A method for improving the selectivity of bisphenol A raw materials by bisphenol A isomers

Abstract

The present invention provides a method for synthesizing 4,4-bisphenol A from phenol and acetone. By regulating the equilibrium concentration of 2,4-bisphenol A in the reaction raw material system, preferably further regulating the mass ratio of phenol to acetone in the feed and the reaction temperature, the generation of total impurities can be inhibited, thereby improving the raw material selectivity, reducing the loads of the decomposition unit and the isomerization unit in the existing process, simplifying the process flow, and after the system operates stably, the decomposition unit can be cancelled to achieve the effect of zero tar emission.

Description

Technical Field

[0001] The present invention belongs to the technical field of epoxy resin synthesis, and particularly relates to an optimized process for the production process of bisphenol A type epoxy resin. Background Art

[0002] Bisphenol A (2,2'-bis(4-hydroxyphenyl)propane, also known as p,p-BPA or 4,4-BPA) is mainly used in the production of polycarbonate resin, epoxy resin, unsaturated polyester, polysulfone, polyetherimide, and polyarylate resin.

[0003] The main product 4,4-BPA is produced by the reaction of phenol and acetone. In this reaction, some by-products are also generated, such as the isomer 2,4-BPA of bisphenol A, and chroman, indane, tar, etc. The generation of these by-products not only reduces the selectivity of phenol (raw material utilization rate), but also affects the purity of the final bisphenol A product.

[0004]

[0005] Figure 4 The industrial production process of bisphenol A is briefly described. In the reaction unit, phenol in the raw material mother liquor (containing a large amount of phenol ~80%, a small amount of bisphenol A ~10%, and ~10% impurities such as isomer 2,4-BPA, chroman, indane, etc.) reacts with acetone, causing changes in the components of the mother liquor (such as in stream 1, phenol ~66%, bisphenol A ~23%, impurities ~11%). The contents of bisphenol A and impurities in the system both increase.

[0006] The impurities mentioned here include two types, namely reversible impurities (such as isomer 2,4-BPA, C3 phenol, etc.) and irreversible impurities (such as chroman, spiroindane, DMX, etc.). Specifically, they include:

[0007]

[0008] Stream 1 enters the crystallization unit, and part of the bisphenol A and phenol crystallize out of the mother liquor in the form of an adduct. The crystals are separated from the mother liquor containing impurities in the separation unit, and are purified and pelletized into products through streams 3 and 4 respectively. The mother liquor separated from the crystals, part of it is recycled back to the reaction unit as raw material through stream 5. In order to remove the impurities generated in the reaction and keep the impurity concentration in the system balanced, another part of the mother liquor is discharged out of the system in the form of tar after being processed by the decomposition unit through stream 8, and the phenol in the mother liquor returns to the reaction unit through logistics 9.

[0009] Since the impurities contain some reversible impurities such as 2,4-BPA and C3 phenol, etc., these substances can reversely generate bisphenol A under certain reaction conditions. Directly sending these substances to the decomposition unit for treatment will cause unnecessary waste. Therefore, the current mainstream practice is to add an isomerization unit before the decomposition unit, that is, part of the 2,4-BPA and other reversible impurities in stream 6 are converted into 4,4-BPA and recycled to the crystallization unit through stream 7 to achieve the purpose of increasing the yield. The impurities in the remaining mother liquor are then sent to the decomposition unit for treatment.

[0010] The above is the general process used in the current production of bisphenol A. In order to maintain the balance and stability of the impurity concentration in the system and prevent its accumulation, an isomerization unit and a decomposition unit are introduced into the system to remove the impurities generated in each reaction, that is, part of the reversible impurities are recycled and converted into bisphenol A products through the isomerization unit, and other impurities are discharged in the form of tar through the decomposition unit. From the above description, it can be seen that the decomposition unit is "necessary", and its existence can maintain the impurity concentration balance of the system and prevent the impurity concentration from rising and polluting the product and the catalyst. The role of the isomerization unit is "optimization", and its existence can recycle a part of the reversible impurities and reduce the tar discharge amount of the decomposition unit.

[0011] The equipment investment required for these two units is high. For example, the material selection of the decomposition unit device needs acid-resistant corrosion materials, and the high-temperature steam and vacuum systems required for the phenol evaporation and recovery modules of these two units all increase the production cost. And the discharged tar brings a burden to the subsequent environmental protection treatment. The fundamental reason for the existence of these two units is that the selectivity of the reaction unit is only 95-97%, and the reaction unit cannot avoid generating various reversible and irreversible impurities.

[0012] The industry still needs a better method for synthesizing bisphenol A, especially for reducing the generation of by-products. Summary of the Invention

[0013] The present invention discloses a method for synthesizing 4,4-bisphenol A by reacting phenol with acetone to obtain 4,4-bisphenol A, which is characterized in that: 2,4-bisphenol A is added to the reaction raw materials containing phenol and acetone to achieve the purpose of inhibiting the generation of impurities.

[0014] Furthermore, the concentration range of 2,4-bisphenol A in the reaction raw material system is controlled, and preferably the concentration range is controlled to be 2.0-4.0 wt%, preferably 3.0-4.0 wt% to achieve the purpose of inhibiting the generation of impurities.

[0015] The reaction raw materials can be fresh raw materials (i.e., only containing phenol and acetone), or a mixture of fresh raw materials and the recycled mother liquor after the reaction. The mother liquor after the reaction may already contain a part of 2,4-bisphenol A. Whether using fresh raw materials or a mixture of fresh raw materials and the mother liquor, by adjusting the dosage of 2,4-bisphenol A added or controlling the ratio of fresh raw materials to the mother liquor after the reaction, the concentration of 2,4-bisphenol A in the reaction raw material system is controlled to be 2.0 - 4.0 wt%, preferably 3.0 - 4.0 wt%.

[0016] The inventors unexpectedly found that by regulating the equilibrium concentration of 2,4-BPA in the reaction raw material system, the generation of total impurities (including various reversible and irreversible impurities) can be inhibited, thereby improving the raw material selectivity. Through a large number of experiments, the inventors found that controlling the concentration range of 2,4-BPA in the reaction raw material system to be 2.0 - 4.0 wt%, preferably 3.0% - 4.0 wt%, can achieve a good purpose of inhibiting the generation of impurities.

[0017] If the reaction raw material system contains more acetone or the reaction is carried out at a higher temperature, generally, it is necessary to appropriately increase the content of 2,4-BPA in the reaction raw material system. However, generally speaking, the content still needs to be controlled within 2 - 4 wt%, preferably 3 - 4 wt%.

[0018] The method further includes real-time monitoring of the content of 2,4-BPA in the feed of the reaction raw material system, and judging whether it is necessary to supplement exogenous 2,4-BPA according to its content. By real-time monitoring the 2,4-BPA value in the feed of the reaction raw material system and referring to the reaction operating conditions (such as temperature, mass ratio of phenol to acetone), when its value is lower than the set value, fresh 2,4-BPA must be supplemented to the system. If the concentration of 2,4-BPA is higher than the set value, no action is required or the content of 2,4-BPA in the reaction raw material system is controlled by adjusting the ratio with the fresh raw materials.

[0019] For the synthesis method as described above, wherein, the mass ratio of phenol to acetone in the reaction raw material system is (14 - 23):1, preferably (15 - 20):1. A preferably high mass ratio of phenol to acetone can further inhibit the generation of impurities.

[0020] For the synthesis method as described above, wherein, the reaction temperature is 70 - 86 °C, preferably between 70 and 80 °C. A preferably low reaction temperature can help inhibit the generation of total impurities in the system.

[0021] For the synthesis method as described above, the method is carried out under a catalytic system for bisphenol A commonly used in the art. The catalytic system includes but is not limited to: a mercapto-modified cation resin system, a system of cation resin and free mercapto substances.

[0022] Among them, the mercapto-modified cationic resin system includes, but is not limited to, cationic resins modified with mercaptoalkylamines such as 2-mercaptoethylamine, 3-mercaptopropylamine, N,N-dimethyl-3-mercaptopropylamine, N,N-di-n-butyl-4-mercaptobutylamine, 2,2-dimethylthiazolidine, etc.

[0023] The cationic resin includes, but is not limited to: sulfonated polystyrene-divinylbenzene spherical polymer.

[0024] The free mercapto compounds include, but are not limited to: methanethiol, ethanethiol, mercaptoacetic acid, mercaptopropionic acid.

[0025] The present invention further discloses a method for synthesizing 4,4-bisphenol A, which uses phenol and acetone to react to obtain a product. It is characterized in that the reaction temperature is 74-76 °C, the mass ratio of phenol to acetone is (17.5-18.5):1, and the concentration of 2,4-BPA in the reaction raw material system is controlled to be 3-3.8 wt%. In one embodiment of the present invention, the reaction temperature is 75 °C, and the mass ratio of phenol to acetone is 18.

[0026] Glossary:

[0027] 2,4-BPA: 2,4-bisphenol A

[0028] Fresh raw materials: The reaction raw materials obtained by mixing phenol and acetone

[0029] Mother liquor after reaction: It refers to the reaction solution formed after the reaction of phenol and acetone. After crystallization and solid-liquid separation, the obtained mother liquor contains phenol, acetone and some impurities, and is often recycled back to the reaction unit as part of the reaction raw materials for repeated recycling.

[0030] The present invention has the following beneficial effects:

[0031] By regulating the equilibrium concentration of 2,4-BPA in the system, and preferably further jointly regulating the mass ratio of phenol to acetone and the reaction temperature in the feed, the generation of total impurities (including various reversible and irreversible impurities) is inhibited, thereby improving the raw material selectivity, reducing the loads of the decomposition unit and the isomerization unit, and simplifying the process flow.

[0032] On the premise of improving the raw material selectivity, the purpose of simplifying the bisphenol A production process is achieved, that is, the isomerization unit is cancelled, and the decomposition unit is cancelled under appropriate operating conditions, achieving the effect of zero tar discharge. Brief Description of the Drawings

[0033] Figure 1 According to the experimental results, by regulating (increasing) the content of 2,4-BPA, the mass ratio of phenol to acetone and the reaction temperature in the feed mother liquor, the generation of the total impurity content in the reaction unit can be fully inhibited.

[0034] Figure 2 One of the process flowcharts of the present invention. This process flow demonstrates that by adopting the synthesis method of the present invention, under the working conditions where the 2,4-BPA is derived from the reaction mother liquor, the operation of the isomerization unit in the existing production process can be omitted.

[0035] Figure 3 One of the process flowcharts of the present invention. This process flow demonstrates that by adopting the synthesis method of the present invention, after the system runs stably, the operation of the decomposition unit can be further omitted, achieving the effect of zero tar emission.

[0036] Figure 4 Industry production flowchart of bisphenol A Detailed implementation manners

[0037] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0038] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0039] Example 1:

[0040] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and mercaptopropionic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 2.5%, the concentration of total impurities after the reaction increases by 13200 ppm compared with the total impurities in the feed of the reaction raw material system.

[0041] Example 2:

[0042] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and mercaptopropionic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 2.9%, the concentration of total impurities after the reaction increases by 6100 ppm compared with the total impurities in the feed of the reaction raw material system.

[0043] Example 3:

[0044] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and thiolactic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 3.1%, the concentration of total impurities after the reaction increases by 2570 ppm compared with the total impurities in the feed of the reaction raw material system.

[0045] Example 4:

[0046] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and thiolactic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 3.3%, the concentration of total impurities after the reaction increases by 120 ppm compared with the total impurities in the feed of the reaction raw material system.

[0047] Example 5:

[0048] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and thiolactic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 3.7%, the concentration of total impurities after the reaction decreases by 8000 ppm compared with the total impurities in the feed of the reaction raw material system.

[0049] Example 6:

[0050] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and thiolactic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 15. When the content of 2,4-BPA in the feed of the raw material system is 3.3%, the concentration of total impurities after the reaction increases by 4300 ppm compared with the total impurities in the feed of the reaction raw material system.

[0051] Example 7:

[0052] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and thiolactic acid is added dropwise online as the co-catalyst. The reactor temperature is 75 °C, and the mass ratio of phenol to acetone is 15. When the content of 2,4-BPA in the feed of the raw material system is 3.5%, the concentration of total impurities after the reaction increases by 680 ppm compared with the total impurities in the feed of the reaction raw material system.

[0053] Example 8:

[0054] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and mercaptopropionic acid is added dropwise online as the co-catalyst. The reactor temperature is 80 °C, and the mass ratio of phenol to acetone is 18. When the content of 2,4-BPA in the feed of the raw material system is 3.1%, the concentration of total impurities after the reaction increases by 5200 ppm compared with the total impurities in the feed of the reaction raw material system.

[0055] Example 9:

[0056] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and mercaptopropionic acid is added dropwise online as the co-catalyst. The reactor temperature is 80 °C, and the mass ratio of phenol to acetone is 15. When the content of 2,4-BPA in the feed of the raw material system is 3.3%, the concentration of total impurities after the reaction increases by 10100 ppm compared with the total impurities in the feed of the reaction raw material system.

[0057] Example 10:

[0058] The reactor is filled with sulfonated polystyrene-divinylbenzene spherical polymer as the main catalyst, and mercaptopropionic acid is added dropwise online as the co-catalyst. The reactor temperature is 80 °C, and the mass ratio of phenol to acetone is 15. When the content of 2,4-BPA in the feed of the raw material system is 3.8%, the concentration of total impurities after the reaction increases by 1590 ppm compared with the total impurities in the feed of the reaction raw material system.

[0059] According to the experimental results, by regulating (increasing) the content of 2,4-BPA, the mass ratio of phenol to acetone, and the reaction temperature in the feed mother liquor, the generation of the total impurity content in the reaction unit can be fully inhibited. According to this result, the production process can be simplified to achieve the purpose of saving production costs and reducing the emission of waste tar.

[0060] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for synthesizing 4,4-bisphenol A, which reacts phenol with acetone to obtain 4,4-bisphenol A, Characterized in that: 2,4-bisphenol A is added to the reaction raw materials containing phenol and acetone to achieve the purpose of inhibiting the generation of impurities, wherein the reaction temperature is 70 - 86 °C; The concentration range of 2,4-bisphenol A in the feed of the reaction raw material system is controlled to be 2.0 - 4.0 wt%; the mass ratio of phenol to acetone is (14 - 23):

1.

2. The synthesis method according to claim 1, wherein, The reaction raw materials are fresh raw materials, or a mixture of fresh raw materials and recycled reaction mother liquor.

3. The synthesis method according to claim 1, wherein, The value of 2,4-bisphenol A in the feed of the reaction raw material system is monitored in real time.

4. The synthesis method according to any one of claims 1 - 3, wherein, The concentration range of 2,4-bisphenol A in the feed of the reaction raw material system is controlled to be 3.0 - 4.0 wt%, and the mass ratio of phenol to acetone is (15 - 20):

1.

5. The synthesis method according to any one of claims 1 - 3, wherein, The reaction temperature is 70 - 80 °C.

6. The synthesis method according to claim 4, wherein, The reaction temperature is 70 - 80 °C.

7. The synthesis method according to any one of claims 1 - 3 or 6, the method is carried out under a catalytic system of bisphenol A commonly used in the art, and the catalytic system is a mercapto-modified cationic resin system, or a system of cationic resin and free mercapto substances.

8. The synthesis method according to claim 7, wherein the cationic resin is a sulfonated polystyrene-divinylbenzene spherical polymer, and the free mercapto substances are methanethiol, ethanethiol, mercaptoacetic acid, and / or mercaptopropionic acid.

9. The synthesis method according to claim 7, wherein, The mercapto-modified cationic resin system is a cationic resin modified with 2-mercaptoethylamine, 3-mercaptopropylamine, N,N-dimethyl-3-mercaptopropylamine, N,N-di-n-butyl-4-mercaptobutylamine, and / or 2,2-dimethylthiazolidine.

10. The synthesis method according to any one of claims 1 - 3, 6, 8 or 9, which reacts phenol with acetone to obtain a product, Characterized in that, The reaction temperature is 74 - 76 °C, the mass ratio of phenol to acetone is (17.5 - 18.5):1, and the concentration of 2,4-BPA in the feed of the reaction raw material system is controlled to be 3 - 3.8 wt%.

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