CN103285865B - Catalyst for synthesizing benzaldehyde by carrying out liquid-phase high-selectivity catalytic oxidation on methylbenzene - Google Patents

Abstract

The invention discloses a novel catalyst for highly selective catalytic oxidation of toluene in liquid phase. The catalyst mainly uses alkaline earth metal composite oxides with high temperature stability as the carrier; highly active metals (V, Cr, Mn, Fe, Co, Ni, Cu, Au, Pd, Pt) as the catalytic oxidation active center. The catalyst prepared by the present invention shows high selectivity and activity in the liquid-phase oxidation of toluene, at a reaction temperature of 90-160° C., a reaction time of 2-48 hours, and an air or oxygen pressure of 0.5-2.0 MPa , the highest selectivity of benzaldehyde can be 94.0%, and the conversion rate of toluene is also up to 45.0%. Compared with the reported results, the catalyst prepared by the present invention still has a good mesoporous structure at high temperature, and in the process of catalysis, the conversion rate of toluene and the yield of benzaldehyde are high, and the reaction system does not add Any solvent or organic additive has many advantages such as high yield, low cost, no pollution to the environment, easy separation and good repeatability.

Description

Catalyst for the synthesis of benzaldehyde by liquid-phase highly selective catalytic oxidation of toluene

technical field

The invention relates to a novel catalyst for producing benzaldehyde by liquid-phase highly selective oxidation of toluene and a preparation method thereof.

Background technique

Volatile organic compounds (VOCs) are one of the common exhaust gases, mainly from petrochemical, paint production, metal coating, printing and varnish and other production fields. Volatilizing into the atmosphere will not only pollute the environment, but also endanger human health. If VOCs are converted into useful chemical products or chemical intermediates, it can not only reduce the discharge of waste, but also turn waste into treasure and improve economic benefits. Toluene, one of the most harmful and polluting VOCs members, can be oxidized to produce benzyl alcohol, benzaldehyde, benzoic acid, benzyl benzoate, etc. These products are widely used as general intermediates in dyes, solvents, fragrances, Plasticizers, dyes, preservatives, flame retardants and other fields. Especially in recent years, as the demand for chlorine-free benzaldehyde in the pharmaceutical and fragrance industries has increased year by year, the selective oxidation of toluene side chains to produce benzaldehyde has attracted more attention. However, the technology of the 1960s is still used in the industry at present, the reaction speed is slow, the consumption of toluene is large, and due to the existence of deep oxidation and ring hydroxylation side reactions, the selectivity is low and the economic effect is poor. Therefore, research on the selective oxidation of toluene to form benzaldehyde has great commercial development value and scientific significance.

Compared with other oxidants, air and oxygen have many advantages such as cheapness, environmental protection and easy availability, which make the selective oxidation of toluene with molecular oxygen have great development prospects. Molecular oxygen selective oxidation of toluene can be divided into gas phase oxidation and liquid phase oxidation. Although both catalytic systems show high catalytic activity, the high reaction temperature in the gas-phase catalytic oxidation process is prone to deep oxidation, resulting in generally low selectivity of target products. In terms of liquid-phase catalytic oxidation, the MC catalytic system is relatively mature, but the selectivity of the target product still needs to be improved. At the same time, it is difficult to separate the catalyst, solvent and product, and the environmental pollution is serious, which is not suitable for the development of modern chemical industry; recently Kesavan et al. Science, 2011, 331(6014): 185-199 reported the liquid-phase catalytic oxidation of toluene by activated carbon-supported Au, Pd nano-alloy catalyst (Au-Pd/C) under solvent-free conditions, and found that when n(Au) in the catalyst : When n(Pd)=1:1.85, react 27h under 160 ℃, the conversion rate of toluene is 94.4%, the selectivity of benzyl benzoate can reach 85.5%, but the selectivity of benzaldehyde is only 1.0%, how to optimize the catalysis System to improve the selectivity of benzaldehyde is one of the problems to be solved urgently.

Contents of the invention

1. The technical problem to be solved by the invention

Aiming at the problems existing in the existing methods for producing benzaldehyde, the invention provides a novel catalyst for producing benzaldehyde by liquid-phase highly selective oxidation of toluene and a preparation method thereof.

2. Technical solution

(1) A novel catalyst for toluene liquid-phase highly selective catalytic oxidation, characterized in that: the catalyst is mainly based on the alkaline earth metal composite oxide of high temperature stability as a carrier; with highly active metals (V, Cr, Mn, Fe, Co, Ni, Cu, Au, Pd, Pt) etc. are catalytic oxidation active centers, and the content of the responsible metal element accounts for 0.03-1.0% of the total mass of the catalyst.

(2) the preparation method of the novel catalyst that is used for toluene liquid-phase selective oxidation system benzaldehyde comprises the steps:

1) Prepare a mixed aqueous solution of divalent alkaline earth metal nitrate and aluminum nitrate, control the molar ratio of alkaline earth metal cations to aluminum ions at 2.0-5.0; control the total concentration of cations at 0.2-1.5mol/L;

2) Prepare ammonium carbonate aqueous solution, control the molar dosage of ammonium carbonate and aluminum nitrate to be the same, mix the above two solutions and fully stir for 0.5 hours, and control the temperature at 60°C. During this process, use NH ₄ OH to control the pH value of the mixed solution at 8 to 11.5, then filter or centrifugally dehydrate the obtained colloid, wash with water until neutral, and dry at 100°C. The obtained solid sample is calcined in _N2 gas at 300-700°C for 4 hours to obtain the corresponding metal composite oxide ;

3) Place the obtained metal composite oxide in an aqueous solution of amine halides with a mass percent concentration of 1-10%, and add an equal volume of 0.2mol/L template aqueous solution to it, and control the temperature at 60-100°C and the pH value at 8.0～11.5. Add transition metal nitrate or noble metal salt after 12 hours, keep the molar number of transition metal nitrate as 5～20% of the molar number of alkaline earth metal, the molar number of noble metal is 0.1～1.0% of the molar number of alkaline earth metal, at the same time Add an appropriate amount of H ₂ O ₂ to keep the moles of H ₂ O ₂ equal to the moles of amine halides, stir for 24 hours, filter or centrifugally dehydrate the resulting colloid, dry at 100°C, and calcinate in N ₂ gas at 800-1200°C 2 to 10 hours need a new catalyst.

The alkaline earth metal nitrate may be one or both of magnesium nitrate, calcium nitrate, strontium nitrate and barium nitrate.

The amine halide may be one or both of ammonium fluoride, ammonium chloride, ammonium bromide and ammonium iodide.

The template agent can be cetyltrimethylammonium bromide (CTAB), polyethylene glycol octylphenyl ether (TritonX-10) and polyoxyethylene-polyoxypropylene-polyoxyethylene three-block One of segment copolymers (P123).

The transition metal nitrate can be one or two of vanadium nitrate, chromium nitrate, manganese nitrate, ferrous nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and the noble metal salt can be PdCl ₂ , HAuCl ₄ ·3H ₂ One or both of O and H ₂ PtCl ₆ ·6H ₂ O.

Product analysis, chromatographic conditions are as follows: Agilent 6890 gas chromatography (capillary column: 30mm×320um×0.25um), column temperature 50°C, temperature program: initial temperature 50°C, first stage 15°C/min to 220°C, last 5min. The carrier gas was N ₂ , the flow rate was 40mL/min, the hydrogen ion flame detector was used, and the sample was injected manually with a sample volume of 0.2μL. The products were quantitatively analyzed by the normalization method.

3. Beneficial effect

Compared with existing catalysts, the present invention has the following advantages:

(1) The obtained catalyst still has a mesoporous structure and a higher specific surface area at a higher temperature.

(2) In the reaction process, the selectivity and yield of benzaldehyde are all higher, and the reaction conditions are mild.

(3) No solvent and organic additives are added to the reaction system, which does not pollute the environment, and the target product is easy to separate, and can be used in industrial production in large quantities.

Detailed ways:

Example 1

Mix 7.2Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 3.1Kg Ba(NO ₃ ) ₂ and 7.5Kg Al(NO ₃ ) ₃ ·9H ₂ O with deionized water to make a 200L solution; mix 2.1Kg Na ₂ CO ₃ Prepare a 200L solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hours, and add NH ₄ OH to control the pH of the mixed solution to 8.0. The obtained colloid is filtered or centrifugally dehydrated, washed with water until neutral, dried at 100°C, placed at 300°C in _N atmosphere for 4 hours and calcined for 4 hours, and the obtained sample is placed in 50 L of mass concentration of 1% ammonium fluoride aqueous solution, 50L of 0.2mol/L CTAB was added therein, the temperature was controlled at 60°C, and the pH of the mixture was controlled by NH ₄ OH to 8.0. After 12 hours, 7.2Kg of Cu(NO ₃ ) ₂ ·3H ₂ O was added, and at the same time A 30% H ₂ O ₂ aqueous solution with an equimolar amount of ammonium fluoride is stirred for 24 hours, the obtained colloid is filtered or centrifugally dehydrated, dried at 100°C, and calcined in N ₂ gas at 800°C for 2 hours to obtain a new catalyst. Add toluene and catalyst into a 100L autoclave, feed _O2 to 0.5MPa, toluene 10.0Kg, the amount of catalyst is 0.6%wt of the reactant, when the temperature rises to 90°C, start stirring, after 12 hours of reaction, the product is settled by centrifugation , and the supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 3.0%, and the selectivity of benzaldehyde was 85%.

Example 2

6.1Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.4Kg Ca(NO ₃ ) ₂ ·4H ₂ O and 2.3Kg Al(NO ₃ ) ₃ ·9H ₂ O were prepared into a 7.2L solution with deionized water; 0.6Kg Na ₂ CO ₃ was prepared into 7.2L solution with deionized water. After mixing the two solutions, vigorously stirred at 60°C for 0.5 hour, and added NH ₄ OH to control the pH value of the mixture to 11.5. The obtained colloid was filtered or centrifugally dehydrated, washed with water until neutral, dried at 100°C, placed at 700°C in _N atmosphere for 4 hours and calcined for 4 hours, and the obtained sample was placed in 50L of mass concentration of 10% ammonium fluoride aqueous solution, And add 50L 0.2mol/L CTAB to it, control the temperature at 60°C, and use NH ₄ OH to control the pH value of the mixed solution to 11.5. After 12 hours, add 0.87Kg of Cu(NO ₃ ) ₂ ·6H ₂ O and 1.0Kg Fe(NO ₃ ) ₂ 6H ₂ O, at the same time, add 30% H ₂ O ₂ aqueous solution with the same molar number as ammonium fluoride, stir for 24 hours, the obtained colloid is filtered or centrifugally dehydrated, dried at 100°C, and dried at 1200°C The new catalyst required for calcination in _N2 gas for 10 hours. Put toluene and catalyst into a 100L autoclave, feed air to 0.5MPa, toluene 10.0Kg, catalyst dosage is 0.6%wt of the reactant, when the temperature rises to 160°C, start stirring, after 48 hours of reaction, the product is centrifugally settled, The supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 15.0%, and the selectivity of benzaldehyde was 25%.

Example 3

Mix 6.1Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.6Kg Ba(NO ₃ ) ₂ and 3.8Kg Al(NO ₃ ) ₃ ·9H ₂ O with deionized water to make 40L solution; mix 1.1Kg Na ₂ CO ₃ Prepare a 40L solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hour, and add NH ₄ OH to control the pH of the mixed solution to 10.0. The obtained colloid is filtered or centrifugally dehydrated, washed with water to neutrality, dried at 100°C, placed at 500°C in _N atmosphere for 4 hours and calcined for 4 hours, and the obtained sample is placed in a 3.0% ammonium bromide aqueous solution with a mass concentration of 50L. 50L of 0.2mol/L TritonX-10 was added therein, the temperature was controlled at 80°C, and the pH of the mixture was controlled by NH ₄ OH to 10.0. After 12 hours, 1.4Kg of Cr(NO ₃ ) ₂ ·9H ₂ O and 1.0Kg of V(NO ₃ ) ₂ ·6H ₂ O, add 30% H ₂ O ₂ aqueous solution with equal molarity to ammonium bromide at the same time, stir for 12 hours, filter the obtained colloid or centrifugal dehydration, dry at 100°C, 800 The new catalyst required for calcination in _N2 gas at ℃ for 6 hours. Add toluene and catalyst into a 100L autoclave, feed _O2 to 2.0MPa, toluene 10.0Kg, the catalyst dosage is 0.6%wt of the reactant, when the temperature rises to 120°C, start stirring, after 24 hours of reaction, the product is settled by centrifugation , and the supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 25.0%, and the selectivity of benzaldehyde was 35%.

Example 4

11.3Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.6Kg Ba(NO ₃ ) ₂ and 3.8Kg Al(NO ₃ ) ₃ ·9H ₂ O were made into 40L solution with deionized water; 1.0Kg Na ₂ CO ₃ Prepare a 40L solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hour, and add NH ₄ OH to control the pH of the mixed solution to 10.0. The obtained colloid is filtered or centrifugally dehydrated, washed to neutrality, dried at 100°C, placed at 500°C in _N atmosphere and calcined for 4 hours, and the obtained sample is placed in a 6.0% ammonium iodide aqueous solution with a mass concentration of 50L. And add 50L of 0.2mol/L P123, the temperature is controlled at 80°C, and the pH of the mixed solution is controlled by NH ₄ OH to 10.0. After 12 hours, 0.9Kg of Mn(NO ₃ ) ₂ ·6H ₂ O and 0.9Kg of Co(NO ₃ ) ₂ ·6H ₂ O, at the same time, add 30% H ₂ O ₂ aqueous solution with equal molarity to ammonium iodide, stir for 12 hours, the obtained colloid is filtered or centrifugally dehydrated, dried at 100°C, and dried at 800°C The new catalyst required for calcination in _N2 gas for 6 hours. Put toluene and catalyst into a 100L autoclave, feed air to 1.5MPa, toluene 10.0Kg, catalyst dosage is 0.6%wt of the reactant, when the temperature is raised to 150°C, start stirring, after 12 hours of reaction, the product is centrifugally settled, The supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 15.0%, and the selectivity of benzaldehyde was 65%.

Example 5

8.7Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.6Kg Ba(NO ₃ ) ₂ and 1.8Kg Al(NO ₃ ) ₃ ·9H ₂ O were made into 40L solution with deionized water; 1.0Kg Na ₂ CO ₃ Prepare a 40L solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hour, and add NH ₄ OH to control the pH of the mixed solution to 10.0. The obtained colloid is filtered or centrifugally dehydrated, washed to neutrality, dried at 100°C, placed at 500°C in _N atmosphere and calcined for 4 hours, and the obtained sample is placed in a 6.0% ammonium iodide aqueous solution with a mass concentration of 50L. And add 50L of 0.2mol/L P123, the temperature is controlled at 80°C, and the pH of the mixed solution is controlled by NH ₄ OH to 10.0. After 12 hours, 0.7Kg of Cu(NO ₃ ) ₂ ·3H ₂ O and 0.9Kg of Ni(NO ₃ ) ₂ ·6H ₂ O, and at the same time, add 30% H ₂ O ₂ aqueous solution with equal molarity to ammonium iodide, stir for 12 hours, and the obtained colloid is filtered or centrifugally dehydrated, dried at 100°C, and dried at 800°C The new catalyst required for calcination in _N2 gas for 6 hours. Add toluene and catalyst into a 100L autoclave, feed _O2 to 2.0MPa, toluene 10.0Kg, catalyst dosage is 1.0%wt of the reactant, when the temperature rises to 160°C, start stirring, after 8 hours of reaction, the product is settled by centrifugation , and the supernatant was analyzed by Agilent 6890 gas chromatography. The conversion rate of toluene was 45.0%, and the selectivity of benzaldehyde was 94%.

Example 6

8.7Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.7Kg Sr(NO ₃ ) ₂ ·4H ₂ O and 3.8Kg Al(NO ₃ ) ₃ ·9H ₂ O were prepared into 80L solution with deionized water; 1.0 Kg Na ₂ CO ₃ was made into 80L solution with deionized water. After the two solutions were mixed, they were vigorously stirred at 60°C for 0.5 hour, and NH ₄ OH was added to control the pH value of the mixed solution to 10.0. The resulting colloid was filtered or centrifugally dehydrated, washed with water until neutral, dried at 100°C, placed at 500°C in _N atmosphere and calcined for 4 hours, and the resulting sample was placed in a 2.0% ammonium bromide aqueous solution with a mass concentration of 50L. Add 50L 0.2mol/L P123 to it, control the temperature at 80°C, and use NH ₄ OH to control the pH of the mixed solution to 10.0. After 12 hours, add 0.7g of PdCl ₂ , and at the same time add the same molar amount of ammonium bromide 30% H ₂ O ₂ aqueous solution, stirred for 12 hours, the obtained colloid was filtered or centrifugally dehydrated, dried at 100°C, and calcined in N ₂ gas at 800°C for 6 hours for the required new catalyst. Add toluene and catalyst into a 100L autoclave, feed _O2 to 2.0MPa, toluene 10.0Kg, the catalyst dosage is 0.5%wt of the reactant, when the temperature rises to 160°C, start stirring, after 8 hours of reaction, the product is settled by centrifugation , and the supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 5.0%, and the selectivity of benzaldehyde was 76%.

Example 7

8.7Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 1.6Kg Ba(NO ₃ ) ₂ and 3.8Kg Al(NO ₃ ) ₃ ·9H ₂ O were made into 80L solution with deionized water; 1.0Kg Na ₂ CO ₃ Prepare 80 L of solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hour, and add NH ₄ OH to control the pH of the mixed solution to 10.0. The resulting colloid was filtered or centrifugally dehydrated, washed with water until neutral, dried at 100°C, placed at 500°C in _N atmosphere and calcined for 4 hours, and the resulting sample was placed in a 2.0% ammonium iodide aqueous solution with a mass concentration of 50L. 50L of 0.2mol/L CTAB was added therein, the temperature was controlled at 80°C, and the pH of the mixture was controlled by NH ₄ OH to 10.0. After 12 hours, 4.0g of PdCl ₂ and 8.0g of HAuCl ₄ ·3H ₂ O were added, At the same time, add 30% H ₂ O ₂ aqueous solution with the same molar number as ammonium iodide, stir for 12 hours, filter or centrifugally dehydrate the obtained colloid, dry at 100°C, and calcinate the required new catalyst in N ₂ gas at 800°C for 6 hours. Add toluene and catalyst into a 100L autoclave, feed air to 2.0MPa, toluene 10.0Kg, catalyst dosage is 0.5%wt of the reactant, when the temperature rises to 160°C, start stirring, after reacting for 8 hours, the product is centrifugally settled, The supernatant was analyzed by Agilent 6890 gas chromatography. The conversion of toluene was 35.0%, and the selectivity of benzaldehyde was 86%.

Example 8

6.1Kg Mg(NO ₃ ) ₂ ·6H ₂ O, 4.2Kg Ba(NO ₃ ) ₂ and 3.8Kg Al(NO ₃ ) ₃ ·9H ₂ O were made into 80L solution with deionized water; 1.0Kg Na ₂ CO ₃ Prepare 80 L of solution with deionized water, mix the two solutions, stir vigorously at 60°C for 0.5 hour, and add NH ₄ OH to control the pH of the mixed solution to 10.0. The resulting colloid was filtered or centrifugally dehydrated, washed with water until neutral, dried at 100°C, placed at 500°C in _N atmosphere and calcined for 4 hours, and the resulting sample was placed in a 2.0% ammonium iodide aqueous solution with a mass concentration of 50L. Add 50L of 0.2mol/L CTAB to it, control the temperature at 80°C, and use NH ₄ OH to control the pH of the mixture to 10.0. After 12 hours, add 4.0g of H ₂ PtCl ₆ ·6H ₂ O and 4.0Kg of HAuCl _4. 3H ₂ O, add 30% H ₂ O ₂ aqueous solution with the same molar number as ammonium iodide at the same time, stir for 12 hours, filter or centrifugally dehydrate the obtained colloid, dry at 100°C, and calcinate in N ₂ gas at 800°C 6 Hours require new catalysts. Add toluene and catalyst into a 100L autoclave, feed _O2 to 2.0MPa, toluene 10.0Kg, the catalyst dosage is 0.5%wt of the reactant, when the temperature rises to 160°C, start stirring, after 8 hours of reaction, the product is settled by centrifugation , and the supernatant was analyzed by Agilent 6890 gas chromatography. The conversion rate of toluene was 37.0%, and the selectivity of benzaldehyde was 90%.

Claims (5)

1. A novel catalyst for liquid phase highly selective catalytic oxidation of toluene, characterized in that: the catalyst is mainly based on the alkaline earth metal composite oxide of high temperature stability as a carrier; with highly active metals: V, Cr, Mn, Fe , Co, Ni, Cu, Au, Pd or Pt are catalytic oxidation active centers, and the content of supported metal elements accounts for 0.03-1.0% of the total mass of the catalyst, The above-mentioned preparation method for the preparation of benzaldehyde novel catalyst for liquid-phase selective oxidation of toluene comprises the following steps: (1) Prepare the mixed aqueous solution of divalent alkaline earth metal nitrate and aluminum nitrate, control the molar ratio of alkaline earth metal cations and aluminum ions at 2.0～5.0; control the total concentration of cations at 0.2～1.5mol/L; (2) Prepare ammonium carbonate aqueous solution, control the molar dosage of ammonium carbonate and aluminum nitrate to be the same, mix the above two solutions and fully stir for 0.5 hours, control the temperature at 60°C, use NH ₄ OH to control the pH value of the mixed solution during this process At 8-11.5, then filter or centrifugally dehydrate the resulting colloid, wash with water until neutral, and dry at 100°C. The obtained solid sample is calcined in _N2 gas at 300-700°C for 4 hours to obtain the corresponding metal composite oxide thing; (3) Place the obtained metal composite oxide in an aqueous solution of amine halide with a mass percent concentration of 1-10%, and add an equal volume of 0.1mol/L template aqueous solution to it, and control the temperature at 60-100°C and the pH value. At 8.0-11.5, add transition metal nitrate or precious metal salt after 12 hours, keep the molar number of transition metal nitrate as 5-20% of the molar number of alkaline earth metal, the molar number of noble metal is 0.1-1.0% of the molar number of alkaline earth metal, At the same time, add an appropriate amount of H ₂ O ₂ to keep the number of moles of H ₂ O ₂ equal to the number of amine halides, stir for 24 hours, filter the obtained colloid or centrifugal dehydration, dry at 100°C, and calcinate in nitrogen at 800-1200°C for 2 New catalyst required for ~10 hours. 2. The catalyst according to claim 1, characterized in that, the alkaline earth metal nitrate can be one or both of magnesium nitrate, calcium nitrate, strontium nitrate and barium nitrate. 3. The catalyst according to claim 1, characterized in that, said ammonium halide can be one or both of ammonium fluoride, ammonium chloride, ammonium bromide and ammonium iodide. 4. catalyzer as claimed in claim 1 is characterized in that, described templating agent can be hexadecyltrimethylammonium bromide, macrogol octylphenyl ether and polyoxyethylene-polyoxypropylene - one of the triblock copolymers of polyoxyethylene. 5. catalyst as claimed in claim 1 is characterized in that, described transition metal nitrate can be one or in vanadium nitrate, chromium nitrate, manganese nitrate, ferrous nitrate, cobalt nitrate, nickel nitrate, copper nitrate Two, the noble metal salt can be one or both of PdCl ₂ , HAuCl ₄ ·3H ₂ O and H ₂ PtCl ₆ ·6H ₂ O.