Recycling method and application of waste liquid

Abstract

The invention relates to a waste liquid recycling method and application, and discloses a preparation method for producing sodium salicylate by using waste liquid, and the preparation method specifically comprises the following steps: introducing carbon dioxide into the waste liquid containing sodium phenate and sodium hydroxide for the first time for reaction and layering to respectively obtain an oil phase and a water phase, the method comprises the following steps: reacting phenol with an alkaline reagent under normal pressure to obtain a reaction solution, then carrying out reduced pressure reaction on the reaction solution to obtain sodium phenate, and then introducing carbon dioxide for the second time to react to obtain sodium salicylate. According to the invention, the waste liquid containing sodium phenate and sodium hydroxide is subjected to chemical treatment, and sodium phenate in the waste liquid is used for producing high-purity sodium salicylate, so that an efficient reaction method for producing sodium salicylate under mild conditions is obtained, high-conversion-rate recovery and high-value utilization of the waste liquid are realized, no secondary pollution is caused during the process, and the method is suitable for industrial production. And the environment burden is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment agent utilization, and particularly relates to a method for recycling and application of waste liquid. Background Art

[0002] In the co-production process of propylene oxide and styrene (PO / SM), during the ethylbenzene / isopropylbenzene oxidation stage and the propylene epoxidation stage, over-oxidation to acid occurs, such as the oxidation of benzene ring-containing compounds to produce by-products such as phenol and benzoic acid, and the waste alkali liquor after alkali washing enters the wastewater. This waste alkali liquor has a high pH, a high COD concentration, and is difficult to biodegrade. Currently, for this waste alkali liquor, there are: (1) Incineration method: sending the waste alkali liquor into an incinerator for combustion to produce carbon dioxide and water; (2) Extraction method: selecting n-hexane, petroleum ether, etc. to extract the organic phase, and the remaining waste alkali is the aqueous phase for subsequent treatment; (3) Oxidative decomposition method: first adding sodium hypochlorite and hydrogen peroxide to oxidize highly toxic substances into low-toxic substances, and then treating or recovering them according to the method for treating inorganic waste liquor; (4) Evaporation and concentration: heating the waste alkali liquor to increase the salt concentration for subsequent treatment or recovery, such as the "triple-effect forced circulation evaporation + stripping" process reported currently, to reduce the COD value, etc. The above several methods have problems such as low process operation, high treatment cost, low material recovery rate and purity, and do not maximize the utilization value of this type of waste alkali liquor. Summary of the Invention

[0003] Based on this, it is necessary to provide a method for recycling and application of waste liquid that can have a high recovery rate and high utilization value.

[0004] In a first aspect, the present invention provides a method for recycling and application of waste liquid, comprising the following steps:

[0005] First, introduce carbon dioxide into the waste liquid containing sodium phenolate and sodium hydroxide for reaction, then separate the layers to obtain an oil phase and an aqueous phase respectively. The oil phase includes phenol. React the oil phase with a basic reagent to obtain a reaction solution containing sodium phenolate. After subjecting the reaction solution to vacuum drying, introduce carbon dioxide for reaction again to obtain sodium salicylate.

[0006] In some embodiments, by weight percentage, the mass percentage content of sodium phenolate in the waste liquid is 5 - 14%.

[0007] In some embodiments, by weight percentage, the mass percentage content of sodium hydroxide in the waste liquid is 0.1 - 0.3%.

[0008] In some embodiments, the waste liquid is selected from the waste liquid in the PO / SM co-production process; and / or, the composition of the waste liquid includes 1,2-propanediol, methanol, sodium hydroxide, sodium formate, sodium acetate, sodium benzoate, sodium phenolate and water.

[0009] In some embodiments, by weight percentage, the composition of the waste liquid includes: 1,2 - propylene glycol 1 - 1.5%, methanol 0.05 - 0.2%, sodium hydroxide 0.1 - 0.3%, sodium formate 3 - 5%, sodium acetate 0.1 - 0.4%, sodium benzoate 12 - 17%, sodium phenoxide 5 - 14%, and water 62 - 78%.

[0010] In some embodiments, the method for recycling the waste liquid further satisfies at least one of the following (1) to (10):

[0011] (1) The mass ratio of the waste liquid to the first introduction of carbon dioxide is 1:(0.018 - 0.055);

[0012] (2) The basic reagent is selected from one or more of sodium hydroxide, sodium alkoxide, sodium carbonate, sodium oxide, and sodium peroxide;

[0013] (3) The mass ratio of the waste liquid to the basic reagent is 1:(0.02 - 0.047);

[0014] (4) The reaction temperature for the reaction of the oil phase with the basic reagent under normal pressure is 50°C - 80°C;

[0015] (5) The pressure for the vacuum drying is -0.04 MPa to -0.1 MPa;

[0016] (6) The temperature for the vacuum drying is 80°C - 115°C;

[0017] (7) The mass ratio of the waste liquid to the second introduction of carbon dioxide is 1:(0.02 - 0.053);

[0018] (8) The reaction temperature for the reaction of the second introduction of carbon dioxide is 135°C - 150°C;

[0019] (9) The reaction time for the reaction of the second introduction of carbon dioxide is 4 h - 5 h;

[0020] (10) The reaction pressure for the reaction of the second introduction of carbon dioxide is 0.7 MPa - 0.8 MPa.

[0021] In a second aspect, the present invention also provides a grinding aid, and the grinding aid contains the aqueous phase obtained by the method for recycling the waste liquid described above.

[0022] In some embodiments, the grinding aid is the material obtained by concentrating the aqueous phase.

[0023] In some embodiments, by mass percentage, the composition of the material includes: 1,2 - propanediol 1.5 - 2.3%, sodium formate 4.8 - 6.3%, sodium acetate 0.15 - 0.5%, sodium benzoate 17 - 24%, sodium bicarbonate 7.5 - 12.5% and water 58 - 62%.

[0024] In a third aspect, the present invention also provides a cement raw meal, and the composition of the cement raw meal includes the above-mentioned grinding aid; optionally, the composition of the cement raw meal includes 0.09% - 0.13% by weight of the above-mentioned grinding aid.

[0025] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0026] The present invention recycles and utilizes the waste liquid containing sodium phenolate and sodium hydroxide. By using a chemical treatment method, sodium salicylate with relatively high value is produced from the sodium phenolate in the waste liquid. It not only realizes the high-conversion recycling and high-value utilization of the waste liquid, but also obtains a high-purity sodium salicylate product. Compared with the waste liquid treatment processes such as incineration method, extraction method, oxidative decomposition method, evaporation and concentration, etc. adopted in the prior art, the present invention realizes the efficient utilization of resources, significantly reduces the COD value, has no secondary pollution during the process, and reduces the environmental burden; at the same time, it also realizes the efficient reaction for producing sodium salicylate under mild conditions, which provides new ideas and new methods for the resource utilization of waste alkali liquor in related fields. Detailed Embodiments

[0027] To facilitate the understanding of the present invention, the following provides a more comprehensive description of the technical solution of the present invention with reference to the preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] It should be noted that the experimental methods without specific conditions mentioned in the following embodiments of the present invention are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. All kinds of commonly used chemical reagents used in the embodiments are commercially available products.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0030] Industrially, the co-oxidation method is often used to produce propylene oxide (PO) and styrene (SM) simultaneously. During the operation of the co-production process, a large amount of wastewater from the PO / SM co-production process is generated. Due to its high pH, it is also called the waste alkali liquor from the PO / SM co-production process. The waste alkali liquor from the PO / SM co-production process also has the characteristics of high COD and difficult biodegradation, and it is difficult to treat with conventional biochemical processes. Therefore, there is an urgent need to develop a treatment method for the waste alkali liquor from the PO / SM co-production process that can be well recovered and utilized.

[0031] The composition of the waste alkali liquor from the PO / SM co-production process contains a relatively high proportion of sodium phenoxide. Therefore, how to recover and utilize the sodium phenoxide in the waste alkali liquor from the PO / SM co-production process can improve the efficient recovery and utilization of the waste alkali liquor from the PO / SM co-production process.

[0032] In a first aspect, the present invention provides a method for the recovery and utilization of waste liquid, comprising the following steps:

[0033] First, carbon dioxide is introduced into the waste liquid containing sodium phenoxide and sodium hydroxide for reaction, and then it is stratified to obtain an oil phase and an aqueous phase respectively. The oil phase is phenol. The oil phase is reacted with a basic reagent to obtain a reaction solution containing sodium phenoxide. After the reaction solution is dried under reduced pressure, carbon dioxide is introduced for a second reaction to obtain sodium salicylate.

[0034] The present invention utilizes the principle that sodium phenoxide reacts with CO2 while the other substances do not react, and pre-separates the sodium phenoxide in the waste liquid. The treatment process involves reduction reaction, acid-base neutralization and carboxylation reaction, and finally sodium salicylate with high yield and high purity is prepared. The reaction mechanism involved is as follows:

[0035] C6H5ONa (sodium phenoxide) + CO2 + H2O = C6H5OH (phenol) + NaHCO3.

[0036] C6H5OH (phenol) + NaOH = C6H5ONa (sodium phenoxide) + H2O.

[0037] C6H5ONa (sodium phenoxide) + CO2 = C6H4(ONa)COOH (sodium salicylate).

[0038] The present invention realizes the efficient recovery and high-value utilization of sodium phenoxide in the waste liquid, realizes the efficient utilization of waste liquid resources, has no secondary pollution during the period, and reduces the environmental burden.

[0039] In some embodiments, the mass percentage content of sodium phenoxide in the waste liquid is 5-14%, including but not limited to 5%, 6%, 8%, 10%, 12%, 14% or any content range formed by any two of the foregoing and any mass percentage content within the range.

[0040] In some embodiments, the mass percentage of sodium hydroxide in the waste liquid is 0.1 - 0.3%, including but not limited to 0.1%, 0.15%, 0.2%, 0.25%, 0.3% or any content range formed by any two of the foregoing and any mass percentage within the range.

[0041] In some embodiments, the waste liquid is selected from the waste liquid in the PO / SM co-production process.

[0042] In some embodiments, the composition of the waste liquid includes 1,2-propanediol, methanol, sodium hydroxide, sodium formate, sodium acetate, sodium benzoate, sodium phenolate and water.

[0043] In some embodiments, by weight percentage, the composition of the waste liquid includes: 1,2-propanediol 1 - 1.5%, methanol 0.05 - 0.2%, sodium hydroxide 0.1 - 0.3%, sodium formate 3 - 5%, sodium acetate 0.1 - 0.4%, sodium benzoate 12 - 17%, sodium phenolate 5 - 14% and water 62 - 78%.

[0044] In some embodiments, the mass ratio of the waste liquid to the first introduction of carbon dioxide is 1:(0.018 - 0.055), including but not limited to 1:0.02, 1:0.03, 1:0.04, 1:0.05 or any mass ratio range formed by any two of the foregoing and any mass ratio within the range.

[0045] In some embodiments, the basic reagent is selected from one or more of sodium hydroxide, sodium alkoxide, sodium carbonate, sodium oxide and sodium peroxide; further, the use of sodium hydroxide in the present invention can better achieve the technical effects of the present invention.

[0046] In some embodiments, the mass ratio of the waste liquid to the basic reagent is 1:(0.02 - 0.047), including but not limited to 1:0.02, 1:0.03, 1:0.04, 1:0.045 or any mass ratio range formed by any two of the foregoing and any mass ratio within the range.

[0047] In some embodiments, the reaction temperature of the oil phase reacting with the basic reagent is 50°C - 80°C, including but not limited to 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any reaction temperature range formed by any two of the foregoing and any reaction temperature within the range.

[0048] In some embodiments, the pressure of the vacuum drying is -0.04 MPa to -0.1 MPa, including but not limited to -0.04 MPa, -0.05 MPa, -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, -0.1 MPa or any pressure range formed by any two of the foregoing and any pressure within the range.

[0049] In some embodiments, the temperature of the reduced-pressure drying is 80°C - 115°C, including but not limited to 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or the temperature ranges formed by any two of the foregoing and any temperature within the ranges.

[0050] In some embodiments, the mass concentration of the alkaline reagent is 30wt% - 50wt%, including but not limited to 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, 45wt%, 50wt%, or the mass concentration ranges formed by any two of the foregoing and any mass concentration within the ranges; further, using an alkaline reagent with a mass concentration of 40wt% can better achieve the effects of the present invention.

[0051] In some embodiments, the mass ratio of the waste liquid to the second introduction of carbon dioxide is 1:(0.02 - 0.053), including but not limited to 1:0.02, 1:0.03, 1:0.04, 1:0.05, or the mass ratio ranges formed by any two of the foregoing and any mass ratio within the ranges.

[0052] In some embodiments, the temperature of the reaction of the second introduction of carbon dioxide is 135°C - 150°C, including but not limited to 135°C, 138°C, 140°C, 142°C, 145°C, 148°C, 150°C, or the temperature ranges formed by any two of the foregoing and any temperature within the ranges.

[0053] In some embodiments, the reaction time of the reaction of the second introduction of carbon dioxide is 4h - 5h, including but not limited to 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5h, or the reaction time ranges formed by any two of the foregoing and any reaction time within the ranges.

[0054] In some embodiments, the reaction pressure of the reaction of the second introduction of carbon dioxide is 0.7MPa - 0.8MPa, including but not limited to 0.7MPa, 0.71MPa, 0.72MPa, 0.73MPa, 0.74MPa, 0.75MPa, 0.76MPa, 0.77MPa, 0.78MPa, 0.79MPa, 0.8MPa, or the reaction pressure ranges formed by any two of the foregoing and any reaction pressure within the ranges.

[0055] In some embodiments, after the reaction of the second introduction of carbon dioxide is completed, the pH is adjusted to 7.5 - 8.5 to ensure the stability of the sodium salicylate product.

[0056] Second aspect, the present invention also provides a grinding aid, which comprises the aqueous phase obtained by the recycling method of the above-mentioned waste liquid, specifically including:

[0057] First, carbon dioxide is introduced into the waste liquid containing sodium phenolate and sodium hydroxide for reaction, and after stratification, an oil phase and an aqueous phase are respectively obtained.

[0058] After the waste alkali liquor from the PO / SM co-production process is recycled by the present invention, a mixed liquid can be obtained for use as a grinding aid. In particular, the aqueous phase mixed liquid prepared by reacting the wastewater in the PO / SM co-production process containing sodium phenolate and sodium hydroxide with carbon dioxide can better improve the grinding performance.

[0059] In some embodiments, the composition of the aqueous phase includes: methanol, 1,2-propanediol, sodium formate, sodium acetate, sodium benzoate, sodium bicarbonate and water.

[0060] The organic acid salts such as sodium benzoate and sodium formate in the aqueous phase of the present invention have a surface-active effect, reduce the surface energy of the material particles, change the charge and polarity of the particle surface, and avoid particle agglomeration. Sodium bicarbonate may generate CO2 gas during the grinding process, and these gases will form micro-bubbles inside the particles, changing the internal structure of the particles and improving the grinding effect. There is a hydroxyl group in the 1,2-propanediol organic matter, which can form hydrogen bonds with the oxides and hydroxides on the surface of cement particles and is more easily destroyed during the grinding process. The two work synergistically and have a better effect; at the same time, the two alcohols have a certain lubricity, reduce the friction between the grinding medium and the particles, reduce the grinding energy consumption, and improve the efficiency.

[0061] In some embodiments, by mass percentage, the composition of the aqueous phase includes: methanol 0.08 - 0.27%, 1,2-propanediol 1 - 1.6%, sodium formate 3 - 5.5%, sodium acetate 0.15 - 0.35%, sodium benzoate 12.5 - 19%, sodium bicarbonate 4.6 - 11.2%, and the balance is water.

[0062] In some embodiments, the grinding aid is the material after the aqueous phase is concentrated.

[0063] In some embodiments, the composition of the material includes: 1,2-propanediol, sodium formate, sodium acetate, sodium benzoate, sodium bicarbonate and water.

[0064] In some embodiments, by mass percentage, the composition of the material includes: 1,2-propanediol 1.5 - 2.3%, sodium formate 4.8 - 6.3%, sodium acetate 0.15 - 0.5%, sodium benzoate 17 - 24%, sodium bicarbonate 7.5 - 12.5% and water 58 - 62%.

[0065] Thirdly, the present invention also provides a cement raw meal, and the composition of the cement raw meal includes the grinding aid described above.

[0066] In some embodiments, the weight addition amount of the grinding aid in the cement raw meal is 0.09% - 0.13%, including but not limited to 0.09%, 0.1%, 0.11%, 0.12%, 0.13% or the weight addition amount ranges formed by any two of the foregoing and any weight addition amount within the ranges.

[0067] For the experimental parameters not specified in the following specific embodiments, the guidelines given in the present application document shall be preferentially referred to. It is also possible to refer to the experimental manuals in the art or other experimental methods known in the art, or the experimental conditions recommended by the manufacturers.

[0068] The raw materials and reagents involved in the following specific embodiments can be obtained commercially, or those skilled in the art can prepare them according to known means.

[0069] The waste alkali liquor used in the examples and comparative examples of the present invention is the waste alkali liquor in the PO / SM co-production process. By weight percentage, the composition of the waste alkali liquor in the PO / SM co-production process is as follows:

[0070] 1,2 - propanediol 1 - 1.5%, methanol 0.05 - 0.2%, sodium hydroxide 0.1 - 0.3%, sodium formate 3 - 5%, sodium acetate 0.1 - 0.4%, sodium benzoate 12 - 17%, sodium phenoxide 5 - 14% and water 62 - 78%.

[0071] Example 1, Method for Recycling Waste Liquid

[0072] The waste alkali liquor used in the examples of the present invention is the waste alkali liquor in the PO / SM co-production process. By weight percentage, the composition of the waste alkali liquor in the PO / SM co-production process is as follows:

[0073] 1,2 - propanediol 1%, methanol 0.08%, sodium hydroxide 0.14%, sodium formate 3.8%, sodium acetate 0.2%, sodium benzoate 13.5%, sodium phenoxide 5.7% and water 75.58%.

[0074] Weigh 500 g of waste alkali liquor and place it in a three - necked flask. Start stirring and slowly introduce CO2 until no new turbidity appears in the solution. Take a sample for testing. When the reaction is complete, a total of 11.8 g of CO2 is introduced, so that the reaction between sodium phenoxide and sodium hydroxide in the waste alkali liquor is complete. Transfer it to a separating funnel and let it stand for separation. The lower aqueous phase is an aqueous solution mixed with sodium salts and alcohols, and the solid content is [not given in the original]. The upper layer is the oil - phase phenol;

[0075] The separated aqueous phase composition by mass percentage is as follows: 1,2 - propanediol 1.04%, methanol 0.1%, sodium formate 3.99%, sodium acetate 0.28%, sodium benzoate 15.02%, sodium bicarbonate 4.99% and water 74.58%. The aqueous phase is concentrated at atmospheric pressure to a solid content of about 40% for the grinding aid test.

[0076] Transfer 25.1 g of the separated phenol to a three - necked beaker, heat it up to 55 °C, and add an aqueous sodium hydroxide solution with a mass concentration of 40% under stirring. The mass of sodium hydroxide in the aqueous sodium hydroxide solution is 10.7 g. After reacting for 40 min, a reaction solution is obtained. The reaction solution is placed under a vacuum of - 0.06 MPa, and the temperature is raised to 85 °C for vacuum drying to obtain 29.85 g of relatively dry sodium phenoxide.

[0077] Slowly introduce 11.5 g of CO₂ into the above - mentioned sodium phenoxide. When the pressure rises to 0.7 MPa, stop introducing gas, raise the temperature to 135 °C, and react for 4 h. Then add an aqueous sodium hydroxide solution with a mass concentration of 40% to adjust the pH of the system to 7.5. After the system temperature drops to room temperature, it is successively filtered, concentrated, cooled and crystallized to obtain 30.08 g of crude sodium salicylate.

[0078] The crude sodium salicylate is washed 3 times with absolute ethanol and dried in vacuum at 60 °C for 6 h with a vacuum degree of - 0.08 MPa. Finally, 27.05 g of sodium salicylate product with a purity of 99.1% is obtained. The actual conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process used in this example is 65.7%.

[0079] Example 2. Method for recycling waste liquid

[0080] In the examples of the present invention, the waste alkali liquor used is the waste alkali liquor of the PO / SM co - production process. By mass percentage, the composition of the waste alkali liquor of the PO / SM co - production process is as follows:

[0081] 1,2 - propanediol 1.3%, methanol 0.11%, sodium hydroxide 0.2%, sodium formate 3.2%, sodium acetate 0.25%, sodium benzoate 14.8%, sodium phenoxide 7.89% and water 72.25%.

[0082] Weigh 500 g of the waste alkali liquor and place it in a three - necked flask. Start stirring and slowly introduce CO₂ until no new turbidity appears in the solution. Take a sample for testing and the reaction is complete. Finally, a total of 16.2 g of CO₂ is introduced, making the reaction between sodium phenoxide and sodium hydroxide in the waste alkali liquor complete. Transfer it to a separating funnel and let it stand for separation. The lower aqueous phase is a mixed aqueous solution of sodium salts and alcohols, and the upper layer is the oil - phase phenol;

[0083] The composition of the separated aqueous phase by mass percentage is as follows: 1,2 - propanediol 1.36%, methanol 0.12%, sodium formate 3.31%, sodium acetate 0.27%, sodium benzoate 15.34%, sodium bicarbonate 6.35% and water 73.25%. The aqueous phase is concentrated at atmospheric pressure to a solid content of about 40% for the grinding aid test.

[0084] Transfer 39.38 g of the separated phenol to a three - necked beaker, heat it to 70 °C, and add an aqueous sodium hydroxide solution with a mass concentration of 40% under stirring. The mass of sodium hydroxide in the aqueous sodium hydroxide solution is 16.8 g. After reacting for 55 min, a reaction solution is obtained. The pressure of the reaction solution system is reduced to - 0.08 MPa, and the temperature is raised to 100 °C for vacuum drying to obtain 48.5 g of dry sodium phenoxide.

[0085] Slowly introduce 18.5 g of CO₂ into the above - mentioned dry sodium phenoxide. When the pressure rises to 0.8 MPa, stop introducing gas, raise the temperature to 140 °C, and react for 4.5 h. Then, adjust the pH of the system to 7.9 with an aqueous sodium hydroxide solution with a mass concentration of 40%. After the system temperature drops to room temperature, filter, concentrate, cool, and crystallize successively to obtain 45.89 g of crude sodium salicylate.

[0086] The crude sodium salicylate is washed 3 times with absolute ethanol and dried in vacuum at 60 °C for 8 h with a vacuum degree of - 0.08 MPa. Finally, 44.9 g of sodium salicylate product with a purity of 99% is obtained. The actual conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process used in this example is 67.12%.

[0087] Example 3. Method for recycling waste liquid

[0088] In the examples of the present invention, the waste alkali liquor used is the waste alkali liquor of the PO / SM co - production process. By mass percentage, the composition of the waste alkali liquor of the PO / SM co - production process is as follows:

[0089] 1,2 - propanediol 1.5%, methanol 0.18%, sodium hydroxide 0.29%, sodium formate 4%, sodium acetate 0.3%, sodium benzoate 12.6%, sodium phenoxide 10.6% and water 70.53%.

[0090] Weigh 500 g of the waste alkali liquor and place it in a three - necked flask. Start stirring and slowly introduce CO₂ until no new turbidity appears in the solution. Take a sample for testing and the reaction is complete. Finally, a total of 21.8 g of CO₂ is introduced, making the reaction between sodium phenoxide and sodium hydroxide in the waste alkali liquor complete. Transfer it to a separating funnel and let it stand for separation. The lower aqueous phase is a mixed aqueous solution of sodium salts and alcohols, and the upper layer is the oil - phase phenol.

[0091] The separated aqueous phase composition by mass percentage is as follows: 1,2 - propanediol 1.57%, methanol 0.19%, sodium formate 4.2%, sodium acetate 0.33%, sodium benzoate 13.16%, sodium bicarbonate 8.65% and water 71.9%. The aqueous phase is concentrated at atmospheric pressure to a solid content of about 40% for the grinding aid test.

[0092] Transfer 42.5 g of the separated phenol to a three - necked beaker, heat it up to 70 °C, and add an aqueous sodium hydroxide solution with a mass concentration of 40% under stirring. The mass of sodium hydroxide in the aqueous sodium hydroxide solution is 18.1 g. After reacting for 55 min, a reaction solution is obtained. The pressure of the reaction solution system is reduced to - 0.1 MPa, and the temperature is raised to 100 °C for vacuum drying to obtain 51.65 g of dry sodium phenoxide.

[0093] Slowly introduce 19.9 g of CO₂ into the above - mentioned dry sodium phenoxide. When the pressure rises to 0.8 MPa, stop introducing gas, raise the temperature to 140 °C, and react for 5 h. Then add an aqueous sodium hydroxide solution with a mass concentration of 40% to adjust the pH of the system to 7.8. After the system temperature drops to room temperature, it is successively filtered, concentrated, cooled and crystallized to obtain 51.47 g of crude sodium salicylate.

[0094] The crude sodium salicylate is washed 3 times with absolute ethanol and dried in vacuum at 80 °C for 6 h with a vacuum degree of - 0.08 MPa, and finally 50.06 g of sodium salicylate product with a purity of 99.2% is obtained. The actual conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process used in this example is 70.28%.

[0095] Example 4. Method for recycling waste liquid

[0096] The waste alkali liquor used in the examples of the present invention is the waste alkali liquor of the PO / SM co - production process. By mass percentage, the composition of the waste alkali liquor of the PO / SM co - production process is as follows:

[0097] 1,2 - propanediol 1.3%, methanol 0.2%, sodium hydroxide 0.2%, sodium formate 5%, sodium acetate 0.1%, sodium benzoate 16.7%, sodium phenoxide 13.2% and water 63.3%.

[0098] Weigh 500 g of the waste alkali liquor and place it in a three - necked flask. Start stirring and slowly introduce CO₂ until no new turbidity appears in the solution. Take a sample for testing and the reaction is complete. Finally, a total of 26.5 g of CO₂ is introduced, making the reaction between sodium phenoxide and sodium hydroxide in the waste alkali liquor complete; transfer it to a separating funnel and let it stand for separation. The lower aqueous phase is a mixed aqueous solution of sodium salts and alcohols, and the upper layer is the oil - phase phenol;

[0099] The separated aqueous phase composition by mass percentage is as follows: 1,2 - propanediol 1.41%, methanol 0.25%, sodium formate 5.32%, sodium acetate 0.16%, sodium benzoate 18.34%, sodium bicarbonate 10.95% and water 63.57%. The aqueous phase is concentrated at atmospheric pressure to a solid content of about 40% for the grinding aid test.

[0100] Transfer 53.4 g of the separated phenol to a three - necked beaker, heat it to 70 °C, and add an aqueous sodium hydroxide solution with a mass concentration of 40% under stirring. The mass of sodium hydroxide in the aqueous sodium hydroxide solution is 22.85 g. After reacting for 55 min, a reaction solution is obtained. The reaction solution system is depressurized to - 0.1 MPa, and the temperature is raised to 100 °C for vacuum drying to obtain 65.4 g of dry sodium phenoxide.

[0101] Slowly introduce 25 g of CO₂ into the above - mentioned dry sodium phenoxide. When the pressure rises to 0.8 MPa, stop introducing gas, raise the temperature to 144.5 °C, react for 5 h, then add an aqueous sodium hydroxide solution with a mass concentration of 40% to adjust the pH of the system to 8.2. After the system temperature drops to room temperature, filter, concentrate, cool and crystallize successively to obtain 70.01 g of crude sodium salicylate.

[0102] The crude sodium salicylate is washed 3 times with absolute ethanol and dried in vacuum at 80 °C for 6 h with a vacuum degree of - 0.08 MPa, and finally 68.52 g of sodium salicylate product with a purity of 99.3% is obtained. The actual conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process used in this example is 75.96%.

[0103] Example 5

[0104] The difference from Example 1 is that after slowly introducing CO₂ into the dry sodium phenoxide and stopping the introduction of gas, the reaction temperature is raised to 125 °C and reacted for 5 h, and the remaining steps are the same as those in Example 1.

[0105] Finally, 22.82 g of sodium salicylate product with a purity of 99.0% is obtained in this example. The conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process in this example is 55.45%.

[0106] Example 6

[0107] The difference from Example 1 is that after slowly introducing CO₂ into the dry sodium phenoxide and completing the reaction, the pH is adjusted to 9, and the remaining steps are the same as those in Example 1.

[0108] Finally, 20.02 g of sodium salicylate product with a purity of 99.0% is obtained in this example. The conversion rate of sodium phenoxide in the waste alkali liquor of the PO / SM co - production process in this example is 48.62%.

[0109] Application Example 1: Application of Grinding Aid in Cement

[0110] Since the content of the effective components in the aqueous phase was too low, the solid content was increased to about 40% by atmospheric pressure concentration, and then the grinding aid test was carried out.

[0111] The aqueous phase prepared in Example 1 was concentrated to a solid content of about 40% and then added as a grinding aid to the cement raw meal to test its application effect.

[0112] By mass percentage, the grinding aid composition is: 1,2 - propylene glycol 1.65%, sodium formate 6.29%, sodium acetate 0.4%, sodium benzoate 23.75%, sodium bicarbonate 7.89% and water 60.02%.

[0113] Cement raw meal: Using Jiangxi Wannianqing material, by mass percentage, the composition is: limestone 77.4%, sandstone 6.4%, shale 10.8%, yellow phosphorus slag 2% and non - ferrous metal ash slag 3.4%.

[0114] Grinding aids with dosages of 0.1wt% and 0.12wt% were added to the cement raw meal respectively, and the cement raw meal without adding grinding aid was used as the blank group. Cement raw meals with the same dosages of commercially available additive 1 (Huaxin grinding aid) and commercially available additive 2 (Aobaisite grinding aid) were used as the control groups. The grinding effects of the cement raw meals were tested respectively. The specific results are shown in Table 1 and Table 2:

[0115] Table 1: Grinding effect of cement raw meal with 0.1wt% grinding aid

[0116]

[0117] Table 2: Grinding effect of cement raw meal with 0.12wt% grinding aid

[0118]

[0119] Application Example 2: Application of Grinding Aid in Cement

[0120] The aqueous phase prepared in Example 2 was concentrated to a solid content of about 40% and added as a grinding aid to the cement raw meal to test its application effect.

[0121] By mass percentage, the grinding aid composition is: 1,2 - propylene glycol 2.03%, sodium formate 4.9%, sodium acetate 0.4%, sodium benzoate 22.87%, sodium bicarbonate 9.45% and water 60.35%.

[0122] Cement raw meal: Using Linxiang Conch material, by mass percentage, the composition is: limestone 90.93%, iron - containing 1.62%, silicon - containing 3.35% and aluminum - containing 4.10%.

[0123] Add a grinding aid with a dosage of 0.12 wt% to the cement raw meal, and use the cement raw meal without the grinding aid as the blank group. Use the cement raw meal with the same dosage of commercially available additive 1 (Huaxin additive) and commercially available additive 2 (Aobaisite grinding aid) as the control group, and test the grinding effect of the cement raw meal respectively. The specific results are shown in Table 3 as follows:

[0124] Table 3: Grinding effect of cement raw meal with 0.12 wt% grinding aid

[0125]

[0126] Application Example 3: Application of Grinding Aid in Cement

[0127] Concentrate the aqueous phase prepared in Example 3 to a solid content of about 40% and add it to the cement raw meal as a grinding aid to test its application effect.

[0128] By mass percentage, the grinding aid composition is: 1,2 - propanediol 2.23%, sodium formate 5.94%, sodium acetate 0.46%, sodium benzoate 18.69%, sodium bicarbonate 12.28% and water 60.4%.

[0129] Cement raw meal: Using Hubei Jinglan material, by mass percentage, the composition is: limestone 82.3%, phosphorus slag 5.5%, silica 4.5%, copper tailings 3.2% and coal - fired boiler slag 4.5%.

[0130] Add a grinding aid with a dosage of 0.12 wt% to the cement raw meal, and use the cement raw meal without the grinding aid as the blank group. Use the cement raw meal with the same dosage of commercially available additive 1 (Huaxin additive) and commercially available additive 2 (Aobaisite grinding aid) as the control group, and test the grinding effect of the cement raw meal respectively. The specific results are shown in Table 4 as follows:

[0131] Table 4: Grinding effect of cement raw meal with 0.12 wt% grinding aid

[0132]

[0133] Application Example 4: Application of Grinding Aid in Cement

[0134] Concentrate the aqueous phase prepared in Example 4 to a solid content of about 40% and add it to the cement raw meal as a grinding aid to test its application effect.

[0135] By mass percentage, the grinding aid composition is: 1,2 - propanediol 1.54%, sodium formate 5.81%, sodium acetate 0.17%, sodium benzoate 20.02%, sodium bicarbonate 11.95% and water 60.51%.

[0136] Cement raw meal: Using the raw materials from Yuande in Tibet, by mass percentage, the composition is: limestone 90%, iron powder 6%, and shale 4%.

[0137] Add 0.12 wt% of grinding aid to the cement raw meal, and use the cement raw meal without adding grinding aid as the blank group. Use the cement raw meal with the same dosage of commercially available additive 1 (Huaxin additive) and commercially available additive 2 (Aobaisite grinding aid) as the control group, and test the grinding effect of the cement raw meal respectively. The specific results are shown in Table 5:

[0138] Table 5: Grinding effect of cement raw meal with 0.12 wt% grinding aid

[0139]

[0140] In the present invention, the lower-layer aqueous-phase sodium salt and alcohol substances obtained after the recovery and utilization of the waste alkali liquor by the PO / SM co-production process can be directly used as grinding aids. When applied to cement raw meal, it can improve the grinding effect. From the results of Application Example 1 to Application Example 4 above, it can be seen that the grinding aid recovered in the present invention has a significant grinding effect when added to cement raw meal. Compared with commercially available grinding aids, the effect is also very prominent, and it is applicable to the grinding of raw meal with different ratios and in different regions. The present invention efficiently recovers and utilizes the waste alkali liquor of the PO / SM co-production process, saving resources.

[0141] Application Example 5

[0142] The difference between this comparative application example and Application Example 1 is that: the composition of the grinding aid does not contain sodium bicarbonate, and water is used to make up the mass, and the rest are the same as Application Example 1.

[0143] Application Example 6

[0144] The difference between this comparative application example and Application Example 1 is that: 1,2-propanediol in the composition of the grinding aid is replaced with an equal amount of 1,3-propanediol, and the rest are the same as Application Example 1.

[0145] Application Example 7

[0146] The difference between this comparative application example and Application Example 1 is that: the percentage content ratios of sodium formate, sodium acetate, and sodium benzoate in the composition of the grinding aid are different. Specifically, sodium formate is 3.5%, sodium acetate is 0.2%, and sodium benzoate is 17%. The insufficient amount is made up with water, and the rest are the same as Application Example 1.

[0147] The above Application Examples 5 to 7 are all freshly prepared grinding aids. Add them to the cement raw meal with a dosage of 0.12 wt%, and test the grinding effect of the cement raw meal. The results are shown in Table 6:

[0148] Table 6: Grinding effect of cement raw meal with 0.12 wt% grinding aid

[0149]

[0150] As can be seen from the results in Table 6, after the recovery and utilization of sodium phenolate and sodium hydroxide in the waste alkali liquor of the PO / SM co-production process in the present invention, substances such as the aqueous-phase sodium salt and alcohols can be directly used as grinding aids. When applied to cement raw meal, the grinding effect can be improved, and the aqueous phase has specific components, which can improve the grinding aid performance. However, the grinding performance of Application Examples Five to Seven is significantly worse than that of Application Example One. It can be seen that the aqueous phase after the process treatment of the waste alkali liquor of the PO / SM co-production process in the present invention is specific, and the technical solution of the present invention better realizes the recovery and high-value utilization of the waste alkali liquor of the PO / SM co-production process.

[0151] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0152] The above-described embodiments only represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for recycling waste liquid, characterized in that: The following steps are involved: Carbon dioxide is introduced into a waste liquid containing sodium phenolate and sodium hydroxide for a first reaction, and layers are separated to obtain an oil phase and an aqueous phase, respectively. The oil phase contains phenol, and the oil phase is reacted with an alkaline reagent to obtain a reaction solution containing sodium phenolate. After the reaction solution is dried under reduced pressure, carbon dioxide is introduced into the waste liquid for a second reaction to obtain sodium salicylate.

2. The method for recycling waste liquid according to claim 1, characterized in that: Calculated by weight percentage, the mass percentage of sodium phenolate in the waste liquid is 5-14%.

3. The method for recycling waste liquid according to claim 1, characterized in that: Calculated by weight percentage, the mass percentage of sodium hydroxide in the waste liquid is 0.1-0.3%.

4. The method for recycling waste liquid according to claim 1, characterized in that: The waste liquid is selected from the waste liquid in the PO / SM co-production process; and / or the waste liquid comprises 1,2-propylene glycol, methanol, sodium hydroxide, sodium formate, sodium acetate, sodium benzoate, sodium phenol and water.

5. The method for recycling waste liquid according to any one of claims 1 to 4, characterized in that: The waste liquid comprises, by important percentage, 1-1.5% 1,2-propylene glycol, 0.05-0.2% methanol, 0.1-0.3% sodium hydroxide, 3-5% sodium formate, 0.1-0.4% sodium acetate, 12-17% sodium benzoate, 5-14% sodium phenol and 62-78% water.

6. The method for recycling waste liquid according to claim 1, characterized in that: The waste liquid recycling method also satisfies at least one of the following (1) to (10): (1) The mass ratio of the waste liquid to the first carbon dioxide introduced is 1:(0.018-0.055); (2) The alkaline agent is selected from one or more of sodium hydroxide, sodium alkoxide, sodium carbonate, sodium oxide and sodium peroxide; (3) The mass ratio of the waste liquid to the alkaline reagent is 1:(0.02-0.047); (4) The reaction temperature of the oil phase and the alkaline reagent at normal pressure is 50°C-80°C; (5) The pressure of the reduced pressure drying is -0.04 MPa to -0.1 MPa; (6) The temperature of the reduced pressure drying is 80°C-115°C; (7) The mass ratio of the waste liquid to the second injection of carbon dioxide is 1:(0.02-0.053); (8) The reaction temperature of the second carbon dioxide introduction reaction is 135°C-150°C; (9) The reaction time of the second carbon dioxide introduction reaction is 4h-5h; (10) The reaction pressure of the second carbon dioxide introduction reaction is 0.7 MPa-0.8 MPa.

7. A grinding aid, characterized in that The grinding aid comprises the aqueous phase obtained by the waste liquid recycling method according to any one of claims 1 to 6.

8. The grinding aid according to claim 7, characterized in that The grinding aid is the material obtained by concentrating the aqueous phase.

9. The grinding aid according to claim 8, characterized in that Calculated by mass percentage, the material comprises: 1.5-2.3% of 1,2-propylene glycol, 4.8-6.3% of sodium formate, 0.15-0.5% of sodium acetate, 17-24% of sodium benzoate, 7.5-12.5% ​​of sodium bicarbonate and 58-62% of water.

10. A cement raw material, characterized in that: The composition of the cement raw meal includes the grinding aid described in any one of claims 7 to 9; optionally, the composition of the cement raw meal includes 0.09-0.13% by weight of the grinding aid described in any one of claims 7 to 9.

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