Method for synthesizing acrylate by recovering methanesulfonic acid from acrylic acid washing wastewater

Abstract

The invention relates to the field of fine chemical engineering wastewater treatment, and particularly discloses a method for synthesizing acrylic ester by recovering methanesulfonic acid from acrylic acid washing wastewater, which can turn the recovered methanesulfonic acid extracted from TMPTA washing wastewater into wealth, and in the preparation process, a mixed solvent in a certain proportion and a methanesulfonic acid solution with the concentration of 30% are extracted for four times, so that the yield of the acrylic ester is improved. The method improves the extraction rate of the acrylic acid, reduces the extraction loss rate of the methanesulfonic acid, greatly improves the content of the methanesulfonic acid, and removes the moisture in the 30% washing water concentrated solution under the condition of negative pressure of 75-80 DEG C, so that the content of the methanesulfonic acid is greater than or equal to 60%. Therefore, the esterification rate and the quality index of trimethylolpropane tri (methyl) acrylate synthesized by recycling methanesulfonic acid are guaranteed, the methanesulfonic acid recycled under the concentration can replace original fresh methanesulfonic acid with the content of 70%, waste is turned into wealth, meanwhile, the cost for synthesizing acrylate is saved, the purpose of saving the cost is achieved, and the method is suitable for industrial production. And the finished product accords with industrial indexes.

Description

Technical Field

[0001] The invention relates to the field of fine chemical wastewater treatment, and relates to a method for recovering methanesulfonic acid from acrylate washing wastewater to synthesize trimethylolpropane tri(meth)acrylate. Background Art

[0002] Trimethylolpropane tri(meth)acrylate is a very useful chemical product. Its good transparency, impact resistance, toughness, color durability, UV resistance and chemical stability make its emulsion copolymer the main dye adhesive widely used in the preparation of various coatings and adhesives for synthetic fiber cotton and some non-woven fabrics. Trimethylolpropane tri(meth)acrylate (TMPTA) is a very important acrylic multifunctional ester monomer. It can be used as a copolymer monomer to synthesize special acrylic resins and as a crosslinking agent for rubber and plastics. Due to its high double bond content, fast curing speed, low viscosity, high boiling point and low volatility, TMPTA has become the most widely used and largest amount of multifunctional acrylate active crosslinking diluent in the field of radiation curing.

[0003] Based on the environmental protection concept of waste utilization and turning waste into treasure, the present application selects crude methanesulfonic acid in TMPTA washing wastewater as the methanesulfonic acid in the process of synthesizing trimethylolpropane tri(meth)acrylate. However, when the crude methanesulfonic acid is directly used in the existing technology of synthesizing trimethylolpropane tri(meth)acrylate with the existing ratio, the esterification reaction time is too long, and the acidity is too high (≥5.5%), the dimerization and trimerization content is high, and the ester content is low. Therefore, it is urgent to design a new method for recovering methanesulfonic acid to synthesize acrylate to solve the above problems. Summary of the invention

[0004] The invention aims to provide a method for synthesizing acrylic acid ester by recovering methanesulfonic acid from acrylic acid washing wastewater, which can turn the recovered methanesulfonic acid into treasure. In the preparation process, a certain proportion of mixed solvent and a methanesulfonic acid solution with a concentration of 30% are extracted four times, thereby improving the extraction rate of acrylic acid, reducing the extraction loss rate of methanesulfonic acid, greatly improving the content of methanesulfonic acid, and removing water in 30% water washing water concentrate under a negative pressure of 75-80° C., so that the content of methanesulfonic acid is ≥60%, thereby ensuring the esterification rate and quality index of synthesizing trimethylolpropane tri(methyl)acrylate by recovering methanesulfonic acid. The methanesulfonic acid recovered at this concentration can replace the original fresh methanesulfonic acid with a content of 70%, and while turning waste into treasure, the cost of synthesizing acrylic acid is saved, thereby achieving the purpose of cost saving, and the finished product meets the industry index.

[0005] In order to solve the above technical problems, the present invention provides a method for recovering methanesulfonic acid from acrylic acid washing wastewater to synthesize acrylic acid ester, the method comprising the following steps:

[0006] S1. Put the acrylate washing wastewater and activated carbon into the reactor in sequence, stir at room temperature for 0.5h, and filter under negative pressure to obtain primary washing water;

[0007] S2, adding the primary washing water and the polymerization inhibitor into the reaction kettle, heating to 75-80°C and concentrating under negative pressure to obtain a 30% concentration of methanesulfonic acid solution, wherein the methanesulfonic acid content is ≥30%;

[0008] S3, after preparing a mixed solvent of octanol, cyclohexane and n-butanol, the mixed solvent and a 30% concentration of methanesulfonic acid solution are added into a reaction kettle in a certain proportion;

[0009] S4, the reactor is heated to 80°C and kept warm for 0.5h, and then left to stand in the extraction bottle for four extractions, and the methanesulfonic acid solution after the four extractions is sampled to measure the acidity and free monomers;

[0010] S5, concentrating the extracted methanesulfonic acid solution to 60% under negative pressure at 75-80° C., standing for crystallization, and filtering under normal pressure to obtain a reused methanesulfonic acid solution, wherein the methanesulfonic acid content is ≥60%;

[0011] S6. Using the recovered methanesulfonic acid as a catalyst, acrylic acid, trimethylolpropane, an azeotropic agent, an inhibitor, and a catalyst are sequentially put into a reactor to synthesize acrylate.

[0012] Preferably, the weight ratio of the acrylic acid ester washing wastewater to the activated carbon in S1 is 100% and 0.5-1% respectively; 100% here can be 1000g, that is, 1000g of acrylic acid ester washing wastewater and 5-10g of activated carbon.

[0013] Preferably, the weight ratio of the primary washing water to the polymerization inhibitor in S2 is 100% and 0.1-0.4‰, respectively, where 100% may be 1000g, i.e. 1000g of primary washing water and 0.1-0.4g of polymerization inhibitor.

[0014] Preferably, the weight ratio of the 30% methanesulfonic acid solution and the mixed solvent in S3 is 100% and 30%-35% respectively, where 100% may be 1000 g, i.e. 1000 g of 30% methanesulfonic acid solution and 300-350 g of mixed solvent.

[0015] Preferably, the weight ratio of the 30% concentration methanesulfonic acid solution to the mixed solvent in S3 is 3:1.

[0016] Preferably, the vacuum degree in S1 and S2 is controlled at 500-1000 Pa.

[0017] Preferably, the inhibitors in S2 and S6 are both a mixed system of hydroquinone and p-hydroxyanisole.

[0018] Preferably, the standing time in S4 is 0.5 h, and the crystallization temperature in S5 is controlled at 10-25° C.

[0019] Preferably, the azeotropic agent in S6 is one or both of cyclohexane and toluene.

[0020] Preferably, the catalyst in S6 further includes copper chloride, and the mass ratio of methanesulfonic acid recovered from the catalyst to copper chloride is 7:1.

[0021] The beneficial effects of the present invention are:

[0022] The invention can transform the recovered methyl sulfonic acid extracted from TMPTA washing waste water into treasure, and the recovered methyl sulfonic acid is used as a raw material to synthesize trimethylolpropane tri(methyl)acrylate, thereby improving the utilization rate of resources. In the preparation process, a certain proportion of mixed solvent and a 30% concentration methyl sulfonic acid solution are subjected to four extractions, thereby improving the extraction rate of acrylic acid, reducing the extraction loss rate of methyl sulfonic acid, and greatly improving the content of methyl sulfonic acid. Under the condition of negative pressure of 75-80 DEG C, the water in the 30% washing water concentrate is removed, so that the content of methyl sulfonic acid is greater than or equal to 60%, thereby ensuring the esterification rate and quality index of the synthesized trimethylolpropane tri(methyl)acrylate by the recovered methyl sulfonic acid. The methyl sulfonic acid recovered at the concentration can replace the original fresh 70% content methyl sulfonic acid, while transforming waste into treasure, saving the cost of synthesizing acrylate, and achieving the purpose of cost saving. The finished product is transparent and clear, free of impurities, and various indexes such as quality, water content, acid value, viscosity, etc. meet the industry indexes. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In a specific embodiment of the present invention, a method for recovering methanesulfonic acid from acrylic acid washing wastewater to synthesize acrylic acid ester comprises the following steps:

[0025] S1. 1000 g of acrylate washing wastewater and 10 g of activated carbon were put into a reactor in sequence, stirred at room temperature for 0.5 h, and filtered under a negative pressure of 850 Pa to obtain primary washing water;

[0026] S2, 5000g of primary washing water and 2g of polymerization inhibitor were sequentially added into a reaction kettle, heated to 75-80°C with stirring, concentrated under a negative pressure of 850pa to obtain a 30% methanesulfonic acid solution, and the methanesulfonic acid content was measured by sampling to be ≥30%;

[0027] S3, after octanol, cyclohexane and n-butanol are prepared into a mixed solvent, 700g of the mixed solvent and 2100g of 30% concentration of methanesulfonic acid solution are put into a reactor;

[0028] S4, the reactor was stirred and heated to 80°C and then kept warm for 0.5h, the reaction solution was allowed to stand in the extraction bottle for 0.5h, the above steps were repeated 3 times, and the methanesulfonic acid solution after four extractions was sampled to measure the acidity and free monomers to obtain 1800g of solution;

[0029] S5, 1800g of the extracted methanesulfonic acid solution was heated to 75-80°C, concentrated to 60% methanesulfonic acid solution under a negative pressure of 850pa, allowed to stand for 4h at 10-20°C for crystallization, and filtered at normal pressure to obtain 785g of recycled methanesulfonic acid solution, wherein the methanesulfonic acid content was ≥60%;

[0030] S6. Using the recovered methanesulfonic acid as a catalyst, acrylic acid, trimethylolpropane, an azeotropic agent, an inhibitor, and a catalyst are sequentially put into a reactor to synthesize acrylate.

[0031] Specifically, in the present embodiment, the inhibitors in step S2 and step S6 are both a mixed system of hydroquinone and p-hydroxyanisole.

[0032] Specifically, in this embodiment, the azeotropic agent S6 is one or two of cyclohexane and toluene.

[0033] Specifically, in this embodiment, the catalyst in S6 also includes copper chloride, and the mass ratio of methanesulfonic acid recovered from the catalyst to copper chloride is 7:1.

[0034] In this embodiment, three batches of parallel experiments were conducted to recover the full analytical indicators of methanesulfonic acid and the synthetic acrylates as follows:

[0035]

[0036]

[0037]

[0038] Note: The finished product gas phase analysis adopts the acrylate finished product detection method, -- represents the content is less than 0.01%.

[0039] In the above table, the recovered alcohol methyl sulfonic acid of three batches of parallel experiments is compared with Comparison 1. In Comparison 1, existing fresh methyl sulfonic acid with a content of 70% is used, wherein the acrylic acid content is 0%, while the content of the methyl sulfonic acid recovered by the present invention in this embodiment is between 62-63%, and the acrylic acid content of the recovered methyl sulfonic acid is only 2% different from that of Comparison 1, and the Cu content is 700-900ppm different. Moreover, the finished product is transparent and clear, free of impurities, and various indicators such as quality, moisture, acid value, viscosity, etc. all meet industry indicators, and can replace the original fresh methyl sulfonic acid with a content of 70%. While turning waste into treasure, the cost of synthesizing acrylate is greatly saved, thereby achieving the purpose of cost saving.

[0040] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for recovering methanesulfonic acid from acrylic acid washing wastewater to synthesize acrylic acid ester, characterized in that: The method comprises the following steps: S1. Put the acrylate washing wastewater and activated carbon into the reactor in sequence, stir at room temperature for 0.5h, and filter under negative pressure to obtain primary washing water; S2, adding the primary washing water and the polymerization inhibitor into the reaction kettle, heating to 75-80°C and concentrating under negative pressure to obtain a 30% concentration of methanesulfonic acid solution, wherein the methanesulfonic acid content is ≥30%; S3, after preparing a mixed solvent of octanol, cyclohexane and n-butanol, the mixed solvent and a 30% concentration of methanesulfonic acid solution are added into a reaction kettle in a certain proportion; S4, the reactor is heated to 80°C and kept warm for 0.5h, and then left to stand in an extraction bottle for a period of time and extracted four times, and the methanesulfonic acid solution after the four extractions is sampled to measure the acidity and free monomers; S5, concentrating the extracted methanesulfonic acid solution to 60% under negative pressure at 75-80° C., standing for crystallization, and filtering under normal pressure to obtain a recycled methanesulfonic acid solution, wherein the methanesulfonic acid content is ≥60%; S6. Using the recovered methanesulfonic acid as a catalyst, acrylic acid, trimethylolpropane, an azeotropic agent, an inhibitor, and a catalyst are sequentially put into a reactor to synthesize acrylate.

2. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The weight ratio of the acrylic acid ester washing wastewater and the activated carbon in the S1 is 100% and 0.5-1% respectively.

3. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The weight ratios of the primary washing water and the polymerization inhibitor in S2 are 100% and 0.1-0.4‰ respectively.

4. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The weight ratios of the 30% methanesulfonic acid solution and the mixed solvent in S3 are 100% and 30%-35% respectively.

5. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 4, characterized in that: The weight ratio of the 30% concentration methanesulfonic acid solution to the mixed solvent in S3 is 3:

1.

6. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The vacuum degree in S1 and S2 is controlled at 500-1000 Pa.

7. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The inhibitors in S2 and S6 are both a mixed system of hydroquinone and p-hydroxyanisole.

8. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The standing time in S4 is 0.5 h, and the crystallization temperature in S5 is controlled at 10-25° C.

9. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The azeotropic agent in S6 is one or both of cyclohexane and toluene.

10. The method for recovering methanesulfonic acid from acrylic acid washing wastewater according to claim 1, characterized in that: The catalyst in S6 also includes copper chloride.

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