A method for inhibiting the formation of isopropenylphenol impurity in the process of synthesizing bisphenol A

Abstract

The present invention relates to the field of bisphenol A preparation, and provides a method for suppressing the generation of isopropenylphenol as an impurity during the synthesis of bisphenol A. The method at least includes increasing the content of 2,4'-BPA in a feed mother liquor during the synthesis process. Further preferably, the content of 2,4'-BPA in the feed mother liquor and the phenol-acetone mass ratio are jointly regulated. The present invention suppresses the generation of the impurity IPP during the synthesis of bisphenol A by regulating the content of 2,4'-BPA and the phenol-acetone mass ratio in the feed mother liquor, thereby improving the selectivity of the phenol raw material, reducing the burden of the separation and impurity removal unit, and also preventing the impurity IPP from being entrained into the bisphenol A product to affect the quality of the downstream polycarbonate during application, such as color.

Description

Technical Field

[0001] The invention relates to the field of bisphenol A preparation, and in particular to a method for inhibiting the generation of isopropenylphenol as an impurity during the synthesis of bisphenol A. 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 resins, epoxy resins, unsaturated polyesters, polysulfones, polyetherimides and polyarylate resins.

[0003] The synthetic route of bisphenol A is as follows:

[0004]

[0005] It can be seen that while acetone and phenol react to produce the main product bisphenol A, some by-products are also produced, such as the isomer 2,4'-BPA of bisphenol A, isopropenylphenol (IPP), C3 phenol, as well as chromane, indane, tar, etc.

[0006] C3 Phenol

[0007] Isopropenylphenol IPP

[0008] Since an excess of phenol is generally used in the reaction, in order to save costs, the phenol in the system after the reaction is recycled in actual production. Therefore, the actual production process of bisphenol A is as follows: the phenol in the mother liquor reacts with acetone and then crystallizes, and then solid-liquid separation is performed to obtain crude bisphenol A and mother liquor containing phenol and impurities. The crude bisphenol A is purified and granulated to obtain BPA products, and the mother liquor (or after impurities are removed) is reused in the previous reaction process, such as Figure 1 That is to say, the raw materials for preparing bisphenol A include mother liquor, which contains phenol, bisphenol A, 2,4'-BPA, isopropenylphenol, C3 phenol, chroman, indane, tar and other impurities in addition to phenol.

[0009] The prior art believes that most impurities will be removed from the bisphenol A product in the separation or impurity removal unit, and a small amount of impurities will be removed in the purification unit. Therefore, the requirements for the mother liquor to be recycled are not high, and generally only require that the bisphenol A content in the mother liquor is about 10%, the water content is less than 1%, and the total amount of impurities is less than 15%. When the mother liquor is fed, the supply amount of the mother liquor is controlled so that the ratio of phenol to acetone therein is within a specified range, thereby stabilizing the quality and yield of bisphenol A.

[0010] But in fact, when the impurity isopropenylphenol is generated in excessive amounts, it is difficult to remove it completely, and the residual isopropenylphenol has a great impact on the quality of bisphenol A. For example, when bisphenol A is used to produce polycarbonate, since isopropenylphenol contains a carbon-carbon double bond, it is very easy to react to generate impurities during the synthesis of polycarbonate, making the color of the polycarbonate yellow or turning yellow during the application process. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention provides a method for inhibiting the generation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A. The present invention achieves the effect of inhibiting the generation of IPP by fine-tuning (increasing) the content of 2,4'-BPA in the raw material mother liquor of synthesizing bisphenol A and adjusting the phenol-acetone mass ratio accordingly, thereby preventing IPP from being entrained into the bisphenol A product and affecting the quality of downstream polycarbonate such as color.

[0012] The invention provides a method for inhibiting the generation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A, which at least comprises increasing the content of 2,4'-BPA in the feed mother liquor during the synthesis process.

[0013] The present invention has found that by increasing the content of 2,4'-BPA in the feed mother liquor and jointly regulating other reaction conditions, the formation of isopropenylphenol can be inhibited, thereby preventing IPP from being entrained into the bisphenol A product and affecting the quality of downstream polycarbonate such as color, and increasing the selectivity of the phenol raw material, thereby reducing the load on the separation and impurity removal unit.

[0014] The prior art has not paid attention to the content of 2,4'-BPA in the mother liquor, and it is an impurity itself. It is difficult for those skilled in the art to think of increasing the content of an impurity for the purpose of obtaining high-purity bisphenol A. Moreover, bisphenol A has multiple isomers. The present invention has found that the content of 2,4'-BPA must be used as the control object. If the content of other isomers is adjusted, the formation of isopropenylphenol cannot be effectively inhibited.

[0015] Specifically, there are currently two mainstream catalytic systems for producing bisphenol A. One is a cationic resin system modified with mercapto groups (i.e., mercapto-based substances are immobilized on cationic resins), and the other is a composite system of ordinary cationic resins and free mercapto substances (co-catalysts).

[0016] The present invention has found that in the process of synthesizing bisphenol A, the content of 2,4'-BPA in the feed mother liquor and the mass ratio of phenol to acetone are jointly regulated, which is applicable to both of the above-mentioned two catalytic systems and can effectively inhibit the formation of the impurity isopropenylphenol.

[0017] In the production process of bisphenol A, multiple reaction factors need to be controlled, such as reaction temperature, phenol-acetone mass ratio, catalyst concentration, etc., which simultaneously affect multiple important reaction result indicators, such as conversion rate, selectivity and device capacity. However, among the many influencing factors, the present invention found that regulating the content of 2,4'-BPA in the feed mother liquor and the phenol-acetone mass ratio can fully inhibit the formation of isopropenylphenol. Not all factors are strongly correlated. The overall change trend is as follows: Figure 2 shown.

[0018] Specifically, in order to achieve good results, the following conditions should be followed:

[0019] When the mass ratio of phenol to acetone is 16-17, the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.8wt% or above.

[0020] When the mass ratio of phenol to acetone is 18-19, the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.4wt% or above.

[0021] When the mass ratio of phenol to acetone is above 20, the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.1wt% or above.

[0022] The increase in the phenol-acetone mass ratio can be achieved by increasing the amount of fresh phenol or mother liquor, or reducing the amount of fresh acetone. The increase in the content of 2,4'-BPA in the feed can be achieved by adding 2,4'-BPA to the system to change the equilibrium concentration of 2,4'-BPA in the system.

[0023] It should be noted that the phenol-acetone mass ratio is not necessarily an integer in actual control. In this case, rounding can be adopted to determine how to regulate the content of 2,4'-BPA in the feed mother liquor. For example, if the phenol-acetone mass ratio is 17.2, it is rounded to 17, which belongs to the first case, thereby controlling the content of 2,4'-BPA in the feed mother liquor to be 3.8wt% and above. For another example, if the phenol-acetone mass ratio is 17.8, it is rounded to 18, which belongs to the second case, thereby controlling the content of 2,4'-BPA in the feed mother liquor to be 3.4wt% and above. In addition, for the third case, the upper limit of the phenol-acetone mass ratio is inconsistent among factories, but it is generally within 30. In short, when the phenol-acetone mass ratio is between 20 and the upper limit, the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.1wt% and above.

[0024] In some specific embodiments of the present invention, for the composite catalytic system containing a free co-catalyst, the main catalyst is a sulfonated styrene-divinylbenzene copolymer, and the co-catalyst is a mercapto substance, such as mercaptopropionic acid.

[0025] In some specific embodiments of the present invention, during the synthesis of bisphenol A, the residence time of the material in the reactor is 6-10 hours, and the residence time of the material in the catalyst bed is 1-2 hours.

[0026] Through the above-mentioned precise regulation, the present invention can control the generation amount of the impurity isopropenylphenol to be within 20 ppm.

[0027] In the prior art, without regulation, the impurity isopropenylphenol is generally generated in an amount of hundreds of ppm. After separation and impurity removal, a portion (tens of ppm) will still enter the final product, affecting product quality and hindering its application in high-end optical grades. The present invention greatly reduces the generation of the impurity isopropenylphenol, reduces the burden of the separation and impurity removal units, improves the selectivity of the phenol raw material, and obtains high-quality bisphenol A.

[0028] The present invention also provides bisphenol A prepared by the above method, which has high quality and can be used to produce high-end downstream products, including polycarbonate with excellent optical properties.

[0029] The invention provides a method for inhibiting the generation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A. The method inhibits the generation of IPP as an impurity in the process of synthesizing bisphenol A by regulating the content of 2,4'-BPA and the mass ratio of phenol to acetone in a feed mother liquor, so as to prevent the IPP as an impurity from being carried into a bisphenol A product and affecting the quality of downstream polycarbonate such as color. Meanwhile, the selectivity of the phenol raw material is improved, and the burden of the separation and impurity removal unit is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the actual main production process of bisphenol A at present;

[0031] Figure 2 The present invention shows the influence of the content of 2,4'-BPA in the feed mother liquor and the mass ratio of phenol to acetone on the formation of isopropenylphenol. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are 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.

[0033] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0034] Unless otherwise stated, the raw materials and auxiliary materials involved in the following examples can be purchased from the market.

[0035] Example 1

[0036] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0037] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0038] It was found that when the 2,4'-BPA content in the mother liquor feed was 2.7% and the mass ratio of phenol to acetone was 16, the concentration of IPP increased by 72 ppm after the reaction.

[0039] The concentration change of IPP is obtained by comparing the difference in IPP content in the reactor inlet and outlet streams, and the increase is the IPP generated in the reaction.

[0040] The concentration change of IPP is measured by gas chromatography; when the concentration is lower than 50 ppm, it is estimated by extrapolation (i.e., the standard curve of the chromatogram only covers part of the concentration range, and too low or too high concentration can only be estimated by the outer edge of the standard curve according to the formula of the standard curve).

[0041] Example 2

[0042] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0043] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0044] It was found that when the 2,4'-BPA content in the mother liquor feed was 2.7% and the mass ratio of phenol to acetone was 18, the concentration of IPP increased by 55 ppm after the reaction.

[0045] Example 3

[0046] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0047] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 80°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0048] It was found that when the 2,4'-BPA content in the mother liquor feed was 2.7% and the mass ratio of phenol to acetone was 18, the concentration of IPP increased by 58 ppm after the reaction.

[0049] Example 4

[0050] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0051] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0052] It was found that when the 2,4'-BPA content in the mother liquor feed was 2.7% and the mass ratio of phenol to acetone was 20, the concentration of IPP increased by 38 ppm after the reaction.

[0053] Example 5

[0054] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0055] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0056] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.8% and the mass ratio of phenol to acetone was 16, the concentration of IPP increased by 19 ppm after the reaction.

[0057] Example 6

[0058] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0059] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0060] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.4% and the mass ratio of phenol to acetone was 18, the concentration of IPP increased by 17 ppm after the reaction.

[0061] Example 7

[0062] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0063] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 80°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0064] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.4% and the mass ratio of phenol to acetone was 18, the concentration of IPP increased by 18 ppm after the reaction.

[0065] Example 8

[0066] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0067] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0068] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.1% and the mass ratio of phenol to acetone was 20, the concentration of IPP increased by 13 ppm after the reaction.

[0069] Example 9

[0070] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0071] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0072] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.6% and the mass ratio of phenol to acetone was 18, the concentration of IPP increased by 9 ppm after the reaction.

[0073] Example 10

[0074] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0075] The reactor is filled with a cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a main catalyst, and a mercapto substance (mercaptopropionic acid) is added online as a co-catalyst to react excess phenol with acetone in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0076] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.5% and the mass ratio of phenol to acetone was 20, the concentration of IPP increased by 2ppm after the reaction.

[0077] Embodiment 11

[0078] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0079] The reactor is filled with a thiol-modified cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a catalyst, and excess phenol and acetone are reacted in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0080] It was found that when the 2,4'-BPA content in the mother liquor feed was 2.7% and the mass ratio of phenol to acetone was 20, the concentration of IPP increased by 52 ppm after the reaction.

[0081] Example 12

[0082] This embodiment provides a method for inhibiting the formation of isopropenylphenol (IPP) as an impurity in the process of synthesizing bisphenol A, as follows:

[0083] The reactor is filled with a thiol-modified cation exchange resin (sulfonated styrene-divinylbenzene copolymer) as a catalyst, and excess phenol and acetone are reacted in the reactor (phenol is provided by the mother liquor of the factory). The reactor temperature is 75°C; the residence time of the material in the reactor is about 9 hours, and the residence time of the material in the catalyst bed is about 1 hour.

[0084] It was found that when the 2,4'-BPA content in the mother liquor feed was 3.5% and the mass ratio of phenol to acetone was 20, the concentration of IPP increased by 11 ppm after the reaction.

[0085] The quality (color) of the downstream product polycarbonate prepared by using bisphenol A prepared in Example 5, 6, 7, 8, 9, 10 or 12 is significantly better than the polycarbonate prepared by using bisphenol A provided in Example 1, 2, 3, 4 or 11 as raw material.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for inhibiting the formation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A, characterized in that: At least including increasing the 2,4'-BPA content in the feed mother liquor during the synthesis process; The content of 2,4'-BPA and the mass ratio of phenol to acetone in the feed mother liquor were jointly regulated; The mass ratio of phenol to acetone is 16-17, and the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.8wt% or above; Or, the mass ratio of phenol to acetone is 18-19, and the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.4wt% or above; Or, the phenol-acetone mass ratio is 20 or more, and the content of 2,4'-BPA in the feed mother liquor is controlled to be 3.1wt% or more; The method is applicable to a composite catalyst system containing a free co-catalyst and a cationic resin system modified with mercapto groups.

2. The method for suppressing the formation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A according to claim 1, characterized in that: For the composite catalytic system containing a free co-catalyst, the main catalyst is a sulfonated styrene-divinylbenzene copolymer, and the co-catalyst is a mercapto-based substance.

3. The method for suppressing the formation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A according to claim 1 or 2, characterized in that: During the synthesis of bisphenol A, the residence time of the material in the reactor is 6-10 hours, and the residence time of the material in the catalyst bed is 1-2 hours.

4. The method for suppressing the formation of isopropenylphenol as an impurity in the process of synthesizing bisphenol A according to claim 3, characterized in that: The amount of the impurity isopropenylphenol generated is controlled within 20 ppm.

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