Method for preparing trihydroxymethyl aminomethane by trickle bed process

Abstract

The invention provides a method for preparing trihydroxymethyl aminomethane by a trickle bed process. According to the method disclosed by the invention, Tris is prepared by hydrogenation of trihydroxymethyl nitromethane, continuous improvement of a trihydroxymethyl nitromethane hydrogenation process is realized by utilizing an adiabatic trickle bed process, and the process adopts a specific hydrogen-alcohol ratio (molar ratio of hydrogen to trihydroxymethyl nitromethane) and specific reaction pressure; the reaction temperature and the gas phase flow velocity in the reactor are controlled by internal gas phase heat extraction, the heat extraction efficiency is ensured, the good Tris yield is also ensured, the THNM conversion rate reaches 100%, the Tris selectivity reaches 90% or above, the product purity is high, and the industrial practicability is good.

Description

Technical Field

[0001] The invention relates to the field of tris(hydroxymethyl)aminomethane synthesis, and in particular to a method for preparing tris(hydroxymethyl)aminomethane by a trickle bed process. Background Art

[0002] Tris(hydroxymethyl)aminomethane, also known as tromethamine, abbreviated as Tris in English, is an important organic chemical raw material, widely used in biomedicine and scientific research.

[0003] Industrially, the synthesis of tris(hydroxymethyl)aminomethane mostly adopts a condensation-hydrogenation two-step method, in which the hydrogenation step is to prepare tris(hydroxymethyl)aminomethane by hydrogenation of tris(hydroxymethyl)nitromethane (THNM). At present, the hydrogenation process generally adopts a kettle-type intermittent reaction. For example, CN113200877A discloses a method for preparing tris(hydroxymethyl)aminomethane, in which condensation and hydrogenation both adopt a kettle-type intermittent reaction process. For another example, the hydrogenation process adopted by the process for preparing tris(hydroxymethyl)aminomethane by hydrogenation of tris(hydroxymethyl)nitromethane (THNM) disclosed in CN115611751A, CN1800142A and CN100343266C is also kettle-type hydrogenation. However, for the high-risk process of hydrogenation reaction, intermittent operation is prone to potential safety hazards, causing inestimable losses, and requires a large amount of manual intervention in operation, and the degree of automation and intelligence is low.

[0004] The fixed bed process can also be used for the hydrogenation of THNM to prepare trishydroxymethylaminomethane. CN115872875A discloses a process for the continuous fixed bed THNM hydrogenation to prepare Tris. The operating conditions disclosed in the patent are a gas-liquid ratio of 50 to 500:1, and the reaction temperature is controlled at 30 to 90°C. Since the hydrogenation of THNM is a highly exothermic reaction, under the gas-liquid ratio conditions disclosed in the patent, external heat exchange is required to maintain the reaction temperature below 90°C. For the reactor, the patent further discloses that the fixed bed reactor used is a shell-and-tube reactor and a series reactor, and a shell-and-tube reactor is used in the embodiment. It can be seen that the fixed bed reactor involved in the patent is a gas-liquid-solid three-phase shell-and-tube fixed bed reactor that can take heat externally, but in engineering, this gas-liquid-solid three-phase shell-and-tube fixed bed reactor is difficult to achieve uniform liquid phase distribution, and industrial amplification is difficult, so the industrialization prospect of the patent is not optimistic. Summary of the invention

[0005] In view of the above-mentioned problems in the prior art, the present invention utilizes an adiabatic trickle bed process to achieve a continuous improvement in the tris(hydroxymethylnitromethane) hydrogenation process. The process adopts a specific hydrogen-to-alcohol ratio (the molar ratio of hydrogen to tris(hydroxymethylnitromethane)) and a specific reaction pressure to achieve internal gas phase heat extraction to control the reaction temperature and the gas phase flow rate in the reactor, thereby ensuring both the heat extraction efficiency and a good Tris yield.

[0006] In view of this, the technical solution of the present invention is as follows:

[0007] The present invention provides a method for preparing tris(hydroxymethyl)aminomethane by a trickle bed process, the method comprising the following steps:

[0008] (1) dissolving trihydroxymethylnitromethane (THNM) in a mixed solvent of methanol and water to prepare a hydrogenation raw material liquid;

[0009] (2) respectively introducing hydrogen and the hydrogenation feed liquid into a trickle bed reactor loaded with a nickel-based catalyst, wherein the hydrogenation feed liquid is fully mixed with hydrogen through a liquid distributor in the trickle bed reactor, and undergoes a catalytic hydrogenation reaction through a catalyst bed; wherein the molar ratio of hydrogen to tris(hydroxymethylnitromethane) (THNM) is 80 to 400:1, and the reaction pressure is 3 to 15 MPa;

[0010] (3) The reaction materials are cooled after exiting the trickle bed reactor, and then subjected to gas-liquid separation to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane.

[0011] In the present invention, since the THNM hydrogenation reaction is a highly exothermic reaction, in order to control the reaction temperature (45-85° C.) and improve the selectivity of the target product, the present invention adopts a high hydrogen-to-alcohol ratio (the molar ratio of hydrogen to THNM is 80-400:1) to fully remove the reaction heat through the gas flow in the trickle bed reactor and the gasification of the solvent methanol in the hydrogenation feed liquid to achieve the control of the reaction temperature.

[0012] At the same time, since the large airflow in the trickle bed reactor leads to a short gas-liquid contact time, the heat extraction effect is reduced. The present invention reduces the superficial airflow velocity by a relatively large reaction pressure (3-15 MPa). In addition, in the THNM hydrogenation reaction, the main reaction hydrogenation reaction and the raw material decomposition reaction are in a competitive relationship. A higher reaction pressure is provided in the trickle bed reactor to increase the hydrogen concentration in the reaction liquid, reduce the possible control of the reaction rate caused by the mass transfer resistance of hydrogen during the reaction, and thus improve the reaction rate and selectivity.

[0013] In some embodiments, the trickle bed reactor is a single-channel plug flow adiabatic reactor, and both the gas phase and the liquid phase enter from the top and exit from the bottom.

[0014] In some embodiments, in step (1), in the hydrogenation feed liquid, the concentration of trimethylolnitromethane (THNM) is 8-18wt%, preferably 9%-15wt%, and more preferably 10-13wt%; the water content is 2-20wt%, preferably 4-15wt%, and more preferably 10-13wt%. Too high a THNM concentration will increase the amount of THNM decomposition during the hydrogenation process, resulting in a reduced Tris yield; and sufficient water content is to ensure that Tris will not precipitate during the hydrogenation process and cause pipeline blockage, while too high a water content will increase the energy consumption of the separation process.

[0015] In some embodiments, in step (2), the nickel-based catalyst includes but is not limited to supported or co-precipitated catalysts such as Raney nickel, nickel aluminum, nickel silicon, and nickel iron. In some embodiments, the particle size of the nickel-based catalyst is 1.5 to 8 mm, preferably 3 to 6 mm. In some embodiments, the nickel-based catalyst is activated with hydrogen before use, and the step of hydrogen activation includes: the nickel-based catalyst is activated with hydrogen at 100 to 400° C. for 3 to 12 hours and then cooled to room temperature.

[0016] In some embodiments, in step (2), the molar ratio of hydrogen to THNM is 180 to 350:1. In a specific embodiment, the flow rate of the hydrogenation feed liquid introduced into the trickle bed reactor loaded with a nickel-based catalyst is 110 to 130 kg / h, and the flow rate of hydrogen is 390 to 540 Nm 3 / h.

[0017] In some embodiments, in step (2), the reaction pressure is preferably 3-7 MPa.

[0018] In some embodiments, in step (2), the hydrogenation feed liquid is introduced into the trickle bed reactor at room temperature, and the hydrogen needs to be heat exchanged through a preheater. The hydrogenation feed liquid passes through a liquid distributor in the trickle bed reactor and is fully mixed with the preheated hydrogen until the temperature reaches 20 to 45°C, preferably 30 to 40°C.

[0019] In some embodiments, in step (2), the hot spot temperature of the catalyst bed is 45 to 85°C, preferably 60 to 75°C.

[0020] In some embodiments, in step (3), the reaction material is cooled to 45-50° C. after exiting the trickle bed reactor.

[0021] In some embodiments, in the method for preparing tris(hydroxymethyl)aminomethane by a trickle bed process of the present invention, the conversion rate of tris(hydroxymethyl)nitromethane can reach 100%, and the reaction yield of Tris is 90-94%.

[0022] Beneficial Effects

[0023] The invention provides a method for preparing tris(hydroxymethyl)aminomethane by a trickle bed process. The method can ensure the continuous operation of a hydrogenation process without blockage, has low cost, simple operation and high automation.

[0024] The invention adopts a trickle bed process, adopts a higher hydrogen-alcohol ratio to extract heat, and adopts a higher pressure to control the gas phase flow rate in the reactor, thereby ensuring the heat extraction efficiency and a good Tris yield, so that the trishydroxymethylnitromethane conversion rate can reach 100%, and a high Tris yield of 90-94% can be obtained. The product has high purity and good industrial practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the liquid chromatogram of the THNM hydrogenation reaction liquid in Example 1. DETAILED DESCRIPTION

[0026] Hereinafter, the present invention will be described in more detail. Here, it should be noted by those skilled in the art that the terms or words used in the specification and claims of the present invention should not be interpreted restrictively as conventional or dictionary meanings, but should be interpreted as the meaning and concept of the present invention consistent with the scope of the present invention on the basis that the inventor of the present invention can appropriately define the terms in order to describe the present invention in the best manner.

[0027] Therefore, the contents described below are only preferred embodiments of the present invention and do not represent all technical concepts of the present invention. Therefore, it can be understood that all equivalent methods and variations that can replace them are included within the scope of the claims of the present invention.

[0028] The present invention will be explained in more detail below by way of examples.

[0029] In the following text, unless otherwise specified, all raw materials are commercially available industrial grade products.

[0030] Trickle bed reactor (Hebei Xuyang Energy Co., Ltd.): Single-channel plug flow adiabatic reactor, the reactor diameter is 450mm, gas and liquid phases are both inlet and outlet. The catalyst in the trickle bed is Raney nickel catalyst, with a particle size of 3-8mm and a loading volume of 0.2m 3 Before use, the catalyst was activated with hydrogen at 150°C for 12 hours and then cooled to room temperature.

[0031] The reaction product Tris was analyzed by high performance liquid chromatography (Agilent 1260 high performance liquid chromatograph), the chromatographic column was Yuexu Technology Ultimate XB-SCX 4.6*250 5.0, the detector was a differential detector, the column temperature was 35°C, the mobile phase was 50 mM potassium dihydrogen phosphate aqueous solution, and the flow rate was 1 mL / min. The external standard quantitative method was used.

[0032] Example 1

[0033] (1) Add 1600 kg methanol and 200 kg water to 3 m 3 Into the stirring kettle, add 200 kg of raw material trimethylolnitromethane (THNM), and stir evenly at room temperature (25° C.) to completely dissolve THNM to prepare a hydrogenation raw material liquid with a concentration of 10 wt%.

[0034] (2) After being preheated by a preheater, the hydrogen gas and the hydrogenation feed liquid are respectively introduced into a trickle bed reactor loaded with a nickel-based catalyst. The flow rate of the hydrogenation feed liquid is 110 kg / h, and the flow rate of the circulating hydrogen gas is 434 Nm 3 / h (at this time, the molar ratio of hydrogen to trihydroxymethylnitromethane (THNM) is 266:1). The hydrogenation feed liquid is fully mixed with the preheated hydrogen through a liquid distributor in a trickle bed reactor (mixing temperature is 30°C), and catalytic hydrogenation reaction occurs through the catalyst bed. The hot spot temperature of the bed is 63°C and the pressure of the reaction system is 4.5MPa.

[0035] (3) After the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. in a heat exchanger and then separated in a high-pressure gas-liquid separator to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane. Samples are taken for HPLC analysis, and the Tris yield is 93.2%.

[0036] Figure 1 The liquid chromatogram of the THNM hydrogenation reaction liquid of this embodiment is shown. Among them, the peak with a retention time of 4.236min is the solvent methanol, the peak with a retention time of 19.341min is Tris, the peak with a retention time of 21.516min is thiaminol, and the peak with a retention time of 24.358min is ethanolamine. The calculated concentration of Tris is 7.47%, the concentration of thiaminol is 0.39%, and the concentration of ethanolamine is 0.14%.

[0037] Example 2

[0038] (1) Add 1560 kg methanol and 200 kg water to 3 m 3 240 kg of trimethylolnitromethane (THNM) was added into the stirring kettle and stirred evenly at room temperature (25° C.) to completely dissolve THNM to prepare a hydrogenation raw material liquid with a concentration of 12 wt%.

[0039] (2) After being preheated by a preheater, the hydrogen gas and the hydrogenation feed liquid are respectively introduced into a trickle bed reactor loaded with a nickel-based catalyst. The flow rate of the hydrogenation reaction liquid is 110 kg / h, and the flow rate of the circulating hydrogen gas is 471 Nm 3 / h (at this time, the molar ratio of hydrogen to trihydroxymethylnitromethane (THNM) is 289:1). The hydrogenation feed liquid is fully mixed with the preheated hydrogen through a liquid distributor in a trickle bed reactor (mixing temperature is 34°C), and catalytic hydrogenation reaction occurs through the catalyst bed. The hot spot temperature of the bed is 69°C and the pressure of the reaction system is 5.5MPa.

[0040] (3) After the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. in a heat exchanger and then separated in a high-pressure gas-liquid separator to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane. Samples are taken for HPLC analysis, and the Tris yield is 92.1%.

[0041] Example 3

[0042] (1) Add 1540 kg methanol and 200 kg water to 3 m 3 Into the stirring kettle, add 260 kg of raw material trimethylolnitromethane (THNM), and stir evenly at room temperature (25° C.) to completely dissolve THNM to prepare a hydrogenation raw material liquid with a concentration of 13 wt%.

[0043] (2) After being preheated by a preheater, the hydrogen gas and the hydrogenation feed liquid are respectively introduced into a trickle bed reactor loaded with a nickel-based catalyst. The flow rate of the hydrogenation reaction liquid is 110 kg / h, and the flow rate of the circulating hydrogen gas is 538 Nm 3 / h (at this time, the molar ratio of hydrogen to trihydroxymethylnitromethane (THNM) is 330:1). The hydrogenation feed liquid is fully mixed with the preheated hydrogen through a liquid distributor in a trickle bed reactor (mixing temperature is 40°C), and catalytic hydrogenation reaction occurs through the catalyst bed. The hot spot temperature of the bed is 72°C and the pressure of the reaction system is 5MPa.

[0044] (3) After the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. in a heat exchanger and then separated in a high-pressure gas-liquid separator to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane. Samples are taken for HPLC analysis, and the Tris yield is 90.1%.

[0045] Embodiments 4 to 7

[0046] According to a method similar to Example 1, with 2000 kg of hydrogenation feed liquid as the basis, the composition of the hydrogenation feed liquid, feed amount, reaction pressure, temperature and other conditions were changed according to Table 1, and the Tris yield results were as follows.

[0047] Table 1.

[0048]

[0049] Comparative Example 1

[0050] (1) Add 1600 kg methanol and 200 kg water to 3 m 3 Into the stirring kettle, add 200 kg of raw material trimethylolnitromethane (THNM), and stir evenly at room temperature (25° C.) to completely dissolve THNM to prepare a hydrogenation raw material liquid with a concentration of 10 wt%.

[0051] (2) After being preheated by a preheater, the hydrogen gas and the hydrogenation feed liquid are respectively introduced into a trickle bed reactor loaded with a nickel-based catalyst. The flow rate of the hydrogenation reaction liquid is 110 kg / h, and the flow rate of the circulating hydrogen gas is 110 Nm 3 / h (at this time, the molar ratio of hydrogen to trihydroxymethylnitromethane (THNM) is 67:1). The hydrogenation feed liquid is fully mixed with the preheated hydrogen through a liquid distributor in a trickle bed reactor (mixing temperature is 30°C), and catalytic hydrogenation reaction occurs through the catalyst bed. The hot spot temperature of the bed is 90.3°C and the pressure of the reaction system is 4.5MPa.

[0052] (3) After the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. in a heat exchanger and then separated in a high-pressure gas-liquid separator to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane. Samples are taken for HPLC analysis, and the Tris yield is 82.1%.

[0053] Comparative Example 2

[0054] (1) Add 1600 kg methanol and 200 kg water to 3 m 3 Into the stirring kettle, add 200 kg of raw material trimethylolnitromethane (THNM), and stir evenly at room temperature (25° C.) to completely dissolve THNM to prepare a hydrogenation raw material liquid with a concentration of 10 wt%.

[0055] (2) After being preheated by a preheater, the hydrogen gas and the hydrogenation feed liquid are respectively introduced into a trickle bed reactor loaded with a nickel-based catalyst. The flow rate of the hydrogenation reaction liquid is 110 kg / h, and the flow rate of the circulating hydrogen gas is 110 Nm 3 / h (at this time, the molar ratio of hydrogen to trihydroxymethylnitromethane (THNM) is 67:1). The hydrogenation feed liquid is fully mixed with the preheated hydrogen through a liquid distributor in a trickle bed reactor (mixing temperature is 30°C), and catalytic hydrogenation reaction occurs through the catalyst bed. The hot spot temperature of the bed is 88.1°C and the pressure of the reaction system is 3MPa.

[0056] (3) After the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. in a heat exchanger and then separated in a high-pressure gas-liquid separator to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane. Samples are taken for HPLC analysis, and the Tris yield is 80.4%.

Claims

1. A method for preparing tris(hydroxymethyl)aminomethane by a trickle bed process, the method comprising the following steps: (1) dissolving trimethylolnitromethane in a mixed solvent of methanol and water to prepare a hydrogenation raw material liquid; (2) respectively introducing hydrogen and the hydrogenation feed liquid into a trickle bed reactor loaded with a nickel-based catalyst, wherein the hydrogenation feed liquid is fully mixed with hydrogen through a liquid distributor in the trickle bed reactor and undergoes a catalytic hydrogenation reaction through a catalyst bed; wherein the molar ratio of hydrogen to trimethylolnitromethane is 80 to 400:1, and the reaction pressure is 3 to 15 MPa; (3) The reaction materials are cooled after exiting the trickle bed reactor, and then subjected to gas-liquid separation to obtain a hydrogenation reaction liquid containing tris(hydroxymethyl)aminomethane.

2. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: The trickle bed reactor is a single-channel plug flow adiabatic reactor, and both the gas phase and the liquid phase enter from the top and exit from the bottom.

3. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (1): In the hydrogenation raw liquid, the concentration of trimethylolnitromethane is 8-18wt%, preferably 9%-15wt%, more preferably 10-13wt%; the water content is 2-20wt%, preferably 4-15wt%, more preferably 10-13wt%.

4. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2): The nickel-based catalyst is a Raney nickel, nickel-aluminum, nickel-silicon, nickel-iron supported or co-precipitated catalyst; Preferably, the particle size of the nickel-based catalyst is 1.5 to 8 mm, preferably 3 to 6 mm; Preferably, the nickel-based catalyst is hydrogen activated before use, and the hydrogen activation step comprises: the nickel-based catalyst is hydrogen activated at 100-400° C. for 3-12 hours and then cooled to room temperature.

5. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2): The molar ratio of hydrogen to tris(hydroxymethyl)nitromethane is 180-350:

1.

6. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2), the flow rate of the hydrogenation feed liquid into the trickle bed reactor loaded with nickel catalyst is 110-130 kg / h, and the flow rate of hydrogen is 390-540 Nm 3 / h.

7. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2): the reaction pressure is preferably 3-7 MPa.

8. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2): The hydrogenation feed liquid is introduced into the trickle bed reactor at room temperature, passes through a liquid distributor in the trickle bed reactor and is fully mixed with the preheated hydrogen to a temperature of 20 to 45° C., preferably 30 to 40° C.

9. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (2): the hot spot temperature of the catalyst bed is 45 to 85°C, preferably 60 to 75°C.

10. The method for preparing tris(hydroxymethyl)aminomethane by trickle bed process according to claim 1, characterized in that: In step (3): after the reaction materials come out of the trickle bed reactor, they are cooled to 45-50° C. through a heat exchanger.

Images