A kind of processing method of paraben

Abstract

The invention relates to a method for processing parabens, which includes a salt-forming dehydration process of obtaining potassium phenolate by reacting phenol and potassium hydroxide; a carboxylation process of obtaining dipotassium p-hydroxybenzoate by reacting potassium phenolate and carbon dioxide; an acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate and sulfuric acid; a recovery process of obtaining a water absorbent by potassium sulfate and activated carbon; and an esterification process of obtaining parabens by using p-hydroxybenzoic acid, an alcohol compound, sulfuric acid and a water absorbent. The present invention recovers the potassium sulfate produced in the processing process and prepares the water absorbent, which can reduce the amount of sulfuric acid used and avoid serious corrosion of equipment due to high concentration of sulfuric acid in the reaction system, and can also synergize with sulfuric acid to accelerate the esterification reaction and improve the yield of parabens.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, in particular to a processing method of paraben. Background Art

[0002] Parabens are internationally recognized broad-spectrum and highly effective food preservatives. The United States, Europe, Japan, Canada, South Korea, Russia and other countries allow the use of parabens in food. They are widely used in condiments such as soy sauce and vinegar, pickled products, baked goods, sauce products, beverages, rice wine, and fruit and vegetable preservation. China's GB2760 stipulates that ethyl paraben, propyl paraben, methyl paraben sodium, ethyl paraben sodium, and propyl paraben sodium salt can be used as food preservatives.

[0003] At present, the common production method of paraben is to first synthesize p-hydroxybenzoic acid, and then use sulfuric acid as a catalyst to reflux esterify p-hydroxybenzoic acid and alcohol compounds at a certain temperature. This method has a low yield, a long reaction time, and many side reactions. In order to increase the catalytic rate of the reaction, the concentration of sulfuric acid in the reaction system is high, which seriously corrodes the equipment and pollutes the environment. In recent years, the literature has successively reported preparation methods such as solid superacids, heteropolyacids, rare earth compounds, microwave irradiation, ferrous sulfate, solid chloride FeCl3 as catalysts, and calcium oxide as a dehydrating agent. The preparation process of the solid heteropolyacid catalytic method is relatively expensive; although the microwave irradiation catalytic method can shorten the reaction time, it requires special experimental equipment; the calcium oxide dehydration method also has the disadvantage of low yield, etc., which needs to be improved. Summary of the invention

[0004] The problem to be solved by the present invention is to provide a processing method of paraben ester in view of the above-mentioned deficiencies existing in the prior art, which has the advantage of improving the yield of paraben ester.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] A method for processing parabens comprises: a salt-forming dehydration process of obtaining potassium phenolate by reacting phenol and potassium hydroxide; a carboxylation process of obtaining dipotassium p-hydroxybenzoate by reacting potassium phenolate and carbon dioxide; an acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate and sulfuric acid; a recovery process of obtaining a water absorbent by potassium sulfate and activated carbon; and an esterification process of obtaining parabens by using p-hydroxybenzoic acid, an alcohol compound, sulfuric acid and a water absorbent.

[0007] By adopting the above technical scheme, potassium sulfate, a by-product in the production process of p-hydroxybenzoic acid, is recovered and prepared into a water absorbent. After potassium sulfate is attached to the activated carbon base, it has good water absorption performance, can promote the water in the esterification process to continuously leave the esterification reaction system, and promote the formation of parabens; at the same time, the water absorbent can synergize with sulfuric acid to accelerate the esterification reaction; in summary, by recovering potassium sulfate produced in the processing process and preparing it into a water absorbent, it can reduce the amount of sulfuric acid used, avoid the high concentration of sulfuric acid in the reaction system and serious corrosion to the equipment, and can synergize with sulfuric acid to accelerate the esterification reaction and improve the yield of parabens.

[0008] Furthermore, the salt-forming and dehydration process includes first heating potassium hydroxide and phenol to 100±5°C, keeping the temperature for reaction for more than 30 minutes until the content of free alkali in the reaction solution is 0.3~1.2%, then heating to 140±5°C, reducing the reaction pressure to 10.0~11.0 kPa, evaporating and dehydrating for 30~60 minutes, then heating to 200±10°C, and simultaneously increasing the reaction pressure to 2.5~3.0 kPa, and completing the dehydration to obtain a potassium phenolate solution containing potassium phenolate.

[0009] Preferably, the carboxylation reaction process comprises first heating the potassium phenolate solution to 220-230° C., introducing carbon dioxide into the potassium phenolate solution, controlling the reaction pressure at 0.4-0.6 MPa, reacting for 4.0-5.0 hours, then cooling to 200±10° C., continuing the reaction for 25-35 minutes, and then vacuum evaporating the reaction solution to remove phenol, and then dissolving the remaining reaction solution in water, decolorizing with activated carbon and filtering to obtain a carboxylated solution containing dipotassium p-hydroxybenzoate.

[0010] Preferably, the acid precipitation process comprises firstly adding 30%wt sulfuric acid to the carboxylation liquid, controlling the dropping temperature to 65-75°C, until the pH of the reaction liquid drops to 1-2, then filtering, centrifuging, and washing in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then steam drying and pulverizing the precipitate to obtain the p-hydroxybenzoic acid.

[0011] Furthermore, the esterification process includes first adding p-hydroxybenzoic acid, sulfuric acid and a water absorbent to the alcohol compound in sequence, then heating to 70-120°C, reflux esterification reaction for 4-6 hours, and then evaporating the reaction solution at normal pressure to remove the alcohol compound to obtain an esterified solution containing paraben.

[0012] Preferably, the esterification process further comprises: first adding the esterification liquid into water, and then dripping 4% sodium carbonate solution until the pH of the esterification liquid is 6.0-8.5, and then cooling and centrifuging and dehydrating the liquid, removing the supernatant, and obtaining a crude paraben.

[0013] Preferably, the esterification process further comprises, firstly, adding activated carbon and crude paraben to the alcohol compound in sequence, heating to 90-110°C, decolorizing for 25-35 minutes, and then evaporating and concentrating, controlling the evaporating and concentrating temperature to 70-90°C, removing the alcohol compound, and then cooling, crystallizing, centrifuging and deliquoring, and drying the material, controlling the drying temperature to 80-105°C, and the drying time to 3.5-5.0 hours, to obtain the paraben.

[0014] Preferably, the processing method also includes recovering the waste activated carbon after decolorization treatment in the carboxylation process and the esterification process, and then subjecting the waste activated carbon to flash drying, activation and multi-stage cooling separation treatment to obtain activated carbon; the activated carbon is used in the carboxylation process, the recovery process and the esterification process respectively.

[0015] Furthermore, the recovery process includes first subjecting the activated carbon to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm, and simultaneously adding potassium hydroxide to a potassium sulfate aqueous solution until the pH is 6.5-8.5, and then sequentially adding the nano-activated carbon and a multifunctional auxiliary agent, performing ultrasonic and freeze-drying treatments, and then adjusting the pH to 5.5-6.5 with sulfuric acid to obtain a water absorbent.

[0016] Preferably, the ultrasonic treatment power is 810-830 W, the ultrasonic time is 10-12 min, and the ultrasonic temperature is 47±3° C.

[0017] In summary, the beneficial technical effect of the present invention is that by recovering the potassium sulfate produced in the processing process and preparing it into a water absorbent, it can not only reduce the amount of sulfuric acid used, avoid the high concentration of sulfuric acid in the reaction system and serious corrosion to the equipment, but also synergize with sulfuric acid to accelerate the esterification reaction and increase the yield of parabens. DETAILED DESCRIPTION

[0018] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0019] Embodiment 1: A method for processing paraben disclosed in the present invention, comprising:

[0020]

[0021] The invention relates to a salt-forming and dehydrating process of obtaining potassium phenolate by reacting phenol and potassium hydroxide; a carboxylation process of obtaining dipotassium p-hydroxybenzoate by reacting potassium phenolate and carbon dioxide; an acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate and sulfuric acid; a recovery process of obtaining a water absorbent by using potassium sulfate and activated carbon; and an esterification process of obtaining paraben by using p-hydroxybenzoic acid, an alcohol compound, sulfuric acid and a water absorbent.

[0022] Wherein, the alcohol compound is methanol, ethanol, propanol, butanol or isobutanol.

[0023] Example 2: A method for processing paraben disclosed in the present invention, which is different from Example 1 in that:

[0024] S1 The salt-forming and dehydration process of potassium phenolate obtained by the reaction of phenol and potassium hydroxide

[0025] First, potassium hydroxide and phenol are put into a carboxylation reaction kettle, and the temperature is raised to 100±5°C at normal pressure, and the reaction solution is stirred for more than 30 minutes until the content of free alkali in the reaction solution is 0.8%; then the temperature is raised to 140±5°C at normal pressure, and then the reaction pressure is reduced to 10.6kPa, and the reaction solution is evaporated and dehydrated for 48 minutes; then the temperature is raised to 200±10°C, and the reaction pressure is simultaneously raised to 2.76kPa, and the dehydration is completed to obtain a potassium phenolate solution containing potassium phenolate;

[0026] S2 Carboxylation process of potassium phenolate and carbon dioxide to obtain dipotassium p-hydroxybenzoate

[0027] First, the potassium phenolate solution of S1 is further heated to 225°C, and carbon dioxide (which is stored in a buffer tank after gasification and dehydration) is introduced into the carboxylation reactor to control the reaction pressure at 0.5MPa and react for 4.5 hours; then the temperature is lowered to 200±10°C, and the reaction is continued to be stirred for 30 minutes, and the reaction is completed; then the reactor is vacuumed, and the phenol in the reaction solution is evaporated into gas and then condensed and recovered by a condenser to obtain recovered phenol; then the remaining reaction solution is transferred to a decolorization kettle, dissolved in water, decolorized with activated carbon, and filtered to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate;

[0028] S3 is the acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate with sulfuric acid

[0029] First, the carboxylated liquid of S2 is transferred to an acid precipitation reactor, and then 30%wt of sulfuric acid is added dropwise to the carboxylated liquid, and the dropping temperature is controlled to be 70°C until the pH of the reaction liquid is reduced to 1, and then filtered, centrifuged, and washed with water in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then the precipitate is steam-dried and pulverized to obtain p-hydroxybenzoic acid;

[0030] S4 Recovery process of water absorbent made from potassium sulfate and activated carbon

[0031] First, the activated carbon is subjected to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm. At the same time, potassium hydroxide is added to the potassium sulfate aqueous solution until the pH is 7.0, and then the nano-activated carbon and the multifunctional auxiliary agent are added in sequence for ultrasonic and freeze-drying treatment. The ultrasonic treatment power is 820 W, the ultrasonic time is 11 min, and the ultrasonic temperature is 47±3°C. Then, sulfuric acid is used to adjust the pH to 6.0 to obtain a water absorbent.

[0032] S5 Esterification process of parabens from p-hydroxybenzoic acid, alcohol compounds, sulfuric acid and water absorbent

[0033] S51 esterification reaction: firstly, methanol is put into the esterification reaction kettle, and then the p-hydroxybenzoic acid, sulfuric acid and water absorbent of S3 are put into the reaction kettle in sequence under stirring, and then the temperature is raised to 100°C at normal pressure, and the reaction is kept at this temperature for 9 hours; during the reaction, the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline to be condensed, and then flows back into the esterification reaction kettle; after the reaction is finished, the pipeline between the condenser outlet and the esterification reaction kettle is controlled to be closed, and the pipeline between the condenser outlet and the alcohol metering tank is opened, and the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline to be condensed, and then flows back into the alcohol metering tank; after the recovery of the alcohol compound is finished, an esterification liquid containing paraben is obtained;

[0034] S52 crude preparation: first add water to the neutralization kettle, then add the esterification liquid under stirring conditions, and then dropwise add 4% sodium carbonate solution until the pH of the esterification liquid is 6.5-7.5, then cool and centrifuge to dehydrate, remove the supernatant, and obtain a crude paraben;

[0035] S53 refining: first add methanol to the decolorization kettle, and then add activated carbon and crude paraben in sequence under stirring conditions, heat to 100°C at normal pressure, stir and decolorize for 30 minutes to obtain a decolorized material; then transfer the decolorized material to a concentration kettle, stir and heat to 80°C, and the alcohol compound vapor on the top of the concentration kettle enters the condenser through a pipeline for condensation and refluxes into the alcohol metering tank; after the alcohol compound recovery is completed, cool, crystallize, centrifuge to remove the liquid, and dry, control the drying temperature to 90°C, and the drying time to 7.0h to obtain paraben, with a yield of 92%.

[0036] Example 3: A method for processing parabens disclosed in the present invention, which is different from Example 1 in that:

[0037] S1 The salt-forming and dehydration process of potassium phenolate obtained by the reaction of phenol and potassium hydroxide

[0038] First, potassium hydroxide and phenol are put into a carboxylation reaction kettle, and the temperature is raised to 100±5°C at normal pressure, and the reaction solution is stirred for more than 30 minutes until the content of free alkali in the reaction solution is 0.3%; then the temperature is raised to 140±5°C at normal pressure, and then the reaction pressure is reduced to 11.0 kPa, and the reaction solution is evaporated and dehydrated for 30 minutes; then the temperature is raised to 200±10°C, and the reaction pressure is simultaneously raised to 2.50 Pa, and the dehydration is completed to obtain a potassium phenolate solution containing potassium phenolate;

[0039] S2 Carboxylation process of potassium phenolate and carbon dioxide to obtain dipotassium p-hydroxybenzoate

[0040] First, the potassium phenolate solution of S1 is further heated to 225°C, and carbon dioxide (which is stored in a buffer tank after gasification and dehydration) is introduced into the carboxylation reactor to control the reaction pressure at 0.4MPa and react for 4.0h; then the temperature is lowered to 200±10°C, and the reaction is continued with stirring for 30min, and the reaction is completed; then the reactor is vacuumed, and the phenol in the reaction solution is evaporated into gas and then condensed and recovered by a condenser to obtain recovered phenol; then the remaining reaction solution is transferred to a decolorization reactor, dissolved in water, decolorized with activated carbon, and filtered to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate;

[0041] S3 is the acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate with sulfuric acid

[0042] First, the carboxylated liquid of S2 is transferred to an acid precipitation reactor, and then 30%wt of sulfuric acid is added dropwise to the carboxylated liquid, and the dropping temperature is controlled to be 65°C until the pH of the reaction liquid is reduced to 1, and then filtered, centrifuged, and washed with water in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then the precipitate is steam-dried and crushed to obtain p-hydroxybenzoic acid;

[0043] S4 Recovery process of water absorbent made from potassium sulfate and activated carbon

[0044] First, the activated carbon is subjected to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm. At the same time, potassium hydroxide is added to the potassium sulfate aqueous solution until the pH is 6.5, and then the nano-activated carbon and the multifunctional auxiliary agent are added in sequence, and ultrasonic and freeze-drying treatments are carried out. The ultrasonic treatment power is 810 W, the ultrasonic time is 10 min, and the ultrasonic temperature is 47±3°C. Then, sulfuric acid is used to adjust the pH to 5.5 to obtain a water absorbent.

[0045] S5 Esterification process of parabens from p-hydroxybenzoic acid, alcohol compounds, sulfuric acid and water absorbent

[0046] S51 esterification reaction: firstly put ethanol into the esterification reaction kettle, then put the p-hydroxybenzoic acid and sulfuric acid of S3 and the water absorbent of S4 in sequence under stirring condition, then heat to 120°C at normal pressure, and keep warm for reaction for 4 hours; during the reaction, the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the esterification reaction kettle; after the reaction is finished, the pipeline between the condenser outlet and the esterification reaction kettle is controlled to be closed, and the pipeline between the condenser outlet and the alcohol metering tank is opened, and the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the alcohol metering tank; after the recovery of the alcohol compound is finished, an esterification liquid containing paraben is obtained;

[0047] S52 crude preparation: first add water to the neutralization kettle, then add the esterification liquid under stirring conditions, and then dropwise add 4% sodium carbonate solution until the pH of the esterification liquid is 6.0-8.5, then cool and centrifuge to dehydrate, remove the supernatant, and obtain a crude paraben;

[0048] S53 refining: first add ethanol to the decolorization kettle, and then add activated carbon and crude paraben in sequence under stirring conditions, heat to 110°C at normal pressure, stir and decolorize for 25 minutes to obtain a decolorized material; then transfer the decolorized material to a concentration kettle, stir and heat to 80°C, and the alcohol compound vapor on the top of the concentration kettle enters the condenser through a pipeline for condensation and refluxes into the alcohol metering tank; after the alcohol compound recovery is completed, cool, crystallize, centrifuge to remove the liquid, and dry, control the drying temperature to 100°C, and the drying time to 3.5h to obtain paraben, with a yield of 95%.

[0049] Example 4: A method for processing paraben disclosed in the present invention, which is different from Example 1 in that:

[0050] S1 The salt-forming and dehydration process of potassium phenolate obtained by the reaction of phenol and potassium hydroxide

[0051] First, potassium hydroxide and phenol are put into a carboxylation reaction kettle, and the temperature is raised to 100±5°C at normal pressure, and the reaction solution is stirred for more than 30 minutes until the content of free alkali in the reaction solution is 0.5%; then the temperature is raised to 140±5°C at normal pressure, and then the reaction pressure is reduced to 10.0 kPa, and the reaction solution is evaporated and dehydrated for 40 minutes; then the temperature is raised to 200±10°C, and the reaction pressure is simultaneously raised to 3.00 kPa, and the dehydration is completed to obtain a potassium phenolate solution containing potassium phenolate;

[0052] S2 Carboxylation process of potassium phenolate and carbon dioxide to obtain dipotassium p-hydroxybenzoate

[0053] First, the potassium phenolate solution of S1 is further heated to 225°C, and carbon dioxide (which is stored in a buffer tank after gasification and dehydration) is introduced into the carboxylation reactor to control the reaction pressure at 0.5MPa and react for 5.0h; then the temperature is lowered to 200±10°C, and the reaction is continued with stirring for 25min, and the reaction is completed; then the reactor is vacuumed, and the phenol in the reaction solution is evaporated into gas and then condensed and recovered by a condenser to obtain recovered phenol; then the remaining reaction solution is transferred to a decolorization reactor, dissolved in water, decolorized with activated carbon, and filtered to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate;

[0054] S3 is the acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate with sulfuric acid

[0055] First, the carboxylated liquid of S2 is transferred to an acid precipitation reactor, and then 30%wt of sulfuric acid is added dropwise to the carboxylated liquid, and the dropping temperature is controlled to be 70°C until the pH of the reaction liquid is reduced to 1, and then filtered, centrifuged, and washed with water in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then the precipitate is steam-dried and pulverized to obtain p-hydroxybenzoic acid;

[0056] S4 Recovery process of water absorbent made from potassium sulfate and activated carbon

[0057] First, the activated carbon is subjected to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm. At the same time, potassium hydroxide is added to the potassium sulfate aqueous solution until the pH is 8.5, and then the nano-activated carbon and the multifunctional auxiliary agent are added in sequence for ultrasonic and freeze-drying treatment. The ultrasonic treatment power is 813 W, the ultrasonic time is 11 min, and the ultrasonic temperature is 47±3°C. Then, sulfuric acid is used to adjust the pH to 6.0 to obtain a water absorbent.

[0058] S5 Esterification process of parabens from p-hydroxybenzoic acid, alcohol compounds, sulfuric acid and water absorbent

[0059] S51 esterification reaction: firstly put propanol into the esterification reaction kettle, then put the p-hydroxybenzoic acid, sulfuric acid and water absorbent of S3 and S4 in order under stirring condition, then heat to 110°C at normal pressure, and keep warm for reaction for 5h; during the reaction, the vapor of alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the esterification reaction kettle; after the reaction is finished, the pipeline between the condenser outlet and the esterification reaction kettle is controlled to be closed, and the pipeline between the condenser outlet and the alcohol metering tank is opened, and the vapor of alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the alcohol metering tank; after the recovery of alcohol compound is finished, the esterification liquid containing paraben is obtained;

[0060] S52 crude preparation: first add water to the neutralization kettle, then add the esterification liquid under stirring, then add 4% sodium carbonate solution dropwise until the pH of the esterification liquid is 6.5-7.0, then cool and centrifuge to remove water, remove the supernatant, and obtain the crude paraben;

[0061] S53 refining: first add propanol to the decolorization kettle, and then add activated carbon and crude paraben in sequence under stirring conditions, heat to 100°C at normal pressure, stir and decolorize for 30 minutes to obtain a decolorized material; then transfer the decolorized material to a concentration kettle, stir and heat to 70°C, and the alcohol compound vapor on the top of the concentration kettle enters the condenser through a pipeline for condensation and refluxes into the alcohol metering tank; after the alcohol compound recovery is completed, cool, crystallize, centrifuge to remove the liquid, and dry, control the drying temperature to 105°C, and the drying time to 5.0h to obtain paraben with a yield of 88%.

[0062] Example 5: A method for processing paraben disclosed in the present invention, which is different from Example 1 in that:

[0063] S1 The salt-forming and dehydration process of potassium phenolate obtained by the reaction of phenol and potassium hydroxide

[0064] First, potassium hydroxide and phenol are put into a carboxylation reaction kettle, and the temperature is raised to 100±5°C at normal pressure, and the reaction solution is stirred for more than 30 minutes until the content of free alkali in the reaction solution is 1.0%; then the temperature is raised to 140±5°C at normal pressure, and then the reaction pressure is reduced to 10.6kPa, and the reaction solution is evaporated and dehydrated for 50 minutes; then the temperature is raised to 200±10°C, and the reaction pressure is simultaneously raised to 2.76kPa, and the dehydration is completed to obtain a potassium phenolate solution containing potassium phenolate;

[0065] S2 Carboxylation process of potassium phenolate and carbon dioxide to obtain dipotassium p-hydroxybenzoate

[0066] First, the potassium phenolate solution of S1 is further heated to 220°C, and carbon dioxide (which is stored in a buffer tank after gasification and dehydration) is introduced into the carboxylation reactor to control the reaction pressure at 0.6MPa and react for 4.0h; then the temperature is lowered to 200±10°C, and the reaction is continued with stirring for 30min, and the reaction is completed; then the reactor is vacuumed, and the phenol in the reaction solution is evaporated into gas and then condensed and recovered by a condenser to obtain recovered phenol; then the remaining reaction solution is transferred to a decolorization reactor, dissolved in water, decolorized with activated carbon, and filtered to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate;

[0067] S3 is the acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate with sulfuric acid

[0068] First, the carboxylated liquid of S2 is transferred to an acid precipitation reactor, and then 30%wt sulfuric acid is added dropwise to the carboxylated liquid, and the dropping temperature is controlled to be 70°C until the pH of the reaction liquid is reduced to 2, and then filtered, centrifuged, and washed with water in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then the precipitate is steam-dried and crushed to obtain p-hydroxybenzoic acid;

[0069] S4 Recovery process of water absorbent made from potassium sulfate and activated carbon

[0070] First, the activated carbon is subjected to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm. At the same time, potassium hydroxide is added to the potassium sulfate aqueous solution until the pH is 7.0, and then the nano-activated carbon and the multifunctional auxiliary agent are added in sequence for ultrasonic and freeze-drying treatment. The ultrasonic treatment power is 825 W, the ultrasonic time is 10 min, and the ultrasonic temperature is 47±3°C. Then, sulfuric acid is used to adjust the pH to 6.0 to obtain a water absorbent.

[0071] S5 Esterification process of parabens from p-hydroxybenzoic acid, alcohol compounds, sulfuric acid and water absorbent

[0072] S51 esterification reaction: firstly put butanol into the esterification reaction kettle, then put the p-hydroxybenzoic acid, sulfuric acid and water absorbent of S3 and S4 in order under stirring condition, then heat to 90°C at normal pressure, and keep warm for reaction for 5h; during the reaction, the vapor of alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the esterification reaction kettle; after the reaction is finished, the pipeline between the condenser outlet and the esterification reaction kettle is controlled to be closed, and the pipeline between the condenser outlet and the alcohol metering tank is opened, and the vapor of alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and refluxes into the alcohol metering tank; after the recovery of alcohol compound is finished, the esterification liquid containing paraben is obtained;

[0073] S52 crude preparation: first add water to the neutralization kettle, then add the esterification liquid under stirring conditions, and then dropwise add 4% sodium carbonate solution until the pH of the esterification liquid is 6.5-7.5, then cool and centrifuge to dehydrate, remove the supernatant, and obtain a crude paraben;

[0074] S53 refining: first add butanol to the decolorization kettle, and then add activated carbon and crude paraben in sequence under stirring conditions, heat to 90°C at normal pressure, stir and decolorize for 35 minutes to obtain a decolorized material; then transfer the decolorized material to a concentration kettle, stir and heat to 90°C, and the alcohol compound vapor on the top of the concentration kettle enters the condenser through a pipeline for condensation and refluxes into the alcohol metering tank; after the alcohol compound recovery is completed, cool, crystallize, centrifuge to remove the liquid, and dry, control the drying temperature to 80°C, and the drying time to 4.0h to obtain paraben, with a yield of 85%.

[0075] Example 6: A method for processing paraben disclosed in the present invention, which is different from Example 1 in that:

[0076] S1 The salt-forming and dehydration process of potassium phenolate obtained by the reaction of phenol and potassium hydroxide

[0077] First, potassium hydroxide and phenol are put into a carboxylation reaction kettle, and the temperature is raised to 100±5°C at normal pressure, and the reaction solution is stirred for more than 30 minutes until the content of free alkali in the reaction solution is 1.2%; then the temperature is raised to 140±5°C at normal pressure, and then the reaction pressure is reduced to 10.6kPa, and the reaction solution is evaporated and dehydrated for 60 minutes; then the temperature is raised to 200±10°C, and the reaction pressure is simultaneously raised to 2.76kPa, and the dehydration is completed to obtain a potassium phenolate solution containing potassium phenolate;

[0078] S2 Carboxylation process of potassium phenolate and carbon dioxide to obtain dipotassium p-hydroxybenzoate

[0079] First, the potassium phenolate solution of S1 is further heated to 230°C, and carbon dioxide (which is stored in a buffer tank after gasification and dehydration) is introduced into the carboxylation reactor to control the reaction pressure at 0.5MPa and react for 5.0h; then the temperature is lowered to 200±10°C, and the reaction is continued with stirring for 35min, and the reaction is completed; then the reactor is vacuumed, and the phenol in the reaction solution is evaporated into gas and then condensed and recovered by a condenser to obtain recovered phenol; then the remaining reaction solution is transferred to a decolorization reactor, dissolved in water, decolorized with activated carbon, and filtered to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate;

[0080] S3 is the acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate with sulfuric acid

[0081] First, the carboxylated liquid of S2 is transferred to an acid precipitation reactor, and then 30%wt sulfuric acid is added dropwise to the carboxylated liquid, and the dropping temperature is controlled to be 75°C until the pH of the reaction liquid is reduced to 2, and then filtered, centrifuged, and washed with water in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then the precipitate is steam-dried and crushed to obtain p-hydroxybenzoic acid;

[0082] S4 Recovery process of water absorbent made from potassium sulfate and activated carbon

[0083] First, the activated carbon is subjected to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm. At the same time, potassium hydroxide is added to the potassium sulfate aqueous solution until the pH is 6.5, and then the nano-activated carbon and the multifunctional auxiliary agent are added in sequence, and ultrasonic and freeze-drying treatments are carried out. The ultrasonic treatment power is 830 W, the ultrasonic time is 12 min, and the ultrasonic temperature is 47±3°C. Then, sulfuric acid is used to adjust the pH to 6.5 to obtain a water absorbent.

[0084] S5 Esterification process of parabens from p-hydroxybenzoic acid, alcohol compounds, sulfuric acid and water absorbent

[0085] S51 esterification reaction: firstly, isobutyl alcohol is put into the esterification reaction kettle, and then, under stirring conditions, p-hydroxybenzoic acid, sulfuric acid and water absorbent of S3 are put into the reaction kettle in sequence, and then the temperature is raised to 70°C at normal pressure, and the reaction is kept at this temperature for 6 hours; during the reaction, the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and then flows back into the esterification reaction kettle; after the reaction is completed, the pipeline between the condenser outlet and the esterification reaction kettle is controlled to be closed, and the pipeline between the condenser outlet and the alcohol metering tank is opened, and the vapor of the alcohol compound at the top of the esterification reaction kettle enters the condenser through the pipeline for condensation, and then flows back into the alcohol metering tank; after the recovery of the alcohol compound is completed, an esterification liquid containing paraben is obtained;

[0086] S52 crude preparation: first add water to the neutralization kettle, then add the esterification liquid under stirring conditions, and then dropwise add 4% sodium carbonate solution until the pH of the esterification liquid is 6.5-7.5, then cool and centrifuge to dehydrate, remove the supernatant, and obtain a crude paraben;

[0087] S53 refining: first add isobutanol into the decolorization kettle, then add activated carbon and crude paraben in sequence under stirring conditions, heat to 100°C at normal pressure, stir and decolorize for 30 minutes to obtain a decolorized material; then transfer the decolorized material to a concentration kettle, stir and heat to 80°C, the alcohol compound vapor on the top of the concentration kettle enters the condenser through a pipeline for condensation, and refluxes into the alcohol metering tank; after the alcohol compound recovery is completed, cool, crystallize, centrifuge to remove the liquid, and dry, control the drying temperature to 85°C, and the drying time to 4.0h to obtain paraben, with a yield of 98%.

[0088] Example 7: A processing method for paraben disclosed in the present invention is different from Example 1 in that activated carbon is required for decolorization in the carboxylation process and the esterification process. In order to improve the recycling of the waste activated carbon after decolorization, the present invention recovers the waste activated carbon and then subjects the waste activated carbon to flash drying, activation and multi-stage cooling separation treatment to obtain activated carbon. The obtained activated carbon is used in the carboxylation process, the recovery process and the esterification process respectively.

[0089] ⑴Feeding system

[0090] The waste activated carbon is conveyed by belt conveyor through bucket elevator into the storage hopper of the flash dryer. The transportation process is sealed and the feeding process is continuous.

[0091] ⑵Regeneration system

[0092] The regeneration system is mainly composed of a dryer and an activation furnace.

[0093] ① Flash drying treatment

[0094] The flash dryer is mainly heated by biomass combustion. The waste gas, water and materials generated by drying are separated by a cyclone separator, and the materials are sent to the activation furnace for activation. The waste gas and water are quenched and then treated by pulse bags + alkali spraying, and then discharged through a 15-meter high exhaust pipe. The dust collected by the pulse bags is sent to the activation furnace together with the materials for activation.

[0095] ②Activation treatment

[0096] Before using the activation furnace, the biomass furnace is first used to heat up. When the temperature rises to 750℃, the materials in the silo continue to enter the activation furnace for activation. The heat source is provided by the heat released during the activation process, and the biomass fuel is no longer used. In the activation furnace, the blower on one side blows the water vapor generated by the waste heat boiler into the furnace to provide the necessary oxygen and water vapor. Under the pull of the subsequent fan, the activated carbon flows from the furnace head to the furnace tail in a rotating state. At high temperature, carbon reacts with oxygen in the air, releasing a large amount of heat, and reacts with water vapor at the same time, absorbing part of the heat. The temperature in the furnace is about 900-1000℃. The activated flue gas carries the regenerated activated carbon into the waste heat system. During the activation process, the amount of oxygen charged must be strictly controlled to ensure the stability of the temperature while preventing excessive loss of activated carbon.

[0097] During the activation process, some reactions occur on the surface of activated carbon:

[0098] C+O2→CO2+Q (exothermic)

[0099] C+H2O→CO+ H2-Q (endothermic)

[0100] C+O2→CO2+Q (exothermic)

[0101] H2+O2→H2O+Q (exothermic)

[0102] The occurrence of these chemical reactions not only gasifies the carbon atoms on the surface of the activated carbon's pores, expanding the pores and forming new active surfaces, but also releases a large amount of combustible gas in the process. These combustible gases react with the oxygen introduced to release a large amount of heat energy as a heat source to maintain the furnace temperature. The adsorbed substances are carbonized, activated or burned at high temperatures to complete the regeneration process.

[0103] ⑶ Waste heat utilization

[0104] The waste heat boiler recovers the waste heat of the activation furnace to prepare water vapor. The water vapor is mainly supplied to the activation furnace. If there is any excess, it will be sent to the employee bathhouse for employees to wash.

[0105] ⑷Multi-stage cooling and separation treatment

[0106] The flue gas carrying the regenerated activated carbon enters the primary quenching system for quenching, and then enters the primary cyclone separator for collection. The principle is to use the centrifugal force to cause the dust particles to rotate and fall along the cylinder wall to separate the solid and gas. The separated heavier materials are cooled and mixed by the screw conveyor, and then sent to the silo by the induced draft fan for packaging to obtain the finished powdered regenerated activated carbon; the flue gas carries a small amount of lighter materials into the secondary quenching system for quenching, and then enters the pulse bag dust collector for collection, and is sent to the silo for packaging to obtain the finished powdered regenerated activated carbon. The flue gas is treated with alkali solution and then discharged through a 15-meter-high exhaust pipe.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for processing parabens, characterized in that: The method comprises a salt-forming dehydration process of obtaining potassium phenolate by reacting phenol and potassium hydroxide; a carboxylation process of obtaining dipotassium p-hydroxybenzoate by reacting potassium phenolate and carbon dioxide; an acid precipitation process of obtaining p-hydroxybenzoic acid and potassium sulfate by reacting dipotassium p-hydroxybenzoate and sulfuric acid; a recovery process of obtaining a water absorbent by using potassium sulfate and activated carbon; and an esterification process of obtaining paraben by using p-hydroxybenzoic acid, an alcohol compound, sulfuric acid and a water absorbent. The salt-forming and dehydrating process comprises: firstly heating potassium hydroxide and phenol to 100±5°C, keeping the temperature to react for more than 30 minutes, until the content of free alkali in the reaction solution is 0.3-1.2%, then heating to 140±5°C, reducing the reaction pressure to 10.0-11.0 kPa, evaporating and dehydrating for 30-60 minutes, then heating to 200±10°C, and simultaneously increasing the reaction pressure to 2.5-3.0 kPa, and completing the dehydration to obtain potassium phenolate solution containing potassium phenolate; The carboxylation reaction process comprises: firstly heating the potassium phenolate solution to 220-230° C., introducing carbon dioxide into the potassium phenolate solution, controlling the reaction pressure at 0.4-0.6 MPa, reacting for 4.0-5.0 hours, then cooling to 200±10° C., continuing the reaction for 25-35 minutes, and then vacuum evaporating the reaction solution to remove phenol, and then dissolving the remaining reaction solution with water, decolorizing with activated carbon, and filtering to obtain a carboxylation solution containing dipotassium p-hydroxybenzoate; The acid precipitation process comprises the following steps: firstly, adding 30%wt sulfuric acid to the carboxylation solution, controlling the adding temperature to be 65-75°C, until the pH value of the reaction solution is reduced to 1-2, then filtering, centrifuging, and washing in sequence to obtain a potassium sulfate aqueous solution and a precipitate containing p-hydroxybenzoic acid, and then steam drying and pulverizing the precipitate to obtain the p-hydroxybenzoic acid; The esterification process comprises firstly adding p-hydroxybenzoic acid, sulfuric acid and a water absorbent to an alcohol compound in sequence, then heating to 70-120° C., performing esterification reflux reaction for 4-6 hours, and then performing atmospheric evaporation treatment on the reaction liquid to remove the alcohol compound, thereby obtaining an esterified liquid containing paraben; The esterification process further comprises: firstly adding the esterification liquid into water, and then dropping a 4% sodium carbonate solution until the pH of the esterification liquid is 6.0-8.5, and then cooling and centrifuging and dehydrating the solution, and removing the supernatant to obtain a crude paraben; The esterification process further comprises: firstly adding activated carbon and crude paraben to the alcohol compound in sequence, heating to 90-110° C., decolorizing for 25-35 min, and then evaporating and concentrating at a temperature of 70-90° C. to remove the alcohol compound, and then cooling, crystallizing, centrifuging and deliquating, and drying the material at a temperature of 80-105° C. and a drying time of 3.5-5.0 h to obtain the paraben; The processing method also includes recovering the waste activated carbon after decolorization in the carboxylation process and the esterification process, and then subjecting the waste activated carbon to flash drying, activation and multi-stage cooling separation to obtain activated carbon; the activated carbon is used in the carboxylation process, the recovery process and the esterification process respectively; The recovery process includes firstly subjecting the activated carbon to high-pressure superheated steam pulverization treatment to obtain nano-activated carbon of 200-500 nm, and simultaneously adding potassium hydroxide to a potassium sulfate aqueous solution until the pH value is 6.5-8.5, and then sequentially adding the nano-activated carbon and a multifunctional auxiliary agent, and subjecting the mixture to ultrasonic and freeze-drying treatments, and then adjusting the pH value to 5.5-6.5 with sulfuric acid to obtain a water absorbent; The power of the ultrasonic treatment is 810-830 W, the ultrasonic time is 10-12 min, and the ultrasonic temperature is 47±3° C.

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