JP6650351B2 - Catalyst, method for producing catalyst, and method for producing aldehydes - Google Patents

Description

  The present invention relates to a catalyst, a method for producing a catalyst, and a method for producing aldehydes. More specifically, the present invention relates to a catalyst for producing aldehydes from carboxylic acids, a method for producing the catalyst, and a method for producing aldehydes from carboxylic acids by hydrogenation using the catalyst.

  Patent Document 1 discloses an iron oxide catalyst (palladium-supported iron oxide catalyst) containing 2.5 to 90% by weight of palladium as a catalyst for producing acetaldehyde from acetic acid by hydrogenation. In addition, by hydrogenation of acetic acid using the catalyst, a gaseous product containing methane, ethane, ethylene, carbon dioxide, acetone, ethanol, ethyl acetate, water, unreacted acetic acid, etc., in addition to the main product acetaldehyde. Is disclosed.

  Patent Document 2 discloses, as a method for producing acetaldehyde by hydrogenation from acetic acid, using a catalyst in which iron, ruthenium, platinum, and tin are supported on a silica catalyst carrier.

  Patent Document 3 discloses, as a method for producing acetaldehyde by hydrogenation from acetic acid, using a catalyst in which cobalt, iron, and molybdenum are supported on an iron oxide or silica catalyst carrier.

  Non-Patent Document 1 discloses that acetaldehyde can be obtained with high selectivity by using a platinum-supported iron oxide catalyst as a method for producing acetaldehyde by hydrogenation from acetic acid.

JP-A-11-322658 JP 2011-529494 A JP 2012-153698 A

JOURNAL OF CATALYSIS 168, 255-264 (1997)

  The present inventors have found that when a hydrogenation reaction is carried out using an iron component as a catalyst as in the above document, acetaldehyde can be obtained with high selectivity when the conversion is low (for example, 40% or less). It has been found that when the rate is increased, the produced acetaldehyde is further hydrogenated and ethanol is by-produced.

  Therefore, an object of the present invention is to suppress the aldehyde hydrogenation reaction that occurs sequentially when aldehydes are produced from carboxylic acids by hydrogenation, and to increase the conversion rate of carboxylic acids to increase the selectivity of aldehydes. An object of the present invention is to provide a catalyst which can be maintained at a high level and can obtain aldehydes in a high yield. Another object of the present invention is to provide a method for producing aldehydes with high yield by hydrogenating carboxylic acids.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, by using a catalyst containing cerium, palladium and iron oxide in a specific ratio, when producing aldehydes from carboxylic acids by hydrogenation, it It has been found that the hydrogenation reaction of aldehydes occurring during the reaction is suppressed, the selectivity of aldehydes can be kept high even when the conversion of carboxylic acids is increased, and aldehydes can be produced in good yield, and the present invention has been completed.

That is, the catalyst of the present invention is a catalyst for producing aldehydes from carboxylic acids by hydrogenation, which contains cerium, palladium and iron oxide, and has a cerium (converted to Ce element) content of iron oxide (Fe). It is 0.1 to 4.5 parts by weight based on 100 parts by weight (in terms of ₂ O ₃ ).

In the catalyst of the present invention, the content of palladium (in terms of Pd element) is preferably 1 to 100 parts by weight based on 100 parts by weight of iron oxide (in terms of Fe ₂ O ₃ ).

  Further, the catalyst of the present invention is preferably in the form of a pellet.

  Further, the method for producing a catalyst of the present invention includes a step of preparing a dispersion or a solution containing cerium, palladium, and an iron component, a step of evaporating the dispersion or the solution to dryness, and a step of baking after evaporating to dryness. including.

  That is, the method for producing aldehydes of the present invention produces aldehydes from carboxylic acids by hydrogenation in the gas phase in the presence of the catalyst.

  In the method for producing aldehydes according to the present invention, the carboxylic acids are preferably acetic acid, and the aldehydes are preferably acetaldehyde.

  According to the catalyst of the present invention, the hydrogenation reaction of aldehydes which occurs sequentially when aldehydes are produced from carboxylic acids by hydrogenation can be suppressed, so that the selectivity of aldehydes can be increased even if the conversion of carboxylic acids is increased. Can be maintained high, and aldehydes can be produced in good yield. Further, according to the method for producing aldehydes of the present invention, aldehydes can be produced with high yield.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic flowchart which shows an example of the manufacturing method of aldehydes of this invention. It is a figure which shows the evaluation result of the reactivity evaluation 2 of a catalyst about the catalyst (E), (F), and (D) obtained in Example 2, 3 and Comparative Example 3. It is a figure which shows the evaluation result of the reactivity evaluation 2 of a catalyst about the catalyst (H) and (G) obtained by Example 4 and Comparative Example 4.

[catalyst]
The catalyst of the present invention is a catalyst for producing aldehydes from carboxylic acids by hydrogenation (catalyst for producing aldehydes), which contains cerium, palladium and iron oxide, and has a cerium (in terms of Ce element) content. for iron oxide (Fe ₂ O ₃ equivalent) 100 parts by weight, and 0.1 to 4.5 parts by weight. The iron oxide includes not only Fe ₂ O ₃ but also other oxidation states such as FeO and Fe ₃ O ₄ . The cerium may be an oxide such as Ce ₂ O ₃ or CeO ₂ .

The content of the iron oxide (in terms of Fe ₂ O ₃ ) in the catalyst of the present invention is, for example, 30% by weight or more (30 to 99% by weight), preferably 40 to 98% by weight, based on the entire catalyst. , More preferably 50 to 97% by weight. When the content of iron oxide is in the above range, sufficient catalytic activity is maintained, and a high selectivity to aldehydes and the like is obtained. The content of iron oxide (in terms of Fe ₂ O ₃ ) can be calculated by subjecting the catalyst to elemental analysis, determining the ratio of the iron (Fe) element, and converting this to Fe ₂ O ₃ .

The content of cerium (in terms of Ce element) in the catalyst of the present invention is 0.1 to 4.5 parts by weight, preferably 0.2 part by weight, per 100 parts by weight of the iron oxide (in terms of Fe ₂ O ₃ ). To 4 parts by weight, more preferably 0.3 to 3 parts by weight, still more preferably 0.4 to 2 parts by weight, particularly preferably 0.5 to 1.5 parts by weight. When the cerium content is within the above range, the affinity of the catalyst surface for the acid does not decrease, and the adsorption of the aldehyde to the catalyst surface can be suppressed. In addition, the affinity of the catalyst surface for the acid does not become too high, the acids react with each other, dimerization and decarboxylation can be performed, and the production of ketone and carbon dioxide can be suppressed. The content of cerium (in terms of Ce element) can be calculated from the ratio of cerium (Ce) element by elemental analysis of the catalyst.

The content of palladium (in terms of Pd element) in the catalyst of the present invention is, for example, 0.5 to 200 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the iron oxide (in terms of Fe ₂ O ₃ ). Parts by weight, more preferably 1.5 to 90 parts by weight, further preferably 1.7 to 85 parts by weight, particularly preferably 2.0 to 80 parts by weight. When the content of palladium is within the above range, sufficient catalytic activity is maintained, and high selectivity for aldehydes and the like is obtained. Palladium usually exists as an oxide such as PdO after calcination, but under a reducing atmosphere (for example, under an H ₂ atmosphere) for producing aldehydes or the like by hydrogenation from carboxylic acids, these oxides or the like are , And reduced to metal paraudium (Pd). In addition, the content (ratio) of palladium can be calculated from the palladium (Pd) element ratio by elemental analysis of the catalyst.

The catalyst of the present invention preferably contains 0.3 to ₃ parts by weight of cerium (in terms of Ce element) and 1.5 parts by weight of palladium (in terms of Pd element) based on 100 parts by weight of the iron oxide (in terms of Fe ₂ O ₃ ). To 90 parts by weight, more preferably 0.5 to 1.5 parts by weight of cerium (in terms of Ce element) and 2.0 to 80 parts by weight of palladium. When the content (ratio) is within the above range, successive hydrogenation reactions of aldehyde can be suppressed while maintaining sufficient catalytic activity, and a high selectivity of aldehydes and the like can be obtained.

  In the catalyst of the present invention, a carrier such as silica or the like may be coexisted, or a metal oxide such as germanium oxide, tin oxide, vanadium oxide, or zinc oxide may be contained, as long as the effects of the present invention are not impaired. it can. In addition, other metals such as platinum, copper, and gold may be contained in these metal oxides. The content of the metal oxide (excluding iron oxide) is, for example, about 0.1 to 50% by weight based on the entire catalyst of the present invention. The addition amount of the other metals (excluding cerium and palladium) is, for example, about 0.1 to 50% by weight based on the entire catalyst of the present invention.

  Although the shape of the catalyst of the present invention is not particularly limited, a pellet shape is preferable from the viewpoint that the catalyst activity is easily maintained, the handling is easy, and the reaction is easy to use. The pellet shape is, for example, a particle shape of about 1 to 10 mm, and may be a cylindrical shape having a diameter of about 1 to 10 mm and a height (length) of about 1 to 10 mm. In particular, when it is desired to selectively obtain aldehydes, which are intermediate products in the hydrogenation of carboxylic acids, the catalyst component is supported only on the surface of the inert carrier pellet to prevent the progress of the sequential reaction in the pores. Is preferred.

  The catalyst of the present invention has, for example, an effect of suppressing a aldehyde hydrogenation reaction that occurs sequentially as compared with the catalyst of Patent Document 1. The catalyst of the present invention has an increased amount of basic points on its surface, and has a higher affinity for acids. The amount of the basic point can be measured using a temperature-programmed desorption method (TPD) using carbon dioxide as a probe molecule.

[Catalyst production method]
The method for producing a catalyst of the present invention includes a step of preparing a dispersion or solution containing a catalyst component, a step of evaporating the dispersion or solution to dryness, and a step of calcining after evaporating to dryness. Examples of the catalyst component include a cerium component, a palladium component, and an iron component. The catalyst of the present invention can be produced by the method for producing a catalyst of the present invention.

Specifically, the method for producing a catalyst of the present invention is, for example, a method including the following steps (1) to (6).
(1) Step of preparing a dispersion or solution by adding and stirring a palladium component, an iron component, and a solvent (2) Step of heating the dispersion or solution prepared in (1), evaporating to dryness, and then drying (3) Step of adding a cerium component and a solvent and stirring to prepare a dispersion or solution (4) Step of impregnating the dispersion or solution prepared in (3) with the substance dried in (2) ( 5) Step of evaporating the product obtained in (4) to dryness, and drying it. (6) Step of baking after drying in (5).

  By the methods (1) to (6), a powdery catalyst is obtained as an oxide. For example, the iron component becomes iron oxide which is an oxide after firing. That is, the iron component is a precursor component that becomes iron oxide by firing. The evaporation to dryness and the drying in (2) and (5) may be performed at once without being separated.

  In (1), a palladium component and an iron component are added as catalyst components, and in (3), a cerium component is added as catalyst components. However, the catalyst components are added at once without adding them separately, and after evaporating to dryness, drying and calcining. You may do.

  Further, in the method for producing a catalyst of the present invention, an iron component, a cerium component, a palladium component, or the like may be supported on a carrier such as silicon dioxide (silica) or alumina. Specifically, a carrier such as silica or alumina is immersed in a solution or dispersion containing an iron component, a cerium component, a palladium component, etc. to impregnate the iron component, cerium, palladium, etc., and then the solution or dispersion is evaporated to dryness. It may be prepared by a method in which the catalyst is solidified, the obtained catalyst is dried under reduced pressure or normal pressure, dried, and calcined. According to this method, a powdery catalyst is obtained as an oxide. The iron component, the cerium component, and the palladium component each become an oxide after firing. In addition, impregnation with an iron component, a cerium component, a palladium component, and the like can be performed by a known and commonly used method.

  The compounding amount of a carrier such as silicon dioxide (silica) or alumina is, for example, 10 to 500 parts by weight, preferably 30 to 300 parts by weight, based on 100 parts by weight of the total amount of the metal compound used. Note that commercially available carriers such as silicon dioxide (silica) and alumina can be used. As silicon dioxide (silica), “Aerosil 200” manufactured by Nippon Aerosil Co., Ltd. can be used.

  The cerium component may be any compound (cerium compound) containing the cerium (Ce) element, which becomes the cerium in the catalyst, such as cerium (III) nitrate hexahydrate and cerium acetate monohydrate. be able to. The amount of the cerium component is, for example, 0.1 to 10% by weight, and preferably 0.5 to 8% by weight, based on the total amount (100% by weight) of the metal compound used. As the cerium component, a commercially available cerium component can be used, and one type can be used alone or two or more types can be used in combination.

  The palladium component may be a compound containing a palladium (Pd) element (palladium compound) that becomes the palladium in the catalyst, and includes palladium nitrate such as palladium nitrate (II) hydrate, palladium sulfate, palladium chloride, and the like. Palladium oxide, palladium acetate, or the like can be used. The amount of the palladium component is, for example, 0.5 to 50% by weight, and preferably 1.0 to 30% by weight, based on the total amount of the metal compound used (100% by weight). As the palladium component, a commercially available one can be used, and one kind can be used alone and two or more kinds can be used in combination.

  The iron component may be any compound (iron compound) containing an iron (Fe) element, and examples thereof include oxides such as iron oxide, nitrides such as iron nitride, and other iron compounds. Other iron compounds include iron nitrate such as iron (III) nitrate hexahydrate, iron chloride such as iron (III) chloride hexahydrate, and iron sulfate. The compounding amount of the iron component (iron compound) is, for example, 20 to 99% by weight, and preferably 40 to 95% by weight, based on the total amount (100% by weight) of the metal compound used. As the iron component, a commercially available iron component can be used, and one type can be used alone or two or more types can be used in combination. When using iron sulfate, it is necessary to add an alkaline precipitant such as ammonia to precipitate as an insoluble iron compound, and then sufficiently wash the precipitate with water to remove sulfate ions.

  Examples of the solvent include water, alcohol, toluene and the like, with water being preferred. Therefore, the dispersion or the solution is preferably an aqueous solution or an aqueous dispersion. The amount of the solvent used is not particularly limited as long as the added amount of the metal compound can be dispersed or dissolved, but is, for example, 100 to 5,000 parts by weight based on the total amount of the metal compound used (100 parts by weight). , Preferably 300 to 1000 parts by weight. In addition, since salts of the platinum group such as palladium are more easily precipitated than iron and other base metal salts, the presence of a chelating agent such as citric acid or EDTA in the dispersion or solution can also improve the catalytic activity. It is effective for The compounding amount of the chelating agent is, for example, 10 to 1000 parts by weight based on the solvent (100 parts by weight).

  The evaporation to dryness is performed, for example, at a temperature of 50 to 150 ° C. for 3 to 48 hours. The drying is performed, for example, at a temperature of 50 to 300 ° C. for 1 to 48 hours. The firing is performed at a temperature of, for example, 200 to 600 ° C. for 1 to 24 hours. These evaporation to dryness, drying and baking can be performed in an air atmosphere using a general electric furnace or the like. After calcination, the resulting powdery catalyst may be further tableted into a tablet shape, solidified and formed into a pellet shape, crushed, or classified with a mesh or the like.

[Production method of aldehydes]
The method for producing aldehydes of the present invention is a method for producing aldehydes by hydrogenation from carboxylic acids in the gas phase in the presence of the catalyst of the present invention. In the method for producing aldehydes of the present invention, hydrogenation is preferably performed using hydrogen (H ₂ ) gas.

  The carboxylic acids are organic acids having at least one carboxyl group in the molecule. Examples of the carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, and benzoic acid.

  The aldehydes are hydrocarbon compounds having at least one formyl group in the molecule. Examples of the aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butanal, pentanal, acrolein, benzaldehyde, and the like. In the method for producing aldehydes of the present invention, aldehydes corresponding to carboxylic acids as raw materials are obtained.

  In the method for producing aldehydes according to the present invention, the carboxylic acids are preferably acetic acid, the aldehydes are acetaldehyde, and the alcohols are preferably ethanol.

FIG. 1 is a schematic flow chart showing an example of the method for producing aldehydes of the present invention. In particular, FIG. 1 is a schematic flow chart when aldehydes are the main target.
In the example shown in FIG. 1, the hydrogen gas is supplied from the hydrogen facility P by a line 1, is pressurized by a compressor I-1, passes through a buffer tank J- 1, merges with the circulating gas of a line 2, The evaporator A (carboxylic acid evaporator) is charged. Carboxylic acids are supplied from the carboxylic acid tank K-1 to the evaporator A from the line 4 using the pump N-1, and the vaporized carboxylic acids are exchanged with hydrogen gas in heat exchangers (heaters) L-1 and L-. The mixture is heated in 2 and charged into the reactor B filled with the catalyst of the present invention from the line 5. The evaporator A is provided with a circulation pump N-2. In the reactor B, carboxylic acids are hydrogenated to produce aldehydes and alcohols as main products, non-condensable ketones such as methane, ethane, ethylene, carbon dioxide, and condensable acetone, and water. . In addition, hydrocarbons having 2 or more carbon atoms such as propylene, 1-butene, 1-pentene, and 1-hexene are generated.

Hydrogenation of carboxylic acids can be performed by a known method. For example, carboxylic acids are reacted with hydrogen in the presence of the catalyst of the present invention. Before the catalyst of the present invention is used for hydrogenation of carboxylic acids, it is preferable to carry out a reduction treatment in advance, for example, by bringing it into contact with hydrogen. The reduction treatment is performed, for example, by flowing hydrogen (H ₂ ) gas at 30 to 300 ml / min under the conditions of 50 to 500 ° C. and 0.1 to 5 MPa.

  The reaction temperature in the reactor is, for example, 250 to 400 ° C, preferably 270 to 350 ° C. If the reaction temperature is too high, by-products of ketones such as acetone increase, and the selectivity of aldehydes and the like tends to decrease. The reaction pressure in the reactor may be any of normal pressure, reduced pressure, and increased pressure, but is, for example, in the range of 0 to 10 MPa, preferably 0.1 to 3 MPa. The contact time in the reactor is, for example, 0.1 to 1 sec, and preferably 0.1 to 0.5 sec.

  The supply ratio (molar ratio) of hydrogen and carboxylic acids to the reactor is, for example, hydrogen / carboxylic acids = 0.5 to 50, preferably hydrogen / carboxylic acids = 2 to 25.

  The conversion of carboxylic acids in the reactor is, for example, 30 to 90%, preferably 40 to 85%, and more preferably 45 to 80%. In the method for producing aldehydes of the present invention, the sequential reaction can be suppressed even at a high conversion, so that the selectivity of aldehydes can be kept high and aldehydes can be produced with high yield.

  As described above, the reaction between carboxylic acids and hydrogen mainly causes unconverted carboxylic acids, unconverted hydrogen, aldehydes, alcohols, water, and other products (e.g., ethyl acetate and the like) formed in the reaction. A gaseous reaction product comprising carboxylic acids, ketones such as acetone) is obtained.

  A non-condensable gas and a condensable component can be separated from the gaseous reaction product, and the condensable component can be used as a reaction liquid. As a method for separating a non-condensable gas and a condensable component from the gaseous reaction product, for example, a reaction fluid obtained by hydrogenating carboxylic acids is charged into an absorption tower, and a condensed component in the reaction fluid is absorbed with an absorption liquid. There is a method of separating a condensable component and a non-condensable gas by absorption (absorption step). At least a part of the by-product hydrocarbon having 2 or more carbon atoms is absorbed by the absorbing solution. In the method for producing aldehydes of the present invention, the condensable component (a mixture of the condensable component and the absorbing solution) absorbed in the absorbing solution is also included in the “reaction solution”. In the absorption step, a part of the non-condensable gas dissolves in the absorption liquid. By providing a step of recycling the liquid after the release of the condensable gas to the absorption tower (dissipation step), hydrogen and other non-condensable gas components can be efficiently separated.

  In the absorption step, for example, a reaction fluid obtained by hydrogenating carboxylic acids is charged into an absorption tower, and a condensed component in the reaction fluid is absorbed by the absorption liquid, and a non-condensable gas is dissolved in the absorption liquid. This absorption step is usually performed by supplying the reaction fluid and the absorption liquid obtained in the reaction step to the absorption tower and bringing them into contact in the absorption tower. The absorption tower is not particularly limited, and a known or well-known gas absorption apparatus, for example, a packed tower, a tray tower, a spray tower, a wet wall tower, or the like can be used.

  Further, in the evaporating step, the pressure of the bottom liquid in the absorption tower is reduced to evaporate the non-condensable gas dissolved in the absorption liquid, and the liquid after the non-condensable gas is evolved is recycled to the absorption tower. In this dispersion step, the bottom liquid of the absorption tower obtained in the absorption step (absorbed liquid after absorbing and dissolving the condensed components and non-condensable gas) is usually supplied to the reduced-pressure dispersion tower, and the non-condensation is performed. This is performed by releasing a volatile gas. The stripping tower is not particularly limited, and a known or well-known gas stripping apparatus, for example, a packed tower, a plate tower, a spray tower, a wet wall tower, a gas-liquid separator, or the like can be used.

  In the example shown in FIG. 1, the reaction fluid flowing out of the reactor B passes through the heat exchanger L-1 via the line 6 and is cooled by the heat exchangers (coolers) M-1 and M-2. The lower part of the absorption tower C is charged. In the absorption tower C, a bottom liquid of a diffusion tower D to be described later (hereinafter sometimes referred to as “circulating liquid”) is charged from the line 9 as an absorption liquid. The circulating fluid mainly absorbs and dissolves non-condensable gases such as hydrogen, methane, ethane, ethylene and carbon dioxide. Further, as an absorbing liquid other than the circulating liquid (hereinafter sometimes referred to as “absorbing tower replenishing liquid”), a distilling upper phase liquid containing a large amount of an azeotropic solvent (a solvent azeotropic with water) from line 11 is used as the absorbing liquid. It may be charged as. The absorption tower replenisher absorbs aldehydes, which are condensable components having a low boiling point, together with non-condensable gas. The distillate upper phase liquid is supplied to the line 11 through the line 15 and the cooler M-3. The positions where the bottoms (line 9) (circulating liquid) and the upper phase liquid (line 11) (replenisher of the absorption tower) of the stripping tower D are charged into the absorption tower C are determined by absorption of aldehydes and non-condensable gas. Although it can be appropriately selected in consideration of efficiency and the like, it is preferable that the circulating liquid is charged into the middle part of the absorption tower C, and the absorption tower replenishment liquid is charged into the upper part of the absorption tower C.

  The bottom liquid of the absorption tower C is divided into a line 14 provided to the reaction liquid tank K-2 and a line 8 charged to the stripping tower D. The bottom liquid in the line 14 is stored in the reaction liquid tank K-2 as a reaction liquid. If necessary, the stored reaction liquid may be subjected to a purification step. The line 8 is decompressed in the stripping tower D, and hydrogen, methane, ethane, ethylene, and carbon dioxide, which are non-condensable gases dissolved in the absorbent, are released from the line 10. It is recycled to absorption tower C. Q-2 is a vent.

  As the absorbing liquid charged into the absorption tower C, only the bottom liquid (circulating liquid) of the absorption tower C may be used. Absorbents that do not contain acetaldehyde are preferred. For example, as the absorbing solution, in addition to the azeotropic solvent-containing solution used when separating unreacted carboxylic acids and by-produced water by azeotropic distillation, aldehydes were separated from the bottom of the absorption tower C. An aqueous solution of acetic acid, such as the latter solution, is preferred.

  When the azeotropic solvent-containing liquid is used as the absorbing liquid, the azeotropic solvent content in the azeotropic solvent-containing liquid is, for example, 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and still more preferably. Is 75% by weight or more.

  The azeotropic solvent forms an azeotropic mixture with water to lower the boiling point, and facilitates separation of carboxylic acids and water by liquid separation with water. Examples of azeotropic solvents include, as esters, isopropyl formate, propyl formate, butyl formate, isoamyl formate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, Examples of isopropyl butyrate include ketones such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diethyl ketone, and ethyl propyl ketone; examples of aliphatic hydrocarbons include pentane, hexane, and heptane; and examples of alicyclic hydrocarbons include , Cyclohexane, methylcyclohexane, dimethylcyclohexane and the like, and aromatic hydrocarbons such as benzene and toluene.

Among them, ethyl acetate is preferred as an azeotropic solvent because it can easily be present as a by-product of hydrogenation of carboxylic acids and can omit the step of recovering the azeotropic solvent.
In addition, propyl acetate (boiling point 102 ° C.), isobutyl acetate (boiling point 117 ° C.), sec-butyl acetate (boiling point 112 ° C.), isopropyl propionate (boiling point 110 ° C.), methyl butyrate (boiling point 102 ° C.), ethyl isobutyrate (boiling point Esters having a boiling point of 100 ° C. to 118 ° C. at normal pressure (eg, 110 ° C.) have a higher ratio of water in an azeotropic mixture with water and have a lower boiling point than acetic acid, so that separation of carboxylic acids and water is easier. To In addition, these esters do not azeotrope with ethanol or have a low ratio of ethanol in an azeotrope with ethanol, so that separation and recovery of the azeotropic solvent are relatively easy. Therefore, an ester having a boiling point at normal pressure of 100 ° C. to 118 ° C. is also preferable as the azeotropic solvent.

  In addition, methane, which is likely to be present as a non-condensable gas, is more soluble in an azeotropic solvent having a lower polarity than an aqueous acetic acid solution having a higher polarity. Therefore, the azeotropic solvent is suitable for an absorbent for a non-condensable gas.

  The ratio (weight ratio) between the supply amount of the absorption tower replenisher (line 11) and the supply amount of the reaction fluid (line 7) supplied to the absorption tower C is, for example, the former / the latter = 0.1-10. , Preferably the former / latter = 0.3-2. The ratio (weight ratio) between the amount of the circulating liquid (line 9) supplied to the absorption tower C and the supply amount of the reaction fluid (line 7) is, for example, the former / the latter = 0.05 to 20, Preferably, the former / the latter = 0.1 to 10.

  The number of stages (theoretical stages) of the absorption tower C is, for example, 1 to 20, preferably 3 to 10. The temperature in the absorption tower C is, for example, 0 to 70 ° C., and the pressure in the absorption tower C is, for example, 0.1 to 5 MPa (absolute pressure).

  The temperature in the stripping tower D is, for example, 0 to 70 ° C. The pressure in the stripping tower D may be lower than the pressure in the absorption tower C, and is, for example, 0.05 to 4.9 MPa (absolute pressure). The difference between the pressure of the absorption tower C and the pressure of the stripping tower D (the former-the latter) can be appropriately selected from the viewpoint of the efficiency of non-condensable gas emission and the suppression of loss of aldehydes, for example, 0.05 to 4.9 MPa. , Preferably 0.5 to 2 MPa.

  Even when the conversion exceeds 40%, reduction of the generated aldehydes to alcohols is suppressed, and a high selectivity can be maintained. Therefore, aldehydes can be produced with high yield. The selectivity of aldehydes in the method for producing aldehydes of the present invention varies depending on reaction conditions, but is, for example, 30 to 90%, preferably 40 to 90%. The selectivity and yield of the aldehydes can be determined by analyzing the reaction solution by gas chromatography or the like.

  The purity of the aldehydes obtained by the method for producing aldehydes of the present invention is, for example, 90.0% by weight or more, preferably 95.0% by weight or more, and more preferably 98.0% by weight or more. . In addition, the obtained aldehydes can be further purified by distillation or the like, if necessary, to further increase the purity.

  Since the method for producing aldehydes of the present invention uses the catalyst of the present invention, it has an effect of suppressing the formation of hydrocarbons having 2 or more carbon atoms by-produced. The selectivity of the hydrocarbon having 2 or more carbon atoms is, for example, 15% or less, and preferably 10% or less. In addition, by adjusting the reaction conditions as described above, aldehydes and the like can be selectively produced, so that ketones such as acetone produced by another side reaction and gases such as carbon dioxide, carbon monoxide, and methane are produced. Occurrence can also be suppressed. The selectivity of ketones such as acetone is, for example, 10% or less, and preferably 5% or less. The selectivity for gases such as carbon dioxide, carbon monoxide, and methane is, for example, 10% or less, and preferably 5% or less.

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. The content of palladium (Pd) is an amount converted to palladium (Pd) element, and the content of cerium (Ce) is an amount converted to cerium (Ce) element. Further, the composition ratio of palladium (Pd) or cerium (Ce) charged to the catalyst is a weight ratio to 100 parts by weight of iron oxide (Fe ₂ O ₃ ).

(Evaluation of catalyst reactivity 1)
1.0 cc of the catalyst was charged into a 12 mmφ SUS reaction tube connected to a fixed-bed gas-phase continuous flow reactor (reactor), and the temperature of the catalyst layer was reduced to 300 ° C. by an electric furnace under a hydrogen gas flow of 100 mL / min. Pretreatment was performed by heating for 12 hours.
After performing the above pretreatment, a hydrogen gas (200 mL / min) and an acetic acid solution (0.2 mL) were used so that the contact time was 0.25 sec and the molar ratio of hydrogen / acetic acid (H ₂ / AC) was 5.0. (103 cc / min) was passed through the reactor to react. The gas at the outlet of the reactor was cooled by a cooler, gas-liquid separated, and a condensate was collected. Low-boiling components such as acetaldehyde in non-condensable gas were collected by bubbling into 300 cc of water, and non-collected gas components were collected in a gaseous state. During the reaction, the electric furnace and the back pressure valve were adjusted so that the catalyst layer temperature was 315 ° C. and the reaction pressure was 0.4 MPa. After a lapse of 12 hours or more from the start of the reaction, the condensate, trap liquid, and gas after the cooler were collected for a predetermined time, and quantitative analysis and composition analysis were performed.
The composition was analyzed using a gas chromatograph and a Karl Fischer moisture meter.

Comparative Example 1 (Preparation of catalyst (A))
In 20 mL of water, 25.00 g of iron (III) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.), 0.25 g of palladium (II) hydrate (manufactured by Johnson Matthey) and citric acid (Wako Pure Chemical Industries, Ltd.) 1.07 g (manufactured by Yakuhin Kogyo Co., Ltd.) was added and stirred until dissolved. The resulting solution was dried in a water bath at 80 ° C. until there was no more water, dried at 110 ° C. for 24 hours, and calcined at 400 ° C. for 5 hours to obtain an oxide. This oxide was tabletted and hardened after being crushed, and classified by 7-10 mesh to obtain a catalyst (A).
This catalyst (A) contained 2.0 parts by weight of palladium (Pd).

Example 1 (Preparation of catalyst (B))
0.15 g of cerium nitrate hexahydrate (manufactured by Kanto Chemical Co., Ltd.) was added to 5 mL of water, and the mixture was stirred until dissolved. The obtained solution was immersed in 5.00 g of the oxide prepared in Comparative Example 1, dried in a hot water bath at 80 ° C. until there was no more water, dried at 110 ° C. for 24 hours, and calcined at 400 ° C. for 5 hours. An oxide was obtained. This oxide was tabletted, hardened after being crushed, and classified by 7-10 mesh to obtain a catalyst (B).
The catalyst (B) contained 2.0 parts by weight of palladium (Pd) and 1.0 part by weight of cerium (Ce).

Comparative Example 2 (Preparation of catalyst (C))
A catalyst (C) was obtained in the same manner as in Example 1, except that the amount of cerium nitrate hexahydrate was changed to 0.75 g.
The catalyst (C) contained 2.0 parts by weight of palladium (Pd) and 5.0 parts by weight of cerium (Ce).

Comparative Example 3 (Preparation of catalyst (D))
A catalyst (D) was obtained in the same manner as in Comparative Example 1, except that the amount of palladium (II) nitrate hydrate was 5.02 g and the amount of citric acid was 21.32 g.
This catalyst (D) contained 40.0 parts by weight of palladium (Pd).

Example 2 (Preparation of catalyst (E))
A catalyst (E) was obtained in the same manner as in Example 1 except that the oxide prepared in Comparative Example 3 was used instead of the oxide prepared in Comparative Example 1, and the amount of cerium nitrate was 0.11 g.
This catalyst (E) contained 40 parts by weight of palladium (Pd) and 1.0 part by weight of cerium (Ce).

Example 3 (Preparation of catalyst (F))
A catalyst (F) was obtained in the same manner as in Example 2, except that the amount of cerium nitrate hexahydrate was changed to 0.33 g.
The catalyst (F) contained 40 parts by weight of palladium (Pd) and 3.0 parts by weight of cerium (Ce).

Comparative Example 4 (Preparation of catalyst (G))
A catalyst (G) was obtained in the same manner as in Comparative Example 1, except that the amount of palladium (II) nitrate hydrate was changed to 10.04 g and the amount of citric acid was changed to 42.64 g.
This catalyst (G) contained 40 parts by weight of palladium (Pd).

Example 4 (Preparation of catalyst (H))
A catalyst (H) was obtained in the same manner as in Example 1, except that the oxide prepared in Comparative Example 4 was used instead of the oxide prepared in Comparative Example 1, and the amount of cerium nitrate was changed to 0.09 g.
This catalyst (H) contained 80 parts by weight of palladium (Pd) and 1.0 part by weight of cerium (Ce).

  Table 1 below shows the evaluation results of the reactivity evaluations 1 of the catalysts (A) to (H) obtained in Examples 1 to 4 and Comparative Examples 1 to 4. The "hydrogenation" selectivity in the table is the sum of the selectivities of acetaldehyde, ethanol, ethyl acetate, and acetal generated through the acetic acid hydrogenation reaction, and the "ketonization" selectivity is the acetic acid ketonization reaction. Is the sum of the selectivities of acetone and carbon dioxide generated by the reaction, and the “decomposition + FT” selectivity is the selectivity of carbon monoxide, methane, ethane, ethylene, propane and propylene generated through decomposition of acetic acid and Fischer-Tropsch reaction. The “Etc” selectivity is the sum of the selectivities of other trace by-products.

(Evaluation of catalyst reactivity 2)
1.0 cc of the catalyst was charged into a 12 mmφ SUS reaction tube connected to a fixed-bed type gas-phase continuous flow reactor (reactor), and the temperature of the catalyst layer was reduced to 300 ° C. by an electric furnace under a flow of 100 mL / min of hydrogen gas. Pretreatment was performed by heating for 12 hours.
After performing the above pretreatment, hydrogen gas and hydrogen gas are mixed so that the contact time is a predetermined value in the range of 0.25 to 1.0 sec, and the molar ratio of hydrogen / acetic acid (H ₂ / AC) is 5.0. The acetic acid solution was allowed to react by flowing through the reactor. The gas at the outlet of the reactor was cooled by a cooler, gas-liquid separated, and a condensate was collected. Low-boiling components such as acetaldehyde in non-condensable gas were collected by bubbling into 300 cc of water, and non-collected gas components were collected in a gaseous state. During the reaction, the electric furnace and the back pressure valve were adjusted so that the catalyst layer temperature was a predetermined value in the range of 300 to 330 ° C. and the reaction pressure was a predetermined value in the range of 0.0 to 0.4 MPa. After a lapse of 12 hours or more from the start of the reaction, the condensate, trap liquid, and gas after the cooler were collected for a predetermined time, and quantitative analysis and composition analysis were performed.
The composition was analyzed using a gas chromatograph and a Karl Fischer moisture meter.

  With respect to the catalysts (E), (F), and (D) obtained in Examples 2 and 3 and Comparative Example 3, evaluation results of the reactivity evaluation 2 of the catalyst are shown in FIG. FIG. 3 shows the evaluation results of the reactivity evaluation 2 of the catalysts (H) and (G) obtained in Example 4 and Comparative Example 4. “Hydride” on the horizontal axis in FIGS. 2 and 3 means a generic term for acetaldehyde, ethanol, ethyl acetate, and acetal generated through the hydrogenation reaction of acetic acid.

  Generally, when the hydride yield increases, the acetaldehyde concentration in the reaction gas increases, and acetaldehyde is successively hydrogenated and converted into ethanol, so that the acetaldehyde concentration in the hydride tends to decrease. In Comparative Example 3 of FIG. 2 and Comparative Example 4 of FIG. 3, it can be seen that the selectivity of acetaldehyde is greatly reduced as the hydride yield increases. On the other hand, in Examples 2 and 3 in FIG. 2, it can be seen that the decrease in acetaldehyde selectivity as the hydride yield increases as compared to Comparative Example 3. In addition, in Example 4 of FIG. 3, similarly, it can be seen that a decrease in acetaldehyde selectivity as the hydride yield increases as compared with Comparative Example 4 is suppressed. From the above, it can be seen that in the present invention, even if the successive hydrogenation reaction of acetaldehyde is suppressed and the acetaldehyde yield increases, a high acetaldehyde selectivity can be achieved.

A Evaporator B Reactor C Absorption tower D Dispersion tower I-1 to I-2 Compressor J-1 to J-3 Buffer tank K-1 Carboxylic acid tank K-2 Reaction liquid tank L-1 to L-2 Heater M-1 to M-4 cooler (cooler)
N-1 to N-3 pump (liquid sending pump)
P hydrogen equipment (hydrogen cylinder)
Q-1 to Q-2 vent 1 to 15 lines

Claims (6)

A catalyst for producing aldehydes by hydrogenation from carboxylic acids, containing cerium, palladium and iron oxide, wherein the content of cerium (in terms of Ce element) is 100 parts by weight of iron oxide (in terms of Fe ₂ O ₃ ) Catalyst in an amount of 0.1 to 4.5 parts by weight, Palladium content of (Pd element equivalent), relative to iron oxide (Fe ₂ O ₃ equivalent) 100 parts by weight, the catalyst according to claim 1 which is 1 to 100 parts by weight.   The catalyst according to claim 1 or 2, which is in the form of a pellet.   The catalyst according to any one of claims 1 to 3, comprising a step of preparing a dispersion or solution containing a catalyst component, a step of evaporating the dispersion or solution to dryness, and a step of calcining after evaporating to dryness. Manufacturing method.   A method for producing aldehydes, comprising producing aldehydes by hydrogenation from carboxylic acids in the gas phase in the presence of the catalyst according to claim 1.   The method for producing an aldehyde according to claim 5, wherein the carboxylic acid is acetic acid, and the aldehyde is acetaldehyde.

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