Circulating chlorobenzene rectification device in production process of 2-alkylanthraquinone

Abstract

The utility model discloses a circulating chlorobenzene rectifying device in a 2-alkylanthraquinone production process, which is characterized in that a rectifying kettle is provided with a stirring paddle and a peripheral wall jacket for circulating low-pressure steam, the rectifying tower is communicated with a gas phase outlet at the top of the rectifying kettle, and a liquid inlet of a return tank is communicated with the gas phase outlet at the top of the rectifying tower through a condenser; and a liquid outlet of the reflux tank is communicated with a reflux inlet at the upper end of the rectifying tower through a first throttle valve and is communicated with the front distillation storage tank and the chlorobenzene circulating tank through a second throttle valve. Compared with the prior art, the purity and quality of circulating chlorobenzene are improved, the activity and selectivity of subsequent reaction of chlorobenzene are ensured, the product yield in the production process of 2-alkylanthraquinone is ensured, and chlorobenzene is recycled in an economical and environment-friendly manner.

Description

Technical Field

[0001] This utility model relates to the production of 2-alkylanthraquinone, and more particularly to a circulating chlorobenzene distillation apparatus for the production of 2-alkylanthraquinone. Background Technology

[0002] Chlorobenzene, a solvent used in the production of 2-alkylanthraquinone, accumulates low-boiling and high-boiling substances after repeated recycling. Continued use will affect product yield, reduce economic efficiency, and increase byproducts, which mainly accumulate in wastewater, making wastewater treatment difficult and posing a threat to environmental protection. Utility Model Content

[0003] The present invention aims to solve at least one of the aforementioned technical problems by providing a circulating chlorobenzene distillation device for the production of 2-alkylanthraquinone, which facilitates chlorobenzene distillation for recycling and improves the product yield of circulating chlorobenzene.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0005] A circulating chlorobenzene distillation apparatus for the production of 2-alkylanthraquinone includes a distillation kettle, a distillation column, and a reflux tank. The distillation kettle is equipped with a stirrer and a peripheral jacket for the flow of low-pressure steam, such as 0-0.5 MPa steam. The distillation column is connected to the vapor outlet at the top of the distillation kettle. The liquid inlet of the reflux tank is connected to the vapor outlet at the top of the distillation column via a condenser. The liquid outlet of the reflux tank is connected to the reflux port at the upper end of the distillation column via a first throttling valve and to the fore-distillation storage tank and the chlorobenzene circulation tank via a second throttling valve.

[0006] Compared with the prior art, the beneficial effects of this application include: from an economic and environmental perspective, it removes impurities and purifies recycled chlorobenzene; improves the purity / quality of recycled chlorobenzene, ensures the activity and selectivity of subsequent reactions of chlorobenzene, guarantees the product yield in the production process of 2-alkylanthraquinone, and economically and environmentally reuses chlorobenzene.

[0007] As an improvement to the above technical solution, a drying unit is also included. The drying unit includes one or more dryers connected in series. The first dryer is used to input chlorobenzene, and the last dryer is used to sample and test the chlorobenzene content. The distillation kettle is used to purify the chlorobenzene that does not meet the standards after being dried by the drying unit.

[0008] As an improvement to the above technical solution, the dryer cavity includes an upper chamber filled with desiccant and a lower chamber suitable for buffering chlorobenzene. The top of the dryer is provided with an inlet for filling the upper chamber with chlorobenzene, the lower chamber is used to receive the chlorobenzene falling from the upper chamber, and the bottom of the lower chamber is provided with an outlet.

[0009] As an improvement to the above technical solution, a solid-alkali neutralization tank is also included. The solid-alkali neutralization tank is used to receive chlorobenzene to be purified and to transport the neutralized chlorobenzene to the drying unit.

[0010] As an improvement to the above technical solution, an activated carbon adsorber is also included, and a solid alkali neutralization tank is used to supply chlorobenzene to the drying unit through the activated carbon adsorber.

[0011] As an improvement to the above technical solution, the distillation kettle is provided with a nitrogen inlet, the top of the reflux tank is provided with an exhaust port, and the distillation kettle, the distillation column, and the reflux tank are connected in series to form a displacement pipeline, which is used to discharge the gas inside through nitrogen.

[0012] As an improvement to the above technical solution, the exhaust port at the top of the reflux tank is connected to a vacuum unit, the displacement pipeline is suitable for evacuating and then filling with nitrogen, and the distillation kettle and the distillation column are used for evacuating and then heating and distilling.

[0013] As an improvement to the above technical solution, the chlorobenzene circulation tank is a buried sealed tank. Attached Figure Description

[0014] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings, wherein:

[0015] Figure 1 This is a schematic diagram of the circulating chlorobenzene distillation device in the production process of alkylanthraquinone according to Embodiment 2 of this utility model.

[0016] The accompanying drawings are only one specific embodiment of this utility model, and the form and structure of this specific embodiment should not limit the extension of other embodiments.

[0017] Primary condenser E1, secondary condenser E2;

[0018] First throttle valve F1, second throttle valve F2, third throttle valve F3;

[0019] Reflux pump P1, distillation kettle R1, distillation column T1, reflux tank V1. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] Reference Figure 1This utility model provides a circulating chlorobenzene distillation device for the production of 2-alkylanthraquinone, including a distillation kettle R1, a distillation column T1, and a reflux tank V1. The distillation kettle R1 is equipped with a stirring paddle and a peripheral jacket for the flow of low-pressure steam, such as 0-0.5 MPa steam. The distillation column T1 is connected to the gas phase outlet at the top of the distillation kettle R1. The liquid inlet of the reflux tank V1 is connected to the gas phase outlet at the top of the distillation column T1 through a condenser. The liquid outlet of the reflux tank V1 is connected to the reflux port at the upper end of the distillation column T1 through a first throttle valve F1, and is connected to the fore-distillation storage tank and the chlorobenzene circulation tank through a second throttle valve F2.

[0022] It is understandable that the distillation vessel R1 is equipped with a liquid inlet, through which chlorobenzene to be distilled and purified is poured into the distillation vessel R1.

[0023] Ideally, the condenser includes a primary condenser E1 and a secondary condenser E2.

[0024] In the production of 2-alkylanthraquinone, chlorobenzene is primarily used as a solvent and reaction medium. Chlorobenzene is an ideal solvent for alkylation reactions, effectively dissolving anthraquinone, catalysts (such as AlCl3), and reaction intermediates, ensuring a homogeneous reaction; it also reduces system viscosity, promotes mass and heat transfer, and improves reaction efficiency. Chlorobenzene helps disperse the catalyst and maintain its activity.

[0025] In the alkylation reaction, the ideal chlorobenzene content of the recycled chlorobenzene is ≥97%, while the purchased chlorobenzene requires a content of ≥99% to reduce side reactions and improve the selectivity of 2-alkylanthraquinone. After a single alkylation reaction, the main components of the chlorobenzene to be purified are chlorobenzene (≥85%), water, and byproducts (such as the main pure benzene). Using chlorobenzene as a standard, its boiling point is around 132℃, while water (boiling point around 100℃) and pure benzene (boiling point around 80℃) are considered low-boiling substances, and other byproducts are considered high-boiling substances. When the temperature of the distillation vessel R1 reaches around 145℃, the chlorobenzene and any water present will boil and evaporate.

[0026] To address the issue of separation costs and to reduce the interference of water (as an azeotrope) on chlorobenzene distillation, a drying unit is preferably included. This unit comprises one or more dryers (closed containers) connected in series. The first dryer is used to input chlorobenzene, the last dryer is used for sampling and testing chlorobenzene content, and the distillation vessel R1 is used to purify any chlorobenzene that does not meet the standards after drying by this unit. Specifically, if drying alone can achieve a chlorobenzene content ≥96.5% or a pure benzene content ≤3%, then the chlorobenzene to be purified does not require distillation, eliminating the distillation step, resulting in lower production costs and more convenient purification operations. For example, recycled chlorobenzene that has only been used once or circulated once can generally be upgraded to the required purity simply through drying. It is understood that the outlet of the last dryer is connected to the chlorobenzene circulation tank and the distillation vessel R1 via different on / off valves; chlorobenzene that does not meet the standards after drying is sent to the distillation vessel R1, while chlorobenzene that meets the standards can be transferred to the corresponding chlorobenzene circulation tank. The purity of chlorobenzene in the last dryer can be periodically tested by GC (gas chromatography), and can be monitored in real time using a Karl Fischer moisture analyzer.

[0027] Desiccants can be selected from molecular sieves (for deep dehydration), salt desiccants (such as calcium chloride), silica gel (for general drying), etc. During salt drying, a saturated salt solution forms at the bottom of the dryer. This brine should be periodically drained from the bottom to prevent liquid accumulation from affecting the drying effect and to reduce corrosion of the equipment bottom by the salt solution. After cleaning the dryer, any residual salt wastewater must be discharged. When draining brine from the bottom of the dryer, carefully observe the sight glass to ensure that chlorobenzene is not discharged outside the equipment.

[0028] It is understandable that there may be some elevation difference between equipment such as the dryer, distillation kettle R1, distillation column T1, reflux tank V1, foredistillation storage tank, and chlorobenzene circulation tank. Installing a pumping pump (water pump) to ensure the supply of feed liquid between these devices is standard practice. To control the flow of feed into and out of each device, on / off valves are installed at the inlets and outlets of the equipment, as well as between the devices; these are also standard practice, such as ball valves, gate valves, and butterfly valves. The foredistillation storage tank and the chlorobenzene circulation tank are connected to the second throttle valve F2 via corresponding on / off valves.

[0029] In some embodiments of this utility model, the distillation vessel R1 is provided with a nitrogen inlet, and the top of the reflux tank V1 is provided with an exhaust port. The distillation vessel R1, the distillation column T1, and the reflux tank V1 are connected in series to form a displacement pipeline. The displacement pipeline is used to discharge the gas inside it, such as air, oxygen, and other residual gases (possible flammable / explosive gases), through nitrogen. After pressurizing and injecting nitrogen, the gas is discharged. This process is repeated multiple times to create an inert environment in the distillation line.

[0030] The operation process of this utility model can be as follows:

[0031] The drying and dehydration process involves four dryers. The chlorobenzene to be purified enters the first dryer, then flows sequentially through the second, third, and fourth dryers. The flow rate is controlled at 1.2 ± 0.2 m³ / h by interlocking the regulating valve and flow meter at the outlet of the delivery pump (adjusting the throttle valve). 3 / h, turn on the dryer at the scheduled interval to check if desiccant needs to be added;

[0032] After dehydration testing and decision-making, samples are taken for analysis. If the chlorobenzene content is ≤96.5% and the pure benzene content is ≥3%, distillation is required to purify and remove impurities. If the chlorobenzene content is ≥96.5% or the pure benzene content is ≤3%, distillation is not required for the chlorobenzene to be purified in this batch.

[0033] Nitrogen purging: Close the vent valve of distillation vessel R1, open the purging pipeline, and introduce nitrogen gas at about 50 kPa into distillation vessel R1. Depressurize the vacuum unit connected to the exhaust port at the top of reflux tank V1. Repeat this purging and discharging process 3 times.

[0034] Pre-cooling involves the flow of cooling water, such as chilled water or circulating water, through the secondary flow channels (shell side or tube side) of the condenser.

[0035] With the feed inlet and the vent valve of distillation vessel R1 open, dried chlorobenzene is pumped into distillation vessel R1. Feeding is stopped when the liquid level in distillation vessel R1 reaches 70%, and the vent valve of distillation vessel R1 is closed.

[0036] Negative pressure, stirring in distillation vessel R1, vacuum evacuation of distillation vessel R1, distillation column T1 and reflux tank V1, reducing oxygen, flammable and explosive gases, and reducing water vapor and other light components to a certain extent in advance, thus lowering the actual distillation boiling point due to negative system pressure.

[0037] Forward heating: Open the steam in the distillation vessel R1 to heat the chlorobenzene inside, so that its liquid phase temperature slowly rises to 80°C. During this process, observe the temperature in the middle and top of the distillation column T1, and the condensate temperature and flow rate in the secondary condenser E2.

[0038] Forward distillation total reflux: When the liquid level in reflux tank V1 reaches 50%, open reflux pump P1 and the first throttle valve F1, and send the condensate in reflux tank V1 into distillation column T1.

[0039] After the foredistillate is collected and refluxed for 1-3 hours, the condensate from the secondary condenser E2 is analyzed. When the benzene content is ≥96%, the second throttle valve F2 and the on / off valve between the reflux tank V1 and the foredistillate tank are opened, and the on / off valve between the second throttle valve F2 and the chlorobenzene circulation tank is closed to maintain a reflux ratio of 20-25.

[0040] The chlorobenzene to be purified at 70% liquid level requires a pre-distillation time T1, such as 30 minutes, to complete the extraction of pure benzene;

[0041] The chlorobenzene distillation process involves heating the vapor to increase its pressure and / or increase the flow rate and / or velocity of the vapor in the distillation vessel R1, causing the liquid phase temperature of the distillation vessel R1 to slowly rise to 145°C. During this process, the temperatures in the middle and top of the distillation column T1, as well as the condensate temperature and flow rate in the secondary condenser E2, are observed.

[0042] Chlorobenzene is distilled under total reflux. The condensate from the secondary condenser E2 is analyzed. When the chlorobenzene content is ≤97%, the reflux pump P1 and the first throttle valve F1 are opened, and the condensate in the reflux tank V1 is sent into the distillation column T1. The second throttle valve F2 and the corresponding on / off valve are closed.

[0043] In the actual distillation of chlorobenzene, when the chlorobenzene content of the condensate output from the secondary condenser E2 is ≥97%, the second throttle valve F2 is opened, and the output of the second throttle valve F2 is switched to the chlorobenzene circulation tank, while maintaining a reflux ratio of 1-2.

[0044] The chlorobenzene content of the condensate is ≤10%, and chlorobenzene distillation is completed;

[0045] After post-processing, chlorobenzene distillation is completed, and even ethylbenzene distillation is further completed. The distillation residue is then returned to the distillation residue tank and treated as hazardous waste.

[0046] It is understandable that the vent valve of the distillation vessel R1 is actually an on / off valve, which can be manually or electrically opened and closed, such as a ball valve, gate valve, butterfly valve, etc. The peripheral jacket of the distillation vessel R1 is connected to steam through the third throttle valve F3, and the distillation flow rate and / or flow rate of the peripheral jacket of the distillation vessel R1 is adjusted by the third throttle valve F3.

[0047] Reference Figure 1 Temperature sensor Q1 is connected to the bottom and / or middle of distillation vessel R1; temperature sensors Q2 and Q3 are connected to the middle and top of distillation column T1; temperature sensor Q4 and flow meter Q5 are connected to the output of the second condenser; and liquid level sensor Q6 is connected to reflux tank V1.

[0048] The reflux ratio R = L / D, where L is the flow rate of the reflux liquid at the top of the column, and D is the flow rate of the product collected at the top of the column. The distillation vessel R1 is distilled at a stable temperature, and the flow rate of the first throttle valve F1 can be adjusted to obtain the desired reflux ratio.

[0049] Compared with the prior art, the beneficial effects of this application include: from an economic and environmental perspective, it removes impurities and purifies recycled chlorobenzene; improves the purity / quality of recycled chlorobenzene, ensures the activity and selectivity of subsequent reactions of chlorobenzene, guarantees the product yield in the production process of 2-alkylanthraquinone, and economically and environmentally reuses chlorobenzene.

[0050] In some embodiments of this utility model, the dryer cavity includes an upper chamber filled with desiccant and a lower chamber suitable for buffering chlorobenzene. The top of the dryer is provided with an inlet for filling the upper chamber with chlorobenzene, the lower chamber is used to receive the chlorobenzene falling from the upper chamber, and the bottom of the lower chamber is provided with an outlet. When the purified chlorobenzene flows through the desiccant packing layer, coarse drying is performed. At this time, most of the moisture in the chlorobenzene is eliminated, improving the chlorobenzene dehydration efficiency and ensuring the production of anthraquinone from the perspective of feeding efficiency.

[0051] Ideally, the lower chamber of the last dryer should be expanded, or connected to a chlorobenzene buffer tank. When the lower chamber of the last dryer is expanded to buffer chlorobenzene, the upper desiccant packing layer continues to absorb moisture released from the chlorobenzene.

[0052] Preferably, the dryer is equipped with heating elements surrounding the upper chamber, such as heating wires, coils for passing heat medium, and jackets for passing heat medium. The top of the dryer also has a vent port connected to an on / off valve. In this invention, after the dryer has discharged chlorobenzene, the chlorobenzene input and output ports are closed, the vent port is opened, and the heating elements are activated to dry the desiccant filling layer.

[0053] In practice, the chlorobenzene to be purified may contain residual acidic impurities (such as HCl, H2SO4, etc.). In some embodiments of this invention, a solid-alkali neutralization tank is also included. This tank receives the chlorobenzene to be purified and then transfers the neutralized chlorobenzene to the drying unit. In the solid-alkali neutralization tank, these acidic impurities are neutralized by an alkaline substance (such as solid sodium hydroxide NaOH or sodium carbonate Na2CO3). The precipitate produced by the neutralization reaction can be removed by sedimentation, and the water produced by the neutralization reaction can be removed by the drying unit. The saturated brine is discharged from the bottom of the dryer. This invention eliminates acidic impurities in the chlorobenzene to be purified, preventing corrosion of subsequent equipment such as the dryer, distillation kettle R1, and distillation column T1.

[0054] In some embodiments of this invention, the exhaust port at the top of the reflux tank V1 is connected to a vacuum unit, and the replacement pipeline is suitable for evacuation followed by nitrogen filling. The distillation kettle R1 and distillation column T1 are used for evacuation followed by reheating and distillation. The distillation kettle R1 is used for stirring and evacuation followed by reheating and distillation, eliminating trace amounts of oxygen and flammable gases that may dissolve in the chlorobenzene to be purified, thus enhancing safety. The negative pressure causes light components with boiling points lower than chlorobenzene (such as water vapor) to volatilize earlier, reducing azeotropic interference and improving product purity. The negative pressure also lowers the boiling points of benzene and chlorobenzene in this distillation, reducing side reactions and saving steam used in distillation. On the other hand, the components of the distillation system are pressure-resistant, such as with reinforced flange seals and the use of vacuum-grade materials.

[0055] In some embodiments of this utility model, an activated carbon filter / activated carbon adsorber is also included, and a solid alkali neutralization tank is used to supply chlorobenzene to the drying unit through the activated carbon adsorber to reduce the accumulation of impurities.

[0056] In some embodiments of this utility model, the chlorobenzene circulation tank is a buried sealed tank that is anti-static, prohibits open flames, and is ventilated to prevent poisoning.

[0057] The above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the scope of the technical solution of this utility model.

Claims

1. A circulating chlorobenzene distillation apparatus for the production of 2-alkylanthraquinone, characterized in that, It comprises: a rectifying kettle (R1) provided with a stirring paddle and a jacket for circulating low-pressure steam, a rectifying tower (T1) connected to the gas phase outlet at the top of the rectifying kettle (R1), a reflux tank (V1) connected to the gas phase outlet at the top of the rectifying tower (T1) through a condenser, the liquid outlet of the reflux tank (V1) connected to the reflux inlet at the upper end of the rectifying tower (T1) through a first throttle valve (F1) and connected to a chlorobenzene circulating tank and a pre-distillation tank through a second throttle valve (F2).

2. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to claim 1, characterized by, It further comprises a drying unit, which comprises one or more dryers connected in series, the first dryer for inputting chlorobenzene and the last dryer for sampling the chlorobenzene content, and the rectifying kettle (R1) for purifying chlorobenzene that does not meet the standards after being dried by the drying unit.

3. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to claim 2, characterized by, The bore of the dryer comprises an upper chamber filled with drying agent and a lower chamber adapted to store chlorobenzene, the top of the dryer is provided with a feed inlet for filling the upper chamber with chlorobenzene, and the lower chamber is used to receive chlorobenzene falling from the upper chamber, and the bottom of the lower chamber is provided with a discharge outlet.

4. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to claim 2, characterized by, It further comprises a solid alkali neutralization tank for receiving chlorobenzene to be purified and for feeding the neutralized chlorobenzene to the drying unit.

5. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to claim 4, characterized by, It further comprises an activated carbon adsorber, and the solid alkali neutralization tank is used to pass through the activated carbon adsorber to provide chlorobenzene to the drying unit.

6. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to any one of claims 1 to 5, characterized by, The rectifying kettle (R1) is provided with a nitrogen inlet, the top of the reflux tank (V1) is provided with an exhaust port, and the rectifying kettle (R1), the rectifying tower (T1), and the reflux tank (V1) are connected in series to form a displacement pipeline for discharging the gas therein by nitrogen.

7. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to claim 6, characterized by, The exhaust port at the top of the reflux tank (V1) is connected to a vacuum unit, the displacement pipeline is adapted to be vacuumized and then filled with nitrogen, and the rectifying kettle (R1) and the rectifying tower (T1) are used to be vacuumized and then heated for distillation.

8. The apparatus for rectifying circulating chlorobenzene in a 2-alkylanthraquinone production process according to any one of claims 1 to 5, characterized by, The chlorobenzene circulating tank is a buried sealed tank.

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