CN110152661A - A nano-Au-CeO2 (cubic) catalyst for the synthesis of aniline compounds by hydrogenation of nitrobenzene compounds - Google Patents

Abstract

The invention belongs to the technical fields of organic chemistry and catalytic chemistry using nitrobenzene matters as raw material, using alcohols as solvent, using hydrogen as hydrogen source, in the presence of a catalyst, it carries out hydrogenation reaction and generates phenyl amines product, it is using nanocube ceria as carrier that the catalyst forms substantially, and active component is the noble metals such as Au, and preparation method is using deposition-precipitation method that Au is immobilized to nanocube CeO₂On.It is an advantage of the invention that prepared catalyst p-nitrophenyl hydrogenation activity is good, reaction condition is mild, in 120 DEG C and 2MPa H₂Under the conditions of, reacting 2h, nitrobenzene conversion rate and aniline selectively all reach 99.9% or more, meanwhile, catalyst has good reusability.

Description

Nano Au-CeO2 for Synthesis of Aniline Compounds by Hydrogenation of Nitrobenzene Compounds (cubic) catalyst

technical field

The invention belongs to the technical field of organic chemistry and catalytic chemistry, and relates to a catalyst for the synthesis of anilines by hydrogenation of nitrobenzenes and a preparation method thereof.

Background technique

Aniline is one of the most important intermediates in the dye industry. It can be used in the manufacture of acid ink blue in the dye industry; it can be used in the manufacture of golden red in organic pigments. It is used for dyeing nigrosine in the printing and dyeing industry; it is used in the production of many insecticides in the pesticide industry; it is an important raw material for rubber additives, and it can also be used as a raw material for pharmaceutical sulfonamides. It is also used for the production of spices, plastics, varnishes, and films. and other intermediates; and can be used as a stabilizer in explosives, an anti-knock agent in gasoline, and as a solvent; others can also be used to make hydroquinone, 2-phenylindole, etc. The synthesis methods of aniline mainly include nitrobenzene iron powder reduction method, chlorinated animination method, nitrobenzene catalytic hydrogenation reduction method and phenol ammonia solution method. The iron powder reduction method is the oldest method. This method is backward, the yield of aniline is low, and the pollution is serious. This method has been gradually eliminated. The cost of chlorinated animination is relatively high. The catalytic hydrogenation method directly uses hydrogen or a compound capable of decomposing to generate hydrogen as a reducing agent for the hydrogenation of nitro compounds. Hydrogenation of nitro compounds using hydrogen as a reducing agent is currently a relatively common method in industry.

Literature (He Daiping, Department of Chemistry, Tsinghua University, 2006 (31)) prepared Au-ZrO ₂ catalyst by deposition and precipitation method, under the conditions of 1MPa H ₂ and 150 ℃, reacted for 2h, its conversion rate was 91.8%, and its Au loading The amount is 4%. Literature (Song Hua, Dong Haixin, etc. School of Chemistry and Chemical Engineering, Northeast Petroleum University, 2012) studied the effect of Pt-TiO ₂ catalyst on the hydrogenation of p-chloronitrobenzene, and found that the carrier TiO The crystal form of ₂ has a great influence on the catalytic activity of the catalyst, and the selective hydrogenation activity of the catalyst supported by anatase TiO ₂ is obviously higher than that of the catalyst supported by rutile TiO ₂ . Literature (Wen Xia, Hunan Normal University, 2015, 17-23) found through the research on the hydrogenation reaction of nitrobenzene catalyzed by Au supported on titanium dioxide nanotubes, under the conditions of 90 °C, 0.3 MPa, and reaction for 1 h, the hydrothermal reaction The catalyst prepared by roasting titanium dioxide nanotubes at 400℃ for 24 hours can reach 79.28% in the hydrogenation reaction of nitrobenzene. In the literature (Cao Liu, Hunan Normal University, 2014, 14-21), three different catalysts Au-TiO ₂ were prepared by deposition precipitation method using different crystal types of titanium dioxide as supports. Among them, the Au-TiO ₂ -A type catalyst was reacted for 4 hours under the reaction conditions of H2 pressure of 0.4MPa, reaction temperature of 90°C, and stirring speed of 500rpm, and the conversion rate of nitrobenzene reached more than 99%. And after the catalyst was recycled for 3 times, the conversion rate of nitrobenzene dropped from 99.75% to 91.7%. To sum up, the conversion rate of nitrobenzene hydrogenation catalyzed by Au-based catalyst is not very high, and the thermal stability and reusability of the catalyst are not good enough. The nano _- cube CeO2 immobilized Au-based catalyst prepared by the present invention shows high reaction rate and good reusability under mild conditions. The reason is that the structure, acidity and alkalinity and redox property of the support nanocube CeO ₂ affect the activity and selectivity of the reaction catalyzed by Au. Among them, _nanocube CeO2 has redox oxides as supports, which is beneficial to the preferential adsorption of nitro groups in nitrobenzene compounds, and thus has high nitro group hydrogenation selectivity. Using redox _- active nanocube CeO2 as a support enables the preferential adsorption of nitro groups on active sites (e.g., oxygen-deficient sites, crystal faces, and edge/corner sites of Au), thereby hindering the adsorption of other radicals. Adsorption and nonselective hydrogenation of clusters. Furthermore, the enhanced electron transfer from the defect site to the metal d-band due to the presence of defects can further regulate _H2 activation and dissociation.

The present invention finds that nano-cubic ceria with (100) crystal faces is used as a carrier to load nano-gold. Hydrogenation activity of nitrobenzenes and product selectivity of anilines.

Contents of the invention

The purpose of the present invention is to provide a nano-cube CeO ₂ immobilized Au-based catalyst for the highly efficient catalytic nitrobenzene hydrogenation capable of accelerating the reaction rate under relatively mild conditions and a preparation method thereof.

The technical scheme of the present invention: a nano-cube CeO ₂ immobilized Au-based catalyst for hydrogenation reaction of nitrobenzene substances and a preparation method thereof, the catalyst is composed of nano-CeO ₂ and Au, and Au is an active component. The preparation method is to immobilize Au _on nanometer CeO2 by deposition and precipitation. Concrete preparation steps are as follows:

(1) Fully mix Ce(NO ₃ ) ₃ •6H ₂ O solution with a concentration of 0.1~5mol/L and 5~50mL NaOH solution with a concentration of 0.1~10mol/L. Treat at ~200°C, then centrifuge and wash fully with water and ethanol to make the solution alkaline, and then dry overnight at 80~200°C to obtain a yellow powder as the carrier precursor.

(2) Weigh 0.1~10g of the solid obtained in (1) and disperse it into 50~150mL of water, then add 2~30g of urea, stir well at 50~180°C and add dropwise to it with a concentration of 0.01 ~10mol/L chloroauric acid solution, continue to age at 50~180°C for 1~15h, the centrifuged precipitate is fully washed with water until the presence of chloride ions can no longer be detected in the supernatant, and then dried overnight at 50~200°C , to get the catalyst.

(3) The catalyst prepared in (2) can be used for hydrogenation of nitrobenzene compounds to produce anilines, wherein: nitrobenzene and alcohol with a molar ratio of 1:85~1:170 are used as raw materials and solvents, in Carry out hydrogenation reaction in the presence of a catalyst, centrifuge the reacted sample to obtain aniline substances: it is characterized in that the catalyst and raw materials are loaded into the autoclave reactor, the reaction temperature is 20~200°C, and the hydrogen pressure is 0.1~15MPa , The reaction time is 0.5~24h.

The invention has the advantages of mild operating conditions, short reaction time, good performance of the catalyst, easy separation of the catalyst and the realization of the whole reaction system, the conversion rate of nitrobenzene is as high as 99%, and the selectivity of aniline is as high as 99%. , and has good reusability, suitable for industrial applications.

Detailed ways

The present invention is further described below by specific embodiment,

Example 1

(1) Preparation of nano-CeO ₂ carriers with different shapes by hydrothermal method

0.4mol/L Ce(NO ₃ ) ₃ •6H ₂ O solution (5ml, 0.868g of cerous nitrate) and 35mL NaOH solution with a concentration of 0.1~6mol/L were fully mixed, stirred for 30min, then transferred to a hydrothermal kettle Treat at 180°C for 24 hours, wash with water and ethanol after centrifugation to make the solution alkaline, and then dry overnight at 105°C to obtain a yellow powder as the carrier precursor. Then bake at 800°C for 4h.

(2) Preparation of solid catalyst Au-CeO ₂ by deposition precipitation method

_The nano CeO of 1g different appearance Carrier is dispersed in 94mL water, then adds 6g urea, after fully stirring evenly under 80 degree, dropwise to wherein dripping concentration is the chloroauric acid solution of 0.1mol/L (loading capacity is 1wt %, add 0.5mL dropwise), continue aging at 80°C for 4h, centrifuge the precipitate and wash it thoroughly with water until the presence of chloride ions can no longer be detected in the supernatant, then dry at 105°C overnight, and roast at 200°C after drying 4h. Catalyst 1 is obtained.

Example 2

Catalyst 2 as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 600°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 200°C.

Example 3

Catalyst 3 is the same as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 400°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 200°C.

Example 4

Catalyst 4 which is the same as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 200°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 200°C.

Example 5

Catalyst 5 which is the same as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 200°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 600°C.

Example 6

Catalyst 6 which is the same as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 200°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 400°C.

Example 7

Catalyst 7 which is the same as in Example 1, but the calcination temperature of nano-cube CeO ₂ is 200°C, and the calcination temperature of Au-CeO ₂ -cube (cube) is 200°C.

Example 8

Catalyst hydrogenation reaction of nitrobenzene was carried out with the catalyst prepared in Examples 1-7.

The catalytic hydrogenation reaction of nitrobenzene is carried out in a 100ml autoclave. Accurately weigh 0.1 g of catalyst, 1mmol of nitrobenzene, 1mmol of n-octane and 10mL of absolute ethanol as solvents in the autoclave, and repeatedly pass hydrogen after sealing. 0MPa。 More than 5 times, the hydrogen pressure was adjusted to 2. 0 MPa. It was placed in a magnetically stirred oil bath, and heated at 120°C for 2h. After cooling, extract the solution in the kettle and centrifuge to obtain the product.

The reaction product was analyzed by gas chromatography, and n-octane was used as the internal standard. The catalytic performance of catalysts 1-4 is shown in Table 1, and the catalyst performance is shown in Table 2.

Table 1 Catalytic properties of catalysts 1-4 for nitrobenzene hydrogenation

Entry catalyst Conv. (%) Sel. (%) 1 Example 1 4.0 38.47 2 Example 2 9.08 79.8 3 Example 3 99.3 99.6 4 Example 4 87.5 99.8

It can be seen from Table 1 that the calcination temperature of the preferred carrier nanocube CeO ₂ is 400°C.

The nitrobenzene hydrogenation catalytic performance of table 2 catalyst 5-7

Entry catalyst Conv. (%) Sel. (%) 1 Example 5 0.7 99.5 2 Example 6 63.3 90.7 3 Example 7 87.5 99.8

It can be seen from Table 2 that the calcination temperature of the catalyst Au-CeO ₂ -cube (cube) is preferably 200°C.

Example 9

In Example 8, the reaction time was changed to 1h, and other reaction conditions were the same as in Example 8 (each recovered catalyst should be roasted at 200°C for 4h). After the reaction, the sample was analyzed by chromatography, and the conversion rate of nitrobenzene and aniline were calculated. The selectivity, the results are shown in Table 3.

Table 3 Repeatability of Catalyst 3

Entry Reaction cycles Conv. (%) Sel. (%) 1 1 50.9 94.5 2 2 69.4 99.6 3 3 61.5 93.8

It can be seen from Table 3 that the catalyst Au-CeO ₂ -cube-400-200 is very stable, and the conversion and selectivity remain basically unchanged.

In summary, the test shows that the preferred catalyst is Au-CeO ₂ -cube-400-200 (the calcination temperature of the carrier is 400°C, the calcination temperature of the catalyst is 200°C), and it is very stable and can be used repeatedly .

Example 10

Comparative example 1-2

Au-CeO _{2 -poly (CeO 2 is a nanopolyhedron) and Au-CeO 2 -rod (CeO 2 is a} nanorod) are used to catalyze the hydrogenation reaction of nitrobenzene respectively. The catalyst dosage is 1 mmol, and the reaction time is 2 h. In other Under the completely same conditions as in Example 8, a hydrogenation reaction was carried out to form Comparative Example 1-2 to examine the reaction results.

Table 4 nitrobenzene hydrogenation reaction results of comparative examples

comparative example catalyst Conv. (%) Sel. (%) 1 Au-CeO₂-poly 88.0 75.6 2 Au-CeO₂-rod 90.9 89.1

In Comparative Example 1-2, catalysts with different shapes were used to catalyze the hydrogenation reaction of nitrobenzene. In summary, it can be seen that the selectivity and conversion rate of cubes are higher, reaching more than 99%, and because nano-cube ceria has (100) crystal planes, its special crystal planes, suitable acidity and alkalinity and suitable Oxygen deficiency sites are more conducive to the formation of anilines from nitrobenzene compounds.

The present invention is not limited to the above embodiments, and various changes and deformations can be made according to the present invention, as long as they do not deviate from the spirit of the present invention, all should belong to the scope of the present invention.

Claims (4)

1. a kind of nanocube CeO for nitrobenzene hydrogenation₂Immobilized Au base catalyst, it is characterized in that the base of catalyst This group becomes nanocube CeO₂And Au, nanocube CeO₂For carrier, Au is active component.

2. catalyst according to claim 1, it is characterised in that the metal oxide for supported noble metals Au, Pt is to receive Rice cube CeO₂。

3. catalyst according to claim 1, which is characterized in that be for the nitrobenzene and alcohol of 1:85 ~ 1:170 with molar ratio Raw material and solvent carry out hydrogenation reaction in the presence of a catalyst, are centrifuged to sample after reaction, obtain aniline category matter: its It being characterized in that, catalyst and raw material are packed into autoclave reactor, and reaction temperature is 20 ~ 200 DEG C, Hydrogen Vapor Pressure is 0.1 ~ 15MPa, the reaction time be 0.5 ~ reacted down for 24 hours, the catalyst be with different temperatures roast nanocube CeO₂For carrier, Au being supported on carrier and roast obtained catalyst using different temperature, dosage is 0.5 ~ 20g, Au content are 1wt% ~ 10wt%..

4. solvent alcohols used in nitrobenzene hydrogenation described in accordance with the claim 3 can be the alcohol such as ethyl alcohol, methanol, propyl alcohol Substance.