Separation and purification method of phenol hydroxylation reaction liquid

Abstract

The invention relates to a phenol hydroxylation reaction liquid separation and purification method, which comprises: dehydrating a phenol hydroxylation reaction liquid, and carrying out decoking to reduce the operation temperature of subsequent separation so as to obtain a first material; carrying out vacuum rectification on the first material through a dephenolization tower to obtain a second material; wherein the dephenolization tower comprises a first dephenolization tower and a second dephenolization tower, the second dephenolization tower and the first dephenolization tower are thermally integrated, tower top steam of the second dephenolization tower is used as a reboiler heat source of the first dephenolization tower, and meanwhile, tower top steam of the second dephenolization tower is condensed; the tower top operation pressure of the second dephenolization tower is higher than that of the first dephenolization tower; and separating the second material to obtain catechol and hydroquinone. The technical problem that the benzenediol product yield and the separation energy consumption are difficult to balance in an existing phenol hydroxylation reaction liquid separation system is solved.

Description

Technical Field

[0001] The present application relates to the field of chemical separation technology, and in particular to a method for separating and purifying a phenol hydroxylation reaction liquid. Background Art

[0002] Catechol and hydroquinone are two important fine chemical products with a wide range of applications. Catechol is an important pesticide and pharmaceutical intermediate, and can also be used to make spices, dyes, photosensitive materials, electroplating materials, etc. Hydroquinone is mainly used as a developer for photographic films, anthraquinone dyes, azo dyes, auxiliary solvents for synthetic ammonia desulfurization processes, rubber antioxidants, inhibitors, stabilizers for paint varnishes, and gasoline antioxidants. The method for synthesizing o- / hydroquinone by phenol hydroxylation reaction using hydrogen peroxide as an oxidant is usually used. For the phenol hydroxylation reaction liquid, the separation tasks mainly include dehydration, detarring, recovery of phenol, and refining of catechol and hydroquinone products.

[0003] However, in the process of producing o- / hydroquinone by hydroxylation of phenol, tar-like byproducts are inevitably generated while obtaining o- / hydroquinone. Because o- / hydroquinone is a heat-sensitive substance, it is easy to oxidize and condense to form tar, and o- / hydroquinone is easier to convert into tar than hydroquinone. In the separation and purification process, the amount of tar generated increases with the increase of the operating temperature of the distillation process and the extension of the operating time. Tar is the substance with the highest boiling point in the separation system. From the perspective of energy saving, it consumes the least energy to remove it at the end. However, if the decoking step is performed at the end of the separation, although the separation energy consumption is reduced, since the boiling point of tar is above 285°C, its presence will increase the operating temperature of the distillation system, thereby aggravating the heat sensitivity of o- / hydroquinone, promoting the formation of phenol tar, and causing product loss of o- / hydroquinone. And the longer the residence time of tar at high temperature, the greater the viscosity becomes, and the worse the fluidity becomes, which brings great difficulties to the transportation and separation of materials. Therefore, removing the tar at the end of the separation process will result in a decrease in product yield, or removing the tar at the beginning of the separation process will result in an increase in separation energy consumption, making it difficult to balance the contradiction between the yield of the hydroquinone product and the separation energy consumption. Summary of the invention

[0004] The present application provides a separation and purification method for a phenol hydroxylation reaction liquid, so as to solve the technical problem that it is difficult to balance the yield of a hydroquinone product and the separation energy consumption in the existing separation system of the phenol hydroxylation reaction liquid.

[0005] In a first aspect, the present application provides a method for separating and purifying a phenol hydroxylation reaction solution, the method comprising:

[0006] Dehydrating the phenol hydroxylation reaction liquid and then decoking it to reduce the operating temperature of subsequent separation to obtain a first material;

[0007] The first material is subjected to vacuum distillation through a dephenolization tower to obtain a second material; wherein the dephenolization tower includes a first dephenolization tower and a second dephenolization tower,

[0008] The second dephenolization tower is heat-integrated with the first dephenolization tower, the top steam of the second dephenolization tower is used as the reboiler heat source of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed, and the top operating pressure of the second dephenolization tower is higher than the top operating pressure of the first dephenolization tower;

[0009] The second material is separated to obtain catechol and hydroquinone.

[0010] Optionally, the top operating pressure of the first dephenolization tower is 1 kPaA to 20 kPaA.

[0011] Optionally, the top operating pressure of the second dephenolization tower is 20 kPaA to 50 kPaA.

[0012] Optionally, the temperature of the top steam of the second dephenolization tower is 130°C to 160°C.

[0013] Optionally, the process parameters of the first dephenolization tower include: a bottom temperature of 110°C to 130°C, a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

[0014] Optionally, the process parameters of the second dephenolization tower include: a bottom temperature of 210° C. to 230° C., a theoretical plate number of 15 to 50, and a reflux ratio of 0.1 to 3.

[0015] Optionally, the decoking is processed by a decoking tower, and the process parameters of the decoking tower include: a tower top operating pressure of 0.5kPaA to 8kPaA, a tower bottom temperature of 210°C to 260°C, a theoretical tower plate number of 5 to 40, and a reflux ratio of 0.5 to 4.

[0016] Optionally, the dehydration is processed by a dehydration tower, and the process parameters of the dehydration tower include: a tower top operating pressure of 2kPaA to 50kPaA, a tower bottom temperature of 150°C to 180°C, a theoretical plate number of 10 to 40, and a reflux ratio of 0.5 to 4.

[0017] Optionally, the second material is separated to obtain catechol and hydroquinone, comprising:

[0018] The second material is subjected to a first separation through a catechol tower to obtain catechol and a third material;

[0019] The third material is subjected to a second separation through a hydroquinone tower to obtain hydroquinone; wherein,

[0020] The process parameters of the catechol tower include: top operating pressure 2kPaA-25kPaA, bottom temperature 200°C-230°C, theoretical plate number 15-50, reflux ratio 0.5-4;

[0021] The process parameters of the hydroquinone tower include: a tower top operating pressure of 0.5 kPaA to 12 kPaA, a tower bottom temperature of 210° C. to 260° C., a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

[0022] Optionally, the chemical components of the phenol hydroxylation reaction solution include: water, phenol, catechol, hydroquinone and tar; wherein, in terms of mass fraction,

[0023] The content of water is 10% to 55%, the content of phenol is 25% to 70%, the content of catechol is 5% to 25%, the content of hydroquinone is 7% to 25%, and the content of tar is 1% to 5%.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] The separation and purification method of the phenol hydroxylation reaction liquid provided in the embodiment of the present application places the decoking step at the front of the separation process, reduces the temperature of the subsequent separation process, and improves the yield of hydroquinone, but at the same time, the energy consumption will increase. On this basis, the double-tower heat integration is adopted to save separation energy consumption; the second dephenolation tower is heat-integrated with the first dephenolation tower, and the double tower replaces the single tower, and the top steam of the second dephenolation tower is used as the heat source of the first dephenolation tower reboiler, and the top steam of the second dephenolation tower is condensed. In order to ensure the heat transfer temperature difference, the operating pressure of the double tower is different, and the operating pressure of the second dephenolation tower is higher than the operating pressure of the first dephenolation tower, so that the operating temperature of the top of the second dephenolation tower is about 20 ° C higher than the operating temperature of the first dephenolation tower kettle. The heat integration makes full use of the temperature difference between the cold and hot media. In the double-tower process, it is only necessary to add a cooling medium to the top of the first dephenolation tower and add steam to the kettle of the second dephenolation tower. No additional steam and cooling medium are needed in the middle of the double tower, that is, the refrigerant at the top of the second dephenolation tower and the heat medium of the reboiler of the first dephenolation tower are saved, and the separation energy consumption is reduced. Theoretically, compared with a single tower, the distillation energy saving effect of the double tower heat integration is about 30-50%. In summary, the technical problem of the difficulty in balancing the yield of the hydroquinone product and the separation energy consumption in the existing separation system of the phenol hydroxylation reaction liquid is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic flow chart of a method for separating and purifying a phenol hydroxylation reaction liquid provided in an embodiment of the present application;

[0029] Figure 2 A schematic structural diagram of a system for separating and purifying a phenol hydroxylation reaction liquid provided in an embodiment of the present application; wherein, 1 is a dehydration tower, 2 is a decoking tower, 3 is a thin film evaporator, 4 is a first dephenolation tower, 5 is a second dephenolation tower, 6 is a catechol tower, 7 is a hydroquinone tower, 8 is an extraction tower, 9 is a solvent recovery tower, 10 is a separator, 11 is a distillation tower, 101 is a phenol hydroxylation reaction liquid, 102 is tar, 103 is phenol, 104 is phenol, 105 is catechol, 106 is hydroquinone, 107 is phenol, and 108 is waste water. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0032] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] In the first aspect, the present application provides a method for separating and purifying a phenol hydroxylation reaction solution, see Figure 1 , the method comprising:

[0035] S1. Dehydrating the phenol hydroxylation reaction liquid and then decoking it to reduce the operating temperature of subsequent separation to obtain a first material; wherein the first material includes: phenol, catechol and hydroquinone.

[0036] In the embodiment of the present application, for the phenol hydroxylation reaction liquid, the separation tasks mainly include dehydration, detarring, recovery of phenol, catechol and hydroquinone product refining. In the process of phenol hydroxylation to produce o- / hydroquinone, while obtaining hydroquinone, tar by-products are inevitably generated. Because hydroquinone is a heat-sensitive substance, it is easy to oxidize and condense to generate tar. Since the boiling point of tar is above 285°C, its presence will increase the operating temperature of the distillation system, thereby aggravating the heat sensitivity of o- / hydroquinone and promoting the generation of phenol tar. Therefore, in step S1, in order to reduce the operating temperature of the separation system, reduce the generation of tar, and increase the product yield of hydroquinone, decoking is performed immediately after dehydration. Tar is separated from phenol and hydroquinone, and then phenol, catechol and hydroquinone are separated in sequence, and hydroquinone is extracted from the top of the tower to avoid subsequent decolorization.

[0037] In some embodiments, the chemical components of the phenol hydroxylation reaction solution include: water, phenol, catechol, hydroquinone and tar; wherein, by mass fraction,

[0038] The content of water is 10% to 55%, the content of phenol is 25% to 70%, the content of catechol is 5% to 25%, the content of hydroquinone is 7% to 25%, and the content of tar is 1% to 5%.

[0039] In an embodiment of the present application, the phenol hydroxylation reaction liquid has the above-mentioned chemical composition. Specifically, the water content can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% and the like, the phenol content can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% and the like, the catechol content can be 5%, 10%, 15%, 20%, 25% and the like, the hydroquinone content can be 7%, 10%, 15%, 20%, 25% and the like, and the tar content can be 1%, 2%, 3%, 4%, 5% and the like.

[0040] In some embodiments, the decoking is processed by a decoking tower, and the process parameters of the decoking tower include: a tower top operating pressure of 0.5kPaA to 8kPaA, a tower bottom temperature of 210°C to 260°C, a theoretical plate number of 5 to 40, and a reflux ratio of 0.5 to 4.

[0041] In some embodiments, the dehydration is processed by a dehydration tower, and the process parameters of the dehydration tower include: top operating pressure 2kPaA~50kPaA, bottom temperature 150℃~180℃, theoretical plate number 10~40, and reflux ratio 0.5~4.

[0042] In the embodiments of the present application, specifically, among the process parameters of the above-mentioned dehydration tower, the top operating pressure can be 2kPaA, 5kPaA, 10kPaA, 15kPaA, 20kPaA, 25kPaA, 30kPaA, 35kPaA, 40kPaA, 45kPaA, 50kPaA, etc., the bottom temperature can be 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, etc., the theoretical number of plates can be 10, 15, 20, 25, 30, 40, etc., and the reflux ratio can be 0.5, 1, 2, 3, 4, etc. Among the process parameters of the above-mentioned decoking tower, the top operating pressure can be 0.5kPaA, 1kPaA, 2kPaA, 4kPaA, 6kPaA, 8kPaA, etc., the bottom temperature can be 210°C, 260°C, 220°C, 230°C, 240°C, 250°C, 260°C, etc., the theoretical number of plates can be 5, 10, 15, 20, 25, 30, 40, etc., and the reflux ratio can be 0.5, 1, 2, 3, 4, etc.

[0043] For the separation and purification method of the phenol hydroxylation reaction liquid and the corresponding separation and purification system of the phenol hydroxylation reaction liquid, please refer to Figure 2 Specifically, the above S1 includes: sending the phenol hydroxylation reaction liquid 101 into the dehydration tower 1 for vacuum distillation and dehydration, the dehydration tower bottom material enters the decoking tower 2, the decoking tower 2 performs vacuum distillation, and tar 102 is discharged from the bottom of the tower, and the tar enters the thin film evaporator 3 to recover hydroquinone and other lighter components, and then discharges high boiling products.

[0044] In addition, phenol-containing water is extracted from the top of the dehydration tower 1, and the phenol-containing wastewater enters the atmospheric extraction tower 8, countercurrently contacts with the extractant from the bottom of the extraction tower 8, and the top extract phase enters the solvent recovery tower 9, and the bottom extract phase is wastewater. The bottom of the solvent recovery tower 9 extracts phenol 107 and returns it to the reaction section. The top distillate of the solvent recovery tower 9 is condensed and layered, and the upper organic phase is recycled as the extractant. The lower aqueous phase is combined with the wastewater from the bottom of the extraction tower 8 and enters the distillation tower 11 to recover the extractant dissolved in the aqueous phase. The top distillate of the distillation tower 11 is condensed and layered, and the upper organic phase is recycled as the extractant. The lower aqueous phase returns to the entrance of the distillation tower 11, and the bottom wastewater 108 is sent to the water treatment unit.

[0045] S2, subjecting the first material to vacuum distillation through a dephenolization tower to obtain a second material; wherein the dephenolization tower includes a first dephenolization tower and a second dephenolization tower, and the second material includes: catechol and hydroquinone;

[0046] The second dephenolization tower is heat-integrated with the first dephenolization tower, the top steam of the second dephenolization tower is used as the reboiler heat source of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed, and the top operating pressure of the second dephenolization tower is higher than the top operating pressure of the first dephenolization tower;

[0047] In the embodiments of the present application, in order to lower the operating temperature of the separation system, reduce the production of tar, and increase the product yield of hydroquinone, the tar present in the reaction liquid should be discharged as early as possible in the separation and purification process of the phenol hydroxylation reaction liquid. However, as the substance with the highest boiling point in the separation system, the earlier the tar is discharged, the greater the energy consumption of the separation system.

[0048] Therefore, based on the above-mentioned problem that tar is placed at the front of the separation process to remove it, which leads to increased separation energy consumption, double-tower heat integration is used to save separation energy consumption; the second dephenolization tower is heat-integrated with the first dephenolization tower, and the double tower is used instead of the single tower. The top steam of the second dephenolization tower is used as the heat source of the reboiler of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed. In order to ensure the heat transfer temperature difference, the operating pressures of the two towers are different. The operating pressure of the second dephenolization tower is higher than the operating pressure of the first dephenolization tower, so that the operating temperature of the top of the second dephenolization tower is about 20°C higher than the operating temperature of the kettle of the first dephenolization tower. This heat integration makes full use of the temperature difference between the cold and hot media. In the double-tower process, only the cooling medium needs to be added to the top of the first dephenolization tower and the steam needs to be added to the kettle of the second dephenolization tower. No additional steam and cooling medium are needed in the middle of the double towers, that is, the refrigerant at the top of the second dephenolization tower and the heat medium of the reboiler of the first dephenolization tower are saved, and the separation energy consumption is reduced. In theory, compared with a single tower, the distillation energy saving effect of the double-tower heat integration is about 30-50%.

[0049] In some embodiments, the top operating pressure of the first dephenolization tower is 1 kPaA to 20 kPaA.

[0050] In some embodiments, the top operating pressure of the second dephenolization tower is 20 kPaA to 50 kPaA.

[0051] In some embodiments, the temperature of the top steam of the second dephenolization tower is 130°C to 160°C.

[0052] In the embodiment of the present application, the above-mentioned decoking tower, the first dephenolization tower, the second dephenolization tower, the catechol tower and the hydroquinone tower are all operated under reduced pressure to reduce the operating temperature. This is because catechol and hydroquinone are heat-sensitive substances, and excessively high temperatures will cause oxidation and condensation to generate tar, resulting in product loss of catechol. Specifically, the top operating pressure of the first dephenolization tower can be 1kPaA, 2kPaA, 4kPaA, 6kPaA, 8kPaA, 10kPaA, 12kPaA, 14kPaA, 16kPaA, 18kPaA, 20kPaA, etc., the top operating pressure of the second dephenolization tower can be 20kPaA, 25kPaA, 30kPaA, 35kPaA, 40kPaA, 45kPaA, 50kPaA, etc., and the top steam of the second dephenolization tower can be 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, etc.

[0053] In some embodiments, the process parameters of the first dephenolization tower include: a bottom temperature of 110° C. to 130° C., a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

[0054] In some embodiments, the process parameters of the second dephenolization tower include: a bottom temperature of 210° C. to 230° C., a theoretical plate number of 15 to 50, and a reflux ratio of 0.1 to 3.

[0055] In the embodiment of the present application, in the process parameters of the first dephenolization tower, specifically, the tower bottom temperature can be 110°C, 115°C, 120°C, 125°C, 130°C, etc., the number of plates can be 4, 5, 10, 15, 20, 25, 30, etc., and the reflux ratio can be 0.1, 0.5, 1, 2, 3, etc. In the process parameters of the second dephenolization tower, specifically, the tower bottom temperature can be 210°C, 215°C, 220°C, 225°C, 230°C, etc., the number of plates can be 15, 20, 25, 30, 35, 40, 45, 50, etc., and the reflux ratio can be 0.1, 0.5, 1, 2, 3, etc.

[0056] Specifically, the above S2 includes: the material produced from the top of the dephenolization tower 2 enters the first dephenolization tower 4 for vacuum distillation. The phenol 103 produced from the top of the first dephenolization tower 4 is returned to the reaction section, and the material in the bottom of the first dephenolization tower 4 is sent to the second dephenolization tower 5 for vacuum distillation. The second dephenolization tower 5 is heat-integrated with the first dephenolization tower 4, and the top steam of the second dephenolization tower 5 is used as the heat source of the reboiler of the first dephenolization tower 4, which saves the top refrigerant of the second dephenolization tower 5 and the reboiler heat medium of the first dephenolization tower 4, and reduces the separation energy consumption.

[0057] S3, separating the second material to obtain catechol and hydroquinone.

[0058] In some embodiments, the separation of the second material to obtain catechol and hydroquinone comprises:

[0059] The second material is subjected to a first separation through a catechol tower to obtain catechol and a third material;

[0060] The third material is subjected to a second separation through a hydroquinone tower to obtain hydroquinone; wherein,

[0061] The process parameters of the catechol tower include: top operating pressure 2kPaA-25kPaA, bottom temperature 200°C-230°C, theoretical plate number 15-50, reflux ratio 0.5-4;

[0062] The process parameters of the hydroquinone tower include: a tower top operating pressure of 0.5 kPaA to 12 kPaA, a tower bottom temperature of 210° C. to 260° C., a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

[0063] In the embodiment of the present application, among the process parameters of the catechol tower, specifically, the top operating pressure can be 2kPaA, 5kPaA, 10kPaA, 15kPaA, 20kPaA, 25kPaA, the bottom temperature can be 200°C, 210°C, 220°C, 230°C, the theoretical number of plates can be 15, 20, 25, 30, 35, 40, 45, 50, and the reflux ratio can be 0.5, 1, 2, 3, 4, etc. Among the process parameters of the hydroquinone tower, specifically, the top operating pressure can be 0.5, 1, 2, 4, 6, 8, 10, 12 kPaA, the bottom temperature can be 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, the theoretical number of plates can be 4, 5, 10, 15, 20, 25, 30, etc., and the reflux ratio can be 0.1, 0.5, 1, 2, 3, etc.

[0064] Specifically, the above S3 includes: phenol 104 is taken out from the top of the second dephenolization tower 5 and sent back to the reaction section, and the bottom material enters the catechol tower 6. The bottom material after the phenol removal is sent to the catechol tower 6 for vacuum distillation, catechol 105 is taken out from the top of the catechol tower 6, and the bottom material enters the hydroquinone tower 7. Hydroquinone 106 is taken out from the top of the hydroquinone tower 7, and the heavy components are discharged from the bottom of the tower. The heavy components are sent to the feed port of the decoking tower 2 to recover hydroquinone.

[0065] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0066] The present application embodiment provides a method for separating and purifying a phenol hydroxylation reaction liquid, the method comprising:

[0067] S11, dehydrating the phenol hydroxylation reaction liquid, and then decoking it to reduce the operating temperature of subsequent separation to obtain a first material;

[0068] S21, subjecting the first material to vacuum distillation through a dephenolization tower to obtain a second material; wherein the dephenolization tower comprises a first dephenolization tower and a second dephenolization tower,

[0069] The second dephenolization tower is heat-integrated with the first dephenolization tower, the top steam of the second dephenolization tower is used as the reboiler heat source of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed, and the top operating pressure of the second dephenolization tower is higher than the top operating pressure of the first dephenolization tower;

[0070] S31, separating the second material to obtain catechol and hydroquinone. For specific separation and purification steps, please refer to Examples 1-2.

[0071] Example 1

[0072] The raw liquid is introduced into the dehydration tower at a flow rate of 17036 kg / h. The mass composition of the raw liquid is 32.2% water, 48.1% phenol, 7.7% catechol, 10.1% hydroquinone, and 1.8% tar. The operating pressure of the dehydration tower is 50 kPaA, the reflux ratio is 2, and the bottom temperature is 167°C.

[0073] Phenolic wastewater is discharged from the top of the dehydration tower and enters the extraction tower. The mass composition of phenolic wastewater is 5.6% phenol and 94.4% water. The operating pressure of the extraction tower is normal pressure, the operating temperature is normal temperature, the solvent mass ratio is 0.07, the extractant is the dispersed phase, the phenolic aqueous solution is the continuous phase, and the countercurrent operation is adopted. The tower bottom extract phase (wastewater) contains 275ppm phenol and 0.5% extractant is dissolved. The mass composition of the top extract phase is 42.1% phenol, 11.3% water, and 46.5% extractant. The extract phase enters the solvent recovery tower to recover the extractant. The operating pressure of the solvent recovery tower is normal pressure, the reflux ratio is 0.12, and the tower bottom temperature is 183°C. The tower bottom is extracted with a purity of ≥99% phenol and returned to the reaction section. The top distillate is condensed and layered. The upper organic phase is recycled as the extractant. The lower aqueous phase is combined with the wastewater from the extraction tower bottom and enters the distillation tower to recover the extractant dissolved in the aqueous phase. The operating pressure of the distillation tower is atmospheric pressure, and the temperature of the tower bottom is 100°C. The overhead distillate is condensed and layered, the upper organic phase is recycled as an extractant, and the lower aqueous phase is returned to the entrance of the distillation tower. The wastewater in the tower bottom contains 275ppm phenol and 10ppm extractant, which is sent to the water treatment unit.

[0074] The materials in the bottom of the dehydration tower enter the decoking tower, the operating pressure of the decoking tower is 5kPaA, the reflux ratio is 1.1, and the bottom temperature is 255℃. Tar is discharged from the bottom of the tower, and the tar enters the thin film evaporator to recover hydroquinone and other lighter components, and then high boiling products are discharged. The mass composition of the distillate at the top of the tower is 73.1% phenol, 12.2% catechol, and 14.7% hydroquinone, and the distillate is sent to the first dephenolization tower. The operating pressure of the first dephenolization tower is 5kPaA, the reflux ratio is 0.4, and the bottom temperature is 115℃. The phenol with a purity of ≥99% extracted from the top of the tower is returned to the reaction section, and the mass composition of the bottom material is 59.1% phenol, 18.5% catechol, and 22.4% hydroquinone, and the bottom liquid is sent to the second dephenolization tower.

[0075] The operating pressure of the second dephenolization tower is 30kPaA, the reflux ratio is 0.4, and the bottom temperature is 220℃. The phenol with a purity of ≥99% is extracted from the top of the tower and returned to the reaction section. The bottom material mass composition is 45.2% catechol and 54.8% hydroquinone. The second dephenolization tower is heat-integrated with the first dephenolization tower. The top steam of the second dephenolization tower is used as the heat source of the reboiler of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed. The bottom liquid of the second dephenolization tower is sent to the catechol tower.

[0076] The operating pressure of the catechol tower is 10 kPaA, the reflux ratio is 1.1, and the bottom temperature is 214°C. The catechol product with a purity of ≥99% is obtained at the top of the tower, and the output from the bottom of the tower is sent to the hydroquinone tower.

[0077] The operating pressure of the hydroquinone tower is 5 kPaA, the reflux ratio is 0.4, and the bottom temperature is 255°C. A hydroquinone product with a purity of ≥99% is obtained at the top of the tower, and a small amount of tar and hydroquinone are returned to the inlet of the thin film evaporator to recover the hydroquinone.

[0078] The yield and separation energy consumption of the hydroquinone product in Example 1 were analyzed:

[0079] The main energy consumption of the first dephenolization tower and the second dephenolization tower is steam consumption, that is, the energy consumption of the second dephenolization tower kettle reboiler is 1078kw.

[0080] The total yield of hydroquinone was 98.1%.

[0081] Example 2

[0082] The raw liquid is passed into the dehydration tower at a flow rate of 17036 kg / h. The mass composition of the raw liquid is 44.4% water, 34.3% phenol, 8.1% catechol, 11.1% hydroquinone, and 2.1% tar. The operating pressure of the dehydration tower is 50 kPaA, the reflux ratio is 2, and the bottom temperature is 171°C.

[0083] The phenol-containing wastewater is discharged from the top of the dehydration tower and enters the extraction tower. The mass composition of the phenol-containing wastewater is 6.5% phenol and 93.5% water.

[0084] The operating pressure of the extraction tower is normal pressure, the operating temperature is normal temperature, the solvent mass ratio is 0.07, the extractant is the dispersed phase, the phenol-containing aqueous solution is the continuous phase, and the countercurrent operation is adopted. The tower bottom extract phase (wastewater) contains 273ppm phenol and 0.5% extractant is dissolved. The mass composition of the top extract phase is 44.2% phenol, 11.9% water, and 43.9% extractant. The extract phase enters the solvent recovery tower to recover the extractant. The operating pressure of the solvent recovery tower is normal pressure, the reflux ratio is 0.13, and the tower bottom temperature is 183°C. The tower bottom is extracted with a purity of ≥99% phenol and returned to the reaction section. The top distillate is condensed and layered, the upper organic phase is recycled as the extractant, and the lower aqueous phase is combined with the wastewater from the extraction tower bottom and enters the stripping tower to recover the extractant dissolved in the aqueous phase. The operating pressure of the stripping tower is normal pressure, and the tower bottom temperature is 100°C. The top distillate is condensed and layered, the upper organic phase is recycled as an extractant, and the lower aqueous phase is returned to the inlet of the distillation tower. The wastewater in the bottom of the tower contains 273ppm phenol and 10ppm extractant, which is sent to the water treatment unit.

[0085] The materials in the bottom of the dehydration tower enter the decoking tower, the operating pressure of the decoking tower is 6kPaA, the reflux ratio is 1.6, and the bottom temperature is 258℃. Tar is discharged from the bottom of the tower, and the tar enters the thin film evaporator to recover hydroquinone and other lighter components, and then high boiling products are discharged. The mass composition of the distillate at the top of the tower is 63% phenol, 16.3% catechol, and 20.7% hydroquinone, and the distillate is sent to the first dephenolization tower. The operating pressure of the first dephenolization tower is 6kPaA, the reflux ratio is 0.3, and the bottom temperature is 123℃. The phenol with a purity of ≥99% extracted from the top of the tower is returned to the reaction section, and the mass composition of the bottom material is 46.2% phenol, 23.6% catechol, and 30.2% hydroquinone, and the bottom liquid is sent to the second dephenolization tower.

[0086] The operating pressure of the second dephenolization tower is 35kPaA, the reflux ratio is 0.5, and the bottom temperature is 226℃. ≥99% of the phenol is extracted from the top of the tower and returned to the reaction section. The bottom material mass composition is 43.8% catechol and 56.2% hydroquinone. The second dephenolization tower is heat-integrated with the first dephenolization tower. The top steam of the second dephenolization tower is used as the heat source of the reboiler of the first dephenolization tower. At the same time, the top steam of the second dephenolization tower is condensed. The bottom liquid of the second dephenolization tower is sent to the catechol tower.

[0087] The operating pressure of the catechol tower is 10 kPaA, the reflux ratio is 1.2, and the bottom temperature is 214°C. The catechol product with a purity of ≥99% is obtained at the top of the tower, and the bottom discharge is sent to the hydroquinone tower.

[0088] The operating pressure of the hydroquinone tower is 5 kPaA, the reflux ratio is 0.4, and the bottom temperature is 255°C. A hydroquinone product with a purity of ≥99% is obtained at the top of the tower, and a small amount of tar and hydroquinone are returned to the inlet of the thin film evaporator to recover the hydroquinone.

[0089] The yield and separation energy consumption of the hydroquinone product in Example 2 were analyzed:

[0090] The main energy consumption of the first dephenolization tower and the second dephenolization tower is steam consumption, that is, the energy consumption of the second dephenolization tower kettle reboiler is 785kw.

[0091] The total yield of hydroquinone was 98.0%.

[0092] Comparative Example 1

[0093] Taking Example 1 as a benchmark, the distillate from the top of the decoking tower is sent to the dephenolization tower (single tower) for energy consumption comparison. The mass composition of the effluent is 73.1% phenol, 12.2% catechol, and 14.7% hydroquinone.

[0094] The distillate from the top of the decoking tower is sent to the dephenolization tower (single tower) to recover phenol. The operating pressure of the dephenolization tower is 5kPaA, the reflux ratio is 0.3, and the temperature of the tower bottom is 174°C. The phenol with a purity of ≥99% is recovered from the top of the tower and returned to the reaction section. The mass composition of the tower bottom material is 45.2% catechol and 54.8% hydroquinone. The energy consumption of the reboiler of the dephenolization tower (single tower) is 1645kw. By comparing with the double tower process of the first dephenolization tower and the second dephenolization tower in Example 1, the heat-integrated double tower saves about 34% energy consumption than the single tower.

[0095] Comparative Example 2

[0096] Referring to the separation method of Chinese patent CN101054340A: the hydroxylation reaction product is sent to a normal pressure dehydration tower, and the phenol-containing wastewater is discharged from the top of the tower. The bottom liquid of the dehydration tower passes through the main dephenolation tower, the auxiliary dephenolation tower, the catechol distillation tower, and the hydroquinone distillation tower in sequence to obtain catechol and hydroquinone products with a purity greater than 99%. Finally, the tar is discharged through the decoking tower. This process isolates the high-boiling products of the tar in the last step of separation. According to the data in Example 1 of patent CN101054340A, it can be calculated that the total yield of hydroquinone is about 97%, and the product yield is lower than the method of the embodiment of this application.

[0097] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for separating and purifying a phenol hydroxylation reaction liquid, characterized in that: The method comprises: Dehydrating the phenol hydroxylation reaction liquid and then decoking it to reduce the operating temperature of subsequent separation to obtain a first material; The first material is subjected to vacuum distillation through a dephenolization tower to obtain a second material; wherein the dephenolization tower includes a first dephenolization tower and a second dephenolization tower, The second dephenolization tower is heat-integrated with the first dephenolization tower, the top steam of the second dephenolization tower is used as the reboiler heat source of the first dephenolization tower, and the top steam of the second dephenolization tower is condensed, and the top operating pressure of the second dephenolization tower is higher than the top operating pressure of the first dephenolization tower; The second material is separated to obtain catechol and hydroquinone.

2. The method according to claim 1, characterized in that: The top operating pressure of the first dephenolization tower is 1 kPaA to 20 kPaA.

3. The method according to claim 1, characterized in that The top operating pressure of the second dephenolization tower is 20 kPaA to 50 kPaA.

4. The method according to claim 1, characterized in that: The temperature of the top steam of the second dephenolization tower is 130°C to 160°C.

5. The method according to claim 1 or 2, characterized in that: The process parameters of the first dephenolization tower include: a bottom temperature of 110° C. to 130° C., a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

6. The method according to claim 1 or 3, characterized in that: The process parameters of the second dephenolization tower include: a bottom temperature of 210° C. to 230° C., a theoretical plate number of 15 to 50, and a reflux ratio of 0.1 to 3.

7. The method according to claim 1, characterized in that The decoking is processed by a decoking tower, and the process parameters of the decoking tower include: a tower top operating pressure of 0.5kPaA to 8kPaA, a tower bottom temperature of 210°C to 260°C, a theoretical tower plate number of 5 to 40, and a reflux ratio of 0.5 to 4.

8. The method according to claim 1, characterized in that: The dehydration is processed by a dehydration tower, and the process parameters of the dehydration tower include: a tower top operating pressure of 2kPaA-50kPaA, a tower bottom temperature of 150°C-180°C, a theoretical plate number of 10-40, and a reflux ratio of 0.5-4.

9. The method according to claim 1, characterized in that: The second material is separated to obtain catechol and hydroquinone, comprising: The second material is subjected to a first separation through a catechol tower to obtain catechol and a third material; The third material is subjected to a second separation through a hydroquinone tower to obtain hydroquinone; wherein, The process parameters of the catechol tower include: top operating pressure 2kPaA-25kPaA, bottom temperature 200°C-230°C, theoretical plate number 15-50, reflux ratio 0.5-4; The process parameters of the hydroquinone tower include: a tower top operating pressure of 0.5 kPaA to 12 kPaA, a tower bottom temperature of 210° C. to 260° C., a theoretical plate number of 4 to 30, and a reflux ratio of 0.1 to 3.

10. The method according to claim 1, characterized in that The chemical components of the phenol hydroxylation reaction liquid include: water, phenol, catechol, hydroquinone and tar; wherein, by mass fraction, The content of water is 10% to 55%, the content of phenol is 25% to 70%, the content of catechol is 5% to 25%, the content of hydroquinone is 7% to 25%, and the content of tar is 1% to 5%.

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