CN108031485B - Method for preparing parachloroaniline through parachloronitrobenzene selective hydrogenation - Google Patents

Method for preparing parachloroaniline through parachloronitrobenzene selective hydrogenation Download PDF

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CN108031485B
CN108031485B CN201711340016.7A CN201711340016A CN108031485B CN 108031485 B CN108031485 B CN 108031485B CN 201711340016 A CN201711340016 A CN 201711340016A CN 108031485 B CN108031485 B CN 108031485B
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tio
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CN108031485A (en
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周继承
王非
张燕吉
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Xiangtan University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
    • B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
    • B01J29/0316—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing iron group metals, noble metals or copper
    • B01J29/0325—Noble metals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
    • C07C209/30—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds
    • C07C209/32—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups
    • C07C209/36—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst
    • C07C209/365—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst by reduction with preservation of halogen-atoms in compounds containing nitro groups and halogen atoms bound to the same carbon skeleton
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions

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Abstract

The invention provides a method for preparing p-chloronitrobenzene by selective hydrogenationThe method for preparing the parachloroaniline comprises the steps of using a catalyst containing platinum and titanium dioxide and catalyzing the parachloronitrobenzene to be selectively hydrogenated under the hydrogen environment and the heating condition to prepare the parachloroaniline, so that the dechlorination side reaction during hydrogenation is greatly reduced, wherein the catalyst is Pt/TiO2The catalyst is SBA-15. The catalyst of the invention shows excellent catalytic activity when being used for catalyzing the selective hydrogenation of p-chloronitrobenzene to prepare p-chloroaniline, has high conversion rate and selectivity which can reach more than 99 percent, and greatly reduces the side reaction of dechlorination. The composite nano-structured catalyst Pt/TiO used in the method provided by the invention2The preparation method of the/SBA-15 is simple, the production period is short, the platinum loading capacity is low, so that the catalyst is low in cost, high-temperature treatment is not needed, and a reducing agent is not needed to be added during preparation. The platinum has good dispersibility and high catalytic activity.

Description

Method for preparing parachloroaniline through parachloronitrobenzene selective hydrogenation
Technical Field
The invention belongs to the field of catalytic hydrogenation, and particularly relates to a method for preparing parachloroaniline through selective hydrogenation of parachloronitrobenzene.
Background
Parachloroaniline is an important organic intermediate and is widely applied to synthesis of dyes, medicines, pesticides and the like. At present, most of parachloroaniline is prepared by parachloronitrobenzene reduction, and reduction methods mainly comprise a metal reduction method, an electrochemical reduction method, a non-hydrogen reducing agent reduction method, a catalytic hydrogenation reduction method and the like, wherein the catalytic hydrogenation reduction method has advanced process and high yield and better meets the requirement of modern chemical engineering on atom economy; the noble metal catalytic hydrogenation method is the main one, and the heterogeneous catalytic reduction method under high temperature and high pressure is mainly adopted in the past, but the dispersity and the catalytic activity of the catalyst are influenced because the microcrystals are easy to gather on the surface of the carrier under high temperature, and the heterogeneous catalysis under low temperature and low pressure gradually attracts the interest of researchers in recent years. The key point of the catalytic hydrogenation method is how to control the selectivity of the reaction and prevent the occurrence of dechlorination side reaction.
There are currently two main approaches: firstly, dechlorination is prevented by adding a dechlorination inhibitor or pre-poisoning a hydrogenation catalyst, and secondly, the aim of dechlorination inhibition is achieved by modifying the hydrogenation catalyst.
For example, patent CN201510129577 discloses a catalytic hydrogenation reaction by using a platinum catalyst and a dechlorination inhibitor, which comprises the steps of firstly carrying out hydrogenation reduction reaction on 2-chloro-6-nitrotoluene as a raw material in the presence or absence of a solvent and in the presence of a hydrogenation catalyst and a dechlorination inhibitor, and filtering a catalyst from a reaction solution at a certain temperature to obtain 3-chloro-2-methylaniline; then carrying out ammonolysis reaction to obtain the product 2, 6-diaminotoluene.
However, the addition of the dechlorination inhibitor can increase secondary pollution and affect the product quality, and the poisoning hydrogenation catalyst can greatly reduce the catalyst activity.
While the modification of hydrogenation catalysts generally involves the following three aspects: (1) the appropriate support and catalyst precursor are selected to tailor the interaction between the metal and the support. (2) Alloying the catalyst active metal with other metals or adding appropriate ions to treat the catalyst; (3) the size of the active metal particles is changed by changing the preparation mode of the catalyst.
For example, patent CN200810183391 provides a catalyst for synthesizing p-chloroaniline by hydrogenation of p-chloronitrobenzene, which comprises active component platinum and support attapulgite. Patent CN201210366514 provides a method for preparing 3, 4-dichloroaniline, which comprises the steps of taking 3, 4-dichloronitrobenzene as a raw material, using no solvent, carrying out catalytic hydrogenation reaction in the presence of a Pt catalyst, wherein the reaction pressure is 1.0-3.0 MPa, and the reaction temperature is 75-120 ℃; the Pt catalyst consists of an active component Pt, a carrier C and an auxiliary agent, wherein the mass percentage of Pt is 0.5-5%, the auxiliary agent is Fe2O3, the mass percentage of the auxiliary agent is 0.05-0.5%, and the balance is C. I.e. wherein a catalyst comprising platinum carbon and iron oxide is used.
The patent CN201310009679 provides a production method for preparing chloroaniline from chloronitrobenzene by a solvent-free method through hydrogenation, wherein the chloronitrobenzene is used as a raw material, reacts with hydrogen at 80-100 ℃ and 0.3-2.5MPa in the presence of a catalyst and an auxiliary agent, and is not added with a solvent, and water is distributed to obtain the chloroaniline after the reaction is finished. The catalyst used therein is a platinum carbon catalyst.
Patent CN2012103303921 provides a method for preparing o-chloroaniline by solvent-free catalytic hydrogenation, which uses o-nitrochlorobenzene as a raw material, wherein a vanadium-added platinum-carbon catalyst is used for catalytic hydrogenation to inhibit dechlorination side reaction. Likewise, patent CN201510128466 provides a method for preparing dichloroaniline by continuous catalytic hydrogenation of dichloronitrobenzene, wherein the hydrogenation is catalyzed by using a catalyst containing platinum carbon plus vanadium or tin to inhibit dechlorination side reactions.
It is believed that the nano platinum catalyst with excellent performance should have the following characteristics in structure: the active component platinum is highly and uniformly dispersed on the surface of the carrier, the platinum loading capacity of the active component is low, the number of exposed atoms on the surface is large, and the specific surface area of the carrier is large. However, there are some problems in the prior art: some preparation methods have harsh preparation conditions, reagents used are not friendly to the environment, the dispersibility of platinum is poor, and the particle size is large. The application aspect requires high catalytic reaction temperature and long reaction time, and has certain limitation on the selective hydrogenation conversion rate and selectivity of the chloronitrobenzene under mild conditions.
In conclusion, the supported platinum-based catalyst has good hydrogenation performance and is commonly used for selective hydrogenation of eneyne, nitryl, aldehyde, ketone and the like; the particle size of the active component platinum, its dispersibility on the support surface, and its interaction with the support all affect the catalytic activity of the catalyst. At present, the common methods for preparing platinum-based catalysts at home and abroad, such as an impregnation method, a sol-gel method, an ion exchange method and the like, have the defects of complex preparation process, easy aggregation of platinum nanoparticles, non-green property and the like, and influence the overall performance of the catalyst. Therefore, the development of a simple and green platinum-based catalyst with good dispersibility, low precious metal loading capacity, high activity and high stability and the provision of an excellent method for preparing p-chloroaniline by selective hydrogenation of p-chloronitrobenzene have important significance.
Disclosure of Invention
Therefore, the invention provides a method for preparing p-chloroaniline by selectively hydrogenating p-chloronitrobenzene, which comprises the steps of using a catalyst containing platinum and titanium dioxide and catalyzing the p-chloronitrobenzene to selectively hydrogenate the p-chloroaniline in a hydrogen environment and under a heating condition, so that the dechlorination side reaction during hydrogenation is greatly reduced, wherein the catalyst is Pt/TiO2The catalyst is SBA-15.
In one specific embodiment, the Pt/TiO is2SBA-15 catalystThe platinum content in the chemical agent is 0.01 to 0.3 wt%, preferably 0.05 to 0.15 wt%, and more preferably 0.08 to 0.10 wt%.
In one specific embodiment, the Pt/TiO is2TiO (treated by spontaneous monolayer dispersion principle) in SBA-15 catalyst2In the form of a thin film, laid flat in single or multiple layers on the support SBA-15, with the active component platinum anchored to the TiO2On the film layer.
In a specific embodiment, anhydrous ethanol is used as a solvent in the selective hydrogenation reaction.
In a specific embodiment, the temperature of the selective hydrogenation is 40 to 90 ℃, preferably 50 to 70 ℃.
In a specific embodiment, the catalyst is TiO2Occupies composite carrier TiO25-20 wt%, preferably 10-15 wt% of the total weight of SBA-15.
In the present invention, platinum and a semiconductor metal oxide TiO2Strong interaction exists between the two to form the composite nano-structure catalyst Pt/TiO2SBA-15; specifically, the nano noble metal platinum and the nano titanium dioxide in the catalyst are cooperatively catalyzed, so that the dosage of the platinum in the catalyst can be reduced to a limit low value.
In a specific embodiment, the catalyst is prepared by first sol-gel processing TiO2Loaded on SBA-15 to obtain one or more layers of nano TiO spread on SBA-152Loading active component platinum onto the composite carrier by adopting a photocatalytic reduction method to obtain the Pt/TiO composite carrier2The catalyst is SBA-15.
In one embodiment, the TiO is2Before loading on the SBA-15, the method also comprises the step of carrying out ultrasonic pretreatment on the SBA-15 by using absolute ethyl alcohol.
In a specific embodiment, the sol-gel method comprises adding butyl titanate into absolute ethyl alcohol containing SBA-15, adding water, continuously stirring to hydrolyze the butyl titanate, heating the hydrolyzed mixture to 35-45 ℃ to form gel, and drying in vacuum at 60-90 DEG CDrying to obtain TiO2the/SBA-15 composite carrier.
In a specific embodiment, the photocatalytic reduction process comprises subjecting TiO to a reduction treatment2Dispersing the/SBA-15 composite carrier in deionized water, adding methanol and chloroplatinic acid solution for ultrasonic impregnation, placing the mixed solution under ultraviolet irradiation, stirring, performing solid-liquid separation, washing with water to neutrality, and drying to obtain the Pt/TiO2SBA-15 catalyst, preferably the mass ratio of methanol to water used in the photocatalytic reduction is 1: 5-15, and the ultraviolet illumination time is 5-20 hours.
The invention has at least the following beneficial effects:
1) the catalyst shows excellent catalytic activity when being used for catalyzing the selective hydrogenation of p-chloronitrobenzene to prepare p-chloroaniline, has very high conversion rate and selectivity which can reach more than 99 percent, and greatly reduces the side reaction of dechlorination.
2) The catalyst has novel structure, and the catalyst has low cost because the consumption of platinum in the catalyst is small. The invention provides a composite nano-structure catalyst Pt/TiO2The preparation method of the/SBA-15 is simple, short in production period, low in platinum loading capacity, free of high-temperature treatment, free of reducing agent during preparation, good in platinum dispersibility and high in catalytic activity.
3) The reaction condition is mild during the catalytic hydrogenation reaction, the reaction time is short, the catalyst and the reaction liquid are easy to separate, and the method has a good application prospect.
4) TiO in the invention2The preparation process of the/SBA-15 composite carrier is simple, the reaction time is short, the solvent is green and pollution-free, high-temperature calcination is not needed, and TiO is used2The surface of the mesoporous silicon material SBA-15 has high dispersity, so that the nano platinum and the nano TiO subsequently loaded on the mesoporous silicon material SBA-15 are ensured2Producing a synergistic catalytic effect.
5) In the present invention, when platinum is supported on the composite carrier, sufficient light is applied to the platinum during the reduction of the photocatalyst, and Pt is added2+Can be totally reduced into Pt0No additional reducing agent needs to be added. Platinum nanoparticles anchored or embedded in the TiO in the catalyst2On the film layer. The catalyst of the invention is prepared from TiO2The Pt nanoparticles are arranged on the SBA-15 carrierThe catalyst is completely and uniformly distributed, the platinum nano-particles have high dispersity and small particle size, so that the catalyst can obtain good selective catalytic hydrogenation effect when the platinum dosage is small.
Drawings
FIG. 1 shows 10% TiO2XRD pattern of the/SBA-15 composite carrier.
FIG. 2 shows 15% TiO2XRD pattern of the/SBA-15 composite carrier.
FIG. 3 is the 0.08% Pt/10% TiO sample prepared in example 22XRD pattern of/SBA-15 catalyst.
FIG. 4 is the 0.1% Pt/10% TiO preparation of example 12XRD pattern of/SBA-15 catalyst.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
Experimental Pt/TiO in the invention2The SBA-15 catalytic selective hydrogenation of p-chloronitrobenzene to prepare p-chloroaniline comprises the following specific steps:
1) taking p-chloronitrobenzene and catalyst in a certain proportion into a reaction kettle, adding a proper amount of solvent, and introducing H2After the air in the reaction kettle is replaced, H is closed2Valve, set reaction temperature and H2And (4) pressure.
2) When the temperature in the kettle reaches the set reaction temperature, introducing H2The reaction was started with the stirring turned on.
3) After the reaction, the reaction mixture was cooled, and an appropriate amount of the reaction mixture was centrifuged to conduct gas chromatography.
Example 1
Adding the mesoporous silicon material SBA-15 into 15mL of absolute ethyl alcohol, and carrying out ultrasonic oscillation for 2h to obtain a mixed solution of the treated SBA-15 and the absolute ethyl alcohol. Under the condition of stirring, 0.5mL of butyl titanate is dropwise added into the mixed solution, and the mixed solution is stirred for 1 hour; slowly add 1mL of water to the mixture, hydrolyze the butyl titanate, and continue stirring for 1h to complete hydrolysis of the butyl titanate. Heating and stirring at 40 deg.C to make the above mixed solution gel. Vacuum drying at 80 deg.C overnight to obtain 10% TiO2/SBA-15 composite carrier (TiO in the composite carrier)2 Content 10 wt%). Take 0.702gTiO2/SBA-15 composite carrier dispersionAdding 10mL of anhydrous methanol into 100mL of deionized water, performing ultrasonic dispersion for 10min, adding 0.1mL of chloroplatinic acid solution, performing ultrasonic dispersion for 20min, placing the solution under ultraviolet light for 12h under the condition of stirring, filtering and washing the obtained solution, and performing vacuum drying at 80 ℃ to obtain Pt/TiO with the Pt mass fraction of 0.1%2SBA-15 catalyst (Pt content 0.1 wt% in catalyst), i.e. 0.1% Pt/10% TiO2/SBA-15。
Example 2
Same as example 1 except that Pt/TiO2The mass fraction of Pt in the SBA-15 is 0.08 percent, namely 0.08 percent of Pt/10 percent of TiO2/SBA-15。
Example 3
Same as example 1 except that Pt/TiO2TiO in SBA-152The mass fraction in the composite carrier is 15 percent, namely 0.1 percent of Pt/15 percent of TiO2/SBA-15。
Example 4
0.1% Pt/10% TiO prepared as described above in example 12The SBA-15 is used for catalyzing the p-chloronitrobenzene hydrogenation reaction. 0.401g of p-chloronitrobenzene and 0.1g of 0.1 percent Pt/10 percent TiO are taken2SBA-15 and 20mL absolute ethyl alcohol are put into a high-pressure reaction kettle, and H is introduced2After the air in the reaction kettle is replaced, H is closed2A valve, when the temperature in the kettle reaches 70 ℃ reaction temperature, H is introduced2After the reaction was completed, the reaction was cooled, and 10mL of the reaction solution was centrifuged and analyzed by gas chromatography. The conversion rate of p-chloronitrobenzene is 100 percent, and the selectivity of p-chloroaniline is 98.44 percent.
Example 5
The catalyst prepared in example 1 was added with 0.1% Pt/10% TiO as in example 42SBA-150.1 g, p-chloronitrobenzene 0.401g and absolute ethyl alcohol 20mL react for 0.5h at 70 ℃. The conversion rate of p-chloronitrobenzene is 98.32 percent, and the selectivity of p-chloroaniline is 98.60 percent.
Example 6
The catalyst prepared in example 1 was added with 0.1% Pt/10% TiO as in example 42SBA-150.1 g, p-chloronitrobenzene 0.401g and absolute ethyl alcohol 20mL react for 1.5h at 50 ℃. Conversion rate of p-chloronitrobenzene99.36%, and a p-chloroaniline selectivity of 99.13%.
Example 7
The catalyst prepared in example 2 was added with 0.08% Pt/10% TiO as in example 42SBA-150.1 g, p-chloronitrobenzene 0.317g and absolute ethyl alcohol 20mL react for 1h at 70 ℃. The conversion rate of p-chloronitrobenzene is 84.71 percent, and the selectivity of p-chloroaniline is 99.50 percent.
In the case of a low platinum content in this example, the catalytic reaction time is not long enough to result in a low conversion of p-chloronitrobenzene.
Example 8
The catalyst prepared in example 2 was added with 0.08% Pt/15% TiO as in example 42SBA-150.1 g, p-chloronitrobenzene 0.317g and absolute ethyl alcohol 20mL react for 1.5h at 70 ℃. The conversion rate of p-chloronitrobenzene is 99.25 percent, and the selectivity of p-chloroaniline is 99.22 percent.
Example 9
The solution reacted in example 4 was centrifuged to remove the reaction solution, washed with absolute ethanol by centrifugation for a plurality of times, and then dried overnight in a vacuum drying oven at 40 ℃, and the catalyst recovered for the second time was reacted according to the method steps in example 4, with a p-chloronitrobenzene conversion of 97.77% and a p-chloroaniline selectivity of 97.23%. The catalytic activity of the secondarily recovered catalyst is still high.
It is clear from the above examples that the catalysts with different mass fractions of platinum prepared by this process are active for the selective hydrogenation of p-chloronitrobenzene, and overall the amount of platinum used is low and the dechlorination side reactions are low at high catalytic hydrogenation conversion.
Comparative example 1
The catalyst was prepared in substantially the same manner as in example 1, except that the titania layer was not provided in the catalyst, and a 0.1% Pt/SBA-15 catalyst (platinum mass fraction in the catalyst: 0.1%) was prepared by the photocatalytic reduction method.
The method of catalytic selective hydrogenation with catalyst is the same as that of example 4, 0.1g of 0.1% Pt/SBA-15 catalyst, 0.401g of p-chloronitrobenzene and 20mL of absolute ethyl alcohol are added, and the reaction is carried out for 2.0h at 70 ℃. The conversion rate of p-chloronitrobenzene is 13.05 percent, and the selectivity of p-chloroaniline is about 100 percent.
Comparative example 2
The catalyst was prepared in substantially the same manner as in example 1, except that the titania layer was not provided in the catalyst, and a 0.1% Pt/SBA-15 catalyst (platinum mass fraction in the catalyst: 0.1%) was prepared by the photocatalytic reduction method.
The method of catalytic selective hydrogenation with the catalyst is the same as that of example 4, 0.1g of 0.1% Pt/SBA-15 catalyst, 0.401g of p-chloronitrobenzene and 20mL of absolute ethyl alcohol are added, and the reaction is carried out for 3.0h at 70 ℃. The conversion rate of p-chloronitrobenzene is 53.7 percent, and the selectivity of p-chloroaniline is about 100 percent.
Comparative example 3
The catalyst was prepared in substantially the same manner as in example 1, except that the titania layer was not provided in the catalyst, and a 2% Pt/SBA-15 catalyst (platinum mass fraction in catalyst: 2%) was prepared by the photocatalytic reduction method.
The method of catalytic selective hydrogenation with the catalyst is the same as that in example 4, 0.1g of 2% Pt/SBA-15 catalyst, 0.401g of p-chloronitrobenzene and 20mL of absolute ethyl alcohol are added, and the reaction is carried out for 1.0h at 70 ℃. The conversion of p-chloronitrobenzene was 91.51% and the selectivity to chloroaniline was 86.56%.
As is clear from comparison between comparative example 1 and comparative example 3, if platinum is directly supported on SBA-15 without first dispersing titanium dioxide on SBA-15, the catalyst requires a high platinum content and has a good catalytic activity, and at this time, the conversion of the raw material is increased, but the dechlorination side reaction is also significantly enhanced. Only by dispersing titanium dioxide on SBA-15 and then dispersing platinum on titanium dioxide, the catalyst with excellent catalytic activity and target product selectivity can be prepared when the platinum loading is very low.
As can be seen from comparison of comparative examples 1-3 and examples, in the preparation process of the catalyst, titanium dioxide and platinum are sequentially dispersed on the carrier SBA-15, when the catalyst is used for catalyzing selective hydrogenation of p-chloronitrobenzene to prepare p-chloroaniline, the catalyst can achieve excellent catalytic activity only by using a small amount of noble metal platinum, and the occurrence of dechlorination side reactions can be obviously reduced.
FIG. 1 and FIG. 2 are TiO2SBA-15 complexXRD patterns of the composite carrier, and FIG. 3 and FIG. 4 are Pt/TiO2XRD pattern of/SBA-15 catalyst. As can be seen from the comparison between FIGS. 3-4 and FIGS. 1-2, no diffraction peak of platinum is observed in the XRD pattern, which indicates that the catalyst prepared by the method of the present invention has a low platinum loading.
The scope of the present invention is not limited to the above examples, and the catalyst of the present invention can achieve good effect on p-chloronitrobenzene hydrogenation reaction as long as the mass fraction of the active components of the catalyst and the reaction conditions including temperature and time are well controlled.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions and substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (8)

1. The method for preparing p-chloroaniline by selectively hydrogenating p-chloronitrobenzene comprises the steps of using a catalyst containing platinum and titanium dioxide and catalyzing the p-chloronitrobenzene to selectively hydrogenate the p-chloroaniline in a hydrogen environment and under a heating condition, so that dechlorination side reactions during hydrogenation are greatly reduced, wherein the catalyst is Pt/TiO2SBA-15 catalyst, said Pt/TiO2The platinum content in the SBA-15 catalyst is 0.01-0.3 wt%, and the Pt/TiO is2TiO in SBA-15 catalyst2Is in a thin film layer, is spread on a carrier SBA-15 in a single layer or a plurality of layers, and anchors active component platinum on TiO by a photocatalytic reduction method2On the film layer.
2. The method for preparing p-chloroaniline according to claim 1, wherein absolute ethanol is used as a solvent in the selective hydrogenation reaction.
3. The method for preparing parachloroaniline according to claim 1, wherein the temperature of said selective hydrogenation is 40 to 90 ℃.
4. The method for preparing parachloroaniline of claim 1, wherein said catalyst is TiO2Occupies composite carrier TiO25-20 wt% of total weight of SBA-15.
5. The method for preparing parachloroaniline of claim 1, wherein said catalyst is prepared by first sol-gel processing TiO2Loaded on SBA-15 to obtain one or more layers of nano TiO spread on SBA-152Loading active component platinum onto the composite carrier by adopting a photocatalytic reduction method to obtain the Pt/TiO composite carrier2The catalyst is SBA-15.
6. The method for preparing p-chloroaniline according to claim 5 wherein the TiO is2Before loading on the SBA-15, the method also comprises the step of carrying out ultrasonic pretreatment on the SBA-15 by using absolute ethyl alcohol.
7. The method for preparing parachloroaniline of claim 6, wherein the sol-gel method comprises the steps of adding butyl titanate into absolute ethyl alcohol containing SBA-15, adding water, continuously stirring to hydrolyze the butyl titanate, heating the hydrolyzed mixture to 35-45 ℃ to form gel, and drying the gel in vacuum at 60-90 ℃ to obtain TiO2the/SBA-15 composite carrier.
8. The method of claim 7, wherein the photocatalytic reduction comprises subjecting TiO to a reduction reaction2Dispersing the/SBA-15 composite carrier in deionized water, adding methanol and chloroplatinic acid solution for ultrasonic impregnation, placing the mixed solution under ultraviolet irradiation, stirring, performing solid-liquid separation, washing with water to neutrality, and drying to obtain the Pt/TiO2The mass ratio of methanol to water used in the photocatalytic reduction is 1: 5-15, and the ultraviolet illumination time is 5-20 hours.
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CN201711340016.7A CN108031485B (en) 2017-12-14 2017-12-14 Method for preparing parachloroaniline through parachloronitrobenzene selective hydrogenation
PCT/CN2018/120710 WO2019114767A1 (en) 2017-12-14 2018-12-12 Catalyst and preparation method thereof for catalytic selective hydrogenation of chloroaromatic nitro compounds
US16/901,029 US11040336B2 (en) 2017-12-14 2020-06-15 Catalyst of platinum/zirconium dioxide/SBA-15 and method for preparing p-chloroaniline using the same
US17/324,034 US11964261B2 (en) 2017-12-14 2021-05-18 Catalyst of platinum/zirconium dioxide/SBA-15 and method for preparing the same

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WO2019114767A1 (en) * 2017-12-14 2019-06-20 湘潭大学 Catalyst and preparation method thereof for catalytic selective hydrogenation of chloroaromatic nitro compounds
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CN113121359A (en) * 2021-04-23 2021-07-16 湘潭大学 Method for preparing aniline by nitrobenzene hydrogenation and palladium catalyst with hybrid nano structure
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