CN111003787B

CN111003787B - Method for efficiently reducing and defluorinating perfluorinated compounds by virtue of bimetallic concerted catalysis

Info

Publication number: CN111003787B
Application number: CN201911310685.9A
Authority: CN
Inventors: 马宣宣; 李晓涵; 李天成; 刘苏静; 刘莺; 夏传海
Original assignee: Ludong University
Current assignee: Ludong University
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2022-05-06
Anticipated expiration: 2039-12-18
Also published as: CN111003787A

Abstract

The invention relates to a treatment method of perfluorinated compounds, in particular to a method for efficiently reducing and defluorinating perfluorinated compounds by virtue of bimetallic concerted catalysis. The method adopts a supported synergistic catalyst with Rh and Ni as active components and hydrogen as a hydrogen source to perform reduction defluorination reaction on perfluorinated compounds in the presence of a strong alkaline proton absorbent. The method effectively exerts the synergistic catalytic advantages of the two active metal components, improves the catalytic performance and the stability of the material, and has the advantages of high efficiency, mild reaction conditions, easy control of operation, low cost and good production and practical values.

Description

Method for efficiently reducing and defluorinating perfluorinated compounds by virtue of bimetallic concerted catalysis

Technical Field

The invention relates to a treatment method of perfluorinated compounds, in particular to a method for efficiently reducing and defluorinating perfluorinated compounds by virtue of bimetallic concerted catalysis.

Background

Perfluoro compounds (PFCs) have unique physicochemical properties and are widely applied to the fields of textile, paper making, packaging, pesticides, fire extinguishing foams and the like. Due to the mass production and use of perfluorinated compounds, the compounds can be detected in the atmosphere, soil, water, sediments, animals and plants, and can be detected in domestic water, human serum and milk, thereby attracting the attention of researchers in various countries. The covalent bond of C-F in the perfluorinated compounds has extremely high chemical bond energy, so the compounds generally have high stability, can endure strong ultraviolet irradiation, heating, chemical action, metabolism of microorganisms and higher animals, are difficult to degrade, can be enriched and amplified in organisms through the transmission of food chain, and must be reduced and controlled from the source.

Various researchers have studied methods for reducing and eliminating the harm of perfluoro compounds, and currently, the treatment methods mainly include physical methods, biological methods, chemical methods and the like, and the treatment methods have advantages and disadvantages. The physical method has low cost, easy operation and wide application range, but only realizes the effect of substance phase separation and does not achieve the aim of eliminating the toxicity of pollutants. The biological method has the obvious advantages of mild treatment conditions, low running cost, simple process, convenient operation and management and the like, but has complex degradation process and incomplete degradation and is easily influenced by molecular structures and external environmental factors. Chemical methods are one of the effective means for reducing the toxicity and durability of the perfluorinated compounds, and mainly comprise incineration methods, advanced oxidation methods and chemical reduction methods. Incineration and advanced oxidation have achieved relatively good degradation and defluorination rates, but may generate short-chain perfluorocarboxylic acids or dioxin and other toxic substances, and there is still a long way to completely realize the harmless treatment of perfluorocompounds. The heterogeneous catalytic reduction method can realize the removal of fluorine atoms in the perfluorinated compounds, reduce the toxicity, stability and biological difficult degradation of the perfluorinated compounds, and simultaneously, the catalytic materials and the defluorinated products can be recycled, so the method is considered to be a method for reducing the perfluorinated compounds with better development prospect, and has attracted extensive attention of researchers in various countries. The C-F bond in perfluorocompounds is a highly stable chemical bond compared to other organohalogenated contaminants, and thus their selective activation and conversion under mild conditions remains challenging. For heterogeneous catalytic reduction, the efficient and stable catalytic material is the key to the defluorination and degradation of the perfluorinated compounds. Therefore, the development of a new and efficient heterogeneous catalytic reduction material and system for the reductive defluorination and degradation of perfluoro compounds is urgently needed.

Aiming at the reduction treatment of organic fluoro-compounds, the existing catalytic material is mainly a homogeneous catalytic material. Sabater et al synthesized a Ru-Pd composite homogeneous catalyst and achieved reductive defluorination of organic fluorides by the homogeneous catalyst. In addition, there are also researchers using NiCl₂Or NiCl₂(PCy₃)₂In LiEt₃The reductive defluorination of organic fluoro-compounds is realized in the presence of BH. However, homogeneous catalysis has the problems of difficult catalyst recovery and poor reutilization while showing good catalytic effect. Furthermore, Yu and Chiu investigated fluoroethylene in Rh/Al₂O₃The reduction reaction process under catalysis discovers Rh/Al₂O₃Can catalyze fluoroethylene to effectively reduce and defluorinate. Although heterogeneous catalyst Rh/Al₂O₃The p-fluorobenzene and the fluoroethylene show better catalytic activity, but the stability and the applicability of the p-fluorobenzene and the fluoroethylene are not clear, particularly for perfluorThe catalytic degradation activity of the compounds is yet to be studied. Lee et al, using the Zn0-VB 12-titanium (III) citrate system, achieved partial defluorination degradation of branched perfluorooctanesulfonic acids and branched perfluorohexanesulfonic acids, yet their catalytic activity remained to be further improved. However, no document or patent reports on the use of supported bimetallic catalysts as co-catalytic materials to degrade perfluorinated compounds by heterogeneous catalytic reductive defluorination.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for efficiently reducing and defluorinating perfluorinated compounds by using bimetallic concerted catalysis.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for efficiently reducing and defluorinating perfluorinated compounds by bimetal concerted catalysis has the following reaction formula:

in the formula: r ═ COOH, SO₃H，SO₃ ^-，SO₂F；n＝4-8；

The method adopts a supported synergistic catalyst with Rh and Ni as active components and hydrogen as a hydrogen source to perform reduction defluorination reaction on perfluorinated compounds in the presence of a strong alkaline proton absorbent.

The perfluorinated compound is subjected to heterogeneous catalytic reduction defluorination reaction in the presence of a strong basic proton absorbent by using hydrogen (10-30mL/min) as a hydrogen source at the temperature of 30-80 ℃ under the pressure of 0.1-1.0 MPa through a supported synergistic catalyst; the addition amount of the supported synergistic catalyst is 2.0-5.0% of the addition mass of the perfluorinated compounds.

The supported synergistic catalyst is an active component and a carrier; the active components are Rh and Ni, the Ni accounts for 6.0-10.0% of the mass fraction of the catalyst, the Rh accounts for 2.0-4.0% of the mass fraction of the catalyst, and the carrier is activated carbon, ferroferric oxide or aluminum oxide.

The strong basic proton absorbent is alkali metal hydroxide; wherein the molar ratio of the strong-basicity proton absorbent to the fluorine atoms in the perfluorinated compounds is 3.0/1-1.5/1.

The alkali metal hydroxide is LiOH, NaOH, KOH, RbOH or CsOH.

Dissolving the perfluorinated compound by the mixed solution; wherein the mixed solution is prepared by mixing alcohol and water, and the concentration of the alcohol/(alcohol + water) is 5-25%

The alcohol is ethanol, ethylene glycol, isopropanol or 1, 3-propylene glycol.

The supported Rh-Ni co-catalyst takes Rh and Ni as two active components and is prepared by the following method: the supported synergistic catalyst takes Rh and Ni as two active components, and takes [ Ni (NH)₃)₆]Cl₂Dissolving with water, adjusting the pH value of the solution to be alkaline, adding pretreated Activated Carbon (AC) into a reaction system under stirring, and adding hydrazine hydrate under stirring to react to obtain a Ni/AC catalyst; will [ Rh (NH)₃)₅]Cl₃Dissolving the mixture in water, adjusting the pH value of the solution to be alkaline, adding the Ni/AC catalyst under magnetic stirring, and adding hydrazine hydrate under stirring to react to obtain the Ni @ Rh/AC bimetallic catalyst.

Further, a certain amount of [ Ni (NH) ] is added into a three-neck flask₃)₆]Cl₂Dissolving the mixture by water, adjusting the pH value of the solution to be about 11.5, adding pretreated Activated Carbon (AC) into the reaction system under magnetic stirring, continuously stirring for 2.0h, adding hydrazine hydrate under stirring, continuously reacting for 1.5h, washing the mixture for a plurality of times by distilled water and absolute ethyl alcohol respectively, and drying the mixture in vacuum to obtain the Ni/AC catalyst. Then a certain amount of [ Rh (NH) is added into a three-neck flask₃)₅]Cl₃Dissolving the mixture by water, adjusting the pH value of the solution to be about 11.5, adding the Ni/AC catalyst under magnetic stirring, continuously stirring for 2.0h, adding hydrazine hydrate under stirring, continuously reacting for 1.5h, washing the mixture by distilled water and absolute ethyl alcohol for a plurality of times respectively, and drying the mixture in vacuum to obtain the Ni @ Rh/AC bimetallic catalyst.

Compared with the prior art, the method of the invention has the advantages that:

1. the treatment method is simple to prepare and does not need other special equipment; 2. the supported synergistic catalyst used in the catalytic reduction defluorination reaction has higher catalytic activity and anti-toxicity performance, the catalyst dosage is less, and the stability and toxicity of the reaction product are greatly reduced; 3. the reaction time is shortened, the cost is reduced, the production and practical values are better, and the perfluorinated compounds can be quickly and efficiently treated; 4. the method for catalytically treating the perfluorinated compounds solves the problems of low degradation efficiency, incomplete degradation and the like in the prior art, and has the advantages of mild conditions, short reaction time, high efficiency and convenient subsequent purification.

Drawings

FIG. 1 is a diagram showing the effect of the catalyst recycling reaction performance in the perfluorooctanoic acid reduction defluorination according to the embodiment of the present invention.

Detailed Description

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

The invention provides a treatment method for carrying out heterogeneous catalytic reduction defluorination on a perfluorinated compound sample under relatively mild conditions, which comprises the steps of firstly adding a mixed solution of a perfluorinated compound for dissolution, adding a supported synergistic catalyst, using hydrogen as a hydrogen source, and carrying out catalytic reduction defluorination on the perfluorinated compound in the presence of a strong alkaline proton absorbent, wherein the reaction pressure is 0.1-1.0 MPa, and the reaction temperature is controlled at 30-80 ℃.

The invention relates to a method for efficiently reducing and defluorinating perfluorinated compounds by bimetal concerted catalysis, wherein a reaction system used for reducing and defluorinating, namely alcohol in an alcohol-water mixed solvent system formed by the reaction system and water is one of methanol, ethanol, ethylene glycol, isopropanol and 1, 3-propylene glycol.

The method effectively exerts the synergistic catalytic advantages of the two active metal components, improves the catalytic performance and the stability of the material, has high efficiency, mild reaction conditions, easy control of operation and low cost, and has good production and practical values.

Example 1 preparation of a heterogeneous catalytic reduction defluorination catalyst

A three-neck flask was taken, and 5.21g of [ Ni (NH) ] was added₃)₆]Cl₂Dissolving in water, adjusting pH to about 11.5, adding pretreated Active Carbon (AC)20g into the reaction system under magnetic stirring, and continuingStirring for 2.0h, adding hydrazine hydrate while stirring, continuously reacting for 1.5h, washing with distilled water and absolute ethyl alcohol for several times respectively, and drying in vacuum to obtain the 6% Ni/AC catalyst. Then, 1.26g of [ Rh (NH) ] is added into a three-neck flask₃)₅]Cl₃Dissolving with water, adjusting pH to about 11.5, adding the Ni/AC catalyst under magnetic stirring, stirring for 2.0 hr, adding hydrazine hydrate under stirring, reacting for 1.5 hr, washing with distilled water and anhydrous ethanol for several times, and vacuum drying to obtain Ni_0.06@Rh_0.02a/AC bimetallic catalyst; method for preparing synergetic bimetallic Ni @ Rh/Fe₃O₄And Ni @ Rh/Al₂O₃Co-catalyst, Ni/AC and Rh/AC single metal component catalysts were prepared in the same way. The different levels of bimetallic catalyst are listed in table 1.

TABLE 1 synergistic catalysts with different supports and different active ingredient contents

Example 2 Effect of different synergistic catalysts on the reductive defluorination of Perfluorooctanoic acid

50mg of the catalyst prepared in example 1 was weighed and charged in a 100mL three-necked flask, 80mL of a 2g/L perfluorooctanoic acid 10% 1, 3-propanediol aqueous solution (V (1, 3-propanediol)/V (water) ═ 10/90) was charged, and hydrogen gas was used as a hydrogen source (H)₂: 20mL/min), carrying out catalytic reduction defluorination treatment on the perfluorooctanoic acid in the liquid phase in the presence of inorganic base NaOH, wherein the ratio of the amount of the inorganic base NaOH to the amount of fluorine elements in a reaction substrate is 1.5:1, the reaction pressure is 0.1MPa, the reaction temperature is 45 ℃, and the specific reduction defluorination result is shown in Table 2.

TABLE 2 catalytic reduction defluorination degradation of perfluorooctanoic acid by different catalytic materials

Serial number	Reaction substrate	Catalyst and process for preparing same	Reaction time	Efficiency of defluorination
					1	Perfluorooctanoic acid	Ni_0.06@Rh_0.02/AC	360min	86.1％
2	Perfluorooctanoic acid	Ni_0.08@Rh_0.02/AC	360min	97.3％
					3	Perfluorooctanoic acid	Ni_0.10@Rh_0.02/AC	360min	100％
4	Perfluorooctanoic acid	Ni_0.08@Rh_0.02/AC	360min	100％
					5	PerfluorooctanesAcid(s)	Ni_0.08@Rh_0.03/AC	360min	100％
6	Perfluorooctanoic acid	Ni_0.08@Rh_0.04/AC	360min	100％
					7	Perfluorooctanoic acid	10％Ni/AC	360min	57.2％
8	Perfluorooctanoic acid	10％Rh/AC	360min	64.3％
					9	Perfluorooctanoic acid	Ni_0.08@Rh_0.03/Fe₃O₄	480min	100％
10	Perfluorooctanoic acid	Ni_0.08@Rh_0.03/Al₂O₃	480min	100％

Example 3 different base pairs Ni_0.08@Rh_0.03Influence of/AC (alternating current) synergistic catalyst on reduction and defluorination of perfluorooctanoic acid

50mg of the Ni0.08@ Rh0.03/AC cocatalyst prepared in example 1 was weighed into a 100mL three-necked flask, and 80mL of a 2 g/L10% aqueous solution of perfluorooctanoic acid (V (1, 3-propanediol)/V (water) ═ 10/90) of 1, 3-propanediol was added, and hydrogen gas was used as a hydrogen source (H) (H, 3-propanediol)/V (water) ═ 10/90)₂: 20mL/min), carrying out catalytic reduction defluorination treatment on the perfluorooctanoic acid in the liquid phase in the presence of strong base, wherein the ratio of the amount of the base to the amount of fluorine in the reaction substrate is 1.5:1, the reaction pressure is 0.1MPa, the reaction temperature is 45 ℃, and the specific reduction defluorination result is shown in Table 3.

TABLE 3 Ni in the Presence of different bases_0.08@Rh_0.03AC (alternating current) catalyzed multi-phase catalytic reduction defluorination treatment of perfluorooctanoic acid

Serial number	Reaction substrate	Alkali	n (alkali)/n (F)	Reaction time	Efficiency of defluorination
						1	Perfluorooctanoic acid	LiOH	1.5	360min	96.2％
2	Perfluorooctanoic acid	NaOH	1.5	360min	100％
						3	Perfluorooctanoic acid	KOH	1.5	360min	100％
4	Perfluorooctanoic acid	RbOH	1.5	360min	100％
						5	Perfluorooctanoic acid	NaOH	1.0	360min	89.8％
6	Perfluorooctanoic acid	NaOH	2.5	360min	100％
						7	Perfluorooctanoic acid	NaOH	3.5	360min	100％

Example 4, Ni_0.08@Rh_0.02Reduction defluorination treatment under catalysis of/AC (alternating current) synergistic catalyst

50mg of Ni prepared in example 1 were weighed_0.08@Rh_0.02The catalyst/AC synergistic catalyst or 10% Ni/AC, 10% Rh/AC, into a 100mL three-necked flask, 80mL of a 10% 1, 3-propanediol-water solution (V (1, 3-propanediol)/V (water) ═ 10/90) containing perfluorooctanoic acid with a fluorine atom concentration of 72mmol/L, and hydrogen as a hydrogen source (H/L)₂: 20mL/min), carrying out catalytic reduction defluorination treatment on the perfluorooctanoic acid in the liquid phase in the presence of strong base NaOH, wherein the ratio of the amount of the base to the amount of fluorine elements in a reaction substrate is 1.5:1, the reaction pressure is 0.1MPa, the reaction temperature is 45 ℃, centrifugally recovering the catalyst after 360min of reaction, carrying out the next reaction, repeatedly reacting for ten times, and comparing the recycling performance of the catalyst, wherein the specific result is shown in figure 1.

As can be seen from FIG. 1, Ni_0.08@Rh_0.02The catalytic activity and stability of the/AC catalyst on the reduction defluorination of the perfluorooctanoic acid are far higher than those of two single metal catalysts, namely 10 percent Ni/AC and 10 percent Rh/AC, which shows that the bimetallic synergistic catalyst prepared by the invention exerts the synergistic catalytic advantages of the two active metal components and improves the catalytic performance and stability of the material.

Example 5 different perfluor compounds in Ni_0.08@Rh_0.03Reduction defluorination treatment under catalysis of/AC (alternating current) synergistic catalyst

50mg of Ni prepared in example 1 were weighed_0.08@Rh_0.03Adding the/AC synergistic catalyst into a 100mL three-neck flask, and adding the fluorine source80mL of a 10% 1, 3-propanediol-water solution (V (1, 3-propanediol)/V (water) ═ 10/90) having a concentration of 72mmol/L of perfluoro compound, and hydrogen gas was used as a hydrogen source (H)₂: 20mL/min), carrying out catalytic reduction defluorination treatment on the perfluorinated compounds in the liquid phase in the presence of strong base NaOH, wherein the ratio of the amount of the base to the amount of fluorine elements in a reaction substrate is 1.5:1, the reaction pressure is 0.1MPa, the reaction temperature is 45 ℃, and the specific reduction defluorination result is shown in Table 4.

TABLE 4 different perfluorinated compounds in Ni_0.08@Rh_0.03Reduction defluorination treatment under catalysis of/AC (alternating current) synergistic catalyst

Serial number	Reaction substrate	Alkali	Reaction time	Efficiency of defluorination
					1	Perfluorobutyric acid	NaOH	360min	100％
2	Perfluorohexanoic acid	NaOH	360min	100％
					3	Perfluorooctanoic acid	NaOH	360min	100％
4	Perfluorooctanesulfonic acid	NaOH	480min	100％

In conclusion, the supported synergistic catalyst used in the method for efficiently reducing and defluorinating the perfluorinated compounds by the bimetallic synergistic catalysis has higher catalytic activity and anti-toxicity performance, the dosage of the catalyst is less, and the stability and toxicity of reaction products are greatly reduced; the method effectively shortens the reaction time, reduces the cost, has better production and practical values, and can quickly and efficiently treat the perfluorinated compounds.

Claims

1. A method for efficiently reducing and defluorinating perfluorinated compounds by bimetallic concerted catalysis is characterized by comprising the following steps: the reaction formula is as follows:

in the formula: r ═ COOH, SO₃H，SO₃ ^-，SO₂F；n＝4-8；

2. The method for the efficient reductive defluorination of perfluorinated compounds by means of bimetallic concerted catalysis as claimed in claim 1, wherein: the perfluorinated compound is subjected to heterogeneous catalytic reduction defluorination reaction in the presence of a strong basic proton absorbent by using hydrogen (10-30mL/min) as a hydrogen source at the temperature of 30-80 ℃ under the pressure of 0.1-1.0 MPa through a supported synergistic catalyst; the addition amount of the supported synergistic catalyst is 2.0-5.0% of the addition mass of the perfluorinated compounds.

3. The method for the efficient reductive defluorination of perfluorinated compounds by means of bimetallic concerted catalysis as claimed in claim 1, wherein: the supported synergistic catalyst is an active component and a carrier; the active components are Rh and Ni, the Ni accounts for 6.0-10.0% of the mass fraction of the catalyst, the Rh accounts for 2.0-4.0% of the mass fraction of the catalyst, and the carrier is activated carbon, ferroferric oxide or aluminum oxide.

4. The process for the highly efficient reductive defluorination of perfluorinated compounds in combination with bimetallic co-catalysis as set forth in claim 2, wherein said strongly basic proton absorbent is an alkali metal hydroxide; wherein the molar ratio of the strong-basicity proton absorbent to the fluorine atoms in the perfluorinated compounds is 3.0/1-1.5/1.

5. The method for efficient reductive defluorination of perfluorinated compounds in coordination with bimetallic catalysis of claim 4, wherein said alkali metal hydroxide is LiOH, NaOH, KOH, RbOH or CsOH.

6. The method for the bimetallic concerted catalysis perfluorinated compound high-efficiency reduction defluorination according to the claim 2, wherein the perfluorinated compound is dissolved by a mixed solution; wherein, the mixed solution is formed by mixing alcohol and water (5-25 percent of alcohol/(alcohol + water)).

7. The method for efficient reductive defluorination of perfluorinated compounds according to claim 6, wherein said alcohol is ethanol, ethylene glycol, isopropanol or 1, 3-propanediol.

8. The method for the high-efficiency reductive defluorination of perfluorinated compounds by means of bimetallic concerted catalysis in accordance with claim 1 or 2The method is characterized in that the supported synergistic catalyst takes Rh and Ni as two active components and takes [ Ni (NH)₃)₆]Cl₂Dissolving with water, adjusting the pH value of the solution to be alkaline, adding pretreated Activated Carbon (AC) into a reaction system under stirring, and adding hydrazine hydrate under stirring to react to obtain a Ni/AC catalyst; will [ Rh (NH)₃)₅]Cl₃Dissolving the mixture in water, adjusting the pH value of the solution to be alkaline, adding the Ni/AC catalyst under magnetic stirring, and adding hydrazine hydrate under stirring to react to obtain the Ni @ Rh/AC bimetallic catalyst.