CN1629132A - Method for producing diphenylamine by aniline liquid-phase condensation and deamination coupling - Google Patents

Abstract

The invention provides a method of coupling condensation reaction and deamination to produce diphenylamine, so as to increase the one-pass conversion rate of aniline, reduce the energy consumption required for the separation of unreacted aniline, improve the catalyst utilization rate and the production capacity of the device, thereby reducing the production capacity of diphenylamine. Cost of production. The method has the characteristics of simple device, easy operation and control, and the like. Among them, the condensation reaction and deamination coupling device adopts 2~N fixed bed reactors connected in series, and each reactor is filled with beta zeolite molecular sieve catalyst, and the top of the reactor is equipped with a gas-liquid separator and a reflux condenser, a gas-liquid separator Equipped with a liquid level display and control system, the operating pressure of each reactor is controlled at 1.5-3.0MPa, the reaction temperature is controlled at 260-400°C, and the space velocity of the raw material aniline is controlled at 0.1-2.0 g/g catalyst·hour .

Description

Method for producing diphenylamine by coupling liquid-phase condensation of aniline and deamination

technical field

The invention relates to the synthesis of organic compounds, in particular to a method for producing diphenylamine using the coupled technology of aniline liquid phase condensation and deamination.

Background technique

Diphenylamine, also known as N-phenylaniline, has a molecular formula of C ₁₂ H ₁₁ N. It is an important fine organic chemical raw material with a wide range of uses, mainly used in rubber additives, explosive stabilizers, medicine, dyes and other industries. As rubber additives, diphenylamine anti-aging agents have good anti-thermal oxygen and anti-bending effects, and also have certain protective effects on metal aging and ozone cracking; as explosive stabilizers, diphenylamine itself and its degradation products It is a good stabilizer and propellant for explosives; in the dye industry, it is mainly used to synthesize acid yellow G, acid IV, sulfur brilliant blue and other dyes; in the pharmaceutical industry, it is mainly used to prepare phenothiazines, and further synthesize insect repellants and insecticides etc.; in addition, diphenylamine is also used as an additive for refining metals, for the preparation of pesticides and other organic compounds, and its derivatives (such as isopropoxy diphenylamine, mono- or diheptyl diphenylamine, hydroxydiphenylamine, hydroxyl Ammoniadiphenylamine) is widely used as an antioxidant in the rubber and plastic industries.

There are nearly 20 kinds of diphenylamine synthesis routes reported in the literature, such as cyclohexylamine method, cyclohexylamine method, cyclohexyleneaniline method, dicyclohexylamine method, phenylene method, cyclohexylaniline method, aniline iodine method, etc. Thermal reaction method, aromatic amine deamination method, etc. However, most of them are of little industrial value. At present, the methods for industrialization or industrialization prospects mainly include aniline condensation method, aniline phenol condensation method and aniline cyclohexanone condensation method. Among them, the aniline condensation method is divided into gas-phase condensation and liquid-phase condensation. Gas-phase condensation requires the raw materials to be preheated and vaporized before the reaction, and the reaction temperature is relatively high. Active; the liquid phase condensation method does not need to gasify the raw materials, and the reaction temperature is low, which overcomes the disadvantages of high energy consumption and easy coking in the gas phase condensation method. The catalyst has a long service life and has obvious advantages.

The reaction of aniline condensation to prepare diphenylamine is a reversible exothermic reaction:

In industry, the reaction pressure is controlled at 2.0-2.5MPa, and the reaction temperature is 320-350°C. Due to the limitation of chemical balance, the single-pass conversion rate of aniline can generally only be below 25%, which is equivalent to the aniline raw material needs of 3-4 times the amount of diphenylamine products. After rectification, separation and recycling, the burden on the subsequent separation process is very heavy, and the energy consumption is very high.

Although increasing the temperature and prolonging the residence time are effective ways to increase the conversion rate, for reversible exothermic reactions, too high a temperature will affect the reaction equilibrium conversion rate, and the selectivity will also decrease. At the same time, in order to maintain the pressure of the liquid phase condensation system, it must increase; the residence time is prolonged, while the conversion rate is increased, the production capacity of the catalyst will decrease. Due to the high price of the catalyst, the service life is only one year, and it needs to be regenerated once in about three months, and the production capacity of the catalyst will decrease. It is bound to increase the cost occupied by the catalyst. Therefore, it is very necessary to seek new ways to strengthen the aniline condensation reaction process and increase the single-pass conversion rate of aniline to increase the production capacity of the device and reduce energy consumption and production costs.

According to the principle of chemical equilibrium, if ammonia, one of the products generated by the condensation reaction of aniline, is removed from the reaction system in time, the chemical equilibrium will shift to the direction of producing diphenylamine. The less ammonia content in the reaction system, the higher the conversion rate of aniline when the reaction reaches equilibrium, and the more the amount of product diphenylamine. At the same time, the ammonia content in the reaction system will also affect the reaction rate, and the removal of ammonia is beneficial to the acceleration of the aniline condensation reaction.

For the aniline liquid-phase condensation reaction, the raw material aniline and the product diphenylamine are in the liquid phase, and the by-product ammonia escapes from the liquid phase to realize the separation of ammonia. Therefore, as long as the deamination is increased in the aniline condensation reaction device The equipment can couple the aniline liquid-phase condensation and deamination, and the condensation reaction is accompanied by deamination, reducing the ammonia content in the reaction system, thereby increasing the conversion rate of the aniline condensation reaction. The ideal aniline condensation-deamination coupling process should be a coupling of continuous condensation reaction and deamination (as shown in Figure 1), which requires the use of a horizontal reactor with a gas phase space on the upper part. Such a continuous process can also be equivalent to a multi-stage coupling process in series (as shown in Figure 2), as long as the number of stages in series is large enough, the effects of the two are the same.

Contents of the invention

The object of the present invention is to provide a method for coupling condensation reaction and deamination to produce diphenylamine for the aniline liquid-phase condensation reaction process, so as to improve the single-pass conversion rate of aniline, reduce the energy consumption required for separating unreacted aniline, and improve catalyst utilization. Rate and device production capacity, thereby reducing the production cost of diphenylamine. The method has the characteristics of simple device, easy operation and control, and the like.

The object of the present invention can be achieved through the following measures:

The condensation reaction and deamination coupling device of the present invention adopts 2 to N sets (N is generally below 10, preferably 3 to 4) fixed bed reactors connected in series, each reactor is equipped with a beta zeolite molecular sieve catalyst, and the top of the reactor is equipped with Gas-liquid separator and reflux condenser, the gas-liquid separator is equipped with a liquid level display and control system. The operating pressure of each reactor is controlled at 1.5-3.0MPa, preferably between 2.0-2.5MPa; the reaction temperature is controlled at 260-400°C, preferably between 300-350°C; the space velocity of the raw material aniline is added It is controlled at 0.1-2.0 g/g catalyst·hour, preferably between 0.2-0.8 g/g catalyst·hour. The aniline raw material is metered with a metering pump and pressurized to the reaction pressure, preheated to the reaction temperature, sent into the bottom of the first reactor, and passed through the catalyst bed in the reactor from bottom to top. When the reaction mixture reaches the gas-liquid separator at the top of the reactor, the ammonia gas is separated from the liquid phase mixture, and after passing through the reflux condenser at the top of the reactor to condense and recover aniline and diphenylamine, it leaves the reaction system and goes to the ammonia gas recovery system to obtain liquid ammonia as a by-product. In order to maintain the normal operation of production, the liquid level of the mixture of aniline and diphenylamine in the gas-liquid separator needs to be kept stable by the operation of the control system. The reaction mixture after deamination enters the second reactor, and then enters the subsequent 3rd to N reactors sequentially after deamination to carry out condensation reaction and deamination. The reaction mixture from the last reactor enters subsequent processes such as deamination, deaniline component removal, aniline separation, light component removal and diphenylamine product refinement, and finally obtains diphenylamine product.

For the series aniline condensation reactor system, equal-volume reactors can be used in series, such as using 3-4 fixed-bed reactors in series, and each reactor can be filled with the same amount of catalyst. The advantage is that in such a system , the flow direction of the reaction material can be changed according to the usage of the catalyst. When the catalyst has been used for 2 to 3 months, the catalyst activity in the reactors will decline as a whole, but the catalyst activity in the rear reactors is relatively good. The first flow, and finally the diphenylamine containing unreacted aniline leaves the first reactor and enters the separation system. Such switching operation can prolong the service life of the catalyst and reduce the times of catalyst regeneration.

When the raw material of aniline passes through 1~N fixed-bed reactors of the same volume successively, the concentration of aniline in the reactor will gradually decrease in the order of 1, 2 to N, the reaction speed will slow down successively, and the diphenylamine produced will also decrease successively. The amount of ammonia removed by the reactor decreases simultaneously. In order to fully reflect the effect of deamination on improving the reaction speed, aniline conversion rate and diphenylamine production, the condensation-deamination coupled reaction system can be connected in series with reactors of different volumes, and in the series of 1, 2 to N fixed bed reactors The loaded catalysts can be sequentially increased according to the multiple of 2 ^N-1 . Such a combination of reactors strengthens the effect of deamination on the condensation reaction, but cannot switch the reaction materials in reverse flow, which affects the flexibility of production operations.

When the aniline condensation reaction is carried out in the above-mentioned condensation-deamination coupling device to produce diphenylamine, under the same reaction pressure, temperature and space velocity conditions, the single-pass conversion rate of aniline is increased from 20 to 23% to 25 to 30%, and the generated diphenylamine The product volume is increased by 10-30%, the utilization rate of the catalyst and the production capacity of the device are also improved, and the amount of unreacted aniline separation and energy consumption are reduced by 20-30%.

The advantages of the present invention are: the reactor system with gas-liquid separator and reflux condenser in series is adopted to produce diphenylamine according to the coupling method of aniline liquid-phase condensation and deamination, the device is simple, the operation and control are convenient, and aniline The single-pass conversion rate, catalyst utilization rate and device production capacity are significantly improved, the energy consumption of separation is greatly reduced, the production cost is low, and the economic benefit is high.

Description of drawings

Figure 1 is a schematic diagram of the continuous condensation-deamination coupling process.

Fig. 2 is a schematic diagram of a multi-stage series condensation-deamination coupling process.

Detailed ways

In order to further illustrate the present invention, illustrate by example below:

Example one:

Four fixed-bed reactors numbered 1, 2, 3, and 4 were connected in series successively, and 6 grams, 12 grams, 24 grams and 48 grams of beta zeolite molecular sieve catalysts were loaded respectively, and the total loading amount of the catalyst was 90 grams. Control the pressure of each reactor to be 2.0MPa and the temperature to be 330°C. After the raw material aniline is pressurized and heated, it is added to the bottom of the first reactor at a speed of 36 g/hour (the space velocity is 0.4 g/g catalyst·hour), followed by Passing through the catalyst beds of the four reactors and exiting from the top of the fourth reactor, samples were taken for analysis of the composition of the reaction mixture. The tops of No. 1, No. 2 and No. 3 reactors are respectively equipped with reflux condensers and valves. When the valves are opened to a certain degree, the deamination can be stabilized while the aniline condensation reaction is carried out. The conversion rates of aniline obtained under the deamination and non-deamination operation forms were 29.3% and 25.1% respectively. It can be seen that the conversion rate of aniline was increased by 4.2% due to the coupling of deamination and condensation reaction.

Example two:

Adopt the same device as example one, catalyst loading, reaction pressure and temperature are also identical with example one. Raw material aniline joins in the reaction system with the speed of 54 grams/hour (space velocity is 0.6 gram/gram catalyst hour), and the aniline conversion obtained under deamination and non-deamination two kinds of operation forms is respectively 18.4% and 23.8%, it can be seen that the conversion rate of aniline has increased by 5.4% because of the coupled deamination and condensation reaction.

Comparing the results of Example 1 and Example 2, it can be seen that, when the aniline conversion rate is low, deamination is more beneficial to the improvement of the conversion rate.

Example three:

Two fixed-bed reactors filled with 5250 kg of beta zeolite molecular sieve catalysts are connected in series, and the top of each reactor is equipped with a gas-liquid separator, a reflux condenser and a liquid level control system. Control the operating pressure and temperature in the reactor to be 2.0MPa and 320°C respectively. After pressurized and heated, the raw material aniline is added to the first reactor at a rate of 2950 kg/hour (the space velocity is 0.28 g/g catalyst·hour). The bottom, after passing through the catalyst beds of the two reactors, leaves the reaction system from the top of the second reactor. According to the analysis and measurement, the aniline conversion rates under deamination and non-deamination operation conditions are 26.6% and 24.5% respectively, and the coupling of deamination and condensation makes the aniline conversion rate increase by 2.1%.

Example four:

Three fixed-bed reactors filled with 5100 kg of zeolite beta molecular sieve catalysts are connected in series, and a gas-liquid separator, a reflux condenser and a liquid level control system are installed on the top of each reactor. Control the operating pressure and temperature in the reactor to be 2.0MPa and 320°C respectively. After pressurized and heated, the raw material aniline is added to the first reactor at a speed of 4300 kg/hour (the space velocity is 0.28 g/g catalyst·hour). The bottom, after passing through the catalyst beds of the three reactors, leaves the reaction system from the top of the third reactor. According to the analysis and measurement, the aniline conversion rates under the deamination and non-deamination operation conditions are 28.5% and 24.8%, respectively, and the coupling of deamination and condensation makes the aniline conversion rate increase by 3.7%.

Comparing the results of Example 3 and Example 4, it can be seen that the number of reactors connected in series increases, and the removal of ammonia generated by the condensation of aniline is more timely, which is beneficial to improving the conversion rate of aniline.

Claims (7)

1. aniline liquid phase condensation and deamination are coupled and produce the method for pentanoic, wherein condensation reaction adopts 2～N platform fixed-bed reactor to connect with the deamination coupling device, be filled with beta-zeolite molecular sieve catalyst in every reactor, the top of reactor is provided with gas-liquid separator and reflux exchanger, gas-liquid separator is equipped with liquid level to show and Controlling System, the working pressure of every reactor all is controlled at 1.5～3.0MPa, temperature of reaction is controlled at 260～400 ℃, and the air speed that adds raw material aniline is controlled at 0.1～2.0 gram/gram catalyzer hour.

2. the method that pentanoic is produced in aniline liquid phase according to claim 1 condensation and deamination coupling is characterized in that adopting 3～4 fixed-bed reactor to connect, and every reactor can load the catalyzer of same amount.

3. the method that pentanoic is produced in the coupling of aniline liquid phase according to claim 1 condensation and deamination is characterized in that placed in-linely 1,2, and the catalytic amount that loads in～N platform the fixed-bed reactor can increase successively according to the multiple of 2N-1.

4. according to the method for claim 1 or 3 described aniline liquid phase condensations and deamination coupling production pentanoic, it is characterized in that N is generally below 10.

5. the method that pentanoic is produced in aniline liquid phase according to claim 1 condensation and deamination coupling, the working pressure that it is characterized in that reactor is between 2.0～2.5MPa.

6. the method that pentanoic is produced in aniline liquid phase according to claim 1 condensation and deamination coupling, the service temperature that it is characterized in that reactor is between 300～350 ℃.

7. the method that pentanoic is produced in the coupling of aniline liquid phase according to claim 1 condensation and deamination, the air speed that it is characterized in that reaction unit is between 0.2～0.8 gram/gram catalyzer hour.

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