A method for removing naphthalene from crude phenol

Abstract

The application belongs to the technical field of crude phenol refining, and particularly relates to a method for removing naphthalene from crude phenol. The method for removing naphthalene from crude phenol comprises the following steps: removing naphthalene in crude phenol by azeotropic rectification of water and crude phenol; the theoretical plate number of the azeotropic rectification tower is 30-60, the feeding position of the crude phenol is the middle part of the azeotropic rectification tower, and the feeding position of the water is the top of the azeotropic rectification tower. The method for removing naphthalene from crude phenol can efficiently remove naphthalene in crude phenol, so that the naphthalene content in crude phenol is less than 0.5%, which meets the industrial standard YBT 5079-2012 that the neutral oil content in crude phenol is less than 0.8%. The method for removing naphthalene from crude phenol has simple process, low equipment investment, and low operation cost, can simultaneously realize dehydration, naphthalene removal, and solvent recovery, and has less crude phenol loss.

Description

Technical Field

[0001] This application belongs to the field of crude phenol refining technology, specifically relating to a method for removing naphthalene from crude phenol. Background Technology

[0002] Naphthalene is the most difficult neutral oil to remove from crude phenol. Whether it's crude phenol extracted from coal tar phenol oil fractions using the alkaline washing method or crude phenol recovered from coal gasification wastewater through solvent extraction, it may contain a certain amount of naphthalene. Naphthalene is a typical neutral oil that forms azeotropes with various components in crude phenol, severely affecting subsequent processing and the quality of phenolic products. Therefore, when its content in crude phenol exceeds 0.8%, it needs to be removed.

[0003] In actual production, the naphthalene content in crude phenol feedstock typically ranges from 1.0% to 8.0%. Existing technologies for removing naphthalene from crude phenol feedstock involve accumulating it in the o-cresol and 2,6-xylenol fractions. Once a certain concentration is reached, it is removed along with the o-cresol and 2,6-xylenol. This method results in the loss of significant amounts of high-value-added products such as o-cresol and 2,6-xylenol, thus reducing economic efficiency. Existing technologies also employ steam stripping to remove neutral oil entrained in crude phenol during solvent extraction. Furthermore, existing technologies propose utilizing the low-boiling-point azeotrope formed by naphthalene and ethanolamine, where the azeotropic point is lower than that of phenol. Ethanolamine is used to extract the naphthalene azeotrope from the crude phenol, and the remaining extract is then separated by distillation to obtain a phenol product with a lower naphthalene content.

[0004] Existing technologies primarily target the removal of residual neutral oil (comprising 3.0-11.0% of the total extracted material) from crude phenol after extraction from direct coal liquefaction oil or low-temperature coal tar using steam stripping. However, naphthalene is a polycyclic aromatic hydrocarbon, mainly found in high-temperature coal tar, and its content in the aforementioned neutral oils is generally low, as both direct coal liquefaction oil and low-temperature coal tar inherently contain low levels of naphthalene. Industry experience shows that, regardless of solvent extraction or azeotropic distillation, naphthalene is the most difficult yet essential neutral oil component to remove from crude phenol. Because this method is not specifically designed for naphthalene removal from crude phenol, it presents several problems. For example, the use of pressure in this method is unreasonable, leading to high separation difficulty, low yield of crude phenol product, and poor naphthalene removal efficiency. As is well known, under pressure, the boiling point difference between phenols and water decreases. The azeotrope emerging from the top of the stripping tower, besides neutral oil, contains a significant amount of phenols, directly impacting the yield of crude phenol. For example, in Example 2 of the existing patent CN201110102049, the crude phenol extraction yield is 90%, with neutral oil accounting for 3.5%, corresponding to a total crude phenol yield of 82%. This means that the crude phenol loss during steam stripping (operating pressure 2.0-3.0 bar) reaches 8%, a very serious loss. Introducing steam from the bottom of the stripping tower is also clearly unreasonable, as the bottom material inevitably contains water, requiring dehydration in a separate atmospheric pressure tower, significantly increasing equipment investment and operating costs. Adding water to the stripping tower in the form of steam is also unreasonable, as steam costs are very high, reaching 200-500 yuan / ton, which is not cost-effective and is less efficient than direct water stripping. Furthermore, the technology has not yet solved some crucial issues, such as reflux ratio, water addition ratio, and feed location. Modern purification and refining processes for crude phenols require energy conservation and cost reduction to achieve better returns. Therefore, optimizing process conditions is essential to gain user acceptance of advanced processing technologies and enable industrial application.

[0005] Due to the complexity, high energy consumption, large investment, and limited effectiveness of existing technologies for removing naphthalene from crude phenol, they have not yet gained acceptance from users and the market, and have not been industrialized. Therefore, removing naphthalene and other key neutral oils from crude phenol is a major technical challenge that urgently needs to be solved in modern crude phenol processing. Summary of the Invention

[0006] This application provides a method for removing naphthalene from crude phenol, aiming to solve the problems of complex processes, high costs, and low efficiency in existing methods for removing naphthalene from crude phenol.

[0007] This application provides a method for removing naphthalene from crude phenol, comprising the following steps: using an azeotropic distillation column to perform azeotropic distillation on water and crude phenol to remove naphthalene from the crude phenol;

[0008] The azeotropic distillation column has 30-60 theoretical plates. The crude phenol is fed into the middle of the azeotropic distillation column, and the water is fed into the top of the azeotropic distillation column.

[0009] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the water feed location is 5-10 trays down from the top of the azeotropic distillation column.

[0010] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, crude phenol with naphthalene removed is collected from the bottom of the azeotropic distillation column, and a naphthalene-containing mixture is collected from the top of the azeotropic distillation column.

[0011] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the mass ratio of water to crude phenol is (0.6-1.0):1.

[0012] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the pressure of the azeotropic distillation is absolute 20-40 kPa, and the reflux ratio of the azeotropic distillation is 3-6.

[0013] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the method further includes mixing a naphthalene-containing mixture with an extractant, separating the layers, separating the naphthalene-free water from the mixture, and obtaining a mixture containing naphthalene and the extractant.

[0014] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the extractant includes toluene and / or xylene.

[0015] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the mass ratio of the extractant to the water in the naphthalene-containing mixture is (0.1-0.5):1.

[0016] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the method further includes subjecting a mixture containing naphthalene and an extractant to a second distillation process to recover the extractant.

[0017] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the second distillation is carried out in a solvent recovery tower.

[0018] According to some embodiments of the method for removing naphthalene from crude phenol as described in this application, the pressure of the second distillation is 20-40 kPa, and the reflux ratio of the second distillation is 0.5-1.0.

[0019] The beneficial effects of this application include: the method for removing naphthalene from crude phenol described in this application can efficiently remove naphthalene from crude phenol, so that the naphthalene content in crude phenol reaches less than 0.5%, which meets the industry standard YBT 5079-2012 that the neutral oil content in crude phenol is less than 0.8%.

[0020] The method for removing naphthalene from crude phenol described in this application is simple, requires little equipment investment, and has low operating costs. It can simultaneously achieve dehydration, naphthalene removal, and solvent recovery with minimal loss of crude phenol. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0023] This application provides a method for removing naphthalene from crude phenol, comprising the following steps: using an azeotropic distillation column to perform azeotropic distillation on water and crude phenol to remove naphthalene from the crude phenol;

[0024] The azeotropic distillation column has 30-60 theoretical plates. The crude phenol is fed into the middle of the azeotropic distillation column, and the water is fed into the top of the azeotropic distillation column.

[0025] In some embodiments of this application, the water feed location is 5-10 plates down from the top of the azeotropic distillation column.

[0026] In some embodiments of this application, crude phenol with naphthalene removed is collected from the bottom of the azeotropic distillation column, and a naphthalene-containing mixture is collected from the top of the azeotropic distillation column.

[0027] In some embodiments of this application, the mass ratio of water to crude phenol is (0.6-1.0):1, for example, 0.6:1, 0.8:1, 0.9:1, 1.0:1, etc.

[0028] In some embodiments of this application, the pressure of the azeotropic distillation is absolute pressure of 20-40 kPa, such as 20 kPa, 22 kPa, 25 kPa, 30 kPa, 36 kPa, 40 kPa, etc., and the reflux ratio of the azeotropic distillation is 3-6, such as 3, 4, 5, 6, etc.

[0029] In some embodiments of this application, the method further includes mixing the naphthalene-containing mixture and the extractant, separating the layers, separating the water in the mixture that does not contain naphthalene, and obtaining a mixture containing naphthalene and the extractant.

[0030] In some embodiments of this application, the extractant includes toluene and / or xylene.

[0031] In some embodiments of this application, the mass ratio of the extractant to the water in the naphthalene-containing mixture is (0.1-0.5):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.5:1, etc.

[0032] In some embodiments of this application, the method further includes a second distillation treatment of the mixture containing naphthalene and the extractant to recover the extractant.

[0033] In some embodiments of this application, the second distillation is carried out in a solvent recovery tower.

[0034] In some embodiments of this application, the pressure of the second distillation is 20-40 kPa, such as 20 kPa, 25 kPa, 30 kPa, 36 kPa, 40 kPa, etc., and the reflux ratio of the second distillation is 0.5-1.0, such as 0.5, 0.8, 1.0, etc.

[0035] The technical solution of this application will be further described below with reference to specific embodiments.

[0036] Example 1

[0037] The crude phenol raw material used in Example 1 is commercially available high-temperature anhydrous crude phenol, and its composition is shown in Table 1 below.

[0038] The method for removing naphthalene from crude phenol as described in Example 1 includes the following steps:

[0039] The azeotropic distillation column (hereinafter referred to as the azeotropic column) has a diameter of 32 mm and a theoretical number of 30 plates (actually using 2 meters of θ-ring packing with a diameter of 3 mm). The crude phenol feed rate is 300 g / h, and the feed position is the 15th plate in the middle of the azeotropic distillation column. The water feed rate is 300 g / h (i.e., the water ratio is 1.0 times the mass of crude phenol), and the feed position is the 5th plate downward from the top of the azeotropic distillation column. The operating pressure of the azeotropic distillation column is absolute pressure 20 kPa, and the reflux ratio is 3. The product exiting the bottom of the azeotropic column is qualified crude phenol with a naphthalene content of 0.49% and a water content of 0.05%, and the crude phenol yield is 94.52% (the approximate calculation method for the yield is shown below). The azeotropic column top product is a naphthalene-containing mixture with a naphthalene content of 49.53% and a total phenol content of 50.47% (excluding water content). Toluene is added to the naphthalene-containing mixture at a rate of 0.1 times the mass of water in the mixture. After mixing and stirring in a mixing tank and settling, the lower layer is naphthalene-free water, which is recycled to the azeotropic column. The upper layer is an organic phase containing naphthalene and trace amounts of crude phenol. This organic phase is added to a 20-plate solvent recovery column for a second distillation process. The reflux ratio for the second distillation process is 1.0, and the operating pressure is 20 kPa. After distillation, naphthalene-free solvent is obtained for future use.

[0040] Crude phenol yield = 100% - Naphthalene from the top of the column * Phenol content at the top of the column / Naphthalene content at the top of the column / Total phenol content in the feed;

[0041] The crude phenol yield of the method described in Example 1 = 100% - (300 * 5.10%) * 50.47 / 49.53 / (300 * (1 - 5.10%)) = 94.52%

[0042] Table 1. Composition of the crude phenols described in Example 1

[0043]

[0044]

[0045] Example 2

[0046] The crude phenol raw material used in Example 2 is the same as that in Example 1.

[0047] The method for removing naphthalene from crude phenol as described in Example 2 includes the following steps:

[0048] The azeotropic distillation column has a diameter of 32 mm and a theoretical number of 60 plates (actually using 4 meters of 3 mm θ-ring packing). The crude phenol feed rate is 300 g / h, fed onto the 30th plate of the azeotropic distillation column. The water feed rate is 180 g / h (the water ratio is 0.6 times the mass of crude phenol), fed onto the 10th plate downwards from the top of the column. The operating pressure of the azeotropic column is absolute 40 kPa, and the reflux ratio is 6. The product exiting the bottom of the azeotropic column is qualified crude phenol with a naphthalene content of 0.41% and a water content of 0.04%, with a crude phenol yield of 95.68%. The azeotropic tower top product is a naphthalene-containing mixture with a naphthalene content of 55.45% and a total phenol content of 44.55% (excluding water content). Mixed xylene (from natural components in the coking industry) is added to the naphthalene-containing mixture at a ratio of 0.5 times the mass of water in the mixture. After mixing and stirring in a mixing tank and settling, the lower layer is naphthalene-free water, which is recycled to the azeotropic tower. The upper layer is an organic phase containing naphthalene and trace amounts of crude phenol. This organic phase is added to a 40-plate solvent recovery tower for a second distillation treatment. The reflux ratio for the second distillation treatment is 0.5, and the operating pressure is 40 kPa. After distillation, naphthalene-free solvent is obtained for future use.

[0049] Crude phenol yield = 100% - Naphthalene from the top of the column * Phenol content at the top of the column / Naphthalene content at the top of the column / Total phenol content in the feed

[0050] The crude phenol yield of the method described in Example 2 is 100% - (300 * 5.10%) * 44.55 / 55.45 / (300 * (1 - 5.10%)) = 95.68%.

[0051] Example 3

[0052] The method for removing naphthalene from crude phenol as described in Example 3 includes the following steps:

[0053] The azeotropic distillation column has a diameter of 32 mm and a theoretical number of 60 plates (actually using 4 meters of 3 mm θ-ring packing). The crude phenol feed rate is 300 g / h, fed onto the 30th plate of the azeotropic distillation column. The water feed rate is 240 g / h (the water ratio is 0.8 times the mass of crude phenol), fed onto the 10th plate downwards from the top of the column. The operating pressure of the azeotropic column is absolute 30 kPa, and the reflux ratio is 5. The product exiting the bottom of the azeotropic column is qualified crude phenol with a naphthalene content of 0.46% and a water content of 0.06%, with a crude phenol yield of 94.41%. The azeotropic tower top product is a naphthalene-containing mixture with a naphthalene content of 61.01% and a total phenol content of 38.99% (excluding water content). Mixed xylene (from natural components in the coking industry) is added to the naphthalene-containing mixture at a ratio of 0.3 times the mass of water in the mixture. After mixing and stirring in a mixing tank and settling, the lower layer is naphthalene-free water, which is recycled to the azeotropic tower. The upper layer is an organic phase containing naphthalene and trace amounts of crude phenol. This organic phase is added to a 40-plate solvent recovery tower for a second distillation process. The reflux ratio for the second distillation process is 0.7, and the operating pressure is 30 kPa. After distillation, naphthalene-free solvent is obtained for future use.

[0054] The raw material composition of the coarse powder described in Example 3 is shown in Table 2.

[0055] Table 2

[0056] Element content / % phenol 48.89 o-cresol 8.77 m-cresol 9.04 p-Cresol 7.39 2,3-Xylene 1.26 2,4-Xylene 2.57 2,5-Xylene 2.50 2,6-Xylenol 3.29 3,4-Xylenol 0.38 3,5-Xylenol 4.93 o-Ethylphenol 2.93 Naphthalene 8.05 sum 100.00

[0057] The crude phenol yield of the method described in Example 3 is 100% - (300 * 8.05%) * 38.99 / 61.01 / (300 * (1 - 8.05%)) = 94.41%.

[0058] Comparative Example 1

[0059] The only difference between the method for removing naphthalene from crude phenol described in Comparative Example 1 and Example 3 is that the water in the method for removing naphthalene from crude phenol described in Comparative Example 1 is added by steam from the bottom of the tower.

[0060] Except for the addition of steam from the bottom of the column, the raw material containing naphthalene and the operating conditions were exactly the same as in Example 3. As a result, the crude phenol from the bottom of the azeotropic column contained 1.08% naphthalene and 1.25% water. The top of the azeotropic column was a mixture of 39.53% naphthalene and 60.47% total phenol (excluding water content). The crude phenol yield was 86.61%. This shows that the operating method in the other party's document is far inferior to the method of this application in terms of naphthalene removal, dehydration, and crude phenol yield.

[0061] Crude phenol yield = 100% - Naphthalene from the top of the column * Phenol content at the top of the column / Naphthalene content at the top of the column / Total phenol content in the feed

[0062] =100% - (300 * 8.05%) * 60.47 / 39.53 / (300 * (1 - 8.05%)) = 86.61%.

[0063] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for removing naphthalene from crude phenol, characterized in that, Includes the following steps: Azeotropic distillation column is used to remove naphthalene from crude phenol by azeotropic distillation of water and crude phenol; the mass ratio of water to crude phenol is (0.6-1.0):

1. The azeotropic distillation column has 30-60 theoretical plates, the azeotropic distillation pressure is absolute 20-40 kPa, the crude phenol is fed into the middle of the azeotropic distillation column, and the water is fed into the top of the azeotropic distillation column.

2. The method for removing naphthalene from crude phenol according to claim 1, characterized in that, The water feed point is 5-10 trays down from the top of the azeotropic distillation column; And / or, crude phenol with naphthalene removed is collected from the bottom of the azeotropic distillation column, and a naphthalene-containing mixture is collected from the top of the azeotropic distillation column.

3. The method for removing naphthalene from crude phenol according to claim 1, characterized in that, The reflux ratio of the azeotropic distillation is 3-6.

4. The method for removing naphthalene from crude phenol according to claim 2, characterized in that, The method further includes mixing the naphthalene-containing mixture and the extractant, separating the layers, separating the water in the mixture that does not contain naphthalene, and obtaining a mixture containing naphthalene and the extractant.

5. The method for removing naphthalene from crude phenol according to claim 4, characterized in that, The extractant includes toluene and / or xylene.

6. The method for removing naphthalene from crude phenol according to claim 4, characterized in that, The mass ratio of the extractant to the water in the naphthalene-containing mixture is (0.1-0.5):

1.

7. The method for removing naphthalene from crude phenol according to claim 4, characterized in that, The method further includes a second distillation process to recover the extractant from the mixture containing naphthalene and the extractant.

8. The method for removing naphthalene from crude phenol according to claim 7, characterized in that, The second distillation is carried out in a solvent recovery tower.

9. The method for removing naphthalene from crude phenol according to claim 8, characterized in that, The pressure of the second distillation is 20-40 kPa, and the reflux ratio of the second distillation is 0.5-1.0.

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