CN107011193B

CN107011193B - Method for preparing N-methyl p-anisidine

Info

Publication number: CN107011193B
Application number: CN201710320824.0A
Authority: CN
Inventors: 袁航空; 黄永吉; 赵祥涛; 石峰
Original assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Current assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Priority date: 2017-05-09
Filing date: 2017-05-09
Publication date: 2020-05-26
Anticipated expiration: 2037-05-09
Also published as: CN107011193A

Abstract

The invention discloses a method for preparing N-methyl-p-anisidine, which takes p-anisidine and methanol as reaction raw materials, takes a molecular sieve loaded active component as a catalyst, and has the reaction temperature of 150-350 ℃ and the liquid volume airspeed of 0.1-2.0 h^‑1、N₂Reacting in a fixed bed continuous flow reactor under the condition of serving as a carrier gas to obtain N-methyl p-anisidine; the active component is at least one of Cu and Ni, and the content of the active component is 0.01-30 wt% of the mass of the catalyst; the molecular sieve is one of 3A, 4A and 5A molecular sieves. The method has the advantages of high yield, simple operation, mild condition, stable catalyst performance, low cost and low pollution.

Description

Method for preparing N-methyl p-anisidine

Technical Field

The invention relates to a method for preparing N-methyl p-anisidine. In particular to a method for preparing N-methyl p-anisidine with high selectivity by using p-anisidine and methanol as raw materials and using molecular sieve loaded copper nickel as a catalyst to realize N-monomethylation through an aminoalcohol alkylation reaction.

Background

The octane number is the most important quality index of the motor gasoline, which comprehensively reflects the national oil refining industry level and the vehicle design level, and the adoption of the antiknock agent is an important means for improving the octane number of the motor gasoline. The antiknock agent mainly comprises alkyl lead, methylcyclopentadienyl manganese tricarbonyl, methyl tert-butyl ether, methyl tert-amyl ether, tert-butyl alcohol, methanol, ethanol and the like. The pollution-free anti-knock additive is the development direction in the future.

The tetraethyl lead has the advantages of simple process, low cost and outstanding effect, and has been widely used since being found in 1921. However, with the need for automobile exhaust emission control and environmental protection, the addition of alkyl lead to gasoline has been internationally restricted, and the reduction of lead and the unleading of gasoline have been gradually achieved. Methylcyclopentadienyl manganese tricarbonyl antiknock agents were introduced in the united states in 1959, but the antiknock agents form porous deposits on the internal surfaces of engine combustion chambers, shorten the life of spark plugs, and cause an increase in the manganese content in the environment, and thus are banned from the united states in 1978. Methanol, ethanol, methyl tert-butyl ether, tert-butyl alcohol and the like are further used as organic nonmetal antiknock agents at home and abroad after the 70 th century, thereby providing a choice for seeking a new gasoline blending scheme. However, these organic antiknock agents have problems of volatility, corrosiveness, toxicity, exhaust emission, and economy. The typical anti-knock agent methyl tert-butyl ether is prohibited from being used in the United states due to water quality pollution.

The research on the performance of aromatic amine and other nitrogen-containing compounds shows that the aromatic amine and other nitrogen-containing compounds have better octane number improving effect, and the development of the aromatic amine and other nitrogen-containing compounds is greatly promoted due to the advantages of low volatility and the like. Among them, N-methylaniline has been widely used as an antiknock agent for gasoline. However, N-methylaniline also has the problems of high toxicity, environmental pollution and the like. How to develop an efficient and clean antiknock agent becomes an important issue in the production of clean gasoline. Compared with N-methylaniline, the N-methyl p-methoxyaniline as the antiknock agent has the characteristics of low toxicity and better performance, and becomes an ideal choice for replacing the N-methylaniline.

It has been shown that the reaction of p-anisidine with methanol as alkylating agent is the most economical and environment-friendly route for producing N-methyl-p-anisidine, and patents CN 103124717A, CN 103570553B, RU 2270187, US 8901354, US 5068434, US 5055617 and US 4029707 with the same or similar structural compounds show that the N-monomethyl compound produced during the reaction is easy to react with alcohol to further produce N, N-dimethylated product; the patent CN 105924363A adopts p-anisidine and paraformaldehyde as raw materials, and the method for preparing N-methyl-p-anisidine through reductive amination also has the problems of large use of non-green solvents, high-pressure hydrogen gas requirement, incapability of continuous production in the process and the like, and no enterprise realizes industrial production of the N-methyl-p-anisidine at home and abroad so far based on the reasons. It should be noted that, at present, many foreign manufacturing enterprises are researching and developing catalysts for industrial production of N-methyl p-anisidine, and the competition of related technologies is very strong, so that it is imperative to accelerate related research and development and promote industrialization.

Disclosure of Invention

The invention aims to provide a method for preparing N-methyl-p-anisidine.

The method takes p-anisidine and methanol as raw materials and takes molecular sieve loaded copper nickel as a catalyst to efficiently synthesize the N-methyl-p-anisidine compound under simpler equipment and milder reaction conditions. The method has the advantages of high yield, simple operation, mild condition, stable catalyst performance, low cost and low pollution.

According to the molecular sieve loaded copper-nickel catalyst, active metal ions are embedded in a molecular sieve lattice through ion exchange, the action of reaction molecules and the catalyst active metal ions is controlled by utilizing the aperture size of the molecular sieve, and the contact time of the reaction molecules and the catalyst is controlled through the regulation and control of kinetic factors, so that the further reaction of an N-monomethylation product and methanol to generate an N, N-dimethyl p-anisidine byproduct is reduced, and the high-selectivity preparation of the product is realized; and due to the protection effect of the molecular sieve crystal lattice, the active metal ions avoid the clustering of nano particles, prolong the catalytic activity time and improve the overall performance of the catalyst.

A method for preparing N-methyl-p-methoxyaniline is characterized in that p-methoxyaniline and methanol are used as reaction raw materials, a molecular sieve loaded active component is used as a catalyst, and the reaction temperature is 150-350 ℃ and the liquid volume space velocity is 0.1-2.0 h^-1、N₂Reacting in a fixed bed continuous flow reactor under the condition of serving as a carrier gas to obtain N-methyl p-anisidine; the active component is at least one of Cu and Ni, and the content of the active component is 0.01-30 wt% of the mass of the catalyst; the molecular sieve is one of 3A, 4A and 5A molecular sieves.

The molar ratio of the methanol to the p-anisidine is 0.8: 1-20: 1.

the carrier gas N₂The volume space velocity is 100-600h^-1。

The catalyst is prepared by the following method: adding a molecular sieve into a water solution of soluble salt containing an active component, stirring for 5-24 hours at room temperature for ion exchange, then drying for 1-5 hours at 50-180 ℃, roasting for 5-15 hours at 200-800 ℃, and reducing for 1-5 hours at 200-800 ℃ by using hydrogen to obtain the catalyst.

The soluble salt is nitrate or chloride of the active component.

Compared with the prior art, the method for preparing the N-methyl-p-methoxyaniline adopts p-methoxyaniline and methanol as base sources, is economical and easy to obtain, and has high atom utilization rate; the catalyst used in the invention has the advantages of simple and ingenious design, low price, high efficiency, stability, few byproducts and high selectivity of the p-N-methyl-p-methoxyaniline.

Detailed Description

The present invention is described in detail below with reference to specific embodiments and examples, but the practice of the present invention is not limited to these examples:

preparation of the catalyst

Example 1

Weighing 2.91 g (10 mmol) of commercial nickel nitrate hexahydrate, adding the nickel nitrate hexahydrate into 150mL of deionized water, stirring and dissolving the nickel nitrate in a 500 mL round-bottom flask, weighing 40 g of 3A molecular sieve, adding the molecular sieve into the solution, and fully stirring the solution for 12 hours until the solution is changed from blue to colorless, namely finishing ion exchange. And (3) filtering, drying the solid sample at 80 ℃ for 3 h, roasting the solid sample at 400 ℃ for 6 h in a muffle furnace, heating the solid sample to 450 ℃ at 10 ℃/min in a hydrogen atmosphere by using a temperature programming reduction furnace, and reducing the solid sample for 2h at 450 ℃ to obtain the catalyst 3A 0-10.

Example 2

482 mg (2 mmol) of commercially available copper nitrate trihydrate and 2.33 g (8 mmol) of nickel nitrate hexahydrate are weighed and added into 150mL of deionized water, stirred and dissolved in a 500 mL round-bottom flask, 40 g of 3A molecular sieve is weighed and added into the solution, and the solution is fully stirred for 12 hours until the solution becomes colorless, namely the ion exchange is completed. And (3) filtering, drying the solid sample at 80 ℃ for 3 h, roasting the solid sample at 400 ℃ for 6 h in a muffle furnace, heating the solid sample to 450 ℃ at 10 ℃/min in a hydrogen atmosphere by using a temperature programming reduction furnace, and reducing the solid sample for 2h at 450 ℃ to obtain the catalyst 3A 2-8.

Example 3

The same operation as in example 2 was conducted except that 4mmol and 6mmol of copper nitrate and nickel nitrate were contained, respectively, to obtain catalyst 3A 4-6.

Example 4

The operation was carried out as in example 2 except that 6mmol and 4mmol of copper nitrate and nickel nitrate, respectively, were used to obtain catalyst 3A 6-4.

Example 5

The operation was carried out in the same manner as in example 2 except that copper nitrate and nickel nitrate were contained in an amount of 8mmol and 2mmol, respectively, to obtain catalyst 3A 8-2.

Example 6

The operation was carried out in the same manner as in example 1 except that 10 mmol of copper nitrate was used in place of nickel nitrate to obtain catalyst 3A 10-0.

Example 7

Reference examples 1-6 were run except that the 3A molecular sieve was changed to 4A or 5A molecular sieve to give 4A6-4 and 5A6-4 catalysts, respectively.

Preparation of N-methyl p-methoxyaniline

Examples 8 to 28

7g (about 10 mL) of the catalyst prepared in examples 1-7 was weighed, charged to a φ 8mm fixed bed reactor, purged with nitrogen and warmed over 2h, and the feed was started after reaching temperature. After the start of the sampling, the qualitative and quantitative analysis was carried out using an Agilent 5977A/7890B GC-MS gas phase mass spectrometer and Agilent 7890A (30 m.times.0.25 mm. times.0.33 μm capillary column, hydrogen flame ion detector), and Table 1 shows the instantaneous conversion and selectivity for 24 h of the reaction of each example under different conditions. From the data in Table 1, it can be seen that 7g of 3A6-4 catalyst had a reaction temperature of 300 ℃ and N₂Volume space velocity 480 h^-1Alcohol amine ratio of 10:1, and volume airspeed of raw material of 1.0 h^-1Under the condition of (1), the conversion rate is 84 percent and the selectivity of the p-methyl p-anisidine is 76 percent when the reactor is operated for 24 hours.

TABLE 1

According to the invention, p-methoxyaniline and methanol are used as raw materials, a molecular sieve is loaded with a copper-nickel catalyst, the high-efficiency preparation of N-methyl-p-methoxyaniline is realized on a fixed bed continuous flow reactor, and the whole process is economic, cheap and environment-friendly; the catalysts used can be prepared simply and inexpensively and have high catalytic activity; the reaction condition is mild, the catalyst has good selectivity and stable performance, and has wide prospect of industrial production.

Claims

1. A method for preparing N-methyl-p-methoxyaniline is characterized in that p-methoxyaniline and methanol are used as reaction raw materials, a molecular sieve loaded active component is used as a catalyst, and the reaction temperature is 150-350 ℃ and the liquid volume space velocity is 0.1-2.0 h^-1、N₂Reacting in a fixed bed continuous flow reactor under the condition of serving as a carrier gas to obtain N-methyl p-anisidine; the active components are Cu and Ni, and the content of the active components is 0.01-30 wt% of the mass of the catalyst; the molecular sieve is one of 3A, 4A and 5A molecular sieves;

the catalyst is prepared by the following method: adding a molecular sieve into a water solution of soluble salt containing an active component, stirring for 5-24 hours at room temperature for ion exchange, then drying for 1-5 hours at 50-180 ℃, roasting for 5-15 hours at 200-800 ℃, and reducing for 1-5 hours at 200-800 ℃ by using hydrogen to obtain the catalyst;

the molar ratio of the methanol to the p-anisidine is 0.8: 1-20: 1; the carrier gas N₂The volume space velocity is 100-600h^-1(ii) a The soluble salt is nitrate or chloride of the active component.