CN111116407B

CN111116407B - Method for preparing DCB reducing substance by continuous catalytic hydrogenation reduction

Info

Publication number: CN111116407B
Application number: CN201911289950.XA
Authority: CN
Inventors: 王晓辉; 赵伟; 仇文仲; 赵磊; 苏天伟
Original assignee: Zhejiang Qinyan Technology Co ltd
Current assignee: Zhejiang Qinyan Technology Co ltd
Priority date: 2019-12-16
Filing date: 2019-12-16
Publication date: 2022-02-22
Anticipated expiration: 2039-12-16
Also published as: CN111116407A

Abstract

A method for preparing DCB reducing substances by continuous catalytic hydrogenation reduction comprises the following steps: adding ortho-nitrochlorobenzene, toluene, 30% liquid caustic soda, desalted water and a Pt/C catalyst into three serially connected kettle type continuous reactors until all the reactors do not absorb hydrogen, and finishing the first-stage intermittent reaction; opening overflow discharge valves of the three kettle type reactors, and simultaneously pumping ortho-nitrochlorobenzene, toluene, 30% liquid caustic soda and desalted water into the first reaction kettle in proportion by using a metering pump; continuously introducing hydrogen to catalyze and hydrogenate to prepare the DCB reducing substance 2, 2-dichlorohydrazobenzene. The method can effectively reduce the loss of the catalyst caused by frequent filtration in the intermittent reaction process, realize the internal recycle of the catalyst and prolong the service life of the catalyst; meanwhile, the reaction kettle has small volume, good reaction stability, low dechlorination of products, high selectivity and less by-products; in addition, the exhaust emission in the continuous reaction is greatly reduced, and the environmental pollution is greatly reduced.

Description

Method for preparing DCB reducing substance by continuous catalytic hydrogenation reduction

Technical Field

The invention relates to the field of organic chemical synthesis, in particular to a method for preparing a DCB reducing substance (2, 2-dichlorohydrazobenzene) by continuous catalytic hydrogenation reduction.

Background

The chemical name of DCB is 3,3' -dichlorobenzidine, which is an important yellow organic pigment intermediate, and pigment varieties such as C.I. pigment yellow 12, 13, 14, 17, 56, 63, 83, 87, 106, 124, 127, 152, 170, 171, 172, 174, 176, 188, orange 13, 14 and the like can be synthesized by taking DCB as a diazo component.

The DCB is prepared by using o-nitrochlorobenzene as a raw material and reducing the raw material under an alkaline condition, wherein the reduction method comprises a catalytic hydrogenation method, an electrolytic reduction method and a chemical reduction method, and the chemical reduction method can be divided into a zinc powder method, a formaldehyde method, a sodium hydrosulfide method, a hydrazine hydrate method and a formic acid method. At present, the catalytic hydrogenation method is mainly used, the conditions are simple, the treatment is convenient, and the three-waste pollution is very small. Now, the most widely used catalytic hydrogenation method is briefly described as follows: the reaction takes ortho-nitrochlorobenzene as a raw material, an organic solvent and a catalyst, under a certain alkaline condition, under a certain hydrogen pressure and a certain temperature, 2 '-dichlorohydrazobenzene is firstly generated, and then transposition and rearrangement are carried out in hydrochloric acid to obtain the 3,3' -dichlorobenzidine hydrochloride.

For the reduction process of DCB, the batch kettle type hydrogenation reduction process is generally adopted at home and abroad at present, and the batch kettle type hydrogenation reduction process has the following problems:

1. the reaction kettle has larger volume, which causes higher equipment investment;

2. a large amount of steam is consumed in the reaction process, and the labor intensity is high;

3. the reaction control is unstable, and the by-product in the reaction is high;

4. a large amount of toluene-containing waste gas is discharged into the air in the reaction, so that the problem of environmental pollution exists.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a catalyst, which can effectively reduce the loss of the catalyst caused by frequent filtration in the intermittent reaction process, realize the internal recycle of the catalyst and prolong the service life of the catalyst; meanwhile, the reaction kettle has small volume, good reaction stability, low dechlorination of products, high selectivity and less by-products; in addition, the exhaust emission in the continuous reaction is greatly reduced, and the environmental pollution is greatly reduced.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for preparing a DCB reduced product by continuous catalytic hydrogenation reduction, comprising: the method is carried out in a reaction system consisting of a 3-stage series kettle type continuous reactor, a gas-liquid separator, a catalyst settling tank and a reaction liquid receiving tank which are sequentially communicated, and specifically comprises the following steps:

(1) batch reaction, preparing substrate for continuous reaction

Adding ortho-nitrochlorobenzene, methylbenzene, 30 percent (mass percentage content) liquid caustic soda, desalted water and 1 percent (mass percentage content) Pt/C catalyst into three serially-connected kettle type continuous reactors, replacing air with nitrogen twice, replacing the nitrogen with hydrogen twice, starting stirring, heating the reaction material to 70-95 ℃, continuously introducing hydrogen, controlling the hydrogen pressure to be 1-1.5MPa, controlling the reaction temperature to be 90-95 ℃, and finishing the first-stage intermittent reaction until all the three reactors do not absorb hydrogen, thereby completing the substrate preparation of the continuous reaction;

(2) continuous reaction, continuous feeding and discharging.

After the reaction in the step (1) is finished, opening overflow discharge valves of three kettle-type reactors, and simultaneously pumping ortho-nitrochlorobenzene, toluene, 30% liquid caustic soda and desalted water into a first reaction kettle (only feeding the materials into the first reaction kettle, enabling the first kettle to enter a second kettle through overflow, enabling the second kettle to enter a third kettle through overflow, and enabling the third kettle to overflow and discharge the materials) by using a metering pump in proportion; continuously introducing hydrogen during the reaction period, controlling the hydrogen pressure in 3 kettle-type reactors to be 1-1.5MPa and the reaction temperature to be 90-95 ℃, and carrying out catalytic hydrogenation to prepare the DCB reducing substance 2, 2-dichlorohydrazobenzene by adopting a continuous hydrogen introduction, continuous feeding and continuous discharging mode;

(3) the DCB reduced matter 2, 2-dichlorohydrazobenzene solution after the reaction flows into a gas-liquid separator from the last reaction kettle, the reaction liquid from the lower opening of the gas-liquid separator enters a catalyst settling tank, the upper layer reduced matter 2, 2-dichlorohydrazobenzene solution enters a reaction liquid receiving tank, the Pt/C catalyst concentrated solution separated from the lower layer is pumped into the first-stage reaction kettle through a metering pump for recycling, and new Pt/C catalyst is added into the first-stage reaction kettle every 6-10 hours in the reaction process to supplement the lost catalyst.

In step (1) of the present invention, o-nitrochlorobenzene: toluene: 30% liquid caustic soda: desalting water: mass ratio of 1% Pt/C catalyst 1: 1-1.2: 0.4-0.5: 0.3-0.4: 0.005-0.01.

In the step (1) of the present invention, 1% (mass percentage) of the Pt/C catalyst means the platinum content in the catalyst.

In the step (2), the feeding speed of the ortho-nitrochlorobenzene is 80-120g/h, the feeding speed of the toluene solvent is 100-150g/h, the feeding speed of the 30% liquid alkali is 35-50g/h, and the feeding speed of the desalted water is 25-40 g/h;

further preferably, the feeding speed of the ortho-nitrochlorobenzene is 90-110g/h, the feeding speed of the toluene solvent is 100-120g/h, the feeding speed of the 30% liquid caustic soda is 38-45g/h, and the feeding speed of the desalted water is 30-35 g/h.

In the step (3), the Pt/C catalyst is 0.3-0.6 g of 1% Pt/C catalyst by mass percent.

The DCB reduced substance solution prepared by the method is detected by liquid chromatography analysis, and the DCB reduced substance 2, 2-dichlorohydrazobenzene is more than or equal to 95 percent, the o-chloroaniline content is less than or equal to 1 percent, and other byproducts are less than or equal to 4 percent.

The chemical reaction equation of the method for preparing the DCB reducing substance by continuous catalytic hydrogenation reduction provided by the invention is as follows:

compared with the prior art, the invention has the following remarkable beneficial effects:

1. when the method is used for preparing the DCB reducing substance by means of continuous hydrogenation, continuous feeding and continuous discharging, the required reaction kettle is small in volume, good in reaction stability, high in selectivity and less in by-products when the DCB reducing substance is prepared by catalytic hydrogenation reduction;

2. the catalyst separated from the lower layer in the catalyst settling tank is pumped into a first-stage (platform) reaction kettle for cyclic utilization through a pump, so that the loss of the catalyst caused by frequent filtration in the intermittent reaction process can be effectively reduced, the internal cyclic utilization of the catalyst is realized, and the service life of the catalyst is prolonged.

3. The exhaust emission in the continuous reaction is greatly reduced, and the problem of environmental pollution is greatly reduced.

Drawings

Figure 1 HPLC profile of the product prepared in the example.

FIG. 2 is a flow chart of a kettle-type continuous catalytic hydrogenation reduction device for DCB reduction.

Detailed Description

The following examples are further illustrative of the present invention, but the present invention is not limited thereto.

Example 1

600g of o-nitrobenzyl chloride, 720g of toluene, 250g of 30% caustic soda liquid, 204g of desalted water and 6g of 1% Pt/C catalyst are respectively added into 3 serially-connected 2L kettle type continuous reactors (which are sequentially divided into a first-stage reaction kettle/reactor, a second-stage reaction kettle/reactor and a third-stage reaction kettle/reactor according to serial connection), air is replaced by nitrogen twice, the nitrogen is replaced by hydrogen twice, stirring is started, the reaction material is heated to 90 ℃, hydrogen is continuously introduced, the hydrogen pressure is controlled to be 1MPa, the reaction temperature is controlled to be 90-95 ℃, until all the 3 reactors react and do not absorb hydrogen, the first-stage intermittent reaction is finished, and the substrate for continuous reaction is prepared;

after the first-step reaction is finished, opening overflow discharge valves of 3 tank reactors, simultaneously pumping ortho-nitrochlorobenzene, toluene, 30% liquid alkali and desalted water into the first reaction tank by a metering pump in proportion, wherein the feed rate of the ortho-nitrochlorobenzene is 100g/h, the feed rate of a toluene solvent is 120g/h, the feed rate of the 30% liquid alkali is 41.7g/h, the feed rate of the desalted water is 34g/h, hydrogen is continuously introduced during the reaction, the hydrogen pressure is controlled to be 1MPa, the reaction temperature is controlled to be 90-95 ℃, and the DCB reducing substance (2, 2-dichlorohydrazobenzene) is prepared by catalytic hydrogenation in a continuous hydrogen introduction, continuous feeding and continuous discharging mode; the DCB reducing substance 2, 2-dichlorohydrazobenzene solution after the reaction flows into a gas-liquid separator from the last stage of reaction kettle, reaction liquid from the lower opening of the gas-liquid separator enters a catalyst settling tank, the upper layer reducing substance 2, 2-dichlorohydrazobenzene solution enters a reaction liquid receiving tank, Pt/C catalyst concentrated solution separated from the lower layer is pumped into the first stage of reaction kettle through a metering pump for recycling, and 0.6g of new 1% Pt/C catalyst is added into the first stage of reaction kettle every 8 hours in the reaction process so as to supplement the lost catalyst.

The total reaction time is 24 hours, samples are taken from the reaction liquid receiving tank at regular time in the reaction process, and liquid chromatography analysis is carried out, wherein specific experimental data are shown in the following table 1:

TABLE 1 sample testing data

Example 2

Respectively adding 600g of o-nitrochlorobenzene, 720g of toluene, 250g of 30% liquid caustic soda, 204g of desalted water and 4g of 1% Pt/C catalyst into 3 serially-connected 2L kettle-type continuous reactors, replacing air with nitrogen twice, replacing nitrogen with hydrogen twice, starting stirring, heating the reaction material to 90 ℃, continuously introducing hydrogen, controlling the hydrogen pressure to be 1.5MPa, controlling the reaction temperature to be 90-95 ℃, and finishing the first-stage intermittent reaction until all the 3 reactors do not absorb hydrogen, thus finishing the substrate preparation of the continuous reaction;

after the first-step reaction is finished, opening overflow discharge valves of 3 tank reactors, simultaneously pumping ortho-nitrochlorobenzene, toluene, 30% liquid alkali and desalted water into the first reaction tank by a metering pump in proportion, wherein the feed rate of the ortho-nitrochlorobenzene is 100g/h, the feed rate of a toluene solvent is 120g/h, the feed rate of the 30% liquid alkali is 41.7g/h, the feed rate of the desalted water is 34g/h, hydrogen is continuously introduced during the reaction, the hydrogen pressure is controlled to be 1MPa, the reaction temperature is controlled to be 90-95 ℃, and the DCB reducing substance (2, 2-dichlorohydrazobenzene) is prepared by catalytic hydrogenation in a continuous hydrogen introduction, continuous feeding and continuous discharging mode; the DCB reducing substance 2, 2-dichlorohydrazobenzene solution after the reaction flows into a gas-liquid separator from the last stage of reaction kettle, reaction liquid from the lower opening of the gas-liquid separator enters a catalyst settling tank, the upper layer reducing substance 2, 2-dichlorohydrazobenzene solution enters a reaction liquid receiving tank, Pt/C catalyst concentrated solution separated from the lower layer is pumped into the first stage of reaction kettle through a metering pump for recycling, and new 0.4g of 1% Pt/C catalyst is added into the first stage of reaction kettle every 8 hours in the reaction process so as to supplement the lost catalyst.

The total reaction time is 24 hours, samples are taken from the reaction liquid receiving tank at regular time in the reaction process, and liquid chromatography analysis is carried out, wherein specific experimental data are shown in the following table 2:

TABLE 2 sample testing data

As shown in fig. 1, HPLC analysis of the product prepared in example 2 showed that the purity of the target product obtained was almost completely higher than that of the standard, which is fully confirmed to be the target product prepared in the present application.

Claims

1. A method for preparing DCB reducing substances by continuous catalytic hydrogenation reduction is characterized by comprising the following steps: the method is carried out in a reaction system consisting of three serially connected kettle type continuous reactors, a gas-liquid separator, a catalyst settling tank and a reaction liquid receiving tank which are sequentially communicated, and specifically comprises the following steps:

(1) batch reaction, preparing substrate for continuous reaction

Adding 600g of o-nitrochlorobenzene, 720g of toluene, 250g of 30% liquid caustic soda, 204g of desalted water and 6g of 1% Pt/C catalyst into three serially-connected 2L kettle-type continuous reactors, replacing air with nitrogen twice, replacing nitrogen with hydrogen twice, starting stirring, heating the reaction material to 90 ℃, continuously introducing hydrogen, controlling the hydrogen pressure to be 1MPa, controlling the reaction temperature to be 90-95 ℃, and finishing the first-stage intermittent reaction until all the three reactors do not absorb hydrogen, and finishing the preparation of substrates for the continuous reaction;

(2) continuous reaction, continuous feeding and discharging

After the reaction in the step (1) is finished, opening overflow discharge valves of three kettle-type reactors, and simultaneously pumping ortho-nitrochlorobenzene, toluene, 30% liquid caustic soda and desalted water into a first reaction kettle in proportion by using a metering pump, wherein the feed speed of the ortho-nitrochlorobenzene is 100g/h, the feed speed of a toluene solvent is 120g/h, the feed speed of the 30% liquid caustic soda is 41.7g/h, and the feed speed of the desalted water is 34 g/h; continuously introducing hydrogen during the reaction period, controlling the hydrogen pressure in the three kettle-type reactors to be 1MPa and the reaction temperature to be 90-95 ℃, and carrying out catalytic hydrogenation to prepare the DCB reducing substance 2, 2-dichlorohydrazobenzene by adopting the modes of continuously introducing hydrogen, continuously feeding and continuously discharging;

(3) the DCB reduced matter 2, 2-dichlorohydrazobenzene solution after the reaction flows into a gas-liquid separator from the last reaction kettle, the reaction liquid from the lower opening of the gas-liquid separator enters a catalyst settling tank, the upper layer reduced matter 2, 2-dichlorohydrazobenzene solution enters a reaction liquid receiving tank, the Pt/C catalyst concentrated solution separated from the lower layer is pumped into the first-stage reaction kettle through a metering pump for recycling, and new 0.6g of 1% Pt/C catalyst is added into the first-stage reaction kettle every 8 hours in the reaction process to supplement the lost catalyst.

2. The method for preparing DCB reducing substance by continuous catalytic hydrogenation reduction according to claim 1, wherein the content of DCB reducing substance 2, 2-dichlorohydrazobenzene is not less than 95%, the content of o-chloroaniline is not more than 1%, and the content of other by-products is not more than 4% by liquid chromatography analysis and detection of the DCB reducing substance solution.

3. The method for preparing DCB reducing substance by continuous catalytic hydrogenation reduction according to claim 1, wherein the chemical reaction equation is as follows:

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