Device system and method for catalytic hydrogenation of polychlorobenzene

Abstract

The invention provides a device system and a method for catalytic hydrogenation of polychlorobenzene. The device system comprises a rectification unit, a hydrogenation unit and a gas-liquid separation unit which are mutually coupled, the rectification unit is used for separating polychlorobenzene with different boiling points; the hydrogenation unit comprises at least two stages of hydrogenation reactors and is used for respectively carrying out catalytic hydrogenation on polychlorobenzene with different boiling points; the gas-liquid separation unit comprises at least two stages of gas-liquid separators which are respectively connected to the corresponding hydrogenation reactors. The method comprises the following steps: (1) introducing polychlorobenzene into a rectification unit for separation to obtain polychlorobenzene with different boiling points; (2) respectively carrying out catalytic hydrogenation on the polychlorobenzene with different boiling points by utilizing a hydrogenation unit; and (3) carrying out gas-liquid separation on the product obtained by the hydrogenation unit by using a gas-liquid separation unit to obtain benzene, chlorobenzene and dichlorobenzene. The method provided by the invention avoids backmixing, reduces energy consumption and operation cost, improves the conversion rate of polychlorobenzene and the selectivity of the target product, and can be popularized and applied on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic hydrogenation, and relates to a method for catalytic hydrogenation of polychlorinated benzenes, and in particular to a device system and method for catalytic hydrogenation of polychlorinated benzenes. Background Art

[0002] As basic chemical raw materials, chlorobenzene and dichlorobenzene compounds are widely used in the fields of solvents, medicines, pesticides, dyes, organic synthesis, polymer materials, etc., and play an important role in the national economy and social development. Chlorobenzene compounds are generally produced by directional chlorination of benzene. Since the chlorination reaction is non-selective, the chlorination process will produce not only dichlorobenzene, but also trichlorobenzene, tetrachlorobenzene and even pentachlorobenzene, which have few uses and small market capacity. Low-value polychlorobenzene products.

[0003] The general method of treating polychlorinated benzenes is direct incineration, but a large amount of HCl will be produced during the incineration process. Therefore, it is of great significance to study the hydrodechlorination of polychlorinated benzenes to produce high value-added compounds such as benzene, chlorobenzene and dichlorobenzene.

[0004] Traditional catalytic hydrogenation of polychlorinated benzene adopts kettle hydrogenation, which requires the addition of acid binding agents and produces a large amount of salt-containing wastewater. At the same time, kettle reactors have disadvantages such as back mixing, high labor intensity, and unstable product quality, and there is still much room for improvement.

[0005] CN114057537A discloses a method for catalytic hydrodechlorination of polychlorobenzenes, which uses toluene as solvent and palladium carbon as catalyst to carry out mixed polychlorobenzene hydrodechlorination reaction in a fixed bed reactor, with a polychlorobenzene conversion rate of up to 100%, and the products are benzene and chlorobenzene. However, the above method uses toluene as solvent, and toluene needs to be recycled after the reaction, which increases unit operation, solvent and energy consumption.

[0006] It can be seen that how to provide a device system and method for catalytic hydrogenation of polychlorinated benzenes to avoid backmixing, reduce energy consumption and operating costs, and improve the conversion rate of polychlorinated benzenes and the selectivity of target products has become an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a device system and method for catalytic hydrogenation of polychlorinated benzenes, which avoids backmixing, reduces energy consumption and operating costs, improves the conversion rate of polychlorinated benzenes and the selectivity of target products, and can be promoted and applied on a large scale.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a device system for catalytic hydrogenation of polychlorinated benzenes, the device system comprising a distillation unit, a hydrogenation unit and a gas-liquid separation unit coupled to each other.

[0010] The distillation unit is used to separate polychlorinated benzenes with different boiling points.

[0011] The hydrogenation unit comprises at least two stages of hydrogenation reactors for catalytically hydrogenating polychlorinated benzenes with different boiling points.

[0012] The gas-liquid separation unit includes at least two stages of gas-liquid separators, which are respectively connected to corresponding hydrogenation reactors.

[0013] The device system provided by the present invention improves the operation cycle of the device and the flexibility of catalytic hydrogenation of different polychlorinated benzenes through the design of a distillation unit and at least two-stage hydrogenation reactors, avoids the use of acid binding agents required for traditional kettle hydrogenation, reduces operation costs, reduces the generation of salt-containing wastewater, prevents environmental pollution, significantly improves the conversion rate of polychlorinated benzenes and the selectivity of benzene, chlorobenzene and dichlorobenzene, thereby producing high value-added products, achieving the dual goals of efficient resource utilization and environmental protection, and is conducive to large-scale promotion and application.

[0014] Preferably, the distillation unit comprises a distillation tower, and the tower top is used to produce trichlorobenzene and tetrachlorobenzene with low boiling points, and the tower bottom is used to produce pentachlorobenzene and hexachlorobenzene with high boiling points.

[0015] Preferably, the hydrogenation unit comprises two-stage hydrogenation reactors, namely a first hydrogenation reactor and a second hydrogenation reactor.

[0016] Preferably, the feed inlet of the first hydrogenation reactor is connected to the bottom discharge port of the distillation tower.

[0017] Preferably, the feed inlet of the second hydrogenation reactor is connected to the top discharge port of the distillation tower.

[0018] Preferably, the gas-liquid separation unit comprises two stages of gas-liquid separators, namely a first gas-liquid separator and a second gas-liquid separator.

[0019] Preferably, the feed port of the first gas-liquid separator is connected to the discharge port of the first hydrogenation reactor.

[0020] Preferably, the liquid phase outlet of the first gas-liquid separator is connected to the feed inlet of the first hydrogenation reactor.

[0021] Preferably, the gas phase outlet of the first gas-liquid separator is connected to the feed inlet of the second hydrogenation reactor.

[0022] Preferably, the feed port of the second gas-liquid separator is connected to the discharge port of the second hydrogenation reactor.

[0023] Preferably, the liquid phase outlet of the second gas-liquid separator is connected to the feed inlet of the second hydrogenation reactor.

[0024] Preferably, the gas phase discharge port of the second gas-liquid separator produces benzene, chlorobenzene and dichlorobenzene.

[0025] In a second aspect, the present invention provides a method for catalytic hydrogenation of polychlorinated benzenes using the device system as described in the first aspect, the method comprising the following steps:

[0026] (1) passing polychlorinated benzenes into a distillation unit for separation to obtain polychlorinated benzenes with different boiling points;

[0027] (2) using a hydrogenation unit to catalytically hydrogenate polychlorinated benzenes with different boiling points;

[0028] (3) The gas-liquid separation unit is used to separate the product obtained from the hydrogenation unit into gas and liquid to obtain benzene, chlorobenzene and dichlorobenzene.

[0029] Preferably, step (1) comprises: passing polychlorobenzenes into a distillation tower for separation, taking out trichlorobenzene and tetrachlorobenzene with low boiling points from the top of the tower, and taking out pentachlorobenzene and hexachlorobenzene with high boiling points from the bottom of the tower.

[0030] Preferably, the pressure inside the distillation tower is 1-10 kPaA, for example, it may be 1 kPaA, 2 kPaA, 3 kPaA, 4 kPaA, 5 kPaA, 6 kPaA, 7 kPaA, 8 kPaA, 9 kPaA or 10 kPaA, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, step (2) comprises: passing the polychlorinated benzenes extracted from the bottom of the tower into a first hydrogenation reactor for a first catalytic hydrogenation, and simultaneously passing the polychlorinated benzenes extracted from the top of the tower into a second hydrogenation reactor for a second catalytic hydrogenation.

[0032] Preferably, in the first catalytic hydrogenation process, the mass ratio of hydrogen to polychlorinated benzenes is 1:(10-30), for example, it can be 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28 or 1:30, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, during the first catalytic hydrogenation process, the weight hourly space velocity of polychlorinated benzene is 0.1-5h -1 , for example, it can be 0.1h -1 、0.5h -1 , 1h -1 , 1.5h -1 , 2h -1 , 2.5h-1 , 3h -1 , 3.5h -1 , 4h -1 , 4.5h -1 or 5h -1 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the reaction temperature of the first catalytic hydrogenation is 180-260°C, for example, it can be 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or 260°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the reaction pressure of the first catalytic hydrogenation is 0.5-5 MPaG, for example, it can be 0.5 MPaG, 1 MPaG, 1.5 MPaG, 2 MPaG, 2.5 MPaG, 3 MPaG, 3.5 MPaG, 4 MPaG, 4.5 MPaG or 5 MPaG, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the catalyst used in the first catalytic hydrogenation comprises an activated carbon-supported active metal catalyst, wherein the active metal comprises a Group VIB metal and / or a Group VIII metal, and the active metal accounts for 2-5% of the weight of the carrier, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, in the second catalytic hydrogenation process, the mass ratio of hydrogen to polychlorinated benzenes is 1:(5-20), for example, 1:5, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18 or 1:20, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, during the second catalytic hydrogenation process, the weight hourly space velocity of polychlorinated benzene is 0.5-10h -1 , for example, it can be 0.5h -1 , 1h -1 , 2h -1 , 3h -1 , 4h -1 , 5h -1 , 6h -1 , 7h -1 , 8h -1 , 9h -1 or 10h -1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the reaction temperature of the second catalytic hydrogenation is 80-200°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the reaction pressure of the second catalytic hydrogenation is 0.1-2 MPaG, for example, it can be 0.1 MPaG, 0.2 MPaG, 0.4 MPaG, 0.6 MPaG, 0.8 MPaG, 1 MPaG, 1.2 MPaG, 1.4 MPaG, 1.6 MPaG, 1.8 MPaG or 2 MPaG, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] Preferably, the catalyst used in the second catalytic hydrogenation comprises an activated carbon-supported active metal catalyst, wherein the active metal comprises a Group VIB metal and / or a Group VIII metal, and the active metal accounts for 0.5-2% of the weight of the carrier, for example, it can be 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, step (3) comprises: passing the product obtained from the first hydrogenation reactor into a first gas-liquid separator for a first gas-liquid separation, returning the obtained liquid phase to the first hydrogenation reactor for recycling, and passing the obtained gas phase into a second hydrogenation reactor; and simultaneously passing the product obtained from the second hydrogenation reactor into a second gas-liquid separator for a second gas-liquid separation, returning the obtained liquid phase to the second hydrogenation reactor for recycling, and the obtained gas phase is benzene, chlorobenzene and dichlorobenzene.

[0043] Preferably, the temperature of the first gas-liquid separation is 150-220°C, for example, it can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the temperature of the second gas-liquid separation is 110-180°C, for example, it can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The device system provided by the present invention improves the operation cycle of the device and the flexibility of catalytic hydrogenation of different polychlorinated benzenes through the design of a distillation unit and at least two-stage hydrogenation reactors, avoids the use of acid binding agents required for traditional kettle hydrogenation, reduces operation costs, reduces the generation of salt-containing wastewater, prevents environmental pollution, significantly improves the conversion rate of polychlorinated benzenes and the selectivity of benzene, chlorobenzene and dichlorobenzene, thereby producing high value-added products, achieving the dual goals of efficient resource utilization and environmental protection, and is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention provides a schematic diagram of the structure of a device system for catalytic hydrogenation of polychlorinated benzenes.

[0049] Among them: 10-distillation unit; 20-hydrogenation unit; 21-first hydrogenation reactor; 22-second hydrogenation reactor; 30-gas-liquid separation unit; 31-first gas-liquid separator; 32-second gas-liquid separator. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] The present invention provides a device system for catalytic hydrogenation of polychlorinated benzenes, such as Figure 1 As shown, the device system includes a distillation unit 10, a hydrogenation unit 20 and a gas-liquid separation unit 30 which are coupled to each other. The distillation unit 10 is used to separate polychlorinated benzenes with different boiling points; the hydrogenation unit 20 includes two-stage hydrogenation reactors, namely a first hydrogenation reactor 21 and a second hydrogenation reactor 22, which are used to catalytically hydrogenate polychlorinated benzenes with different boiling points; the gas-liquid separation unit 30 includes two-stage gas-liquid separators, namely a first gas-liquid separator 31 and a second gas-liquid separator 32, which are respectively connected to the corresponding hydrogenation reactors.

[0052] In the present invention, the distillation unit 10 comprises a distillation tower, and the tower top is used to produce trichlorobenzene and tetrachlorobenzene with low boiling points, and the tower bottom is used to produce pentachlorobenzene and hexachlorobenzene with high boiling points.

[0053] In the present invention, the feed port of the first hydrogenation reactor 21 is connected to the bottom discharge port of the distillation tower, and the feed port of the second hydrogenation reactor 22 is connected to the top discharge port of the distillation tower; the feed port of the first gas-liquid separator 31 is connected to the discharge port of the first hydrogenation reactor 21, the liquid phase discharge port is connected to the feed port of the first hydrogenation reactor 21, and the gas phase discharge port is connected to the feed port of the second hydrogenation reactor 22; the feed port of the second gas-liquid separator 32 is connected to the discharge port of the second hydrogenation reactor 22, the liquid phase discharge port is connected to the feed port of the second hydrogenation reactor 22, and the gas phase discharge port produces benzene, chlorobenzene and dichlorobenzene.

[0054] Example 1

[0055] This embodiment provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, which specifically includes the following steps:

[0056] (1) passing polychlorobenzenes into a distillation tower for separation, controlling the pressure in the tower to be 5 kPaA, extracting trichlorobenzene and tetrachlorobenzene with low boiling points from the top of the tower, and extracting pentachlorobenzene and hexachlorobenzene with high boiling points from the bottom of the tower;

[0057] (2) The polychlorinated benzenes extracted from the bottom of the tower are introduced into a first hydrogenation reactor 21 for a first catalytic hydrogenation, and the polychlorinated benzenes extracted from the top of the tower are introduced into a second hydrogenation reactor 22 for a second catalytic hydrogenation; wherein, during the first catalytic hydrogenation, the mass ratio of hydrogen to polychlorinated benzenes is 1:20, and the weight hourly space velocity of polychlorinated benzenes is 2.5 h -1 , the reaction temperature is 220°C, the reaction pressure is 2MPaG, the catalyst used in the first catalytic hydrogenation is activated carbon supported palladium, and the palladium accounts for 3% of the weight of the carrier; in the second catalytic hydrogenation process, the mass ratio of hydrogen to polychlorinated benzene is 1:10, and the weight hourly space velocity of polychlorinated benzene is 5h -1 , the reaction temperature is 140° C., the reaction pressure is 0.4 MPaG, the catalyst used in the second catalytic hydrogenation is activated carbon-supported palladium, and the palladium accounts for 1% of the weight of the carrier;

[0058] (3) The product obtained from the first hydrogenation reactor 21 is passed into the first gas-liquid separator 31, and the first gas-liquid separation is performed at 180° C. The obtained liquid phase is returned to the first hydrogenation reactor 21 for recycling, and the obtained gas phase is passed into the second hydrogenation reactor 22; at the same time, the product obtained from the second hydrogenation reactor 22 is passed into the second gas-liquid separator 32, and the second gas-liquid separation is performed at 150° C., and the obtained liquid phase is returned to the second hydrogenation reactor 22 for recycling, and the obtained gas phase is benzene, chlorobenzene and dichlorobenzene.

[0059] In this embodiment, the composition of the polychlorobenzenes in step (1) is 20.46wt% trichlorobenzene, 24.68wt% tetrachlorobenzene, 28.65% pentachlorobenzene and 26.21% hexachlorobenzene, and the feed flow rate is 2kg / h; the discharge flow rate of the target product obtained in step (3) is 1.26kg / h, and the specific composition is 92.40wt% dichlorobenzene, 7.07wt% chlorobenzene and 0.53wt% benzene, and the yield decreases after 3260h of stable operation, the system cannot maintain stability, and the catalyst is deactivated.

[0060] Embodiment 2-5

[0061] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the pressure inside the distillation tower. The remaining steps and conditions are the same as those in Embodiment 1, and therefore will not be described in detail here.

[0062] The relevant results of this group of examples are shown in Table 1 below.

[0063] Table 1

[0064]

[0065] Embodiment 6-9

[0066] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the mass ratio of hydrogen to polychlorinated benzenes in the first catalytic hydrogenation process is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0067] The relevant results of this group of examples are shown in Table 2 below.

[0068] Table 2

[0069]

[0070] Examples 10-13

[0071] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the reaction temperature of the first catalytic hydrogenation. The remaining steps and conditions are the same as those in Example 1, and therefore will not be described in detail here.

[0072] The relevant results of this group of examples are shown in Table 3 below.

[0073] Table 3

[0074]

[0075] Examples 14-16

[0076] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the type of supported metal of the catalyst used in the first catalytic hydrogenation is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0077] The relevant results of this group of examples are shown in Table 4 below.

[0078] Table 4

[0079]

[0080] Examples 17-19

[0081] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the metal loading amount of the catalyst used in the first catalytic hydrogenation is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0082] The relevant results of this group of examples are shown in Table 5 below.

[0083] Table 5

[0084]

[0085] Examples 20-23

[0086] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the weight hourly space velocity of polychlorinated benzenes in the first catalytic hydrogenation process is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0087] The relevant results of this group of examples are shown in Table 6 below.

[0088] Table 6

[0089]

[0090]

[0091] Examples 24-27

[0092] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the reaction pressure of the first catalytic hydrogenation. The remaining steps and conditions are the same as those in Example 1, and therefore will not be described in detail here.

[0093] The relevant results of this group of examples are shown in Table 7 below.

[0094] Table 7

[0095]

[0096] Examples 28-29

[0097] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the temperature of the first gas-liquid separation. The remaining steps and conditions are the same as those in Example 1, so they will not be described in detail here.

[0098] The relevant results of this group of examples are shown in Table 8 below.

[0099] Table 8

[0100]

[0101]

[0102] Examples 30-32

[0103] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the mass ratio of hydrogen to polychlorinated benzenes in the second catalytic hydrogenation process is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0104] The relevant results of this group of examples are shown in Table 9 below.

[0105] Table 9

[0106]

[0107] Examples 33-36

[0108] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the reaction temperature of the second catalytic hydrogenation. The remaining steps and conditions are the same as those in Example 1, so they will not be described in detail here.

[0109] The relevant results of this group of examples are shown in Table 10 below.

[0110] Table 10

[0111]

[0112] Examples 37-39

[0113] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference is that the type of supported metal of the catalyst used in the second catalytic hydrogenation is different, and the remaining steps and conditions are the same as those in Example 1, so they are not repeated here.

[0114] The relevant results of this group of examples are shown in Table 11 below.

[0115] Table 11

[0116]

[0117] Examples 40-42

[0118] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the metal loading amount of the catalyst used in the second catalytic hydrogenation is different, and the remaining steps and conditions are the same as those in Example 1, so they are not repeated here.

[0119] The relevant results of this group of examples are shown in Table 12 below.

[0120] Table 12

[0121]

[0122] Examples 43-46

[0123] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the weight hourly space velocity of polychlorinated benzenes in the second catalytic hydrogenation process is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0124] The relevant results of this group of examples are shown in Table 13 below.

[0125] Table 13

[0126]

[0127] Examples 47-49

[0128] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the reaction pressure of the second catalytic hydrogenation. The remaining steps and conditions are the same as those in Example 1, and therefore will not be described in detail here.

[0129] The relevant results of this group of examples are shown in Table 14 below.

[0130] Table 14

[0131]

[0132] Examples 50-51

[0133] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being the temperature of the second gas-liquid separation. The remaining steps and conditions are the same as those in Example 1, so they will not be described in detail here.

[0134] The relevant results of this group of examples are shown in Table 15 below.

[0135] Table 15

[0136]

[0137] Examples 52-53

[0138] This group of embodiments respectively provides a method for catalytic hydrogenation of polychlorinated benzenes using the above-mentioned device system, the only difference being that the composition of the polychlorinated benzenes described in step (1) is different, and the remaining steps and conditions are the same as those in Example 1, so they are not described here in detail.

[0139] The relevant results of this group of examples are shown in Table 16 below.

[0140] Table 16

[0141]

[0142] It can be seen that the device system provided by the present invention improves the operation cycle of the device and the flexibility of catalytic hydrogenation of different polychlorinated benzenes through the design of the distillation unit and at least two-stage hydrogenation reactors, avoids the use of acid binding agents required for traditional kettle hydrogenation, reduces operating costs, reduces the generation of salt-containing wastewater, prevents environmental pollution, and significantly improves the conversion rate of polychlorinated benzenes and the selectivity of benzene, chlorobenzene and dichlorobenzene, thereby producing high value-added products, achieving the dual goals of efficient utilization of resources and environmental protection, and is conducive to large-scale promotion and application.

[0143] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A device system for catalytic hydrogenation of polychlorinated benzenes, characterized in that: The device system comprises a distillation unit, a hydrogenation unit and a gas-liquid separation unit which are coupled to each other; The distillation unit is used to separate polychlorinated benzenes with different boiling points; The hydrogenation unit comprises at least two stages of hydrogenation reactors for catalytically hydrogenating polychlorinated benzenes with different boiling points respectively; The gas-liquid separation unit includes at least two stages of gas-liquid separators, which are respectively connected to corresponding hydrogenation reactors.

2. The device system according to claim 1, characterized in that: The distillation unit comprises a distillation tower, wherein the tower top is used to produce trichlorobenzene and tetrachlorobenzene with low boiling points, and the tower bottom is used to produce pentachlorobenzene and hexachlorobenzene with high boiling points; Preferably, the hydrogenation unit comprises two-stage hydrogenation reactors, namely a first hydrogenation reactor and a second hydrogenation reactor; Preferably, the feed inlet of the first hydrogenation reactor is connected to the bottom discharge port of the distillation tower; Preferably, the feed inlet of the second hydrogenation reactor is connected to the top discharge port of the distillation tower.

3. The device system according to claim 1 or 2, characterized in that: The gas-liquid separation unit comprises two-stage gas-liquid separators, namely a first gas-liquid separator and a second gas-liquid separator; Preferably, the feed port of the first gas-liquid separator is connected to the discharge port of the first hydrogenation reactor; Preferably, the liquid phase outlet of the first gas-liquid separator is connected to the feed inlet of the first hydrogenation reactor; Preferably, the gas phase outlet of the first gas-liquid separator is connected to the feed inlet of the second hydrogenation reactor; Preferably, the feed port of the second gas-liquid separator is connected to the discharge port of the second hydrogenation reactor; Preferably, the liquid phase outlet of the second gas-liquid separator is connected to the feed inlet of the second hydrogenation reactor; Preferably, the gas phase discharge port of the second gas-liquid separator produces benzene, chlorobenzene and dichlorobenzene.

4. A method for catalytic hydrogenation of polychlorinated benzenes using the device system as described in any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) passing polychlorinated benzenes into a distillation unit for separation to obtain polychlorinated benzenes with different boiling points; (2) using a hydrogenation unit to catalytically hydrogenate polychlorinated benzenes with different boiling points; (3) Using a gas-liquid separation unit to separate the product obtained from the hydrogenation unit into gas and liquid to obtain benzene, chlorobenzene and dichlorobenzene.

5. The method according to claim 4, characterized in that Step (1) comprises: passing polychlorobenzenes into a distillation tower for separation, taking out trichlorobenzene and tetrachlorobenzene with low boiling points from the top of the tower, and taking out pentachlorobenzene and hexachlorobenzene with high boiling points from the bottom of the tower; Preferably, the internal pressure of the distillation tower is 1-10 kPaA.

6. The method according to claim 5, characterized in that Step (2) comprises: passing the polychlorinated benzenes extracted from the bottom of the tower into a first hydrogenation reactor for a first catalytic hydrogenation, and simultaneously passing the polychlorinated benzenes extracted from the top of the tower into a second hydrogenation reactor for a second catalytic hydrogenation.

7. The method according to claim 6, characterized in that In the first catalytic hydrogenation process, the mass ratio of hydrogen to polychlorinated benzene is 1:(10-30), and the weight hourly space velocity of polychlorinated benzene is 0.1-5h -1 ; Preferably, the reaction temperature of the first catalytic hydrogenation is 180-260°C and the reaction pressure is 0.5-5MPaG; Preferably, the catalyst used in the first catalytic hydrogenation comprises an activated carbon-supported active metal catalyst, wherein the active metal comprises a Group VIB metal and / or a Group VIII metal, and the active metal accounts for 2-5% of the weight of the carrier.

8. The method according to claim 6 or 7, characterized in that: In the second catalytic hydrogenation process, the mass ratio of hydrogen to polychlorinated benzene is 1:(5-20), and the weight hourly space velocity of polychlorinated benzene is 0.5-10h -1 ; Preferably, the reaction temperature of the second catalytic hydrogenation is 80-200°C and the reaction pressure is 0.1-2MPaG; Preferably, the catalyst used in the second catalytic hydrogenation comprises an activated carbon-supported active metal catalyst, wherein the active metal comprises a Group VIB metal and / or a Group VIII metal, and the active metal accounts for 0.5-2% of the weight of the carrier.

9. The method according to any one of claims 6 to 8, characterized in that: Step (3) comprises: passing the product obtained from the first hydrogenation reactor into a first gas-liquid separator for a first gas-liquid separation, returning the obtained liquid phase to the first hydrogenation reactor for recycling, and passing the obtained gas phase into a second hydrogenation reactor; and passing the product obtained from the second hydrogenation reactor into a second gas-liquid separator for a second gas-liquid separation, returning the obtained liquid phase to the second hydrogenation reactor for recycling, and the obtained gas phase is benzene, chlorobenzene and dichlorobenzene.

10. The method according to claim 9, characterized in that The temperature of the first gas-liquid separation is 150-220°C; Preferably, the temperature of the second gas-liquid separation is 110-180°C.

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