Preparation method of dehydroacetic acid and sodium salt thereof

Abstract

The invention provides a preparation method of a dehydroacetic acid. The preparation method sequentially comprises the following steps: a condensation reaction step and an after-treatment step. The preparation method is characterized in that in the condensation reaction step, after a catalyst and a polymerization inhibitor are added into a toluene solvent, ketene dimer is dropwise added, and the heat is preserved to generate a toluene dehydroacetic acid solution; in the after-treatment step, the obtained toluene dehydroacetic acid solution is cooled, filtered, washed and centrifuged to obtain the dehydroacetic acid; and the catalyst is an ethylenediamine acetate catalyst. The invention further provides a preparation method of sodium acetate dehydrogenation, wherein the preparation method comprises the following steps of adding sodium hydroxide into the toluene dehydroacetic acid solution which is obtained in the condensation reaction step; neutralizing and adjusting pH; carrying out active carbon decoloration; and condensing and crystallizing to obtain the sodium acetate dehydrogenation. According to the preparation method of the dehydroacetic acid provided by the invention, excessive polymerization of the ketene dimer is reduced, the side reaction is reduced, and the yield of dehydroacetic acid is improved. The invention further provides a preparation method of the sodium acetate dehydrogenation, wherein the dehydroacetic acid is not needed to be separated, and the yield of sodium dehydroacetate is improved.

Description

technical field

[0001] The invention belongs to the field of chemical production, and in particular relates to a preparation method of dehydroacetic acid and its sodium salt. Background technique

[0002] Dehydroacetic acid, English name: Dehydroacetic Acid, alias DHA, 3-acetyl-6-methyl-2H-pyran-2,4(3H)dione, color to white needle-like or plate-like crystals or white crystalline powder , odorless, slightly sour, melting point: 108~111°C (sublimation), boiling point: 269.9°C, easily soluble in aqueous solution of fixed alkali, insoluble in water, 1g is soluble in 35mL ethanol and 5mL acetone, its dehydroacetic acid A saturated aqueous solution has a pH of 4.

[0003] Prior Art Synthetic Process:

[0004] ①Under alkaline conditions (such as sodium alkoxide, sodium phenoxide, sodium hydroxide, sodium acetate, pyrazole, triethylamine, etc.) or under the catalysis of aluminum bromide, diketene is condensed to obtain dehydroacetic acid. Its operation method is as follows. Add ...

Examples

Embodiment 1

[0053] The preparation of amide acetate catalyst comprises the following steps:

[0054] Add 23.5g (0.21mol) triethylenediamine and 50g water into the three-necked flask, slowly add 12.0g (0.2mol) glacial acetic acid dropwise, after the addition is complete, heat to 60°C, continue the reaction for 2h, and concentrate to dryness under negative pressure to obtain Yellow viscous liquid triethylenediamine acetate, yield 96%.

[0055] The preparation method of amines acetate catalysts such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine is the same as embodiment 1.

[0056] A kind of preparation technology of dehydroacetic acid, comprises the following steps:

[0057] In a 500ml three-necked flask, add 300g of solvent toluene, 5g of triethylenediamine acetate catalyst, and 6g of p-tert-butylquinone as a polymerization inhibitor. 100 g of diketene was added dropwise, the addition was completed within 5 hours, and the mixture was kept at 40°C for 4 hours. The g...

Embodiment 2

[0059] A kind of preparation technology of sodium dehydroacetate, comprises the following steps:

[0060] Add 300 g of solvent toluene, 4 g of diethylenetriamine acetate catalyst (the preparation method is the same as in Example 1) and 5 g of 2,6-di-tert-butyl-p-cresol into a 500 ml three-necked flask. 100 g of diketene was added dropwise, the addition was completed within 5 hours, and the temperature was kept at 50° C. for 3 hours. Add 5% sodium hydroxide to the toluene solution for neutralization, adjust the pH value to 9-11, separate layers, add 10% activated carbon to the water layer for decolorization, concentrate and crystallize, and centrifuge to obtain 119.2 g of sodium dehydroacetate. The mother liquor is applied mechanically, and the product is collected. The rate is 96.3%, and the content is 99.8%.

Embodiment 3

[0062] A kind of preparation technology of sodium dehydroacetate, comprises the following steps:

[0063] In a 500ml three-necked flask, add 300g of solvent toluene, 3g of triethylenetetramine acetate catalyst (the preparation method is the same as in Example 1), polymerization inhibitor p-tert-butylquinone and 2,6-di-tert-butyl p-cresol 4g. 100 g of diketene was added dropwise, and the dropwise addition was completed within 5 hours, and then kept at 55° C. for 3.5 hours. Add 5% sodium hydroxide to the toluene solution to neutralize, adjust ph9-11, separate layers, add 10% activated carbon to the water layer for decolorization, concentrate and crystallize, centrifuge to obtain 119.6g of product sodium dehydroacetate, apply mechanically to the mother liquor, and the product yield is 96.5%, content 99.9%.

technical field

[0001] The invention belongs to the field of chemical production, and in particular relates to a preparation method of dehydroacetic acid and its sodium salt. Background technique

[0002] Dehydroacetic acid, English name: Dehydroacetic Acid, alias DHA, 3-acetyl-6-methyl-2H-pyran-2,4(3H)dione, color to white needle-like or plate-like crystals or white crystalline powder , odorless, slightly sour, melting point: 108~111°C (sublimation), boiling point: 269.9°C, easily soluble in aqueous solution of fixed alkali, insoluble in water, 1g is soluble in 35mL ethanol and 5mL acetone, its dehydroacetic acid A saturated aqueous solution has a pH of 4.

[0003] Prior Art Synthetic Process:

[0004] ①Under alkaline conditions (such as sodium alkoxide, sodium phenoxide, sodium hydroxide, sodium acetate, pyrazole, triethylamine, etc.) or under the catalysis of aluminum bromide, diketene is condensed to obtain dehydroacetic acid. Its operation method is as follows. Add ...

Examples

Embodiment 1

[0053] The preparation of amide acetate catalyst comprises the following steps:

[0054] Add 23.5g (0.21mol) triethylenediamine and 50g water into the three-necked flask, slowly add 12.0g (0.2mol) glacial acetic acid dropwise, after the addition is complete, heat to 60°C, continue the reaction for 2h, and concentrate to dryness under negative pressure to obtain Yellow viscous liquid triethylenediamine acetate, yield 96%.

[0055] The preparation method of amines acetate catalysts such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine is the same as embodiment 1.

[0056] A kind of preparation technology of dehydroacetic acid, comprises the following steps:

[0057] In a 500ml three-necked flask, add 300g of solvent toluene, 5g of triethylenediamine acetate catalyst, and 6g of p-tert-butylquinone as a polymerization inhibitor. 100 g of diketene was added dropwise, the addition was completed within 5 hours, and the mixture was kept at 40°C for 4 hours. The g...

Embodiment 2

[0059] A kind of preparation technology of sodium dehydroacetate, comprises the following steps:

[0060] Add 300 g of solvent toluene, 4 g of diethylenetriamine acetate catalyst (the preparation method is the same as in Example 1) and 5 g of 2,6-di-tert-butyl-p-cresol into a 500 ml three-necked flask. 100 g of diketene was added dropwise, the addition was completed within 5 hours, and the temperature was kept at 50° C. for 3 hours. Add 5% sodium hydroxide to the toluene solution for neutralization, adjust the pH value to 9-11, separate layers, add 10% activated carbon to the water layer for decolorization, concentrate and crystallize, and centrifuge to obtain 119.2 g of sodium dehydroacetate. The mother liquor is applied mechanically, and the product is collected. The rate is 96.3%, and the content is 99.8%.

Embodiment 3

[0062] A kind of preparation technology of sodium dehydroacetate, comprises the following steps:

[0063] In a 500ml three-necked flask, add 300g of solvent toluene, 3g of triethylenetetramine acetate catalyst (the preparation method is the same as in Example 1), polymerization inhibitor p-tert-butylquinone and 2,6-di-tert-butyl p-cresol 4g. 100 g of diketene was added dropwise, and the dropwise addition was completed within 5 hours, and then kept at 55° C. for 3.5 hours. Add 5% sodium hydroxide to the toluene solution to neutralize, adjust ph9-11, separate layers, add 10% activated carbon to the water layer for decolorization, concentrate and crystallize, centrifuge to obtain 119.6g of product sodium dehydroacetate, apply mechanically to the mother liquor, and the product yield is 96.5%, content 99.9%.