A method for improving the activity and selectivity of a hydrogenation catalyst Pt / SnO2-Sb2O3 for nitrostyrene

Abstract

The present application relates to a kind of methods for improving the activity and selectivity of nitrostyrene hydrogenation catalyst Pt / SnO2-Sb2O3.The catalyst Pt / SnO2-Sb2O3 is reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50~250 ℃ for 1~5h, and then heat-treated in air atmosphere at 80~150 ℃ for 2~132h or placed at room temperature for 15~120 days, and then reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50~100 ℃ for 1~5h, and then selectively hydrogenated in anhydrous ethanol to prepare aminostyrene from nitrostyrene.The selectivity of aminostyrene reaches 95% when nitrostyrene is completely converted.The above scheme significantly improves the activity of catalyst Pt / SnO2-Sb2O3, and solves the problem of reducing the selectivity of aminostyrene during the storage process.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for improving the activity and selectivity of Pt / SnO2-Sb2O3 catalyst for the hydrogenation of nitrostyrene. Specifically, the method comprises the following steps: reducing the catalyst in 10% H2-N2 mixed gas or high-purity hydrogen at 50-250℃ for 1-5h, then heat-treating the catalyst in air atmosphere at 80-150℃ for 2-132h or placing the catalyst at room temperature for 15-120 days, reducing the catalyst in 10% H2-N2 mixed gas or high-purity hydrogen at 50-100℃ for 1-5h, and then catalytically hydrogenating nitrostyrene in anhydrous ethanol with high-purity hydrogen as the hydrogen source to prepare aminostyrene. After the above treatment, the activity and selectivity of the Pt / SnO2-Sb2O3 catalyst are significantly improved. BACKGROUND

[0002] Arylamine compounds containing easily-reducible groups are an important class of intermediates in organic synthesis, and are widely used in the fields of medicine, pesticides, dyes, fluorescent brighteners, stabilizers and high-molecular polymers. Aminostyrene is an important intermediate for the synthesis of pesticides, dyes, pigments, medicines and high-performance polymers.

[0003] Catalytic hydrogenation of nitrostyrene is a relatively green approach for the preparation of aminostyrene, but since the reactant molecule contains both a nitro group and an easily-reducible vinyl group, it is challenging to selectively reduce the nitro group without reducing the vinyl group. Au / TiO2, Au / Fe2O3, Pt / TiO2, Pt / FeO xor hydrogenation of nitrostyrene catalyzed by Ag / Al2O3 in tetrahydrofuran, without accumulation of phenylhydroxylamine in the reaction process, the yield of aminostyrene can reach 90%~96%, but the catalyst activity is relatively low ((Corma, Serna, Science., 2006), (Macino, Barnes et al., Nature Catal., 2019), (Wei, Liu et al., Nature Comm., 2014) (Shimizu, Miyamoto et al., J. Catal., 2010)). CN104974047B discloses a technology for catalyzing hydrogenation of nitrostyrene with Pt / SnO2-Sb2O3 catalyst in ethanol, H2O, n-heptane, H2O-ethanol mixture with any ratio, H2O-n-heptane mixture with any ratio solvent, which has the advantages of high selectivity for nitro hydrogenation and no catalytic activity for vinyl hydrogenation, etc. For example, 0.15g of 0.5wt% Pt / SnO2-Sb2O3 catalyst reduced at 250℃ is used to catalyze hydrogenation of 0.25g of 4-nitrostyrene in 5mL of ethanol at 50℃, and the reaction is carried out for 4h, the conversion rate of 4-nitrostyrene is 97.6%, and the selectivity of 4-aminostyrene is 95.6%. However, the scheme mainly has the following problems: (1) the catalyst activity is relatively low; (2) subsequent studies have found that after the reduced catalyst is placed for a period of time, it is used to catalyze hydrogenation of nitrostyrene, and the selectivity of aminostyrene is greatly reduced. Therefore, how to further improve the activity of the catalyst while maintaining the high selectivity of the catalyst for aminostyrene, and how to restore and improve the selectivity of aminostyrene for the catalyst placed for a period of time are problems to be solved. SUMMARY

[0004] The present application relates to a catalyst Pt / SnO2-Sb2O3 reduced at 50~250℃, which is heat-treated under suitable conditions, and is used to catalyze selective hydrogenation of nitrostyrene in anhydrous ethanol to prepare aminostyrene, and the activity and selectivity of the catalyst after heat treatment are significantly improved.

[0005] The technical scheme adopted by the present application is that: the Pt / SnO2-Sb2O3 catalyst after calcination is reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50-250 DEG C for 1-5h, and then is heat-treated in an air atmosphere at 80-150 DEG C for 2-132h or is placed at room temperature for 15-120 days, and then is reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50-100 DEG C for 1-5h, and then, in anhydrous ethanol, catalytic hydrogenation of nitrostyrene is carried out to prepare aminostyrene, the volume ratio of anhydrous ethanol to nitrostyrene is (5-50):1, the mass ratio of nitrostyrene to the catalyst is (1-10):1, the reaction kettle is screwed tightly, high-purity nitrogen is blown for 5min at room temperature, the reaction kettle is heated to 35-100 DEG C, preheating is carried out for 20min, 1-6MPa H2 is added, stirring is started, and the reaction is carried out until the reactants are close to or reach complete conversion, and aminostyrene is obtained.

[0006] The nitrostyrene is 3-nitrostyrene and 4-nitrostyrene.

[0007] The Pt / SnO2-Sb2O3 catalyst is prepared by the following method: SnO2-Sb2O3 powder is calcined in a muffle furnace air atmosphere at 250-450 DEG C for 2-6h, a certain amount of chloroplatinic acid solution is loaded onto the above calcined SnO2-Sb2O3 carrier by impregnation, the mass content of Pt is 0.5-1%, drying is carried out at 80-120 DEG C for 8-12h, grinding and sieving are carried out, and calcination is carried out at 250-500 DEG C for 3-6h.

[0008] The molar ratio of Sn to Sb of the SnO2-Sb2O3 powder is (5-90):1.

[0009] The present application has the following advantages: (1) anhydrous ethanol is an environmentally acceptable solvent, and pollution to the environment caused by the use of harmful solvents such as toluene and tetrahydrofuran is avoided.

[0010] (2) compared with the catalyst Pt / SnO2-Sb2O3 disclosed in CN104974047B, the activity of the catalyst after heat treatment according to the present scheme is obviously improved.

[0011] (3) the problem of reduction of the selectivity of aminostyrene during the storage of the Pt / SnO2-Sb2O3 catalyst is solved, and a method for restoring and improving the selectivity of the catalyst is provided.

[0012] In summary, the Pt / SnO2-Sb2O3 catalyst is reduced in 10% H2-N2 mixed gas or high purity hydrogen at 50-250°C for 1-5 h, and then treated at 80-150°C in air for 2-132 h or placed at room temperature for 15-120 days, and then reduced in 10% H2-N2 mixed gas or high purity hydrogen at 50-100°C for 1-5 h, and then the catalytic hydrogenation of nitrostyrene in anhydrous ethanol to prepare aminostyrene is a high-efficiency, safe and green process. DETAILED DESCRIPTION

[0013] Example 1 Pt / SnO2-Sb2O3 reduced at 250°C and placed at room temperature and heat treated to catalyze the hydrogenation of 3-nitrostyrene

[0014] The Pt / SnO2-Sb2O3 catalyst was prepared by an equal volume impregnation method, and the mass content of Pt was 0.5 wt%, and the molar ratio of Sn to Sb was 9:1.

[0015] The catalyst was reduced in 10% H2-N2 mixed gas at 250°C for 2 h, and the reduced Pt / SnO2-Sb2O3 was placed at room temperature for 37 days, and then reduced in 10% H2-N2 mixed gas at 50°C for 2 h, and directly used for the reaction. 0.15 g of the above-mentioned catalyst, 10 mL of anhydrous ethanol, and 0.26 g of 3-nitrostyrene were added to a 50 mL stainless steel reaction kettle, the reaction kettle was tightly closed, and high-purity N2 was blown for 5 min at room temperature. The reaction kettle was preheated at 50°C for 20 min, 4 MPa H2 was filled, stirring was started, and the reaction was carried out for 1 h. After the reaction kettle was cooled, the reaction product was analyzed by gas chromatography. The conversion rate of 3-nitrostyrene was 100%, and the selectivity of 3-aminostyrene was 92.8%.

[0016] Comparative Example 1 Pt / SnO2-Sb2O3 reduced at 250°C and placed at room temperature, resulting in a decrease in the selectivity of aminostyrene

[0017] The preparation process of the catalyst before reduction was the same as that in Example 1. The Pt / SnO2-Sb2O3 catalyst was reduced in 10% H2-N2 mixed gas at 250°C for 2 h, and the reduced Pt / SnO2-Sb2O3 catalyst was placed at room temperature for 94 days and directly used for the reaction. Anhydrous ethanol was 5 mL, the reaction was carried out for 1.5 h, and the other reaction conditions were the same as those in Example 1. The conversion rate of 3-nitrostyrene was 100%, and the selectivity of 3-aminostyrene was 15.6%.

[0018] Comparative Example 2 Pt / SnO2-Sb2O3 reduced at 250°C catalyzing the hydrogenation of 3-nitrostyrene

[0019] The preparation process of the catalyst before reduction is the same as that of Example 1. The Pt / SnO2-Sb2O3 catalyst is reduced at 50°C for 2 h in 10% H2-N2mixed gas, directly used for the reaction, anhydrous ethanol 5 mL, reaction time 1.5 h, and other reaction conditions are the same as those of Example 1. The conversion of 3-nitrostyrene is 99.8%, and the selectivity of 3-aminostyrene is 95.2%.

[0020] Example 2 Hydrogenation of 3-nitrostyrene catalyzed by Pt / SnO2-Sb2O3 reduced at 50°C after heat treatment

[0021] The preparation process of the catalyst before reduction is the same as that of Example 1. The Pt / SnO2-Sb2O3 catalyst is reduced at 50°C for 2 h in 10% H2-N2mixed gas, directly used for the reaction, anhydrous ethanol 5 mL, reaction time 1.5 h, and other reaction conditions are the same as those of Example 1. The conversion of 3-nitrostyrene is 99.8%, and the selectivity of 3-aminostyrene is 95.2%.

[0022] Example 2 Hydrogenation of 3-nitrostyrene catalyzed by Pt / SnO2-Sb2O3 reduced at 50°C after heat treatment

[0023] The preparation process of the catalyst before reduction is the same as that of Example 1. The Pt / SnO2-Sb2O3 catalyst is reduced at 50°C for 2 h in 10% H2-N2mixed gas, directly used for the reaction, anhydrous ethanol 5 mL, reaction time 1.5 h, and other reaction conditions are the same as those of Example 1. The conversion of 3-nitrostyrene is 99.8%, and the selectivity of 3-aminostyrene is 95.2%.

[0024] Example 2 Hydrogenation of 3-nitrostyrene catalyzed by Pt / SnO2-Sb2O3 reduced at 50°C after heat treatment

[0025] The preparation process of the catalyst before reduction is the same as that of Example 1. The Pt / SnO2-Sb2O3 catalyst is reduced at 50°C for 2 h in 10% H2-N2mixed gas, directly used for the reaction, anhydrous ethanol 5 mL, reaction time 1.5 h, and other reaction conditions are the same as those of Example 1. The conversion of 3-nitrostyrene is 99.8%, and the selectivity of 3-aminostyrene is 95.2%.

[0026] Example 2 Hydrogenation of 3-nitrostyrene catalyzed by Pt / SnO2-Sb2O3 reduced at 50°C after heat treatment

[0027] The catalyst was prepared as in Example 1. The Pt / SnO2-Sb2O3 catalyst was reduced at 250°C for 2 h in 10% H2-N2mixed gas, treated in air at 100°C for 132 h, and directly used for the reaction. The reaction was carried out in 5 mL of anhydrous ethanol for 1.5 h. The other reaction conditions were the same as in Example 1. The conversion of 3-nitrostyrene was 100%, and the selectivity to 3-aminostyrene was 81.9%.

[0028] Example 4 Effect of reduction temperature in the subsequent heat treatment step of the Pt / SnO2-Sb2O3 catalyst reduced at 250°C

[0029] The catalyst was prepared as in Example 1. The Pt / SnO2-Sb2O3 catalyst was reduced at 250°C for 2 h in 10% H2-N2mixed gas, treated in air at 100°C for 16 h, and then reduced at 100°C for 2 h in 10% H2-N2mixed gas, and directly used for the reaction. The reaction was carried out for 1.5 h. The other reaction conditions were the same as in Example 1. The conversion of 3-nitrostyrene was 100%, and the selectivity to 3-aminostyrene was 93.2%.

[0030] Comparative Example 5 Effect of reduction temperature in the subsequent heat treatment step of the Pt / SnO2-Sb2O3 catalyst reduced at 250°C

[0031] The catalyst was prepared as in Example 1. The Pt / SnO2-Sb2O3 catalyst was reduced at 250°C for 2 h in 10% H2-N2mixed gas, treated in air at 100°C for 132 h, and then reduced at 250°C for 2 h in 10% H2-N2mixed gas, and directly used for the reaction. The reaction was carried out in 5 mL of anhydrous ethanol for 1.5 h. The other reaction conditions were the same as in Example 1. The conversion of 3-nitrostyrene was 48.3%, and the selectivity to 3-aminostyrene was 89.5%.

[0032] Example 5 Hydrogenation of 4-nitrostyrene catalyzed by the heat-treated Pt / SnO2-Sb2O3 catalyst reduced at 250°C

[0033] The catalyst was prepared as in Example 1. The Pt / SnO2-Sb2O3 catalyst was reduced at 250°C for 2 h in 10% H2-N2mixed gas, treated in air at 100°C for 16 h, and then reduced at 50°C for 2 h in 10% H2-N2mixed gas, and directly used for the reaction. The other reaction conditions were the same as in Example 1. The conversion of 4-nitrostyrene was 99.1%, and the selectivity to 4-aminostyrene was 93%.

Claims

1. A method for improving the activity and selectivity of a Pt / SnO2-Sb2O3 catalyst for the hydrogenation of nitrostyrene, characterized in that, The calcined Pt / SnO2-Sb2O3 catalyst is reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50-250 DEG C for 1-5 h, then heat-treated in air atmosphere at 80-150 DEG C for 2-132 h or placed at room temperature for 15-120 days, then reduced in 10% H2-N2 mixed gas or high-purity hydrogen at 50-100 DEG C for 1-5 h, and used to catalyze the hydrogenation of nitrostyrene to prepare aminostyrene in anhydrous ethanol at 1-6 MPa H2 and 35-100 DEG C; The nitrostyrene is 3-nitrostyrene and 4-nitrostyrene; The hydrogenation catalyst Pt / SnO2-Sb2O3 contains 0.5-1% of Pt, and the molar ratio of Sn to Sb is (5-90):

1.

2. A process for improving the activity and selectivity of a hydrogenation catalyst Pt / SnO2-Sb2O3 for nitrostyrene according to claim 1, characterized in that, The volume ratio of anhydrous ethanol to nitrostyrene is (5-50):1, and the mass ratio of nitrostyrene to catalyst is (1-10):

1.

3. A process for improving the activity and selectivity of a hydrogenation catalyst Pt / SnO2-Sb2O3 for nitrostyrene according to claim 1, characterized in that, The hydrogenation catalyst Pt / SnO2-Sb2O3 is prepared by the following method: a certain amount of chloroplatinic acid solution is loaded onto a SnO2-Sb2O3 carrier by impregnation, dried at 80-120 DEG C for 8-12 h, ground, sieved, and calcined at 250-500 DEG C for 3-6 h.