RU2256498C1 - Catalyst, method for preparation thereof, and a method for complete oxidation of phenol - Google Patents

Abstract

FIELD: oxidation catalysts and waste water treatment.

SUBSTANCE: catalyst than may be used in hydrogen peroxide-mediated oxidation of phenol in waste waters at 50-70°C is based on montmorillonite clay and iron and aluminum ions intercalated in the form of polyoxometallate cation [Al₁₂FeO₄(OH)₂₄(H₂O)₁₂]⁷⁺. Complete oxidation of phenol into CO₂ and H₂O with hydrogen peroxide is effected in presence of above-defined catalyst, which is characterized by low degree of washing-out of active component into solution, at 50-70°C, preferably in aqueous solutions with acidity close to neutral.

EFFECT: reduced expenses, simplified preparation procedure, and achieved environmental safety.

5 cl, 1 dwg, 3 tbl, 15 ex

Description

The invention relates to the field of chemical industry and environmental protection and can be used for wastewater treatment from phenol, hazardous to human health and the environment, by oxidation with hydrogen peroxide at 50-70 ° C: C ₆ H ₅ OH + 14H ₂ O ₂ → 6CO ₂ + 17H ₂ O.

There are several fundamentally different methods for the oxidation of phenol:

1) biochemical oxidation using microorganisms [Method, reagent and kit for the detection of fecal occult blood. WFSmith, DWRobinson, TRScheiner, USA Pat. 5447868 (1993)], 2) electrochemical and photocatalytic oxidation [Anodic oxidation of phenol in the presence of NaCI for wastewater treatment ", Ch. Comninellis, A. Nerini, J. Appl. Electrochem., 25 (1995) 23], and also 3) homogeneous and heterogeneous low-temperature catalytic oxidation using transition and noble metals (cobalt, nickel, iron, etc.) as an active component of the catalyst [MRMaurya, SJJ Titinchi, S. Chand., Oxidation of phenol with H ₂ O ₂ catalysed by Cr (III), Fe (III) or Bi (III) N, N'-bis- (salicylidene) diethylenetriamine (H2saliden) complexes encapsulated in Zeolite-Y, J. Mol. Catal.A: Chemical., 193 (2003) 165 .; Alejandre, A .; Medina, F .; Rodriguez, X .; Salagre, P .; Sueiras, JE Preparation and activity of Cu-Al mixed oxides v ia hydrotalcitelike precursors for the oxidation of phenol aqueous solutions., Journal of Catalysis, 188 (1999) 311].

In the low-temperature oxidation of phenol with hydrogen peroxide, three main methods of introducing Fe (II) and Fe (III) iron ions into the catalyst are used: 1) adsorption of iron ions on various carriers, such as activated carbons, graphite, etc. [The use of carbon catalysts for oxidation destructive wastewater treatment./ Tarkovskaya I.A., Stavitskaya S.S., Lukyanchuk V.M., Tarkovskaya GB.// Chemistry and water technology, 1993, 15, No. 7-8, p. 578-583 ; The method of wastewater treatment from organic impurities, Ryazantsev AA, Batoeva AA, Zhalsanova DB, RU 2135419 (1999)], 2) embedding iron ions in the catalyst matrix, for example, in the zeolite frame H-ZSM -5 [K. Fajerwerg, H. Debellefontaine, Wet oxidation of phenol by hydrogen peroxide using heterogeneous catalysis Fe-ZSM-5: a promising catalyst., Appl. Catalysis B: Environmental, 10 (1996) L229] or silicate matrix [N .Crowther, F. Larachi, Iron-containing silicalites for phenol catalytic wet peroxidation, Appl. Catalysis B: Environmental, 46 (2003) 293] and 3) introducing iron ions into the interlayer space of layered clays such as beidelite [C. Catrinescu, C. Theodosiu, M. Macoveanu, J. Miehe-Brendle, RL Dred, Water Research, 37 (2003) 1154], bentonite [E. Guelo u, J. Barrault, J. Foumier, J.-M. Tatibouet, Active iron species in the catalytic wet peroxide oxidation of phenol over pillared clays containing iron, Appl. Catalysis B: Environmental, 44 (2003) 1] et al.

The disadvantages of catalytic methods based on the use of intercalated clays of beidelite or bentonite with iron ions are the necessity of carrying out the process in the presence of acids such as sulfuric or nitric (pH = 2-5), the introduction of significant amounts of catalyst into the system (1-10% wt / l ), as well as a substantial leaching of the active component into the solution.

The closest solution in terms of the number of similar features to the proposed invention is a method consisting in the oxidation of phenol with hydrogen peroxide in the presence as a catalyst of bentonite intercalated with aluminum-iron hydroxocomplex, in the molar ratio [H ₂ O ₂ ] / [PhOH] = 14: 1 [J. Barrault, M. Abdellaoui, C. Bouchoule, A. Majeste, JM Tatibouet, A. Louloudi, Catalytic wet oxidation over mixed (Al-Fe) pillared clays, Appl. Catalysis B: Enviromental, 27 (2000) L225]. The aluminum-iron hydroxocomplex was obtained by hydrolysis of a mixed solution of AlCl ₃ and FeCl ₃ (Al ³⁺ / Fe ³⁺ = 9 mol.) With a solution of NaOH (OH / (Al ³⁺ + Fe ³⁺ ) = 1.9 mol.) And fixed on the surface of bentonite by ion sharing. To form active sites, the intercalated clay was calcined at 500 ° С for 2 h. In the presence of this catalyst, phenol was oxidized at a temperature of 25-70 ° С, catalyst concentration (0.5-1.0 g / l) and pH = 2 ÷ 5.5. The acidity of the medium is an important factor that significantly affects the activity of the catalyst. The catalyst has the highest activity at pH = 3.5 ÷ 4.0. During the reaction, 0.2–1.0 ppm iron ions are washed out from the catalyst into the solution. With this method of oxidizing phenolic solutions, complete removal of intermediate reaction products (CH ₃ COOH, HCOOH, UNOOSSOO, etc.) is not achieved (table 1).

The data show that the prototype has the following disadvantages:

- the need for a reaction in a strongly acidic environment,

- leaching of the active component during the reaction into the solution,

- incomplete purification of aqueous solutions from intermediate products of phenol oxidation.

The objective of the invention is to provide a liquid-phase low-temperature method for the complete oxidation of phenol in aqueous solutions with an acidity close to neutral with hydrogen peroxide in the presence of a catalyst with a low degree of washing off of the active component into the solution.

The problem is solved by using a catalyst for the complete oxidation of phenol with hydrogen peroxide based on layered montmorillonite clay and a mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ in which the mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ having a layered columnar structure is in the interlayer space of clay and prevents the closure of silicate layers of clay.

The problem is also solved by the method of preparing a catalyst for the complete oxidation of phenol with hydrogen peroxide based on layered montmorillonite clay and a mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ , in which the mixed oxide phase Al ₂ O ₃ · Fe ₂ O _{3 is} obtained by intercalating a polyoxometallate of the composition [Al ₁₂ FeO ₄ (OH) ₂₄ (H ₂ O) ₁₂ ] ⁷⁺ into the interlayer space of layered montmorillonite clay.

The problem is also solved by the method of complete oxidation of phenol with hydrogen peroxide in the presence of a catalyst based on a modified layered clay, which is carried out at a temperature of 50-70 ° C and atmospheric pressure in aqueous solutions with an acidity of the medium close to neutral hydrogen peroxide in the presence of the catalyst described above. The process is carried out at a pH of at least 6.0. The weight concentration of the catalyst in the solution is not more than 1.5 g / l.

The catalyst is a composite system based on montmorillonite clay, for example montmorillonite clay of the Mukhortalinsky deposit (Republic of Buryatia), having the following chemical composition, wt.%: SiO ₂ - 65.50; Al ₂ O ₃ - 14.30; Fe ₂ O ₃ - 1.78; MgO - 1.42; CaO - 1.08; K ₂ O - 0.20; Na ₂ O - 0.10; FeO - 0.22; MnO - 0.02; TiO ₂ 0.19; P ₂ O ₅ - 0.03; H ₂ O - 15.16, and polyoxometallate (POM) containing ions of iron and aluminum.

Polyoxometallate (POM) is obtained in the form of a Keggin cation according to a modified method [Pillared interlayered clay materials useful as catalysts and sorbents, D.E.W. Vaughan, R.J. Lussier, Jr.J.S. Magee, USA Pat. 4176090 (1979)] and fix in the interlayer space of clay.

The essential features affecting the achievement of the task are:

- temperature mode of the process

- chemical composition and preparation of the catalyst.

The claimed invention has the following features similar to the prototype:

- aqueous phenol solutions are oxidized with hydrogen peroxide

- the process is carried out in the presence of layered clay intercalated with iron ions.

The combination of general and distinctive features characterizing the claimed method is not known from the prior art, which indicates the compliance of the claimed invention with the criterion of "novelty."

The problem is solved due to the combination of features set forth in the distinctive part of the formula, and can be achieved exclusively with the specified method of clay intercalation of the corresponding chemical composition of polyoxometallate (POM).

The invention is illustrated by the following examples.

Example 1. The catalyst is prepared as follows.

Preparation of modifying solution (1) of a polyoxometallate of the composition [Al ₁₂ FeO ₄ (OH) ₂₄ (H ₂ O) ₁₂ ] ⁷ ).

Na ₂ CO ₃ (300 ml, 0.2 M) ([OH ^- ] / [Fe ³⁺ + Al ³⁺ ) is slowly added to the solution containing AlCl ₃ (272 ml, 0.2 M) and FeCl ₃ (27 ml, 0.2 M). ] = 2; pH = 4.0-4.5). The solution was kept at room temperature for 14 days and for 36 hours at 95 ° C.

Intercalation of layered clay (CAC).

Before intercalation, CAC is separated from large impurities by washing several times with water,

5 g of natural clay, aged in 200 ml of water during the day at 20 ° C, is subjected to ultrasonic treatment (22 kHz, 3 min). 600 ml of solution (1) are slowly added to the suspension at 80 ° C with vigorous stirring. The resulting mixture was kept at room temperature for one day, after which the precipitate was separated, washed with water until a negative reaction to chloride ions, dried in air at room temperature and calcined at 500 ° C for 3 hours. The resulting sample contains 15 ± 2 mg / g of iron ions.

An aqueous solution of phenol (20 ml, 1 mmol), 10 mg (0.5 g / l) of catalyst was loaded into a 100 ml reactor, the mixture was heated to 50 ° C and H ₂ O ₂ (0.28 ml, 1 M) was added ([H ₂ O ₂ ] / [PhOH] = 14 mol / mol). The reaction mass is maintained with vigorous stirring until the phenol is completely oxidized for 7.8 hours. The reaction solution is analyzed by LC and spectrophotometrically. The amount of iron ions in the reaction mass, washed out of the catalyst during the reaction, is lower than the sensitivity level of the method for determining iron ions (Sensitivity of the method is 0.1 ppm [Kreshkov A.P. Fundamentals of Analytical Chemistry, T.2, Khimiya Publishing House, 1965, S.350]) The results are shown in table 2.

In all subsequent examples, the catalyst prepared in Example 1 was used.

Example 2. Similar to example 1, the difference is that 20 mg (1.0 g / l) of catalyst are loaded into the reactor. The complete oxidation of phenol is achieved in 6.8 hours. The amount of iron ions in the reaction mass washed out of the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Example 3. Similar to example 1, the difference is that 30 mg (1.5 g / l) of catalyst are loaded into the reactor. Complete phenol oxidation is achieved in 6.0 hours. The amount of iron ions in the reaction mass washed out of the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Example 4. Similar to example 3, the difference is that the reaction is carried out at 60 ° C. The complete oxidation of phenol is achieved in 4.3 hours. The amount of iron ions in the reaction mass washed from the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Example 5. Similar to example 4, the difference is that 0.028 ml of 10 M H ₂ O ₂ is introduced into the solution. The complete oxidation of phenol is achieved in 2.5 hours. The amount of iron ions in the reaction mass washed out of the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Example 6. Similar to example 5, the difference is that the reaction is carried out at 70 ° C. The complete oxidation of phenol is achieved in 1.8 hours. The amount of iron ions in the reaction mass washed from the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Examples 3, 4 and 6 demonstrate that the speed of the process can be increased by increasing the temperature. Examples 3 and 4 show that the activity of the catalyst system can be enhanced by using concentrated hydrogen peroxide.

Example 7. Similar to example 1, the difference is that the reaction is carried out at pH = 5.0, adding to the solution of H ₂ SO ₄ (0.04 ml, 0.02 M) and use 10 M H ₂ O ₂ . Complete phenol oxidation is achieved in 2.6 hours. The amount of iron ions in the reaction mass washed out of the catalyst during the reaction is lower than the sensitivity level of the method for determining iron ions.

Example 8. Similar to example 7, the difference is that the reaction is carried out at pH = 4.0, adding to the solution of H ₂ SO ₄ (0.14 ml, 0.02 M). The complete oxidation of phenol is achieved in 1.5 hours. The amount of iron ions in the reaction mass, washed from the catalyst during the reaction, was 0.5 ppm.

Example 9. Similar to example 7, the difference is that the reaction is carried out at pH = 3.8, adding to the solution of H ₂ SO ₄ (0.21 ml, 0.02 M). The complete oxidation of phenol is achieved in 1.0 h. The amount of iron ions in the reaction mass, washed from the catalyst during the reaction, was 2.5 ppm.

Example 10. Similar to example 7, the difference is that the reaction is carried out at pH = 3.0, adding to the solution of H ₂ SO ₄ (1.35 ml, 0.02 M). The complete oxidation of phenol is achieved in 1.2 hours. The amount of iron ions in the reaction mass washed from the catalyst during the reaction was 8.5 ppm.

Examples 7-10 demonstrate that the speed of the process can be increased by changing the acidity of the medium.

Examples 11-14. The process is carried out as in example 3, but the catalyst after each cycle is filtered off, washed with water, dried and reused. The results obtained for 4 cycles (examples 11-14) are shown in table 3.

These examples demonstrate that the catalyst can be separated from the reaction mixture by simple filtration and reused.

Example 15. The process is carried out as in example 5, the difference is that the phenol oxidation reaction (1 mM) is carried out in D ₂ O. The reaction mass is analyzed by ¹ H NMR. The degree of purification of the aqueous solution from phenol oxidation products is close to 100% , as evidenced by the presence in the NMR spectrum of only signals from H ₂ O (δ = 4.87 ppm) and D ₂ O (δ = 4.85 ppm) (see drawing, on which NMR ¹ H spectrum of the solution after the phenol oxidation reaction ([PhOH] / [H ₂ O ₂ ] = 1/14 mol / mol, [catalyst] = 1 g / l, 60 ° C, 2.5 h).

This example demonstrates that in the presence of the proposed catalyst, phenol can be oxidized to CO ₂ and H ₂ O.

Table 1.
Oxidation of an aqueous phenol solution in the presence of Fe / Al-bentonite ([PhOH] = 1 mM, [H ₂ O ₂ ] = 14 tM) as a catalyst [J. Barrault, M. Abdellaoui, C. Bouchoule, A. Majeste, JM Tatibouet, A. Louloudi, Catalytic wet oxidation over mixed (Al-Fe) pillared clays, Appl. Catalysis B: Enviromental, 27 (2000) L225]. No. T ° C Catalyst g / l pH Time ¹ h The degree of complete oxidation% The iron content of ² ppm 1 40 0.5 3.5 4.0 72 0.8 2 70 1.0 3.5 2.0 78 0.2 ¹ Time for which 100% phenol conversion is achieved; ^{2 The} amount of iron washed into the solution during the reaction.

Table 2.
Oxidation of an aqueous phenol solution in the presence of Al / Fe-CAC systems as a catalyst ([PhOH] = 1 mM, [H ₂ O ₂ ] = 14 mM). No. T ° C Catalyst g / l pH Time ¹ h The iron content of ² ppm 1 fifty 0.5 6.2 7.8 less than 0.1 ⁴ 2 fifty 1.0 6.2 6.8 less than 0.1 ⁴ 3 fifty 1.5 6.2 6.0 less than 0.1 ⁴ 4 60 1.0 6.2 4.3 less than 0.1 ⁴ 5 60 ³ 1.0 6.2 2.5 less than 0.1 ⁴ 6 70 ³ 1.0 6.2 1.8 less than 0.1 ⁴ 7 50 ³ 0.5 5.0 2.6 less than 0.1 ⁴ 8 50 ³ 0.5 4.0 1.5 0.5 nine 50 ³ 0.5 3.8 1.0 2.5 10 50 ³ 0.5 3.0 1.2 8.5 ¹ Time for which 100% phenol conversion is achieved; ^{2 The} amount of iron washed into the solution during the reaction; ³ Used 10 M H ₂ O ₂ ; ⁴ Sensitivity of the method 0.1 ppm [Kreshkov A.P., Fundamentals of Analytical Chemistry, Vol. 2, Publishing House "Chemistry", 1965. P.350].

Table 3.
Oxidation of an aqueous phenol solution in the presence of Al / Fe-CAC as a catalyst ([PhOH] = 1 mM, [H ₂ O ₂ ] = 14 tM, [catalyst] = 0.5 g / l, pH = 6.2, 50 ° C). No. Cycle number Time ¹ h The iron content of ² ppm eleven 1 1.8 less than 0.1 ³ 12 2 1.8 - thirteen 3 3.3 2.9 14 4 6.0 3.9 ¹ Time for which 100% phenol conversion is achieved; ^{2 The} amount of iron washed into the solution during the reaction; ³ The sensitivity of the method is 0.1 ppm. [Kreshkov A.P., Fundamentals of Analytical Chemistry, Vol. 2, Publishing House "Chemistry", 1965, S.350].

Claims (5)

1. The catalyst for the complete oxidation of phenol with hydrogen peroxide based on layered montmorillonite clay and a mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ , characterized in that the mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ having a layered columnar structure, located in the interlayer space of clay and prevents the closure of silicate layers of clay. 2. A method of preparing a catalyst for the complete oxidation of phenol with hydrogen peroxide based on layered montmorillonite clay and a mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ , characterized in that the mixed oxide phase Al ₂ O ₃ · Fe ₂ O ₃ is obtained by intercalating a polyoxometallate of the composition [Al ₁₂ FeO ₄ (OH) ₂₄ (H ₂ O) ₁₂ ] ⁷⁺ into the interlayer space of layered montmorillonite clay. 3. A method for the complete oxidation of phenol with hydrogen peroxide in the presence of a catalyst based on a modified layered clay, characterized in that the process is carried out at a temperature of 50-70 ° C in aqueous solutions with a medium acidity close to neutral with hydrogen peroxide in the presence of a catalyst according to any one of claims .1 and 2. 4. The method according to claim 3, characterized in that the process is carried out at a pH of not lower than 6.0. 5. The method according to PP.3 and 4, characterized in that the weight concentration of the catalyst in the solution is not more than 1.5 g / L.