The way to obtain benzoic acid or sodium benzoate

 

(57) Abstract:

The invention relates to the field of organic chemistry, specifically to a method for producing benzoic acid (Bq) or sodium benzoate (bn), the difference is that BC separated from the aqueous phase of oxidate obtained in the oxidation of toluene in the presence of water and sodium carbonate (KN), by evaporation of the aqueous phase with obtaining bn containing up to 20% ash, which is placed in a vertical reactor, for example type "Soxhlet", and the top serves aqueous organic solvent, for example ethanol, or acetone, or methyl ethyl ketone, containing 10 to 30% water, and carbon dioxide under pressure and bottom removed BC in the solvent. To obtain pure bn, oxidat evaporated, loaded into a column type apparatus, and the top serves the solvent, providing a gradual dissolution of the bn and not dissolving soda, for example, water, acetone or ethanol. These differences in the way that allow you to get BK or bn high purity waste-free environmentally friendly technologies. 1 Il.

The invention relates to the field of organic chemistry, refers to aromatic acids, in particular the receipt of benzoic acid and sodium benzoate, and can be used in chemiczna from her sodium benzoate by the reaction of neutralization) oxygen at elevated temperature and pressure in the presence of catalysts, for example, Co-Mn-Br [1] or on the basis of benzoate metal (Mn and/or Ni) and promoter - bromine compounds [2].

A disadvantage of the known methods is the low performance, corrosion of equipment bromine, high energy consumption, technological difficulties in the allocation of benzoic acid from oxidate, difficulty cleaning it of impurities - diphenyloxide, methylbiphenyl etc.

Closest to the proposed technical essence is a method for benzoic acid by oxidation of toluene with oxygen at a temperature of 240 - 275oC and a pressure of 7.5 to 15.0 MPa in the presence of water and sodium carbonate in 2 - 6 normal concentration of the latter in the aqueous phase and the volume ratio of toluene : a mixture of sodium carbonate and water 1 - 5 : 5 - 1 for 5 to 30 minutes to obtain an organic and aqueous phase, followed by additional oxidation of the obtained aqueous phase for 1 to 6 minutes and the selection of the received oxidate benzoic acid by acidification with a solution of mineral acids [3]. In the specified way oxidat is a mixture of water, sodium benzoate and soda.

The disadvantage of this method is unproductive consumption of soda and mineral acids, the presence of significant colcheste is the creation of clean and waste-free technologies for clean benzoic acid and pure sodium benzoate.

This goal is achieved by a method of obtaining benzoic acid or sodium benzoate by oxidation of toluene with oxygen at a temperature of 240 - 275oC and a pressure of 7.5 to 15.0 MPa in the presence of water and sodium carbonate in 2 - 6 normal concentration of the latter in the aqueous phase and the volume ratio of toluene : a mixture of sodium carbonate and water 1 - 5 : 5 - 1 for 5 to 30 minutes with obtaining organic and aqueous phases are separated, the organic phase is returned to the step of oxidation, and water cooksley passing air under the same conditions as at the stage of oxidation, for 1 to 6 minutes, the resulting aqueous oxidat evaporated to a residual moisture content of 1 - 3% and any resulting sodium benzoate (containing up to 20% NaHCO3) are placed in a vertical reactor, for example, type the Soxhlet, in which the top at the same time serves aqueous organic solvent and carbon dioxide under pressure and below the removed solution of benzoic acid. Next, the solvent is distilled off and return in the process. Soda remains in the reactor and can be used at the stage of oxidation. Use of organic solvents, soluble in water and well-dissolving benzoic acid, for example 10 to 30% aqueous solutions of acetone or alcohol, and Saga excessive consumption of reagents.

Under these conditions, carbon dioxide and water interact with the sodium benzoate with the formation of benzoic acid. Because this interaction occurs with evolution of heat, cooling is required to avoid solvent evaporation.

The difference from the prototype stage is the selection of benzoic acid from the aqueous phase of oxidate, namely the simultaneous processing of aqueous solution of organic solvent and carbon dioxide under pressure.

These differences in the method of obtaining benzoic acid allow you to create waste-free environmentally friendly technology:

- excluded losses soda and consumption of mineral acid;

- there are no acidic wastewater.

To obtain pure sodium benzoate oxidat evaporated, loaded into a column type apparatus and the top serves the solvent, providing a gradual dissolution of benzoate and not dissolving soda, for example ethanol or a mixture of acetone : water in the ratio of 80 to 70 : 20 - 30.

Example 1. In a reactor with a volume of 3.5 liters, load 785 g of toluene and 2.12 kg of a mixture of soda and water at 4N concentration of sodium carbonate (volume ratio of toluene : a mixture of baking soda and water 1:3). The oxidation is carried out at a temperature of 240oC and the pressure is of DNA phase 2260 g, the organic phase 660, the Organic phase is returned to the process, and water doukissa for 6 minutes at a temperature of 240oC and a pressure of 8.0 MPa and air flow rate of 1000 nl/h, the reactor is unloaded, the solution evaporated. Obtain 180 g of dry residue containing sodium benzoate and soda.

The dry residue is placed in a vertical type reactor "Soxhlet" 2.0 liter working under a carbon dioxide pressure of 5.2 MPa. The height of the layer of the loaded balance 45 see from Above into the reactor serves acetone containing 10% water, at a rate of 0.5 l/h.

The process is carried out for 60 minutes at a temperature 50-53oC and continuous supply of water and acetone. At the end of the process is unloaded from the reactor 66 g of sodium, containing only traces of sodium benzoate, and 0.6 l of a solution of benzoic acid in acetone. After evaporation of the acetone allocate 150 g of benzoic acid, the purity of which 99.9% of the output from theoretical 98,7%.

The example illustrated by diagram (see drawing), where 1 - reactor; 2, 3 - evaporator; 4 - separator.

Example 2. Getting benzoic acid is carried out analogously to example 1, however, if the selection:

The carbon dioxide pressure of 5.2 MPa

Temperature - 50-53oC

The feed rate of the solvent (water:acetone 3:7) - 0.5 l/h

The pressure of carbon dioxide - 5.0 MPa

Temperature - 50oC

The feed rate of the solvent (water:ethanol 2:8) - 0.5 l/h

The reaction time 60 min

The degree of purity of 99.1%

Output benzoic acid 97.5% of

Example 4. Getting benzoic acid is carried out analogously to example 1, however, if the selection:

The carbon dioxide pressure of 5.2 MPa

Temperature - 55oC

The feed rate of the solvent (water:ethyl ketone 1:9) - 0.5 l/h

The reaction time 60 min

The degree of purity - 99.8% of

The output of benzoic acid - 98.6% of

In the case of obtaining sodium benzoate.

Example 5. One stripped off oxidat obtained as in example 1 (0.6 kg), placed in a column with a height of 1 m, diameter 60 mm Above the pump serves ethanol at a speed of 2.5 l/h for 4 hours. Bottom of receiver selects a solution of sodium benzoate in alcohol. Distilled alcohol, receive 451 sodium benzoate (96,6%).

Example 6. Analogously to example 5 at 25oC 550 g one stripped off of oxidate, feeding water methyl ethyl ketone (10%) of water at a feed rate of 2.5 l/h for 5 hours, obtained after distillation of methyl ethyl ketone 432 g sodium benzoate (94,4%).

Literature

1. USSR author's certificate N 24936 elsto USSR N 1369226, class. C 07 C 63/06, 1983 (prototype).

The way to obtain benzoic acid or sodium benzoate by oxidation of toluene with oxygen at a temperature of 240-275oC and a pressure of 7.5 to 15.0 MPa in the presence of water and sodium carbonate at 2-6 normal concentration of the latter in the aqueous phase and the volume ratio of toluene:a mixture of sodium carbonate and water 1-5:5-1 within 5-30 min with obtaining organic and aqueous phases, the additional oxidation of the obtained aqueous phase for 1-6 min and the release of her benzoic acid or sodium benzoate, characterized in that the separation of benzoic acid by evaporation cookislands the aqueous phase and the processing of the obtained residue in a vertical apparatus operating under pressure of the carbon dioxide feed water solvent (10-30% water), capable of dissolving benzoic acid and does not dissolve the soda and unloading of the target product from the bottom at a temperature below the boiling point of the solvent, and the allocation of sodium benzoate is carried out by treating the dried oxalate solvent, dissolving sodium benzoate and not dissolving soda, for example, ethanol, aqueous ethyl ketone.

 

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