CN110627654B

CN110627654B - Process for the methylation of amines

Info

Publication number: CN110627654B
Application number: CN201910928935.9A
Authority: CN
Inventors: 张超; 曹忠; 张华�
Original assignee: Sichuan Zhijiang Advanced Materials Co ltd
Current assignee: Sichuan Zhijiang Advanced Materials Co ltd
Priority date: 2019-09-28
Filing date: 2019-09-28
Publication date: 2022-05-06
Anticipated expiration: 2039-09-28
Also published as: CN110627654A

Abstract

The invention discloses a methylation method of amine, which comprises the following steps: hydrogen is taken as a reducing agent, and organic amine, paraformaldehyde and a composite catalyst are subjected to methylation reaction in a solvent; adjusting the pressure of the methylation reaction to (1.5 +/-0.1) Mpa by using hydrogen, adjusting the temperature of the methylation reaction to 40-60 ℃ and reacting for 8-10 h; and carrying out post-treatment on the obtained reaction liquid to obtain an amine methylation product. The invention prepares the composite catalyst for catalytic hydrogenation, so that the aminomethylation yield can reach more than 90 percent, and the byproduct is only water, thereby being green and environment-friendly.

Description

Process for the methylation of amines

Technical Field

The invention belongs to the field of organic synthesis, and particularly relates to a methylation method of organic amine.

Background

Methyl-substituted amines are widely found in natural products and have important applications in the fields of large chemical engineering, fine chemical engineering, pharmaceuticals, dyes, and the like.

From the domestic and foreign literature reported at present, the methylation reagent and the reducing agent are mainly classified into the following types:

1. formaldehyde is used as a methylating agent, and carboxylic acid is used as a reducing agent to carry out reaction. The literature (Synthetic Communications,2002, 32(3),457-465) reports that formic acid and formaldehyde are used as methylating agents to react with ethylenediamine, the reaction temperature is 100 ℃, the conversion rate of the method is high, the product is single, but the problem is that the formic acid is oxidized and decarboxylated, a large amount of carbon dioxide gas is released, and the method does not meet the requirement of green chemistry on atom economy. Meanwhile, when the tetramethylethylenediamine is separated, alkali is needed to neutralize excessive formic acid, the raw material consumption is large, and the generated formate is difficult to treat.

2. Formaldehyde is used as a methylating agent, hydrogen is used as a reducing agent, and the reaction is carried out under the action of a catalyst. The literature (RSC Advances,2014, 4(81), 43195-43203) reports that aniline, paraformaldehyde and hydrogen are used as raw materials, Raney nickel is used as a catalyst, the reaction temperature is 180 ℃, the reaction pressure is controlled at 1.7MPa, the reaction time is 7h, and the yield is 65%. The method takes ethylenediamine, paraformaldehyde and hydrogen as raw materials, Raney nickel as a catalyst, the reaction temperature is 130 ℃, the reaction pressure is controlled at 2MPa, the reaction time is 4.5h, and the yield is 89%. The method has high reaction temperature and low selectivity of the catalyst. In this method, if the reaction temperature is lowered to 60 ℃, the reaction is incomplete, and byproducts such as dimethylethylenediamine are generated, resulting in a reduction in the product yield.

3. Dimethyl carbonate is used as a methylating agent for reaction. The literature (fine and specialty chemicals, 2016,24(09):39-41.) reports that the yield of the product N, N-dimethylaniline can reach 90% by using dimethyl carbonate and aniline as raw materials and reacting at 200 ℃ for 2h under the conditions that the reaction temperature is 1:1.25 and the reaction pressure is 3.5 MPa. The method has the advantages of high reaction yield, short reaction time, higher reaction temperature and reaction pressure, high requirements on equipment, release of carbon dioxide gas in the reaction, non-conformity with the concept of green chemistry, higher price of dimethyl carbonate than formaldehyde and low atom utilization rate.

4. Methanol is used as a methylating agent for reaction. The document (Angewandte Chemie,2011,50(13),3006-3009) uses methanol as a methylating agent to react with aniline, and the yield of dimethylaniline reaches 99% by reacting at 200 ℃ for 36h under the action of a catalyst. The method has high reaction temperature and long reaction time.

5. The methylating agent is methyl iodide, dimethyl sulfate, methyl p-toluenesulfonate, diazomethane, etc. These highly toxic agents present safety hazards and are rather limited in practical use.

Disclosure of Invention

The invention aims to solve the technical problem of providing an amine methylation method which is high in reaction conversion rate, high in selectivity, low in production cost and environment-friendly.

In order to solve the above technical problems, the present invention provides a method for methylation of an amine, comprising:

hydrogen is taken as a reducing agent, and organic amine, paraformaldehyde and a composite catalyst are subjected to methylation reaction in a solvent; adjusting the pressure of the methylation reaction to (1.5 +/-0.1) Mpa by using hydrogen, adjusting the temperature of the methylation reaction to 40-60 ℃ and reacting for 8-10 h;

carrying out post-treatment on the obtained reaction liquid to obtain an amine methylation product;

the molar ratio of the organic amine to the paraformaldehyde is 1: 2.2-4.4, and the composite catalyst accounts for 6-8% of the mass of the organic amine.

As an improvement of the methylation process of the amine of the present invention, the post-treatment is:

cooling the obtained reaction liquid to room temperature, and filtering to respectively obtain filtrate and filter cake;

distilling the filtrate (atmospheric distillation or reduced pressure distillation, namely collecting fractions under the pressure of corresponding to 20mmHg) to obtain an amine methylation product;

the filter cake is a recyclable composite catalyst.

As a further improvement of the methylation process of the amine of the present invention:

the organic amine is ethylenediamine, cyclohexylamine, aniline or benzylamine;

when the organic amine is ethylenediamine, the molar ratio of ethylenediamine to paraformaldehyde is 1: 4.2-4.4,

when the organic amine is cyclohexylamine, aniline or benzylamine, the molar ratio of the organic amine to the paraformaldehyde is 1: 2.2-2.4.

the active component of the composite catalyst consists of Ni, Al, Mo, Cd and Fe.

As a further improvement of the methylation process of the amine of the present invention: in the active components of the composite catalyst, the mass fraction of Ni is (90 +/-2)%, the mass fraction of Al is (8 +/-1)%, the mass fraction of Mo is (1 +/-0.1)%, the mass fraction of Cd is (0.5 +/-0.05)%, and the mass fraction of Fe is (0.5 +/-0.05)%.

The preparation method of the composite catalyst comprises the following steps: weighing Ni-Al-Mo-Cd-Fe alloy powder, controlling the mass fractions of Ni, Al, Mo, Cd and Fe in the alloy powder (according to the requirement of the mass fractions of active components Ni, Al, Mo, Cd and Fe of the finally obtained composite catalyst), and dropwise adding a sodium hydroxide solution into the alloy powder under the condition of ice-water bath for stirring reaction; and filtering the obtained product, and washing a filter cake to obtain the composite catalyst. Because Al can react with sodium hydroxide to form sodium metaaluminate which is dissolved in water, and other components do not react with the sodium hydroxide; by controlling the reaction time, the mass fractions of active components Ni, Al, Mo, Cd and Fe of the obtained composite catalyst can meet the set requirements.

For example, 10g of Ni-Al-Mo-Cd-Fe alloy powder is weighed, wherein the mass fraction of Ni, the mass fraction of Al, the mass fraction of Mo, the mass fraction of Cd and the mass fraction of Fe are 60%, 38.67%, 0.67%, 0.33% and 0.33% respectively; dropwise adding a sodium hydroxide solution with the concentration of 5mol/L into the alloy powder under the condition of ice-water bath (the dropwise adding time is 20 min); then stirring and reacting for 30 min; and filtering the obtained product, and washing a filter cake to obtain the composite catalyst. ICP detection shows that the composite catalyst comprises 90% of Ni, 8% of Al, 1% of Mo, 0.5% of Cd and 0.5% of Fe by mass.

As a further improvement of the methylation process of the amine of the present invention: the solvent is methanol.

The mass ratio of the organic amine to the methanol is about 1 (3 +/-0.5).

The invention has the following technical advantages:

1. the invention solves the problem of low utilization rate of raw material atoms when dimethyl carbonate is used as a methylating agent in the prior art. The method has the advantages that the composite catalyst is prepared for catalytic hydrogenation, so that the aminomethylation yield can reach over 90 percent, and the byproduct is only water, so that the method is green and environment-friendly; when dimethyl carbonate is used as a methylating agent, a large amount of carbon dioxide is generated, which causes a greenhouse effect.

2. Compared with the method 2 in the background art, the method has the technical advantages that: the method has the advantages of low reaction temperature, high selectivity and yield, recyclable catalyst, long service life, more applicable substrates and higher yield.

3. According to the invention, the five-component composite catalyst is prepared, and the Mo, Cd and Fe promoters are added, so that the reaction selectivity is improved, and the production cost is reduced.

4. In the prior art, formic acid is used as a reducing agent, the raw material price is high, a large amount of carbon dioxide is generated, the atom utilization rate is low, and the greenhouse effect is easily caused; and formic acid is easy to form salt of organic amine and is difficult to separate. The invention prepares the composite catalyst for catalytic hydrogenation, so that the aminomethylation yield can reach more than 90 percent, and the byproduct is only water, thereby being green and environment-friendly.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

example 1 preparation of composite catalyst by the following procedure

Weighing 10gNi-Al-Mo-Cd-Fe alloy powder into a beaker, wherein the mass fraction of Ni, Al, Mo, Cd and Fe in the alloy powder is 60%, 38.67%, 0.67%, 0.33% and 0.33% respectively; then 50mL of sodium hydroxide solution with the concentration of 5mol/L is dropwise added into the alloy powder (the dropwise adding time is 20min), the mixture is kept in an ice water bath (about 0 ℃) and is magnetically stirred at 120r/min in the dropwise adding process, and after the dropwise adding is finished, the mixture is continuously stirred for 30min (in the ice water bath, 120 r/min).

Description of the invention: according to the mass fraction reported above, alloy powder as a raw material can be easily obtained according to a known technique.

Secondly, post-treating a reaction product obtained after the stirring reaction, wherein the post-treatment comprises the following steps: filtering the reaction product to respectively obtain a filter cake and a filtrate;

and repeatedly washing the filter cake to be neutral by using deionized water to obtain the composite catalyst, and storing the composite catalyst in water for later use (because the nickel metal is easy to spontaneously combust, the nickel metal needs to be stored in the water). ICP detection shows that the composite catalyst comprises 90% of Ni, 8% of Al, 1% of Mo, 0.5% of Cd and 0.5% of Fe by mass.

The following examples all used the composite catalyst prepared in example 1.

Example 1, a method for producing tetramethylethylenediamine, comprising the steps of:

1) 12g (0.2mol) of ethylenediamine, 25.8g (0.86mol) of paraformaldehyde and 36g of methanol are added into an autoclave, 0.84g of composite catalyst is added, nitrogen is substituted for 3 times, and hydrogen is introduced until the pressure in the autoclave is controlled to be 1.5MPa, the reaction temperature is 50 ℃ and the reaction time is 9 hours.

Description of the drawings: during the whole reaction process, the pressure in the autoclave is required to be controlled to be 1.5MPa all the time by adjusting the using amount of the hydrogen.

2) And after the reaction is finished, cooling to room temperature, filtering, washing a filter cake obtained by filtering to be neutral by using deionized water, and then storing the filter cake in water to be used as a recyclable composite catalyst. Distilling the obtained filtrate at normal pressure, and collecting the fraction at 120 ℃ to obtain the product, namely tetramethylethylenediamine, with the yield of 95% and the purity of 99% by GC detection.

Examples 2 to 9

The molar ratio of ethylenediamine to paraformaldehyde, the amount of catalyst, the reaction time and the reaction temperature in example 1 were changed and the same conditions as in example 1 were adopted to obtain examples 2 to 9, respectively, and the yields of tetramethylethylenediamine as a product were shown in Table 1 (the purities were all about 99%).

TABLE 1

Example 10, the composite catalyst recovered in example 1 is recycled, that is, the recovered composite catalyst is used to replace the original composite catalyst; the rest is identical to example 1, and the obtained results are as in table 2 below in comparison with example 1.

TABLE 2

Example 11, a method for producing dimethylcyclohexylamine, comprising the steps of:

1) 19.8g (0.2mol) of cyclohexylamine, 13.8g (0.46mol) of paraformaldehyde and 59.4g of methanol are added into an autoclave, 1.4g of composite catalyst is added, nitrogen is replaced for 3 times, and hydrogen is introduced until the pressure in the autoclave is controlled at 1.5MPa, the reaction temperature is 50 ℃ and the reaction time is 9 hours.

2) And after the reaction is finished, cooling to room temperature, filtering, washing a filter cake obtained by filtering with deionized water to be neutral, and then storing in water to be used as a recyclable composite catalyst. The obtained filtrate is subjected to reduced pressure distillation (the pressure is 20mmHg), and the fraction at 105 +/-3 ℃ is collected to obtain the product, namely dimethylcyclohexylamine, with the yield of 96 percent and the purity of 99 percent by GC detection.

Examples 12 to 19

The molar ratio of cyclohexylamine to paraformaldehyde, the amount of catalyst used, the reaction time and the reaction temperature in example 11 were varied and the same procedures as in example 11 were repeated to obtain the following examples 12 to 19, respectively, giving dimethylcyclohexylamine yields shown in Table 3 (all having a purity of about 99%).

TABLE 3

Example 20, the composite catalyst recovered in example 11 was recycled, that is, the recovered composite catalyst was used in place of the original composite catalyst; the rest was the same as in example 11, and the results obtained were compared with those of example 11 in Table 4 below.

TABLE 4

Example 21, a method of producing dimethylaniline, comprising the steps of:

1) 9.3g (0.1mol) of aniline, 6.9g (0.23mol) of paraformaldehyde and 27.9g of methanol are added into an autoclave, 0.65g of composite catalyst is added, nitrogen is replaced for 3 times, and hydrogen is introduced until the pressure in the autoclave is controlled at 1.5MPa, the reaction temperature is 50 ℃ and the reaction time is 9 hours.

Description of the invention: during the whole reaction process, the pressure in the autoclave is required to be controlled to be 1.5MPa all the time by adjusting the using amount of the hydrogen.

2) And after the reaction is finished, cooling to room temperature, filtering, washing a filter cake obtained by filtering to be neutral by using deionized water, and then storing the filter cake in water to be used as a recyclable composite catalyst. The obtained filtrate was subjected to reduced pressure distillation (pressure 20mmHg), and fractions at 115 + -3 ℃ were collected to obtain the product, dimethylaniline, with a yield of 96% and a purity of 99% by GC assay.

Examples 22 to 29,

The molar ratio of aniline to paraformaldehyde, the amount of catalyst used, the reaction time and the reaction temperature in example 21 were changed to the same values as in example 21, to obtain the following examples 22 to 29, respectively, and the yields of dimethylaniline obtained were as shown in Table 5.

TABLE 5

Example 30, the composite catalyst recovered in example 21 was recycled, that is, the recovered composite catalyst was used in place of the original composite catalyst; the rest was equivalent to example 21, and the results obtained were compared with example 21 in Table 6 below.

TABLE 6

Example 31, a method for producing dimethylbenzylamine, comprising the steps of:

1) 21.4g (0.2mol) benzylamine, 13.8g (0.46mol) formaldehyde and 64.2g methanol were added to an autoclave, 1.5g of the composite catalyst was added thereto, nitrogen gas was substituted for 3 times, and hydrogen gas was introduced until the pressure in the autoclave was controlled at 1.5MPa, the reaction temperature was 50 ℃ and the reaction time was 9 hours.

2) And after the reaction is finished, cooling to room temperature, filtering, washing a filter cake obtained by filtering to be neutral by using deionized water, and then storing in water to be used as a recyclable composite catalyst. The obtained filtrate was subjected to reduced pressure distillation (pressure 20mmHg), and 117 + -3 deg.C fractions were collected to obtain the product, dimethylbenzylamine, in a yield of 96% and a purity of 99% by GC assay.

Examples 32 to 39 were carried out in the same manner as in example 31 except for changing the molar ratio of benzylamine to paraformaldehyde, the amount of catalyst used, the reaction time and the reaction temperature in example 31, and examples 32 to 39 were respectively obtained with the yields of dimethylbenzylamine shown in Table 7.

TABLE 7

Example 40, the composite catalyst recovered in example 31 was recycled, that is, the recovered composite catalyst was used in place of the original composite catalyst; the rest was equivalent to example 31, and the results obtained were compared with example 31 in Table 8 below.

TABLE 8

Comparative example 1, the composite catalyst in example 1 was changed to 100% -Ni, 90% Ni-10% Al, 90% Ni-8% Al-2% Mo, 90% Ni-8% Al-1% Mo-1% Cd, 90% Ni-8% Al-1% Mo-1% Fe, respectively, with the same amount; the rest is equivalent to example 1, and the yield of the obtained product is shown in table 9 in comparison with example 1.

Comparative example 2, the composite catalyst in example 11 was changed to 100% -Ni, 90% Ni-10% Al, 90% Ni-8% Al-2% Mo, 90% Ni-8% Al-1% Mo-1% Cd, 90% Ni-8% Al-1% Mo-1% Fe, respectively, with the same amount; the rest is equivalent to example 11, and the yield of the obtained product is shown in Table 9 in comparison with example 11.

Comparative example 3, the composite catalyst in example 21 was changed to 100% -Ni, 90% Ni-10% Al, 90% Ni-8% Al-2% Mo, 90% Ni-8% Al-1% Mo-1% Cd, 90% Ni-8% Al-1% Mo-1% Fe, respectively, with the same amount; the rest was identical to example 21, and the yield of the obtained product compared with that of example 21 is shown in Table 9.

Comparative example 4 the composite catalyst of example 31 was modified to 100% -Ni, 90% Ni-10% Al, 90% Ni-8% Al-2% Mo, 90% Ni-8% Al-1% Mo-1% Cd, 90% Ni-8% Al-1% Mo-1% Fe, respectively, with the amounts used being unchanged; the rest is equivalent to example 31, and the yield of the obtained product is shown in Table 9 in comparison with example 31.

TABLE 9

The preparation method of the composite catalyst used in the above comparative example was as follows:

first, 90% Ni-10% Al:

weighing 10gNi-Al alloy powder into a beaker, wherein the mass percent of Ni and the mass percent of Al in the alloy powder are 50%, then dropwise adding 100mL of 5mol/L sodium hydroxide solution into the alloy powder (the dropwise adding time is 20min), keeping in an ice water bath and magnetically stirring at 100r/min in the dropwise adding process, after the dropwise adding is finished, continuously stirring for 30min (in the ice water bath, 100r/min), and carrying out the post-treatment after the reaction is finished in the same way as in example 1.

II, 90% of Ni-8% of Al-2% of Mo:

weighing 10gNi-Al-Mo alloy powder into a beaker, wherein the mass fraction of Ni in the alloy powder is 60%, the mass fraction of Al is 38.67%, and the mass fraction of Mo is 1.33%, then dropwise adding 50mL of 5mol/L sodium hydroxide solution into the alloy powder (the dropwise adding time is 20min), during the dropwise adding process, keeping in an ice water bath and magnetically stirring at 120r/min, after the dropwise adding is finished, continuously stirring for 30min (in the ice water bath, at 120r/min), and carrying out the post-treatment after the reaction is finished in the same way as in example 1.

Thirdly, 90% of Ni-8% of Al-1% of Mo-1% of Cd:

weighing 10gNi-Al-Mo-Cd alloy powder into a beaker, wherein the mass fraction of Ni in the alloy powder is 60%, the mass fraction of Al is 38.66%, the mass fraction of Mo is 0.67%, and the mass fraction of Cd is 0.67%, then dropwise adding 50mL of 5mol/L sodium hydroxide solution into the alloy powder (dropwise adding time is 20min), keeping the mixture in an ice-water bath and stirring by a magnetic force of 120r/min during the dropwise adding process, continuously stirring for 30min (in the ice-water bath, 120r/min) after the dropwise adding is finished, and carrying out the post-treatment after the reaction in the same example 1.

Fourthly, 90% of Ni-8% of Al-1% of Mo-1% of Fe:

weighing 10gNi-Al-Mo-Fe alloy powder into a beaker, wherein the mass fraction of Ni, Al, Mo and Fe in the alloy powder is 60%, 38.66%, 0.67% and 0.67%; then 50mL of sodium hydroxide solution with the concentration of 5mol/L is dropwise added into the alloy powder (the dropwise adding time is 20min), the mixture is kept in an ice water bath and is magnetically stirred at 120r/min in the dropwise adding process, stirring is continued for 30min (in the ice water bath, 120r/min) after the dropwise adding is finished, and the post-treatment after the reaction is finished is the same as that in example 1.

As can be seen from the above examples, the five-component composite catalyst is used as the catalyst for the reduction reaction, so that the chemical selectivity of the reaction and the yield of the methylated product are effectively improved, the yield can reach over 90 percent, and the production cost is saved.

Comparative example 5, the "reaction pressure 1.5Mpa, reaction temperature 50 ℃ and reaction time 9 h" in example 1 was changed to "reaction pressure 2Mpa, reaction temperature 130 ℃ and reaction time 4.5 h", and the rest was identical to example 1, and the yield of the obtained product was only about 67%.

Finally, it is also noted that the above-mentioned list is only a few specific embodiments of the present invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims

1. A process for the methylation of amines, characterized in that:

the composite catalyst accounts for 6-8% of the mass of the organic amine;

the organic amine is ethylenediamine, cyclohexylamine, aniline or benzylamine;

when the organic amine is cyclohexylamine, aniline or benzylamine, the molar ratio of the organic amine to the paraformaldehyde is 1: 2.2-2.4;

the active component of the composite catalyst consists of Ni, Al, Mo, Cd and Fe;

in the active components of the composite catalyst, the mass fraction of Ni is 90%, the mass fraction of Al is 8%, the mass fraction of Mo is 1%, the mass fraction of Cd is 0.5%, and the mass fraction of Fe is 0.5%.

2. Process for the methylation of amines according to claim 1, characterized in that the work-up is:

distilling the filtrate to obtain an amine methylation product;

the filter cake is a recyclable composite catalyst.

3. Process for the methylation of amines according to claim 1 or 2, characterized in that: the solvent is methanol.