in the range of 2 ppm to 30 ppm.

  It is preferable that the supplied molybdenum compound is dissolved and dispersed in a reaction solution for performing liquid phase oxidation. Due to the effects of both the molybdenum compound dissolved in the reaction solution and the molybdenum compound dispersed in the reaction solution, the productivity of the target product α, β-unsaturated carboxylic acid can be further increased. . In addition, when the catalyst which exists in the reaction liquid which performs liquid phase oxidation, or a supported catalyst is used, a part or all of the supplied molybdenum compound may be adsorbed by the support | carrier in the catalyst. In other words, when at least a part of the molybdenum compound supplied into the reaction system is supported on a catalyst present in the reaction liquid that undergoes liquid phase oxidation, or when a supported catalyst is used, It may be in a state of being supported on the carrier.

  Furthermore, a molybdenum compound may be present in the reaction system that performs liquid phase oxidation by another method, in addition to the method of supplying the Mo supply solution. Other methods include (A) a method using a catalyst carrying a molybdenum compound, (B) a method using a carrier carrying a molybdenum compound when using a supported catalyst, and (C) a solid. And a method of adding the molybdenum compound in a state to the reaction solution. A plurality of these methods may be combined. The method for producing the catalyst (A) and the method for preparing the carrier (B) will be described later.

  The mass of the molybdenum compound present in the reaction system that performs liquid phase oxidation must be such that the mass ratio of the Mo element present in the reaction system to the mass of the liquid present in the reaction system exceeds 0 ppm. However, the mass ratio of the Mo element is preferably 1 ppm or more, more preferably 5 ppm or more, and even more preferably 10 ppm or more. Further, the mass of the molybdenum compound present in the reaction system must be such that the mass ratio of Mo element present in the reaction system to the liquid present in the reaction system does not exceed 270 ppm. The mass ratio of the Mo element is preferably not more than 250 ppm, more preferably not more than 200 ppm, and still more preferably not more than 180 ppm. The mass of Mo element present in the reaction system means the molybdenum compound dissolved in the reaction liquid, the molybdenum compound dispersed in the reaction liquid, and the molybdenum supported on the catalyst present in the reaction system. When a compound and a supported catalyst are used, it means the total of molybdenum compounds supported on a carrier in the catalyst.

  Liquid phase oxidation is carried out in a reaction system containing such an amount of Mo element, and the catalyst life of α, β-unsaturated carboxylic acid is stabilized by using a catalyst containing palladium and tellurium (productivity and (Selectivity reduction can be suppressed). The presence of the molybdenum compound in the reaction system makes it possible to increase the productivity of the target product, α, β-unsaturated carboxylic acid. In the case where the molybdenum compound is present under the condition that the mass ratio of the Mo element present in the sample exceeds 270 ppm, the productivity of the α, β-unsaturated carboxylic acid at the initial stage of the reaction can be increased, but the decrease in productivity becomes severe, The so-called catalyst life is greatly reduced.

  The mass of Mo element contained in the molybdenum compound dissolved in the reaction solution can be directly measured from the reaction solution by atomic absorption spectrometry (frameless).

  The mass of the Mo element contained in the molybdenum compound dispersed in the reaction solution and the molybdenum compound supported on the catalyst or the carrier can be measured by the following method. That is, a sample (catalyst or dispersion) to be measured and a predetermined amount of a mixture of concentrated nitric acid and concentrated sulfuric acid (concentrated nitric acid: concentrated hydrochloric acid = 1: 1) are placed in a beaker and dissolved in a microwave thermal decomposition apparatus. Next, the dissolution-treated product is filtered and washed, and the filtrate and washing water are combined and made up into a volumetric flask to obtain a molybdenum solution. The mass of Mo element contained in the molybdenum solution thus obtained is quantified with an ICP emission spectrometer.

  When liquid phase oxidation is performed by continuously supplying a reaction solution having a known molybdenum compound concentration to the reaction system, the concentration of the molybdenum compound, the molecular weight of the molybdenum compound, From the atomic weight, the mass of Mo element contained in the molybdenum compound dissolved and dispersed in the reaction solution in the reaction system can be determined by a conventional method.

〔catalyst〕
In the present invention, a catalyst containing palladium and tellurium is used for the liquid phase oxidation reaction.

  The chemical state of palladium in the catalyst may be a metallic state or an oxidized state, but it is preferable that the palladium is in a metallic state because it exhibits high catalytic activity. The chemical state of tellurium in the catalyst may be a metallic state or an oxidized state, but tellurium is preferably in a metallic state because it changes the electronic state of palladium more. Moreover, since palladium and tellurium are adjacent to each other, the percentage of palladium in which the electronic state is greatly changed is increased. Therefore, tellurium is preferably alloyed with palladium or formed an intermetallic compound.

  The molar ratio of tellurium to palladium (Te / Pd) needs to exceed 0, but is preferably 0.001 to 0.40, more preferably 0.002 to 0.30, and 0.003 to 0.00. 25 is more preferable. By using a catalyst containing palladium and tellurium at such a molar ratio, the selectivity and productivity of the α, β-unsaturated carboxylic acid can be further increased. Te / Pd can be adjusted by the blending ratio of the palladium and tellurium raw materials used in the production of the catalyst.

Te / Pd can be calculated from the mass and atomic weight of palladium and tellurium in the catalyst. The masses of palladium and tellurium in the catalyst can be measured by sequentially performing the following steps.
-Preparation of treatment solution A: 0.2 g of catalyst and a predetermined amount of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide solution are placed in a Teflon (registered trademark) decomposition tube and dissolved in a microwave thermal decomposition apparatus. The sample is filtered, and the filtrate and washing water are combined, and the volume is made up in a volumetric flask to obtain the treatment solution A.
-Preparation of B treatment liquid: The filter paper which collected the insoluble part in the preparation of A treatment liquid is transferred to a platinum crucible, heated and incinerated, and then added with lithium metaborate and melted with a gas burner. After cooling, add hydrochloric acid and a small amount of water in a crucible and dissolve, then add up to a volumetric flask to make the B treatment solution.
Quantitative determination of palladium and tellurium in the catalyst: The masses of palladium and tellurium contained in the obtained A treatment liquid and B treatment liquid were each quantified with an ICP emission spectrometer, and the total values of palladium and tellurium in the catalyst respectively Mass.

  The catalyst may contain other metal elements. Examples of other metal elements include noble metal elements such as platinum, rhodium, ruthenium, iridium, gold, silver and osmium; and base metal elements such as bismuth, antimony, thallium, lead and mercury. 1 type may be used for the other metal element contained in a catalyst, and 2 or more types may be used together. From the viewpoint of expressing high catalytic activity, the total amount of palladium and tellurium among the metal elements contained in the catalyst is preferably 25% by mass or more, more preferably 50% by mass or more, and 80% by mass or more. More preferably.

  The catalyst may be an unsupported type, but is preferably a supported type in which palladium and tellurium are supported on a carrier. As the carrier, activated carbon, carbon black, silica, alumina, magnesia, calcia, titania, zirconia and the like can be used. Among these, activated carbon, silica, alumina, titania and zirconia are preferable. One type of carrier may be used, or two or more types may be used in combination. When using 2 or more types of support | carriers together, the mixture which mixed silica and an alumina can also be used, for example, and complex oxides, such as a silica-alumina, can also be used.

Since the specific surface area of a preferable carrier varies depending on the type of the carrier, it cannot be generally stated. For example, the specific surface area of the activated carbon support is preferably ^{100~5000m 2 / g, 300~4000m 2 /} g is more preferable. The specific surface area of the silica support is preferably 10~2000m ² / g, more preferably 50~1500m ² / g, more preferably 100~1000m ² / g. The smaller the specific surface area of the support is, the more the components with useful components (palladium and tellurium) supported on the surface can be produced. The larger the range, the more the components with useful components supported. . The specific surface area of the carrier can be measured by a nitrogen gas adsorption method.

  The pore volume of the carrier is preferably from 0.1 to 2.0 cc / g, more preferably from 0.2 to 1.5 cc / g.

  The supported rate of palladium in the supported catalyst is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, and still more preferably 4 to 20% by mass with respect to the mass of the carrier before being supported.

  The mass of the carrier used can be measured by an appropriate method depending on the type of the carrier. For example, in the case of a silica support, the catalyst is placed in a platinum crucible, melted by adding sodium carbonate, and distilled water is added to form a homogeneous solution. By quantifying Si atoms in the sample solution with ICP, the mass of silicon element is obtained. And the mass of the silica support can be calculated. In the case of a titania carrier or zirconia carrier, the catalyst is placed in a Teflon (registered trademark) decomposition tube, concentrated sulfuric acid and hydrofluoric acid are added, dissolved in a microwave thermal decomposition apparatus, distilled water is added as a uniform solution, and the sample solution is obtained by ICP By quantifying the Ti atom or Zr atom in the medium, the mass of the titanium element or zirconia element can be obtained, and the mass of the titania carrier or zirconia carrier can be calculated.

  The catalyst is preferably used in a state of being suspended in a reaction solution for performing a liquid phase oxidation reaction, but may be used in a fixed bed. 0.1-30 mass% is preferable with respect to the solution which exists in a reactor, and the usage-amount of a catalyst has more preferable 0.5-20 mass%, and 1-15 mass% is further more preferable.

[Production method of catalyst]
A catalyst containing palladium and tellurium can be produced using raw materials supplying palladium and tellurium. When the catalyst contains another metal element, a raw material for supplying the metal element may be used in combination. As a raw material, a single metal of each element, an alloy of two or more of these, or a compound containing each element can be used. Such raw materials are appropriately selected, and the amount of the raw materials used is appropriately adjusted so that a catalyst having a target composition is obtained.

  As the raw material of palladium, palladium metal, palladium salt, palladium oxide and the like can be used. Of these, palladium salts are preferred. Examples of the palladium salt include palladium chloride, palladium acetate, palladium nitrate, palladium sulfate, tetraammine palladium chloride, bis (acetylacetonato) palladium and the like. Among these, palladium chloride, palladium acetate, palladium nitrate, and tetraammine palladium chloride are preferable, and palladium nitrate is more preferable. The palladium raw material may be used alone or in combination of two or more.

  As a raw material of tellurium, tellurium metal, tellurium salt, telluric acid and its salt, telluric acid and its salt, tellurium oxide and the like can be used. Of these, telluric acid and its salt, telluric acid and its salt, and tellurium oxide are preferred. Examples of tellurium salts include hydrogen telluride, tellurium tetrachloride, tellurium dichloride, tellurium hexafluoride, tellurium tetraiodide, tellurium tetrabromide, tellurium dibromide and the like. Examples of tellurate include sodium tellurate and potassium tellurate. Examples of tellurite include sodium tellurite and potassium tellurite. One type of tellurium raw material may be used, or two or more types may be used in combination.

  As a method for producing a catalyst containing palladium and tellurium, a method having a step of reducing a compound containing palladium element in an oxidized state with a reducing agent and a step of mixing a compound containing tellurium element in an oxidized state is preferable. Furthermore, you may have the process of reducing the tellurium element of an oxidation state with a reducing agent. Moreover, the tellurium element can be reduced simultaneously with the reduction of the palladium element by mixing the compound containing the tellurium element before reducing the palladium element. When the reduction of palladium element and the reduction of tellurium element are performed in separate steps, the reduction of palladium element may be performed first, or the reduction of tellurium element may be performed first. The conditions in these reduction steps can be set independently.

  As the reducing agent, one having at least the ability to reduce palladium element in an oxidized state can be used. Examples of reducing agents include hydrazine, formaldehyde, sodium borohydride, hydrogen, formic acid, formic acid salt, ethylene, propylene, 1-butene, 2-butene, isobutylene, 1,3-butadiene, 1-heptene, 2- Examples include heptene, 1-hexene, 2-hexene, cyclohexene, allyl alcohol, methallyl alcohol, acrolein, and methacrolein. One reducing agent may be used, or two or more reducing agents may be used in combination.

  The reduction with the reducing agent may be performed in the gas phase, but is preferably performed in the liquid phase. As a reducing agent when performing reduction in the gas phase, hydrogen is preferable. As a reducing agent when performing reduction in the liquid phase, hydrazine, formaldehyde, formic acid, and a salt of formic acid are preferable.

  However, it is preferable that the reducing agent does not contain sulfur. Here, the reducing agent not containing sulfur means that no sulfur element is contained in the structure of the reducing agent, that is, it is not a sulfur-containing compound, and is a reduction in which sulfur or a sulfur compound is contained as a small amount of impurities. The agent is not included. Since reduction with a reducing agent is preferably performed at a relatively low temperature, when a reducing agent that is a sulfur-containing compound is used, sulfur is strongly adsorbed on a carrier, palladium, tellurium, etc., and the activity of the resulting catalyst may be reduced. .

  As the solvent used for the reduction in the liquid phase, water is preferable. However, depending on the solubility of the raw material and the reducing agent and the dispersibility of the carrier when producing a supported catalyst, ethanol, 1-propanol, Alcohols such as 2-propanol, n-butanol and t-butanol; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; Organic acids such as acetic acid, n-valeric acid and isovaleric acid; heptane, hexane and cyclohexane An organic solvent such as hydrocarbons can be used. 1 type may be used for an organic solvent and it may use 2 or more types together. A mixed solvent of an organic solvent and water can also be used.

  When the reducing agent is a gas, it is preferably carried out in a pressure device such as an autoclave that increases the solubility of the reducing agent in the solution. At that time, the inside of the pressurizer is pressurized with a reducing agent. The pressure is preferably 0.1 to 1.0 MPa.

  When the reducing agent is a liquid, the reduction can be performed by adding the reducing agent to the solution. The amount of the reducing agent used is preferably 1 to 100 mol with respect to 1 mol of the palladium element in the oxidized state.

  The reduction temperature is preferably -5 to 150 ° C, more preferably 15 to 80 ° C. The reduction time is preferably 0.1 to 4 hours, more preferably 0.25 to 3 hours, and further preferably 0.5 to 2 hours.

  When the above-mentioned catalyst (A) is produced, a step of mixing a molybdenum compound may be performed. By doing so, the molybdenum compound is supported on the catalyst. Since it is not necessary to reduce the molybdenum compound, the molybdenum compound can be mixed after the above reduction step. However, a molybdenum compound may be mixed before performing the above reduction step.

  When producing a supported catalyst, the raw material may be supported on a carrier. Examples of methods for supporting the raw material on the carrier include precipitation methods, ion exchange methods, impregnation methods, and deposition methods. In the case of producing by the impregnation method, the palladium raw material and the tellurium raw material may be impregnated and supported simultaneously, or after impregnating and supporting one of the raw materials, the remaining raw materials may be impregnated and supported. The amount of the carrier used is appropriately adjusted so that a catalyst having a desired loading rate can be obtained.

  However, when an activated carbon-supported catalyst is produced, when a solution containing palladium raw material and tellurium raw material is contacted with a support (activated carbon), palladium element and tellurium element are formed by reaction with active groups present on the outer surface of the support. In some cases, the catalyst is reduced and deposited, and becomes a catalyst in which palladium metal and tellurium metal are unevenly distributed on the outer surface of the support. Accordingly, it is preferable that an appropriate amount of an oxidizing agent such as hydrogen peroxide, nitric acid, hypochlorous acid, or the like is present in the solution containing the palladium raw material and the tellurium raw material before the reduction with the reducing agent. Even in the case of other carriers, the palladium element and the tellurium element may be reduced depending on the production conditions. Similarly, the reduction can be prevented by the presence of an appropriate amount of an oxidizing agent.

  When the carrier in the state (B) described above is used, a step of supporting the molybdenum compound on the carrier may be performed. This step may be performed before the raw material is supported on the carrier, or may be performed after the raw material is supported on the carrier. For example, the molybdenum compound can be supported on the carrier by a method in which the carrier and the molybdenum compound are dissolved and / or dispersed in a solvent and then the solvent is removed. The solvent is preferably a solvent having a pH of 9 or less from the viewpoint of suppressing dissolution of the carrier in the solvent. The molybdenum compound may be dispersed in a solvent, or all or a part of it may be dissolved in the solvent. The solvent can be removed by filtration, evaporation, dry-up, centrifugation, or the like. In addition, after removing the solvent, drying and / or firing may be performed as necessary. Drying can be performed by, for example, a general box-type dryer. Firing can be performed, for example, using a muffle furnace at a temperature not lower than the drying temperature and not higher than 800 ° C. with little structural change of the carrier. The firing time is preferably 0.5 to 24 hours.

  After the palladium raw material and the tellurium raw material are supported on the carrier, heat treatment may be performed before the reduction, so that palladium oxide and tellurium oxide are supported on the carrier. The heat treatment temperature is preferably from the decomposition temperature of the raw material used to 800 ° C, more preferably from 200 to 700 ° C. The heat treatment time is preferably 0.5 to 24 hours, more preferably 1 to 12 hours. The heat treatment may be performed in air or in an inert gas such as nitrogen.

  The produced catalyst is preferably washed with water, a solvent or the like. By washing with water, a solvent or the like, impurities derived from raw materials such as chloride, acetate radical, nitrate radical and sulfate radical are removed. Since some impurities may inhibit the liquid phase oxidation reaction, it is preferable to perform a method capable of sufficiently removing impurities and the number of times of washing. The washed catalyst may be recovered by filtration or centrifugation and used for the reaction as it is.

  Further, the recovered catalyst may be dried. For example, the catalyst can be dried in air or in an inert gas using a dryer. The dried catalyst can be activated prior to use for liquid phase oxidation if desired. For example, a method of heat-treating the catalyst in a reducing atmosphere in a hydrogen stream can be mentioned. According to this method, the oxide film on the palladium surface and impurities that could not be removed by washing can be removed.

  The physical properties of the produced catalyst can be confirmed by BET surface area measurement, XRD measurement, CO pulse adsorption method, TEM measurement, XPS measurement and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to an Example.

(Measurement of the molar ratio of tellurium and palladium (Te / Pd) in the catalyst)
It was calculated from the mass and atomic weight of palladium and tellurium in the catalyst. The masses of palladium and tellurium in the catalyst were measured by sequentially performing the following steps.
Preparation of treatment solution A: 0.2 g of catalyst and a predetermined amount of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide water were placed in a Teflon (registered trademark) decomposition tube, and a microwave thermal decomposition apparatus (CEM, product name: The dissolution treatment was performed with MARS5). The sample was filtered, and the filtrate and the washing water were combined and made up into a volumetric flask to obtain a treatment solution A.
-Preparation of B treatment liquid: The filter paper which collected the insoluble part in the preparation of the A treatment liquid was transferred to a platinum crucible, heated and incinerated, and then added with lithium metaborate and melted with a gas burner. After cooling, hydrochloric acid and a small amount of water were put in a crucible and dissolved, and then measured up in a measuring flask to obtain a B treatment solution.
-Quantification of tellurium and palladium in the catalyst: The masses of palladium and tellurium contained in the obtained A treatment liquid and B treatment liquid were each quantified with an ICP emission analyzer (trade name: IRIS-Advantage, manufactured by Thermo Elemental) The total value was defined as the mass of palladium and tellurium in the catalyst, respectively.

(Measurement of Mo element contained in reaction system)
The mass of Mo element contained in the reaction solution was calculated by a conventional method from the concentration of the molybdenum compound, the molecular weight of the molybdenum compound, the atomic weight of molybdenum, and the like. The mass of Mo element adsorbed on the catalyst after use in the reaction was measured with an ICP emission spectrometer in accordance with the above-described mass measurement method for tellurium and palladium.

(Analysis of raw materials and products)
Analysis of raw materials and products was performed using gas chromatography. Reaction rate of olefin used as raw material, selectivity of produced α, β-unsaturated aldehyde, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid anhydride, and produced α, β-unsaturated The productivity of saturated carboxylic acid is defined as follows.
Olefin reaction rate (%) = (B / A) × 100
Selectivity of α, β-unsaturated aldehyde (%) = (C / B) × 100
Selectivity of α, β-unsaturated carboxylic acid (%) = (D / B) × 100
Selectivity of α, β-unsaturated carboxylic acid anhydride (%) = (2 × E / B) × 100 productivity of α, β-unsaturated carboxylic acid (g / (g−Pd · h)) = F / (G x H)
Here, A is the number of moles of olefin supplied, B is the number of moles of reacted olefin, C is the number of moles of α, β-unsaturated aldehyde produced, and D is the mole of α, β-unsaturated carboxylic acid produced. Number, E is the number of moles of α, β-unsaturated carboxylic acid anhydride produced, F is the mass of the α, β-unsaturated carboxylic acid produced (unit: g), and G is Pd in the catalyst used in the reaction. Mass (unit: g), H is the reaction time (unit: h).

<Example 1>
(Manufacture of catalyst)
1.46 g of telluric acid was dissolved in 270 g of pure water, and 64.08 g of palladium nitrate solution (manufactured by NE Chemcat, Pd content 23.41% by mass) was dissolved in the resulting solution to obtain a mixed solution. Prepared. In this mixed solution, 150 g of silica support (specific surface area 450 m ² / g, pore volume 0.68 cc / g) was added and immersed, and then evaporation was performed so that telluric acid and palladium nitrate were added to the silica support. Supported. Next, the silica support was calcined in air at 200 ° C. for 3 hours to obtain a catalyst precursor. This catalyst precursor was added to 450 g of a 37 mass% formaldehyde aqueous solution, and reduction was performed at 70 ° C. for 2 hours. A catalyst (PdTe) in which palladium and tellurium were supported on a silica support was obtained through suction filtration and washing with pure water. The obtained catalyst had a Te / Pd of 0.05.

(Reaction evaluation)
As a reaction vessel for conducting the liquid phase oxidation reaction, a jacketed stainless steel stirred tank reactor having an inner diameter of 126 mm and a capacity of 4 liters was used. The raw material is supplied from the upper part of the reaction vessel together with the solvent, and the reaction liquid is continuously extracted from the system while keeping the liquid surface of the liquid phase part constant. The above-prepared catalyst (palladium mass is 15 g) and a 75 mass% t-butanol aqueous solution as a solvent were introduced into the reaction vessel so as to reach the control liquid level (the liquid level was 3 liters). It was adjusted).

  Nitrogen gas was supplied from the upper part of the reaction vessel to the gas phase part at 614 g / hr to increase the pressure to 4.8 MPa (absolute pressure), and this pressure was maintained by a pressure controller thereafter. The liquid phase temperature was raised to 110 ° C. and stabilized for about 10 minutes, and then liquefied isobutylene was 950 g / hr, 80.4 mass% t-butanol aqueous solution (prepared by containing 215 ppm of p-methoxyphenol as a polymerization inhibitor). 3543 g / hr, molybdenum-containing aqueous solution (prepared by adding 2.21 g of molybdenum trioxide to 4997.8 g of pure water and heating and stirring at 80 ° C. for 3 hours) at 257 g / hr continuously to the reaction vessel did. The mass ratio of the supplied Mo element with respect to the mass of the supplied liquid at this time (hereinafter referred to as “the concentration of Mo element in the supply liquid”: dissolved in the reaction liquid with respect to the mass of the liquid existing in the reaction system) Or equivalent to the mass ratio of Mo element contained in the dispersed molybdenum compound) was 16 ppm, and the average residence time was 0.5 hours.

  Next, as an oxygen source for the liquid phase oxidation reaction, compressed air was continuously supplied to the liquid phase portion in the reaction vessel through a sparger made of sintered metal to initiate the reaction. Thereafter, the nitrogen gas supplied to the gas phase portion was gradually reduced and finally the supply was stopped. During the reaction, the oxygen concentration in the exhaust gas was constantly monitored by a magnetic oximeter (manufactured by Yokogawa Electric Corporation), and the supply amount of compressed air was controlled so that the unreacted oxygen concentration was maintained at about 6% by volume.

  To confirm the reaction results, the reaction solution and exhaust gas were sampled and analyzed. Analysis of raw materials and products was performed using gas chromatography (manufactured by Shimadzu Corporation) equipped with an FID or TCD detector. The results are shown in Table 1, FIG. 1 and FIG. Further, as a result of measuring the mass of Mo element adsorbed on the catalyst after use, it was 0.13% by mass with respect to the catalyst, and the catalyst present in the reaction system with respect to the mass of the liquid present in the reaction system. The mass ratio of the Mo element in it (hereinafter referred to as “the concentration of the Mo element in the catalyst”) was 88 ppm. From this, the mass ratio of the Mo element present in the reaction system to the mass of the liquid present in the reaction system (hereinafter referred to as “Mo element concentration present in the reaction system”: concentration of Mo element in the supply liquid) + Mo element concentration in the catalyst) was found to be 104 ppm.

<Example 2>
A catalyst was produced in the same manner as in Example 1. The reaction evaluation was performed in the same manner as in Example 1 except that a molybdenum-containing aqueous solution (prepared by adding 4.43 g of molybdenum trioxide to 4995.6 g of pure water and heating and stirring at 80 ° C. for 3 hours) was used. . At this time, the concentration of Mo element in the supply liquid was 32 ppm, and the average residence time was 0.5 hours. The results are shown in Table 2, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.16% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 111 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 143 ppm.

<Comparative Example 1>
A catalyst was produced in the same manner as in Example 1. In the reaction evaluation, a molybdenum-containing aqueous solution prepared in the same manner as in Example 2 was continuously supplied at 514 g / hr, and an 86.6% by mass t-butanol aqueous solution (231 ppm of p-methoxyphenol was used as a polymerization inhibitor). This was carried out in the same manner as in Example 1 except that it was continuously fed at 3286 g / hr. At this time, the concentration of Mo element in the supply liquid was 64 ppm, and the average residence time was 0.5 hours. The results are shown in Table 3, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.15% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 105 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 169 ppm.

<Example 3>
A catalyst was produced in the same manner as in Example 1. The reaction evaluation was performed in the same manner as in Example 1 except that a molybdenum-containing aqueous solution (prepared by adding 0.55 g of molybdenum trioxide to 4995.6 g of pure water and stirring at 80 ° C. for 3 hours) was used. . At this time, the concentration of the Mo element in the supply liquid was 4 ppm, and the average residence time was 0.5 hours. The results are shown in Table 4, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.18% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 126 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 130 ppm.

<Example 4>
A catalyst was produced in the same manner as in Example 1. The reaction was evaluated in the same manner as in Example 1 except that a molybdenum-containing aqueous solution (prepared by adding 1.11 g of molybdenum trioxide to 4995.6 g of pure water and stirring at 80 ° C. for 3 hours) was used. . At this time, the concentration of Mo element in the supply liquid was 8 ppm, and the average residence time was 0.5 hours. The results are shown in Table 5, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.23% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 161 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 169 ppm.

<Comparative example 2>
A catalyst was produced in the same manner as in Example 1. The reaction was evaluated except that a molybdenum-containing aqueous solution (prepared by adding 27.33 g of silicomolybdic acid n hydrate [n≈30] to pure water 4970.8 g and stirring at 80 ° C. for 3 hours) was used. The same method as in Example 1 was used. At this time, the concentration of Mo element in the supply liquid was 144 ppm, and the average residence time was 0.5 hours. The results are shown in Table 6, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.17% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 119 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 263 ppm.

<Example 5>
(Manufacture of catalyst)
Dissolving 2.43 g of telluric acid in 450 g of pure water, and dissolving 106.79 g of palladium nitrate solution (manufactured by NE Chemcat, Pd content 23.41 mass%) in the resulting solution, the mixed solution was dissolved. Prepared. In this mixed solution, 250 g of silica support (specific surface area 450 m ² / g, pore volume 0.68 cc / g) was added and immersed, and then evaporation was performed, whereby telluric acid and palladium nitrate were added to the silica support. Supported. Next, the silica support was calcined in air at 200 ° C. for 3 hours to obtain a catalyst precursor. This catalyst precursor was added to 900 g of a 37% by mass aqueous formaldehyde solution and reduced at 70 ° C. for 2 hours. A catalyst (PdTe) in which palladium and tellurium were supported on a silica support was obtained through suction filtration and washing with pure water. The obtained catalyst had a Te / Pd of 0.05.

(Reaction evaluation)
The same procedure as in Example 4 was performed, except that the catalyst was changed to the prepared catalyst (palladium mass: 25 g). At this time, the concentration of Mo element in the supply liquid was 8 ppm, and the average residence time was 0.5 hours. The results are shown in Table 7, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.15 mass% with respect to the catalyst, and the concentration of Mo element in the catalyst was 175 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 183 ppm.

<Comparative Example 3>
A catalyst was produced in the same manner as in Example 5. In the reaction evaluation, a molybdenum-containing aqueous solution was not supplied to the reaction solution, and a 75 mass% t-butanol aqueous solution (prepared by containing 200 ppm of p-methoxyphenol as a polymerization inhibitor) was continuously supplied at 3800 g / hr. Except for this, the same method as in Example 1 was used. At this time, the concentration of Mo element in the supply liquid was 0 ppm, and the average residence time was 0.5 hours. The results are shown in Table 8, FIG. 1 and FIG. Moreover, adsorption | suction of Mo element was not confirmed by the catalyst after use.

<Comparative Example 4>
A catalyst was produced in the same manner as in Example 1. The reaction was evaluated except that a molybdenum-containing aqueous solution (prepared by adding 29.18 g of phosphomolybdic acid n hydrate [n≈30] to 4970.8 g of pure water and heating and stirring at 80 ° C. for 3 hours) was used. The same method as in Example 1 was used. At this time, the concentration of Mo element in the feed liquid was 190 ppm, and the average residence time was 0.5 hours. The results are shown in Table 9, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.13% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 88 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 278 ppm.

<Comparative Example 5>
Except that no telluric acid was added during the production of the catalyst, a catalyst (Pd) in which palladium was supported on a silica carrier was produced in the same manner as in Example 1, and the reaction evaluation was carried out using the obtained catalyst. The same method as in No. 2 was performed. The results are shown in Table 10, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.10% by mass with respect to the catalyst, and the concentration of Mo element in the catalyst was 72 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 104 ppm.

<Comparative Example 6>
(Manufacture of catalyst)
5 g of nitric acid was dissolved in 3.42 g of bismuth nitrate pentahydrate. A mixed solution is prepared by slowly adding a bismuth solution to 270 g of pure water and dissolving 64.08 g of a palladium nitrate solution (manufactured by NE Chemcat, Pd content 23.41 mass%) in the resulting solution. did. In this mixed solution, 135 g of silica support (specific surface area 450 m ² / g, pore volume 0.68 cc / g) was added and immersed, and then evaporated to convert bismuth nitrate and palladium nitrate to the silica support. Supported. Next, the silica support was calcined in air at 200 ° C. for 3 hours to obtain a catalyst precursor. This catalyst precursor was added to 450 g of a 37 mass% formaldehyde aqueous solution, and reduction was performed at 70 ° C. for 2 hours. A catalyst (PdBi) in which palladium and bismuth were supported on a silica carrier was obtained through suction filtration and washing with pure water. The resulting catalyst had a Bi / Pd of 0.05.

(Reaction evaluation)
Reaction evaluation was performed in the same manner as in Example 2 using the prepared catalyst. The results are shown in Table 11, FIG. 1 and FIG. Further, the mass of Mo element adsorbed on the catalyst after use was 0.25 mass% with respect to the catalyst, and the concentration of Mo element in the catalyst was 174 ppm. From this, it was found that the concentration of Mo element present in the reaction system was 206 ppm.

  The conditions in the above Examples and Comparative Examples are summarized in Table 12 including the reaction time.

  From FIG. 1, it was found that Comparative Examples 5 and 6 had low methacrylic acid productivity from the beginning, and Comparative Examples 3 and 4 had a large decrease in methacrylic acid productivity over time. Further, FIG. 2 indicates that Comparative Examples 1, 2 and 4 have a large decrease in methacrylic acid selectivity over time.

Claims (4)

A process for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of an alcohol, olefin or α, β-unsaturated aldehyde with molecular oxygen in the presence of a catalyst containing palladium and tellurium, In a dissolved and / or dispersed state, and a molybdenum feed liquid having a molybdenum element mass ratio of 1 mass ppm or more and 40 mass ppm or less is fed into the reaction system for performing the liquid phase oxidation, and The α, β-unsaturated carboxylic acid is characterized in that the liquid phase oxidation is performed under the condition that the mass ratio of the molybdenum element present in the reaction system to the mass of the liquid present in the reaction system does not exceed 270 mass ppm. Acid production method.   The method for producing an α, β-unsaturated carboxylic acid according to claim 1, wherein at least a part of the molybdenum compound present in the reaction system is supported on the catalyst.   The method for producing an α, β-unsaturated carboxylic acid according to claim 1 or 2, wherein palladium and tellurium in the catalyst are supported on a carrier.   The method for producing an α, β-unsaturated carboxylic acid according to claim 3, wherein at least a part of the molybdenum compound present in the reaction system is supported on the carrier.

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