A method for preparing 2,2-dimethylolbutyraldehyde and trimethylolpropane

Abstract

The invention provides a method for preparing 2,2-dimethylolbutyraldehyde (DMB) and trimethylolpropane (TMP). The method uses formaldehyde, n-butyraldehyde and secondary alcohol as raw materials, and an aldol condensation reaction occurs under the catalyst of an organic base. During the process, a Meerwein-Ponndorf-Verley (MPV) reaction occurs under the catalysis of a catalyst to suppress the occurrence of a Cannizzaro reaction, reduce the generation of formic acid, obtain a condensation reaction liquid of high-content 2,2-dimethylolbutyraldehyde (DMB), and the reaction liquid is hydrogenated to obtain trimethylolpropane (TMP). The method of the present invention has the advantages of high condensation yield, few by-products, high total yield of TMP, and low cost.

Description

Technical Field

[0001] The invention belongs to the field of organic chemical synthesis, and particularly relates to a method for preparing 2,2-dihydroxymethylbutyraldehyde and trimethylolpropane. Background Art

[0002] Trimethylolpropane (TMP) is a widely used polyol with the advantages of good thermal stability, acid and alkali resistance, and good weather resistance.

[0003] The current industrial production of TMP is mainly based on the disproportionation route, which has a relatively mature process. However, due to the limitations of chemical reactions, a large amount of formate will be produced as a by-product, making product separation difficult and having poor atom economy.

[0004] Therefore, the production of TMP by hydrogenation has attracted more and more attention. Patents CN112517018, CN104892364, CN108772073, CN110121486 and other patents have reported hydrogenation catalysts for producing TMP, but the condensation step of n-butyraldehyde and formaldehyde before hydrogenation will inevitably undergo Cannizzaro disproportionation reaction and condensation. The generated DMB is easy to react with formic acid to form DMB formate, accounting for 1-3wt% of the total condensation liquid (ref: CN201410362861.4). Therefore, improving the efficiency of the condensation step is very important for improving the total yield of TMP by hydrogenation. Summary of the invention

[0005] One of the purposes of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for preparing 2,2-dimethylolbutyraldehyde (DMB) and using it to obtain trimethylolpropane (TMP) in high yield. The method has the advantages of high condensation yield, few by-products, high total yield of TMP, and low cost.

[0006] In order to achieve the above invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing 2,2-dimethylolbutyraldehyde and trimethylolpropane, the method comprising the following steps:

[0008] S1: Formaldehyde, n-butyraldehyde and an organic base undergo an aldol condensation reaction to obtain 2,2-dimethylolbutyraldehyde. During the reaction, a secondary alcohol and a catalyst are added, and part of the 2,2-dimethylolbutyraldehyde undergoes a Meerwein-Ponndorf-Verley (MPV) reaction;

[0009] S2: After filtering and concentrating the 2,2-dihydroxymethylbutyraldehyde obtained in S2, hydrogenating it in a hydrogen atmosphere to obtain trimethylolpropane;

[0010] Optionally, S3: filtering, concentrating and distilling the 2,2-dimethylolbutyraldehyde reaction solution obtained in S1 to obtain 2,2-dimethylolbutyraldehyde.

[0011] The inventors have found that in the process of preparing dimethylolbutyraldehyde (DMB) by aldol condensation of n-butyraldehyde and formaldehyde under the catalysis of alkali, about 10% of DMB will still undergo Cannizzaro disproportionation reaction with the raw material formaldehyde to produce formic acid and formate esters, formate salts and other by-products. When the aldol condensation proceeds to a certain extent, the inventors have found that adding isopropanol and a catalyst can make DMB more likely to undergo MPV reaction to form TMP without disproportionation reaction, thereby reducing the generation of by-products and improving the overall yield. The reactions involved are schematically shown as follows:

[0012]

[0013] In one embodiment of the present invention, the formaldehyde in S1 is a formaldehyde aqueous solution.

[0014] In one embodiment of the present invention, the molar ratio of n-butyraldehyde, formaldehyde, organic base and water in the aldol condensation reaction described in S1 is 1:(2-6):(0.02-0.2):(1-5).

[0015] In one embodiment of the present invention, the organic base in S1 is an alkylamine compound, preferably one or more of triethylamine, trimethylamine, and diisopropylethylamine.

[0016] In one embodiment of the present invention, the temperature of the aldol condensation reaction before adding the secondary alcohol and the catalyst in S1 is 30-65°C.

[0017] In one embodiment of the present invention, S1 is reacted in an inert gas atmosphere.

[0018] In one embodiment of the present invention, the secondary alcohol and the catalyst in S1 are added 10 to 90 minutes after the start of the aldol condensation, preferably 10 to 30 minutes.

[0019] In one embodiment of the present invention, the secondary alcohol in S1 is a C2-C12 secondary alcohol, preferably one or more of ethanol, isopropanol, and isobutanol, more preferably isopropanol.

[0020] In one embodiment of the present invention, the catalyst in S1 is a metal-containing catalyst that catalyzes the MPV reaction, preferably a metal alkoxy reagent, more preferably one or more of aluminum triisopropoxide, trimethoxyaluminum, and samarium triisopropoxide, more preferably aluminum triisopropoxide; preferably, the amount of the secondary alcohol is 0.1-1 times the molar amount of n-butyraldehyde, preferably 0.2-0.5 times; preferably, the amount of the catalyst is 0.01-1 times the molar amount of n-butyraldehyde, preferably 0.02-0.5 times.

[0021] In one embodiment of the present invention, after adding the secondary alcohol and the catalyst, S1 continues to react for 0.5 to 5 hours, preferably 0.5 to 2 hours; preferably, the temperature of continuing the reaction after adding the secondary alcohol and the catalyst is the same as that of the condensation reaction.

[0022] In one embodiment of the present invention, the condensation reaction liquid obtained in S1 has a formic acid content of ≤0.05wt%, preferably ≤0.01wt%; a formate content of ≤0.05wt%, preferably ≤0.01wt%; and a formate ester content of ≤0.1wt%, preferably ≤0.03wt%, based on the total mass of the condensation reaction liquid.

[0023] In one embodiment of the present invention, the condensation reaction liquid in S2 is filtered and concentrated, and then diluted to a DMB concentration of 1-15 wt% during the hydrogenation reaction; preferably, the diluent is one or more of water, methanol, and TMP aqueous solution.

[0024] In one embodiment of the present invention, a metal hydrogenation catalyst is added to S2, preferably one or more of copper-based, nickel-based, and palladium-based catalysts having hydrogenation activity, more preferably a copper-based catalyst having hydrogenation activity. The above catalysts are all commonly used hydrogenation catalysts in the art.

[0025] In one embodiment of the present invention, the liquid hourly space velocity of the S2 hydrogenation reaction is 0.5-8 g / gcat. / h.

[0026] In one embodiment of the present invention, the S2 hydrogen to oil ratio is (50-200):1.

[0027] In one embodiment of the present invention, S2 has a temperature of 90-120°C and a pressure of 2-4 MPaG.

[0028] In one embodiment of the present invention, the S3 distillation conditions are: plate number 10-40, temperature 50-200°C, pressure 0.2-50 kPaA, and reflux ratio 0.2-20.

[0029] Another object of the present invention is to provide 2,2-dimethylolbutyraldehyde.

[0030] A 2,2-dihydroxymethylbutyraldehyde is prepared by the above method.

[0031] Another object of the present invention is to provide a trimethylolpropane.

[0032] A trimethylolpropane is prepared by the above method.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] (1) The conversion rate of n-butyraldehyde is ≥98%, and the MPV reaction inhibits the Cannizzaro disproportionation reaction, which greatly reduces by-products such as formic acid, formate esters, and formate salts, simplifies the process flow, and reduces the equipment investment.

[0035] (2) The reduction of TMP formate improves the efficiency of DMB hydrogenation, making the total yield of TMP reach more than 95%, thus reducing the production cost. DETAILED DESCRIPTION

[0036] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0037] The content of formic acid and formates was determined by acid-base titration;

[0038] The content and conversion rate of butyraldehyde and DMB, the content of formate and TMP were measured by gas chromatography:

[0039] Gas chromatograph: Agilent 7890; chromatographic column: Rtx-5MS; inlet temperature: 250°C; split ratio 10:1; H2:Air:N2=40:400:30 (mL / min), column flow rate 5.0 mL / min; heating program: 50°C for 1 min, increase the temperature from 50°C to 250°C at a rate of 10°C / min, and keep the temperature at 250°C for 10 min; FID detector temperature: 250°C.

[0040] Reagent information: 37wt% formaldehyde aqueous solution, n-butyraldehyde (AR), triethylamine (AR), trimethylamine (30wt% aqueous solution), diisopropylethylamine (AR), ethanol (AR), isopropanol (AR), isobutyl alcohol (AR), triisopropylaluminum (AR), trimethylaluminum (AR), triisopropylsamarium (AR): Inokite; Cu catalyst 4000T, 60 / 35T, 2912: Johnson Matthey Catalyst Co., Ltd.

[0041] Equipment information: Condensation reactor: volume 2L, material 316L; fixed bed reactor: reaction tube length 1.2m, diameter 32mm, material 316L.

[0042] Example 1

[0043] 288.4 g (4.0 mol) of n-butyraldehyde, 746.7 g (9.2 mol) of 37 wt% formaldehyde aqueous solution, 40.5 g (0.4 mol) of triethylamine and 288 g (16 mol) of water were added into a condensation reactor. After reacting at 65°C and 0.5 MPaG for 10 min, 48.1 g (0.8 mol) of isopropanol and 163.4 g (0.8 mol) of triisopropylaluminum were added and the reaction was continued for 0.5 h.

[0044] The condensation reaction liquid was filtered through a conventional Buchner funnel, and then the light components and part of the water were removed by a rotary evaporator under vacuum to make the water content after concentration 50wt%, and the concentration of DMB in the condensation reaction concentrate was diluted to 1wt% with methanol. The hydrogenation reaction was carried out in a continuous trickle fixed bed reactor filled with a copper-based catalyst 4000T, with a liquid hourly space velocity of 8g / gcat. / h, a hydrogen-to-oil ratio of 50:1, a temperature of 120°C, and a pressure of 4MPaG to obtain a TMP reaction liquid.

[0045] The formic acid content in the condensation reaction liquid was analyzed to be 0.050wt%, the formate content was 0.031wt%, and the formate content was 0.095wt%. The butyraldehyde conversion rate was 99.5% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 95.2%.

[0046] Example 2

[0047] 216.3 g (3.0 mol) of n-butyraldehyde, 730.5 g (9.0 mol) of 37 wt% formaldehyde aqueous solution, 60.7 g (0.6 mol) of triethylamine and 270 g (15 mol) of water were added into a condensation reactor. After reacting for 60 min at 40°C and 0.5 MPaG, 54.1 g (0.9 mol) of isopropanol and 183.8 g (0.3 mol) of triisopropylaluminum were added and the reaction was continued for 2 h.

[0048] The condensation reaction liquid was filtered through a conventional Buchner funnel, and then the light components and part of the water were removed by a rotary evaporator under vacuum to make the water content after concentration 50wt%, and the concentration of DMB in the condensation reaction concentrate was diluted to 5wt% with a TMP aqueous solution. The hydrogenation reaction was carried out in a continuous trickle fixed bed reactor filled with a copper catalyst 60 / 35T at a liquid hourly space velocity of 2g / gcat. / h, a hydrogen-to-oil ratio of 150:1, a temperature of 110°C, and a pressure of 3MPaG to obtain a TMP reaction liquid.

[0049] The formic acid content in the condensation reaction liquid was analyzed to be 0.003 wt%, the formate content was 0.048 wt%, and the formate content was 0.043 wt%. The butyraldehyde conversion rate was 99.3% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 97.0%.

[0050] Example 3

[0051] 144.2 g (2.0 mol) of n-butyraldehyde, 973.9 g (12.0 mol) of 37 wt% formaldehyde aqueous solution, 25.8 g (0.2 mol) of diisopropylethylamine and 144 g (8.0 mol) of water were added into a condensation reactor. After reacting for 10 min at 30°C and 0.5 MPaG, 74.1 g (1.0 mol) of isobutanol and 120.1 g (1.0 mol) of trimethoxyaluminum were added and the reaction was continued for 5 h.

[0052] The condensation reaction liquid was conventionally filtered through a Buchner funnel, and then the light components and part of the water were removed by a rotary evaporator under vacuum to make the water content after concentration 50wt%. The concentration of DMB in the condensation reaction concentrate was diluted to 15wt% with methanol, and hydrogenation reaction was carried out in a continuous trickle fixed bed reactor filled with a copper-based catalyst 2912 at a liquid hourly space velocity of 0.5g / gcat. / h, a hydrogen-to-oil ratio of 200:1, a temperature of 90°C, and a pressure of 2MPaG to obtain a TMP reaction liquid.

[0053] The formic acid content in the condensation reaction liquid was analyzed to be 0.012wt%, the formate content was 0.022wt%, and the formate content was 0.016wt%. The butyraldehyde conversion rate was 98.6% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 96.1%.

[0054] Example 4

[0055] 360.6 g (5.0 mol) of n-butyraldehyde, 852.2 g (10.5 mol) of 37 wt% formaldehyde aqueous solution, 49.3 g (0.05 mol) of 30 wt% trimethylamine and 90 g (5.0 mol) of water were added into a condensation reactor. After reacting for 30 min at 45°C and 0.5 MPaG, 23.0 g (0.5 mol) of ethanol and 32.8 g (0.1 mol) of samarium triisopropoxide were added and the reaction was continued for 1 h.

[0056] The condensation reaction liquid was filtered through a conventional Buchner funnel, and then the light components and part of the water were removed by a rotary evaporator under vacuum to make the water content after concentration 50wt%, and the concentration of DMB in the 70% condensation reaction concentrate was diluted to 3wt% with water. The hydrogenation reaction was carried out in a continuous trickle fixed bed reactor filled with a copper-based catalyst 4000T at a liquid hourly space velocity of 4g / gcat. / h, a hydrogen-to-oil ratio of 160:1, a temperature of 115°C, and a pressure of 3.5MPaG to obtain a TMP reaction liquid.

[0057] The formic acid content in the condensation reaction liquid was analyzed to be 0.008wt%, the formate content was 0.004wt%, and the formate content was 0.021wt%. The butyraldehyde conversion rate was 98.9% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 97.4%.

[0058] The remaining 30% of the condensation reaction concentrated liquid material enters the light removal tower to remove the light components at the top of the tower. The theoretical plate number is 10, the pressure is 20 kPaA, the temperature is 80°C, and the reflux ratio is 10; the material in the bottom of the light removal tower enters the heavy removal tower to remove the heavy components at the bottom of the tower. The theoretical plate number is 40, the pressure is 0.2 kPaA, the temperature is 180°C, the reflux ratio is 0.3, and DMB is produced from the top of the tower.

[0059] Comparative Example 1

[0060] Compared with Example 1, the difference is that there is no step of adding secondary alcohol, and the rest is the same as Example 1.

[0061] The formic acid content in the condensation reaction liquid was analyzed to be 0.22wt%, the formate content was 0.24wt%, and the formate content was 1.57wt%. The butyraldehyde conversion rate was 96.3% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 79.3%.

[0062] Comparative Example 2

[0063] Compared with Example 1, the difference is that there is no step of adding a catalyst, and the rest is the same as Example 1.

[0064] The formic acid content in the condensation reaction liquid was analyzed to be 0.13wt%, the formate content was 0.45wt%, and the formate content was 1.34wt%. The butyraldehyde conversion rate was 92.2% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 81.6%.

[0065] Comparative Example 3

[0066] Compared with Example 1, the difference is that there is no step of adding secondary alcohol and catalyst, and the rest is the same as Example 1.

[0067] The formic acid content in the condensation reaction liquid was analyzed to be 0.16wt%, the formate content was 0.12wt%, and the formate content was 2.12wt%. The butyraldehyde conversion rate was 96.4% based on n-butyraldehyde. The TMP content in the hydrogenation reaction liquid was analyzed, and the total TMP yield was 78.5%.

Claims

1. A method for preparing 2,2-dimethylolbutyraldehyde and trimethylolpropane, characterized in that: The method comprises the following steps: S1: Formaldehyde, n-butyraldehyde and an organic base undergo an aldol condensation reaction to obtain 2,2-dihydroxymethylbutyraldehyde, and a secondary alcohol and a catalyst are added during the reaction to produce an MPV reaction; S2: filtering and concentrating the 2,2-dihydroxymethylbutyraldehyde obtained in S1, and then hydrogenating it in a hydrogen atmosphere to obtain trimethylolpropane; Optionally, S3: filtering, concentrating and distilling the 2,2-dimethylolbutyraldehyde reaction solution obtained in S1 to obtain 2,2-dimethylolbutyraldehyde; Wherein, the secondary alcohol described in S1 is a C2-C12 secondary alcohol.

2. The method according to claim 1, characterized in that The formaldehyde described in S1 is a formaldehyde aqueous solution; And / or, in the aldol condensation reaction described in S1, the molar ratio of n-butyraldehyde, formaldehyde, organic base and water is 1:(2-6):(0.02-0.2):(1-5); And / or, the organic base in S1 is an alkylamine compound; and / or, the temperature of the aldol condensation reaction before adding the secondary alcohol and the catalyst in S1 is 30 to 65° C.; And / or, S1 is reacted in an inert gas atmosphere.

3. The method according to claim 2, characterized in that The organic base in S1 is one or more of triethylamine, trimethylamine and diisopropylethylamine.

4. The method according to claim 1 or 2, characterized in that: The secondary alcohol and the catalyst are added in step S1 10 to 90 minutes after the start of the aldol condensation; And / or, the secondary alcohol in S1 is one or more of ethanol, isopropanol, and isobutanol; And / or, the catalyst described in S1 is a metal-containing catalyst that catalyzes MPV reaction.

5. The method according to claim 4, characterized in that The secondary alcohol and the catalyst are added 10 to 30 minutes after the start of the aldol condensation in S1; And / or, the secondary alcohol in S1 is isopropanol; And / or, the catalyst in S1 is a metal alkoxy reagent; The amount of the secondary alcohol in S1 is 0.1-1 times the molar amount of n-butyraldehyde; The amount of the catalyst in S1 is 0.01-1 times the molar amount of n-butyraldehyde.

6. The method according to claim 5, characterized in that S1 The catalyst is one or more of aluminum triisopropoxide, aluminum trimethoxide, and samarium triisopropoxide; The amount of the secondary alcohol in S1 is 0.2-0.5 times the molar amount of n-butyraldehyde; The amount of the catalyst in S1 is 0.02-0.5 times the molar amount of n-butyraldehyde.

7. The method according to claim 6, characterized in that The catalyst in S1 is aluminum triisopropoxide.

8. The method according to claim 1, characterized in that After adding the secondary alcohol and the catalyst to S1, the reaction was continued for 0.5 to 5 hours.

9. The method according to claim 8, characterized in that S1 adds secondary alcohol and catalyst and continues the reaction for 0.5 to 2 hours; The temperature at which the reaction is continued after the secondary alcohol and the catalyst are added to S1 is the same as that of the condensation reaction.

10. The method according to claim 1, characterized in that In the condensation reaction liquid obtained in S1, based on the total mass of the condensation reaction liquid, the formic acid content is ≤0.05wt%; the formate content is ≤0.05wt%; and the formate ester content is ≤0.1wt%.

11. The method according to claim 10, characterized in that In the condensation reaction liquid obtained in S1, based on the total mass of the condensation reaction liquid, the content of formic acid is ≤0.01wt%; the content of formate salt is ≤0.01wt%; and the content of formate ester is ≤0.03wt%.

12. The method according to claim 1, characterized in that Said S2 adds a metal hydrogenation catalyst; and / or, the liquid hourly space velocity of the S2 hydrogenation reaction is 0.5-8 g / gcat. / h; and / or, the hydrogen-to-oil ratio of S2 is (50-200):1; And / or, S2 temperature is 90-120°C, pressure is 2-4MPaG.

13. The method according to claim 12, characterized in that The metal hydrogenation catalyst added to S2 is one or more of copper-based, nickel-based, and palladium-based catalysts having hydrogenation activity.

14. The method according to claim 13, characterized in that The metal hydrogenation catalyst added to S2 is a copper-based catalyst with hydrogenation activity.

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