A process for the preparation of hydroxyacetaldehyde by bridged catalytic hydroformylation of formaldehyde

Abstract

The application provides a method for preparing glycolaldehyde by bridging catalysis of formaldehyde hydroformylation, wherein polyoxymethylene, a rhodium precursor, a second metal, a bidentate ligand and a solvent are added into a reaction kettle, CO and H2 with a molar ratio of 1:0.4-2.5 are introduced to replace the gas in the kettle, the reaction is carried out at 90-120 DEG C under a synthesis gas pressure of 7-10 MPa for 0.5-2 h, and glycolaldehyde is prepared. In the reaction condition, a bimetallic synergistic catalyst is generated in situ, the monodentate bridging effect of the bidentate ligand can form a ligand-bridged bimetallic structure, the ligand-bridged bimetallic structure is used for formaldehyde hydroformylation, the use amount of the ligand can be effectively reduced, and the method has the advantages of mild reaction condition, significant improvement of the activity and selectivity of glycolaldehyde and the like.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a catalyst and its application in a bridging catalytic hydroformylation reaction system for the preparation of ethanolaldehyde. Background Technology

[0002] The hydroformylation of unsaturated substrates such as alkenes or aldehydes with syngas is one of the most important industrial methods for producing higher aldehydes or alcohols. Ethanaldehyde, as the smallest sugar molecule, possesses the dual properties of both aldehydes and alcohols, making it an important organic synthesis intermediate with significant applications in the chemical, food, and pharmaceutical industries, and possessing considerable market value. The hydroformylation of formaldehyde to ethanolaldehyde is a well-known technical route for converting C1 feedstocks into multi-carbon chemicals, characterized by 100% atom economy and readily available feedstocks. Furthermore, the hydroformylation of formaldehyde to ethanolaldehyde is considered a key step determining product selectivity in the one-step synthesis of ethylene glycol, and exploring this route contributes to research on the direct synthesis of ethylene glycol.

[0003] Current research on formaldehyde hydroformylation mainly focuses on rhodium, cobalt, and ruthenium complexes. Rhodium complexes, compared to cobalt and ruthenium complexes, readily generate ethanolaldehyde with better activity and selectivity under milder conditions (EP0002908 A1, ethanolaldehyde yield 43.3% at 120℃ and 14.5 MPa for 3 h). Adding organophosphorus ligands to the reaction system can improve the reactivity to some extent. However, due to the instability of monodentate ligands and their competitive coordination with CO, excess ligands are usually required to stabilize the active species, which reduces the reaction rate and selectivity (US4477685). Although rhodium-monodentate complexes can achieve formaldehyde hydroformylation, the reaction still requires high pressure and a large amount of precious metal rhodium (≥5 mmol / L) and ligands in the system. Therefore, developing a novel and efficient catalytic system to reduce ligand usage and improve the reactivity and selectivity of formaldehyde hydroformylation to ethanolaldehyde is of great significance. Summary of the Invention

[0004] This invention aims to address the shortcomings of existing technologies by proposing a bridged catalytic method for the hydroformylation of formaldehyde to prepare ethanolaldehyde. This method generates a bimetallic synergistic catalyst in situ. Through bridging coordination with bidentate ligands, a synergistic bimetallic structure is formed, enabling the highly active and selective generation of the target product, ethanolaldehyde, under low temperature and low pressure. This invention aims to provide a catalytic system generated in situ under specific reaction conditions, characterized by simple operation, high reproducibility, significantly enhanced reaction activity, and low ligand dosage.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] This invention provides a method for preparing ethanolaldehyde by bridging catalytic hydroformylation of formaldehyde. Paraformaldehyde, a rhodium precursor, a second metal, a bidentate ligand, and a solvent are added to a reaction vessel. CO and H2 in a molar ratio of 1:0.4-2.5 are introduced to replace the gas in the vessel. The reaction is carried out at 90-120°C and a syngas pressure of 7-10 MPa for 0.5-2 hours to obtain ethanolaldehyde.

[0007] Further, the molar ratio of paraformaldehyde to rhodium is 120-800, the molar ratio of bidentate ligand to rhodium is 0.5-2, and the molar ratio of the second metal to rhodium is 0.1-1; preferably, the molar ratio of paraformaldehyde to rhodium is 400, the molar ratio of bidentate ligand to rhodium is 1, and the molar ratio of the second metal to rhodium is 1.

[0008] Furthermore, the rhodium precursor is one of the following: rhodium dicarbonylacetylacetonate, (1,5-cyclooctadiene) rhodium chloride dimer, tetracarbonyl dirhodium chloride, rhodium trichloride, and rhodium trichloride trihydrate.

[0009] Furthermore, the second metal is one of cobalt octacarbonyl, manganese decacarbonyl, bis(1,5-cyclooctadiene)nickel, cobalt triacetylacetonate, and cobalt diacetylacetonate.

[0010] Furthermore, the bidentate ligand is one of bis(diphenylphosphine ethane), bis(diphenylphosphine propane), 2-(2-(diphenylphosphine)ethyl)pyridine, 2-(diphenylphosphine)ethylamine, binatidine-diphenylphosphine, and biphenyl-diphenylphosphine.

[0011] Furthermore, the rhodium precursor is rhodium dicarbonylacetylacetonate; the second metal is cobalt octacarbonyl; and the bidentate ligand is 2-(2-(diphenylphosphino)ethyl)pyridine.

[0012] Further, the solvent is N,N-dimethylacetamide or N-methylpyrrolidone or benzene or n-butanol or pyridine.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The bidentate ligand used in this invention can form a stable catalytically active species through a bridging structure. When catalyzing the hydroformylation of formaldehyde to glycolaldehyde, only an equivalent amount of ligand is required, far less than the excess ligand used in monodentate ligand-modified catalytic systems, significantly reducing the amount of ligand needed. The bidentate bridging ligand provided by this invention exhibits a unique steric effect, effectively promoting the migration and insertion of hydroxymethyl groups, resulting in highly selective glycolaldehyde formation.

[0015] 2. The in-situ generated bidentate ligand-bridged bimetallic synergistic catalyst of this invention alters the reaction mechanism of formaldehyde hydroformylation to glycolaldehyde, significantly reducing the energy barrier of the rate-determining step and improving the reaction activity. According to DFT calculations, the reaction sequentially follows four steps: HCHO insertion, CO insertion, hydrogenolysis, and H2 addition. The rate-determining step is hydrogenolysis, with an energy barrier of only 17.7 kcal / mol. The ligand-bridged bimetallic catalyst contains bridging hydrides, which act as the hydrogen source in the hydrogenolysis step, resulting in intramolecular hydrogenolysis. This exhibits significant advantages compared to single-metal systems and monodentate ligand systems.

[0016] 3. The bidentate ligand-bridged bimetallic catalyst provided by this invention can significantly improve the reactivity and selectivity of hydroformylation to ethanolaldehyde. The selectivity for ethanolaldehyde production via bridged bimetallic catalysis is 96.8% after 2 hours of reaction, with a TOF of 79.4 h. -1 .

[0017] 4. The hydroformylation method for generating glycolaldehyde provided by this invention can use as little as 1.25 mmol / L of the precious metal rhodium, which reduces the amount of rhodium used and has great economic value and market prospects.

[0018] 5. The formaldehyde hydroformylation reaction system described in this invention is simple, the catalyst can be generated in situ under reaction conditions, the operation is simple, the repeatability is high, and it is suitable for large-scale production. Detailed Implementation

[0019] The following detailed description of the embodiments further illustrates the present invention. It should be noted that the following embodiments are illustrative and not limiting, and should not be construed as limiting the scope of protection of the present invention. All raw materials used in the following embodiments and comparative examples are commercially available. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions and conditions described in the manual, or as recommended by the manufacturer. Unless otherwise specified, all general equipment and materials used are commercially available.

[0020] Example 1

[0021] Weigh out 19.7 mg of rhodium dicarbonyl acetylacetone, 13.1 mg of cobalt octacarbonyl (cobalt to rhodium molar ratio of 1), 900.9 mg of paraformaldehyde (formaldehyde to rhodium molar ratio of 400), and 22.3 mg of 2-(2-(diphenylphosphino)ethyl)pyridine ligand (ligand to rhodium molar ratio of 1). Measure 30 mL of N,N-dimethylacetamide solvent and add it to a 100 mL quartz-lined container. Immediately seal the quartz-lined container in a stainless steel high-pressure reactor. Purge the reactor with syngas (CO to H2 molar ratio of 1:1) multiple times to displace the air inside. After purging the air, introduce syngas at 2.5 MPa and begin heating. Raise the temperature to 110 °C, then pressurize to 10 MPa and react at 600 rpm for 2 hours. After the reaction is complete, immediately cool to room temperature in a water bath.

[0022] After the reaction, isopropanol was used as an internal standard, and the post-reaction solution was analyzed by Shimadzu 2014C GC gas chromatography. The selectivity for the target product, glycolaldehyde, was 96.8%, and the TOF was 79.4 h. -1 .

[0023] Example 2

[0024] Except for replacing the octacarbonyl dicobalt with 14.9 mg of decacarbonyl dimanganese (manganese to rhodium molar ratio of 1) added to the quartz liner, the reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 95.9%, and the TOF was 51.0 h. -1 .

[0025] Example 3

[0026] Except for replacing the octacarbonyl cobalt with 21.1 mg of bis(1,5-cyclooctadiene) nickel (nickel to rhodium molar ratio of 1) in the quartz liner, the reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 96.2%, and the TOF was 37.7 h. -1 .

[0027] Comparative Example 1

[0028] Except for the absence of cobalt octacarbonyl, the reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 93.2%, and the TOF was 37.5 h. -1 .

[0029] Comparative Example 2

[0030] Except for the absence of rhodium dicarbonyl acetylacetone, the reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 90.5%, and the TOF was 8.3 h. -1 .

[0031] Comparative Example 3

[0032] The difference from Example 1 is that the bidentate ligand 2-(2-(diphenylphosphino)ethyl)pyridine ligand was replaced with 20.7 mg of the monodentate ligand triphenylphosphine. All other reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 96.8%, and the TOF was 30.8 h. -1 .

[0033] Comparative Example 4

[0034] The difference from Example 1 is that the second metal, octacarbonyl dicobalt, was replaced with 10.3 mg of copper chloride; all other reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 55.3%, and the TOF was 28.9 h. -1 .

[0035] Example 4

[0036] Except for adding 11.1 mg of 2-(2-(diphenylphosphino)ethyl)pyridine ligand (the molar ratio of ligand to rhodium was 0.5) to the quartz liner, the reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 93.8%, and the TOF was 56.4 h. -1 .

[0037] Example 5

[0038] Except for adding 44.6 mg of 2-(2-(diphenylphosphino)ethyl)pyridine ligand (molar ratio of ligand to rhodium = 2) to the quartz liner, the reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 97.4%, and the TOF was 42.0 h. -1 .

[0039] Example 6

[0040] Except for replacing the octacarbonyl cobalt with 27.3 mg of cobalt triacetylacetone (cobalt to rhodium molar ratio of 1) in the quartz liner, the reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 96.6%, and the TOF was 71.0 h. -1 .

[0041] Example 7

[0042] Except for replacing the octacarbonyl cobalt with 19.5 mg of diacetylacetone cobalt (cobalt to rhodium molar ratio of 1) added to the quartz liner, the reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 96.8%, and the TOF was 70.5 h. -1 .

[0043] Example 8

[0044] Except for replacing the rhodium dicarbonyl acetylacetone with 18.9 mg of (1,5-cyclooctadiene) rhodium chloride dimer in the quartz liner, the reaction conditions were identical to those in Example 1. The selectivity for the target product, glycolaldehyde, was 97.6%, and the TOF was 59.6 h. -1 .

[0045] Example 9

[0046] Except for the reaction time, which was changed to 1 hour, all other reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 95.8%, and the TOF was 80.0 h. -1 .

[0047] Example 10

[0048] Except for the reaction time, which was changed to 0.5 h, all other reaction conditions were exactly the same as in Example 1. The selectivity for the target product, glycolaldehyde, was 95.7%, and the TOF was 84.9 h. -1 .

[0049] Example 11

[0050] Weigh 9.9 mg of rhodium dicarbonyl acetylacetone, 6.5 mg of cobalt octacarbonyl (molar ratio of cobalt to rhodium is 1), 900.9 mg of paraformaldehyde (molar ratio of formaldehyde to rhodium is 800), and 11.1 mg of 2-(2-(diphenylphosphino)ethyl)pyridine ligand (molar ratio of ligand to rhodium is 1). Measure 30 mL of N,N-dimethylacetamide solvent and add it to a 100 mL quartz liner. React at 110 °C and 10 MPa for 1 h. The remaining operations are exactly the same as in Example 1.

[0051] Gas chromatography analysis showed that the selectivity for the target product, glycolaldehyde, was 96.5%, and the time-to-free (TOF) was 115.5 h. -1 .

[0052] Compared with Examples 1-3 and Comparative Examples 1-4, under the reaction conditions described in this invention, the TOF and selectivity of ethanolaldehyde in Examples 1 (rhodium concentration of 2.5 mmol / L, second metal cobalt), 2 (rhodium concentration of 2.5 mmol / L, second metal manganese), and 3 (rhodium concentration of 2.5 mmol / L, second metal nickel) were all higher than those in the comparative examples. This indicates that the bimetallic structure of bidentate ligands bridged in situ under the reaction conditions can significantly improve the activity and selectivity of the target product.

[0053] In Example 1, the ligand-to-rhodium ratio was 1:1; in Example 4, it was 0.5:1; and in Example 5, it was 2:2. All three examples exhibited good activity and selectivity for ethanolaldehyde. This indicates that the bidentate ligands used can generate stable catalytically active species, requiring only a low amount of ligand in the reaction system, which effectively reduces the amount of ligand compared to monodentate ligand catalytic systems. In Example 1, the molar amount of coordinating atoms was the same as the sum of the molar amounts of the two metals, resulting in the optimal reaction activity. This indicates that during the reaction, the bidentate ligands connected the two metals in a monodentate bridging mode, generating a ligand-bridged bimetallic catalyst in situ. This catalyst then lowered the rate-determining energy barrier through a unique formaldehyde hydroformylation reaction mechanism, thereby enhancing the activity for ethanolaldehyde formation.

[0054] To explore the universality of the synergistic effect of ligand-bridged bimetallic catalysts in the hydroformylation of formaldehyde to ethanolaldehyde, this invention employs various rhodium and cobalt precursors. The TOF of the ethanolaldehyde in Example 6 is 71.0 h⁻¹. -1 The TOF of ethanolaldehyde in Example 7 was 70.5 h. -1 The TOF of ethanolaldehyde in Example 8 was 59.6 h. -1 All of these significantly promote reactivity. The bridging bimetallic synergistic effect provided by this invention has universality.

[0055] In Example 11, the rhodium concentration was 1.25 mmol / L, and the TOF for the formation of glycolaldehyde after 1 hour of reaction was 115.5 h. -1 This result demonstrates that bidentate ligand-bridged bimetallic synergistic catalysts can enhance reaction rate, activity, and selectivity while reducing the amount of precious metals required.

[0056] Matters not covered in this invention are common knowledge.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing ethanolaldehyde by bridging catalytic hydroformylation of formaldehyde, characterized in that, Paraformaldehyde, a rhodium precursor, a second metal, a bidentate ligand, and a solvent are added to a reactor to generate a bidentate ligand-bridged bimetallic synergistic catalyst in situ. CO and H2 in a molar ratio of 1:0.4-2.5 are introduced to replace the gas in the reactor. The reaction is carried out at 90-120 °C and a syngas pressure of 7-10 MPa for 0.5-2 h to obtain glycolaldehyde. The molar ratio of paraformaldehyde to rhodium is 120-800, the molar ratio of bidentate ligand to rhodium is 0.5-2, and the molar ratio of the second metal to rhodium is 0.1-1. The second metal is one of cobalt octacarbonyl, cobalt triacetylacetonate, and cobalt diacetylacetonate; The bidentate ligand is one of bis(diphenylphosphine ethane), bis(diphenylphosphine propane), 2-(2-(diphenylphosphino)ethyl)pyridine, 2-(diphenylphosphino)ethylamine, binatidine diphenylphosphine, and biphenyl diphenylphosphine; The rhodium precursor is one of the following: rhodium dicarbonyl acetylacetonate, (1,5-cyclooctadiene) rhodium chloride dimer, tetracarbonyl dichloride, rhodium trichloride, and rhodium trichloride trihydrate.

2. The method for preparing glycolaldehyde by bridging catalytic hydroformylation of formaldehyde according to claim 1, characterized in that, The rhodium precursor is rhodium dicarbonylacetylacetone; the second metal is cobalt octacarbonyl; and the bidentate ligand is 2-(2-(diphenylphosphino)ethyl)pyridine.

3. The method for preparing glycolaldehyde by bridging catalytic hydroformylation of formaldehyde according to claim 1, characterized in that, The solvent is N,N-dimethylacetamide, N-methylpyrrolidone, benzene, n-butanol, or pyridine.

4. The method for preparing ethanolaldehyde by bridging catalytic hydroformylation of formaldehyde according to claim 1, characterized in that, The molar ratio of paraformaldehyde to rhodium is 400, the molar ratio of bidentate ligand to rhodium is 1, and the molar ratio of the second metal to rhodium is 1.