A catalyst system for the hydroformylation synthesis of butyraldehyde and its application

Abstract

This application relates to the field of catalytic technology, in particular to a catalyst system for hydroformylation synthesis of butyraldehyde and its application. A catalyst system for hydroformylation synthesis of butyraldehyde includes a first ligand, a second ligand and a metal active component; the first ligand is a bidentate rigid phosphine ligand, and the second ligand is a monodentate auxiliary phosphine ligand; the preparation method of the first ligand is as follows: 1) React o-bromotoluene, tert-butyllithium and diphenylphosphine chloride to obtain o-tert-butyldiphenylphosphine; 2) Carry out an electrophilic substitution reaction between o-tert-butyldiphenylphosphine and silver trifluoromethanesulfonate to introduce a -CF3 group at the para position of the benzene ring; then purify to obtain o-tert-butyl-p-trifluoromethyl diphenylphosphine; 3) React tert-butyl-p-trifluoromethyl diphenylphosphine with 1,2-dibromoethane to generate a bidentate ligand, and then purify by recrystallization to obtain the first ligand. When it is applied to the hydroformylation synthesis of butyraldehyde reaction, the n / i ratio of the obtained product can reach 25.4 - 30:1.

Description

Technical Field

[0001] The present application relates to the field of catalytic technology, and in particular to a catalyst system for synthesizing butyraldehyde through hydroformylation and its application. Background Art

[0002] Butyraldehyde is an important chemical raw material, mainly used as an intermediate for resins, plasticizers, vulcanization accelerators, pesticides, etc. In the reaction to prepare butyraldehyde, the reactants are propylene and mixed gases (carbon monoxide and hydrogen), and butyraldehyde is produced.

[0003] In the above reaction, the commonly used catalyst is a catalyst formed by triphenylphosphine and rhodium catalytic active components. Using the low-pressure rhodium carbonyl synthesis process, the reaction conditions are 75-95°C, 0.8-2.0MPa, the allyl alcohol conversion rate is 97-99%, the selectivity is 96-98%, and the product iso-ratio is 7:10. However, the product iso-ratio is designed to be 7:10, and it is difficult to maintain a low level in actual operation.

[0004] Butyraldehyde is a key intermediate in the production of plasticizers and solvents (such as 2-ethylhexanol). The industrial demand for it is much higher than that for isobutyraldehyde. Therefore, how to increase the content of n-butyraldehyde is a technical problem that needs to be solved in the process of producing butyraldehyde. Summary of the invention

[0005] In order to increase the content of normal butyraldehyde in the process of hydroformylation to butyraldehyde, the present application provides a catalyst system for hydroformylation to butyraldehyde and its application.

[0006] In a first aspect, the present application provides a catalyst system for synthesizing butyraldehyde by hydroformylation, which adopts the following technical scheme.

[0007] A catalyst system for synthesizing butyraldehyde by hydroformylation, comprising a first ligand, a second ligand and a metal active component;

[0008] The first ligand is a bidentate rigid phosphine ligand, and the second ligand is a monodentate auxiliary phosphine ligand;

[0009] The preparation method of the first ligand is:

[0010] 1) Preparation of o-tert-butyldiphenylphosphine

[0011] React o-bromotoluene with tert-butyllithium to generate o-tert-butylphenyllithium intermediate;

[0012] Then add diphenylphosphine chloride and heat the reaction to obtain o-tert-butyldiphenylphosphine;

[0013] ‌2) CF3 substitution of benzene ring modification‌

[0014] An electrophilic substitution reaction is carried out between o-tert-butyl diphenylphosphine and silver trifluoromethanesulfonate to introduce a -CF3 group at the para position of the benzene ring;

[0015] Then it is purified to obtain o-tert-butyl-p-trifluoromethyl diphenylphosphine;

[0016] 3) Bidentate ligand bridging

[0017] o-tert-Butyl-p-trifluoromethyl diphenylphosphine reacts with 1,2-dibromoethane to form a bidentate ligand, and then it is purified by recrystallization to obtain the first ligand.

[0018] By adopting the above technical solution, a phosphine ligand is designed. The rigid skeleton of the first ligand, through the steric effects of the tert-butyl group and the CF3 group, forces propylene to approach the rhodium center in a "trans" configuration, forming a linear transition state and sterically excluding the formation of branched-chain isomers; the strong electron-withdrawing property of the second ligand reduces the electron density of rhodium, weakens the stability of the branched-chain acyl rhodium intermediate (isobutyraldehyde precursor), and promotes its rapid conversion to the linear product. In the catalytic reaction, the first ligand and the second ligand form a mixed coordination layer at the rhodium center, where the first ligand serves as an axial rigid anchor point and the second ligand serves as an equatorial flexible adjustment site, dynamically optimizing the energy path of the intermediate through ligand exchange to achieve high selectivity and achieve dynamic coordination equilibrium. That is, the first bidentate rigid phosphine ligand, through the synergistic effect of the ortho-tert-butyl group and the para-CF3 group, restricts the spatial configuration of the reaction intermediate, enabling propylene to preferentially insert into the rhodium center in a linear form and significantly inhibiting the formation of isobutyraldehyde. The second ligand reduces the electron density of rhodium through a strong electron-withdrawing effect, stabilizes the linear acyl rhodium intermediate (n-butyraldehyde precursor), and further enhances the selectivity.

[0019] In the catalytic system of this application, the rhodium-based catalyst, through the synergistic design of rigid / flexible ligands and the precise regulation of electronic / steric effects, achieves high regioselectivity and long-term stability in the hydroformylation reaction of propylene, providing an efficient solution for industrial-grade n-butyraldehyde production.

[0020] In the catalytic reaction, high pressure and high temperature can be used for assistance. High pressure promotes the rate of CO insertion into the linear path, while high temperature accelerates the dissociation of the branched-chain intermediate, and the dual effects inhibit the accumulation of isobutyraldehyde.

[0021] Furthermore, in 1), the weight ratio of o-bromotoluene, tert-butyllithium, and diphenylphosphine chloride is 1: (4.5 - 5): (1 - 1.5).

[0022] Furthermore, in 2), the weight ratio of o-tert-butyl diphenylphosphine and silver trifluoromethanesulfonate is 1: (1 - 5).

[0023] Further, the weight ratio of tert-butyl-bis(4-(trifluoromethyl)phenyl)phosphine to 1,2-dibromoethane in the step 3) is (4-6):1.

[0024] Further, the monodentate auxiliary phosphine ligand is tris(pentafluorophenyl)phosphine.

[0025] Further, the weight ratio of the first ligand to the second ligand is (5-8):1.

[0026] Further, the metal active component is rhodium.

[0027] Further, its preparation method includes:

[0028] S1. Activation of rhodium precursor;

[0029] S2. Ligand compounding and complexation

[0030] Add the activated rhodium precursor, the first ligand, and the second ligand into toluene solvent, and react at 80 °C for 5-7 hours under the action of a protective gas. Then remove the solvent under reduced pressure and wash to obtain a catalyst system for hydroformylation synthesis of butyraldehyde.

[0031] In the second aspect, the present application provides an application of a catalyst system for hydroformylation synthesis of butyraldehyde, adopting the following technical solution.

[0032] An application of a catalyst system for hydroformylation synthesis of butyraldehyde, which is applied to the hydroformylation synthesis of butyraldehyde.

[0033] In summary, the present application has the following beneficial effects:

[0034] In this application, a catalyst is prepared by combining a bidentate rigid phosphine ligand (the first ligand) with a monodentate auxiliary phosphine ligand (the second ligand). The rigid skeleton of the first ligand, through the steric effects of the tert-butyl group and the CF3 group, forces propylene to approach the rhodium center in a "trans" configuration, forming a linear transition state and sterically excluding the formation of branched-chain isomers. The strong electron-withdrawing property of the second ligand reduces the electron density of rhodium, weakens the stability of the branched-chain acylrhodium intermediate (the isobutyraldehyde precursor), and promotes its rapid conversion to the linear product. In the catalytic reaction, the first ligand and the second ligand form a mixed coordination layer at the rhodium center. The first ligand serves as an axial rigid anchor point, and the second ligand serves as an equatorial flexible adjustment site, dynamically optimizing the energy path of the intermediate through ligand exchange to achieve high selectivity and a dynamic coordination equilibrium. That is, the bidentate rigid phosphine ligand of the first ligand, through the synergistic effect of the ortho-tert-butyl group and the para-CF3 group, restricts the spatial configuration of the reaction intermediate, enabling propylene to preferentially insert into the rhodium center in a linear form and significantly inhibiting the formation of isobutyraldehyde. The second ligand reduces the electron density of rhodium through a strong electron-withdrawing effect, stabilizes the linear acylrhodium intermediate (the n-butyraldehyde precursor), and further enhances the selectivity. When applied to the hydroformylation reaction for synthesizing butyraldehyde, the n / i ratio of the obtained product can reach 25.4 - 30:1. Detailed implementation mode

[0035] The following further elaborates on this application with reference to examples.

[0036] Preparation examples of raw materials and intermediates

[0037] Raw materials

[0038] The raw materials in the examples of this application can all be obtained commercially:

[0039] o-Bromotoluene, analytical grade;

[0040] tert-Butyllithium, analytical grade;

[0041] Diphenylphosphine chloride, analytical grade;

[0042] Silver trifluoromethanesulfonate, analytical grade;

[0043] 1,2-Dibromoethane, analytical grade.

[0044] Preparation examples

[0045] Preparation example 1

[0046] A first ligand, the preparation method thereof is as follows:

[0047] 1) Preparation of o-tert-butyldiphenylphosphine

[0048] Dissolve 4.5 kg of tert-butyllithium in a hexane solvent to obtain a tert-butyllithium solution with a concentration of 1.0 M. Add 1 kg of o-bromotoluene to anhydrous diethyl ether to obtain a mixture. Dropwise add the tert-butyllithium solution to the mixture at -78 °C, and react to form an o-tert-butylphenyllithium intermediate.

[0049] Then, dropwise add 1.5 kg of diphenylphosphine chloride to the above reaction solution, raise the temperature to 25 °C and react to obtain o-tert-butyldiphenylphosphine.

[0050] 2) CF3 substitution for benzene ring modification

[0051] Reflux 1 kg of o-tert-butyldiphenylphosphine and 3 kg of silver trifluoromethanesulfonate in toluene for 24 hours to carry out an electrophilic substitution reaction to introduce a -CF3 group at the para position of the benzene ring.

[0052] The product is purified by column chromatography (petroleum ether / ethyl acetate = 10:1) to obtain o-tert-butyl-p-trifluoromethyldiphenylphosphine.

[0053] 3) Bidentate ligand bridging

[0054] React 5 kg of tert-butyl-p-trifluoromethyldiphenylphosphine with 1 kg of 1,2-dibromoethane in tetrahydrofuran using NaH as the base at 60 °C for 48 hours to form a bidentate ligand, and then purify it by recrystallization to obtain the first ligand.

[0055] Preparation Example 2

[0056] The difference from Preparation Example 1 is that in step 1) of Preparation Example 2, the weight ratio of o-bromotoluene, tert-butyllithium, and diphenylphosphine chloride is 1:5:1.

[0057] Preparation Example 3

[0058] The difference from Preparation Example 1 is that in step 1) of Preparation Example 3, the weight ratio of o-bromotoluene, tert-butyllithium, and diphenylphosphine chloride is 1:4:1.

[0059] Preparation Example 4

[0060] The difference from Preparation Example 1 is that in step 2) of Preparation Example 4, the weight ratio of o-tert-butyldiphenylphosphine and silver trifluoromethanesulfonate is 1:1.

[0061] Preparation Example 5

[0062] The difference from Preparation Example 1 is that in step 2) of Preparation Example 5, the weight ratio of o-tert-butyldiphenylphosphine and silver trifluoromethanesulfonate is 1:5.

[0063] Preparation Example 6

[0064] Different from Preparation Example 1, in Step 2) of Preparation Example 6, the weight ratio of o-tert-butyldiphenylphosphine to silver trifluoromethanesulfonate is 1:6.

[0065] Preparation Example 7

[0066] Different from Preparation Example 1, in Step 3) of Preparation Example 7, the weight ratio of tert-butyl-bis(4-(trifluoromethyl)phenyl)phosphine to 1,2-dibromoethane is 4:1.

[0067] Preparation Example 8

[0068] Different from Preparation Example 1, in Step 3) of Preparation Example 8, the weight ratio of tert-butyl-bis(4-(trifluoromethyl)phenyl)phosphine to 1,2-dibromoethane is 6:1.

[0069] Preparation Example 9

[0070] Different from Preparation Example 1, in Step 3) of Preparation Example 9, the weight ratio of tert-butyl-bis(4-(trifluoromethyl)phenyl)phosphine to 1,2-dibromoethane is 3:1.

[0071] Examples

[0072] Example 1

[0073] A catalyst system for hydroformylation synthesis of butyraldehyde, comprising a first ligand, a second ligand and a metal active component, and its preparation method is as follows:

[0074] S1. Activation of rhodium precursor

[0075] Using dirhodium(II) tetraacetate as the precursor, 0.1 kg of dirhodium(II) tetraacetate is added to 7 L of toluene, and stirred at room temperature for 30 minutes under the protection of CO gas to obtain the activated rhodium precursor;

[0076] S2. Ligand complexing and coordination

[0077] Add 3.5 kg of the activated rhodium precursor, 7 kg of the first ligand from Preparation Example 1, and 1 kg of the second ligand tris(pentafluorophenyl)phosphine to 70 L of toluene solvent, and react at 80 °C for 6 hours under the action of the protective gas CO, then remove the solvent under reduced pressure and wash to obtain the catalyst system for hydroformylation synthesis of butyraldehyde.

[0078] Example 2

[0079] Different from Example 1, in Example 2, the dosage of the first ligand is 5 kg.

[0080] Example 3

[0081] Different from Example 1, in Example 3, the dosage of the first ligand is 8 kg.

[0082] Example 4

[0083] Different from Example 1, the dosage of the first ligand in Example 4 is 9 kg.

[0084] Examples 5 - 12

[0085] Different from Example 1, the first ligands in Examples 5 - 12 are respectively from Preparation Examples 2 - 9. Comparative Example

[0086] Comparative Example 1

[0087] A catalytic system, and its preparation method is as follows:

[0088] Under nitrogen protection, acetylacetone dicarbonyl rhodium and triphenylphosphine are added, and the molar ratio of acetylacetone dicarbonyl rhodium:triphenylphosphine = 1:5;

[0089] Deoxygenated toluene is injected, stirred and heated to 65 °C, and reacted for 5 hours to form an orange - red solution.

[0090] Application Example

[0091] Application Example 1

[0092] A method for synthesizing butyraldehyde, comprising the following steps:

[0093] I. Reaction system design

[0094] Raw material ratio (based on 1 kg of propylene):

[0095] Propylene (purity ≥ 99.5%): 1 kg;

[0096] Synthesis gas (H2:CO = 1:1, volume ratio): The total dosage is 1.5 times the molar amount of propylene;

[0097] Catalyst: The catalytic system obtained in Example 1, and the dosage is 0.05 g catalyst / kg propylene;

[0098] Solvent: Toluene / n - heptane (volume ratio 3:1), and the solvent dosage is 5 times the mass of propylene (5 L / kg propylene).

[0099] II. Operating steps and process parameters

[0100] Reactor preparation:

[0101] A high - pressure stainless - steel batch reactor or a continuous - flow tubular reactor is used;

[0102] The reactor is pre - purged with nitrogen 3 times to ensure an oxygen - free environment;

[0103] Add solvent, propylene and catalyst, seal the reactor, introduce syngas to an initial pressure of 5 bar, and maintain the subsequent reaction pressure at 10 bar.

[0104] Reaction condition control:

[0105] Temperature: 80 °C;

[0106] Pressure: constant pressure of 10 bar;

[0107] Stirring speed: 800 rpm;

[0108] Reaction time: 4 hours;

[0109] Gas recycling: The unreacted syngas is condensed and separated and then returned to the reactor for recycling.

[0110] III. Product separation and catalyst recovery

[0111] Product separation:

[0112] After the reaction is completed, cool down to 25 °C and slowly release the pressure to atmospheric pressure;

[0113] Separate the solvent (toluene / n-heptane recovery rate ≥ 98%) by distillation, and then rectify to collect n-butyraldehyde (boiling point 75 °C) and isobutyraldehyde (boiling point 64 °C).

[0114] Catalyst recovery:

[0115] Primary separation: Solvent distillation recovery. After the reaction is completed, cool the mixture to 25 °C and separate the solvent (toluene / n-heptane) by vacuum distillation (45 °C, 0.1 bar), with a recovery rate ≥ 98%;

[0116] Residue: The remaining liquid contains Rh-L1 / L2 complex, trace amounts of unreacted propylene and the product butyraldehyde;

[0117] Secondary separation: Catalyst adsorption and enrichment. Use functionalized mesoporous silica (NH2-SBA-15) as the adsorbent, mix the distillation residue with the adsorbent (the dosage is 20 times the mass of rhodium), stir at 50 °C for 2 hours, filter to separate the adsorbent, and wash with n-heptane 3 times to remove the residual product;

[0118] Catalyst desorption and regeneration: Desorbing solution: Toluene solution containing the first ligand and the second ligand (to supplement the ligand loss), the ratio of the first ligand to the second ligand is the same as that in the reaction system. Immerse the adsorbent in the desorbing solution at 60 °C for 1 hour, and centrifuge to obtain the catalyst regeneration solution, which is directly used for the next batch of reactions.

[0119] Control of rhodium loss:

[0120] Monitoring: After desorption, the rhodium content in the waste liquid is detected by ICP-OES. If it is > 0.1 ppm, the sulfide precipitation method (treatment with Na2S) is added to ensure up-to-standard discharge.

[0121] Application Example 2 - 12

[0122] Different from Application Example 1, the catalysts in Application Examples 2 - 12 are from Examples 2 - 12 respectively.

[0123] Comparative Application Example

[0124] Comparative Application Example 1

[0125] Different from Application Example 1, the catalyst in Comparative Application Example 1 is from Example 1.

[0126] Performance Detection

[0127] The contents of n-butyraldehyde and isobutyraldehyde obtained in the application examples and comparative application examples are detected, and the n / i ratio (weight ratio of n-butyraldehyde to isobutyraldehyde) is calculated. The results are shown in Table 1;

[0128] After continuous use for 10 times, the rhodium loss of the catalyst is detected. The results are shown in Table 1.

[0129] Table 1 Performance Detection Results

[0130]

[0131] Combined with Application Examples 1-12 and Comparative Application Example 1, and in combination with Table 1, it can be seen that the content of n-butanal in the products obtained by the methods for preparing butanal in Application Examples 1-12 is higher. This indicates that the catalyst system of the present application has higher selectivity for n-butanal and can increase the content of n-butanal. This may be because in the catalyst of the present application, the rigid skeleton of the first ligand, through the steric effects of the tert-butyl and CF3 groups, forces propylene to approach the rhodium center in a "trans" configuration, forming a linear transition state and sterically excluding the formation of branched-chain isomers; the strong electron-withdrawing property of the second ligand reduces the electron density of rhodium and weakens the stability of the branched-chain acylrhodium intermediate (precursor of isobutanal), prompting its rapid conversion to a linear product. In the catalytic reaction, the first ligand and the second ligand form a mixed coordination layer at the rhodium center, where the first ligand serves as an axial rigid anchor point and the second ligand serves as an equatorial flexible adjustment site, dynamically optimizing the energy path of the intermediate through ligand exchange to achieve high selectivity and dynamic coordination equilibrium. That is, the bidentate rigid phosphine ligand of the first ligand, through the synergistic effect of the ortho-tert-butyl group and the para-CF3 group, restricts the spatial configuration of the reaction intermediate, enabling propylene to preferentially insert into the rhodium center in a linear form and significantly inhibiting the formation of isobutanal. The second ligand reduces the electron density of rhodium through a strong electron-withdrawing effect, stabilizing the linear acylrhodium intermediate (precursor of n-butanal) and further enhancing the selectivity.

[0132] Combined with Application Examples 1-4 and in combination with Table 1, it can be seen that the content of n-butanal in the products obtained by the method for preparing butanal in Application Example 1 is higher. This indicates that the ratio of the first ligand to the second ligand in the catalyst system affects the selectivity of the catalyst for n-butanal, and the ratio in Application Example 1 is more optimal.

[0133] Combined with Application Example 1 and Application Examples 5-12 and in combination with Table 1, it can be seen that the ratio of each functional group in the process of preparing the catalyst affects the selectivity of the catalyst for n-butanal, and the ratio in Application Example 1 is more optimal.

[0134] This specific embodiment is only an explanation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A catalyst system for synthesizing butyraldehyde by hydroformylation, characterized in that, It includes a first ligand, a second ligand and a metal active component; The first ligand is a bidentate rigid phosphine ligand, and the second ligand is a monodentate auxiliary phosphine ligand; The preparation method of the first ligand is as follows: 1) Preparation of o-tert-butyl diphenylphosphine React o-bromotoluene with tert-butyllithium to generate an intermediate of o-tert-butylphenyllithium; Then add diphenylphosphine chloride and heat up for reaction to obtain o-tert-butyl diphenylphosphine; 2) Modification of CF3 substitution on the benzene ring Carry out an electrophilic substitution reaction of o-tert-butyl diphenylphosphine with silver trifluoromethanesulfonate to introduce a -CF3 group at the para position of the benzene ring; Then purify to obtain o-tert-butyl-p-trifluoromethyl diphenylphosphine; 3) Bridging of bidentate ligands React tert-butyl-p-trifluoromethyl diphenylphosphine with 1,2-dibromoethane to generate a bidentate ligand, and then purify by recrystallization to obtain the first ligand.

2. The catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, In the above 1), the weight ratio of o-bromotoluene, tert-butyllithium, and diphenylphosphine chloride is 1:(4.5 - 5):(1 - 1.5).

3. A catalyst system for synthesizing butyraldehyde by hydroformylation according to claim 1, characterized in that, In the above 2), the weight ratio of o-tert-butyl diphenylphosphine to silver trifluoromethanesulfonate is 1:(1 - 5).

4. A catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, In the above 3), the weight ratio of tert-butyl-p-trifluoromethyl diphenylphosphine to 1,2-dibromoethane is (4 - 6):

1.

5. A catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, The monodentate auxiliary phosphine ligand is tris(pentafluorophenyl)phosphine.

6. The catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, The weight ratio of the first ligand to the second ligand is (5 - 8):

1.

7. A catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, The metal active component is rhodium.

8. The catalyst system for hydroformylation synthesis of butyraldehyde according to claim 1, characterized in that, Its preparation method includes: S1. Activation of rhodium precursor; S2. Ligand complexing Add the activated rhodium precursor, the first ligand, and the second ligand into a toluene solvent, and react at 80°C for 5 - 7 hours under the action of a protective gas. Then remove the solvent under reduced pressure and wash to obtain a catalyst system for hydroformylation synthesis of butyraldehyde.

9. Use of a catalyst system for the hydroformylation synthesis of butyraldehyde, characterized in that, The catalyst system for hydroformylation synthesis of butyraldehyde according to any one of claims 1 - 8 is applied to the hydroformylation synthesis of butyraldehyde.

Images