CN102701944A - Method for preparing 2-ethyl hexanoic acid by catalytically oxidizing 2-ethylhexanal by molybdovanadophosphoric acid - Google Patents

Abstract

The invention discloses a method for preparing 2-ethyl hexanoic acid by catalytically oxidizing 2-ethylhexanal by molybdovanadophosphoric acid, and relates to a method for preparing a chemical preparation. The method comprises the following steps: weighing molybdovanadophosphoric acid and dissolving the molybdovanadophosphoric acid in distilled water at first and then in hydrochloric acid to prepare a catalyst solution; adding 2-ethylhexanal and the prepared catalyst in an ordinary-pressure reaction device, slowly heating and stirring the mixture, regulating oxygen flux, and starting to introduce oxygen when the temperature rises to the reaction temperature; after the reaction is ended, separating out the aqueous phase solution on the lower layer to obtain organic phase matter on the upper layer; and depressurizing and distilling the organic phase matter to obtain colorless transparent and pungent oily liquid, 2-ethyl hexanoic acid. By changing the ratio of molybdenum to vanadium of the catalyst and optimizing the reaction condition, the conversion rate of the 2-ethylhexanal reaches above 99%, and the selection and yield of the 2-ethyl hexanoic acid reach above 98% respectively.

Description

Method for preparing 2-ethylhexanoic acid by catalytic oxidation of 2-ethylhexanal with phosphomolybdovanadium heteropolyacid

technical field

The invention relates to a preparation method of a chemical preparation, in particular to a method for preparing 2-ethylhexanoic acid by catalyzing and oxidizing 2-ethylhexanal with phosphomolybdovanadium heteropolyacid.

Background technique

The prepared phosphomolybdovanadium heteropolyacid has a Keggin structure, has a unique and stable molecular structure, and is easy to design at the molecular level to control its acidity and oxidation properties. The preparation of 2-ethylhexanoic acid by catalyzed air oxidation of 2-ethylhexanal by phosphomolybdovanadium heteropolyacid has not been reported so far. Using phosphomolybdovanadium heteropolyacid as a catalyst, under a certain reaction temperature and a certain air (oxygen) flow rate, it is used for the air oxidation of 2-ethylhexanal. The conversion rate of 2-ethylhexanal is the best. The selectivity of 2-ethylhexanoic acid is up to 99%. Prepare 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal with phosphorus molybdovanadium heteropolyacid. The catalyst has high activity, small dosage, and can be reused. Compared with potassium permanganate, nitric acid, etc., the conversion rate and yield increase 10-15%, and does not corrode reaction equipment. The preparation method has mild reaction conditions, simple and convenient operation, and reduces pollution of three wastes.

Contents of the invention

The object of the present invention is to provide a method for preparing 2-ethylhexanoic acid by catalytic oxidation of 2-ethylhexanal with phosphomolybdovanadium heteropolyacid. By adjusting the ratio of vanadium atoms to control the acidity and oxidative properties of the catalyst, the obtained highly catalytic phosphomolybdenum vanadium heteropolyacid catalyst has the advantages of small catalyst consumption, mild reaction conditions, easy operation, reusable catalyst, and no harm to equipment. Corrosion and other characteristics.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal by phosphomolybdovanade heteropolyacid, said method comprising the following process:

Weigh phosphomolybdovanadium heteropolyacid, dissolve it in distilled water, and then dissolve it in hydrochloric acid to prepare a catalyst solution. In the normal pressure reaction device, add 2-ethylhexanal and the prepared catalyst, slowly heat up, stir, and adjust Oxygen flow rate, when the temperature rises to the reaction temperature, oxygen is introduced. After the reaction, the lower aqueous phase solution is separated to obtain the upper organic phase substance. The organic phase substance is subjected to reduced pressure distillation to obtain a colorless, transparent and irritating Odor oily liquid --- 2-ethylhexanoic acid.

The method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal by the phosphomolybdovanadium heteropolyacid, in which the catalyzed oxidation of 2-ethylhexanal by the phosphomolybdovanadium heteropolyacid is used to prepare 2-ethylhexanal Hexanoic acid catalyst, and changing the ratio of vanadium atoms to control the acidity and oxidation performance of the catalyst, the expression is: H _3+n PMo _12-n V _n O ₄₀ xH ₂ O, where 0.5≤n≤6, 3≤ x≤40.

The method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal by the phosphomolybdovanadium heteropolyacid, which prepares the phosphomolybdovanadium heteropolyacid: weigh molybdate, phosphate and partial Vanadate, respectively dissolved in deionized water; put the phosphate solution in a constant temperature water bath at 80°C, stir, then slowly add the molybdate solution into the phosphate solution, and then slowly add dropwise to the mixed solution Acidify with concentrated sulfuric acid until the solution turns light yellow; add the metavanadate solution to the mixed solution acidified with sulfuric acid, continue to add concentrated sulfuric acid dropwise until the solution becomes a transparent orange-red solution, stop heating and stirring, and cool to room temperature; finally, add diethyl ether, shake fully, let stand for stratification, and separate the orange-red oily solution in the lower layer. After distilling off the diethyl ether, the orange-red powdery phosphomolybdovanadium heteropolyacid is obtained.

The method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal by the phosphomolybdovanadium heteropolyacid, which prepares phosphomolybdovanadium heteropolyacid: changing the amount of metavanadate solution to prepare different molybdenum vanadium ratios Phosphomolybdovanadium heteropolyacid.

The method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal by the phosphomolybdovanadium heteropolyacid, the molybdate used is ammonium, alkali metal, magnesium, etc. soluble in water molybdate, metavanadate The salt is metavanadate dissolved in water such as sodium and potassium; and the acidity and oxidative properties of the molybdenum vanadium ratio transformation catalyst are changed by adding the metavanadate.

The method for preparing 2-ethylhexanoic acid by catalyzing the oxidation of 2-ethylhexanal with phosphomolybdovanadium heteropolyacid, the catalyst used is phosphomolybdovanadium heteropolyacid, using deionized water and hydrochloric acid to prepare the catalyst solution, preparing the catalyst The concentration of the substance is 0.5-8mol/L, preferably 2-5 mol/L; the mass fraction of the catalyst is in the range of 1-10%, preferably in the range of 2-4%; the reaction temperature range is 40-120 °C, preferably 50-70 °C; oxygen flow rate is 0-20mL/s, preferably 4-10mL/s; reaction time is 2-8h, preferably 4-6h.

Advantage and effect of the present invention are:

1. The present invention provides phosphomolybdenum vanadium heteropoly acid H _3+n PMo _12-n V _n O ₄₀ xH ₂ O with a certain proportion of vanadium atoms. The heteropoly acid has stable chemical properties and good thermal stability, and its acidity And oxidative properties can be transformed into each other by controlling the ratio of vanadium atoms, and it has excellent catalytic activity for the oxidation of 2-ethylhexanal to 2-ethylhexanoic acid. The phosphorus molybdenum vanadium heteropolyacid catalyst provided by this invention and the preparation method of 2-ethylhexanoic acid obtained by air oxidation of 2-ethylhexanal can be completed only under mild reaction conditions and simple process, And the three wastes pollution is reduced in the synthesis process.

2. The present invention utilizes the phosphorus molybdenum vanadium heteropolyacid with suitable molybdenum vanadium ratio to catalyze the preparation method of 2-ethylhexanal to prepare 2-ethylhexanoic acid. Phosphorus molybdenum vanadium heteropolyacid solid catalyst H _3+n PMo _12-n V _n O ₄₀ xH ₂ O, catalytic oxidation of 2-ethylhexanal with high conversion rate, good selectivity, 2-ethylhexanoic acid yield high. Moreover, the acidity and oxidative properties of the catalyst are controlled by adjusting the ratio of vanadium atoms, the selectivity and yield of 2-ethylhexanoic acid are improved, the best catalytic effect is obtained, and the production cost of 2-ethylhexanoic acid can be reduced. The procedure prepares 2-ethylhexanoic acid, the reaction conditions are mild, and the operation is simple and convenient.

Description of drawings

Fig. 1 is the X-ray diffraction figure of catalyst phosphorus molybdenum vanadium heteropolyacid H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O used in the present invention;

Fig. 2 is the infrared spectrogram of catalyst phosphorus molybdenum vanadium heteropolyacid H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O used in the present invention;

Fig. 3 is the infrared spectrogram of the obtained 2-ethylhexanoic acid of the present invention.

Note: Fig. 1-Fig. 3 of the present invention are analysis schematic diagrams of the product state, and the unclear text or image in the figure does not affect the understanding of the technical solution of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with examples.

Figure 1 is H ₄ PMo prepared by weighing 20.00g sodium molybdate, 6.00g disodium hydrogen phosphate, 1.85g sodium metavanadate, and placing the disodium hydrogen phosphate solution in a constant temperature water bath at 80°C. X-ray diffraction pattern of ₁₁ VO ₄₀ ·32H ₂ O catalyst.

Figure 2 is the infrared spectrum of H ₄ PMo ₁₁ VO ₄₀ ·32H ₂ O.

Figure 3 is the catalytic oxidation of 2-ethylhexanal with H ₄ PMo ₁₁ VO ₄₀ ·32H ₂ O, the reaction temperature is 60°C, the mass fraction of the catalyst is 3%, and the dilute hydrochloric acid solution is used as the solvent, and the concentration of the substance is 2mol/L, the oxygen flow rate is 5mL/s, and the reaction time is 5h, the infrared spectrum of the 2-ethylhexanoic acid prepared.

Embodiment 1: Weigh 20.00 g of sodium molybdate, 6.00 g of disodium hydrogen phosphate, and 1.85 g of sodium metavanadate, and dissolve them in deionized water respectively. Put the disodium hydrogen phosphate solution in a constant temperature water bath at 80°C, then slowly add the sodium molybdate solution into the disodium hydrogen phosphate solution, then slowly add concentrated sulfuric acid to the mixed solution for acidification until the solution becomes pale yellow. Add the sodium metavanadate solution into the mixed solution acidified with sulfuric acid, and continue to add concentrated sulfuric acid dropwise under vigorous stirring until the solution becomes a transparent orange-red solution. Heating and stirring were stopped, and the mixed solution of the three solutions was cooled to room temperature. Finally, the mixed solution was transferred to a separatory funnel, and a little ether was added. After fully shaking, the layers were allowed to stand and the orange-red oily solution in the lower layer was separated. Repeat the separation and distill off the ether to obtain the orange-red powdery phosphomolybdovanade heteropolyacid (H ₄ PMo ₁₁ VO ₄₀ ·32H ₂ O) catalyst.

Embodiment 2: H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O is used as a catalyst, dilute hydrochloric acid solution is used as a solvent, the concentration of the substance is 2mol/L, the mass fraction in the reaction system is 2%, and the flow rate of oxygen is 5mL/ s, the reaction time is 4h, the reaction temperature is 40-120°C, and 2-ethylhexanal is oxidized to obtain 2-ethylhexanoic acid. Under these conditions, when the reaction temperature is 60°C, the conversion rate of 2-ethylhexanal is 92.73%, the selectivity of 2-ethylhexanoic acid is 92.64%, and the yield of 2-ethylhexanoic acid is 91.59%.

Embodiment 3: H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O is used as the catalyst, dilute hydrochloric acid solution is used as the solvent, the concentration of the substance is 2mol/L, the mass fraction in the reaction system is 2%, and the flow rate of oxygen is 5mL/ s, the reaction temperature is 60°C, the reaction time is 1h, 2h, 3h, 4h, 5h, 6h, 7h, and 2-ethylhexanoic acid is obtained by oxidation of 2-ethylhexanal. Under these conditions, when the reaction time was 7 hours, the conversion rate of 2-ethylhexanal was 95.57%, and the selectivity of 2-ethylhexanoic acid was 95.44%.

Embodiment 4: H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O is used as catalyst, dilute hydrochloric acid solution is used as solvent, the concentration of substance is 2mol/L, the flow rate of oxygen is 5mL/s, the reaction temperature is 60°C, and the reaction time is 4h, the mass fraction of H ₄ PMo ₁₁ VO ₄₀ ·32H ₂ O in the reaction system is 0.5%-10%, and 2-ethylhexanal is oxidized to produce 2-ethylhexanoic acid. Under these conditions, when the mass fraction of H ₄ PMo ₁₁ VO ₄₀ ·32H ₂ O in the reaction system is 3%, the conversion rate of 2-ethylhexanal is 96.73%, and the selectivity of 2-ethylhexanoic acid is 95.44% %, the yield of 2-ethylhexanoic acid is 95.59%.

Embodiment 5: H ₄ PMo ₁₁ VO ₄₀ 32H ₂ O is used as the catalyst, dilute hydrochloric acid solution is used as the solvent, the concentration of the substance is 2mol/L, the mass fraction in the reaction system is 3%, and the reaction temperature is 60°C , the reaction time is 5h, the flow rate of oxygen is 1-20 mL/s, and 2-ethylhexanoic acid is obtained by oxidation of 2-ethylhexanal. Under these conditions, when the flow rate of oxygen was 10 mL/s, the conversion rate of 2-ethylhexanal was 99.83%, the selectivity of 2-ethylhexanoic acid was 98.34%, and the yield of 2-ethylhexanoic acid was 98.79%.

Claims (6)

1. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal prepares the method for 2 ethyl hexanoic acid, it is characterized in that, said method comprises following process:

Take by weighing phosphorus molybdenum vanadium heteropolyacid, be dissolved in the zero(ppm) water, be dissolved in again and be mixed with catalyst solution in the hydrochloric acid, in the synthesis under normal pressure device; The catalyzer that adds the 2-ethyl hexanal and configure slowly heats up, stirs, and regulates oxygen flow; When temperature rises to temperature of reaction, begin aerating oxygen, reaction is isolated lower floor's aqueous phase solution after finishing; Obtain the organic phase material on upper strata, this organic phase material is carried out underpressure distillation, obtain the oily liquids that water white transparency has irritating smell---2 ethyl hexanoic acid.

2. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal according to claim 1 prepares the method for 2 ethyl hexanoic acid; It is characterized in that; The said catalyzer for preparing 2 ethyl hexanoic acid with phosphorus molybdenum vanadium heteropolyacid as catalyzed oxidation 2-ethyl hexanal; And changing vanadium atom ratio control acidity of catalyst and oxidisability performance, expression formula is: H _3+nPMo _12-nV _nO ₄₀XH ₂O, 0.5≤n in the formula≤6,3≤x≤40.

3. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal according to claim 1 prepares the method for 2 ethyl hexanoic acid; It is characterized in that; Preparation phosphorus molybdenum vanadium heteropolyacid: take by weighing molybdate, phosphoric acid salt and metavanadate by stoichiometric ratio, be dissolved in respectively in the deionized water; Aqueous phosphate solution is placed 80 ℃ water bath with thermostatic control, stir, then molybdate solution is slowly joined in the aqueous phosphate solution, in mixing solutions, slowly drip vitriol oil acidifying again, become faint yellow up to solution; Metavanadate solution is added in the mixing solutions that sulfuric acid acidation crosses, continue to drip the vitriol oil, become transparent orange-red solution, stop heating and stir, be cooled to room temperature until solution; At last, add ether, fully after the vibration, standing demix is told the orange-red oily solution of lower floor, steam ether after, promptly get orange red Powdered phosphorus molybdenum vanadium heteropolyacid.

4. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal according to claim 3 prepares the method for 2 ethyl hexanoic acid, it is characterized in that the preparation phosphorus molybdenum vanadium heteropolyacid: change the amount of metavanadate solution, prepare the phosphorus molybdenum vanadium heteropolyacid of different molybdenum vanadium ratios.

5. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal according to claim 3 prepares the method for 2 ethyl hexanoic acid, it is characterized in that, used molybdate is water-soluble molybdates such as ammonium, basic metal, magnesium, and metavanadate is water-soluble metavanadates such as sodium, potassium; And through adding metavanadate change molybdenum vanadium than changing acidity of catalyst and oxidisability performance.

6. phosphorus molybdenum vanadium heteropolyacid catalyzed oxidation 2-ethyl hexanal according to claim 1 prepares the method for 2 ethyl hexanoic acid; It is characterized in that; Catalyst system therefor is a phosphorus molybdenum vanadium heteropolyacid; Utilize deionized water and hydrochloric acid preparation catalyst solution, the amount of substance concentration of preparation catalyzer is 0.5-8mol/L, is preferably 2-5 mol/L; The massfraction of catalyzer is preferably in the 2-4% scope in the 1-10% scope; Range of reaction temperature is 40-120 ℃, is preferably in 50-70 ℃; Oxygen flow is 0-20mL/s, is preferably in 4-10mL/s; Reaction times is 2-8h, is preferably 4-6h.

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