CN104141148B - A kind of method of electrochemical synthesis trimethylamine - Google Patents

Abstract

A method for electrochemically synthesizing trimethylamine is to mix N,N-dimethylformamide and water in proportion to form a solution at normal temperature and pressure, then add a supporting electrolyte tetramethylammonium chloride to form an electrolyte, and Add it into a closed electrolytic cell, stir it well, then pass nitrogen gas into the electrolytic cell for electrochemical reaction, and then pass the gas product through a strong alkali solution to remove impurities to obtain trimethylamine with a purity of 99%. The method has simple process, convenient operation, high-purity trimethylamine is easy to collect, opens up a new way for the synthesis of amine organic matter, and is a process route with great industrial synthesis value.

Description

A kind of method of electrochemically synthesizing trimethylamine

technical field

The invention relates to a method for synthesizing trimethylamine, in particular to a technical scheme for synthesizing trimethylamine by an electrochemical method.

Background technique

Trimethylamine is a tertiary amine with a molecular formula of C ₃ H ₉ N. It is an important chemical product used in pesticides, dyes, medicine and organic synthesis; it is used as a disinfectant, an alarm agent for natural gas, an analytical reagent and a raw material for organic synthesis. It is also used as a raw material for medicine, pesticide, photographic materials, rubber additives, explosives, chemical fiber solvents, surfactants and dyes. The reaction product with ethylene oxide is used as a catalyst for polycondensation reaction; the reaction product choline chloride with 2-chloroethanol is used as an additive for chicken feed. The main organic synthetic raw material can be used to produce various industrial additives, surfactants and dyes, ion exchange resins, flocculants, other cationic polymers, etc.

Most of the existing production methods of trimethylamine are required to be completed under high temperature and high pressure, which requires relatively high equipment and energy consumption. The publication number is CN203112720U "A device for preparing methylamine by vapor-phase ammoniation of methanol" uses a mixture of various metal oxides such as activated alumina, silicon oxide, titanium dioxide, tungsten trioxide, clay, and thorium oxide as a catalyst. The reaction temperature is 250-500 ⁰ C, the reaction pressure is 0.5-5.0 MPa, and the space velocity is 500-1500h ^-1 . Methanol reacts with ammonia to form a mixture of primary, secondary, and tertiary amines. The formation ratio of the three amines is related to raw materials, catalysts and reaction conditions. The desired product can be obtained by adjusting the ratio of methanol and ammonia. Methanol:ammonia=1:4 is the best condition for the formation of monomethylamine, and methanol:ammonia=1:1.5 is the best condition for the formation of trimethylamine. The obtained trimethylamine often contains methanol, methylamine, dimethylamine and other impurities, which can be refined by extractive distillation or azeotropic distillation. To obtain pure trimethylamine, acetic anhydride or acetyl chloride can be added for distillation. Primary and secondary amines will form acetylated products, which have high boiling points and are difficult to distill out. Treat the distilled trimethylamine with activated alumina, add sodium fluorenone and dry it for later use. Alternatively, passing it through a drying tower filled with solid potassium hydroxide yields pure dry gaseous trimethylamine. The operation process is relatively complicated and requires high energy and equipment.

In the present invention, during the "research on the electrochemical synthesis of ethylene and oxalic acid in pairs of acetylene", it was found that a large amount of gas was generated in the reaction, and the gas product was directly collected by a gas collection device, and the product was detected by gas chromatography, and the product was determined to be trimethyl Amines, domestic and foreign related papers and patents were searched, and no report was found on the synthesis of trimethylamine using N,N-dimethylformamide as a raw material by an electrochemical method.

In the publication number CN102976950 "an improved process for preparing tertiary amines", the main reaction is to prepare trimethylamine with fatty alcohol and dimethylamine, which is characterized in that: when the reaction conversion rate of the main reaction is 80-90%, the hydrogen in the reactor is , trimethylamine, a small amount of monomethylamine, and a small amount of dimethylamine mixed gas are passed into the absorption tower, and the mono, di, and trimethylamine are absorbed by water, and then the pure hydrogen is passed into the reactor, and the reaction is continued, and finally separated to obtain Trimethylamine. The publication number is CN101062896A "Manufacturing method of trimethylamine", which provides a method for efficiently producing insufficient trimethylamine while reducing energy consumption costs by using a zeolite catalyst when producing methylamine. The method for producing trimethylamine is characterized in that, in the method for producing methylamine by using methanol and ammonia, mixing methanol and methylamine and ammonia, or a mixture of methylamine and ammonia, using a zeolite catalyst, including separating and purifying formazan from the obtained reaction mixture Amines, after separation of ammonia and trimethylamine, the process of making dimethylamine or a mixture containing 50 mol% or more of dimethylamine and monomethylamine react with ammonia in the gas phase. Zhang Fulai et al. published in Tianjin Chemical Industry in 2003 titled "Industrialization Process of Synthetic Amines", using methanol and ammonia as raw materials, under high temperature of 400-420°C and high pressure of 5MPa, with amorphous aluminum silicate The reaction is carried out as a catalyst to prepare a mixture of three amines mainly composed of methylamine, dimethylamine and trimethylamine, which are roughly mixed, and then purified by fractional distillation to obtain methylamine, dimethylamine and trimethylamine with higher purity. These operating processes are relatively complex and require high energy and equipment.

Contents of the invention

The invention provides a method for electrochemically synthesizing trimethylamine to overcome the deficiencies in the prior art of harsh equipment and reaction conditions, complicated process flow and environmental pollution.

Realize above-mentioned object, the measure that the present invention takes is a kind of method for electrochemically synthesizing trimethylamine, and its described method is as follows:

(1) Preparation of raw materials

Distill N,N-dimethylformamide and anhydrous Na ₂ CO _3- two times under reduced pressure to obtain high-purity N,N-dimethylformamide for storage; dissolve tetramethylammonium chloride in ethanol, After recrystallization twice, vacuum dry storage; After the electrode is polished, it is cleaned with distilled water, and the surface grease is removed by wiping with acetone;

(2) Electrochemical reaction

At normal temperature and pressure, mix N,N-dimethylformamide and water in step (1) with a volume ratio of 5:1-10:1 to form a solution, and add the supporting electrolyte tetramethyl chloride Ammonium 0.1-1.0mol/L is mixed into an electrolyte solution, then added to a closed electrolytic cell, fully stirred, and then nitrogen gas is passed into the above electrolytic cell for 1 hour, and the electrochemical reaction is carried out at a current density of 140-450mA/ ^cm2 , and finally the gas product is removed by a 3-6mol/L strong alkali solution to obtain trimethylamine with a purity of 99%, which is collected by a gas collection device.

Further technical scheme is as follows.

The N,N-dimethylformamide and water are mixed into a solution according to the volume ratio of 7:1, and the supporting electrolyte tetramethylammonium chloride 0.5mol/L is added to mix into an electrolyte solution to obtain trimethylamine.

The anode of the electrolytic cell is one of Pd, Pt, Au and Ti based oxide electrodes.

The cathode of the electrolytic cell is one of Cu, Ag and Ni.

The strong alkali solution is sodium hydroxide or potassium hydroxide.

Compared with the prior art, the method for electrochemically synthesizing trimethylamine provided above by the present invention has the following characteristics.

(1) The existing technology requires the reaction to be carried out under normal temperature and pressure conditions at a high temperature of 400-420°C and a high pressure of 5 MPa. The reaction conditions are mild and the requirements for equipment are very low.

(2) The reducing agent required in the reaction process is generated in situ electrochemically, and at the same time, trimethylamine is prepared in situ. The in situ generation and in situ utilization are carried out in the same system, which simplifies the reaction steps and shortens the reaction time.

(3) The product produced by the prior art is a mixture of monomethylamine, dimethylamine, and trimethylamine, and the separation process is relatively cumbersome. In this reaction, high-purity trimethylamine can be obtained through a saturated strong alkali solution, and the process flow is simple.

(4) The existing technology requires the use of amorphous aluminum silicate as a catalyst for the reaction. The reactant of this reaction is clean electrons, which will not produce secondary pollution by-products. It is an environmentally friendly reduction synthesis technology.

(5) It is difficult to control the interruption and stop of the reaction in the prior art, but the reaction is easy to control, that is, the start, interruption and stop of the reaction can be controlled by controlling the voltage, realizing the continuous and large-scale production of energy saving, emission reduction and environmental protection An environmentally friendly clean production method.

detailed description

The method of the present invention is further illustrated by the following specific examples.

Implement a method for electrochemically synthesizing trimethylamine, the method is to mix N,N-dimethylformamide and water into a solution at a volume ratio of 5:1-10:1 at normal temperature and pressure , then add supporting electrolyte Tetramethylammonium Chloride 0.1-1.0mol/L to mix into an electrolyte solution, and add it into a closed electrolytic cell, stir well, pass nitrogen gas into the above electrolytic cell for 1 hour, and then use 140-450mA/ The current density of cm ² is used for electrochemical reaction, and then the gas product is removed by 3-6mol/L strong alkali solution to obtain trimethylamine with a purity of 99%, which is collected by a gas collection device.

Example 1

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 7:1 to form a 30mL solution, then add a supporting electrolyte of 0.5mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 350mA/ ^cm2 , select the Pt electrode as the anode, and the Cu electrode as the cathode, and pass the gas product through 5mol/cm2 L sodium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 95%, the yield is 89%, and the current efficiency is 76%. The gas is removed with sodium hydroxide solution to obtain trimethylamine with a purity of 99%.

Example 2

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 6:1 to form a 30mL solution, then add a supporting electrolyte of 0.3mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 250mA/ ^cm2 , select Au electrode as anode, Pd electrode as cathode, and pass the gas product through 4mol/cm2 L sodium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 93%, the yield is 87%, and the current efficiency is 75%. The gas is removed with sodium hydroxide solution to obtain trimethylamine with a purity of 98%.

Example 3

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 5:1 to form a 30mL solution, then add a supporting electrolyte of 0.6mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 300mA/ ^cm2 , choose Ti-based oxide electrode as anode, Ni electrode as cathode, and gas product Remove impurities by 5mol/L sodium hydroxide solution, collect them through a gas collection device, and then use a gas chromatography spectrometer from Agilent Company of the United States, model: 7890A-5975C; ion source ionization mode: EI, detect the product, and confirm that the product is Trimethylamine, the conversion rate is 92%, the yield is 81%, and the current efficiency is 72%. The gas is removed with sodium hydroxide solution to obtain trimethylamine with a purity of 97%.

Example 4

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 8:1 to form a 30mL solution, then add a supporting electrolyte of 0.7mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 240mA/cm ² , select the Ti-based oxide electrode as the anode, and the Cu electrode as the cathode, and the gas product Remove impurities by 5mol/L sodium hydroxide solution, collect them through a gas collection device, and then use a gas chromatography spectrometer from Agilent Company of the United States, model: 7890A-5975C; ion source ionization mode: EI, detect the product, and confirm that the product is Trimethylamine, the conversion rate is 90%, the yield is 83%, and the current efficiency is 72%. The gas is removed with sodium hydroxide solution to obtain trimethylamine with a purity of 96%.

Example 5

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 9:1 to form a 30mL solution, then add a supporting electrolyte of 0.8mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 410mA/ ^cm2 , select the Pt electrode as the anode, and the Pd electrode as the cathode, and pass the gas product through 6mol/cm2 L sodium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 92%, the yield is 84%, and the current efficiency is 74%. The gas is removed with sodium hydroxide solution to obtain trimethylamine with a purity of 98%.

Example 6

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 10:1 to form a 30mL solution, then add a supporting electrolyte of 0.3mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 400mA/ ^cm2 , select the Pt electrode as the anode, and the Ni electrode as the cathode, and pass the gas product through 6mol/cm2 The L potassium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 93%, the yield is 83%, and the current efficiency is 70%. The gas is removed with potassium hydroxide solution to obtain trimethylamine with a purity of 98.5%.

Example 7

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 6:1 to form a 30mL solution, then add a supporting electrolyte of 0.4mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction at a current density of 450mA/ ^cm2 , select the Pt electrode as the anode, and the Ag electrode as the cathode, and pass the gas product through 6mol/cm2 The L potassium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 89%, the yield is 84%, and the current efficiency is 71%. The gas is removed with potassium hydroxide solution to obtain trimethylamine with a purity of 97%.

Example 8

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 7:1 to form a 30mL solution, then add a supporting electrolyte of 0.5mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction with a current density of 400mA/ ^cm2 , select the Pd electrode as the anode, and the Cu electrode as the cathode, and pass the gas product through 6mol/cm2 The L potassium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate is 87%, the yield is 83%, and the current efficiency is 70%. The gas is removed with potassium hydroxide solution to obtain trimethylamine with a purity of 95%.

Example 9

At normal temperature and pressure, mix N,N-dimethylformamide and water at a volume ratio of 7:1 to form a 30mL solution, then add a supporting electrolyte of 0.5mol/L tetramethylammonium chloride to form an electrolyte, and add a In the airtight electrolytic cell, fully stir, pass nitrogen gas into the above electrolytic cell for 1 hour, and then carry out electrochemical reaction with a current density of 350mA/ ^cm2 , select the Pd electrode as the anode, and the Ag electrode as the cathode, and pass the gas product through 5mol/cm2 The L potassium hydroxide solution was used to remove impurities, collected by a gas collection device, and then adopted a gas chromatography spectrometer from Agilent Corporation of the United States, model: 7890A-5975C; ion source ionization mode: EI, to detect the product, confirm that the product is trimethylamine, The conversion rate was 88%, the yield was 83%, and the current efficiency was 74%. The gas was removed with potassium hydroxide solution to obtain trimethylamine with a purity of 93.5%.

Claims (5)

1. a method for electrochemical synthesis trimethylamine, its described method is as follows:

(1) preparation of raw material

By N,N-dimethylformamide and anhydrous Na₂CO_3-Decompression distillation obtains highly purified N,N-dimethylformamide for twice and stores；Tetramethyl ammonium chloride is dissolved in ethanol, twice final vacuum stored dry of recrystallization；Cleaned by distilled water again after electrode polishing, remove surface oils and fats with acetone wiping；

(2) electrochemical reaction

At normal temperatures and pressures, by the N in step (), the ratio that dinethylformamide and water are 5:1-10:1 by volume is mixed into solution, and add supporting electrolyte tetramethyl ammonium chloride 0.1-1.0mol/L and be mixed into electrolyte, add an airtight electrolyzer, it is sufficiently stirred for, states electrolyzer then up and pass into the nitrogen of 1 hour, and with 140-450mA/cm²Electric current density be electrochemically reacted, finally gaseous product is carried out remove impurity by 3-6mol/L strong base solution, it is thus achieved that purity is the trimethylamine of 99%, is collected by gas collector.

2. the method for claim 1, is mixed into solution by described DMF and water according to the ratio that volume ratio is 7:1, and adds supporting electrolyte tetramethyl ammonium chloride 0.5mol/L and be mixed into electrolyte, it is thus achieved that trimethylamine.

3. the method for claim 1, the anode of described electrolyzer is the one in Pt, Pd, Au and Ti base oxide electrode.

4. the method for claim 1, the negative electrode of described electrolyzer is the one in Cu, Ag and Ni.

5. the method for claim 1, described strong base solution is sodium hydroxide or potassium hydroxide.