Preparation method of trimethylolpropane

Abstract

The invention discloses a preparation method of TMP (trimethylolpropane). A small amount of formaldehyde and an alkaline auxiliary agent are added into an n-butyraldehyde formaldehyde condensation reaction solution with a certain composition, and the solution is injected into a fixed bed reactor filled with a hydrogenation catalyst at a certain air speed for a hydrogenation reaction, so that the generation of a byproduct 2-methyl butanol can be greatly reduced, and the total yield of TMP is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a method for preparing trimethylolpropane. Background Art

[0002] Trimethylolpropane (TMP) is widely used as a multifunctional alcohol chemical raw material and plays a key role in many fields. It is widely used due to its excellent thermal stability, chemical resistance and excellent weather resistance. These properties make TMP an important ingredient in the production of resins, plastics, coatings, adhesives and many other chemicals.

[0003] Despite the wide application of TMP, its industrial production still faces some challenges. Currently, the industrial production of TMP mainly adopts disproportionation reaction. Although this process is very mature, there are still some unavoidable problems. During the production process, a large amount of formate by-product is produced, which not only makes product purification complicated, but also reduces the efficiency of raw material use, affecting productivity and economy.

[0004] In order to solve these challenges, condensation hydrogenation, as a new method for producing TMP, is gaining attention from researchers and the industry. According to reports in patents such as GB1535826A, US4594461A, CN1123558C, and CN101395112B, condensation hydrogenation provides a possible solution that avoids the production of formate and helps improve production efficiency and environmental sustainability.

[0005] However, in the process of preparing TMP by condensation hydrogenation method, there is still a technical difficulty in the condensation stage of n-butyraldehyde and formaldehyde. In this key step, the intermediate MMB is not only likely to continue condensation to form DMB (2,2-dimethylolbutyraldehyde), but also inevitably generates byproduct 2-ethylacrolein (EA) by dehydration reaction, and EA can generate 2-methylbutanol without economic value in subsequent hydrogenation process, and this side reaction significantly reduces the yield of overall reaction. Although the patent CN1123558C describes that EA can be recycled by distillation and then continued to be used in the condensation reactor for reuse, in the concentrated application process, EA will undergo self-condensation and cross-condensation side reactions with DMB, and the concentration process itself also increases energy consumption.

[0006]

[0007] Patent CN102304022A discloses that the byproduct EA can be used to prepare TMP through an organic base disproportionation method, but this method requires the use of 2-4 equivalents of formaldehyde as a raw material, and because the disproportionation reaction of formaldehyde produces TMP-equivalent amine formate salt, it also faces the problems of difficult by-product separation and low atom economy.

[0008] Therefore, how to reduce the formation of the hydrogenation by-product 2-methylbutanol without separating and recovering EA in the condensation hydrogenation process is of great significance for the optimization and efficiency improvement of the entire process. Summary of the invention

[0009] In order to overcome the problem that EA (2-ethylacrolein) cannot be effectively utilized in the existing condensation hydrogenation process for TMP (trimethylolpropane), the present invention provides a method for preparing trimethylolpropane, wherein EA is hydrogenated in situ to generate TMP. The method uses a condensation hydrogenation method, takes the condensation reaction liquid of the TMP process and a small amount of formaldehyde aqueous solution as raw materials, adjusts the pH of the reaction liquid by adding an alkaline auxiliary agent, and obtains TMP by one-step condensation hydrogenation under the conditions of an existing hydrogenation catalyst.

[0010]

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for preparing TMP comprises the following steps:

[0013] (1) obtaining a condensation reaction liquid from formaldehyde and n-butyraldehyde under the action of an alkaline catalyst;

[0014] (2) adding formaldehyde and an alkaline auxiliary agent to the condensation reaction liquid, passing hydrogen gas, and reacting in the presence of a hydrogenation catalyst to obtain a TMP-rich reaction liquid.

[0015] The condensation reaction in step (1) of the present invention adopts conventional conditions in the art. Preferably, in the condensation reaction liquid obtained in step (1) of the present invention, the mass ratio of formaldehyde (FA), n-butyraldehyde (BA) and 2-ethylacrolein (EA) is 1-2:1-2:18-22, and the solvent is water.

[0016] Preferably, the condensation reaction solution obtained in step (1) of the present invention further comprises components such as 2,2-dihydroxybutyraldehyde (DMB), trimethylamine (TMA), and trimethylolpropane (TMP).

[0017] In a specific embodiment, the condensation reaction liquid obtained in step (1) of the present invention comprises the following components: BA: FA: DMB: EA: TMA: TMP: water in a mass ratio of 1-2: 1-2: 28-32: 18-22: 1-2: 2-3: 300-500.

[0018] The amount of formaldehyde added in step (2) of the present invention is 0.5-2 eq (equivalent) of the initial EA molar amount in the condensation reaction solution, preferably 1-1.2 eq.

[0019] The alkaline auxiliary agent in step (2) of the present invention is an organic tertiary amine catalyst, including chain tertiary amines and / or cyclic tertiary amines.

[0020] Specifically, the specific structure of the chain tertiary amine is shown in Formula 1:

[0021]

[0022] Wherein, R1, R2, and R3 are independently selected from -CH3, -CH2CH3, -CH2CH2CH3, and -CH(CH3)CH3;

[0023] Specifically, the cyclic tertiary amine comprises one or more of hexamethylenetetramine, DBU or N-methylmorpholine.

[0024] The amount of the alkaline auxiliary agent used in step (2) of the present invention is 0.01-0.05 eq of the initial DMB mass in the condensation reaction solution.

[0025] The hydrogenation catalyst in step (2) of the present invention is a copper-based catalyst, preferably a co-precipitation copper-based catalyst, and commercially available catalysts such as Johnson Matthey Cu 4000T and Cu 2912 can be used.

[0026] The reaction temperature of step (2) of the present invention is 100-150°C, preferably 120-150°C, and the pressure is 2MpaG-4MpaG.

[0027] The hydrogenation reaction space velocity of step (2) of the present invention is 1-10mL / cm 2 cat. / h, preferably 2-5mL / cm 2 cat. / h.

[0028] Preferably, the hydrogen-to-oil ratio (molar ratio of hydrogen to initial DMB in the condensation reaction liquid) of step (2) of the present invention is 2-10.

[0029] The beneficial effect of the present invention is that, without changing the existing condensation hydrogenation process, a certain amount of alkaline additive and a small amount of formaldehyde are added to the condensation reaction liquid, so that the byproduct EA can be condensed and hydrogenated in situ in the hydrogenation reactor to generate TMP, and the yield of the condensation hydrogenation process is greatly improved without increasing the investment in the device. Compared with the prior art, the self-condensation of EA and the cross-condensation side reaction with DMB in the concentration and application process are reduced, and the occurrence of a large number of formaldehyde disproportionation reactions is also avoided, thereby improving the atom economy. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with specific implementation methods. However, those skilled in the art will understand that the embodiments described below are only part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention.

[0031] The main raw materials, n-butyraldehyde, organic amines, and formaldehyde aqueous solution were purchased from Maclean Reagent Co., Ltd., and the hydrogenation catalyst was purchased from Johnson Matthey.

[0032] <Test Method>

[0033] The qualitative analysis of each substance in the condensation reaction solution was performed using a high-resolution mass spectrometer, model: Thermo QExactive Focus;

[0034] The selectivity of the EA reaction is defined by the ratio of the key byproduct 2-MB:TMP. The lower the ratio, the higher the EA selectivity.

[0035] Material content test instrument: gas chromatography (Agilent 7820A), Rtx-5MS capillary column, FID detector, vaporization temperature 250℃, detector temperature 250℃, carrier gas is high-purity nitrogen, flow rate 30ml / min. Heating program: 50℃, 1min; 10℃ / min to 250℃, hold for 10min.

[0036] Example 1

[0037] 271 mL of 37 wt% formaldehyde aqueous solution and 4.2 mL of trimethylamine were added to 5 L of condensation reaction liquid with a composition of BA: FA: DMB: EA: TMA: TMP: water = 1: 1: 32: 22: 1: 3: 300, and the mixture was introduced into a fixed bed hydrogenation reactor through a horizontal flow pump. Under the catalysis of a Johnson Matthey Cu 2912 series catalyst, hydrogenation was performed to generate a hydrogenation reaction liquid rich in trimethylolpropane, wherein the hydrogenation reaction temperature was 120° C., the reaction pressure was 2 MPa, and the air velocity was 2 mL / cm 2 cat. / h, the hydrogen-to-oil ratio (molar ratio of hydrogen to initial DMB in the condensation reaction liquid) was 2. GC analysis of the reaction liquid at the fixed bed outlet showed 2-MB:TMP=3:97.5 (mass ratio).

[0038] Example 2

[0039] 298 mL of 37 wt% formaldehyde aqueous solution and 12.6 mL of triethylamine were added to 5 L of condensation reaction liquid with a composition of BA:FA:DMB:EA:TMA:TMP:water=1:1:30:20:1:3:330, and the mixture was introduced into a fixed bed hydrogenation reactor through a horizontal flow pump. Under the catalysis of a Johnson Matthey Cu 2912 series catalyst, hydrogenation was performed to generate a hydrogenation reaction liquid rich in trimethylolpropane, wherein the hydrogenation reaction temperature was 140°C, the reaction pressure was 3 MPa, and the air velocity was 3 mL / cm 2 cat. / h, hydrogen-to-oil ratio (molar ratio of hydrogen to initial DMB in the condensation reaction liquid) was 5. GC analysis of the reaction liquid at the fixed bed outlet showed 2-MB:TMP=1:99.5 (mass ratio).

[0040] Example 3

[0041] 325 mL of 37 wt% formaldehyde aqueous solution and 18 mL of N-methylmorpholine were added to 5 L of condensation reaction liquid with a mass composition of BA: FA: DMB: EA: TMA: TMP: water = 2: 2: 28: 18: 1: 2: 350, and the mixture was introduced into a fixed bed hydrogenation reactor through a horizontal flow pump. Under the catalysis of a Johnson Matthey Cu 2912 series catalyst, hydrogenation was performed to generate a hydrogenation reaction liquid rich in trimethylolpropane, wherein the hydrogenation reaction temperature was 150° C., the reaction pressure was a gauge pressure of 4 MPa, and the space velocity was 5 mL / cm 2 cat. / h, hydrogen-to-oil ratio (molar ratio of hydrogen to initial DMB in the condensation reaction liquid) was 8. GC analysis of the reaction liquid at the fixed bed outlet showed 2-MB:TMP=2:98 (mass ratio).

[0042] Comparative Example 1 (without addition of alkaline additive and formaldehyde)

[0043] 5L of the condensation reaction liquid with a composition of BA:FA:DMB:EA:TMA:TMP:water=2:2:28:18:1:2:350 was fed into a fixed bed hydrogenation reactor through a horizontal flow pump, and hydrogenated to generate a hydrogenation reaction liquid rich in trimethylolpropane under the catalysis of Johnson Matthey Cu 2912 series catalyst, wherein the hydrogenation reaction temperature was 150°C, the reaction pressure was 4MPa, and the space velocity was 5mL / cm 2 cat. / h, hydrogen-to-oil ratio (molar ratio of hydrogen to initial DMB in the condensation reaction liquid) was 8. GC analysis of the reaction liquid at the fixed bed outlet showed 2-MB:TMP=15:99 (mass ratio).

Claims

1. A method for preparing trimethylolpropane, comprising the following steps: Formaldehyde and an alkaline auxiliary agent are added to the condensation reaction liquid of n-butyraldehyde and formaldehyde, and hydrogen is introduced to react in the presence of a hydrogenation catalyst to obtain a reaction liquid of TMP.

2. The preparation method according to claim 1, characterized in that: The condensation reaction liquid is obtained by reacting formaldehyde and n-butyraldehyde under the action of an alkaline catalyst; Preferably, the condensation reaction liquid contains 2-ethylacrolein, and the mass ratio of formaldehyde, n-butyraldehyde and 2-ethylacrolein is 1-2:1-2:18-22.

3. The preparation method according to claim 2, characterized in that: The condensation reaction liquid contains 2,2-dihydroxybutyraldehyde, trimethylamine and trimethylolpropane, wherein the mass ratio of n-butyraldehyde: formaldehyde: 2,2-dihydroxybutyraldehyde: 2-ethylacrolein: trimethylamine: trimethylolpropane: water is 1-2: 1-2: 28-32: 18-22: 1-2: 2-3: 300-500.

4. The preparation method according to claim 2 or 3, characterized in that: The amount of formaldehyde added in the present invention is 0.5-2eq of the initial molar amount of 2-ethylacrolein in the condensation reaction solution.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The alkaline auxiliary agent of the present invention is an organic tertiary amine catalyst, including chain tertiary amine and / or cyclic tertiary amine.

6. The alkaline auxiliary agent according to claim 5, characterized in that The specific structure of the chain tertiary amine is shown in Formula 1: Wherein, R1, R2, and R3 are independently selected from -CH3, -CH2CH3, -CH2CH2CH3, or -CH(CH3)CH3.

7. The alkaline auxiliary agent according to claim 5, characterized in that The cyclic tertiary amine includes one or more of hexamethylenetetramine, DBU and N-methylmorpholine.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The amount of the alkaline auxiliary agent added in the present invention is 0.01-0.05eq of the initial 2,2-dihydroxybutyraldehyde mass.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The hydrogenation catalyst of the present invention is a co-precipitation copper-based catalyst.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The hydrogenation reaction temperature of the present invention is 100-150°C, preferably 120°C-150°C, and the pressure is 2MpaG-4MpaG; Preferably, the hydrogenation space velocity is 1-10 mL / cm 2 cat. / h, preferably 2-5mL / cm 2 cat. / h; Preferably, the molar ratio of hydrogen to the initial 2,2-dihydroxybutyraldehyde in the condensation reaction solution is 2-10.

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