CN104418684A - Method for effectively maintaining high activity and high stability of catalyst - Google Patents

Abstract

The invention relates to a hydrogenation dehalogenation reaction catalyst, in particular to a method for effectively maintaining high activity and high stability of the catalyst. The catalyst is used in different reaction solvent systems to perform heterogeneous catalytic hydrodehalogenation reactions on organic halides in different reaction solvent systems at a reaction pressure of 0.05-1.0 MPa and a reaction temperature of 20-80°C; wherein, the catalyst is in the reaction solution The concentration of the solution is 20-50mg/100mL, and a basic proton absorbent is added to absorb the HCl generated in the reaction. In the invention, by changing the properties of the reaction solvent, the catalyst maintains high stability of the active agent, the hydrogenation and dehalogenation efficiency is high, the reaction conditions are mild, and the catalyst can be used repeatedly.

Description

A method to effectively maintain high catalyst activity and high stability

technical field

The invention relates to a hydrogenation dehalogenation reaction catalyst, in particular to a method for effectively maintaining high activity and high stability of the catalyst.

Background technique

As an organic synthesis method, heterogeneous catalytic hydrogenation dehalogenation has been used in the production of fine chemicals for a long time, and it has recently received more and more attention in environmental protection. Conversion of halogenated hydrocarbons into low-toxic, easily-disposable or non-toxic reusable compounds; for example, by catalytic hydrodechlorination, which can remove organic chlorinated pollutants such as chlorinated alkanes, chlorobenzenes, PCBs, etc. Chlorine atoms, converting chlorinated organic pollutants into the corresponding alkanes, benzene and biphenyl.

The usual hydrogenation catalysts use Group VIII metals (supported on supports) or complexes, and use alcohols, organic acid salts or hydrogen as hydrogen sources to carry out catalytic hydrogenation reactions. European patent (1990, EP352,164) uses Pd(OAc) ₂ as a catalyst. In the presence of PPh ₃ and NEt ₃ , chlorobenzene undergoes hydrodehalogenation reaction with hydrogen to generate benzene, and the conversion rate is only 41%. The US patent ( 1986, US4,618,686) using Pd/C as a catalyst, adding phosphate, can dechlorinate polychlorinated biphenyls; US patent (1971, US3,595,931) using Pd/Al ₂ O ₃ as a catalyst, in hydrogen oxidation In the presence of potassium, 2-chloro-p-xylene and hydrogen are subjected to gas-phase reaction of catalytic hydrodechlorination at high temperature to generate xylene, the conversion rate is close to 100%, and the conversion rate is low at low temperature; Chinese patent (2009, CN101565356A) uses The supported nickel phosphide catalyst is treated with chlorobenzene compounds at 200-400°C, and a good dechlorination and detoxification effect is obtained.

In the hydrodehalogenation reaction of organic halides, hydrogen halide will be generated, and the generation of hydrogen halide will easily poison and deactivate the catalyst, resulting in a decrease in the activity and stability of the catalyst, and finally the complete deactivation of the catalyst. Therefore, it is necessary to solve the problem of catalyst poisoning and deactivation.

Contents of the invention

The object of the present invention is to provide a method for effectively maintaining high catalyst activity and high stability.

To achieve the above object, the technical solution provided by the invention is:

A method to effectively maintain the high activity and high stability of the catalyst: the catalyst is placed in different reaction solvent systems under the reaction pressure of 0.05-1.0MPa and the reaction temperature of 20-80°C, and at the same time, a basic proton absorber is added to the different reaction solvents. The organic halides in the system undergo a heterogeneous catalytic hydrodehalogenation reaction; wherein, the concentration of the catalyst in the reaction solution is 20-50 mg/100 mL; the basic proton absorber absorbs HCl generated in the reaction;

The different reaction solvent systems are protic solvent-water two-phase solvent system or protic solvent-methanol homogeneous solvent system.

The catalyst is a catalyst in a hydrodehalogenation reaction system.

In the protic solvent-water phase solvent system or the protic solvent-methanol homogeneous solvent system, the protic solvent is mixed with the water phase solvent or the methanol homogeneous solvent respectively at a volume ratio of 20:1˜1:5.

The protic solvent is n-butanol, n-pentanol, n-hexanol, n-heptanol or n-octanol.

The volume ratio of the protic solvent to water or methanol in the reaction system is 5:1˜1:3.

The basic proton absorbent is one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, triethylamine;

The molar ratio of the basic proton absorber to the organic halide halogen substance is 1:2˜4:1.

The molar ratio of the basic proton absorber to the organic halide halogen substance is 1:1˜1.5:1.

The reaction pressure is 0.05-1.0 MPa, and the reaction temperature is 20-80°C.

The catalyst adopts transition metal as catalyst, and this type of catalyst is composed of active component and carrier. The active component is: one or more of Pd, Pt, Rh, Ru, Ni, and the active component accounts for 0.5%-5.0% of the mass fraction of the catalyst.

The present invention has the following advantages:

1. The catalyst can effectively maintain high activity and high stability. The reaction temperature and reaction pressure conditions provided by the invention are relatively mild, and at the same time, the hydrodechlorination reaction catalyst can maintain high activity and stability by adjusting the polarity of the dehalogenation reaction solvent.

2. High efficiency of hydrodechlorination reaction. The mild reaction conditions provided by the invention can make the organic halide undergo hydrogenation dehalogenation reaction, completely eliminate the halogen atoms of the organic halide, and reduce the stability and toxicity of the organic halide.

3. The reaction conditions are mild, the operating conditions are easy to control, and the cost is low.

4. In the present invention, by changing the properties of the reaction solvent, the catalyst maintains high stability of the active agent, the hydrogenation and dehalogenation efficiency is high, the reaction conditions are mild, and the catalyst can be reused.

Description of drawings

Fig. 1 is an effect diagram of the hydrodechlorination reaction of Pd/C catalyzed 4-chlorobiphenyl in reaction solutions with different properties provided by the embodiment of the present invention.

Detailed ways

The following examples are further illustrations of the present invention, but the present invention is not limited thereto.

The preparation of embodiment 1 catalyst

Dissolve 4.15g of PdCl ₂ in 200ml of 1.0mol/L dilute hydrochloric acid, add 5g of activated carbon and mix well, then add Na ₂ CO ₃ solution, adjust the pH to 10, stir for 30min, wash with deionized water several times until the filtrate No Cl ions are present. Then add 5.25g NaBH ₄ under stirring conditions for reduction for 2 hours, wash with deionized water several times until the filtrate is neutral, and dry at room temperature to obtain a 5.0% Pd/C catalyst. Palladium-nickel/carbon catalysts with different contents prepared in the same way are listed in Table 1.

Then according to the above-mentioned preparation process, except that the active component and the carrier are different, the rest of the process is the same, and the supported catalysts with different carriers and different active components can be prepared, and the prepared catalysts are listed in Table 1.

Table 1 Catalysts with different supports and different active components

The hydrodechlorination of 4-chlorobiphenyl in the protic solvent-water two-phase solvent system of embodiment 2

Take by weighing the 5.0%Pd/C catalyst that 20mg embodiment 1 prepares, join in the there-necked flask of 100ml, add the protic solvent solution 40ml that contains the 4-chlorobiphenyl that concentration is 20g/L, protic solvent is n-butanol, n-butanol, Pentanol, n-hexanol, n-heptanol or n-octanol, the volume of the aqueous phase is 40ml, sodium hydroxide is 0.188g, the reaction temperature is controlled at 40°C, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, hydrogen The flow rate is 10ml/min, and the hydrodechlorination of 4-chlorobiphenyl can be performed well in different solvents. The specific results are shown in Table 2.

Table 2 Hydrodechlorination of 4-chlorobiphenyl in protic solvent-water two-phase solvent system

protic solvent Molar ratio Cl:Pd Reaction time/min Dechlorination efficiency% Butanol 452:1 90 100 n-pentanol 452:1 90 100 n-Hexanol 452:1 90 98.1 n-Heptanol 452:1 90 95.3 n-octanol 452:1 90 93.2

Example 3 The influence of temperature on the hydrodechlorination of 4-chlorobiphenyl in protic solvent-water two-phase solvent system

Take by weighing the 5.0%Pd/C catalyst that 20mg embodiment 1 prepares, join in the there-necked flask of 100ml, add the protic solvent solution 40ml that contains the 4-chlorobiphenyl that concentration is 20g/L, protic solvent is n-butanol, n-butanol, Pentanol, n-hexanol, n-heptanol or n-octanol, the volume of the aqueous phase is 40ml, sodium hydroxide 0.188g, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, and the hydrogen flow rate is 10ml/min. 4-Chlorobiphenyl can be reductively dechlorinated well at different temperatures such as 20°C, 30°C, 40°C, and 50°C. The specific results are shown in Table 3.

Table 3 Hydrodechlorination of PCBs at different temperatures

temperature/℃ solvent Molar ratio Cl:Pd Reaction time/min Dechlorination efficiency% 20 n-butanol-water 452:1 90 85.3 30 n-butanol-water 452:1 90 98.8 40 n-butanol-water 452:1 90 100 50 n-butanol-water 452:1 90 100 20 n-Pentanol-Water 452:1 90 81.7 30 n-Pentanol-Water 452:1 90 95.9 40 n-Pentanol-Water 452:1 90 100 50 n-Pentanol-Water 452:1 90 100

The hydrodechlorination of 4-chlorobiphenyl in the protic solvent-methanol homogeneous solvent system of embodiment 4

Take by weighing the 5.0%Pd/C catalyst that 20mg embodiment 1 prepares, join in the there-necked flask of 100ml, add the protic solvent solution 40ml that contains the 4-chlorobiphenyl that concentration is 20g/L, protic solvent is n-butanol, n-butanol Pentanol, n-hexanol, n-heptanol or n-octanol, the volume of methanol is 40ml, sodium hydroxide is 0.188g, the reaction temperature is controlled at 40°C, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, and the hydrogen flow rate is The hydrodechlorination of 4-chlorobiphenyl can be performed well in different solvents, and the specific results are shown in Table 4.

Table 4 Hydrodechlorination of PCBs at different concentrations

solvent Molar ratio Cl:Pd Reaction time/min Dechlorination efficiency% n-Butanol-Methanol 452:1 120 100 n-Pentanol-Methanol 452:1 120 99.9 n-Hexanol-Methanol 452:1 120 97.1 n-Heptanol-Methanol 452:1 120 91.2 n-octanol-methanol 452:1 120 88.7

The impact of embodiment 5 n-butanol on the stability of 4-chlorobiphenyl hydrodechlorination catalyst

Take by weighing the 5.0%Pd/C catalyst that 25mg embodiment 1 prepares, join in the there-necked flask of 100ml, add the n-butanol solution 80ml that contains the 4-chlorobiphenyl that concentration is 10g/L, sodium hydroxide 0.188g, react The temperature is controlled at 40°C, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, the hydrogen flow rate is 10ml/min, and the reaction is 2.5h. In the reaction, the catalyst was reused 10 times in this way, and the results of the reuse of the catalyst in n-butanol are shown in Figure 1.

The impact of embodiment 6 n-butanol-methanol on the stability of 4-chlorobiphenyl hydrodechlorination catalyst

Weigh 25 mg of the 5.0% Pd/C catalyst prepared in Example 1, add it to a 100 ml three-necked flask, add 40 ml of n-butanol solution containing 20 g/L of 4-chlorobiphenyl, 40 ml of methanol, and 0.188 g of sodium hydroxide g, the reaction temperature is controlled at 40°C, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, the hydrogen flow rate is 10ml/min, and the reaction is 2.5h. In the next reaction, the catalyst was reused 10 times in this way, and the results of the reuse of the catalyst in n-butanol-methanol are shown in Figure 1.

Embodiment 7 The impact of n-butanol-water on the stability of 4-chlorobiphenyl hydrodechlorination catalyst

Weigh 25mg of the 5.0%Pd/C catalyst prepared in Example 1, join in a 100ml three-necked flask, add 40ml of n-butanol solution containing 20g/L of 4-chlorobiphenyl, 40ml of water, and 0.188 g of sodium hydroxide g, the reaction temperature is controlled at 40°C, the stirring speed of the magnetic stirrer is 300r/min, the reaction pressure is normal pressure, the hydrogen flow rate is 10ml/min, and the reaction is 2.5h. In the next reaction, the catalyst was reused 10 times in this way, and the results of the reuse of the catalyst in n-butanol-methanol are shown in Figure 1.

The other catalysts described in the above-mentioned Example 1, as well as the catalysts obtained by the prior art that can be used in the hydrodehalogenation reaction system, can be used in the protic solvent-water two-phase solvent system or the protic solvent-methanol homogeneous The halogen atom of the organic halide is completely eliminated in the solvent system, the stability and toxicity of the organic halide are reduced, and the catalyst can maintain high active agent and stability, and can be reused at the same time.

Claims (9)

1. effectively keep a method for high activity of catalyst and high stability, it is characterized in that:

By catalyzer in differential responses solvent system under 0.05 ~ 1.0MPa reaction pressure, 20 ~ 80 DEG C of temperature of reaction, add alkaline proton absorbent simultaneously and then the heterogeneous catalytic hydrogenation dehalogenation reaction carried out to the organic halogen in differential responses solvent system; Wherein, the concentration of catalyzer in reaction soln is 20 ~ 50mg/100mL;

Differential responses solvent system is protonic solvent-water two phase solvent system or protonic solvent-methyl alcohol homogeneous solvent system.

2. press the method for effective maintenance high activity of catalyst according to claim 1 and high stability, it is characterized in that: described catalyzer is the catalyzer in hydrodehalogenation reaction system.

3. press the method for effective maintenance high activity of catalyst according to claim 1 and high stability, it is characterized in that: protonic solvent all mixes with aqueous phase solvent or methyl alcohol homogeneous solvent by the volume ratio of 20:1 ~ 1:5 by described protonic solvent-aqueous phase solvent system or protonic solvent-methyl alcohol homogeneous solvent system respectively.

4., by the method for effective maintenance high activity of catalyst described in claim 1 or 3 and high stability, it is characterized in that: described protonic solvent is propyl carbinol, Pentyl alcohol, n-hexyl alcohol, n-Heptyl alcohol or n-Octanol.

5. press the method for effective maintenance high activity of catalyst according to claim 3 and high stability, it is characterized in that: in described reaction system, the volume ratio of protonic solvent and water or methyl alcohol is 5:1 ~ 1:3.

6. by the method for effective maintenance high activity of catalyst according to claim 1 and high stability, it is characterized in that: described alkaline proton absorbent is one or more in lithium hydroxide, sodium hydroxide, potassium hydroxide, ammoniacal liquor, triethylamine.

7. press the method for effective maintenance high activity of catalyst according to claim 6 and high stability, it is characterized in that: described alkaline proton absorbent and organic halogen halogen species mol ratio are 1:2 ~ 4:1.

8. press the method for effective maintenance high activity of catalyst according to claim 7 and high stability, it is characterized in that: described alkaline proton absorbent and organic halogen halogen species mol ratio are 1:1 ~ 1.5:1.

9. press the method for effective maintenance high activity of catalyst according to claim 1 and high stability, it is characterized in that: described reaction pressure is 0.05 ~ 1.0MPa, temperature of reaction is 20 ~ 80 DEG C.