A terephthalaldehyde reaction gas collector and a capture method

Abstract

The invention discloses a terephthalaldehyde reaction gas collector and a collecting method, wherein the collector is composed of a cylinder, an upper cover plate, a jacket, a center plate containing a condenser, a baffle plate, and an inlet and outlet pipe. After the reaction gas enters the cylinder through the air inlet, it reaches the bottom of the cylinder under the baffle effect of the baffle plate, and then passes through the center plate and flows out from the air outlet after being baffled upward. The solids precipitated after the terephthalaldehyde gas is cooled through the jacket and the condenser on the center plate are intercepted, and other gases are discharged from the air outlet. The invention can effectively capture the terephthalaldehyde in the gas after the gas phase oxidation reaction of para-xylene, and the captured terephthalaldehyde solids can be easily cleaned, reducing the cleaning difficulty.

Description

Technical Field

[0001] The invention relates to a technology for preparing terephthalaldehyde by gas phase oxidation of p-xylene, and in particular to a terephthalaldehyde reaction gas collector and a collecting method. Background Art

[0002] Terephthalaldehyde is an important downstream fine chemical product of p-xylene, mainly used in the synthesis of fluorescent brighteners, pharmaceutical products, dyes and fragrances. Due to its two active aldehyde groups, terephthalaldehyde can also self-polymerize or copolymerize with other monomers to form polymer materials.

[0003] The traditional method for synthesizing terephthalaldehyde adopts the chlorination and hydrolysis of p-xylene, which is not environmentally friendly, and the terephthalaldehyde product contains a small amount of chlorine that is difficult to remove, which limits its application in the fields of medicine. Therefore, research on the production of terephthalaldehyde by gas phase oxidation of p-xylene has been carried out successively at home and abroad. Among them, how to conveniently and effectively capture the terephthalaldehyde in the gas after the gas phase reaction has become a problem that needs to be solved.

[0004] CN101166707 discloses a method and apparatus for continuously separating aromatic dialdehydes from a reaction mixture obtained by a gas-phase oxidation reaction of xylene. For the separation and capture of terephthalaldehyde, it is proposed to introduce a gas phase mixture containing aromatic dialdehydes obtained by a gas-phase oxidation reaction of xylene into a condenser by cooling, and selectively condense the aromatic dialdehydes by cooling the mixture to 5-70°C. It also introduces an apparatus for separating aromatic dialdehydes, including a condenser for cooling the reaction mixture so that at least a portion of the aromatic dialdehydes contained in the reaction mixture are condensed; and a cyclone for separating and discharging the condensed aromatic dialdehydes contained in the cooled reaction mixture. The condenser of the patent has no components, and the cooling gas is directly introduced, so the utilization efficiency of the condenser is not high; a vibrator is also connected to the outer wall of the condenser to promote the gravity sedimentation of the aromatic dialdehydes, but the setting of the vibrator will weaken the structural strength of the condenser assembly.

[0005] CN104208900 discloses a crystal collector for anhydrides. It includes a cylindrical shell, a spherical upper head is sealed at the upper end of the shell, and a conical lower head is sealed at the lower end. A number of springs are evenly distributed in the shell, and the upper end of each spring is respectively connected to a mesh connecting frame fixed to the upper end face of the shell, and the lower end of each spring is a free end. The spring can swing freely in the shell, and the side wall of the shell is connected to a nitrogen inlet. By regularly purging nitrogen into the interior, the anti-stickiness of the spring, the interior of the shell, and the upper and lower heads can be further improved. The patent does not mention how to make the spring swing, and the evenly distributed springs also compress the space of the collector, the capture capacity becomes smaller, and even with nitrogen purging, the material cannot be effectively shed.

[0006] In summary, the existing collectors that can be used to capture terephthalaldehyde reaction gas have technical problems such as low condensation efficiency, small capture capacity, and inconvenient cleaning of terephthalaldehyde solids after condensation. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a terephthalaldehyde reaction gas collector and a capturing method.

[0008] The technical solution adopted by the present invention is:

[0009] A terephthalaldehyde reaction gas collector is composed of a cylinder, an upper cover plate, a jacket, a center plate containing a condenser, a baffle plate, and inlet and outlet pipes. The upper cover plate is used to seal the upper end of the cylinder. The cylinder is divided into two cavities, an air inlet cavity and an air outlet cavity, by the center plate. The air inlet pipe is arranged on one side of the outer edge of the upper cover plate and is connected to the air inlet cavity. The air outlet pipe is arranged on the other side of the outer edge of the upper cover plate and is connected to the air outlet cavity. A gas flow channel is opened at the bottom of the center plate, and the air inlet cavity and the air outlet cavity are connected through the gas flow channel. Baffle plates are fixed on both sides of the center plate, and the baffle plates are provided in a plurality of pieces and are arranged at intervals from top to bottom. The center plate is detachably connected to the cylinder. The jacket is arranged on the outer peripheral surface of the cylinder, and a cooling medium is passed through the jacket and the condenser.

[0010] Furthermore, the condenser is wrapped in the center plate and does not directly contact the material. The inlet end of the condenser extends from one side of the upper cover plate for the introduction of cooling medium, and the outlet end of the condenser extends from the other side of the upper cover plate for the outflow of cooling medium after heat exchange. The condenser is serpentine-coiled in the center plate from its inlet end to its outlet end.

[0011] Furthermore, the cold wall tube is composed of an inlet tube, an outlet tube and a condensation channel opened in the body of the center plate, and the inlet tube and the outlet tube are threadedly connected to the center plate.

[0012] Furthermore, the center plate is composed of two flat plates with the same structure, and two opposite side surfaces of the two flat plates are provided with tube cavities adapted to the condenser tubes, and the condenser tubes are arranged in the tube cavities.

[0013] Furthermore, the baffle includes a first baffle and a second baffle, and the first baffle and the second baffle are arranged alternately; the first baffle is semicircular, the outer diameter of the semicircle is adapted to the inner diameter of the cylinder, and a gas through hole is provided in the center of the semicircle; the second baffle is semicircular, the outer diameter of the semicircle is adapted to the inner diameter of the cylinder, and a gas through hole is provided at the outer edge of the semicircle.

[0014] Furthermore, the center plate is arranged on a side close to the air outlet pipe, the uppermost baffle in the air inlet cavity is the first baffle, the uppermost baffle in the air outlet cavity is the second baffle, and the position of the uppermost first baffle in the air inlet cavity is lower than the uppermost second baffle in the air outlet cavity.

[0015] A method for capturing terephthalaldehyde reaction gas comprises the following steps: introducing reaction gas containing terephthalaldehyde into any one of the above-mentioned collectors, introducing a cooling medium into the collector, cooling the reaction gas to below a certain temperature, causing the terephthalaldehyde in the reaction gas to change from a gaseous state to a solid state and be condensed in the collector, and the remaining reaction gas mixture escapes from an air outlet pipe of the collector; after a certain amount of terephthalaldehyde is collected in the collector, switching to another standby collector, cleaning the terephthalaldehyde collected in the collector and keeping it for standby.

[0016] Furthermore, the temperature of the reaction gas is maintained at 140-200° C. before being introduced into the collector.

[0017] Furthermore, after the reaction gas enters the collector, it is cooled to below 70° C. in the collector.

[0018] Furthermore, the reaction gas is cooled to 30-50° C. in the trap.

[0019] Beneficial effects of the present invention: The present invention adopts the method of cooling inside and outside the jacket and the center plate, which can effectively capture terephthalaldehyde in the gas after the gas-phase oxidation reaction of para-xylene. The reaction gas is cooled by the jacket and the condenser on the center plate under the baffle effect of the baffle, and the solid precipitated is intercepted, and other gases are discharged through the outlet. The baffle and the center plate of the present invention can be easily disassembled, and the captured terephthalaldehyde solids can be conveniently cleaned, reducing the difficulty of cleaning; and its design method makes full use of the space of the cylinder, which can capture more terephthalaldehyde solids, increase the single use time of the collector, and reduce the labor intensity caused by frequent switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the terephthalaldehyde reaction gas collector of Example 1 of the present invention.

[0021] Figure 2 It is a schematic structural diagram of the second baffle of the terephthalaldehyde reaction gas collector of Example 1 of the present invention.

[0022] Figure 3 It is a schematic structural diagram of the first baffle of the terephthalaldehyde reaction gas collector of Example 1 of the present invention.

[0023] Figure 4 yes Figure 2 It is a schematic structural diagram of the center plate of the terephthalaldehyde reaction gas collector of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0025] See also Figure 1 to Figure 4 Example 1 provides a terephthalaldehyde reaction gas collector, which consists of an air inlet pipe 1, an air outlet pipe 2, an upper cover plate 3, a center plate 4, a cylinder 5, a first baffle 7, a second baffle 6, a condenser 8 and a jacket 9.

[0026] The upper cover plate 3 is covered on the upper end of the cylinder 5 for sealing the cylinder. The condenser 8 is wrapped in the center plate 4, the inlet end of the condenser extends from one side of the upper cover plate for the cooling medium to enter, and the outlet end of the condenser extends from the other side of the upper cover plate for the cooling medium to flow out after heat exchange, and the condenser is coiled in the center plate from its inlet end to its outlet end in a serpentine shape; the cylinder is divided into two cavities, an air inlet cavity and an air outlet cavity, by the center plate 4, the air inlet pipe 1 is arranged on one side of the outer edge of the upper cover plate and communicates with the air inlet cavity, the air outlet pipe 2 is arranged on the other side of the outer edge of the upper cover plate and communicates with the air outlet cavity, and a gas flow channel is opened at the bottom of the center plate 4, and the air inlet cavity and the air outlet cavity are communicated through the gas flow channel; the first baffle 7 and the second baffle 6 are fixed on the two side surfaces of the center plate 4, and the first baffle 7 and the second baffle 6 are arranged alternately from top to bottom; the jacket 9 is arranged on the outer peripheral surface of the cylinder 5, and the jacket 9 and the condenser 8 are passed with cooling medium such as water, alcohol or frozen brine.

[0027] The upper cover plate 3 and the cylinder 5 can be sealed and connected by flange or other quick connection methods. The upper cover plate 3 is provided with an air inlet, an air outlet, a condensate pipe inlet and a condensate pipe outlet. The air inlet pipe 1 is arranged in the air inlet pipe, the air outlet pipe 2 is arranged in the air outlet pipe, and the condensate pipe inlet and the condensate pipe outlet are used to pass through the condensate pipe in the center plate.

[0028] The condenser tube 8 is wrapped in the center plate 4 and does not come into direct contact with the material. For example, in this embodiment, the cold wall tube is composed of an inlet tube, an outlet tube and a condensation channel opened in the body of the center plate 4. The inlet tube and the outlet tube are threadedly connected to the center plate. The one-piece molding structure is simple and easy to install and disassemble.

[0029] In another embodiment of the present invention, the center plate 4 is composed of two flat plates of the same structure, and the two opposite sides of the two flat plates are provided with cavities adapted to the condenser tubes, and the condenser tubes 8 are embedded in the cavities. The separated condenser tubes and the center plate can be made of different materials, and the condenser tubes can be easily updated.

[0030] The center plate 4 and the cylinder 5 can be connected by plugging, and the inner wall of the cylinder 5 is provided with a slot, and the slot is adapted to the thickness of the center plate. The center plate 4 is inserted into the cylinder 5. One end of the first baffle 7 and the second baffle 6 are welded to the two side surfaces of the center plate 4, and form a whole with the center plate. For example, in this embodiment, the air inlet cavity and the air outlet cavity are respectively provided with a first baffle 7 and a second baffle 6. In other embodiments, multiple first baffles 7 and second baffles 6 can also be provided. The integrally designed center plate 4, condenser, and baffle make it convenient to remove the terephthalaldehyde gas from the cylinder after it is condensed into crystals and clean it up.

[0031] The cold source in the condenser tube 8 is conducted to the first baffle plate 7 and the second baffle plate 6 through the central plate 4. The first baffle plate 7 and the second baffle plate 6 also function as cooling fins.

[0032] In order to improve the condensation effect, the uppermost baffle in the air inlet cavity of the collector in this embodiment is designed as a first baffle 7, which is semicircular in shape, with an outer diameter matching the inner diameter of the cylinder 5, and a gas through hole is provided in the center of the semicircle. The uppermost baffle in the air outlet cavity is a second baffle 6, which is semicircular in shape, with an outer diameter matching the inner diameter of the cylinder 5, and a gas through hole is provided in the outer edge of the semicircle. After the reaction gas enters the air inlet chamber through the air inlet pipe 1, it is blocked by the first baffle plate 7, flows from the outer edge of the cylinder to the center of the cylinder, flows downward through the gas through hole of the first baffle plate 7, is blocked by the second baffle plate 6, flows from the center of the cylinder to the outer edge of the cylinder, and then flows downward through the gas through hole of the second baffle plate 6 through the bottom channel of the center plate into the air outlet chamber, and is discharged from the air outlet pipe 2 after being deflected by the second baffle plate 6 and the first baffle plate 7 in the air outlet chamber. Most of the terephthalaldehyde solids are intercepted on the first baffle plate 7, and the remaining reaction gas mixture reaches the bottom of the cylinder 5 under the deflection effect of the baffle plates 6 and 7, and then passes through the center plate 4 upward and flows out from the air outlet 2 after being deflected.

[0033] Since most of the terephthalaldehyde solids are intercepted on the first baffle 7, the installation position of the center plate 4 is designed to be closer to the side of the outlet pipe 2, and the position of the first baffle at the upper end of the air inlet cavity is lower than the second baffle at the upper end of the air outlet cavity, thereby providing more interception space, more effectively utilizing the cylinder space, and capturing more solids.

[0034] A method for capturing terephthalaldehyde reaction gas comprises the following steps:

[0035] 1) A cooling liquid medium, such as water, alcohol or frozen brine, is introduced into the condenser tube 8 and the jacket 9 in the collector, and the temperature is maintained between 20 and 30°C;

[0036] 2) introducing the reaction gas containing terephthalaldehyde into the collector from the gas inlet 1, and maintaining the gas temperature between 140 and 200° C.;

[0037] 3) In the collector, the reaction gas is cooled to below 70°C, preferably 30-50°C, and the terephthalaldehyde in the reaction gas is thus converted from gaseous to solid and condensed into the collector. The remaining reaction gas mixture reaches the bottom of the cylinder 5 under the deflection effect of the baffles 6 and 7, and then passes through the center plate 4 upward and flows out from the gas outlet 2 after being deflected;

[0038] 4) After the capture operation is stopped or switched, the collector is cut out, the cooling medium is disconnected, the upper cover plate 3 is opened, the center plate 4 and the baffles 6 and 7 are taken out, the baffles 6 and 7 and the terephthalaldehyde solids in the cylinder 5 are cleaned, and then reassembled for use.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A terephthalaldehyde reaction gas collector, characterized in that: It is composed of a cylinder, an upper cover, a jacket, a center plate including a condenser tube, a baffle plate, and an inlet and outlet pipe. The upper cover plate is used to seal the upper end of the cylinder. The cylinder is divided into two cavities, an air inlet cavity and an air outlet cavity, by the center plate. The air inlet pipe is arranged on one side of the outer edge of the upper cover plate and is connected to the air inlet cavity. The air outlet pipe is arranged on the other side of the outer edge of the upper cover plate and is connected to the air outlet cavity. A gas flow channel is opened at the bottom of the center plate, and the air inlet cavity and the air outlet cavity are connected through the gas flow channel. Baffle plates are fixed on both sides of the center plate. The baffle plates are provided in a plurality of pieces and are arranged at intervals from top to bottom. The center plate is detachably connected to the cylinder. The jacket is arranged on the outer peripheral surface of the cylinder. The cooling medium is passed through the jacket and the condenser tube. The condenser is wrapped in the center plate and does not come into direct contact with the material. The inlet end of the condenser extends from one side of the upper cover plate for the introduction of cooling medium, and the outlet end of the condenser extends from the other side of the upper cover plate for the outflow of cooling medium after heat exchange. The condenser is serpentine-shaped and coiled in the center plate from its inlet end to its outlet end. The baffles include a first baffle and a second baffle, which are arranged alternately; one end of the first baffle and the second baffle are welded to the two side surfaces of the center plate to form a whole with the center plate.

2. The terephthalaldehyde reaction gas collector according to claim 1, characterized in that: The condenser pipe is composed of an inlet pipe, an outlet pipe and a condensation channel opened in the body of the center plate. The inlet pipe and the outlet pipe are threadedly connected to the center plate.

3. The terephthalaldehyde reaction gas collector according to claim 1, characterized in that: The center plate is composed of two flat plates with the same structure. Two opposite sides of the two flat plates are provided with tube cavities adapted to the condenser tubes, and the condenser tubes are arranged in the tube cavities.

4. The terephthalaldehyde reaction gas collector according to claim 1, characterized in that: The baffle includes a first baffle and a second baffle, and the first baffle and the second baffle are arranged alternately; the first baffle is semicircular, the outer diameter of the semicircle is adapted to the inner diameter of the cylinder, and a gas through hole is provided in the center of the semicircle; the second baffle is semicircular, the outer diameter of the semicircle is adapted to the inner diameter of the cylinder, and a gas through hole is provided at the outer edge of the semicircle.

5. The terephthalaldehyde reaction gas collector according to claim 1, characterized in that: The center plate is arranged on a side close to the air outlet pipe, the uppermost baffle in the air inlet cavity is the first baffle, the uppermost baffle in the air outlet cavity is the second baffle, and the position of the uppermost first baffle in the air inlet cavity is lower than the uppermost second baffle in the air outlet cavity.

6. A method for capturing terephthalaldehyde reaction gas, characterized in that: The reaction gas containing terephthalaldehyde is introduced into the collector according to any one of claims 1 to 5, and a cooling medium is passed into the collector, the reaction gas is cooled to below 70°C, the terephthalaldehyde in the reaction gas is converted from gaseous to solid and condensed in the collector, and the remaining reaction gas mixture escapes from the gas outlet pipe of the collector; after a certain amount of terephthalaldehyde is collected in the collector, it is switched to another spare collector, and the terephthalaldehyde collected in the collector is cleaned and kept for standby use.

7. The capture method according to claim 6, characterized in that: The temperature of the reaction gas is maintained at 140~200℃ before it is introduced into the collector.

8. The capture method according to claim 6, characterized in that: The reaction gas is cooled to 30~50℃ in the collector.

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