Method for preparing azelaic acid by catalyzing oleic acid oxidation through supported heteropolyacid salt

Abstract

The invention discloses a preparation method of azelaic acid, which is characterized in that under a solvent-free condition, a reusable supported heteropolyacid salt catalyst is adopted to catalyze oleic acid to oxidize so as to prepare the azelaic acid. The method is characterized in that the supported heteropolyacid salt catalyst is supported phosphotungstate or supported silicotungstate, and the oxidizing agent is hydrogen peroxide. Compared with the prior art, the method has the advantages that the catalyst can be efficiently separated and reused, the production cost is reduced, the reaction process is simple, and the process is clean.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing azelaic acid by catalyzing oxidation of oleic acid with a supported heteropoly acid salt catalyst. BACKGROUND

[0002] Azelaic acid, also known as rhododendric acid, is a high value-added fine chemical. Azelaic acid is an intermediate for producing nylon 9 and nylon 69, and can improve the flexibility of unsaturated polyester; it can also be used for producing azelaic acid plasticizer, which is suitable for artificial leather, film, sheet, wire and cable sheath, and is widely used in plastic and rubber additives. It is also widely used in the fields of lubricating oil, perfume, oil agent, flocculant, flame retardant and polyacrylamide resin, etc. In addition, azelaic acid has significant effects in the fields of electrolytic capacitor manufacturing and skin disease prevention. Especially in recent years, with the application of azelaic acid in the fields of medicine and cosmetics, the demand for high-purity azelaic acid in China has been increasing year by year.

[0003] At present, the main method for producing azelaic acid is the oxidation cracking method of unsaturated fatty acid, such as ozone oxidation method, nitric acid oxidation method, potassium permanganate oxidation method and hydrogen peroxide oxidation method. The ozone oxidation method is the main method for preparing azelaic acid at present, which has low yield, high energy consumption and high requirements for reaction equipment; the nitric acid oxidation method has the defects of strong corrosion to equipment, serious environmental pollution and low selectivity; the potassium permanganate oxidation method has low product yield, high production cost, and the by-product manganese dioxide has a complex post-treatment process and can cause environmental pollution. The hydrogen peroxide oxidation method is currently recognized as a clean process for preparing azelaic acid, which has the advantages of high product yield, simple process and no pollution. The reported catalyst system is mainly homogeneous catalyst system such as tungstic acid, sodium tungstate and phosphotungstic acid, which has the disadvantages of difficult recovery and reuse of catalyst, and high reaction cost. Therefore, it is of great significance to develop a supported catalyst for catalyzing oxidation of oleic acid to prepare azelaic acid. SUMMARY

[0004] The present application improves the above-mentioned existing azelaic acid preparation method, and proposes a method for preparing azelaic acid by catalyzing oxidation of oleic acid with a reusable supported heteropoly acid salt catalyst under solvent-free conditions.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A method for preparing azelaic acid by catalyzing oxidation of oleic acid with a supported heteropoly acid salt catalyst, characterized in that: the reaction is carried out under solvent-free conditions, the supported heteropoly acid salt catalyst is a supported phosphotungstate or a supported silicotungstate, and the oxidizing agent is hydrogen peroxide.

[0006] Preferably, the phosphotungstate is [(C 18 H 37)2N(CH3)2]3[P(W3O 10 )4]、[(C8H 17 )3NCH3]3[P(W3O 10 )4]、 [π-C5H5NC 16 H 33 ]3[P(W3O 10 )4]、 [π-C5H5NC 16 H 33 ]3[PO4(WO3)4] or [(C 18 H 37 )2N(CH3)2]3[PO4(WO3)4].

[0007] More preferably, the supported tungstophosphoric acid salt is prepared by one of the following ways: Way one, first dissolve tungstophosphoric acid in hydrogen peroxide, then add quaternary ammonium salt and continue to react for a certain time, add carrier and continue to react for a certain time, filter and dry to obtain the supported tungstophosphoric acid salt; Way two, first dissolve tungstic acid in hydrogen peroxide, then add phosphoric acid and carrier and continue to react for a certain time, add quaternary ammonium salt and continue to react for a certain time, filter and dry to obtain the supported tungstophosphoric acid salt; The quaternary ammonium salt is [(C 18 H 37 )2N(CH3)2]Cl, [(C8H 17 )3NCH3]Cl, [π-C5H5NC 16 H 33 ]Cl.

[0008] Preferably, the silicotungstic acid salt is [(C8H 17 )3NCH3]4[Si(W3O 10 )4]、[(C 18 H 37 )2N(CH3)2]4[Si(W3O 10 )4] or [π-C5H5NC 16 H 33 ]4[Si(W3O 10 )4].

[0009] Preferably, the carrier of the supported heteropoly acid salt catalyst is alumina, silica or titanium silicalite.

[0010] Preferably, the dosage of the supported heteropoly acid salt catalyst is 5-20 wt.% of the amount of oleic acid, more preferably 6-10 wt.%.

[0011] Preferably, the hydrogen peroxide concentration is 30-50 wt.%.

[0012] Preferably, the molar ratio of H2O2 to oleic acid is 2-8:1, more preferably 4-8:1.

[0013] Preferably, the reaction temperature is 80-100°C, more preferably 95-100°C.

[0014] Preferably, the reaction time is 6-12h, more preferably 8-10h.

[0015] Compared with the prior art, the method of the present application can realize efficient separation and reuse of the catalyst, reduce production cost, and the reaction is carried out under solvent-free conditions, the process is simple and clean. DETAILED DESCRIPTION

[0016] The technical solutions of the present application are further described below in combination with examples.

[0017] Unless otherwise specified, each reagent and raw material used in the present application is a commercially available product.

[0018] Example 1 Preparation process of supported heteropoly acid salt [(C 18 H 37 )2N(CH3)2]3[P(W3O 10 )4]@Al2O3: phosphotungstic acid (36g, 12.5mmol) was added to 150ml 30% hydrogen peroxide, and a dichloromethane solution (200ml) of dioctadecyldimethylammonium chloride (14.7g, 25mmol) was added dropwise, and the reaction was continued at room temperature for 1 hour, then mesoporous Al2O3 (37.5g) was added and the reaction was continued at room temperature for 4 hours. After filtration, the yellowish solid was dried.

[0019] Example 2 Preparation process of supported heteropoly acid salt [(C 18 H 37 )2N(CH3)2]3[P(W3O 10 )4]@Al2O3-1: phosphotungstic acid (36g, 12.5mmol) was added to 150ml deionized water, and a dichloromethane solution (200ml) of dioctadecyldimethylammonium chloride (14.7g, 25mmol) was added dropwise, and the reaction was continued at room temperature for 1 hour, then mesoporous Al2O3 (37.5g) was added and the reaction was continued at room temperature for 4 hours. After filtration, the yellowish solid was dried.

[0020] Example 3 Preparation process of supported heteropoly acid salt [(C 18 H37 )2N(CH3)2]3[P(W3O 10 )4]@SiO2 was prepared as in Example 1. The difference is that mesoporous Al2O3 was replaced by SiO2.

[0021] Example 4 supported heteropoly salt [(C8H 17 )3NCH3]3[P(W3O 10 )4]@Al2O3 was prepared as in Example 1. The difference is that dioctadecyldimethylammonium chloride was replaced by trioctylmethylammonium chloride.

[0022] Example 5 supported heteropoly salt [π-C5H5NC 16 H 33 ]3[PO4(WO3)4]@Al2O3 was prepared as follows: tungstic acid (12.5 g, 50 mmol) was added to 30% hydrogen peroxide (50 ml) and heated to 60°C with vigorous stirring until the tungstic acid was completely dissolved to give a light yellow solution; after the solution was cooled to room temperature, 15 ml of 80% H3PO4 (1.6 g, 12.5 mmol) aqueous solution was added and diluted with deionized water to 150 ml, and mesoporous Al2O3 (37.5 g) was added and reacted at room temperature for 30 minutes; a solution of chlorohexadecylpyridine (9.42 g, 25 mmol) in dichloromethane (200 ml) was added dropwise and the reaction was continued at room temperature for 4 hours; after filtration, the light yellow solid was dried.

[0023] Example 6 In a 500 ml three-necked flask equipped with a mechanical stirrer, a thermometer and a condenser, 100 g of oleic acid and 10.0 g of [(C 18 H 37 )2N(CH3)2]3[P(W3O 10 )4]@Al2O3 were added successively, heated to 60°C with stirring, and 120 ml of 50% hydrogen peroxide was added in portions, with the temperature controlled not to exceed 105°C. The reaction was continued at 95-100°C for 8 hours. After the reaction was completed, the catalyst was separated by hot filtration and could be reused after drying. The filtrate was allowed to stand to separate into layers, the lower aqueous phase was cooled and azelaic acid was precipitated, which was filtered and dried, weighed and analyzed; the upper layer was the oil phase. The azelaic acid powder and the oil phase were methyl esterified respectively and analyzed by gas chromatography, the conversion of oleic acid was 95% and the selectivity of azelaic acid was 84%.

[0024] Example 7 The reaction conditions were the same as in Example 6. The difference is that [(C 18 H 37 )2N(CH3)2]3[P(W3O 10)4]@Al203-1 as catalyst, the conversion of oleic acid is 78%, and the selectivity of azelaic acid is 85%.

[0025] Example 8 The reaction conditions are the same as in Example 6. The difference is that [(C8H 18 H 37 )2N(CH3)2]3[P(W3O 10 )4]@Si02 as catalyst, the conversion of oleic acid is 76%, and the selectivity of azelaic acid is 80%.

[0026] Example 9 The reaction conditions are the same as in Example 6. The difference is that [(C8H 17 )3NCH3]3[P(W3O 10 )4]@Al203 as catalyst, the conversion of oleic acid is 98%, and the selectivity of azelaic acid is 87%.

[0027] Example 10 The reaction conditions are the same as in Example 6. The difference is that [π-C5H5NC 16 H 33 ]3[PO4(WO3)4]@Al203 as catalyst, the conversion of oleic acid is 82%, and the selectivity of azelaic acid is 85%.

[0028] Examples 11-15 The operation process of Examples 11-15 is the same as that of Example 5, the catalyst is [(C8H 17 )3NCH3]3[P(W3O 10 )4]@Al203, and the reaction conditions and results are shown in Table 1.

[0029] Table 1 Reaction conditions of epoxidation catalyzed by [(C8H 17 )3NCH3]3[P(W3O 10 )4]@Al203

[0030] Example 16 The catalyst is recovered after the reaction of Example 9 is completed, and is repeatedly used under the same conditions, and the reaction results are shown in Table 2.

[0031] Table 2 Effect of recycling of [(C8H 17 )3NCH3]3[P(W3O 10 )4]@Al203

[0032] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing azelaic acid by oxidizing oleic acid using a supported heteropolyacid salt catalyst, characterized in that: The reaction is carried out in the absence of a solvent. The supported heteropolyacid salt catalyst is supported phosphotungstate or supported silicotungstate, and the oxidant is hydrogen peroxide.

2. The preparation method according to claim 1, wherein: The phosphotungstate is [(C 18 H 37 )2N(CH3)2]3[P(W3O 10 )4]、[(C8H 17 )3NCH3]3[P(W3O 10 )4]、 [π-C5H5NC] 16 H 33 ]3[P(W3O 10 )4],[π-C5H5NC 16 H 33 ]3[PO4(WO3)4] or [(C 18 H 37 )2N(CH3)2]3[PO4(WO3)4] .

3. The preparation method according to claim 1 or 2, characterized in that: The supported phosphotungstate is prepared by one of the following methods: Method 1: first dissolve phosphotungstic acid in hydrogen peroxide, then add quaternary ammonium salt and react for a certain time, then add carrier and continue to react for a certain time, filter and dry to obtain the supported phosphotungstic acid; Method 2: first dissolve tungstic acid in hydrogen peroxide, then add phosphoric acid and the carrier to react for a certain time, then add quaternary ammonium salt and continue to react for a certain time, filter and dry to obtain the supported phosphotungstate; The quaternary ammonium salt is [(C 18 H 37 )2N(CH3)2]Cl, [(C8H 17 )3NCH3]Cl, [π-C5H5NC 16 H 33 ]Cl.

4. The preparation method according to claim 1, wherein: The silicotungstate is [(C8H 17 )3NCH3]4[Si(W3O 10 )4], [(C 18 H 37 )2N(CH3)2]4[Si(W3O 10 )4] or [π-C5H5NC 16 H 33 ]4[Si(W3O 10 )4].

5. The preparation method according to claim 1, wherein: The carrier of the supported heteropolyacid salt catalyst is alumina, silicon dioxide or titanium silicon molecular sieve.

6. The preparation method according to claim 1, wherein: The amount of the supported heteropolyacid salt catalyst is 5-20 wt.% of the oleic acid feed amount, preferably 6-10 wt.%.

7. The preparation method according to claim 1, wherein: The concentration of the hydrogen peroxide is 30% to 50%.

8. The preparation method according to claim 1, wherein: The molar ratio of H2O2 to oleic acid is 2-8:1, preferably 4-8:

1.

9. The preparation method according to claim 1, wherein: The reaction temperature is 80-100°C, preferably 95-100°C.

10. The preparation method according to claim 1, characterized in that: The reaction time is 6 to 12 hours, preferably 8 to 10 hours.

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