Continuous palladium on carbon hydrogenation process and apparatus

Abstract

The application provides a continuous palladium-carbon hydrogenation reaction method, which is carried out according to the following steps: step one, mixing carbon catalyst with a solvent, and then injecting into the inside of a reactor; step two, connecting and starting a circulating pump to make the inside catalyst partially flow in a circulating mode; step three, injecting p-nitrotoluene and hydrogen, and carrying out heat exchange treatment on the whole reactor through a heat exchanger to keep the temperature stable during the reaction; and step four, discharging the reaction liquid and carrying out filtration treatment. The continuous palladium-carbon hydrogenation reaction method and equipment optimize the catalytic effect of the catalyst, improve the filtration efficiency, ensure that the raw material liquid and hydrogen enter the reactor, make the catalyst freely flow in the whole reaction area without being discharged from the reactor, continuously remove the product from the reactor, keep the temperature stable during the whole reaction process through the heat exchanger, and automatically stir the inside through the hydrogen injection.

Description

Technical Field

[0001] This invention relates to the field of chemical raw materials, specifically to a continuous palladium-carbon hydrogenation reaction method and equipment. Background Technology

[0002] p-Toluidine is an important intermediate in dyes, pharmaceuticals, and pesticides. Current synthesis methods mainly include iron powder reduction, sodium sulfide reduction, and catalytic hydrogenation reduction. Iron powder reduction produces large amounts of iron sludge, causing environmental pollution; sodium sulfide reduction produces hydrogen sulfide, which also pollutes the environment and is harmful to human health. Catalytic hydrogenation is the preferred method.

[0003] Currently, the intermittent operation of palladium-carbon catalytic hydrogenation requires repeated loading and cleaning of the catalyst, which is cumbersome and complex. In addition, the hydrogenation reaction pressure is relatively high, posing certain safety risks.

[0004] According to existing technologies, such as the benzoic acid hydrogenation continuous reaction apparatus and method described in Chinese patent document CN110961067B, the disclosed technical solution involves allowing the catalyst and raw materials to enter and exit the reactor simultaneously, with the catalyst being filtered after exiting the reactor. However, this filtration process is time-consuming and labor-intensive. Another example is the p-toluidine production method described in Chinese patent document CN102180801A, which involves the intermittent synthesis of p-aminotoluene from p-nitrotoluene. Since the raw material is solid and requires heating to melt before the reaction can proceed, this is unfavorable for continuous hydrogenation processes. Furthermore, conventional reaction methods lack precise temperature control and have low heat exchange efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a continuous palladium-carbon hydrogenation reaction method and apparatus to solve the problems mentioned in the background art. The present invention can ensure that the raw material liquid and hydrogen enter the reactor while allowing the catalyst to flow freely throughout the reaction zone without leaving the reactor, and at the same time continuously remove the product from the reactor, resulting in high heat exchange efficiency and a more uniform reaction process.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a continuous palladium-carbon hydrogenation reaction method, comprising the following steps: Step 1, mixing a carbon catalyst with a solvent and then injecting it into the reactor; Step 2, connecting and starting a circulation pump to circulate the catalyst portion inside; Step 3, injecting p-nitrotoluene and hydrogen gas, and using a heat exchanger to heat the entire reactor to maintain a stable temperature during the reaction; Step 4, discharging the reaction liquid and filtering it.

[0007] Furthermore, the p-nitrotoluene is dissolved in an alcohol solvent and enters from the top of the reactor, while hydrogen enters from the bottom of the reactor. The volume ratio of the alcohol solvent to p-nitrotoluene is 7-10:1, the molar ratio of hydrogen to p-nitrotoluene is 1.5-2:1, and the reaction temperature is 80-90℃, with a pressure of 8-10 bar.

[0008] Furthermore, in step four, the reaction liquid is discharged through a filter, and a back pressure valve is installed on the discharge pipeline to control the pressure inside the reactor and the discharge pipeline.

[0009] Furthermore, the circulation and extraction ratio is controlled to be greater than 100 by a circulation pump, and the reactor interior is blocked by a flow disruptor and baffles.

[0010] A continuous palladium-carbon hydrogenation reaction apparatus is provided. This apparatus is used in the reaction method described above and mainly includes a reactor, a heat exchanger, a central tube, and a stirring mechanism. A top plate is provided on the top of the reactor, and an injection port is provided on the surface of the top plate. A heat exchanger is installed on the surface of the reactor. A column is installed at the bottom of the reactor, and a support plate is installed at the bottom of the column. A central tube is installed inside the reactor, and a stirring mechanism is provided on the bottom side of the central tube.

[0011] Furthermore, a hydrogen delivery pipeline is connected to one side of the bottom of the reactor, and a discharge pipeline is connected to the bottom of the reactor. A back pressure valve and a filter are installed on the surface of the discharge pipeline. The other end of the hydrogen delivery pipeline is connected to the bottom of the central tube, and a reaction cavity is provided inside the reactor.

[0012] Furthermore, a support plate is welded and installed on one side of the outer shell at the bottom of the reactor, and a pressure pump is installed on the top of the support plate. The heat exchanger includes a heat-conducting plate and a heat exchange medium circulation pipeline.

[0013] Furthermore, the heat-conducting plate is attached to the surface of the reactor shell, and the two ends of the heat exchange medium circulation pipeline are respectively provided with a heat exchange medium injection pipe and a heat exchange medium return pipe, and the heat exchange medium injection pipe is connected to the pressure pump.

[0014] Furthermore, a diversion chamber is provided on the inner side of the bottom of the central tube, the agitation mechanism is installed on the outer side of the diversion chamber, and a rotating drum is provided in the middle of the agitation mechanism. A pressure chamber is provided inside the rotating drum. One end of the pressure chamber is connected to a diversion pipe. One end of the diversion pipe is movably connected to the inner wall of the reactor through a bearing, and the other end of the diversion pipe is movably connected to the surface of the bottom of the central tube through a bearing.

[0015] Furthermore, the interior of the diversion pipe is connected to the interior of the diversion chamber, a guide port is provided on the inner side of the rotating drum, an air hole is provided on the outer side of the guide port, and an agitator is welded and installed on the surface of the rotating drum.

[0016] The beneficial effects of this invention are:

[0017] 1. This continuous palladium-carbon hydrogenation reaction method and equipment optimizes the catalytic effect of the catalyst, improves the filtration efficiency, and allows the catalyst to flow freely throughout the reaction zone without leaving the reactor while ensuring that the feed liquid and hydrogen enter the reactor, and at the same time continuously removes the product from the reactor.

[0018] 2. This continuous palladium-carbon hydrogenation reactor uses a heat exchanger to circulate the heat exchange medium and connects it to a water bath circulation system to perform heat exchange treatment on the reactor section, ensuring stable temperature throughout the reaction process. The heat exchanger's exchange efficiency is improved by utilizing a bottom-to-top flow pattern. An internal stirring mechanism is installed to achieve automatic stirring using injected hydrogen gas, assisting the heat exchanger in performing a highly efficient heat exchange process. Attached Figure Description

[0019] Figure 1 This is a flowchart of a continuous palladium-carbon hydrogenation reaction method according to the present invention;

[0020] Figure 2 This is a structural diagram of the external appearance of a continuous palladium-carbon hydrogenation reaction apparatus according to the present invention;

[0021] Figure 3 This is a cross-sectional view of the reactor section in a continuous palladium-carbon hydrogenation reactor according to the present invention.

[0022] Figure 4 This is a schematic diagram of the stirring mechanism of a continuous palladium-carbon hydrogenation reactor according to the present invention.

[0023] Figure 5 This is a side sectional view of the stirring mechanism of a continuous palladium-carbon hydrogenation reactor according to the present invention;

[0024] In the diagram: 1. Reactor; 2. Top plate; 3. Column; 4. Support plate; 5. Inlet; 6. Hydrogen delivery pipeline; 7. Heat exchanger; 8. Support plate; 9. Pressure pump; 10. Reaction cavity; 11. Central tube; 12. Heat-conducting plate; 13. Heat exchange medium injection pipeline; 14. Heat exchange medium circulation pipeline; 15. Heat exchange medium return pipeline; 16. Diversion chamber; 17. Stirring mechanism; 18. Diversion pipeline; 19. Rotating drum; 20. Vent; 21. Stirring rod; 22. Bearing; 23. Pressure chamber; 24. Inlet; 25. Discharge pipeline; 26. Back pressure valve; 27. Filter. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] Please see Figures 1 to 5 This invention provides a technical solution: a continuous palladium-on-carbon hydrogenation reaction method for the synthesis of p-aminotoluene from p-nitrotoluene, mainly comprising a liquid feed system, a hydrogen feed system, a reactor 1, a heat exchanger 7, a circulating pump, and a cross-flow filter 27, etc., and is carried out according to the following steps:

[0027] (1) The palladium on carbon catalyst is dissolved in the solvent and added to reactor 1 first, so that the whole system is catalyst and solvent, and the circulation pump is turned on to allow the catalyst to circulate inside reactor 1.

[0028] (2) Dissolve p-nitrotoluene in an alcohol solvent and enter from the top of reactor 1. Hydrogen enters from the bottom of reactor 1. The reaction liquid is discharged through filter 27. A back pressure valve 26 is installed on the discharge pipeline 25 as needed to ensure the system pressure.

[0029] (3) The heat exchange medium flow side of heat exchanger 7 is connected to the water bath circulation machine to exchange heat for the entire reaction and ensure the temperature is stable throughout the reaction process.

[0030] In the above process of this embodiment, the volume ratio of alcohol solvent to p-nitrotoluene is 7-10:1, the molar ratio of hydrogen to p-nitrotoluene is 1.5-2:1, the reaction temperature is 80-90℃, and the pressure is 8-10 bar.

[0031] The circulation pump's circulation rate should ensure a circulation-to-production ratio greater than 100. Simultaneously, the flow velocity at the cross-flow filter 27 should be sufficient to flush away all palladium on carbon, preventing its accumulation on the filter screen. Turbulence-inducing and baffle components are added to reactor section 1 to minimize short-circuiting of the reaction liquid.

[0032] This embodiment also provides a continuous palladium-carbon hydrogenation reaction apparatus. This reaction apparatus is applied to the reaction method described above and mainly includes a reactor 1, a heat exchanger 7, a central tube 11, and a stirring mechanism 17. The top of the reactor 1 is provided with a top plate 2, and an injection port 5 is opened on the surface of the top plate 2. The heat exchanger 7 is installed on the surface of the reactor 1. A column 3 is installed at the bottom of the reactor 1, and a support plate 4 is installed at the bottom of the column 3. The central tube 11 is installed inside the reactor 1, and the stirring mechanism 17 is provided on the bottom side of the central tube 11. The heat exchange medium can be circulated through the heat exchanger and connected to a water bath circulation to perform heat exchange treatment on the reactor 1, ensuring the temperature stability throughout the reaction process. The heat exchanger 7's exchange efficiency is improved by utilizing the flow from bottom to top. The stirring mechanism 17 installed inside can achieve automatic stirring using the injected hydrogen and assist the heat exchanger 7 in performing an efficient heat exchange process.

[0033] In this embodiment, a hydrogen delivery pipe 6 is connected to one side of the bottom of the reactor 1, and a discharge pipe 25 is connected to the bottom of the reactor 1. A back pressure valve 26 and a filter 27 are installed on the surface of the discharge pipe 25. The other end of the hydrogen delivery pipe 6 is connected to the bottom of the central pipe 11. A reaction cavity 10 is provided inside the reactor 1. A support plate 8 is welded and installed on one side of the outer shell at the bottom of the reactor 1. A pressure pump 9 is installed on the top of the support plate 8. The heat exchanger 7 includes a heat-conducting plate 12 and a heat exchange medium circulation pipe 14. The heat-conducting plate 12 is attached to the surface of the outer shell of the reactor 1. A heat exchange medium injection pipe 13 and a heat exchange medium return pipe 14 are respectively provided at both ends of the heat exchange medium circulation pipe 14. The heat exchange medium injection pipe 13 is connected to the pressure pump 9 via the flow pipe 15. Specifically, the pressure pump 9 transports the heat exchange medium from the heat exchange medium injection pipe 13 to the inside of the heat exchange medium circulation pipe 14, and exchanges heat inside the reactor 1 through the heat-conducting plate 12, ensuring that the solution temperature inside the reactor 1 remains stable. Furthermore, by flowing from bottom to top, and in conjunction with the inner central pipe 11, the reaction solution can always accumulate in the area near the inner wall of the reaction cavity 10, further improving the heat exchange efficiency of the heat exchanger 7. Finally, the heat exchange medium is transported from the top heat exchange medium return pipe 15 back to the heat exchange medium injection pipe 13 through the pressure pump 9.

[0034] In this embodiment, a diversion chamber 16 is provided on the inner side of the bottom of the central tube 11. The stirring mechanism 17 is installed on the outer side of the diversion chamber 16, and a rotating drum 19 is provided in the middle of the stirring mechanism 17. A pressure chamber 23 is provided inside the rotating drum 19. One end of the pressure chamber 23 is connected to a diversion pipe 18. One end of the diversion pipe 18 is movably connected to the inner wall of the reactor 1 through a bearing 22, and the other end of the diversion pipe 18 is movably connected to the bottom surface of the central tube 11 through a bearing 22. The interior of the diversion pipe 18 is connected to the interior of the diversion chamber 16. The inner side of the rotating drum 19 is provided with a diversion chamber 16. A guide port 24 is provided, and an air hole 20 is opened on the outer side of the guide port 24. An agitator 21 is welded and installed on the surface of the rotating drum 19. Hydrogen gas is injected into the interior of the reactor 1 from the hydrogen gas delivery pipe 6 at the bottom and directly into the diversion chamber 16. Inside the diversion chamber 16, it is transmitted to the agitation mechanisms 17 on both sides. It is discharged to the outside through the guide port 24 and the air hole 20 inside the agitation mechanism 17. The guide port 24 can provide a reverse thrust to the rotating sleeve when the hydrogen gas is discharged to the outside, so that the rotating drum 19 can rotate, thereby providing a stirring and mixing effect to the reaction solution injected inside.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A continuous palladium-carbon hydrogenation reaction apparatus, characterized in that: The reactor (1) includes a reactor (1), a heat exchanger (7), a central tube (11), and a stirring mechanism (17). A top plate (2) is provided on the top of the reactor (1), and an injection port (5) is opened on the surface of the top plate (2). A heat exchanger (7) is installed on the surface of the reactor (1). A column (3) is installed at the bottom of the reactor (1), and a support plate (4) is installed at the bottom of the column (3). A central tube (11) is installed inside the reactor (1), and a stirring mechanism (17) is provided on the bottom side of the central tube (11). A hydrogen delivery pipe (6) is connected to one side of the bottom of the reactor (1), and a discharge pipe (25) is connected to the bottom of the reactor (1). A back pressure valve (26) and a filter (27) are installed on the surface of the discharge pipe (25). The other end of the hydrogen delivery pipe (6) is connected to the bottom of the central tube (11). The reactor (1) contains... The reaction cavity (10) has a flow distribution chamber (16) on the inner side of the bottom of the central tube (11). The stirring mechanism (17) is installed on the outer side of the flow distribution chamber (16), and a rotating drum (19) is set in the middle of the stirring mechanism (17). A pressure chamber (23) is set inside the rotating drum (19). One end of the pressure chamber (23) is connected to a flow distribution pipe (18). One end of the flow distribution pipe (18) is movably connected to the inner wall of the reactor (1) through a bearing (22). The other end of the flow distribution pipe (18) is movably connected to the surface of the bottom of the central tube (11) through a bearing (22). The interior of the flow distribution pipe (18) is connected to the interior of the flow distribution chamber (16). A guide port (24) is opened on the inner side of the rotating drum (19), and an air hole (20) is opened on the outer side of the guide port (24). A stirring rod (21) is welded and installed on the surface of the rotating drum (19).

2. The continuous palladium-carbon hydrogenation reactor according to claim 1, characterized in that: A support plate (8) is welded and installed on one side of the bottom shell of the reactor (1), and a pressure pump (9) is installed on the top of the support plate (8). The heat exchanger (7) includes a heat-conducting plate (12) and a heat exchange medium circulation pipeline (14).

3. The continuous palladium-carbon hydrogenation reaction apparatus according to claim 2, characterized in that: The heat-conducting plate (12) is attached to the surface of the outer shell of the reactor (1). The two ends of the heat exchange medium circulation pipeline (14) are respectively provided with a heat exchange medium injection pipeline (13) and a heat exchange medium return pipeline (15). The heat exchange medium injection pipeline (13) is partially connected to the pressure pump (9).

4. A method for continuous palladium-carbon hydrogenation reaction using the continuous palladium-carbon hydrogenation reaction apparatus as described in claim 1, characterized in that, The following steps are performed: Step 1: Mix the carbon catalyst with the solvent and then inject it into the reactor (1); Step 2: Connect and start the circulation pump to circulate the catalyst inside; Step 3: Inject p-nitrotoluene and hydrogen gas, and use the heat exchanger (7) to heat the entire reactor (1) so that the temperature remains stable during the reaction; Step 4: Discharge the reaction liquid and perform filtration.

5. The continuous palladium-on-carbon hydrogenation reaction method according to claim 4, characterized in that: The p-nitrotoluene is dissolved in an alcohol solvent and enters from the top of the reactor (1), while hydrogen enters from the bottom of the reactor (1). The volume ratio of the alcohol solvent to p-nitrotoluene is 7-10:1, the molar ratio of hydrogen to p-nitrotoluene is 1.5-2:1, and the reaction temperature is 80-90℃ and the pressure is 8-10 bar.

6. The continuous palladium-on-carbon hydrogenation reaction method according to claim 4, characterized in that: In step four, the reaction liquid is discharged through the filter (27), and a back pressure valve (26) is installed on the discharge pipeline (25). The pressure inside the reactor (1) and the discharge pipeline (25) is controlled by the back pressure valve (26).

7. The continuous palladium-on-carbon hydrogenation reaction method according to claim 5, characterized in that: The circulation and extraction ratio is controlled by a circulation pump to be greater than 100, and the reactor (1) is blocked by a flow disruptor and baffles.

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