JP5931781B2 - Method for producing conjugated diene - Google Patents

Description

  The present invention relates to a method for producing a conjugated diene by intramolecular dehydration of vicinal diol.

  Conjugated dienes such as 1,3-butadiene, which is a raw material for synthetic rubber, and isoprene, which is a raw material for terpenes or polyisoprene rubber, are generally produced through naphtha decomposition. However, in recent years, depletion of fossil resources represented by crude oil has been regarded as a problem. Against this background, attempts to produce conjugated dienes using biomass, which is a typical non-naphtha raw material, have become active. One of these causes vicinal diols such as 2,3-butanediol or 2-methyl-2,3-butanediol obtained by fermentation of biomass to undergo an intramolecular dehydration reaction in the presence of a specific dehydration catalyst. This is a method for producing butadiene or isoprene (Patent Documents 1 to 5). However, the intramolecular dehydration reaction efficiency using the dehydration catalyst disclosed in these prior arts (Patent Documents 1 and 2) is still not sufficient from the viewpoint of industrial production, and there is room for improvement.

Japanese Patent Publication 54-9148 JP-A-50-115686 US2012 / 0252082A CN10158462A KR10-2012-0096125

  The problem to be solved by the present invention is to provide a method for industrially advantageously producing a conjugated diene by improving the results of the intramolecular dehydration reaction of vicinal diol as described above.

That is, the present invention
The present invention relates to a method for producing a conjugated diene by intramolecular dehydration of vicinal diol and producing a conjugated diene using a rare earth element pyrophosphate as a catalyst.
In the production method of the present invention, the rare earth element is preferably a lanthanoid.

Furthermore, in the production method of the present invention, the rare earth element is preferably selected from lanthanum and cerium.
The production method of the present invention is preferably carried out using a fixed bed flow reactor.

  In the present invention, the vicinal diol is preferably 2,3-butanediol or 2-methyl-2,3-butanediol, and the conjugated diene to be produced is preferably butadiene or isoprene, respectively.

  Excellent yield of conjugated diene obtained by intramolecular dehydration reaction of vicinal diol.

The present invention will be described in detail below.
The present invention is a method for producing a conjugated diene using a rare earth element pyrophosphate as a dehydration catalyst in a method for producing a conjugated diene by intramolecular dehydration of vicinal diol.

  A vicinal diol means a diol in which one hydroxyl group is bonded to each of two adjacent carbon atoms. The total carbon number of the vicinal diol is an aliphatic diol usually in the range of 4-20. The preferred total carbon number is in the range of 4 to 10, particularly preferably 4 or 5. The preferred vicinal diol in the production method of the present invention is 2,3-butanediol or 2-methyl-2,3-butanediol.

  The dehydration catalyst according to the present invention is a pyrophosphate of a rare earth element. Here, the rare earth element specifically includes scandium, yttrium, and metals belonging to lanthanoids, that is, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Can be mentioned. In the present invention, among the rare earth elements, lanthanoids are preferable, and lanthanum (La) or cerium (Ce) is more preferable from the viewpoint of reaction results.

  The dehydration catalyst according to the present invention only needs to contain a pyrophosphate salt of one or more elements selected from rare earth elements, and the equivalent ratio of rare earth elements to phosphorus elements in the catalyst is (rare earth element) / (phosphorus element) The range of 2/6 to 6/6 is preferable, and the range of 3/6 to 5/6 is more preferable.

  The rare earth element pyrophosphate can be prepared by various methods. For example, lanthanum pyrophosphate is precipitated as a precipitate of lanthanum pyrophosphate by adding a sodium pyrophosphate or potassium pyrophosphate aqueous solution as a pyrophosphoric acid source to a heated lanthanum trichloride aqueous solution. Then, after aging, it can be prepared by filtration, washing with water, drying and baking. The concentration of the pyrophosphoric acid source aqueous solution is preferably 1 to 50 wt%, more preferably 5 to 40 wt%. The temperature of the aqueous solution of the pyrophosphate source to be added is preferably maintained at 40 to 99 ° C. More preferably, the temperature is maintained at 50 to 95 ° C. In order to control the pH of the supernatant after aging, a base such as sodium hydroxide or potassium hydroxide can be added in advance to the aqueous solution of the pyrophosphate source. The present inventors have found that controlling the pH of the supernatant after the aging step in the range of 4 to 9, preferably 5 to 8, is the key to improving the reaction performance. When the pH after aging is low, the selectivity of the conjugated diene is poor, and when the pH is high, the activity is low. The pH control may be performed at any stage until the filtration stage.

  The rare earth element source can be used in any form as long as it is water-soluble, but rare earth element chlorides, nitrates, and acetates are preferably used. The concentration of such an aqueous solution of rare earth element salt is preferably 1 to 50 wt%, more preferably 2 to 40 wt%. It is preferable to maintain the liquid temperature of the aqueous solution at 40 to 99 ° C. until aging is completed. More preferably, the temperature is maintained at 60 to 95 ° C.

  Aging is preferably maintained at the same temperature as during precipitation. The aging time is preferably 10 minutes to 24 hours, more preferably 30 minutes to 20 hours.

  Sodium hydroxide, potassium hydroxide and other bases used for pH control during catalyst preparation and sodium, potassium, etc. contained in the pyrophosphoric acid source may remain to some extent even after washing with water, but catalyst performance will remain if much remains. Therefore, the concentration of the alkali element such as sodium or potassium in the catalyst is preferably controlled in the range of 0.001 to 2 wt% by washing with water. Washing with water is performed using 10 to 1000 parts by weight, preferably 30 to 300 parts by weight of ion-exchanged water per 100 parts by weight of the precipitate. The number of washings may be any number as long as it is one or more, but the process is preferably shortened in terms of cost, and is preferably within 5 times. The water washing method may be a batch method or a continuous method.

  The drying may be performed under reduced pressure or normal pressure, and is preferably performed at a temperature in the range of 20 to 200 ° C. for 1 to 24 hours. Moreover, baking is performed in 300-700 degreeC, Preferably it is 400-600 degreeC. The firing time is preferably in the range of 30 minutes to 24 hours, more preferably 1 to 20 hours. As an atmosphere during firing, air or an inert gas such as nitrogen, argon, carbon dioxide, or the like is used.

  Any shape of the catalyst can be used, and examples thereof include powder, granules, pellets, and spheres. Any size can be used as long as the reactor can be filled.

  The reaction mode of the intramolecular dehydration reaction of the present invention is not particularly limited, but a gas phase flow reaction is particularly preferable. As a catalyst filling method, various methods such as a fixed bed, a fluidized bed, and a suspension bed are adopted, and any method may be used, but a fixed bed is preferably adopted. When the intramolecular dehydration reaction of the present invention is performed in the gas phase, the raw material vicinal diol may be supplied to the reactor as it is or may be supplied in a form diluted with an inert gas. . An inert gas such as nitrogen, carbon dioxide, helium, and argon can be used as the diluent gas. The concentration of the diluent gas is in the range of 1 to 99.9 mol%, preferably in the range of 10 to 99.5 mol%. More preferably, it is 20 to 99% of range. The concentration of vicinal diol is in the range of 0.1 to 99 mol%, preferably in the range of 0.5 to 90 mol%, more preferably in the range of 1 to 80 mol%.

The intramolecular dehydration temperature is 200 to 600 ° C, preferably 250 to 550 ° C, more preferably 300 to 500 ° C. The reaction pressure can be reacted in the range of normal pressure to 2 MPa. The weight hourly space velocity (WHSV) indicating the weight ratio of the raw material supply amount to the catalyst charged in the reactor is in the range of 0.1 to 5, preferably 0.2 to 3 (hr ⁻¹ ).

Next, the intramolecular dehydration reaction of the present invention using 2,3-butanediol as the vicinal diol and the rare earth pyrophosphate as the catalyst will be described in detail by way of examples. The present invention is not limited to the examples.
Raw materials and catalyst [2,3-butanediol]
2,3-butanediol was manufactured by Tokyo Chemical Industry.

[Lanthane pyrophosphate (La ₄ (P ₂ O ₇ ) ₃ )]
A 300 ml round bottom flask was charged with 80 ml of ion-exchanged water, and 8.9 g of lanthanum chloride heptahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved to prepare an aqueous solution, which was heated to 80 to 90 ° C. (solution A) ). To a 50 ml beaker, add 16 ml of ion-exchanged water, 8.0 g of sodium pyrophosphate decahydrate (manufactured by Wako Pure Chemical Industries) and 1.06 g of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade) while heating to 80-90 ° C. An aqueous solution was prepared by dissolution (solution B). The solution B was gradually added dropwise to the solution A to precipitate a lanthanum pyrophosphate precursor. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 7.7. After filtration, the precipitate is washed with 80 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Cerium pyrophosphate (Ce ₄ (P ₂ O ₇ ) ₃ )]
In a 300 ml round bottom flask, 60 ml of ion-exchanged water was added, and 6.7 g of cerium chloride heptahydrate (manufactured by Wako Pure Chemical Industries) was added and dissolved to prepare an aqueous solution, which was heated to 80 to 90 ° C. (A liquid). An aqueous solution was prepared by adding 12 ml of ion-exchanged water, 6.0 g of sodium pyrophosphate decahydrate and 0.8 g of sodium hydroxide to a 50 ml beaker and dissolving at 80 to 90 ° C. while heating (B solution). Liquid B was gradually added dropwise to liquid A to precipitate a cerium pyrophosphate precursor. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 7.2. After filtration, the precipitate is washed with 60 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Neodymium pyrophosphate (Nd ₄ (P ₂ O ₇ ) ₃ )]
A 300 ml round bottom flask was charged with 60 ml of ion exchanged water, and 6.5 g of neodymium chloride hexahydrate (Aldrich) was added and dissolved to prepare an aqueous solution, which was heated to 80 to 90 ° C. (solution A) ). In a 50 ml beaker, 12 ml of ion-exchanged water, 6.0 g of sodium pyrophosphate decahydrate and 0.8 g of sodium hydroxide were added and dissolved while heating at 80 to 90 ° C. to prepare an aqueous solution (Liquid B). The solution B was gradually added dropwise to the solution A to precipitate a precursor of neodymium pyrophosphate. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 7.7. After filtration, the precipitate is washed with 60 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Samarium pyrophosphate (Sm ₄ (P ₂ O ₇ ) ₃ )]
A 300 ml round bottom flask was charged with 160 ml of ion exchanged water, 7.2 g of samarium acetate tetrahydrate (manufactured by Mitsuwa Chemicals) was added and dissolved to prepare an aqueous solution and heated to 80 to 90 ° C. ( A liquid). In a 50 ml beaker, 12 ml of ion-exchanged water, 6.0 g of sodium pyrophosphate decahydrate and 0.4 g of sodium hydroxide were added and dissolved while heating at 80 to 90 ° C. to prepare an aqueous solution (Liquid B). The solution B was gradually added dropwise to the solution A to precipitate a samarium pyrophosphate precursor. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 5.8. After filtration, the precipitate is washed with 60 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Yttrium pyrophosphate (Y ₄ (P ₂ O ₇ ) ₃ )]
A 300 ml round bottom flask was charged with 60 ml of ion exchange water, and 5.5 g of yttrium chloride hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved to prepare an aqueous solution, which was heated to 80 to 90 ° C. (A liquid). In a 50 ml beaker, 12 ml of ion-exchanged water, 6.0 g of sodium pyrophosphate decahydrate and 0.7 g of sodium hydroxide were added and dissolved while heating at 80 to 90 ° C. to prepare an aqueous solution (Liquid B). The solution B was gradually added dropwise to the solution A to precipitate a samarium pyrophosphate precursor. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 7.1. After filtration, the precipitate is washed with 60 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Trilithium sodium pyrophosphate (Li ₃ NaP ₂ O ₇ ]]
It was prepared with reference to Example 1 of Patent Document 1 (Japanese Patent Publication No. 54-9148). In a 500 ml round bottom flask, 6.36 g of lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) and 200 ml of ion-exchanged water were dissolved, dissolved, and heated to 95 ° C. (solution A). In a 200 ml beaker, 50 ml of ion exchange water and 22.3 g of sodium pyrophosphate decahydrate were added and dissolved by heating at 95 ° C. (solution B). Liquid B was dropped into liquid A and precipitated, and then cooled to 20 ° C. Thereafter, filtration was performed, and the precipitate was washed with 100 ml of methanol. 110 ° C., 18 h dried, 500 ° C., 2 h fired, molded with a tablet machine and then crushed to a particle size of 0.2 to 0.8 mm.

[Calcium pyrophosphate (Ca ₂ P ₂ O ₇ )]
It was prepared using calcium chloride with reference to Example 1 of Patent Document 2 (Japanese Patent Laid-Open No. 50-115686). In a 300 ml round bottom flask, 4.0 g of calcium chloride (manufactured by Kanto Chemical Co., Ltd., special grade) and 80 ml of ion exchange water were added and dissolved, and heated to 95 ° C. (solution A). In a 50 ml beaker, 16 ml of ion exchange water and 8.0 g of sodium pyrophosphate decahydrate are added and dissolved by heating at 95 ° C. (solution B). Liquid B was dropped into liquid A and precipitated, and then cooled to 20 ° C. Thereafter, the mixture was filtered, and the precipitate was washed with 80 ml of water and filtered. 110 ° C., 18 h dried, 500 ° C., 2 h fired, molded with a tablet machine and then crushed to a particle size of 0.2 to 0.8 mm.

[Lantan phosphate (LaPO ₄ )]
For comparison with lanthanum pyrophosphate, lanthanum phosphate was prepared by the following method. An aqueous solution was prepared by adding 80 ml of ion-exchanged water and 8.9 g of lanthanum chloride heptahydrate to a 300 ml round bottom flask to prepare an aqueous solution and heated to 80 to 90 ° C. (solution A). In a 50 ml beaker, 16 ml of ion exchange water, 3.4 g of disodium hydrogen phosphate (Kanto Chemical, special grade) and 1.2 g of sodium hydroxide were added and dissolved while heating at 80 to 90 ° C. to prepare an aqueous solution (Liquid B). B liquid was gradually dripped at A liquid, and the precursor of lanthanum phosphate was precipitated. While stirring, the temperature was maintained at 80 to 90 ° C. for 2 hours, and then cooled to 20 ° C. The pH of this suspension was 6.9. After filtration, the precipitate is washed with 80 ml of ion-exchanged water, and after filtration, dried at 110 ° C. for 18 hours, baked at 500 ° C. for 2 hours, molded by a tablet molding machine, and crushed to a particle size of 0.2 to 0.8 mm. Aligned.

[Evaluation method of reaction results]
The product was analyzed using an FID gas chromatograph, and the conversion rate of 2,3-butanediol and the selectivity of the product were calculated on a carbon atom basis.

  The reaction that reaches the target butadiene (C) by the intramolecular dehydration reaction of 2,3-butanediol (A) is a reaction via 3-buten-2-ol (B) as an intermediate. In the present invention, the raw material conversion C and the reaction selectivity S are defined as follows.

[Reaction method]
The catalytic activity of the catalyst was evaluated by the following reaction method unless otherwise specified.

After charging 2.0 g of the catalyst obtained above into a 3/8 inch reaction tube, the reaction tube was heated in a tubular electric furnace in a nitrogen stream, and after the catalyst layer reached a predetermined temperature, nitrogen, and 2, A predetermined amount of 3-butanediol was supplied, and the reaction was performed at normal pressure and a reaction temperature of 350 ° C. The results are shown in Table 1. In the present invention, WHSV (space velocity based on catalyst weight) is defined by the following equation.
WHSV (hr ⁻¹ ) = 2,3-butanediol flow rate (g / hr) / catalyst (g)

[Examples 1-5, Comparative Examples 1-3]
Activity evaluation was performed using the catalysts described in Table 1 under the conditions of WHSV of 0.5 hr ⁻¹ , reaction temperature of 350 ° C., and 2,3-butanediol: N ₂ = 1: 39 (molar ratio). The results are shown in Table 1.

  As can be seen from the above table, Examples 1 to 5 using rare earth element pyrophosphates as dehydration catalysts show high raw material conversion and good reaction selectivity, while alkali metal or alkaline earth metal pyrroline. In the system using an acid salt as a catalyst, both the conversion rate and the selectivity are low. Also, from the comparison of the selectivity between Example 1 and Comparative Example 3, it is clear that the anion portion constituting the catalyst gives far superior reaction results for the pyrophosphate anion compared to the phosphate anion.

  The intramolecular dehydration reaction of the vicinal diol of the present invention makes it possible to efficiently obtain a conjugated diene.

Claims (5)

  A method for producing a conjugated diene using a rare earth element pyrophosphate as a catalyst in a method for producing a conjugated diene by intramolecular dehydration of vicinal diol. 2. The method for producing a conjugated diene according to claim 1, wherein the rare earth element is a lanthanoid.   The method for producing a conjugated diene according to claim 2, wherein the rare earth element is selected from lanthanum and cerium.   A method for producing a conjugated diene according to any one of claims 1 to 3, wherein a fixed bed flow reactor is used.   The method for producing a conjugated diene according to any one of claims 1 to 4, wherein the vicinal diol is 2,3-butanediol or 2-methyl-2,3-butanediol.