A preparation method of trishydroxymethylaminomethane

Abstract

The present invention relates to a method for preparing tris(hydroxymethyl)aminomethane and a use of a fixed bed reactor for realizing the method for preparing tris(hydroxymethyl)aminomethane. The method for preparing tris(hydroxymethyl)aminomethane of the present invention comprises: a process for preparing tris(hydroxymethyl)aminomethane by continuous catalytic hydrogenation of tris(hydroxymethyl)nitromethane is carried out in a fixed bed reactor, and a catalyst is loaded in the fixed bed reactor. The method for preparing tris(hydroxymethyl)aminomethane of the present invention has a high degree of automation, can be produced online, has controllable safety risks, can greatly eliminate safety hazards, can realize continuous feeding and discharging, reduce the amount of solvent used, and have uniform products, which can greatly shorten the reaction time, improve the reaction selectivity, and improve the product yield and quality.

Description

Technical Field

[0001] The invention belongs to the field of fine chemical synthesis, and specifically relates to a method for preparing trishydroxymethylaminomethane. Background Art

[0002] Tris(hydroxymethyl)aminomethane can be used as a biological buffer for preparing buffer for gel electrophoresis. As an alkaline drug, it is used to correct acidosis without causing increased carbon dioxide retention. It is widely used in metabolic acidosis and respiratory acidosis. It has a good buffering effect on metabolic acidosis and enzyme activity reactions. It is also a good pharmaceutical intermediate.

[0003] Tris(hydroxymethyl)aminomethane is synthesized industrially, and the polymerization-hydrogenation two-step method is often used to synthesize tris(hydroxymethyl)aminomethane. For example, CN1800142A records the synthesis method of tris(hydroxymethyl)aminomethane. Its hydrogenation reaction is completed by intermittent operation of a high-pressure hydrogenation kettle. Due to the high pressure of the hydrogenation reduction reaction, multiple gas replacements are required before and after the reaction. The operation is cumbersome, the operation process is dangerous, the requirements for the reaction equipment are also relatively high, and the reaction time is long. CN104725244A discloses a method for preparing tris(hydroxymethyl)aminomethane using tris(hydroxymethyl)aminomethane and charcoal activated carbon. Due to the need to repeatedly add charcoal activated carbon, it is difficult to achieve continuous production, and the post-processing process is complicated and not suitable for industrial production. There is an urgent need for a preparation method with simple process and continuous production, short reaction time and low probability of side reactions. Summary of the invention

[0004] Problem that the invention aims to solve

[0005] The invention provides a preparation method of trishydroxymethylaminomethane. The preparation method has high yield, high purity of the obtained product, simple process and high safety, can be produced continuously, has short reaction time and can effectively improve the production capacity of the product.

[0006] Technical solutions to the problem

[0007] The present invention provides a method for preparing trishydroxymethylaminomethane, comprising:

[0008] A method for preparing tris(hydroxymethyl)aminomethane is characterized by comprising the following steps: loading a catalyst into a fixed bed reactor, replacing the air in the fixed bed reactor, then introducing a reaction mass of tris(hydroxymethyl)nitromethane and a solvent uniformly mixed into the fixed bed reactor, performing continuous catalytic hydrogenation reaction to obtain a crude product, and obtaining tris(hydroxymethyl)aminomethane after refining.

[0009] The catalytic hydrogenation reaction in the synthesis process of tris(hydroxymethyl)aminomethane has always been carried out using a traditional high-pressure reactor. The inventor of this patent uses a fixed bed reactor to carry out the hydrogenation reaction in the synthesis process of tris(hydroxymethyl)aminomethane. By using a fixed bed reactor for the hydrogenation reaction, the reaction can be carried out continuously, the material can be continuously fed and discharged, the amount of solvent can be reduced, the reaction time can be greatly shortened, the reaction selectivity can be improved, and the product yield and quality can be improved.

[0010] According to the preparation method of the present invention, after the continuous hydrogenation reaction is carried out in the fixed bed, the product is collected at the discharge port, the solvent can be recycled for the synthesis of tris(hydroxymethyl)aminomethane after recovery, and the obtained crude product is recrystallized with water to obtain tris(hydroxymethyl)aminomethane.

[0011] According to the preparation method of the present invention, the temperature of the hydrogenation reaction is 30-90°C.

[0012] According to the preparation method of the present invention, the pressure of the hydrogenation reaction is 1.5-3 MPa.

[0013] According to the preparation method of the present invention, the carrier loaded with active metal catalyst is selected from any one of silica, activated alumina, diatomaceous earth and activated carbon, and the loading amount of active metal is 5wt%-30wt% based on the total mass of the catalyst.

[0014] According to the preparation method of the present invention,

[0015] The reaction material of trimethylolnitromethane and solvent is first preheated through a preheating pipeline, and then introduced into the emptied fixed bed reactor, wherein the preheating temperature is 40-60° C. The reaction material enters the fixed bed reactor after being preheated, which can reduce the temperature difference in the fixed bed reactor and reduce the impact damage to the catalyst, thereby facilitating the extension of its service life.

[0016] According to the preparation method of the present invention,

[0017] The solvent is selected from any one of methanol, ethanol, isopropanol or water.

[0018] According to the preparation method of the present invention,

[0019] The gas-liquid ratio input into the fixed bed is 50-500: 1. The gas-liquid ratio is not suitable to be too high or too low. If the gas-liquid ratio is too low, the hydrogen content is low, the flow rate is too slow, and the reaction efficiency is low; if the gas-liquid ratio is too large, the reaction residence time is short and the reaction cannot be fully reacted.

[0020] According to the preparation method of the present invention, the air in the fixed bed reactor is replaced by an inert gas, and the inert gas may be nitrogen, helium, etc., which can achieve the purpose of exhausting air in the present invention. Alternatively, the air in the fixed bed reactor is replaced by introducing the solvent.

[0021] According to the preparation method of the present invention,

[0022] The fixed bed reactor is a fixed bed reactor, or a plurality of fixed bed reactors are connected in series to form a multi-stage fixed bed reactor. For example, the fixed bed reactor is a single-stage tubular fixed bed reactor, or a plurality of tubular fixed bed reactors are connected in series to form a multi-stage tubular fixed bed reactor. Based on the production capacity of the tris(hydroxymethyl)nitromethane dehydrogenation device and the size of the reactor equipment, the number of stages of the fixed bed reactor of the present invention can be set as required.

[0023] According to the preparation method of the present invention,

[0024] The catalyst is a metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium; or the catalyst is a supported metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium.

[0025] According to the preparation method of the present invention,

[0026] The source of the trimethylolnitromethane includes but is not limited to being prepared from nitromethane and paraformaldehyde or nitromethane and formaldehyde.

[0027] According to the preparation method of the present invention,

[0028] The hydrogen for the continuous catalytic hydrogenation reaction is delivered to the fixed bed reactor in excess, or the hydrogen required for hydrogenation is delivered to the reactor in excess, or the amount of hydrogen delivered to the fixed bed reactor is sufficient to compensate for the hydrogen consumed by the reaction and the hydrogen dissolved in the product stream and carried away from the reactor.

[0029] The present invention also provides a use of a fixed bed reactor for realizing the method for preparing trishydroxymethylaminomethane of the present invention.

[0030] The present invention uses a fixed bed reactor to realize the hydrogenation reaction in the synthesis of tris(hydroxymethyl)aminomethane, and the equipment used has the characteristics of small footprint, low catalyst loss, low investment cost, high reaction conversion rate, etc. The present invention uses a fixed bed for continuous hydrogenation reaction, which can realize continuous feeding and discharging of materials, greatly shorten the reaction time, have a high degree of automation, reduce the amount of solvent, improve the reaction selectivity, improve the product yield and product purity, can be produced online, and the safety risk can be controlled, which greatly improves the logistics process and cost, eliminates safety hazards, and reduces the occurrence of safety accidents and quality accidents.

[0031] Beneficial Effects

[0032] 1. The most important thing about the patent of the present invention is that it uses a fixed bed reactor for continuous catalytic hydrogenation, which solves the safety problems caused by the hydrogenation reaction in reactors for a long time. Traditional reactor hydrogenation has large heat release and high pressure, and requires a large amount of material to be fed at one time. It is extremely dangerous when hydrogen is replaced, and the reaction safety is difficult to control. This is an important safety hazard that needs to be urgently solved in chemical companies. In the case of continuous catalytic hydrogenation in a fixed bed reactor, gas replacement only occurs during start-up and shutdown. There is no hydrogen replacement or catalyst replacement process during continuous feeding and discharging, and the amount of combustible and explosive substances per unit area in the fixed bed reactor is very small, which fundamentally solves the safety hazard with the greatest risk of combustion and explosion caused by multiple gas replacements in reactor catalyst hydrogenation, greatly reducing the occurrence of safety accidents.

[0033] 2. The patent of the present invention adopts a fixed bed reactor for continuous hydrogenation to realize fully automated online production, which does not require production workers to participate in high-risk operations and provides safety protection for employees.

[0034] 3. The patent of the present invention adopts a fixed bed reactor for continuous hydrogenation, which can greatly shorten the reaction time. The method of the present invention can complete the reaction in a fixed bed reactor in 20 minutes. The logistics in the fixed bed reactor is a plug flow, flowing forward like a piston. The material reacts with the hydrogen as it pushes forward. The generated products are not back-mixed, and the products are uniform, which can effectively improve product quality, greatly improve production efficiency, and reduce production costs. It takes several hours for the reactor to complete the reaction, and the products after the reaction have to stay in the reactor, which is prone to back-mixing to produce by-products or product destruction.

[0035] 4. The existing traditional reactor hydrogenation process adopts rapid mechanical stirring, which can easily break the catalyst and dissolve heavy metals. After the reaction, the catalyst needs to be filtered out, the reaction time is long, and the purification post-processing is cumbersome. Both the quality and cost are far inferior to the fixed bed reactor used in the present invention. The patent of the present invention adopts a fixed bed reactor for continuous hydrogenation. The catalyst is pre-installed in the fixed bed reactor. No stirring is required during the reaction process, and there will be no heavy metal residues in the product, which can effectively improve the product quality and increase the product yield.

[0036] 5. It is difficult to change the reaction conditions in the reaction process of the existing traditional reactor. The heat released by the reaction cannot be exchanged, which easily leads to local overheating, resulting in a narrow range of optimal reaction conditions for the existing reaction and the temperature is not easy to be too high. The fixed bed reactor hydrogenation reaction adopted by the patent of the present invention can be realized in a wider span range, and the reaction temperature can be higher than that of the traditional reactor. The reaction can be completed faster under high temperature conditions, and the reaction efficiency is improved. The heat release of the present invention is controllable, and the three-phase heterogeneous hydrogenation reaction of gas, liquid and solid in the fixed bed reactor is realized.

[0037] 6. In the existing conventional reactor for catalytic hydrogenation, the hydrogen after the reaction can only be burned or emptied and cannot be recovered. The fixed bed catalytic hydrogenation adopted by the present invention has stable hydrogen inflow and outflow, has recovery value, is beneficial to environmental protection and cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0039] Figure 1 It is a schematic diagram of the preparation method of the present invention. DETAILED DESCRIPTION

[0040] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0041] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0042] Unless otherwise stated, the units used in the present invention are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0043] The present invention provides a method for preparing trishydroxymethylaminomethane, wherein:

[0044] The fixed bed reactor has a constant temperature section in the middle, the catalyst is loaded in the constant temperature section in the middle of the reactor, quartz sand is loaded in the upper and lower sections of the catalyst, nitrogen is introduced to replace the air in the fixed bed reactor, and then hydrogen is introduced to discharge the nitrogen in the fixed bed reactor. First, trimethylolnitromethane and solvent are mixed, and the resulting reaction mass is preheated through a preheating pipe with a preheating temperature of 40-60°C, and then enters from the top of the fixed bed. Hydrogen, reaction mass and catalyst are fully mixed inside the fixed bed for continuous catalytic hydrogenation reaction, separated by an oil and gas separator, discharged from the bottom discharge port, cooled and crystallized, and the solvent can be distilled and recovered. The obtained crude product is recrystallized from water to obtain trimethylolaminomethane;

[0045] The catalyst is a metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium; or the catalyst is a supported metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium, and the carrier is selected from any one of silicon dioxide, activated alumina, diatomaceous earth, activated carbon, and the loading amount of the active metal is 5wt%-30wt% based on the total mass of the catalyst.

[0046] According to an embodiment of the present invention, the temperature of the hydrogenation reaction is 30-90°C and the pressure is 1.5-3Mpa; if the temperature or pressure is too low, the reaction cannot occur or the time to complete the reaction is too long, which is not suitable for production.

[0047] According to an embodiment of the present invention, the gas-liquid ratio input into the fixed bed is 50-500: 1. The aspect ratio of the fixed bed reactor can be selected in a suitable range according to production needs. Although a fixed bed reactor that is too long has a better reaction effect, the pressure drop will increase accordingly.

[0048] According to an embodiment of the present invention, the volume proportion of the catalyst loading is 20-80% relative to the total volume of the fixed bed reactor.

[0049] According to an embodiment of the present invention, the air in the fixed bed reactor is replaced by an inert gas, and the inert gas may be nitrogen, helium, or the like, which can achieve the purpose of evacuation of the present invention. Alternatively, the air in the fixed bed reactor is replaced by introducing a solvent, and the solvent is selected from any one of methanol, ethanol, isopropanol, or water.

[0050] According to an embodiment of the present invention, the fixed bed reactor is a fixed bed reactor, or a plurality of fixed bed reactors are connected in series to form a multi-stage fixed bed reactor. Specifically, the fixed bed reactor is a single-stage tubular fixed bed reactor, or a plurality of tubular fixed bed reactors are connected in series to form a multi-stage tubular fixed bed reactor, and each stage of the tubular fixed bed reactor can be equipped with a plurality of tubular reaction units.

[0051] In the traditional preparation process of tris(hydroxymethyl)aminomethane, a reactor is used for intermittent production, and each production requires hydrogen replacement and catalyst separation, which results in extremely high production safety risks. In contrast, in the preparation method of the present invention, a fixed bed reactor is used as a reaction vessel, and continuous production can be carried out after only one hydrogen filling, without repeated hydrogen replacement, thereby reducing production risks, and not requiring frequent separation of catalysts and materials, thereby greatly improving production efficiency, stabilizing product quality, and being more suitable for large-scale industrial production.

[0052] By adopting a fixed bed reactor to carry out the preparation method of the present invention, back-mixing of the reaction raw materials during the reaction process can be effectively prevented, the reaction efficiency can be improved, and the reaction yield and product purity can be increased.

[0053] The tris(hydroxymethyl)nitromethane used in the present invention is not particularly limited, and can be a commercially available product or prepared by a known preparation method, for example, by reacting nitromethane, paraformaldehyde and methanol under a catalyst for 3 to 6 hours to obtain the tris(hydroxymethyl)nitromethane, and the reaction temperature is 40-55°C.

[0054] The present invention also provides a fixed bed reactor for realizing the method for preparing trishydroxymethylaminomethane of the present invention, which can realize continuous feeding and discharging of materials, has a high degree of automation, and has controllable safety risks, so that the production efficiency is greatly improved and the product quality is stable.

[0055] Example

[0056] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0057] Examples 1-9 and Comparative Examples 1-3

[0058] The catalyst nickel is respectively loaded in the middle of two-stage serially connected tubular fixed bed reactors, and both ends are sealed with quartz sand. The volume of the catalyst in the first reactor accounts for 20%, and the volume of the catalyst in the second reactor accounts for 50%. Tris(hydroxymethyl)nitromethane is dissolved in anhydrous methanol to prepare a reaction material with a mass concentration of 10%.

[0059] Nitrogen is introduced to replace the air in the fixed bed reactor, and then hydrogen is introduced to discharge the nitrogen in the fixed bed reactor. The reaction materials configured above are preheated to 60°C, and introduced into the fixed bed reactor that discharges nitrogen at a flow rate of 20 ml / min. The reaction temperature is controlled to be 50°C and the reaction pressure is 2 MPa. Continuous catalytic hydrogenation reaction is carried out, and the flow rate of hydrogen is controlled so that the material stays in the fixed bed reactor for at least 20 minutes. The product is continuously sampled at the discharge port for 0.5 hours to collect the product, cooled, crystallized and filtered, and the obtained crude product is recrystallized once with water to obtain the finished product of trishydroxymethylaminomethane. The methanol obtained by distillation of the filtered mother liquor can be recycled.

[0060] The effects of different reaction temperatures, reaction pressures, hydrogen flow rates, and gas-liquid ratios on the reaction are shown in the following table.

[0061]

[0062] (Note: The gas-liquid ratio is the flow rate of hydrogen: the flow rate of the reaction materials)

[0063] Example 10

[0064] Palladium and quartz sand were mixed in a volume ratio of 3:2 and then respectively loaded in the middle of a two-stage series tubular fixed bed reactor, and both ends were sealed with quartz sand. The volume proportion of the catalyst in the two-stage reactor was 70%. Tris(hydroxymethyl)nitromethane was dissolved in anhydrous ethanol to prepare a reaction material with a mass concentration of 10%.

[0065] First, anhydrous ethanol is introduced to empty the reactor, and then hydrogen is introduced. The reaction material configured above is preheated to 60° C., and introduced into a fixed bed reactor at a flow rate of 20 ml / min. The reaction temperature is controlled to be 80° C., and the reaction pressure is 2 MPa. A continuous catalytic hydrogenation reaction is performed, and the flow rate of hydrogen is 1000 ml / min. The material is allowed to stay in the fixed bed reactor for at least 20 minutes. The product is continuously sampled at the discharge port for 0.5 hours to collect the product, and the product is cooled, crystallized, and filtered. The crude product is recrystallized once with water to obtain tris(hydroxymethyl)aminomethane. The product purity is 99.92%, and the yield of tris(hydroxymethyl)aminomethane is 85.13%. The ethanol obtained by distilling the filtered mother liquor can be recycled.

[0066] Embodiment 11

[0067] Platinum-carbon (platinum content 5%) catalyst is loaded in the middle of a first-stage tubular fixed bed reactor, and both ends are sealed with quartz sand, with the catalyst volume accounting for 80%. Tris(hydroxymethyl)nitromethane is dissolved in water to prepare a reaction material with a mass concentration of 20%.

[0068] Nitrogen is introduced to replace the air in the fixed bed reactor, and then hydrogen is introduced to discharge the nitrogen in the fixed bed reactor. The reaction materials configured above are preheated to 40°C, introduced into the fixed bed reactor from which nitrogen is discharged at a flow rate of 20 ml / min, the reaction temperature is controlled to be 90°C, the reaction pressure is 2 MPa, and a continuous catalytic hydrogenation reaction is carried out, the flow rate of hydrogen is 1000 ml / min, the material is allowed to stay in the fixed bed reactor for at least 20 min, and the product is collected by continuous sampling at the discharge port for 0.5 h, cooled, crystallized and filtered, and the crude product is recrystallized once with water to obtain the finished product of tris(hydroxymethyl)aminomethane, the product purity is 99.91%, and the yield of tris(hydroxymethyl)aminomethane is 85.11%.

[0069] Example 12

[0070] A metal nickel supported catalyst (supported by activated alumina with a loading of 30 wt%) was loaded into a fixed bed reactor, and both ends were sealed with quartz sand, with the catalyst volume accounting for 20%. Tris(hydroxymethyl)nitromethane was dissolved in anhydrous methanol to prepare a reaction mass with a mass concentration of 30%.

[0071] Nitrogen is introduced to replace the air in the fixed bed reactor, and then hydrogen is introduced to discharge the nitrogen in the fixed bed reactor. Anhydrous methanol is first introduced into the fixed bed reactor discharging nitrogen at a flow rate of 20 ml / min for adjustment for 5 minutes, and then the reaction material configured above is introduced to preheat to 60°C, and introduced into the fixed bed reactor discharging nitrogen at a flow rate of 20 ml / min, and the reaction temperature is controlled to be 80°C, and the reaction pressure is 1.5 MPa, and a continuous catalytic hydrogenation reaction is carried out. The flow rate of hydrogen is 1000 ml / min, and the material is allowed to stay in the fixed bed reactor for at least 20 minutes. The product is continuously sampled at the discharge port for 0.5 hours to collect the product, cooled, crystallized, and filtered. The obtained crude product is recrystallized once with water to obtain the finished product of tris(hydroxymethyl)aminomethane, and the product purity is 99.92%, and the yield of tris(hydroxymethyl)aminomethane is 84.12%.

[0072] Example 13

[0073] A metal palladium supported catalyst (supported by activated carbon, with a loading of 30 wt%) was loaded into a fixed bed reactor, and both ends were sealed with quartz sand, with the catalyst volume accounting for 40%. Tris(hydroxymethyl)nitromethane was dissolved in anhydrous methanol to prepare a reaction mass with a mass concentration of 20%.

[0074] Nitrogen is introduced to replace the air in the fixed bed reactor, and then hydrogen is introduced to discharge the nitrogen in the fixed bed reactor. The reaction materials configured above are preheated to 70°C, introduced into the fixed bed reactor from which nitrogen is discharged at a flow rate of 20 ml / min, the reaction temperature is controlled to be 80°C, the reaction pressure is 3 MPa, and a continuous catalytic hydrogenation reaction is carried out, the flow rate of hydrogen is 1000 ml / min, the material is allowed to stay in the fixed bed reactor for at least 20 min, and the product is collected by continuous sampling at the discharge port for 0.5 h, cooled, crystallized and filtered, and the crude product is recrystallized once with water to obtain the finished product of tris(hydroxymethyl)aminomethane, the product purity is 99.93%, and the yield of tris(hydroxymethyl)aminomethane is 84.54%.

[0075] Embodiment 14

[0076] Weigh 190g of paraformaldehyde, 150g of methanol and 0.4g of potassium hydroxide in a reactor, stir and heat until completely dissolved, slowly drop 110g of nitromethane, keep the temperature at 45°C, the reaction is completed, and 45°C is maintained for 4 hours. Add 650g of methanol to the condensed material after the reaction and mix evenly, and transport it to a fixed bed reactor at a flow rate of 20ml / min for continuous catalytic hydrogenation. Among them, the reaction temperature is 50°C, the reaction pressure is 2MPa, the flow rate of hydrogen is 1000ml / min, and nickel is filled in the fixed bed reactor so that the material stays in the fixed bed reactor for at least 20min. The product is collected by continuous sampling at the discharge port for 0.5h, cooled, crystallized and filtered, and the crude product is recrystallized once with water to obtain the finished product of trishydroxymethylaminomethane, with a product purity of 99.89% and a yield of 82.07%.

[0077] Comparative Example 4

[0078] Take 7.20g of trimethylolnitromethane, 60.0mL of anhydrous methanol, and 0.7g of platinum-carbon catalyst (platinum content 5%) in an autoclave, ventilate five times, control the hydrogen pressure at 2Mpa, pass hydrogen at 50°C for 3h, continue the reaction for 1h after the hydrogen passing is completed, stop heating, cool down, transfer the cooled reaction solution to a single-necked bottle, put it in the refrigerator for cooling and crystallization, and then filter it. Repeat the cooling and crystallization 3 times. The purity is 99.69% and the yield is 72.01%.

[0079] Comparative Example 5

[0080] Weigh 190g of paraformaldehyde, 150g of methanol and 0.4g of potassium hydroxide into a reactor, stir and heat until completely dissolved, slowly drop 110g of nitromethane, keep the temperature at 45°C, and finish the reaction. Maintain 45°C for 4 hours. Add 650g of methanol and 15.4g of nickel catalyst to the condensed material after the reaction, mix evenly, and inject into a hydrogenation autoclave, control the reaction temperature to 55°C, the reaction pressure to 2MPa, pass hydrogen for 3h, continue the reaction for 1h after the hydrogenation is finished, cool down, crystallize and filter, add water to the obtained crude product and recrystallize it 3 times to obtain the finished product of trishydroxymethylaminomethane, the product purity is 99.62%, and the total yield of condensation and reduction is 72.35%.

[0081] Heavy Metal Test

[0082] The tris(hydroxymethyl)aminomethane products produced in Example 1, Comparative Example 4 and Comparative Example 5 were measured according to the national standard GB / T 9735-2008 General method for determination of heavy metals in chemical reagents. The results are shown in the following table.

[0083] Heavy metals (as Pb), w / % Example 1 ≤0.0005 Comparative Example 4 ≤0.001 Comparative Example 5 ≤0.001

[0084] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

[0085] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing trishydroxymethylaminomethane, characterized in that: The method comprises the following steps: loading a catalyst into a fixed bed reactor, replacing the air in the fixed bed reactor, and then introducing a reaction material in which trimethylolnitromethane and a solvent are evenly mixed into the fixed bed reactor, performing a continuous catalytic hydrogenation reaction to obtain a crude product, and obtaining trimethylolaminomethane after refining, wherein the gas-liquid ratio input into the fixed bed is 50-500:1, the temperature of the hydrogenation reaction is 30-90°C, and the pressure of the hydrogenation reaction is 1.5-3MPa.

2. The preparation method according to claim 1, characterized in that: The carrier for supporting the active metal catalyst is selected from any one of silicon dioxide, activated alumina, diatomaceous earth and activated carbon. Based on the total mass of the catalyst, the loading amount of the active metal is 5wt%-30wt%.

3. The preparation method according to claim 1, characterized in that: The reaction material of trimethylolnitromethane and solvent is first preheated through a preheating pipeline and then introduced into the emptied fixed bed reactor, wherein the preheating temperature is 40-60°C.

4. The preparation method according to claim 1, characterized in that: The solvent is selected from any one of methanol, ethanol, isopropanol or water.

5. The preparation method according to claim 1, characterized in that: The air in the fixed bed reactor is replaced by an inert gas or the air in the fixed bed reactor is replaced by introducing the solvent.

6. The preparation method according to claim 1, characterized in that: The fixed bed reactor is one fixed bed reactor, or a plurality of fixed bed reactors are connected in series to form a multi-stage fixed bed reactor.

7. The preparation method according to claim 1, characterized in that: The catalyst is an active metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium; or the catalyst is a supported active metal catalyst, wherein the active metal is selected from one or more of nickel, palladium, cobalt, platinum or ruthenium.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The source of the trimethylolnitromethane includes preparation from nitromethane and paraformaldehyde or nitromethane and formaldehyde.

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