CN111068669B - A kind of heterogeneous catalyst for the selective hydrogenation reaction of quinoline compounds and its application - Google Patents

Abstract

The invention discloses a heterogeneous catalyst for the selective hydrogenation reaction of quinoline compounds and its application. The heterogeneous catalyst consists of 1-10% noble metal particles and 9-90% oxygen It consists of titanium dioxide with oxygen vacancies, and noble metal particles are supported on the titanium dioxide with oxygen vacancies. Compared with the general titanium dioxide-supported noble metal catalyst, when the heterogeneous catalyst of the present invention is used to catalyze the selective hydrogenation reaction of quinoline compounds, due to the joint action of the noble metal in the heterogeneous catalyst of the present invention and the oxygen vacancies of titanium dioxide, electrons are generated transfer to enrich the charge of noble metals, thereby improving the catalytic activity of heterogeneous catalysts.

Description

A heterogeneous catalyst for selective hydrogenation of quinoline compounds and its application

technical field

The invention relates to the field of catalysts, in particular to a heterogeneous catalyst for selective hydrogenation of quinoline compounds and its application.

Background technique

The synthesis of functionalized 1,2,3,4-tetrahydroquinoline (py-THQ) has attracted increasing attention due to its great application value in the production of pharmaceuticals, alkaloids, pesticides, and other fine chemicals. High reaction temperatures (>120 °C) and long reaction times (>24 h) are required for the hydrogenation of N-heteroarenes over transition metal and metal-free catalysts because of their low _H2 activation capacity. Noble metal (such as Ir, Ru, Rh, Pd, Pt) catalytic systems have high catalytic activity for the hydrogenation of quinoline compounds. However, whether it is a heterogeneous catalyst or a homogeneous catalyst, in the presence of other reducible functional groups (Cl, OH, CHO, etc.), the substrate scope of the catalyst is generally poor, resulting in a decrease in its chemoselectivity. In addition, the strong adsorption of quinoline and hydroquinoline may lead to catalyst poisoning. Therefore, it is of great significance to develop highly active and highly selective hydrogenation catalysts for quinoline compounds.

For a long time, people have been trying to develop catalysts with high activity, high selectivity and high stability for the selective hydrogenation of quinolines to prepare 1,2,3,4-tetrahydroquinolines. As a common metal oxide, _TiO2 has attracted extensive attention as a support due to its strong interaction with metals. For example, the use of nano-Au catalysts supported on high specific surface area _TiO2 can quantitatively convert 6-chloroquinoline to 6-chlorotetrahydroquinoline within 3 h under the reaction conditions of 60 °C and 2 MPa _H2 without dehalogenation Happened (J.Am. Chem. Soc. 2012, 134, 17592.). The substrate universality of the catalytic system is very good, for some reducible groups (acetyl, vinyl, etc.) substituted quinoline substrates or other nitrogen-containing aromatic compounds (such as isoquinoline, 7,8-benzo Quinoline and acridine etc.) all can obtain better yield. At the same time, the rutile phase TiO ₂ supported nano-gold catalyst can also use formic acid as a hydrogen source to complete the selective hydrogenation of quinoline compounds at 130 °C (Adv. Synth. Catal. 2015, 357, 753.). However, these catalysts are complicated in preparation or harsh in reaction conditions.

The defect of metal oxide is one of the important factors affecting its performance. Oxygen vacancy is one of the most important defects of metal oxide, and its influence on the electronic structure regulation of metal and the influence in quinoline hydrogenation reaction is less studied. The present invention It is to apply the strong interaction between oxygen-vacancy _TiO2 and noble metals to heterogeneous catalytic reactions.

Contents of the invention

For the above-mentioned technical problems existing in the prior art, the object of the present invention is to provide a kind of heterogeneous catalyst for the selective hydrogenation reaction of quinoline compounds and its application, and synthesize the heterogeneous catalyst containing precious metal particles by a specific method, The heterogeneous catalyst is stable to air, water and heat, and it is applied in the selective hydrogenation reaction of quinoline, showing excellent catalytic activity and selectivity.

The heterogeneous catalyst for the selective hydrogenation of quinoline compounds is characterized in that the heterogeneous catalyst consists of 1-10% noble metal particles and 9-90% oxygen vacancy The composition of titanium dioxide, noble metal particles supported on the titanium dioxide with oxygen vacancies.

The heterogeneous catalyst for the selective hydrogenation reaction of quinoline compounds is characterized in that the preparation method of the titanium dioxide having oxygen vacancies is as follows: using titanium dioxide as a raw material, in an inert gas atmosphere, at 600 ~ Calcining at 1200° C. for 0.5-6 h to obtain the titanium dioxide with oxygen vacancies.

The heterogeneous catalyst for selective hydrogenation of quinoline compounds is characterized in that in the method for preparing titanium dioxide with oxygen vacancies, the raw material of titanium dioxide is TiO ₂ (B), and the inert gas is nitrogen.

A described heterogeneous catalyst for the selective hydrogenation of quinolines is characterized in that the preparation method of the heterogeneous catalyst comprises the following steps:

1) adding the titanium dioxide with oxygen vacancies into the aqueous solution of the noble metal precursor, stirring and mixing evenly, so that the noble metal precursor is adsorbed on the titanium dioxide, and then heating and stirring at 60-80° C. until the water is completely volatilized to obtain a solid mixture;

2) The solid mixture obtained in step 1) is placed in a tube furnace and roasted under an atmosphere of hydrogen gas, so that the noble metal precursor supported on the titanium dioxide is reduced to noble metal particles, and the heterogeneous catalyst is obtained.

The described heterogeneous catalyst for the selective hydrogenation of quinoline compounds is characterized in that the noble metal particles are Au, Ag, Rh, Os, Ir, Ru, Pt or Pd particles; the particles of the noble metal particles are The diameter is 1 to 50 nm, preferably 1 to 15 nm.

The heterogeneous catalyst for the selective hydrogenation of quinoline compounds is characterized in that in step 2), the calcination temperature is 200-600°C, preferably 250-500°C.

The application of the heterogeneous catalyst in the selective hydrogenation reaction of quinoline compounds is characterized in that the quinoline compounds are mixed with a solvent, and the mixed reaction solution is carried out with hydrogen under the action of the heterogeneous catalyst. Selective hydrogenation reaction to generate hydrogenated quinoline compounds; wherein the reaction temperature is 0-150°C, and the reaction pressure is 0.1-10MPa; the solvent is water, ethanol, dichloromethane, tetrahydrofuran, ethyl acetate, dioxygen Hexacyclic, N,N-dimethylformamide, n-hexane or toluene.

The application of the heterogeneous catalyst in the selective hydrogenation reaction of quinoline compounds is characterized in that the quinoline compounds are quinoline or substituted quinoline, the benzene ring or pyridine ring of the substituted quinoline The number of substituents is one or more, and the substituents on the benzene ring or pyridine ring of the substituted quinoline are halogen, C1~C3 alkoxy, hydroxyl or phenyl.

The application of the heterogeneous catalyst in the selective hydrogenation reaction of quinoline compounds is characterized in that the mass of the heterogeneous catalyst is 0.1-10% of the mass of quinoline compounds.

The application of the heterogeneous catalyst in the selective hydrogenation reaction of quinoline compounds is characterized in that the temperature for the selective hydrogenation reaction is 20-80° C., the pressure is 0.1-2 MPa, and the solvent is water or ethanol.

Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art:

1. In the preparation process of the catalyst carrier of the present invention, TiO ₂ (B) is selected as TiO 2 (B), and TiO ₂ (B) has a sheet-like multilayer structure, which is unstable at high temperature, and O is detached when calcined at high temperature under an inert atmosphere. , resulting in the formation of oxygen vacancies. In the catalyst prepared by the present invention, due to the strong interaction between the noble metal particles and the titania carrier with oxygen vacancies, the contact surface between the noble metal particles and the titania carrier increases, which promotes the dissociation of hydrogen, and the contact surface is not easy to be The quinoline is attached, thereby inhibiting the nitrogen atom in the quinoline from forming a coordination bond with the catalyst to reduce the catalytic activity, thereby effectively avoiding the poisoning of the catalyst.

2. In the heterogeneous catalyst of the present invention, due to the strong interaction between the noble metal particles and the titanium dioxide carrier with oxygen vacancies and the effectiveness of hydrogen reduction (that is, hydrogen will effectively reduce the ionic noble metal to a simple substance), the present invention The prepared heterogeneous catalyst has uniform noble metal particle size and good dispersion, and the average diameter of the noble metal particle can reach 1-10 nm. The heterogeneous catalyst is stable to air, water and heat, and its catalytic quinoline hydrogenation activity does not decrease after it exists in the air for 5 months, and the metal valence state remains unchanged.

3. Compared with the general titanium dioxide-supported noble metal catalyst, when the heterogeneous catalyst of the present invention is applied to catalyze the selective hydrogenation reaction of quinoline compounds, the noble metal in the heterogeneous catalyst of the present invention and the oxygen vacancies of titanium dioxide act together, resulting in electron The offset of the noble metal makes the noble metal rich in charge (the electron-rich noble metal particles are more conducive to its dispersion on the catalyst support, which is more conducive to the exposure of the metal active site and improves the catalytic activity), thereby improving the catalytic performance of the heterogeneous catalyst. active. Taking the preparation of 1,2,3,4-tetrahydroquinoline by catalytic hydrogenation of quinoline as an example, the conversion rate of quinoline can reach 100%, and the selectivity of 1,2,3,4-tetrahydroquinoline can reach above 95.

Description of drawings

Fig. 1 is the HRTEM figure of the catalyst obtained in embodiment 1.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the protection scope of the present invention is not limited thereto.

Example 1 Heterogeneous catalyst based on TiO _2-x supported Ru

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Then add 0.2 g of the TiO _2-x material prepared above into a 100 mL beaker, then add 0.15 ml of pre-prepared RuCl ₃ aqueous solution (the concentration of RuCl ₃ aqueous solution is 10 mg/mL), stir and mix evenly, so that RuCl ₃ is adsorbed on TiO _2-x material on. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Ru after later calcination.

The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h in a hydrogen atmosphere to obtain the TiO _2-x supported Ru catalyst.

Example 2 Heterogeneous catalyst based on TiO _2-x supported Pd

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Then add 0.2 g of the TiO _2-x material prepared above into a 100 mL beaker, and then add 0.15 ml of a pre-prepared PdCl ₃ aqueous solution (the concentration of the PdCl ₃ aqueous solution is 10 mg/mL), stir and mix evenly, so that PdCl ₃ is adsorbed on the TiO _2-x material on. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Pd after later calcination.

The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h under a hydrogen atmosphere to obtain a Pd catalyst supported on TiO _2-x .

Example 3 A heterogeneous catalyst based on TiO _2-x supported Au

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Then add 0.2 g of the TiO _2-x material prepared above into a 100 mL beaker, and then add 0.15 ml of pre-configured HAuCl ₄ 4H ₂ O aqueous solution (the concentration of HAuCl ₄ 4H 2 O aqueous solution is 10 mg/mL), stir and mix evenly, HAuCl ₄ ·4H ₂ O was adsorbed on the TiO _2-x material. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Au after later calcination.

The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h under a hydrogen atmosphere to obtain the TiO _2-x supported Au catalyst.

Example 4 Heterogeneous catalyst based on TiO _2-x supported Pt

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Then add 0.2 g of the TiO _2-x material prepared above into a 100 mL beaker, and then add 0.15 ml of pre-configured H ₂ PtCI ₆ 6H ₂ O aqueous solution (the concentration of H ₂ PtCI ₆ 6H ₂ O aqueous solution is 10 mg/mL ), stirring and mixing evenly, so that H ₂ PtCI ₆ ·6H ₂ O is adsorbed on the TiO _2-x material. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Pt after later calcination.

The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h in a hydrogen atmosphere to obtain a TiO _2-x supported Pt catalyst.

Example 5 Heterogeneous catalyst based on TiO _2-x loaded Ag

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Then add 0.2 g of the TiO _2-x material prepared above into a 100 mL beaker, and then add 0.15 ml of a pre-prepared AgNO ₃ aqueous solution (the concentration of the AgNO ₃ aqueous solution is 10 mg/mL), stir and mix evenly, so that AgNO ₃ is adsorbed on the TiO _2-x material on. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Ag after later calcination.

The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h in a hydrogen atmosphere to obtain the TiO _2-x supported Ag catalyst.

The characterization of TiO _2-x supported Ru catalyst in embodiment 6

The TiO _2-x supported Ru catalyst obtained in Example 1 was characterized by high-resolution transmission electron microscopy (HRTEM). The characterization results are shown in Figure 1, which confirmed that the catalyst was composed of titanium dioxide nano-metal Ru. The Ru nanoparticles are uniformly distributed on the _TiO2-x material, and Ru and TiO2 are in close contact, indicating that there is an obvious interaction between Ru and TiO2. By counting 150 nanometer Ru metal particles, the average particle size of Ru nanoparticles is 1.8 nm.

Example 7 The heterogeneous catalyst prepared in Example 1 catalyzed the hydrogenation of quinoline to prepare tetrahydroquinoline

After adding 118 μl of quinoline, 10 mg of the heterogeneous catalyst prepared in Example 1 and 10 mL of dichloromethane into a 50 mL stainless steel autoclave, the stainless steel autoclave was inflated and degassed with hydrogen for 3 times (i.e. by hydrogen Replace the air in the stainless steel autoclave, empty the air in the stainless steel autoclave, the following examples are the same), fill with hydrogen to 1MPa and seal, heat in a water bath at 60°C, stir magnetically, and perform selective hydrogenation reaction for 3 hours . After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution are separated by centrifugation, and the reaction solution is detected by gas chromatography. The conversion rate of quinoline is 98% and the selectivity of 1,2,3,4-tetrahydroquinoline is 97%. .

Example 8 The heterogeneous catalyst prepared in Example 2 catalyzed the hydrogenation of quinoline to prepare tetrahydroquinoline

Add 118 μl of quinoline, 10 mg of the heterogeneous catalyst prepared in Example 2, and 10 mL of tetrahydrofuran into a 50 mL stainless steel autoclave. After inflating and degassing the stainless steel autoclave with hydrogen for 3 times, fill it with hydrogen to 1 MPa and seal it , heated in a water bath at 80°C, stirred magnetically, and carried out selective hydrogenation reaction for 3 h. After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution are separated by centrifugation, and the reaction solution is detected by gas chromatography. The conversion rate of quinoline is 99% and the selectivity of 1,2,3,4-tetrahydroquinoline is 90%. .

Example 9 The heterogeneous catalyst prepared in Example 3 catalyzed the hydrogenation of quinoline to prepare tetrahydroquinoline

118 μl of quinoline, 10 mg of the heterogeneous catalyst prepared in Example 3 and 10 mL of ethanol were added to a 50 mL stainless steel autoclave. After the stainless steel autoclave was inflated and degassed with hydrogen for 3 times, hydrogen was charged to 1 MPa and Seal it, heat it in a water bath at 60°C, stir it with magnetic force, and carry out selective hydrogenation reaction for 3 h. After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution are separated by centrifugation. The reaction solution is detected by gas chromatography. The conversion rate of quinoline obtained by detection and calculation is 98%, and the selectivity of 1,2,3,4-tetrahydroquinoline is 95%. .

Example 10 The heterogeneous catalyst prepared in Example 4 catalyzed the hydrogenation of quinoline to prepare tetrahydroquinoline

118 μl of quinoline, 10 mg of the heterogeneous catalyst prepared in Example 4 and 10 mL of ethanol were added to a 50 mL stainless steel autoclave. After the stainless steel autoclave was inflated and degassed with hydrogen for 3 times, hydrogen was charged to 1 MPa and Seal it, heat it in a water bath at 60 °C, stir it with magnetic force, and carry out selective hydrogenation reaction for 3 h. After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution are separated by centrifugation. The reaction solution is detected by gas chromatography. The conversion rate of quinoline is 99% and the selectivity of 1,2,3,4-tetrahydroquinoline is 96%. .

Example 11 The heterogeneous catalyst prepared in Example 5 catalyzed the hydrogenation of quinoline to prepare tetrahydroquinoline

Add 118 μl of quinoline, 10 mg of the catalyst of Example 5 and 10 mL of N,N-dimethylformamide into a 50 mL stainless steel autoclave. Hydrogen to 1 MPa and sealed, heated in a water bath at 60 °C, magnetically stirred, for selective hydrogenation reaction, reacted for 3 h. After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution are separated by centrifugation. The reaction solution is detected by gas chromatography. The conversion rate of quinoline is 90% and the selectivity of 1,2,3,4-tetrahydroquinoline is 95%. .

Examples 8-11 illustrate that the titanium dioxide-supported noble metals with vacancies have good activity and selectivity for the hydrogenation of quinoline.

Example 12 Catalyzing the hydrogenation of quinoline to prepare tetrahydroquinoline with the catalyst prepared in Example 3 after standing for 5 months

After placing the heterogeneous catalyst prepared in Example 3 in an environment with a cool room temperature and a relative humidity of 70% to 80% for 5 months, verify its catalytic activity according to the following steps: place 118 μl quinoline, 10 mg for 5 months Then add the catalyst prepared in Example 3 and 10 mL of ethanol into a 50 mL stainless steel autoclave. After inflating and degassing the stainless steel autoclave with hydrogen for 3 times, fill it with hydrogen to 1 MPa and seal it, and heat it in a water bath at 60 °C. Magnetic stirring was carried out for selective hydrogenation reaction for 3h. After stopping the reaction, the residual hydrogen in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The heterogeneous catalyst and the reaction solution were separated by centrifugation, and the reaction solution was detected by gas chromatography. The detection and calculation showed that the conversion rate of quinoline was 96%, and the selectivity of 1,2,3,4-tetrahydroquinoline was 92%. . By comparing Example 14 with Example 10, it can be seen that the catalyst obtained in Example 3 has good stability and is inert to air and moisture.

Examples 13-20

Examples 14-21 are examples of preparing functional hydrides using the heterogeneous catalyst prepared in Example 1 to catalyze the hydrogenation reaction of quinoline compounds. The operating steps of Examples 14-21 are the same as in Example 7, and the moles of the reaction substrate Feeding amount, the added volume of solvent and the added amount of catalyzer are the same as embodiment 7. Table 1 shows the reaction conditions and corresponding reaction results of each embodiment.

Table 1

It can be seen from Examples 13-20 that the catalyst has good universality, and different substituents can be well retained in the reaction process, that is to say, Ru/TiO _2-x can be used in the catalytic addition of quinoline compounds Hydrogen is a highly active and selective catalyst.

Comparative Example 1 A heterogeneous catalyst based on TiO ₂ (B) supported Ru for the hydrogenation of quinoline

Add 0.2g TiO ₂ (B) to a 100mL beaker, then add 0.15ml pre-configured RuCl ₃ aqueous solution (the concentration of RuCl ₃ aqueous solution is 10 mg/mL), stir and mix evenly, so that RuCl ₃ is adsorbed on TiO ₂ (B) material. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Ru after later calcination. The above-prepared solid mixture was placed in a tube furnace and calcined at 300°C for 1 h in a hydrogen atmosphere to obtain the TiO ₂ (B)-supported Ru catalyst.

Catalytic reaction process: Add 118 μl quinoline, 10 mg TiO ₂ (B)-supported Ru catalyst prepared above and 10 mL ethanol into a 50 mL stainless steel autoclave. to 1 MPa and sealed, heated in a water bath at 60°C with magnetic stirring, and reacted for 3 h. After stopping the reaction, the residual hydrogen gas was carefully discharged, and the reaction solution was taken out. The catalyst and the reaction solution were separated by centrifugation, and the reaction solution was detected by gas chromatography. The conversion rate of quinoline was calculated to be 20%, and the selectivity of 1,2,3,4-tetrahydroquinoline was 85%.

Comparative Example 2 Catalyst based on titanium dioxide P25 supported Ru for the hydrogenation of quinoline to prepare tetrahydroquinoline

Catalyst preparation: Add 0.2 g of titanium dioxide P25 into a 100 ml beaker, then add 0.15 ml of pre-configured RuCl ₃ aqueous solution (concentration of RuCl ₃ aqueous solution is 10 mg/mL), stir and mix evenly, so that RuCl ₃ is adsorbed on titanium dioxide P25. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Ru after later calcination. The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h in a hydrogen atmosphere to obtain a P25-supported Ru catalyst.

Catalyzed reaction process: Add 118 μl quinoline, 10 mg of the above-prepared P25-loaded Ru catalyst and 10 mL of ethanol into a 50 mL stainless steel autoclave, inflate and degas the autoclave with hydrogen gas for 3 times, then fill it with hydrogen gas to 1 MPa and seal it , heated in a water bath at 60°C with magnetic stirring, and reacted for 3 h. After stopping the reaction, the residual hydrogen gas was carefully discharged, and the reaction solution was taken out. The catalyst and the reaction solution were separated by centrifugation, and the reaction solution was detected by gas chromatography. The detection and calculation showed that the conversion rate of quinoline was 25%, and the selectivity of 1,2,3,4-tetrahydroquinoline was 96%.

It can be seen from Comparative Example 1 and Comparative Example 2 that when TiO ₂ (B) or titanium dioxide P25 is used as a carrier to support nano-metal Ru, its catalytic activity is not as good as that of the catalyst prepared in Example 3, which proves that the oxygen vacancies of titanium dioxide play a role. play an important role.

Comparative Example 3 Heterogeneous Catalyst Based on TiO _2-x Supported Ru Reduction with NaBH ₄

After calcination of 0.4g TiO ₂ (B) at 600°C for 1 h under nitrogen atmosphere, a titanium dioxide material with oxygen vacancies was obtained, which was labeled as TiO _2-x material.

Take 0.2 g of the TiO _2-x material prepared above and add it to 50 mL of deionized water, sonicate for 10 min, then add 0.15 ml of pre-configured RuCl ₃ aqueous solution (concentration of RuCl ₃ aqueous solution is 10 mg/mL), and sonicate for 10 min , add 5 mL of freshly prepared sodium borohydride aqueous solution and continue to sonicate (concentration of sodium borohydride aqueous solution is 1 mg/mL), reduce Ru ³⁺ to elemental Ru, then filter with suction, wash the filter residue with water several times, and dry to obtain TiO _{2 -x} supported Ru catalyst.

Catalytic reaction process: Add 118 μl quinoline, 10 mg TiO _2-x- supported Ru catalyst prepared above and 10 mL ethanol into a 50 mL stainless steel autoclave. 1 MPa and sealed, heated in a 60°C water bath with magnetic stirring, and reacted for 3 h. After stopping the reaction, the residual hydrogen gas was carefully discharged, and the reaction solution was taken out. The catalyst and the reaction solution were separated by centrifugation, and the reaction solution was detected by gas chromatography. The conversion rate of quinoline was 55% and the selectivity of 1,2,3,4-tetrahydroquinoline was 95%.

From the comparison of the reaction results of Comparative Example 3 and Example 7, it can be seen that the reduction mode has a close relationship with the catalyst activity. The catalyst prepared by reducing Ru ³⁺ to elemental Ru by high-temperature calcination under hydrogen atmosphere has higher catalytic activity.

Comparative example 4 Catalyst based on commercial activated carbon supported Ru for the hydrogenation of quinoline to prepare tetrahydroquinoline

Catalyst preparation: Take 0.2 g commercial activated carbon (coconut shell activated carbon, 200-300 mesh, purchased from Jiuding Chemical Technology Co., Ltd.), add it to 50 mL deionized water, add 0.15 mL pre-prepared RuCl ₃ aqueous solution (RuCl ₃ aqueous solution concentration of 10 mg/mL), stir and mix evenly, so that RuCl ₃ is adsorbed on the activated carbon. Then heat and stir at 70° C. until the deionized water in the beaker is completely volatilized to obtain a solid mixture. The solid obtained by this method can closely and uniformly combine titanium dioxide and Ru after later calcination. The solid mixture prepared above was placed in a tube furnace and calcined at 300 °C for 1 h under a hydrogen atmosphere to obtain a Ru catalyst supported on activated carbon.

Catalytic reaction process: Add 118 μl quinoline, 10 mg of the commercial activated carbon-supported Ru catalyst prepared above, and 10 mL of ethanol into a 50 mL stainless steel autoclave. After inflating and degassing with hydrogen gas for 3 times, fill it with hydrogen gas to 1 MPa and seal it. , heated in a water bath at 80 °C, stirred magnetically, and reacted for 3 h. After stopping the reaction, the residual hydrogen gas was carefully discharged, and the reaction solution was taken out. The catalyst and the reaction solution were separated by centrifugation, and the reaction solution was detected by gas chromatography. The detection and calculation showed that the conversion rate of quinoline was 18%, and the selectivity of 1,2,3,4-tetrahydroquinoline was 43%.

The content described in this specification is only an enumeration of the implementation forms of the inventive concepts, and the protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments.

Claims (4)

1. the application of a heterogeneous catalyst in the selective hydrogenation reaction of quinolines, characterized in that the quinolines are mixed with a solvent, and the mixed reaction solution is mixed with hydrogen under the action of the heterogeneous catalyst Carry out selective hydrogenation reaction to generate hydrogenated quinoline compounds; wherein the reaction temperature is 0-150°C, and the reaction pressure is 0.1-10MPa; the solvent is water, ethanol, dichloromethane, tetrahydrofuran, ethyl acetate, di Oxyhexane, N,N-dimethylformamide, n-hexane or toluene; The catalyst is calculated by weight percentage, the heterogeneous catalyst is composed of 10% noble metal particles and 90% titanium dioxide with oxygen vacancies, and the noble metal particles are supported on the titanium dioxide with oxygen vacancies; The preparation method of the titanium dioxide with oxygen vacancies is as follows: using titanium dioxide as a raw material, calcining at 600-1200° C. for 0.5-6 h in an inert gas atmosphere to obtain the titanium dioxide with oxygen vacancies; the raw material of titanium dioxide is TiO ₂ (B), the inert gas is nitrogen; The preparation method of described heterogeneous catalyst comprises the following steps: 1) adding the titanium dioxide with oxygen vacancies into the aqueous solution of the noble metal precursor, stirring and mixing evenly, so that the noble metal precursor is adsorbed on the titanium dioxide, and then heating and stirring at 60-80° C. until the water is completely volatilized to obtain a solid mixture; 2) The solid mixture obtained in step 1) is placed in a tube furnace, and roasted under an atmosphere of hydrogen gas, so that the noble metal precursor supported on the titanium dioxide is reduced to noble metal particles, that is, the heterogeneous catalyst is prepared; The noble metal particles are Au, Ag, Rh, Os, Ir, Ru, Pt or Pd particles; the particle diameter of the noble metal particles is 1-15nm; in step 2), the calcination temperature is 250-500°C. 2. the application of the heterogeneous catalyst as claimed in claim 1 in the selective hydrogenation reaction of quinoline compounds is characterized in that the quinoline compounds are quinoline or substituted quinolines, the benzene of the substituted quinolines The number of substituents on the ring or pyridine ring is one or more, and the substituents on the benzene ring or pyridine ring of the substituted quinoline are halogen, C1~C3 alkoxy, hydroxyl or phenyl. 3. The application of the heterogeneous catalyst as claimed in claim 1 in the selective hydrogenation reaction of quinoline compounds, characterized in that the mass of the heterogeneous catalyst is 0.1% to 10% of the mass of quinoline compounds. 4. The application of the heterogeneous catalyst according to claim 1 in the selective hydrogenation reaction of quinoline compounds, characterized in that the temperature for the selective hydrogenation reaction is 20 to 80° C., the pressure is 0.1 to 2 MPa, and the solvent For water or ethanol.

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