An apparatus and method for recovering α-methylstyrene by pyrolysis of phenol tar.

Abstract

This invention relates to an apparatus and method for recovering α-methylstyrene from phenol tar through cracking. The apparatus includes a cracking reaction unit for cracking the phenol tar feedstock, a crude product condenser connected to the gas phase outlet of the cracking reaction unit via its feed inlet, a negative pressure de-heavy distillation column connected to the liquid phase outlet of the crude product condenser via its feed inlet, and a negative pressure distillation AMS product column connected to the top outlet of the negative pressure de-heavy distillation column. α-methylstyrene is collected from the top of the negative pressure distillation AMS product column. Compared with existing technologies, this invention, on the one hand, employs a continuous direct-heat cracking method to control the reaction residence time, increasing the reaction directionality and the recovery rate of the target product; on the other hand, it uses a negative pressure distillation method, which avoids further cracking of heavy components and allows for the separation of cumene and AMS in two columns, resulting in a simple process flow.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to an apparatus and method for recovering α-methylstyrene by cracking phenolic tar. Background Technology

[0002] Phenolic tar is a byproduct of the reaction between cumene and acetone, produced from cumene. It is the distillation residue after separating phenol and acetone from the reaction products and is classified as hazardous waste. The approximate composition of phenol tar is as follows: phenol 19.6%, acetophenone 12%, cumylphenol 21.6%, and other heavy components 48.8%. Compositionally, phenol tar contains a significant amount of fine chemicals with high application value. However, current market practices for treating phenol tar do not maximize its value. Many phenol plants incinerate phenol tar, which not only causes environmental pollution but also wastes resources. Therefore, methods to recover useful products such as cumene, phenol, acetophenone, and α-methylstyrene from phenol tar to the greatest extent possible, while reducing the amount of tar removed through combustion, would be of great value.

[0003] Document CN1154399 discloses a method for treating phenol tar. Phenol tar is subjected to controlled thermal cracking under polyphosphoric acid conditions to recover valuable products. The phenol tar is added to a cylindrical reactor for thermal cracking, and the temperature of the reactor bottom is heated to 200–360°C. The reactor pressure is maintained at 0.1–5 atm. In the presence of 0.1–1.0% (preferably 0.1–0.2%) of phosphoric acid preheated to 50–180°C, the cracked tar is dehydrated by the added phosphoric acid and polymerized into a non-volatile polyphosphoric acid analog. Bisphenol A tar can optionally be mixed with the tar for cracking under these conditions to improve product yield. A comparative analysis of the literature shows that this process uses catalytic cracking to obtain useful and recoverable components. However, because the phosphoric acid catalyst readily polymerizes to produce solids, the heavy components at the bottom after catalytic cracking tend to coke, affecting equipment operation. The patent does not describe a method for recovering the useful components.

[0004] Document CN1137033 discloses the co-cracking of tar from bisphenol A and phenol processes. It designs a processing technology for a mixture of tar produced during the manufacture of phenol and bisphenol. The method involves heating the bottom liquid from the bisphenol A process and the phenol tar from the cumene-to-phenol process at a mass ratio of 1:(1-10) in a distillation column-type thermal cracking reactor at 290–360°C. The process involves feeding the material into the middle of the column and removing the valuable product from the top. A comparative analysis of this document shows that this process targets phenol tar and bisphenol A tar, or a mixture of both in any proportion, obtained from the cumene-to-phenol process. It uses thermal cracking to obtain reusable valuable products (phenol, α-methylstyrene, and cumene), not phenol tar from the cumene process, and the patent does not mention any recycling methods or equipment. Summary of the Invention

[0005] The purpose of this invention is to address the problem of difficult treatment of phenol tar generated in phenol production plants using cumene as a raw material, and to provide an apparatus and method for cracking phenol tar to recover valuable α-methylstyrene.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] An apparatus for recovering α-methylstyrene by phenol tar cracking, comprising:

[0008] The pyrolysis reaction unit is used for the pyrolysis reaction of phenolic tar feedstock;

[0009] The crude product condenser has its inlet connected to the gas phase outlet of the pyrolysis reaction unit and is used to condense the crude product into a liquid phase.

[0010] A negative pressure de-heavy distillation column, the feed inlet of which is connected to the liquid phase outlet of the crude product condenser, wherein the de-heavy distillation liquid phase is collected from the top of the column; and

[0011] The negative pressure distillation AMS product column has its inlet connected to the outlet of the negative pressure de-weighting distillation column, and the product α-methylstyrene is collected from the top of the negative pressure distillation AMS product column.

[0012] Furthermore, the pyrolysis reaction unit includes a pyrolysis reactor, and an external circulation pump, a heater, and a gas-liquid separator connected in sequence to the liquid phase outlet of the pyrolysis reactor.

[0013] The gas phase outlet of the gas-liquid separator is connected to the feed inlet of the crude product condenser, and the liquid phase outlet is connected to the pyrolysis reactor.

[0014] Furthermore, the connecting pipeline between the external circulation pump and the heater is also provided with a pyrolysis liquid phase outlet.

[0015] Furthermore, along the material flow direction, a crude product collection tank and a de-weighting tower feed pump are sequentially provided between the crude product condenser and the negative pressure de-weighting distillation tower;

[0016] The crude product collection tank is provided with a crude product discharge port.

[0017] Furthermore, a heavy component recovery pump is also provided between the bottom outlet of the negative pressure de-heavy distillation column and the crude product condenser. After the bottom outlet of the negative pressure de-heavy distillation column exchanges heat with the gas phase outlet of the cracking reaction unit through the crude product condenser, it is returned to the cracking reaction unit.

[0018] Furthermore, the negative pressure de-weighting distillation column is sequentially connected to a de-weighting column top condenser and a de-weighting column top collection tank at its top outlet.

[0019] The outlet of the top collection tank of the deweight removal tower is connected to the negative pressure distillation AMS product tower.

[0020] Furthermore, an AMS product column feed pump is also provided between the top collection tank of the deweighting tower and the negative pressure distillation AMS product column.

[0021] A method for recovering α-methylstyrene by pyrolysis of phenol tar includes employing the apparatus described above, and further includes:

[0022] The phenol tar feedstock is sent to the cracking reaction unit. The gaseous output is condensed by the crude product condenser and then sent to the negative pressure de-gravity distillation column. The gaseous output from the top of the column is condensed and sent to the negative pressure distillation AMS product column. The product α-methylstyrene is collected from the bottom of the column.

[0023] Furthermore, the method for recovering α-methylstyrene by phenol tar cracking includes:

[0024] The phenol tar feedstock is sent to the cracking reactor. The liquid phase output is divided into two parts after passing through the external circulation pump. One part is collected, and the other part is heated by the heater and enters the gas-liquid separator. The liquid phase output of the gas-liquid separator is returned to the cracking reactor. The gas phase output is mixed with the gas phase output of the cracking reactor and then condensed by the crude product condenser before entering the crude product collection tank.

[0025] The liquid phase discharge from the crude product collection tank is pumped to the negative pressure de-heavy distillation column via the feed pump of the de-heavy column. The liquid phase discharge from the bottom of the column is pumped to the crude product condenser via the heavy component recovery pump to exchange heat with the mixed gas phase discharge. The discharge is then returned to the cracking reactor. The top discharge from the negative pressure de-heavy distillation column is condensed in the top condenser of the de-heavy column and enters the top collection tank of the de-heavy column. It is then pumped to the negative pressure distillation AMS product column via the feed pump of the AMS product column. The product α-methylstyrene is collected from the top of the column.

[0026] Furthermore, the liquid phase discharge from the pyrolysis reactor is heated by an external circulation pump and a heater, which can control the residence time of the material in the pyrolysis reaction unit to be 1-6 hours.

[0027] Furthermore, the operating pressure of the negative pressure deweighting distillation column is 10-90 kPa (preferably 40-60 kPa), and the operating pressure of the negative pressure distillation AMS product column is 1-50 kPa (preferably 5-20 kPa). All operating pressures in this invention refer to absolute pressure.

[0028] Furthermore, the mass content of α-methylstyrene in the bottom product of the negative pressure distillation AMS product column is not less than 99.0%.

[0029] Compared with the prior art, the present invention has the following characteristics:

[0030] 1) Compared with the phenol tar cracking scheme, the present invention adopts a negative pressure distillation method, which can avoid the further cracking of heavy components and can separate cumene and AMS in two towers, and the process flow is simple.

[0031] 2) Compared with the conventional direct thermal pyrolysis method, the present invention adopts a continuous direct thermal pyrolysis method to control the reaction residence time, thereby increasing the reaction orientation and increasing the recovery rate of the target product. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the apparatus for recovering α-methylstyrene from phenolic tar through cracking in Example 1;

[0033] Explanation of markings in the diagram:

[0034] 1-Crack reactor, 2-External circulation pump, 3-Heater, 4-Gas-liquid separator, 5-Crude product condenser, 6-Crude product collection tank, 7-De-heavy product tower feed pump, 8-Negative pressure de-heavy product distillation tower, 9-Heavy component recovery pump, 10-De-heavy product tower top condenser, 11-De-heavy product tower top collection tank, 12-AMS product tower feed pump, 13-Negative pressure distillation AMS product tower. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] Example 1:

[0037] like Figure 1 The apparatus shown is for the cracking and recovery of α-methylstyrene from phenol tar, including a cracking reaction unit, a crude product condenser 5, a negative pressure de-gravity distillation column 8, and a negative pressure distillation AMS product column 13.

[0038] The pyrolysis reaction unit includes a pyrolysis reactor 1, and an external circulation pump 2, a heater 3, and a gas-liquid separator 4, which are sequentially connected to the liquid phase outlet of the pyrolysis reactor 1. The gas phase outlets of the pyrolysis reactor 1 and the gas-liquid separator 4 are connected to the inlet of the crude product condenser 5, and the liquid phase outlet of the gas-liquid separator 4 is connected to the pyrolysis reactor 1. In addition, a pyrolysis liquid phase outlet is provided on the connecting pipeline between the external circulation pump 2 and the heater 3.

[0039] The pyrolysis reaction unit is used to pyrolyze phenolic tar feedstock. After the liquid phase output of pyrolysis reactor 1 is pumped out by external circulation pump 2, part of it is collected and the other part is partially vaporized by heater 3 before entering gas-liquid separator 4. The liquid phase output of gas-liquid separator 4 is returned to pyrolysis reactor 1 for pyrolysis reaction cycle, while the gas phase output is mixed with the gas phase output of pyrolysis reactor 1 and enters crude product condenser 5.

[0040] The crude product condenser 5 is used to condense the pyrolysis gas phase output to obtain a liquid crude product, and a crude product collection tank 6 and a de-heavy distillation column feed pump 7 are sequentially installed at the outlet. Part of the liquid phase material in the crude product collection tank 6 is collected through the crude product outlet, and the other part is sent to the negative pressure de-heavy distillation column 8 through the de-heavy distillation column feed pump 7.

[0041] The bottom outlet of the negative pressure de-heavy distillation column 8 is connected to a heavy component recovery pump 9. The heavy component recovery pump 9 sends the bottom product to the crude product condenser 5, where it exchanges heat with the vapor phase product from the cracking reaction unit, and then returns to the cracking reactor 1 for cracking. The top outlet of the negative pressure de-heavy distillation column 8 is sequentially connected to a de-heavy distillation column top condenser 10, a de-heavy distillation column top collection tank 11, and an AMS product column feed pump. The de-heavy distillation liquid phase collected at the top of the column passes sequentially through the de-heavy distillation column top condenser 10, the de-heavy distillation column top collection tank 11, and the AMS product column feed pump before being sent to the negative pressure distillation AMS product column 13. High-purity α-methylstyrene is collected at the top of the negative pressure distillation AMS product column 13.

[0042] Example 2:

[0043] A method for recovering α-methylstyrene by pyrolysis of phenolic tar, using the apparatus described in Example 1, specifically includes:

[0044] Phenolic tar from a cumene-to-phenol-acetone production unit is used as feedstock at a flow rate of 100 kg / h. Its mass composition is 19.9% ​​phenol, 10.3% acetophenone, 0.1% dimethylphenol, 21.7% cumylphenol, and 48.0% other heavy components. The phenolic tar feedstock enters cracking reactor 1 (φ300×1000mm), with a controlled pressure of 300 kPa and a temperature of 320℃. The material at the bottom of cracking reactor 1 is collected by external circulation pump 2 at a rate of 20 kg / h. A portion of this material is heated by heater 3 and then sent to gas-liquid separator 4, with the pressure controlled at 300 kPa. The gaseous material from gas-liquid separator 4 and cracking reactor 1 are condensed to 50℃ by crude product condenser 5 before entering crude product collection tank 6 (at ambient pressure and temperature).

[0045] Part of the material in the crude product collection tank 6 is collected, and the other part is transported to the negative pressure de-heavy distillation column 8 via the de-heavy column feed pump 7, with a controlled pressure of 10 kPa. The bottom material is then pumped by the heavy component recovery pump 9 and, after heat exchange at the crude product condenser 5, enters the cracking reactor 1. The top material is condensed by the de-heavy column top condenser 10 and enters the de-heavy column top collection tank 11, and then transported by the AMS product column feed pump 12 to the negative pressure distillation AMS product column 13. The top pressure of the negative pressure distillation AMS product column 13 is 10 kPa, and AMS product is obtained at the top of the column at a flow rate of 30 kg / h with a purity of 99.4%. The components obtained from the bottom of the column are returned to the main unit for the production of phenol and acetone from cumene for further distillation and purification of cumene and phenol.

[0046] Example 3:

[0047] A method for recovering α-methylstyrene by pyrolysis of phenolic tar, differing from Example 2 only in that:

[0048] The reaction temperature of the cracking reactor 1 is 350℃, the operating pressure is 150kPa, and the top discharge flow rate of the negative pressure distillation AMS product column 13 is 35kg / h. The rest is the same as in Example 2.

[0049] The purity of the obtained AMS product was 99.2%.

[0050] Example 4:

[0051] A method for recovering α-methylstyrene by pyrolysis of phenolic tar, differing from Example 2 only in that:

[0052] The reaction temperature of the pyrolysis reactor 1 is 350℃, the operating pressure is 250kPa, and the top discharge flow rate of the negative pressure distillation AMS product column 13 is 33kg / h. The rest is the same as in Example 2.

[0053] The purity of the obtained AMS product was 99.3%.

[0054] In the phenol recovery method of the present invention, phenol tar is purified by high-temperature cracking and distillation to obtain α-methylstyrene product, wherein the cracking reaction employs external circulation heating to control the residence time. The apparatus and method for recovering α-methylstyrene from phenol tar by cracking of the present invention can control the residence time of the tar cracking reaction, reduce the generation of by-products, and improve the recovery rate of α-methylstyrene.

[0055] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A process for the cleavage of phenol tar to recover α-methylstyrene, characterized in that, The device used comprises a cracking reaction unit for carrying out a cracking reaction on a phenol tar raw material; a crude product condenser (5) having a feed inlet connected to the gas phase outlet of the cracking reaction unit, for condensing to obtain a liquid phase crude product; a negative pressure heavy component removal rectifying tower (8) having a feed inlet connected to the liquid phase outlet of the crude product condenser (5), the negative pressure heavy component removal rectifying tower (8) being provided with a heavy component removal rectifying liquid phase outlet at the top; a negative pressure rectifying AMS product tower (13) having a feed inlet connected to the top outlet of the negative pressure heavy component removal rectifying tower (8), the negative pressure rectifying AMS product tower (13) being provided with a product α-methylstyrene outlet at the top. The method comprises: feeding the phenol tar raw material to a cracking reactor (1), the liquid phase outlet being divided into two parts after passing through an external circulation pump (2), one part being taken out, and the other part being heated by a heater (3) and then entering a gas-liquid separator (4), the liquid phase outlet of the gas-liquid separator (4) being returned to the cracking reactor (1), the gas phase outlet being mixed with the gas phase outlet of the cracking reactor (1) and then condensed by a crude product condenser (5), and then entering a crude product collection tank (6); the liquid phase outlet of the crude product collection tank (6) being sent to the negative pressure heavy component removal rectifying tower (8) by a heavy component removal tower feed pump (7), the bottom liquid phase outlet being sent to the crude product condenser (5) by a heavy component recovery pump (9) to exchange heat with the mixed gas phase outlet, and then being returned to the cracking reactor (1); the top outlet of the negative pressure heavy component removal rectifying tower (8) being condensed by a heavy component removal tower top condenser (10) and then entering a heavy component removal tower top collection tank (11), and then being sent to the negative pressure rectifying AMS product tower (13) by an AMS product tower feed pump (12), and the product α-methylstyrene being taken out at the top; the liquid phase outlet of the cracking reactor being heated by an external circulation pump and a heater, and the residence time of the material in the cracking reaction unit being controlled to be 1-6h; the operating pressure of the negative pressure heavy component removal rectifying tower (8) being 10-90kPa, and the operating pressure of the negative pressure rectifying AMS product tower (13) being 1-50kPa.

2. The method for recovering a-methylstyrene by pyrolysis of phenol tar according to claim 1, characterized in that, The cracking reaction unit comprises a cracking reactor (1), and an external circulation pump (2), a heater (3), and a gas-liquid separator (4) connected to the liquid phase outlet of the cracking reactor (1) in sequence. The gas phase outlet of the gas-liquid separator (4) is connected to the feed inlet of the crude product condenser (5), and the liquid phase outlet is connected to the cracking reactor (1).

3. The method for recovering a-methylstyrene by pyrolysis of phenol tar according to claim 2, characterized in that, A cracking liquid phase outlet is further provided on the connecting pipeline between the external circulation pump (2) and the heater (3).

4. The method for recovering a-methylstyrene by pyrolysis of phenol tar according to claim 1, characterized in that, In the direction of the material flow, a crude product collection tank (6), a heavy component removal tower feed pump (7) are further provided in sequence between the crude product condenser (5) and the negative pressure heavy component removal rectifying tower (8). A crude product outlet is provided on the crude product collection tank (6).

5. The method of recovering a-methylstyrene from a creosote tar according to claim 1, wherein A heavy component recovery pump (9) is further provided between the bottom outlet of the negative pressure heavy component removal rectifying tower (8) and the crude product condenser (5), and the bottom outlet of the negative pressure heavy component removal rectifying tower (8) is returned to the cracking reaction unit after exchanging heat with the gas phase outlet of the cracking reaction unit by the crude product condenser (5).

6. The method of recovering a-methylstyrene from a creosote tar according to claim 1, wherein The top outlet of the negative pressure heavy-removing rectifying tower (8) is connected with a heavy-removing tower top condenser (10) and a heavy-removing tower top collecting tank (11) in sequence. The outlet of the heavy-removing tower top collecting tank (11) is connected with a negative pressure rectifying AMS product tower (13).

7. The process for recovery of a-methylstyrene by cleavage of phenol tar according to claim 6, characterized in that, An AMS product tower feeding pump (12) is further arranged between the heavy-removing tower top collecting tank (11) and the negative pressure rectifying AMS product tower (13).

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