Catalytic hydrogenation dehalogenation method for haloacetic acid or halomethane in water body

Abstract

The invention discloses a method for catalytically hydrogenating and dehalogenating haloacetic acid or halomethane in a water body, which comprises the following steps of: catalytically hydrogenating and dehalogenating haloacetic acid or halomethane in the water body into acetic acid or methane by taking a ruthenium or platinum-containing material as a catalyst and hydrogen as a reducing agent; the noble metal in the catalyst is cheaper, and the unit price of ruthenium is far lower than that of palladium and rhodium; according to the method, the dehalogenation selectivity is higher, and compared with a palladium catalyst, the selectivity of hydrodechlorinating trichloroacetic acid in a water body into acetic acid is improved by 10.3%-15.5%; and the selectivity of trichloromethane hydrodechlorination into methane is improved by 8.6%-10.0%.

Description

(I) Technical field

[0001] The invention belongs to the field of water treatment and relates to a method for treating haloacetic acid or methyl halide in water, specifically a method for catalytically hydrogenating and dehalogenating haloacetic acid or methyl halide in water into acetic acid or methane by using a ruthenium or platinum-containing material as a catalyst and hydrogen as a reducing agent. (II) Background technology

[0002] Haloacetic acids and halomethanes are common halogen-containing organic pollutants in drinking water, surface water and groundwater. These two types of pollutants are characterized by low concentration, high toxicity and difficulty in treatment. If they are not controlled or treated, they will cause great harm to the ecological environment and human health. The catalytic hydrogenation method using palladium-containing materials as catalysts and hydrogen as a reducing agent can remove haloacetic acids and trihalomethanes from water at room temperature and pressure, but this method has the problem of incomplete dehalogenation. Taking the catalytic hydrogenation and dechlorination of trichloroacetic acid in water as an example, the current catalytic hydrogenation method usually produces a high proportion of monochloroacetic acid as the final product [Water Research 192 (2021) 116841], and the toxicity of monochloroacetic acid is nearly 50 times that of trichloroacetic acid [Fundam. Appl. Toxicol. 17, 240–253 (1991)].

[0003] The existing method discloses an electrochemical catalytic hydrogenation method using a rhodium-containing material as a catalyst. The hydrogen in this method is generated in situ by electrolysis of water, and various haloacetic acids can be highly selectively dehalogenated to acetic acid [Nature Water, 2023, 1(1): 95-103]. However, the rhodium in the catalyst used in this method is too expensive and difficult to apply on a large scale. Therefore, it is necessary to find a low-cost and efficient dehalogenation method. (III) Summary of the invention

[0004] The present invention aims to provide a method for catalytically dehalogenating haloacetic acid or halomethyl ethane in water, wherein haloacetic acid or halomethyl ethane in water is dehalogenated to acetic acid or methane by using a ruthenium or platinum-containing material as a catalyst and hydrogen as a reducing agent. This method can not only reduce the unit price of precious metals, but also has the advantage of high dehalogenation selectivity and can be applied on a large scale.

[0005] The technical solution adopted by the present invention is:

[0006] The invention provides a method for catalytically dehalogenating haloacetic acid or halomethyl ethane in water. The method uses a ruthenium- or platinum-containing material as a catalyst, hydrogen as a reducing agent, and water containing haloacetic acid or halomethyl ethane as a treatment object to dehalogenate haloacetic acid or halomethyl ethane in the water into acetic acid or methane.

[0007] Furthermore, the haloacetic acid includes trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, dibromoacetic acid, and monobromoacetic acid; the halogenated methane includes chloroform, dichloromethane, chloromethane, bromodichloromethane, bromoform, and dibromochloromethane.

[0008] Furthermore, the catalyst is a supported catalyst prepared by loading ruthenium or platinum on a carrier, and the carrier can be any solid material with stable chemical properties under the reaction conditions, including carbon materials, metal materials, metal oxide materials, ceramic materials or polymer materials.

[0009] Furthermore, the carbon material includes activated carbon, carbon fiber, graphite felt, foamed glassy carbon, etc.; the metal material includes nickel, titanium, copper, silver, stainless steel, etc.; the metal oxide material includes aluminum oxide, titanium oxide, cerium oxide, etc.

[0010] Furthermore, the catalyst is Ru / C, Ru / Al2O3, Ru / Ni, Pt / C, Pt / Al2O3, or Pt / Cu.

[0011] Furthermore, the temperature range of the hydrodehalogenation reaction is 5-90°C.

[0012] Furthermore, the concentration of the haloacetic acid or methyl halide in the water body is in the range of 10 μg / L to 1 g / L, preferably 3 mg / L.

[0013] Furthermore, the water body includes drinking water, surface water or groundwater.

[0014] The content of ruthenium or platinum in the catalyst is not a critical factor of the present invention and can be varied according to the concentration of haloacetic acid and methyl halide; preferably, the mass loading of ruthenium or platinum is 0.1-10%, more preferably 5%.

[0015] Furthermore, the amount of the catalyst is 10-30 mg / L (preferably 20 mg / L) based on the volume of the water containing the halogenated acetic acid or methyl halide, and the hydrogen flow rate is 30-70 mL / min, preferably 50 mL / min.

[0016] The method for catalytic hydrogenation dehalogenation of haloacetic acid or methyl halide in water of the present invention is carried out according to the following steps: using a three-necked flask as a reactor, firstly adding a catalyst into a water body containing haloacetic acid or methyl halide, introducing nitrogen with a flow rate of 50 mL / min into the water body under the conditions of pH=7.2 and a temperature of 5-90° C. (preferably 25° C.), switching the nitrogen to hydrogen with an equal flow rate after 10 minutes to start the reaction (preferably after 60 minutes of reaction), and hydrogenating and dehalogenating the haloacetic acid or methyl halide in the water body into acetic acid or methane.

[0017] The source and method of hydrogen introduction are not critical factors. Hydrogen can come from hydrogen produced by water electrolysis or from petrochemical hydrogen. When hydrogen is introduced into the water to be treated, it can be dispersed in various ways, such as through a porous membrane, ultrasonic treatment, mechanical stirring, etc.

[0018] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: (1) the price of precious metals in the catalyst is cheaper, and the unit price of ruthenium is much lower than that of palladium and rhodium; (2) the dehalogenation selectivity is higher. Compared with the palladium catalyst, the selectivity of trichloroacetic acid in water to form acetic acid by hydrogenation dechlorination is increased by 10.3% to 15.5%; the selectivity of trichloromethane to form methane by hydrogenation dechlorination is increased by 8.6% to 10.0%; (3) the method of the present invention is easy to apply on a large scale, which is conducive to the realization of industrial production; (4) compared with the electrochemical method, the equipment is simpler and the cost is lower. (IV) Description of the drawings

[0019] Figure 1 , ion chromatogram of the reaction solution before and after the reaction. (V) Specific implementation methods

[0020] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0021] In the following examples, the noble metal-containing catalysts were provided by Sigma-Aldrich unless otherwise specified.

[0022] Conversion rate Yield Selectivity Where C0 is the initial reactant molar concentration, C1 is the reactant molar concentration at the end of the reaction, and C2 is the target product molar concentration at the end of the reaction.

[0023] Example 1: Hydrodechlorination of trichloroacetic acid in tap water

[0024] Using a three-necked flask as a reactor, firstly, 2 mg of ruthenium carbon (Ru / C, Ru mass content is 5 wt%, product number 206180) catalyst was added to 100 mL of tap water containing 3 mg / L trichloroacetic acid (pH = 7.2, temperature = 25 ° C), and the reaction solution was sampled for ion chromatography before the reaction started, and then nitrogen with a flow rate of 50 mL / min was introduced into the tap water. After 10 minutes, the nitrogen was switched to hydrogen with the same flow rate to start the reaction. After 60 minutes of reaction, the reaction solution was sampled for ion chromatography. The results are shown in FIG. Figure 1 , the conversion rate of trichloroacetic acid in tap water = 100%, the yield of acetic acid = 98.1%, and the selectivity of acetic acid 98.1%.

[0025] Ion chromatography analysis conditions: Dionex ICS-2100 ion chromatograph, Dionex Ion Pac AG19 anion protection column (50mm×4mm) and Ion Pac AS19 anion separation column (250mm×4mm); ASRS-ULTRA anion suppressor (4mm); eluent: KOH isocratic elution, gradient program is 0-40min, 8mmol / L; flow rate: 1mL / min; injection volume: 25μL; column temperature: 30℃; detection cell temperature: 35℃; suppressor current 20mA; conductivity detection; external standard method quantification.

[0026] Example 2-6: Hydrodehalogenation reaction of different halogenated organic compounds in tap water

[0027] The trichloroacetic acid in Example 1 was replaced by the same amount of reactants shown in Table 1, and other operations were the same. The results are shown in Table 1. It can be seen that various haloacetic acids and methyl halides can be highly selectively hydrodehalogenated to acetic acid or methane under the experimental conditions of Example 1.

[0028] Table 1 Hydrodehalogenation reaction of different halogenated organic compounds

[0029]

[0030] Example 7-11: Effect of Catalyst Type on Hydrodechlorination of Trichloroacetic Acid in Tap Water

[0031] The catalyst in Example 1 was replaced with the same amount of catalyst shown in Table 2 (except for special instructions), and other operations were the same. The results are shown in Table 2. It can be seen that various catalysts with ruthenium or platinum as active components can hydrodechlorinate trichloroacetic acid to acetic acid with high selectivity.

[0032] Table 2 Effect of different catalysts on the hydrodehalogenation reaction of trichloroacetic acid

[0033]

[0034] a Preparation method of nickel foam loaded with ruthenium: First, nickel foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then in 0.5 mol·L -1 The nickel foam was soaked in HNO3 aqueous solution for 5 min, and finally washed with a large amount of deionized water. Then, the nickel foam was used as the cathode and the platinum electrode was used as the anode. -1 RuCl3 and 0.1 mol·L -1 The aqueous solution of aminosulfonic acid is the cathode electrolyte, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.05A·cm -2The current density was 0.1000 ℃ and the ruthenium foam was obtained by electrodeposition (Ru / Ni, Ru content 0.1 mg / cm 2 ).

[0035] b Preparation method of platinum-supported copper foam: First, copper foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then heated to 0.5 mol·L -1 The copper foam was immersed in HCl aqueous solution for 15 min, and finally washed with a large amount of deionized water. Then, the copper foam was used as the cathode and the platinum electrode was used as the anode. -1 H2PtCl6 and 0.1mol·L -1 The catholyte is an aqueous solution of HCl, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.05A·cm -2 The foam copper-supported platinum (Pt / copper, Pt content 0.1 mg / cm 2 ).

[0036] Examples 12-16. Hydrodechlorination of trichloroacetic acid in water - temperature, reactant concentration, water and precious metal loading

[0037] Example 1 was adjusted according to the conditions in Table 3, and other operations were the same. The results are shown in Table 3. It can be seen that in the temperature range of 5-40°C and the reactant concentration range of 10 μg / L to 3 mg / L, trichloroacetic acid in tap water and well water can be highly selectively hydrogenated and dechlorinated to acetic acid under the catalysis of ruthenium-carbon catalyst.

[0038] Table 3 Hydrodechlorination reaction of trichloroacetic acid in water under different conditions

[0039]

[0040]

[0041] Unless otherwise specified, the other reaction conditions are the same as those in Example 1. a The Ru content in the catalyst is 10 wt %, and the reaction time is 6 hours; b The Ru content in the catalyst was 0.1 wt%, and the reaction time was 10 minutes.

[0042] Comparative Example 1: Hydrodechlorination of trichloroacetic acid in tap water - palladium-carbon catalyst

[0043] Take a three-necked flask as a reactor, first 2mg palladium carbon (Pd / C, Pd content is 5wt%) catalyst is added to 100mL of tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid, then the nitrogen that passes into the tap water is 50mL / min, after 10 minutes, the nitrogen is switched to the hydrogen of equal flow to start the reaction, after reacting for 60min, the conversion rate of trichloroacetic acid in the tap water=99.9%, the yield of monochloroacetic acid=16.8%, the yield of acetic acid=82.5%, and the selectivity of acetic acid 82.6%; after reacting for 120min, the conversion rate of trichloroacetic acid in the tap water=100%, the yield of monochloroacetic acid=16.5%, the yield of acetic acid=83.1%, and the selectivity of acetic acid 83.1%.

[0044] Compared with Example 1, the selectivity of acetic acid decreased by 15.5% at the same reaction time. The selectivity of acetic acid remained almost unchanged when the reaction time was extended.

[0045] Comparative Example 2: Hydrodechlorination of chloroform in tap water - palladium-carbon catalyst

[0046] A three-necked flask was used as a reactor. First, 2 mg of palladium carbon (Pd / C, the content of Pd was 5 wt%) catalyst was added to 100 mL of tap water (pH=7.2, temperature=25°C) containing 3 mg / L chloroform. Then, nitrogen with a flow rate of 50 mL / min was introduced into the tap water. After 10 minutes, the nitrogen was switched to hydrogen with an equal flow rate to start the reaction. After 60 min of reaction, the conversion rate of chloroform in the tap water was 99.9%, the total yield of dichloromethane and monochloromethane was 9.1%, the yield of methane was 89.2%, and the selectivity of methane was 89.3%. After 120 min of reaction, the conversion rate of chloroform in the tap water was 100%, the total yield of dichloromethane and monochloromethane was 8.5%, the yield of methane was 90.1%, and the selectivity of methane was 90.1%.

[0047] Compared with Example 5, the selectivity of methane decreased by 8.6% at the same reaction time. The selectivity of methane remained almost unchanged when the reaction time was extended.

[0048] Comparative Example 3: Hydrodechlorination of trichloroacetic acid in tap water - palladium-supported alumina catalyst

[0049] A three-necked flask was used as a reactor. First, 2 mg of alumina-supported palladium (Pd / Al2O3, the content of Pd was 5 wt%) catalyst was added to 100 mL of tap water (pH=7.2, temperature=25°C) containing 3 mg / L trichloroacetic acid. Then, nitrogen with a flow rate of 50 mL / min was introduced into the tap water. After 10 minutes, the nitrogen was switched to hydrogen with an equal flow rate to start the reaction. After 60 min of reaction, the conversion rate of trichloroacetic acid in the tap water was 99.9%, the yield of monochloroacetic acid was 11.6%, the yield of acetic acid was 87.7%, and the selectivity of acetic acid was 87.8%. After 120 min of reaction, the conversion rate of trichloroacetic acid in the tap water was 100%, the yield of monochloroacetic acid was 11.3%, the yield of acetic acid was 88.1%, and the selectivity of acetic acid was 88.1%.

[0050] Compared with Example 1, the selectivity of acetic acid at the same reaction time decreased by 10.3%. When the reaction time was extended, the selectivity of acetic acid remained almost unchanged.

[0051] Comparative Example 4: Hydrodechlorination of Chloroform in Tap Water - Alumina-supported Palladium Catalyst

[0052] A three-necked flask was used as a reactor. First, 2 mg of alumina-supported palladium (Pd / Al2O3, Pd content of 5 wt%) catalyst was added to 100 mL of tap water (pH=7.2, temperature=25°C) containing 3 mg / L chloroform. Then, nitrogen with a flow rate of 50 mL / min was introduced into the tap water. After 10 minutes, the nitrogen was switched to hydrogen with an equal flow rate to start the reaction. After 60 min of reaction, the conversion rate of chloroform in the tap water was 99.9%, the total yield of dichloromethane and monochloromethane was 12.3%, the yield of methane was 87.8%, and the selectivity of methane was 87.9%. After 120 min of reaction, the conversion rate of chloroform in the tap water was 100%, the total yield of dichloromethane and monochloromethane was 11.9%, the yield of methane was 87.8%, and the selectivity of methane was 87.8%.

[0053] Compared with Example 5, the selectivity of methane decreased by 10.0% at the same reaction time. The selectivity of methane remained almost unchanged when the reaction time was extended.

[0054] Comparative Example 5: Hydrodechlorination of trichloroacetic acid in tap water - Rhodium-carbon catalyst

[0055] A three-necked flask was used as a reactor. First, 2 mg of ruthenium-on-carbon (Rh / C, Rh content was 5 wt%) catalyst was added to 100 mL of tap water (pH=7.2, temperature=25° C.) containing 3 mg / L trichloroacetic acid. Then, nitrogen was introduced into the tap water at a flow rate of 50 mL / min. After 10 minutes, the nitrogen was switched to hydrogen with an equal flow rate to start the reaction. After 60 min of reaction, the conversion rate of trichloroacetic acid in the tap water was 99.9%, the yield of monochloroacetic acid was 6.6%, the yield of acetic acid was 92.8%, and the selectivity of acetic acid was 92.9%. After 120 min of reaction, the conversion rate of trichloroacetic acid in the tap water was 100%, the yield of monochloroacetic acid was 1.5%, the yield of acetic acid was 98.1%, and the selectivity of acetic acid was 98.1%.

[0056] Compared with Example 1, the selectivity of acetic acid decreased by 5.2% at the same reaction time. The selectivity of acetic acid can be close to that of Example 1 by prolonging the reaction time.

[0057] Comparative Example 6: Hydrodechlorination of Chloroform in Tap Water - Rhodium Carbon Catalyst

[0058] A three-necked flask was used as a reactor. First, 2 mg of rhodium carbon (Rh / C, Rh content was 5 wt%) catalyst was added to 100 mL of tap water (pH=7.2, temperature=25° C.) containing 3 mg / L chloroform. Then, nitrogen with a flow rate of 50 mL / min was introduced into the tap water. After 10 minutes, the nitrogen was switched to hydrogen with an equal flow rate to start the reaction. After 60 min of reaction, the conversion rate of chloroform in the tap water was 99.9%, the total yield of dichloromethane and monochloromethane was 5.1%, the yield of methane was 94.4%, and the selectivity of methane was 94.5%. After 120 min of reaction, the conversion rate of chloroform in the tap water was 100%, the total yield of dichloromethane and monochloromethane was 1.8%, the yield of methane was 97.4%, and the selectivity of methane was 97.4%.

[0059] Compared with Example 5, the selectivity of methane decreased by 3.4% at the same reaction time. The selectivity of methane can be close to that of Example 5 by prolonging the reaction time.

[0060] Comparative Example 7: Hydrodechlorination of Tetrachloromethane in Tap Water

[0061] Using a three-necked flask as a reactor, first add 2 mg of ruthenium carbon (Ru / C, Ru content is 5 wt%) catalyst into 100 mL of tap water containing 3 mg / L tetrachloromethane (pH = 7.2, temperature = 25°C), then introduce nitrogen at a flow rate of 50 mL / min into the tap water, and after 10 minutes, switch the nitrogen to hydrogen at the same flow rate to start the reaction. After 60 minutes of reaction, the conversion rate of tetrachloromethane in the tap water = 82.5%, the methane yield = 58.8%, and the methane selectivity = 71.3%.

[0062] This comparative example shows that the hydrodechlorination reaction activity and dehalogenation selectivity of ruthenium-carbon catalyst for tetrachloromethane are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

[0063] Comparative Example 8: Hydrodechlorination of tetrachloroethane in tap water

[0064] Using a three-necked flask as a reactor, first add 2 mg of ruthenium carbon (Ru / C, Ru content is 5 wt%) catalyst into 100 mL of tap water containing 3 mg / L tetrachloroethane (pH = 7.2, temperature = 25°C), then introduce nitrogen at a flow rate of 50 mL / min into the tap water, and after 10 minutes, switch the nitrogen to hydrogen at the same flow rate to start the reaction. After 60 minutes of reaction, the conversion rate of tetrachloroethane in the tap water = 79.8%, the ethane yield = 54.5%, and the methane selectivity 68.3%.

[0065] This comparative example shows that the hydrodechlorination reaction activity and dehalogenation selectivity of the ruthenium-carbon catalyst for tetrachloroethane are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

[0066] Comparative Example 9: Hydrodechlorination of 2,4,6-trichlorophenol in tap water

[0067] Using a three-necked flask as a reactor, first add 2 mg of ruthenium carbon (Ru / C, Ru content is 5 wt%) catalyst into 100 mL of tap water (pH = 7.2, temperature = 25°C) containing 3 mg / L 2,4,6-trichlorophenol, then introduce nitrogen at a flow rate of 50 mL / min into the tap water, and after 10 minutes, switch the nitrogen to hydrogen at the same flow rate to start the reaction. After 60 minutes of reaction, the conversion rate of 2,4,6-trichlorophenol in the tap water = 84.8%, the phenol yield = 1.5%, and the phenol selectivity 1.8%.

[0068] This comparative example shows that the hydrodechlorination reaction activity and dehalogenation selectivity of the ruthenium-carbon catalyst for 2,4,6-trichlorophenol are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

Claims

1. A method for catalytic hydrodehalogenation of haloacetic acid or methyl halide in water, characterized in that: The method uses a ruthenium or platinum-containing material as a catalyst, hydrogen as a reducing agent, and a water body containing halogenated acetic acid or halogenated methyl gas as a treatment object, and hydrogenates and dehalogenates the halogenated acetic acid or halogenated methyl gas in the water body into acetic acid or methane.

2. The method according to claim 1, characterized in that The haloacetic acids include trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, dibromoacetic acid, and monobromoacetic acid; the halogenated methane includes chloroform, dichloromethane, monochloromethane, bromodichloromethane, bromoform, and dibromochloromethane.

3. The method according to claim 1, characterized in that The catalyst is a supported catalyst, and the carrier comprises a carbon material, a metal material, a metal oxide material, a ceramic material or a polymer material.

4. The method according to claim 3, characterized in that The carbon material includes activated carbon, carbon fiber, graphite felt, and foamed glassy carbon; the metal material includes nickel, titanium, copper, silver, and stainless steel; and the metal oxide material includes aluminum oxide, titanium oxide, and cerium oxide.

5. The method according to claim 1, characterized in that The catalyst is Ru / C, Ru / Al2O3, Ru / Ni, Pt / C, Pt / Al2O3 or Pt / Cu.

6. The method according to claim 1, characterized in that The reaction temperature of the hydrodehalogenation is in the range of 5 to 90°C.

7. The method according to claim 1, characterized in that The concentration range of the haloacetic acid or methyl halide in the water body is 10 μg / L to 1 g / L.

8. The method according to claim 1, characterized in that The water body includes drinking water, surface water or groundwater.

9. The method according to claim 1, characterized in that The mass loading of ruthenium or platinum in the catalyst is 0.1-10%.

10. The method according to claim 1, characterized in that The amount of the catalyst used is 10-30 mg / L based on the volume of the water containing the halogenated acetic acid or methyl halide.

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