Synthesis method of 4-hydroxybutyraldehyde

Abstract

The invention provides a synthetic method of 4-hydroxybutyraldehyde, and belongs to the technical field of chemical synthesis. The synthesis method of the 4-hydroxybutyraldehyde comprises the following steps: dissolving allyl alcohol, a rhodium catalyst, a phosphorus ligand and a reaction aid in a solvent to form a homogeneous solution, and carrying out hydroformylation reaction on the homogeneous solution under the condition of introducing synthesis gas to prepare the 4-hydroxybutyraldehyde, wherein in the structural general formula of the reaction aid, R1 and R2 are the same or different and are respectively and independently selected from any one of H, C1-C12 saturated alkyl, cycloalkyl or aryl. According to the present invention, the raw material composition does not need to be strictly controlled, and the reaction auxiliary agent only needs to be introduced, such that the activity of the catalyst and the selectivity of the 4-hydroxybutyraldehyde can be effectively improved, the production of the 3-hydroxy-2-methylpropionaldehyde and other branched by-products can be inhibited, and the economy of the process can be effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of chemical synthesis, in particular to a synthesis method of 4-hydroxybutyraldehyde. BACKGROUND

[0002] 1,4-butanediol (1,4-BDO for short) is a kind of key organic and fine chemical raw material, which is widely used in medicine, chemical industry, textile, papermaking, automobile and daily chemical industry and many other fields. A variety of important chemical products can be produced by taking 1,4-BDO as raw material, such as tetrahydrofuran (THF), polytetramethylene glycol ether (PTMEG), gamma-butyrolactone (GBL), polybutylene succinate (PBS), polybutylene terephthalate (PBT), polyurethane resin (PU Resin), paint and plasticizer, etc., which can also be used as a solvent and a brightener in the electroplating industry. As can be seen, the market demand for 1,4-BDO is huge, and improving its yield is of great significance to meet the needs of various industries.

[0003] In the production method of 1,4-BDO, propylene oxide method (also known as allyl alcohol method) is a relatively common one. The method first prepares allyl alcohol through propylene oxide isomerization or allyl acetate hydrolysis; secondly, allyl alcohol is subjected to hydroformylation reaction to prepare 4-hydroxybutyraldehyde; finally, 4-hydroxybutyraldehyde is hydrogenated to synthesize 1,4-BDO. As can be seen, 4-hydroxybutyraldehyde is a crucial intermediate in the preparation process of 1,4-BDO, and high-efficiency synthesis of 4-hydroxybutyraldehyde through a suitable preparation method plays a key role in indirectly improving the yield of 1,4-butanediol.

[0004] Compared with other 1,4-BDO production methods such as alkyne aldehyde method, butadiene acetoxylation method and Davy method, the allyl alcohol method has the advantages of low investment, small energy consumption and flexible production capacity. However, in the actual production process, in addition to the main product 4-hydroxybutyraldehyde, a considerable amount of by-products will be produced in the hydroformylation process of allyl alcohol; these by-products mainly include 3-hydroxy-2-methylpropyl aldehyde branched by-products and C3 by-products such as n-propyl aldehyde and n-propyl alcohol. In the current mature industrial process, the by-products of hydroformylation are hydrogenated into corresponding alcohols, i.e. 2-methyl-1,3-propanediol and n-propyl alcohol, together with the main product. Although these by-products can be sold as products, due to the limited market capacity or cost factors, their existence will significantly affect the revenue of the process and have a negative impact on the economic feasibility of the process.

[0005] The patent CN114149312B provides a preparation method of 4-hydroxybutyraldehyde. The method uses allyl acetate as raw material, and through hydrolysis, extraction, rectification, hydroformylation and other steps, the product 4-hydroxybutyraldehyde is obtained, and the activity of the hydroformylation reaction and the normal / iso ratio of the product are improved by controlling the raw material and other means. However, the method has extremely strict requirements for the control of raw materials, and has strict restrictions on various trace impurities. In the actual industrial continuous production process, it is extremely difficult to achieve such fine continuous regulation and control, and it is difficult to meet the needs of large-scale production.

[0006] In summary, in the process of preparing 4-hydroxybutyraldehyde by hydroformylation of allyl alcohol, developing a 4-hydroxybutyraldehyde synthesis method with simple operation, high 4-hydroxybutyraldehyde yield and low by-product generation rate has important practical significance and application value for improving the economic efficiency of the process and indirectly increasing the yield of 1,4-BDO. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application discloses a synthesis method of 4-hydroxybutyraldehyde to improve the conversion rate of allyl alcohol and the selectivity of 4-hydroxybutyraldehyde, and inhibit the generation of branched by-products such as 3-hydroxy-2-methylpropionaldehyde.

[0008] To solve at least one of the above problems, the present application proposes a synthesis method of 4-hydroxybutyraldehyde, which dissolves allyl alcohol, rhodium catalyst, phosphorus ligand and reaction aid in a solvent to form a homogeneous solution, and performs a hydroformylation reaction on the homogeneous solution under the condition of passing synthetic gas to prepare 4-hydroxybutyraldehyde.

[0009] Among them, the structure general formula of the reaction aid is In the formula, R1 and R2 are the same or different, and are independently selected from any one of H, C1-C12 saturated alkyl, cycloalkyl or aromatic group.

[0010] In allyl alcohol hydroformylation reaction process, the unexpected discovery of the research and development team of the present invention, adds the reaction promoter with above-mentioned general formula, can not only significantly promote the reactive activity of catalyst, and can promote the generation of forward product 4-hydroxybutyraldehyde, can also suppress the generation amount of by products such as 3-hydroxy-2-methylpropional.The research and development team of the present invention further studies and analyzes and finds that the carbonyl-carbon-carbon double bond-carbonyl structure in the reaction promoter structure, can carry out bidentate coordination with the rhodium metal in the rhodium catalyst dissolved in solvent, form cyclic structure, make the active site of rhodium catalyst exposed, promote the activity of catalyst.Due to the influence of ester groups at both ends of reaction promoter, cause the absorption capacity of π-electrons in the main structure of reaction promoter to strengthen, and the absorption capacity of π-electrons is conducive to the branched structure intermediate generation of allyl alcohol in hydroformylation process when strengthening hydrogen elimination formation alkene, rather than CO migration insertion formation branched aldehyde, thus suppressing the generation of branched by-products such as 3-hydroxy-2-methylpropional, improve product positive iso-ratio.

[0011] In some embodiments, in the general formula of the reaction aid, R1 and R2 are the same and are selected from any one of H, methyl, ethyl, n-propyl, isopropyl, or phenyl. Optionally, the reaction aid is 1,4-butenediol dimethyl ester, 1,4-butenediol dibenzoate, 1,4-butenediol diethyl ester, 1,4-butenediol dipropyl ester, etc.

[0012] In some embodiments, the rhodium catalyst is one or more of rhodium 2-ethylhexanoate, rhodium dicarbonyl acetylacetonate, triphenylphosphine acetylacetonate carbonyl rhodium, tris(triphenylphosphine)carbonyl rhodium hydride, and (1,5-cyclooctadiene)chlororhodium dimer.

[0013] In some embodiments, the phosphorus ligand is one or more of P,P-bidentate phosphorus-containing ligand, preferably one or more of 1,2-bis(dimethylphosphino)ethane, bis-diphenylphosphinomethane, trans-1,2-bis(diphenylphosphino)ethylene, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane, 1,6-bis(diphenylphosphino)hexane, 1,2-bis(di-pentafluorophenylphosphino)-ethane, 1,2-bis(diphenylphosphino)benzene, 1,3-bis[(di-tert-butylphosphino)oxy]benzene, 2,2'-bis(diphenylphosphino)biphenyl, 1,1'-binaphthalene-2,2'-bisdiphenylphosphine, 1,8-bis(diphenylphosphino)naphthalene, bis(2-diphenylphosphinophenyl)ether, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, 4,6-bis(diphenylphosphino)phenazine, 4,5-bis(dicyclohexylphosphino)-dibenzopyran derivatives, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)propylamine, 1,1'-bis(diphenylphosphino)ferrocene, 1,1'-bis(diisopropylphosphino)ferrocene, 1,1'-bis(di-tert-butylphosphino)ferrocene.

[0014] In some embodiments, the solvent is one or more of C5-C15 aliphatic hydrocarbon, C6-C12 aromatic hydrocarbon, preferably one or more of toluene, xylene, cyclohexane, or methylcyclohexane.

[0015] In some embodiments, the molar ratio of the rhodium catalyst to the reaction aid is 1:(0.5-1).

[0016] In some embodiments, the concentration of the rhodium catalyst in the mixture of the allyl alcohol and the solvent is 50-100 ppm in terms of the mass of the contained rhodium element.

[0017] In some embodiments, the molar ratio of the phosphine ligand to the rhodium catalyst is (10-100):1.

[0018] In some embodiments, the mass ratio of the allyl alcohol to the solvent is 1:(2-10).

[0019] In some embodiments, the molar ratio of carbon monoxide to hydrogen in the synthesis gas is 1:(0.5-2).

[0020] In some embodiments, the pressure of the hydroformylation reaction is 0.5-6 MPaG;

[0021] and / or, the reaction temperature is 50-100°C;

[0022] and / or, the reaction time is 1-8h.

[0023] Compared with the prior art, the present application has the following beneficial effects: in the synthesis method of 4-hydroxybutyraldehyde, the activity of the catalyst can be effectively improved by introducing a reaction aid, the reaction rate is accelerated, the reaction efficiency is greatly improved, the selectivity of 4-hydroxybutyraldehyde is significantly improved, the loss of the target product is reduced, and the purity and quality of the product are improved. More importantly, the reaction aid can also effectively inhibit the generation of branched by-products such as 3-hydroxy-2-methylpropionaldehyde, reduce the influence of the by-products on the main product, and reduce the cost and difficulty of subsequent separation and purification. In addition, the reaction aid introduced in the present application has good solubility in the solvent and stable properties in the reaction system, and can be recycled, which has good industrial application prospect. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application are given. It should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the present application in any form, that is, not intended to limit the protection scope of the present application.

[0025] Unless otherwise defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are commercially available products; the experimental methods, unless otherwise specified, are conventional methods.

[0026] In the following examples, the source of the reaction aid is not limited and can be directly purchased from the market, or synthesized by any means known to those skilled in the art, such as using 1,4-butenediol and the corresponding acid as raw materials to synthesize by esterification.

[0027] In the following examples, the content of each component in the reaction product is analyzed by gas chromatography, and the allyl alcohol conversion rate, 4-hydroxybutyraldehyde selectivity, isomerization by-product selectivity and the normal-isomer ratio of the product are calculated according to the following formula:

[0028] Allyl alcohol conversion rate=(moles of allyl alcohol consumed in the reaction / moles of allyl alcohol feed) x 100%;

[0029] 4-hydroxybutyraldehyde selectivity=(moles of 4-hydroxybutyraldehyde generated in the reaction / moles of allyl alcohol consumed) x 100%;

[0030] Isomerization by-product (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) selectivity = (moles of isomerization by-product (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) produced by the reaction / moles of allyl alcohol consumed by the reaction) x 100%;

[0031] Product n / i ratio = 4-hydroxybutyraldehyde selectivity / isomerization by-product (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) selectivity.

[0032] Example 1

[0033] A homogeneous solution was formed by dissolving 250 g of allyl alcohol, 500 g of toluene, 0.188 g of rhodium dicarbonyl acetylacetanate (concentration of 100 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 28.014 g of dichlorobis(triphenylphosphine) palladium (molar ratio of ligand to rhodium catalyst was 100:1), and 0.105 g of 1,4-butanediol dimethyl ester (molar ratio of rhodium catalyst to reaction aid was 1:1). The homogeneous solution was placed in a pressure-resistant reaction kettle and was subjected to a reaction under the conditions of a molar ratio of 2:1 of hydrogen and CO, a pressure of 6 MPaG, and a temperature of 100°C for 1 h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0034] Gas chromatography detection showed that the conversion rate of allyl alcohol in the reaction solution was 99.8%, the selectivity of 4-hydroxybutyraldehyde was 98.1%, the selectivity of isomerization by-product (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 1.6%, and the product n / i ratio was 61.3:1.

[0035] Example 2

[0036] A homogeneous solution was formed by dissolving 60 g of allyl alcohol, 600 g of cyclohexane, 0.158 g of triphenylphosphine acetylacetone carbonyl rhodium (concentration of 50 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 2.431 g of 1,2-bis(dipentafluorophenylphosphine)-ethane (molar ratio of ligand to rhodium catalyst was 10:1), and 0.048 g of 1,4-butanediol dibenzoate (molar ratio of rhodium catalyst to reaction aid was 1:0.5). The homogeneous solution was placed in a pressure-resistant reaction kettle and was subjected to a reaction under the conditions of a molar ratio of 0.5:1 of hydrogen and CO, a pressure of 0.5 MPaG, and a temperature of 50°C for 8 h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0037] Gas chromatography detection showed that the conversion rate of allyl alcohol in the reaction solution was 99.3%, the selectivity of 4-hydroxybutyraldehyde was 96.9%, the selectivity of isomerization by-product (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 2.6%, and the product n / i ratio was 37.3:1.

[0038] Example 3

[0039] A homogeneous solution was formed by dissolving 120 g of allyl alcohol, 600 g of toluene, 0.386 g of tris(triphenylphosphine) rhodium carbonyl hydride (60 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 8.774 g of 2,2'-bis(diphenylphosphino) biphenyl (molar ratio of ligand to rhodium catalyst is 40:1), and 0.051 g of 1,4-butanediol diethyl ester (molar ratio of rhodium catalyst to reaction aid is 1:0.7). The homogeneous solution was introduced into a pressure-resistant reactor, and hydrogen and CO were introduced at a molar ratio of 1:1. The reaction was carried out at a pressure of 2.5 MPaG and a temperature of 80°C for 3 hours to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0040] According to gas chromatography detection, the conversion rate of allyl alcohol in the reaction solution was 99.5%, the selectivity of 4-hydroxybutyraldehyde was 97.3%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 2.3%, and the normal-to-isomer ratio of the product was 42.3:1.

[0041] Example 4

[0042] A homogeneous solution was formed by dissolving 80 g of allyl alcohol, 600 g of toluene, 0.130 g of (1,5-cyclooctadiene) rhodium chloride dimer (80 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 22.306 g of 4,5-bis(dicyclohexylphosphino)-dibenzopyran derivative (molar ratio of ligand to rhodium catalyst is 70:1), and 0.085 g of 1,4-butanediol dipropyl ester (molar ratio of rhodium catalyst to reaction aid is 1:0.8). The homogeneous solution was introduced into a pressure-resistant reactor, and hydrogen and CO were introduced at a molar ratio of 1:1. The reaction was carried out at a pressure of 1.5 MPaG and a temperature of 70°C for 5 hours to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0043] According to gas chromatography detection, the conversion rate of allyl alcohol in the reaction solution was 99.4%, the selectivity of 4-hydroxybutyraldehyde was 97.1%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 2.4%, and the normal-to-isomer ratio of the product was 40.5:1.

[0044] Example 5

[0045] The reaction solution of 4-hydroxybutyraldehyde obtained in Example 4 was transferred to a separation tank, deionized water was added for separation, the lower layer was the aqueous phase in which unreacted allyl alcohol and the product existed, and the upper layer was the toluene phase in which rhodium catalyst, ligand and reaction aid existed. The toluene phase was collected and transferred to a pressure-resistant reactor again, then 80 g of allyl alcohol was added, and the hydroformylation reaction was carried out according to the conditions of Example 4. The reaction was recycled for a total of 5 times.

[0046] The results of the 5 times of recycling experiments are shown in Table 1.

[0047] Table 1

[0048]

[0049] Comparative Example 1

[0050] This comparative example is based on Example 1, except that the reaction aid 1,4-butanediol dimethyl carbonate is not added, and the other conditions are the same.

[0051] A homogeneous solution was formed by dissolving 250 g of allyl alcohol, 500 g of toluene, 0.188 g of rhodium dicarbonyl acetylacetone (concentration of 100 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), and 28.014 g of bisdiphenylphosphine methane (molar ratio of ligand to rhodium catalyst is 100:1). The homogeneous solution was placed in a pressure-resistant reaction kettle and was introduced with hydrogen and CO at a molar ratio of 2:1, and was reacted at a pressure of 6 MPaG and a temperature of 100°C for 1 h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0052] Gas chromatography detection showed that the conversion rate of allyl alcohol in the reaction solution was 88.1%, the selectivity of 4-hydroxybutyraldehyde was 86.9%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 12.2%, and the n / i ratio of the product was 7.1:1.

[0053] Comparative Example 2

[0054] This comparative example is based on Example 2, except that the reaction aid 1,4-butanediol dibenzoate is changed to equimolar 1,4-butanediol dibenzoate, and the other conditions are unchanged.

[0055] A homogeneous solution was formed by dissolving 60 g of allyl alcohol, 600 g of cyclohexane, 0.158 g of triphenylphosphine acetylacetone carbonyl rhodium (concentration of 50 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 2.431 g of 1,2-bis(dipentafluorophenylphosphino)-ethane (molar ratio of ligand to rhodium catalyst is 10:1), and 0.048 g of 1,4-butanediol dibenzoate (molar ratio of rhodium catalyst to reaction aid is 1:0.5). The homogeneous solution was placed in a pressure-resistant reaction kettle and was introduced with hydrogen and CO at a molar ratio of 0.5:1, and was reacted at a pressure of 0.5 MPaG and a temperature of 50°C for 8 h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0056] Gas chromatography detection showed that the conversion rate of allyl alcohol in the reaction solution was 88.5%, the selectivity of 4-hydroxybutyraldehyde was 87.5%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) was 11.8%, and the n / i ratio of the product was 7.4:1.

[0057] Comparative Example 3

[0058] The comparative example is based on example 3, the reaction aid 1,4-butenediol diethyl ester is changed to equimolar amount of allyl acetate, and the rest of the conditions remain unchanged.

[0059] After 120 g of allyl alcohol, 600 g of xylene, 0.386 g of tris (triphenylphosphine) rhodium carbonyl hydride (60 ppm of rhodium element in the mixed solution of allyl alcohol and toluene, the concentration is 60 ppm of rhodium element in the mixed solution of allyl alcohol and toluene, 8.774 g of 2,2'-bis (diphenylphosphine) biphenyl (the molar ratio of ligand to rhodium catalyst is 40:1) and 0.029 g of allyl acetate (the molar ratio of rhodium catalyst to reaction aid is 1:0.7) are mixed and dissolved to form a homogeneous solution. The homogeneous solution is placed in a pressure-resistant reaction kettle and hydrogen and CO with a molar ratio of 1:1 are introduced, and the reaction is carried out at a pressure of 2.5 MPaG and a temperature of 80°C for 3h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0060] After gas chromatography detection, the conversion rate of allyl alcohol in the reaction solution is 90.7%, the selectivity of 4-hydroxybutyraldehyde is 88.9%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) is 10.5%, and the n / i ratio of the product is 8.5:1.

[0061] Comparative example 4

[0062] The comparative example is based on example 4, the molar ratio of rhodium catalyst to reaction aid is changed to 1:1.2, and the rest of the conditions remain unchanged.

[0063] After 80 g of allyl alcohol, 600 g of toluene, 0.130 g of (1,5-cyclooctadiene) chloro rhodium dimer (80 ppm of rhodium element in the mixed solution of allyl alcohol and toluene, the concentration is 80 ppm of rhodium element in the mixed solution of allyl alcohol and toluene, 22.306 g of 4,5-bis (dicyclohexylphosphine) -dibenzopyran derivative (the molar ratio of ligand to rhodium catalyst is 70:1) and 0.127 g of 1,4-butenediol dipropyl ester (the molar ratio of rhodium catalyst to reaction aid is 1:1.2) are mixed and dissolved to form a homogeneous solution. The homogeneous solution is placed in a pressure-resistant reaction kettle and hydrogen and CO with a molar ratio of 1:1 are introduced, and the reaction is carried out at a pressure of 1.5 MPaG and a temperature of 70°C for 5h to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0064] After gas chromatography detection, the conversion rate of allyl alcohol in the reaction solution is 94.1%, the selectivity of 4-hydroxybutyraldehyde is 93.3%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propanol) is 6.3%, and the n / i ratio of the product is 14.8:1.

[0065] Comparative example 5

[0066] The comparative example is based on example 4, the molar ratio of rhodium catalyst to reaction aid is changed to 1:0.4, and the rest of the conditions remain unchanged.

[0067] A homogeneous solution was formed by dissolving 80 g of allyl alcohol, 600 g of toluene, 0.130 g of (1,5-cyclooctadiene)chloro rhodium dimer (80 ppm of rhodium element in the mixed solution of allyl alcohol and toluene), 22.306 g of 4,5-bis(dicyclohexylphosphino)-dibenzopyran derivative (molar ratio of ligand to rhodium catalyst was 70:1), and 0.042 g of 1,4-butanediol dipropyl ester (molar ratio of rhodium catalyst to reaction aid was 1:0.4). The homogeneous solution was placed in a pressure-resistant reaction kettle and was subjected to reaction under the conditions of 1.5 MPaG of pressure and 70°C of temperature for 5 h by introducing hydrogen and CO at a molar ratio of 1:1 to obtain a reaction solution of 4-hydroxybutyraldehyde.

[0068] According to gas chromatography detection, the conversion rate of allyl alcohol in the reaction solution was 94.4%, the selectivity of 4-hydroxybutyraldehyde was 94.0%, the selectivity of isomerization by-products (3-hydroxy-2-methylpropionaldehyde, n-propionaldehyde, n-propyl alcohol) was 5.5%, and the normal-to-isomer ratio of the product was 17.1:1.

[0069] The experimental results of examples 1-4 and comparative examples 1-5 were summarized in Table 2.

[0070] Table 2

[0071]

[0072] According to the above, the conversion rate of propylene alcohol in the reaction solution of 4-hydroxybutyraldehyde obtained by the synthesis method of examples 1-4 was more than 99%, the selectivity of 4-hydroxybutyraldehyde was in the range of 96-98%, the selectivity of isomerization by-products was 1-3%, and the normal-to-isomer ratio of the product was in the range of (40-62):1.

[0073] As can be seen from example 5, the reaction aid 1,4-butanediol diester is stable in the reaction system and can be recycled for multiple times, which has good industrial application prospect.

[0074] As can be seen from comparative example 1 and comparative example 1, the presence of the reaction aid can significantly improve the catalytic activity of the catalyst and the selectivity of 4-hydroxybutyraldehyde, and inhibit the generation of isomerization by-products.

[0075] As can be seen from comparative example 2 and comparative example 2, the use of 1,4-butanediol diester with similar structure instead of 1,4-butanediol diester cannot achieve similar results, which is presumably because the 1,4-butanediol diester structure does not have an unsaturated carbon-carbon double bond structure and does not have a carbonyl-carbon-carbon double bond-carbonyl structure, so it cannot coordinate with the rhodium catalyst of the solvent to improve the activity of the rhodium catalyst and the selectivity of 4-hydroxybutyraldehyde.

[0076] Comparing Example 3 with Comparative Example 3, it can be seen that using an allyl acetate structure having a carbon-carbon double bond-carbonyl structure instead of 1,4-butenediol diester does not achieve similar results. It is speculated that this may be because the carbon-carbon double bond-carbonyl structure of allyl acetate cannot form a bidentate coordination with the rhodium catalyst like the carbonyl-carbon-carbon double bond-carbonyl structure in 1,4-butenediol diester, and the effect of using 1,4-butenediol diester cannot be achieved.

[0077] Comparing Example 4 with Comparative Example 4 and Comparative Example 5, it can be seen that the amount of 1,4-butenediol diester needs to be controlled at a reasonable level. Neither a larger nor a lower amount can achieve a desired result. It is speculated that this may be because CO in the gas phase can also coordinate with rhodium. When the amount of reaction aid is low, it is mainly CO that participates in the coordination of rhodium, which is not conducive to the exposure of the active sites of the rhodium catalyst. When the amount of reaction aid is too much, since the content of the rhodium catalyst is limited, not only can the catalyst not be exposed to more active sites, but due to the spatial structure of its molecule, the active sites of the catalyst will be blocked, resulting in a decrease in catalyst activity.

[0078] It should be noted that the above content is a further detailed description of the present invention in conjunction with specific implementation methods, and the specific implementation of the present invention cannot be considered to be limited to these descriptions; the specific parameters of this embodiment do not necessarily limit the technical solution, but only illustrate one specific working condition. For those skilled in the art of the present invention, simple improvements and modifications can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing 4-hydroxybutyraldehyde, characterized in that: Allyl alcohol, a rhodium catalyst, a phosphorus ligand, and a reaction aid are dissolved in a solvent to form a homogeneous solution, and the homogeneous solution is subjected to a hydroformylation reaction under a condition of introducing synthesis gas to prepare 4-hydroxybutyraldehyde; Wherein, the general structural formula of the reaction aid is In the formula, R1 and R2 are the same or different and are independently selected from any one of H, C1-C12 saturated alkyl, cycloalkyl or aromatic groups.

2. The synthetic method of 4-hydroxybutyraldehyde according to claim 1, wherein In the general structural formula of the reaction auxiliary, R1 and R2 are the same and are selected from any one of H, methyl, ethyl, n-propyl, isopropyl or phenyl.

3. The synthetic method of 4-hydroxybutyraldehyde according to claim 1, wherein The rhodium catalyst is one or more of 2-ethylhexanoic acid rhodium, dicarbonyl acetylacetonate rhodium, triphenylphosphine acetylacetonate carbonyl rhodium, tri(triphenylphosphine)carbonyl rhodium hydride, and (1,5-cyclooctadiene)chlororhodium dimer.

4. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The phosphorus ligand is a P,P-bidentate phosphorus-containing ligand, preferably 1,2-bis(dimethylphosphino)ethane, bisdiphenylphosphinomethane, trans-1,2-bis(diphenylphosphino)ethylene, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane, 1,6-bis(diphenylphosphino)hexane, 1,2-bis(dipentafluorophenylphosphino)-ethane, 1,2-bis(diphenylphosphino)benzene, 1,3-bis[(di-tert-butylphosphino)oxy]benzene, 2,2'-bis(diphenylphosphino) One or more of biphenyl, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,8-bis(diphenylphosphino)naphthalene, bis(2-diphenylphosphinophenyl) ether, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, 4,6-bis(diphenylphosphino)phenazine, 4,5-bis(dicyclohexylphosphino)-dibenzopyran derivatives, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)propylamine, 1,1'-bis(diphenylphosphino)ferrocene, 1,1'-bis(diisopropylphosphino)ferrocene, and 1,1'-bis(di-tert-butylphosphino)ferrocene.

5. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The solvent is selected from one or more of C5-C15 aliphatic hydrocarbons and C6-C12 aromatic hydrocarbons, preferably one or more of toluene, xylene, cyclohexane or methylcyclohexane.

6. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The molar ratio of the rhodium catalyst to the reaction aid is 1:(0.5-1).

7. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein Calculated by the mass of the rhodium element contained, the concentration of the rhodium catalyst in the mixture of the allyl alcohol and the solvent is 50 to 100 ppm.

8. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The molar ratio of the phosphine ligand to the rhodium catalyst is (10-100):

1. And / or, the mass ratio of the allyl alcohol to the solvent is 1:(2-10).

9. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The molar ratio of carbon monoxide to hydrogen in the synthesis gas is 1:(0.5-2).

10. The method for synthesizing 4-hydroxybutyraldehyde according to claim 1, wherein The pressure of the hydroformylation reaction is 0.5-6 MPaG; and / or, the reaction temperature is 50-100° C.; And / or, the reaction time is 1 to 8 hours.

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