阅读说明：本技术 一种合成3,5-二氯苯胺用催化剂及其制备方法和应用 (Catalyst for synthesizing 3, 5-dichloroaniline and preparation method and application thereof ) 是由 颜攀敦 陈丹 张洁兰 张宇 李小安 高武 李岳锋 万克柔 曾永康 于 2019-09-27 设计创作，主要内容包括：本发明公开了一种合成3,5-二氯苯胺用催化剂,包括硫酸钡载体,Pd和助剂金属,助剂金属为Mn、Fe、Co、Cu或Zn。此外,本发明还提供一种该催化剂的制备方法以及应用该催化剂催化3,5-二氯硝基苯加氢合成3,5-二氯苯胺的方法。本发明的催化剂原料成本低、催化活性高、选择性好,用于催化合成3,5-二氯苯胺时,无需添加脱氯剂,原料的转化率达100％,脱氯率在0.04％以下。采用本发明的方法制备的催化剂,活性金属粒子和载体结合更加牢固,更加高度分散和均匀,在催化3,5-二氯硝基苯加氢合成3,5-二氯苯胺反应中具有很好的选择性,大幅降低脱氯率。(The invention discloses a catalyst for synthesizing 3, 5-dichloroaniline, which comprises a barium sulfate carrier, Pd and an auxiliary metal, wherein the auxiliary metal is Mn, Fe, Co, Cu or Zn. In addition, the invention also provides a preparation method of the catalyst and a method for synthesizing 3, 5-dichloroaniline by catalyzing 3, 5-dichloronitrobenzene to hydrogenate by using the catalyst. The catalyst has the advantages of low cost of raw materials, high catalytic activity and good selectivity, and when the catalyst is used for catalytically synthesizing 3, 5-dichloroaniline, dechlorination agent is not required to be added, the conversion rate of the raw materials reaches 100%, and the dechlorination rate is below 0.04%. The catalyst prepared by the method has the advantages that the active metal particles are combined with the carrier more firmly and are dispersed and uniform to a higher degree, the selectivity is good in the reaction of catalyzing 3, 5-dichloronitrobenzene to synthesize 3, 5-dichloroaniline, and the dechlorination rate is greatly reduced.)

1. The catalyst for synthesizing 3, 5-dichloroaniline is characterized by comprising a barium sulfate carrier, Pd and an auxiliary metal, wherein the Pd and the auxiliary metal are loaded on the barium sulfate carrier, the mass percentage of the Pd in the catalyst is 0.5-2.0%, the mass percentage of the auxiliary metal is 0.2-2.0%, and the auxiliary metal is Mn, Fe, Co, Cu or Zn.

2. The catalyst for synthesizing 3, 5-dichloroaniline according to claim 1, wherein the mass percent of Pd in the catalyst is 1%, the mass percent of the promoter metal is 0.5%, and the promoter metal is Co.

3. A process for the preparation of a catalyst for the synthesis of 3, 5-dichloroaniline according to claim 1, comprising the steps of:

adding a barium sulfate carrier into a boric acid solution, stirring and refluxing for 3-6 h in a water bath at 80-100 ℃, filtering, washing the intercepted matters, drying, adding the dried intercepted matters into a sodium phosphite solution, stirring for 20-24 h at normal temperature, filtering, washing and drying to obtain pretreated barium sulfate;

step two, mixing and pulping the pretreated barium sulfate obtained in the step one with water to obtain barium sulfate slurry;

and step three, mixing a soluble palladium precursor, soluble salt of an auxiliary metal and water, uniformly stirring to obtain a mixture, dropwise adding the mixture into the barium sulfate slurry obtained in the step two within 30-90 min under the stirring condition, controlling the pH of the system to be 7-11 by using an alkali liquor in the dropwise adding process, continuously stirring after dropwise adding is finished, then stirring for 3-5 h at the system temperature of 50-90 ℃, cooling, adding an aqueous solution of a reducing agent, stirring for 30-60 min, filtering, washing the intercepted matter, and drying to obtain the catalyst for synthesizing 3, 5-dichloroaniline.

4. The method according to claim 3, wherein the boric acid in the boric acid solution in the first step is 2-25% by mass; in the step one, the mass percentage of the sodium phosphite in the sodium phosphite solution is 5-30%.

5. The method of claim 3, wherein the stirring in step three is continued for 30-60 min.

6. The method of claim 3, wherein the soluble palladium precursor in step three is chloropalladic acid, palladium chloride or sodium chloropalladite, and the soluble salt of the promoter metal is a nitrate of the promoter metal or a chloride of the promoter metal.

7. The method according to claim 3, wherein the alkali solution in step three is sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution or potassium hydroxide solution.

8. The method according to claim 3, wherein the mass of the reducing agent in the third step is 3 to 6 times of the sum of the mass of Pd in the soluble palladium precursor and the mass of the auxiliary metal in the soluble salt of the auxiliary metal, and the reducing agent is sodium borohydride or potassium borohydride.

9. The method for synthesizing 3, 5-dichloroaniline by catalyzing 3, 5-dichloronitrobenzene hydrogenation by using the catalyst according to claim 1 is characterized by comprising the steps of adding 3, 5-dichloronitrobenzene, methanol and the catalyst into a high-pressure reactor, and introducing hydrogen to react, wherein the reaction pressure is 1.2MPa, the reaction temperature is 85 ℃, and the reaction time is 60 min; the mass of the methanol is 8 times of that of the 3, 5-dichloronitrobenzene, and the mass of the catalyst is 1 percent of that of the 3, 5-dichloronitrobenzene.

Technical Field

The invention belongs to the technical field of noble metal catalysts, and particularly relates to a catalyst for synthesizing 3, 5-dichloroaniline, and a preparation method and application thereof.

Background

3, 5-dichloroaniline is an important intermediate of pesticide, medicine, dye and pigment, and is widely applied to synthesis of medicine, dye and plant growth promoter. Among them, the increase of the output of the agricultural bactericide of the cyclohexanediamine makes the 3, 5-dichloroaniline have a tendency of short supply and demand. At present, the synthesis method of 3, 5-dichloroaniline mainly comprises the following steps:

(1) the electrolytic reduction method is restricted in research stage due to factors such as electrode material, equipment and cost, and the process route can not realize industrial production.

(2) The chemical reduction method of iron powder can generate more waste water, is very difficult to treat and has serious environmental pollution, and the sodium sulfide reduction method has high cost and can not obtain ideal yield.

(3) The 1,3, 5-trichlorobenzene ammonolysis method is published as 2017, 5 and 31, and Chinese patent document with application number of 201611235021.7 discloses a synthetic method for obtaining 3, 5-dichloroaniline by ammonolysis of 1,3, 5-trichlorobenzene under the catalysis of transition metal, wherein the method is simple to operate and short in reaction steps, but has the problem of low yield (less than 93%).

(4) In order to avoid the problem of environmental pollution, people focus on researching an environment-friendly catalytic hydrogenation reduction method, but the process also has the problem of dechlorination while hydrogenation. The Kyasu et al (3, 5-dichloroaniline synthesized by pentachloronitrobenzene catalytic hydrogenation) of Nanjing industry university uses pentachloronitrobenzene as a raw material to prepare 3, 5-dichloroaniline through catalytic hydrogenation, and uses 5% palladium-carbon as a catalyst under optimized reaction conditions, so that the conversion rate of the raw material can reach 99%, but the selectivity is only 95%. The published date is 6/23/2004, and chinese patent application No. 02148509.7 discloses that when Pd and Pt/CNT (carbon nano-tube) are used as catalyst for catalytic hydrogenation, the dehalogenation rate is reduced to 0.1%, but because the cost of carbon nano-tube is too high, the industrial production can not be realized. In addition, other documents can achieve the effect of low dechlorination rate by adding chemical reagents such as dechlorination inhibitors, ethanolamine, morpholine and the like into the reaction system, but after the dechlorination agents are added, the reaction rate is greatly reduced and certain difficulty is caused in product separation.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a catalyst for synthesizing 3, 5-dichloroaniline, and a preparation method and an application thereof, aiming at the defects of the prior art. The catalyst has low cost of raw materials, high catalytic activity and good selectivity, and when the catalyst is used for catalytically synthesizing 3, 5-dichloroaniline, a dechlorinating agent is not required to be added, the conversion rate of the raw materials reaches 100%, and the dechlorinating rate is below 0.04%. The catalyst for synthesizing 3, 5-dichloroaniline, prepared by the preparation method, has the advantages that the combination of active metal particles and a carrier is firmer, the active metal particles are more highly dispersed and uniform, the selectivity is good in the reaction of catalyzing 3, 5-dichloronitrobenzene to synthesize 3, 5-dichloroaniline, and the dechlorination rate of the hydrogenation reaction is greatly reduced.

In order to solve the technical problems, the invention adopts the technical scheme that: the catalyst for synthesizing 3, 5-dichloroaniline is characterized by comprising a barium sulfate carrier, Pd and an auxiliary metal, wherein the Pd and the auxiliary metal are loaded on the barium sulfate carrier, the mass percentage of the Pd in the catalyst is 0.5-2.0%, the mass percentage of the auxiliary metal is 0.2-2.0%, and the auxiliary metal is Mn, Fe, Co, Cu or Zn.

The catalyst for synthesizing 3, 5-dichloroaniline is characterized in that in the catalyst, the mass percent of Pd is 1%, the mass percent of the auxiliary metal is 0.5%, and the auxiliary metal is Co.

In addition, the invention also provides a method for preparing the catalyst for synthesizing 3, 5-dichloroaniline, which is characterized by comprising the following steps:

adding a barium sulfate carrier into a boric acid solution, stirring and refluxing for 3-6 h in a water bath at 80-100 ℃, filtering, washing the intercepted matters, drying, adding the dried intercepted matters into a sodium phosphite solution, stirring for 20-24 h at normal temperature, filtering, washing and drying to obtain pretreated barium sulfate;

step two, mixing and pulping the pretreated barium sulfate obtained in the step one with water to obtain barium sulfate slurry;

and step three, mixing a soluble palladium precursor, soluble salt of an auxiliary metal and water, uniformly stirring to obtain a mixture, dropwise adding the mixture into the barium sulfate slurry obtained in the step two within 30-90 min under the stirring condition, controlling the pH of the system to be 7-11 by using an alkali liquor in the dropwise adding process, continuously stirring after dropwise adding is finished, then stirring for 3-5 h at the system temperature of 50-90 ℃, cooling, adding an aqueous solution of a reducing agent, stirring for 30-60 min, filtering, washing the intercepted matter, and drying to obtain the catalyst for synthesizing 3, 5-dichloroaniline.

The method is characterized in that in the step one, the mass percentage of boric acid in the boric acid solution is 2-25%; in the step one, the mass percentage of the sodium phosphite in the sodium phosphite solution is 5-30%.

The method is characterized in that the time for continuously stirring in the third step is 30-60 min.

The method is characterized in that the soluble palladium precursor in the third step is chloropalladic acid, palladium chloride or sodium chloropalladite, and the soluble salt of the auxiliary metal is nitrate of the auxiliary metal or chloride of the auxiliary metal.

The method is characterized in that the alkali liquor in the third step is sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution or potassium hydroxide solution.

The method is characterized in that the mass of the reducing agent in the third step is 3-6 times of the sum of the mass of Pd in the soluble palladium precursor and the mass of the auxiliary metal in the soluble salt of the auxiliary metal, and the reducing agent is sodium borohydride or potassium borohydride.

Furthermore, the invention also provides a method for synthesizing 3, 5-dichloroaniline by catalyzing 3, 5-dichloronitrobenzene to hydrogenate and applying the catalyst, which is characterized by comprising the steps of adding 3, 5-dichloronitrobenzene, methanol and the catalyst into a high-pressure reactor, and introducing hydrogen to react, wherein the reaction pressure is 1.2MPa, the reaction temperature is 85 ℃, and the reaction time is 60 min; the mass of the methanol is 8 times of that of the 3, 5-dichloronitrobenzene, and the mass of the catalyst is 1 percent of that of the 3, 5-dichloronitrobenzene.

Compared with the prior art, the invention has the following advantages:

1. the catalyst for synthesizing 3, 5-dichloroaniline has the advantages of low raw material cost, high catalytic activity and good selectivity, and when the catalyst is used for catalytically synthesizing 3, 5-dichloroaniline, no dechlorinating agent is needed to be added, the conversion rate of the raw materials reaches 100%, and the dechlorinating rate is below 0.04%.

2. The catalyst for synthesizing 3, 5-dichloroaniline of the invention has barium sulfate as a carrier, Pd and an auxiliary metal as metal components, and because of the electronic effect of the auxiliary metal in the catalyst, the outer layer orbit of Pd atom has more electron distribution, which is beneficial to the adsorption of nitrogen atom with positive charge in nitro group, and greatly improves the activity of the catalyst.

3. In the preparation method, the carrier is barium sulfate pretreated by boric acid and sodium phosphite, the method for loading Pd and the auxiliary metal comprises the steps of dropwise adding, continuously stirring and stirring at the temperature of 50-90 ℃ for 3-5 h, and the prepared catalyst has strong adsorption capacity on nitrogen atoms with positive charges in nitro groups, high catalytic reaction selectivity and low dechlorination rate.

4. The invention adopts boric acid and sodium phosphite to pretreat barium sulfate, and boron atoms are doped into the barium sulfate to interact with Pd, so that the selectivity of an active component Pd is higher.

5. The invention adopts the modes of dripping, continuously stirring and stirring at the temperature of 50-90 ℃ for 3-5 h to load Pd and the auxiliary metal, the initial formation of crystal nucleus occurs at normal temperature, the combination of active metal particles and a carrier is firmer under the action of high temperature, the active metal particles and the carrier are more highly dispersed and uniform, and the electron effect of the auxiliary metal in the catalyst ensures that the outer layer orbit of palladium atoms has more electron distribution, thereby being more beneficial to the adsorption of nitrogen atoms with positive charges in nitro groups.

6. According to the invention, the preferable reducing agent is sodium borohydride or potassium borohydride, and the preferable quality of the reducing agent is 3-6 times of the sum of the quality of Pd in the soluble palladium precursor and the quality of the auxiliary metal in the soluble salt of the auxiliary metal, so that the interaction between the boron atom doped into the barium sulfate carrier and the active component Pd is favorably improved, the selectivity of the catalyst is further improved, and the dechlorination rate is reduced.

7. The catalyst for synthesizing 3, 5-dichloroaniline has the advantages of simple preparation method, easy operation, easy mass production and low production cost.

The technical solution of the present invention is further described in detail with reference to the following examples.

Detailed Description