CN101157626A

CN101157626A - Method for purifying N,N-dimethyl formamide

Info

Publication number: CN101157626A
Application number: CNA2007101351537A
Authority: CN
Inventors: 崔鹏; 姚运金
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2007-10-26
Filing date: 2007-10-26
Publication date: 2008-04-09
Anticipated expiration: 2027-10-26
Also published as: CN101157626B

Abstract

The invention relates to a purifying method for N, N-dimethylformamide. The invention is characterized in that DMF solution which includes formic acid contactes with load type metal catalyst under the oxygen deficiency condition to carry a catalyst reaction; and the formic acid of the DMF solution is transformed into carbon dioxide and hydrogen after being catalyzed so as to purify the DMF solution. The invention catalyzes and decomposes the formic acid into CO2 and H2. Besides, the invention has the advantages of mild reaction condition, low device investment, low production cost, easy operation. No new impurity is brought into the whole system.

Description

Method for purifying N, N-dimethylformamide

The technical field is as follows:

the invention relates to a method for purifying an N, N-dimethylformamide solution containing formic acid impurities. More specifically, the method is a purification treatment method for promoting the decomposition and destruction of formic acid contained in an N, N-dimethylformamide solution by a noble metal catalysis method.

Background art:

n, N-Dimethylformamide (DMF), the structural formula is: HCON (CH)₃)₂. It is a colorless, transparentviscous liquid at room temperature, melting point: -61 ℃, boiling point 153 ℃, relative density 0.9487, it is highly polar and somewhat toxic. DMF has strong dissolving capacity, has been known as "universal solvent", is used as important chemical raw material and solvent with excellent performance, and is mainly applied to polyurethane, acrylon and medicineIndustries such as pesticide, dye, electronics and the like. The polyurethane resin is used as a washing curing agent in the polyurethane industry and is mainly used for the production of wet synthetic leather; the method is used for synthesizing high-efficiency low-toxicity pesticide in the pesticide industry; the dye is used as a dye solvent in the dye industry; the quenching agent is used as a quenching agent for tin-plated parts and a cleaning agent for circuit boards in the electronic industry.

In the absence of acid, alkali and water, DMF is relatively stable even if heated to a boiling point, but DMF is hydrolyzed in the presence of water, and the acid, alkali and oxygen all play a catalytic role in hydrolysis, which has a great influence on the purity and use of DMF. Hydrolysis of DMF leads to formic acid and dimethylamine, the formation of formic acid will further facilitate the hydrolysis:

HCON(CH₃)₂+H₂O→HCOOH+(CH₃)₂NH

HCON(CH₃)₂+H₂O+H⁺→ HCOOH+NH₂(CH₃)₂ ⁺meanwhile, formic acid and DMF can form an azeotrope with a high boiling point, so that the DMF is more difficult to refine. Therefore, finding a suitable method for removing formic acid from DMF solution has certain practical significance.

At present, in the production process of DMF internationally, the methods commonly used for removing formic acid in DMF solution are distillation, neutralization, adsorption and the like. However, these methods may cause partial decomposition of DMF or introduce new impurities, which is not favorable for improving the quality of DMF product, or because high temperature and high pressure are used, a large amount of energy and related equipment are required, and the industrial production investment is large, which leads to increase of production cost.

The invention content is as follows:

the invention aims to avoid the defects of the prior art and provides an effective N, N-dimethylformamide purification method with mild reaction conditions, small equipment investment and low production cost₂And H₂So that no new impurities are introduced into the whole system.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the method for purifying the N, N-dimethylformamide is characterized in that under the condition of oxygen deficiency, a DMF solution containing formic acid is contacted with a supported metal catalyst to carry out catalytic reaction, and the formic acid in the DMF solution is converted into carbon dioxide and hydrogen after the catalytic reaction, so that the purification treatment of the DMF solution is completed.

The purification method of the invention is also characterized in that:

the method comprises the following process steps:

a. firstly, activating the supported metal catalyst by a hydrogen reduction method, then placing the activated supported metal catalyst in a fixed bed reactor, ensuring that the catalyst is not lost, introducing inert gas to remove oxygen possibly existing in the reactor, controlling the temperature of the reactor to be 80-150 ℃and the pressure to be normal pressure;

b. introducing a DMF solution containing formic acid to be treated under the condition of keeping introducing inert gas, fully contacting the DMF solution with the catalyst, and carrying out catalytic reaction for 10-60 minutes to obtain a purified DMF solvent.

The purification method of the invention is also characterized in that:

the catalyst carrier of the supported metal catalyst is active carbon and Al₂O₃Or MgO.

The supported active metal of the supported metal catalyst is palladium (Pd), rhodium (Rh) or platinum (Pt), and the mass percentage of the supported active metal in the catalyst is 0.1-10%;

the inert gas is nitrogen or argon.

Compared with the prior art, the invention has the beneficial effects that:

1. the main chemical reactions involved in the process of the invention are:

it is evident that formic acid can be decomposed to CO using noble metal catalysis₂And H₂No new impurities are introduced, and no influence is caused on the DMF product.

2. Although the catalytic reaction can be carried out in any conventional normal-temperature normal-pressure catalytic oxidation reactor, the reaction efficiency can be remarkably improved by setting the reaction temperature of the DMF to be 80-150 ℃ in the method of the invention because the DMF is easy to decompose under the condition of oxygen and higher temperature.

3. The method has simple and convenient operation, can be carried out intermittently or continuously, has the characteristics of high efficiency and mild reaction conditions, requires simple equipment and consumes low energy, and provides a new way for treating the formic acid-containing wastewater and removing the formic acid in other organic solutions.

4. The method of the invention reasonably uses the inert gas, and can effectively and simultaneously remove CO dissolved in the solution₂、H₂And O₂。

Drawings

FIG. 1 is a schematic diagram of a fixed bed reactor used in the practice of the present invention for the catalytic decomposition of formic acid in DMF solution.

Reference numbers in the figures: 1 gas inlet, 2 product outlets, 3 gas outlets and 4 material inlets.

The invention is further described by the following detailed description in conjunction with the accompanying drawings.

The specific implementation mode is as follows:

example 1:

the platinum carbon catalyst is used for removing formic acid impurities in the DMF solution, and the corresponding reaction steps are as follows:

1. catalyst pretreatment

50g of platinum-carbon catalyst was added to the fixed bed reactor, and the mass percentage of platinum in the platinum-carbon catalyst was 1%, as shown in FIG. 1. In the figure the gas inlet 1 and the product outlet 2 are in the lower part of the reactor and the gas outlet 3 and the material inlet 4 are in the upper part of the reactor. At atmospheric pressure, the reactor was heated to 250 ℃ and the air in the reactor was displaced with nitrogen. Then, the nitrogen gas in the reactor was replaced with hydrogen gas, the platinum-carbon catalyst was reduced to activate the catalyst, and after half an hour of the reaction, the hydrogen gas in the reactor was purged with nitrogen gas.

2. Formic acid removal from DMF solution

When the temperature in the reactor is kept at 100 ℃, DMF solution containing formic acid impurities is continuously introduced from the top of the fixed bed, the flow rate is kept at 0.2mL/s, the concentration of formic acid is 0.2mol/L, the catalytic reaction time in the reactor is kept at 30 minutes, a purified DMF product can be obtained from the bottom of the reactor, and the removal rate of formic acid reaches 100% after analysis.

Example 2:

the selected catalyst is palladium-carbon catalyst powder, the mass percent of palladium in the palladium-carbon catalyst is 1%, the other contents are the same as those in the embodiment 1, and finally, analysis shows that the removal rate of formic acid reaches 96%.

Example 3:

the temperature used for the catalytic reaction was 150 ℃ and the rest was the same as in example 1, and finally, the formic acid removal rate was 95% by analysis.

Claims

A process for purifying N, N-dimethyl formamide includes such steps as catalytic reaction between the solution of DMF containing formic acid and the supported metal catalyst in the absence of oxygen to convert formic acid into carbon dioxide and hydrogen, and purifying.
2. The method for purifying N, N-dimethylformamide as claimed in claim 1, characterized in that the method comprises the following steps:

a. firstly, activating the supported metal catalyst by a hydrogen reduction method, then placing the activated supported metal catalyst in a fixed bed reactor, ensuring that the catalyst is not lost, introducing inert gas to remove oxygen possibly existing in the reactor, controlling the temperature of the reactor to be 80-150 ℃ and the pressure to be normal pressure;

b. introducing a DMF solution containing formic acid to be treated under the condition of keeping introducing inert gas, fully contacting the DMF solution with the catalyst, and carrying out catalytic reaction for 10-60 minutes to obtain a purified DMF solvent.
3. The method for purifying N, N-dimethylformamide as claimed in claim 1 or 2, wherein the N, N-dimethylformamide is purified by the method

The catalyst carrier of the supported metal catalyst is active carbon and Al₂O₃Or MgO.

The supported active metal of the supported metal catalyst is palladium (Pd), rhodium (Rh) or platinum (Pt), and the mass percentage of the supported active metal in the catalyst is 0.1-10%;

the inert gas is nitrogen or argon.