Methods and systems for dichlorobenzene isomer separation

Abstract

The invention provides a method for separating dichlorobenzene isomers, which comprises the following steps of: pretreating the dichlorobenzene isomers, removing hydrogen chloride and tar in the dichlorobenzene isomers by combining multiple times of rectification, adsorption and desorption and multiple times of crystallization, and separating three isomers in the dichlorobenzene isomers to obtain m-dichlorobenzene, o-dichlorobenzene and p-dichlorobenzene with higher purity. The invention also provides a system for separating dichlorobenzene isomers. The method and system can be used for dichlorobenzene isomer separation, m-dichlorobenzene, p-dichlorobenzene and o-dichlorobenzene with high purity are obtained through separation, and efficient separation of m-dichlorobenzene, p-dichlorobenzene and o-dichlorobenzene is achieved.

Description

Technical Field

[0001] The invention belongs to the field of material separation, and in particular relates to a method and a system for separating dichlorobenzene isomers. Background Art

[0002] The traditional method of separating dichlorobenzene isomers is a method combining crystallization and rectification. This method is to separate p-dichlorobenzene from a mixture of dichlorobenzene isomers by crystallization, rectify the crystallization mother liquor to obtain the heavy component o-dichlorobenzene, recrystallize the distillate to precipitate p-dichlorobenzene and obtain a mother liquor enriched in m-dichlorobenzene, rectify the mother liquor enriched in m-dichlorobenzene to obtain the distillate m-dichlorobenzene. The m-dichlorobenzene obtained by this method has low purity, low separation efficiency, and high cost. Since the boiling points of p-dichlorobenzene and m-dichlorobenzene are very close, it is difficult to achieve effective separation. Summary of the invention

[0003] The first object of the present invention is to provide a method for separating dichlorobenzene isomers, which can achieve the separation of p-dichlorobenzene isomers.

[0004] The second object of the present invention is to provide a system for separating dichlorobenzene isomers in the above method, wherein the system can achieve the separation of p-dichlorobenzene isomers.

[0005] To achieve the first object of the present invention, the following technical solutions are adopted:

[0006] A method for separating dichlorobenzene isomers, wherein the dichlorobenzene isomers include at least chlorobenzene, tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0007] The method comprises the following steps:

[0008] (1) pre-treating the dichlorobenzene isomers and then performing distillation to remove light components, thereby removing light components including chlorobenzene and outputting heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0009] (2) subjecting the heavy components obtained in step (1) to distillation to remove the heavy components including tar, and outputting the light components including p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0010] (3) sending the light component obtained in step (2) to an adsorption device to adsorb and retain the p-dichlorobenzene therein, and outputting a raffinate containing o-dichlorobenzene and m-dichlorobenzene;

[0011] (4) distilling the raffinate obtained in step (3) to remove light components, remove light components including chlorobenzene, and output heavy components including o-dichlorobenzene and m-dichlorobenzene;

[0012] (5) distilling the heavy component obtained in step (3) to separate meta-dichlorobenzene, and outputting the heavy component containing ortho-dichlorobenzene;

[0013] (6) distilling the heavy components obtained in step (5) to remove the heavy components including tar and output o-dichlorobenzene;

[0014] (7) introducing the desorbent into the adsorption device in step (3) to dissolve and then desorb the adsorbed p-dichlorobenzene to form a desorbed liquid for output;

[0015] (8) distilling the desorbed liquid obtained in step (7) to remove light components, remove light components including chlorobenzene, and output heavy components including p-dichlorobenzene;

[0016] (9) subjecting the heavy components obtained in step (8) to distillation to remove the heavy components including tar, and outputting the light components enriched in p-dichlorobenzene;

[0017] (10) pre-crystallizing the light component obtained in step (9), and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor;

[0018] (11) heating and remelting the crude p-dichlorobenzene crystals obtained in step (10) in stages, obtaining a primary melt at 10-40° C. and returning the primary melt to the adsorption device in step (3), obtaining a secondary melt at 50-70° C. and performing primary crystallization, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor;

[0019] (12) remelting the primary p-dichlorobenzene crystals obtained in step (11) and performing secondary crystallization, outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor;

[0020] (13) The secondary p-dichlorobenzene crystals obtained in step (12) are sequentially subjected to heat melting, cooling and slicing to obtain p-dichlorobenzene.

[0021] The method for separating dichlorobenzene isomers of the present invention preferably comprises, in step (1), the pretreatment comprising sequentially preheating and flashing the dichlorobenzene isomers to obtain a gaseous material for use as a feed for a distillation device; preferably, the pretreatment further comprises performing oil-gas separation on the gaseous material obtained by flashing, extracting tar, and outputting a light component as a feed for a distillation device; preferably, in step (1), the preheating is performed in an evaporator buffer tank; the pretreatment further comprises returning the gaseous material obtained by flashing to the evaporator buffer tank for oil-gas separation, extracting tar from the bottom thereof, and outputting a light component as a feed for a distillation device from the top thereof.

[0022] The method for separating dichlorobenzene isomers of the present invention preferably further comprises, in step (2), condensing the light components outputted from the rectification device, and at least partially refluxing and / or at least partially withdrawing the obtained condensate for use as feed for the adsorption device in step (3).

[0023] The method for separating dichlorobenzene isomers of the present invention preferably further comprises, in step (7), cooling the desorption liquid outputted from the adsorption device;

[0024] Preferably, the condensate obtained in step (2) is first used as a cooling medium to heat and cool the desorbed liquid before being sent to the adsorption device, and the condensate itself is heated. Preferably, the heated condensate is subjected to gas-liquid separation to separate the gas containing chlorobenzene and the liquid containing p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene. The separated liquid is then heated and buffered in sequence before being used as feed for the adsorption device in step (3).

[0025] In the method for separating dichlorobenzene isomers of the present invention, preferably, in step (7), the desorbent is chlorobenzene; preferably, the method further comprises using the light components removed in any one or more of steps (1), (4) and (8) as a desorbent in step (7).

[0026] The method for separating dichlorobenzene isomers of the present invention preferably comprises:

[0027] In step (3), the raffinate outputted from the adsorption device is cooled before being distilled in step (4);

[0028] Preferably, in step (7), the temperature is first increased before the desorbent is introduced into the adsorption device;

[0029] Preferably, before the desorbent is introduced into the adsorption device in step (7), it is first used as a cooling medium to cool the residual liquid output from the adsorption device, while the desorbent itself is heated.

[0030] The method for separating dichlorobenzene isomers of the present invention preferably comprises:

[0031] The light component output from step (4) is first cooled and condensed before being used in step (7), and the obtained condensate is used as a desorbent in step (7); and / or

[0032] After the light components output from step (8) are condensed, the resulting condensate is at least partially refluxed and / or at least partially cooled and then used as a desorbent in step (7).

[0033] The method for separating dichlorobenzene isomers of the present invention preferably further comprises, in step (9), condensing the light components outputted from the rectification device, and at least partially refluxing the obtained condensate and / or at least partially using it as feed for the pre-crystallization device in step (10).

[0034] The method for separating dichlorobenzene isomers of the present invention preferably further comprises: returning the pre-crystallization mother liquor obtained in step (10) to the pre-crystallization device for cyclic crystallization; and / or

[0035] The method further comprises: returning the primary crystallization mother liquor obtained in step (11) to the pre-crystallization device for cyclic crystallization; and / or

[0036] The method further comprises: returning the secondary crystallization mother liquor obtained in step (12) to the primary crystallization device for cyclic crystallization.

[0037] To achieve the second object of the present invention, a system for separating dichlorobenzene isomers in the above method is provided.

[0038] The beneficial effects of the present invention are:

[0039] The meta-dichlorobenzene separated by the prior art has low purity, low separation effect, high separation cost, and since the boiling points of para-dichlorobenzene and meta-dichlorobenzene are very close, the two cannot be completely separated. The method and system for separating dichlorobenzene isomers of the present invention can overcome the above-mentioned technical problems existing in the prior art by organically combining distillation, crystallization and adsorption and desorption, and separate meta-dichlorobenzene, para-dichlorobenzene and o-dichlorobenzene with higher purity, thereby realizing efficient separation of the three. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The figure is a schematic flow diagram of a method for separating dichlorobenzene isomers according to the present invention in one embodiment. DETAILED DESCRIPTION

[0041] The technical scheme and its effects of the present invention are further described below in conjunction with specific implementation methods / examples. The following implementation methods / examples are only used to illustrate the content of the present invention, and the invention is not limited to the following implementation methods or examples. Simple changes made to the present invention using the concept of the present invention are all within the scope of protection claimed by the present invention.

[0042] like Figure 1 As shown, a method for separating dichlorobenzene isomers, wherein the dichlorobenzene isomers include at least chlorobenzene, tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0043] The method comprises the following steps:

[0044] (1) pre-treating the dichlorobenzene isomers and then performing distillation to remove light components, thereby removing light components including chlorobenzene and outputting heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0045] (2) subjecting the heavy components obtained in step (1) to distillation to remove the heavy components including tar, and outputting the light components including p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene;

[0046] (3) sending the light component obtained in step (2) to an adsorption device to adsorb and retain the p-dichlorobenzene therein, and outputting a raffinate containing o-dichlorobenzene and m-dichlorobenzene;

[0047] (4) distilling the raffinate obtained in step (3) to remove light components, remove light components including chlorobenzene, and output heavy components including o-dichlorobenzene and m-dichlorobenzene;

[0048] (5) distilling the heavy component obtained in step (3) to separate meta-dichlorobenzene, and outputting the heavy component containing ortho-dichlorobenzene;

[0049] (6) distilling the heavy components obtained in step (5) to remove the heavy components including tar and output o-dichlorobenzene;

[0050] (7) introducing the desorbent into the adsorption device in step (3) to dissolve and then desorb the adsorbed p-dichlorobenzene to form a desorbed liquid for output;

[0051] (8) distilling the desorbed liquid obtained in step (7) to remove light components, remove light components including chlorobenzene, and output heavy components including p-dichlorobenzene;

[0052] (9) subjecting the heavy components obtained in step (8) to distillation to remove the heavy components including tar, and outputting the light components enriched in p-dichlorobenzene;

[0053] (10) pre-crystallizing the light component obtained in step (9), and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor;

[0054] (11) heating and remelting the crude p-dichlorobenzene crystals obtained in step (10) in stages, obtaining a primary melt at 10-40° C. and returning the primary melt to the adsorption device in step (3), obtaining a secondary melt at 50-70° C. and performing primary crystallization, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor;

[0055] (12) remelting the primary p-dichlorobenzene crystals obtained in step (11) and performing secondary crystallization, outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor;

[0056] (13) The secondary p-dichlorobenzene crystals obtained in step (12) are sequentially subjected to heat melting, cooling and slicing to obtain p-dichlorobenzene.

[0057] Those skilled in the art understand that the distillation device in each step is a distillation tower, which is a commonly used distillation equipment, and a reboiler is provided at the bottom of the tower, and a condenser and reflux are provided at the top of the tower, which will not be described in detail here; the adsorption device is an adsorption tower, which is provided with an adsorption column, which is a commonly used adsorption device in the art; the pre-crystallization device, the primary crystallization device and the secondary crystallization device are all commonly used crystallization devices in the art, such as a crystallizer. In step (13), heat melting, cooling and slicing are carried out in a device commonly used in the art. The transportation between the devices is carried out by pumping.

[0058] Those skilled in the art understand that remelting is performed in remelting equipment commonly used in the art, such as a heating equipment.

[0059] In one embodiment, the remelting temperature of step (12) is 60-90°C, such as 60°C, 70°C, 80°C and 90°C and any value and numerical range within the range; and / or the hot melting temperature of step (13) is 60-90°C, such as 60°C, 70°C, 80°C and 90°C and any value and numerical range within the range; and / or the cooling temperature of step (13) is 30-40°C, such as 30°C, 35°C and 40°C and any value and numerical range within the range.

[0060] The method and system for separating dichlorobenzene isomers of the present invention can overcome the technical problems existing in the prior art by organically combining distillation, crystallization and adsorption and desorption, and can separate and obtain meta-dichlorobenzene, para-dichlorobenzene and ortho-dichlorobenzene with higher purity, thereby achieving efficient separation of the three.

[0061] Those skilled in the art will appreciate that the properties of the various components that may be present in dichlorobenzene isomers are shown in Table 1.

[0062] Table 1 Properties of the components in dichlorobenzene isomers

[0063]

[0064] As shown in Table 1, the boiling points of m-dichlorobenzene and p-dichlorobenzene are close, and it is difficult to separate them by distillation. However, their melting points are very different, so they can be separated by crystallization.

[0065] In order to improve the distillation and removal effect of step (1) and remove chlorobenzene as much as possible, in one embodiment, in step (1), the operating conditions of the distillation include: an operating temperature of 50 to 120°C, such as 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C and 120°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0066] In order to improve the distillation and de-weighting effect of step (2) and remove the tar as much as possible, in one embodiment, in step (2), the operating conditions of the distillation include: an operating temperature of 90 to 150°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C and 150°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0067] In order to improve the adsorption and retention effect of p-dichlorobenzene in step (3), in one embodiment, in step (3), the adsorption operating conditions of the adsorption device (i.e., adsorption device 3) include: an adsorption temperature of 190 to 220°C, such as 190°C, 200°C, 210°C and 220°C and any numerical value and numerical range within the range; an adsorption pressure of 0.1 to 0.5 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa and 0.5 MPa and any numerical value and numerical range within the range; the adsorption column is a jacketed packing column, and there are 3 to 8 adsorption columns, such as 3, 4, 5, 6, 7, 8, and they are arranged in parallel.

[0068] In order to improve the distillation and light removal effect of step (4) and remove chlorobenzene as much as possible, in one embodiment, in step (4), the operating conditions of the distillation include: an operating temperature of 60 to 120°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, 110°C and 120°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0069] In order to improve the distillation separation effect of step (5) and improve the purity of the separated meta-dichlorobenzene, in one embodiment, in step (5), the operating conditions of the distillation include: an operating temperature of 90 to 130°C, such as 90°C, 100°C, 110°C, 120°C and 130°C and any numerical value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any numerical value and numerical range within the range.

[0070] In order to improve the effect of deheaving and decoking of distillation in step (6) and improve the purity of separated o-dichlorobenzene, in one embodiment, in step (6), the operating conditions of distillation include: an operating temperature of 100 to 150°C, such as 100°C, 110°C, 120°C, 130°C, 140°C and 150°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0071] In order to improve the desorption effect of step (7), in one embodiment, in step (7), the desorption operating conditions of the adsorption device (i.e., the adsorption tower 3) include: a desorption temperature of 190-220°C, such as 190°C, 200°C, 210°C and 220°C and any value and numerical range within the range; a desorption pressure of 0.1-0.5MPa, such as 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa and 0.5MPa and any value and numerical range within the range.

[0072] In order to improve the distillation and removal effect of step (8) and remove chlorobenzene as much as possible, in one embodiment, in step (8), the operating conditions of the distillation include: an operating temperature of 50 to 120°C, such as 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C and 120°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0073] In order to improve the distillation and de-weighting effect of step (9) and remove the tar as much as possible, in one embodiment, in step (9), the operating conditions of the distillation include: an operating temperature of 90 to 150°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C and 150°C and any value and numerical range within the range; an operating pressure of -0.095 to -0.08MPa, such as -0.095MPa, -0.09MPa, -0.085MPa and -0.08MPa and any value and numerical range within the range.

[0074] In order to improve the pre-crystallization effect of step (10), in one embodiment, in step (10), the operating conditions of pre-crystallization include: an operating temperature of -10 to 90°C, such as -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C and 90°C and any value and numerical range within the range; an operating pressure of 0.2 to 0.6 MPa, such as 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa and 0.6 MPa and any value and numerical range within the range.

[0075] In order to improve the primary crystallization effect of step (11), in one embodiment, in step (11), the operating conditions of the primary crystallization include: an operating temperature of -10 to 90°C, such as -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C and 90°C and any value and numerical range within the range; an operating pressure of 0.2 to 0.6 MPa, such as 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa and 0.6 MPa and any value and numerical range within the range.

[0076] In order to improve the secondary crystallization effect of step (12), in one embodiment, in step (12), the operating conditions of the secondary crystallization include: an operating temperature of 10 to 90°C, such as 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C and 90°C and any value and numerical range within the range; an operating pressure of 0.2 to 0.6 MPa, such as 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa and 0.6 MPa and any value and numerical range within the range.

[0077] In one embodiment, in step (1), the pretreatment includes preheating and flashing the dichlorobenzene isomers in sequence to obtain a gaseous material for use as a feed for its distillation device (i.e., the first distillation tower 1); preferably preheating to 90-120°C, such as 90°C, 100°C, 110°C and 120°C and any numerical value and numerical range within the range; preferably flashing conditions include: an operating temperature of 90-120°C, such as 90°C, 100°C, 110°C and 120°C and any numerical value and numerical range within the range; an operating pressure of 0.01-0.05MPa, such as 0.01MPa, 0.02MPa, 0.06MPa, 0.08MPa, 0.11MPa, 0.12MPa, 0.13MPa, 0.16MPa, 0.17MPa, 0.18MPa, 0.19MPa, 0.20MPa, 0.21MPa, 0.22MPa, 0.23MPa, 0.24MPa, 0.26MPa, 0.27MPa, 0.28MPa, 0.29MPa, 0.30MPa, 0.31MPa, 0.32MPa, 0.33MPa, 0.34MPa, 0.36MPa, 0.37MPa, 0.38MPa, 0.39MPa, 0.40MPa, 0.41MPa, 0.42MPa, 0.43MPa .03MPa, 0.04MPa and 0.05MPa and any numerical value and numerical range within this range; preferably, the pretreatment also includes separating oil and gas from the gaseous material obtained by flash evaporation, extracting tar, and outputting light components as feed for its distillation device (i.e., the first distillation device 1); preferably, in step (1), the preheating is carried out in an evaporator buffer tank; the pretreatment also includes returning the gaseous material obtained by flash evaporation to the evaporator buffer tank for oil and gas separation, extracting tar from the bottom, and outputting light components as feed for its distillation device (i.e., the first distillation device 1) from the top, thereby further improving the subsequent distillation effect.

[0078] In one embodiment, step (1) further comprises condensing the removed light components, separating the obtained condensate into oil and water, and refluxing at least part of the oil phase separated from the oil and water back to the distillation device (i.e., the first distillation device 1), and / or at least part of it is extracted and used as a desorbent in step (7), thereby improving the product yield; preferably, the light components removed in step (1) are subjected to two-stage condensation, firstly, a primary condensation is performed to output a primary condensate and a primary non-condensable gas; then, the primary condensate is subjected to oil and water separation, the primary non-condensable gas is subjected to a secondary condensation, and a secondary condensate and a secondary non-condensable gas are output; The secondary condensate is then subjected to oil-water separation, and the secondary non-condensable gas is sent to a vacuum collector; the oil phase separated in the oil-water separation tank is at least partially refluxed to its distillation device (i.e., the first distillation device 1), and / or at least partially extracted and used as a desorbent in step (7), thereby further improving the product yield; preferably, the primary condensation uses circulating water as a cooling medium, and / or the secondary condensation uses chilled water as a cooling medium, and the temperature of the chilled water is -15 to -10°C, such as -15 to 10°C, -10°C, -5°C, 0°C, 5°C and 10°C and any value and numerical range within this range.

[0079] In order to improve the product yield, in one embodiment, step (2) further includes condensing the light components outputted therefrom, and at least partially refluxing and / or at least partially withdrawing the obtained condensate for use as feed for the adsorption device in step (3); preferably, the light components outputted from step (2) are subjected to two-stage condensation, firstly, a primary condensation is performed to output a primary condensate and a primary non-condensable gas; then the primary non-condensable gas is subjected to a secondary condensation to output a secondary condensate and a secondary non-condensable gas; then the secondary non-condensable gas is sent to a vacuum collector; then the primary condensate and / or the secondary condensate are at least partially refluxed and / or at least partially withdrawn and used as feed for the adsorption device (i.e., adsorption device 3) in step (3); preferably, the primary condensate and / or the secondary condensate are first sent to a dichlorobenzene reflux tank, and then at least partially refluxed to the distillation device (i.e., the second distillation device 2) of step (2) through a reflux pump and / or at least partially withdrawn and used as feed for the adsorption device (i.e., adsorption device 3) in step (3).

[0080] In one embodiment, step (7) further includes cooling the desorption liquid output from the adsorption device (i.e., the adsorption device 3); preferably, two-stage cooling is performed; preferably, the temperature is cooled to 60 to 90°C, such as 60°C, 70°C, 80°C and 90°C and any value and range of values ​​within the range.

[0081] In one embodiment, in step (2), the condensate obtained by condensing the light component is first sent to a cooling device for the desorption liquid as a cooling medium to heat exchange and cool the desorption liquid before being sent to the adsorption device (i.e., the adsorption device 3) to increase its own temperature, thereby improving energy utilization; preferably, the heated condensate is subjected to gas-liquid separation to separate the gas containing chlorobenzene and the liquid containing p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene, and then the separated liquid is heated and buffered in turn before being used as feed for the adsorption device (i.e., the adsorption device 3) in step (3); preferably, the gas-liquid separation conditions include: an operating temperature of 190 to 220°C, such as 190°C, 200°C, 210°C and 220°C and any value and range of values ​​within the range; an operating pressure of 0.1 to 0.5 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa and 0.5 MPa and any value and range of values ​​within the range.

[0082] In one embodiment, the raffinate output from step (3) is cooled before being sent to step (4) for distillation; preferably, two-stage cooling is performed; preferably, the temperature is cooled to 40-60°C, such as 40°C, 45°C, 50°C, 55°C and 60°C and any value and range of values ​​within the range.

[0083] In one embodiment, before the desorbent is introduced into the adsorption device (i.e., the adsorption device 3) in step (7), the temperature is first increased; preferably, the temperature is increased to 190-220° C., such as 190° C., 200° C., 210° C., and 220° C., and any value and range of values ​​within the range;

[0084] Preferably, before the desorbent is introduced into the adsorption device (i.e., the adsorption device 3) in step (7), it is first sent to the cooling device of the residual liquid to serve as a cooling medium to perform heat exchange and cooling of the residual liquid output from the adsorption device (i.e., the adsorption device 3), while the desorbent itself is heated up, thereby improving energy utilization and reducing external energy demand.

[0085] In one embodiment, the light component output from step (4) is first cooled and condensed before being used in step (7), and the obtained condensate is used as a desorbent in step (7); preferably, the temperature is cooled to 30-50°C, such as 30°C, 35°C, 40°C, 45°C and 50°C and any value and range of values ​​within the range.

[0086] In one embodiment, step (8) further comprises condensing the light components output from the distillation device (i.e., the seventh distillation device 7), at least partially refluxing and / or at least partially cooling the light components, and then using them as a desorbent in step (7); preferably, the light components output from step (8) are condensed, and the obtained condensate is at least partially refluxing and / or at least partially cooled, and then used as a desorbent in step (7); preferably, two-stage condensation is performed, firstly, a primary condensation is performed to output a primary condensate and a primary non-condensable gas; then, the primary non-condensable gas is subjected to a secondary condensation, and a secondary condensate and a secondary non-condensable gas are output; then, the secondary non-condensable gas is sent to a vacuum collector; then, the primary condensate and / or the secondary condensate are at least partially refluxing and / or at least partially cooled, and then used as a desorbent in step (7).

[0087] In one embodiment, step (9) further includes condensing the light components output from the distillation device (i.e., the eighth distillation device 8), and at least partially refluxing the obtained condensate and / or at least partially using it in step (10) as feed for its pre-crystallization device (i.e., the pre-crystallization device 9); preferably, two-stage condensation is performed, firstly, a primary condensation is performed to output a primary condensate and a primary non-condensable gas; then, the primary non-condensable gas is subjected to a secondary condensation to output a secondary condensate and a secondary non-condensable gas; then, the secondary non-condensable gas is sent to a vacuum collector; then, the primary condensate and / or the secondary condensate are at least partially refluxed and / or at least partially used in step (10) as feed for its pre-crystallization device (i.e., the pre-crystallization device 9).

[0088] In one embodiment, the pre-crystallization mother liquor obtained in step (10) is returned to the pre-crystallization device (i.e., the pre-crystallization device 9) for cyclic crystallization, thereby improving the crystallization rate; and / or

[0089] The primary crystallization mother liquor obtained in step (11) is returned to the pre-crystallization device (i.e., pre-crystallization device 9) in step (10) for cyclic crystallization, thereby improving the crystallization rate; and / or

[0090] The secondary crystallization mother liquor obtained in step (12) is returned to the primary crystallization device (i.e., primary crystallization device 10) of step (11) for cyclic crystallization, thereby improving the crystallization rate.

[0091] Those skilled in the art will appreciate that after the material comes out, it can be sent to a corresponding buffer tank, buffer tank or storage tank, storage tank for buffering before being sent to the next step or device. The three isomers separated can be sent to corresponding storage tanks respectively.

[0092] The present invention also provides a system for separating dichlorobenzene isomers in the above method, such as Figure 1 shown.

[0093] In one embodiment, Figure 1 As shown, the system includes a first distillation device 1, a second distillation device 2, an adsorption device 3, a fourth distillation device 4, a fifth distillation device 5, a sixth distillation device 6, a seventh distillation device 7, an eighth distillation device 8, a pre-crystallization device 9, a primary crystallization device 10, a secondary crystallization device 11 and a post-processing device connected by pipelines; wherein,

[0094] The first distillation device 1, the second distillation device 2, and the adsorption device 3 are connected in sequence; the first distillation device 1 is used to feed the pretreated dichlorobenzene isomers, and distill them, remove the light components containing chlorobenzene from the top of the tower, and output the heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the bottom of the tower; the second distillation device 2 is used to distill the heavy components from the first distillation device 1, remove the heavy components containing tar from the bottom of the tower, and output the light components containing p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the top of the tower; the adsorption device 3 is provided with an inlet, a residual liquid outlet and a desorption liquid outlet, which is used to feed the light components from the second distillation device 2 from its inlet during adsorption and adsorb and retain the p-dichlorobenzene therein, output the residual liquid containing o-dichlorobenzene and m-dichlorobenzene from the residual liquid outlet, and during desorption, a desorbent is introduced from the inlet to dissolve the adsorbed p-dichlorobenzene and then desorb it, and the desorption liquid is formed and output from the desorption liquid outlet;

[0095] The adsorption device 3, the fourth distillation device 4, the fifth distillation device 5 and the sixth distillation device 6 are connected in sequence, and the inlet of the fourth distillation device 4 is connected to the residual liquid outlet of the adsorption device 3; the fourth distillation device 4 is used to distill the residual liquid from the adsorption device 3, remove the light components containing chlorobenzene from the top of the tower, and output the heavy components containing o-dichlorobenzene and m-dichlorobenzene from the bottom of the tower; the fifth distillation device 5 is used to distill the heavy components from the fourth distillation device 4, separate m-dichlorobenzene from the top of the tower, and output the heavy components containing o-dichlorobenzene from the bottom of the tower; the sixth distillation device 6 is used to distill the heavy components from the fifth distillation device 5, remove the heavy components containing tar from the bottom of the tower, and output o-dichlorobenzene from the top of the tower;

[0096] The adsorption device 3, the seventh distillation device 7, the eighth distillation device 8, the pre-crystallization device 9, the primary crystallization device 10, the secondary crystallization device 11 and the post-treatment device are connected in sequence, and the inlet of the seventh distillation device 7 is connected to the desorption liquid outlet of the adsorption device 3; the seventh distillation device 7 is used to distill the desorption liquid from the adsorption device 3, remove the light components containing chlorobenzene from the top of the tower, and output the heavy components containing p-dichlorobenzene from the bottom of the tower; the eighth distillation device 8 is used to distill the heavy components from the seventh distillation device 7, remove the heavy components containing tar from the bottom of the tower, and output the light components enriched in p-dichlorobenzene from the top of the tower; the pre-crystallization device 9, the primary crystallization device 10, the secondary crystallization device 11 and the post-treatment device are connected in sequence, and the inlet of the seventh distillation device 7 is connected to the desorption liquid outlet of the adsorption device 3; the seventh distillation device 7 is used to distill the desorption liquid from the adsorption device 3, remove the light components containing chlorobenzene from the top of the tower, and output the heavy components enriched in p-dichlorobenzene from the bottom of the tower; The crystallization device 9 is used for pre-crystallizing the light components from the eighth distillation device 8, and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor; the primary crystallization device 10 is used for primary crystallization of the remelted melt of the crude p-dichlorobenzene crystals from the pre-crystallization device 9, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor; the secondary crystallization device 11 is used for secondary crystallization of the remelted liquid of the primary p-dichlorobenzene crystals from the primary crystallization device 10, and outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor; the post-treatment device is used for sequentially hot-melting, cooling and slicing the secondary p-dichlorobenzene crystals from the secondary crystallization device 11 to obtain p-dichlorobenzene.

[0097] In one embodiment, the system further comprises a pretreatment device, the outlet of which is connected to the inlet of the first distillation device 1, for feeding the first distillation device 1; the pretreatment device comprises an evaporator buffer tank and a flash evaporator which are sequentially connected and arranged, for sequentially preheating and flashing the dichlorobenzene isomer feed to obtain a gaseous material; preferably, the gaseous outlet of the flash evaporator is also connected to the gaseous inlet of the evaporator buffer tank, for returning the gaseous material obtained by flashing to the evaporator buffer tank for oil and gas separation, producing tar, and outputting a light component as the feed of the first distillation device 1.

[0098] In one embodiment, the system further includes a primary cooler, a secondary cooler, a dichlorobenzene low-level tank and a vacuum collector which are connected in sequence, wherein the inlet of the primary cooler is connected to the light component outlet of the second distillation device 2, and is used to condense the light component output by the second distillation device 2 once, and output a primary condensate and a primary non-condensable gas; the secondary cooler is used to condense the primary non-condensable gas output by the primary cooler for a secondary time, and output a secondary condensate and a secondary non-condensable gas; the inlet of the dichlorobenzene low-level tank is respectively connected to the primary condensate outlet of the primary cooler and the secondary condensate outlet of the secondary cooler, and is used to receive the primary condensate of the primary cooler and the secondary condensate of the secondary cooler to at least partially reflux and / or at least partially extract as feed for the adsorption device 3; the vacuum collector is connected to the secondary non-condensable gas outlet of the secondary cooler, and is used to capture the secondary non-condensable gas of the secondary cooler.

[0099] Those skilled in the art will appreciate that the system of the present invention also includes other equipment capable of carrying out the aforementioned method, as well as intermediate equipment, such as intermediate buffer tanks for various substances, lifting pumps for various materials, and the like.

[0100] The method of the present invention adopts the process of separating dichlorobenzene isomers by the aforementioned system as follows Figure 1 As shown:

[0101] (1) pre-treating the dichlorobenzene isomers and sending them to a first distillation unit 1 for distillation, removing light components including chlorobenzene from the top of the distillation unit, and outputting heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the bottom of the distillation unit;

[0102] (2) sending the heavy components obtained in step (1) to a second distillation unit 2 for distillation, removing the heavy components including tar from the bottom of the second distillation unit 2, and outputting the light components including p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the top of the second distillation unit 2;

[0103] (3) sending the light component obtained in step (2) to an adsorption device 3 to adsorb and retain the p-dichlorobenzene therein, and outputting a residual liquid containing o-dichlorobenzene and m-dichlorobenzene;

[0104] (4) sending the raffinate obtained in step (3) to a fourth distillation unit 4 for distillation, removing light components including chlorobenzene from the top of the distillation unit, and outputting heavy components including o-dichlorobenzene and m-dichlorobenzene from the bottom of the distillation unit;

[0105] (5) sending the heavy component obtained in step (3) to a fifth distillation unit 5 for distillation, separating meta-dichlorobenzene from the top of the distillation unit, and outputting a heavy component containing ortho-dichlorobenzene from the bottom of the distillation unit;

[0106] (6) sending the heavy components obtained in step (5) to a sixth distillation unit 6 for distillation, removing the heavy components including tar from the bottom of the distillation unit, and outputting o-dichlorobenzene from the top of the distillation unit;

[0107] (7) introducing the desorbent into the adsorption device 3 in step (3) to dissolve and then desorb the adsorbed p-dichlorobenzene to form a desorbed liquid for output;

[0108] (8) sending the desorbed liquid obtained in step (7) to a seventh distillation unit 7 for distillation, removing light components including chlorobenzene from the top of the distillation unit, and outputting heavy components including p-dichlorobenzene from the bottom of the distillation unit;

[0109] (9) sending the heavy components obtained in step (8) to an eighth distillation unit 8 for distillation, removing the heavy components including tar from the bottom of the distillation unit 8, and outputting the light components enriched in p-dichlorobenzene from the top of the distillation unit 8;

[0110] (10) sending the light component obtained in step (9) to a pre-crystallization device 9 for pre-crystallization, and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor;

[0111] (11) heating and remelting the crude p-dichlorobenzene crystals obtained in step (10) in stages, remelting at 10-40° C. to obtain a primary melt and returning it to the adsorption device 3 in step (3), remelting at 50-70° C. to obtain a secondary melt and sending it to the primary crystallization device 10 for primary crystallization, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor;

[0112] (12) remelting the primary p-dichlorobenzene crystals obtained in step (11) and sending them to a secondary crystallization device 11 for secondary crystallization, and outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor;

[0113] (13) The secondary p-dichlorobenzene crystals obtained in step (12) are sequentially subjected to heat melting, cooling and slicing to obtain p-dichlorobenzene.

[0114] Those skilled in the art understand that, in the present invention, the distillation device is a distillation device commonly used in the art, such as a distillation tower; the adsorption device is an adsorption device commonly used in the art, such as an adsorption tower; the crystallization device is a crystallization device commonly used in the art, such as a crystallizer.

[0115] The present invention is further described below by means of specific examples.

[0116] Example 1 (S1)

[0117] For dichlorobenzene isomer 1, the method of the present invention is used as follows Figure 1 The process shown is for separating dichlorobenzene isomers, wherein dichlorobenzene isomer 1 comprises 7wt% of chlorobenzene, 2wt% of tar, 30wt% of p-dichlorobenzene, 15wt% of o-dichlorobenzene, 44wt% of m-dichlorobenzene, and 2wt% of water;

[0118] The specific steps include:

[0119] (1) preheating and flashing the dichlorobenzene isomer 1 in sequence, and then sending the gaseous material obtained by flashing to a first distillation device 1 for distillation, removing light components including chlorobenzene from the top of the distillation device, and outputting heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the bottom of the distillation device;

[0120] (2) sending the heavy components obtained in step (1) to a second distillation unit 2 for distillation, removing the heavy components including tar from the bottom of the second distillation unit 2, and outputting the light components including p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene from the top of the second distillation unit 2;

[0121] (3) sending the light component obtained in step (2) to an adsorption device 3 to adsorb and retain the p-dichlorobenzene therein, and outputting a residual liquid containing o-dichlorobenzene and m-dichlorobenzene;

[0122] (4) sending the raffinate obtained in step (3) to a fourth distillation unit 4 for distillation, removing light components including chlorobenzene from the top of the distillation unit, and outputting heavy components including o-dichlorobenzene and m-dichlorobenzene from the bottom of the distillation unit;

[0123] (5) sending the heavy component obtained in step (4) to a fifth distillation unit 5 for distillation, separating meta-dichlorobenzene from the top of the distillation unit, and outputting a heavy component containing ortho-dichlorobenzene from the bottom of the distillation unit;

[0124] (6) sending the heavy components obtained in step (5) to an o-dichlorobenzene distillation tower 6 for distillation, removing the heavy components including tar from the bottom of the tower, and outputting o-dichlorobenzene from the top of the tower;

[0125] (7) introducing the desorbent into the adsorption device 3 in step (3) to dissolve and then desorb the adsorbed p-dichlorobenzene to form a desorbed liquid for output;

[0126] (8) sending the desorbed liquid obtained in step (7) to a seventh distillation unit 7 for distillation, removing light components including chlorobenzene from the top of the distillation unit, and outputting heavy components including p-dichlorobenzene from the bottom of the distillation unit;

[0127] (9) sending the heavy components obtained in step (8) to an eighth distillation unit 8 for distillation, removing the heavy components including tar from the bottom of the distillation unit 8, and outputting the light components enriched in p-dichlorobenzene from the top of the distillation unit 8;

[0128] (10) sending the light component obtained in step (9) to a pre-crystallization device 9 for pre-crystallization, and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor;

[0129] (11) heating and remelting the crude p-dichlorobenzene crystals obtained in step (10) in stages, remelting at 10-40° C. to obtain a primary melt and returning it to the adsorption device 3 in step (3), remelting at 50-70° C. to obtain a secondary melt and sending it to the primary crystallization device 10 for primary crystallization, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor;

[0130] (12) remelting the primary p-dichlorobenzene crystals obtained in step (11) and sending them to a secondary crystallization device 11 for secondary crystallization, and outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor;

[0131] (13) melting, cooling and slicing the secondary p-dichlorobenzene crystals obtained in step (12) in sequence to obtain p-dichlorobenzene; wherein:

[0132] In step (1), preheating to 100°C; flash evaporation uses 0.6MPa steam; flash evaporation conditions include: operating temperature of 100°C and operating pressure of 0.03MPa; distillation operating conditions include: operating temperature of 110°C and operating pressure of -0.09MPa;

[0133] In step (2), the operating conditions of the distillation include: an operating temperature of 140° C. and an operating pressure of −0.09 MPa;

[0134] In step (3), the adsorption operating conditions of the adsorption device 3 include: the adsorption temperature is 200° C., the adsorption pressure is 0.2 MPa, the adsorption column is a jacketed packing column, there are 5 adsorption columns, and they are arranged in parallel;

[0135] In step (4), the operating conditions of the distillation include: an operating temperature of 105° C. and an operating pressure of −0.09 MPa;

[0136] In step (5), the operating conditions of the distillation include: an operating temperature of 115° C. and an operating pressure of −0.09 MPa;

[0137] In step (6), the operating conditions of the distillation include: an operating temperature of 140° C. and an operating pressure of −0.09 MPa;

[0138] In step (7), the desorption operating conditions of the adsorption device 3 include: a desorption temperature of 200° C. and a desorption pressure of 0.2 MPa;

[0139] In step (8), the operating conditions of the distillation include: an operating temperature of 110° C. and an operating pressure of −0.09 MPa;

[0140] In step (9), the operating conditions of the distillation include: an operating temperature of 140° C. and an operating pressure of −0.09 MPa;

[0141] In step (10), the operating conditions of the pre-crystallization device 9 include: an operating temperature of -10 / 70°C (meaning crystallization at -10°C and heating and melting at 70°C for removal), and an operating pressure of 0.4 MPa;

[0142] In step (11), the operating conditions of the primary crystallization device 10 include: an operating temperature of 10 / 70°C (meaning crystallization at 10°C and heating and melting at 70°C for removal), and an operating pressure of 0.4 MPa;

[0143] In step (12), the operating conditions of the secondary crystallization device 11 include: an operating temperature of 10 / 70°C (meaning crystallization at 10°C and heating and melting at 70°C for removal), and an operating pressure of 0.4 MPa.

[0144] Embodiment 2 (S2)

[0145] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0146] In step (1), preheating to 90°C; flash evaporation using 0.6MPa steam; flash evaporation conditions include: operating temperature of 90°C, operating pressure of 0.05MPa; distillation operating conditions include: operating temperature of 100°C, operating pressure of -0.095MPa;

[0147] In step (2), the operating conditions of the distillation include: an operating temperature of 130° C. and an operating pressure of −0.095 MPa;

[0148] In step (3), the adsorption operating conditions of the adsorption device 3 include: the adsorption temperature is 190° C., the adsorption pressure is 0.3 MPa, the adsorption column is a jacketed packing column, there are 5 adsorption columns, and they are arranged in parallel;

[0149] In step (4), the operating conditions of the distillation include: an operating temperature of 95° C. and an operating pressure of −0.095 MPa;

[0150] In step (5), the operating conditions of the distillation include: an operating temperature of 105° C. and an operating pressure of −0.095 MPa;

[0151] In step (6), the operating conditions of the distillation include: an operating temperature of 130° C. and an operating pressure of −0.095 MPa;

[0152] In step (7), the desorption operating conditions of the adsorption device 3 include: a desorption temperature of 190° C. and a desorption pressure of 0.3 MPa;

[0153] In step (8), the operating conditions of the distillation include: an operating temperature of 100° C. and an operating pressure of −0.095 MPa;

[0154] In step (9), the operating conditions of the distillation include: an operating temperature of 130° C. and an operating pressure of −0.095 MPa;

[0155] In step (10), the operating conditions of the pre-crystallization device 9 include: an operating temperature of -5 / 75°C and an operating pressure of 0.4 MPa;

[0156] In step (11), the operating conditions of the primary crystallization device 10 include: an operating temperature of 15 / 75° C. and an operating pressure of 0.4 MPa;

[0157] In step (12), the operating conditions of the secondary crystallization device 11 include: an operating temperature of 15 / 75° C. and an operating pressure of 0.4 MPa.

[0158] Embodiment 3 (S3)

[0159] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0160] In step (1), preheating to 110°C; flash evaporation using 0.6MPa steam; flash evaporation conditions include: operating temperature of 110°C, operating pressure of 0.01MPa; distillation operating conditions include: operating temperature of 120°C, operating pressure of -0.085MPa;

[0161] In step (2), the operating conditions of the distillation include: an operating temperature of 150° C. and an operating pressure of −0.085 MPa;

[0162] In step (3), the adsorption operating conditions of the adsorption device 3 include: the adsorption temperature is 220° C., the adsorption pressure is 0.2 MPa, the adsorption column is a jacketed packing column, there are 5 adsorption columns, and they are arranged in parallel;

[0163] In step (4), the operating conditions of the distillation include: an operating temperature of 115° C. and an operating pressure of −0.085 MPa;

[0164] In step (5), the operating conditions of the distillation include: an operating temperature of 125° C. and an operating pressure of −0.085 MPa;

[0165] In step (6), the operating conditions of the distillation include: an operating temperature of 150° C. and an operating pressure of −0.085 MPa;

[0166] In step (7), the desorption operating conditions of the adsorption device 3 include: a desorption temperature of 220° C. and a desorption pressure of 0.2 MPa;

[0167] In step (8), the operating conditions of the distillation include: an operating temperature of 120° C. and an operating pressure of −0.085 MPa;

[0168] In step (9), the operating conditions of the distillation include: an operating temperature of 150° C. and an operating pressure of −0.085 MPa;

[0169] In step (10), the operating conditions of the pre-crystallization device 9 include: an operating temperature of -5 / 85°C and an operating pressure of 0.3 MPa;

[0170] In step (11), the operating conditions of the primary crystallization device 10 include: an operating temperature of 15 / 85° C. and an operating pressure of 0.3 MPa;

[0171] In step (12), the operating conditions of the secondary crystallization device 11 include: an operating temperature of 15 / 85° C. and an operating pressure of 0.3 MPa.

[0172] Embodiment 4 (S4)

[0173] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0174] In step (1), the light component is also sent to its primary cooler for primary condensation using circulating water, and a primary condensate and a primary non-condensable gas are output; then the primary condensate is sent to the oil-water separation tank for oil-water separation, and the primary non-condensable gas is sent to the secondary cooler for secondary condensation using 5°C chilled water, and a secondary condensate and a secondary non-condensable gas are output; then the secondary condensate is sent to the oil-water separation tank for oil-water separation, and the secondary non-condensable gas is sent to the vacuum collector; the oil phase separated in the oil-water separation tank is partially refluxed to the first distillation device 1, and part is extracted and used as a desorbent in step (7).

[0175] Embodiment 5 (S5)

[0176] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0177] In step (2), the light components output from the second distillation device 2 are sent to its primary cooler for primary condensation using circulating water, and primary condensate and primary non-condensable gas are output; the primary non-condensable gas is then sent to its secondary cooler for secondary condensation using circulating water, and secondary condensate and secondary non-condensable gas are output; the secondary non-condensable gas is then sent to a vacuum collector; and part of the primary condensate and / or secondary condensate is then refluxed, and part of it is extracted and used as feed for the adsorption device 3 in step (3).

[0178] Embodiment 6 (S6)

[0179] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0180] The light components removed in step (1) are used as a desorbent in step (7).

[0181] Embodiment 7 (S7)

[0182] Dichlorobenzene isomer 1 was separated according to the method of Example 1; compared with Example 1, it has the following differences:

[0183] The light components removed in step (1), step (4) and step (8) are all used as desorbents in step (7).

[0184] Comparative Example 1 (D1)

[0185] The dichlorobenzene isomer 1 was separated by a conventional method, specifically as follows: p-dichlorobenzene was separated from the dichlorobenzene isomer mixture by crystallization (the crystallization operating temperature was -10 / 70°C and the operating pressure was 0.4 MPa), the crystallization mother liquor was distilled (the distillation operating temperature was 115°C and the operating pressure was -0.09 MPa) to obtain a heavy component as an o-dichlorobenzene product, the distillate was recrystallized (the recrystallization operating temperature was 10 / 70°C and the operating pressure was 0.4 MPa) to precipitate p-dichlorobenzene and obtain a mother liquor enriched in m-dichlorobenzene, and the m-dichlorobenzene-enriched mother liquor was distilled (the distillation operating temperature was 115°C and the operating pressure was -0.09 MPa) to obtain a distillate as an m-dichlorobenzene product.

[0186] result

[0187] The meta-dichlorobenzene obtained at the top of the fifth distillation unit 5 in Example 1-7 (S1-7), the ortho-dichlorobenzene obtained at the top of the sixth distillation unit 6, and the para-dichlorobenzene obtained in step (13) (i.e., the three products obtained) were sampled and analyzed respectively to obtain their purity data. The results are shown in Table 2.

[0188] The m-dichlorobenzene, o-dichlorobenzene and p-dichlorobenzene (i.e. the three products obtained) obtained in Comparative Example 1 (D1) were sampled and analyzed respectively to obtain their purity data. The results are shown in Table 3

[0189] Table 2 Purity of the three products obtained in Example 1-7 (S1-7)

[0190]

[0191]

[0192] Table 3 Purity of the three products obtained in Comparative Example 1 (D1)

[0193] project D1 The obtained m-dichlorobenzene Purity (wt%) 91 The obtained o-dichlorobenzene Purity (wt%) 93 The obtained p-dichlorobenzene Purity (wt%) 93

[0194] According to Table 2 and Table 3, compared with the traditional method, the method of the present invention has a good separation effect on dichlorobenzene isomers, and the purity of the separated meta-dichlorobenzene, ortho-dichlorobenzene and para-dichlorobenzene is high.

Claims

1. A method for separating dichlorobenzene isomers, characterized in that: The dichlorobenzene isomers include at least chlorobenzene, tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene; The method comprises the following steps: (1) pre-treating the dichlorobenzene isomers and then performing distillation to remove light components, thereby removing light components including chlorobenzene, and outputting heavy components including tar, p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene; (2) subjecting the heavy components obtained in step (1) to distillation to remove the heavy components including tar, and outputting the light components including p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene; (3) sending the light component obtained in step (2) to an adsorption device to adsorb and retain the p-dichlorobenzene therein, and outputting a raffinate containing o-dichlorobenzene and m-dichlorobenzene; (4) distilling the raffinate obtained in step (3) to remove light components, remove light components including chlorobenzene, and output heavy components including o-dichlorobenzene and m-dichlorobenzene; (5) distilling the heavy component obtained in step (3) to separate meta-dichlorobenzene, and outputting the heavy component containing ortho-dichlorobenzene; (6) distilling the heavy components obtained in step (5) to remove the heavy components including tar and output o-dichlorobenzene; (7) introducing the desorbent into the adsorption device in step (3) to dissolve and then desorb the adsorbed p-dichlorobenzene to form a desorbed liquid for output; (8) distilling the desorbed liquid obtained in step (7) to remove light components, remove light components including chlorobenzene, and output heavy components including p-dichlorobenzene; (9) subjecting the heavy components obtained in step (8) to distillation to remove the heavy components including tar, and outputting the light components enriched in p-dichlorobenzene; (10) pre-crystallizing the light component obtained in step (9), and outputting crude p-dichlorobenzene crystals and pre-crystallization mother liquor; (11) heating and remelting the crude p-dichlorobenzene crystals obtained in step (10) in stages, obtaining a primary melt at 10-40° C. and returning the primary melt to the adsorption device in step (3), obtaining a secondary melt at 50-70° C. and performing primary crystallization, and outputting primary p-dichlorobenzene crystals and primary crystallization mother liquor; (12) remelting the primary p-dichlorobenzene crystals obtained in step (11) and performing secondary crystallization, outputting secondary p-dichlorobenzene crystals and secondary crystallization mother liquor; (13) The secondary p-dichlorobenzene crystals obtained in step (12) are sequentially subjected to heat melting, cooling and slicing to obtain p-dichlorobenzene.

2. The method according to claim 1, characterized in that In step (1), the pretreatment includes preheating and flashing the dichlorobenzene isomers in sequence to obtain a gaseous material for use as a feed for its distillation device; preferably, the pretreatment also includes oil and gas separation of the gaseous material obtained by flashing, extracting tar and outputting light components as feed for its distillation device; preferably, in step (1), the preheating is carried out in an evaporator buffer tank; the pretreatment also includes returning the gaseous material obtained by flashing to the evaporator buffer tank for oil and gas separation, extracting tar from the bottom, and outputting light components as feed for its distillation device from the top.

3. The method according to claim 1 or 2, characterized in that: Step (2) also includes condensing the light components output from the distillation device, and at least partially refluxing and / or at least partially recovering the obtained condensate for use as feed for the adsorption device in step (3).

4. The method according to claim 3, characterized in that Step (7) further includes cooling the desorption liquid output from the adsorption device; Preferably, the condensate obtained in step (2) is first used as a cooling medium to heat and cool the desorbed liquid before being sent to the adsorption device, and the condensate itself is heated. Preferably, the heated condensate is subjected to gas-liquid separation to separate the gas containing chlorobenzene and the liquid containing p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene. The separated liquid is then heated and buffered in sequence before being used as feed for the adsorption device in step (3).

5. The method according to any one of claims 1 to 4, characterized in that In step (7), the desorbent is chlorobenzene; preferably, the method further comprises using the light components removed in any one or more of steps (1), (4) and (8) as a desorbent in step (7).

6. The method according to any one of claims 1 to 5, characterized in that In step (3), the raffinate outputted from the adsorption device is cooled before being distilled in step (4); Preferably, in step (7), the temperature is first increased before the desorbent is introduced into the adsorption device; Preferably, before the desorbent is introduced into the adsorption device in step (7), it is first used as a cooling medium to cool the residual liquid output from the adsorption device, while the desorbent itself is heated.

7. The method according to any one of claims 1 to 6, characterized in that The light component output from step (4) is first cooled and condensed before being used in step (7), and the obtained condensate is used as a desorbent in step (7); and / or After the light components output from step (8) are condensed, the resulting condensate is at least partially refluxed and / or at least partially cooled and then used as a desorbent in step (7).

8. The method according to any one of claims 1 to 7, characterized in that Step (9) also includes condensing the light components output from the rectification device, and at least partially refluxing the obtained condensate and / or at least partially using it as feed for the pre-crystallization device in step (10).

9. The method according to any one of claims 1 to 8, characterized in that The pre-crystallization mother liquor obtained in step (10) is returned to the pre-crystallization device for cyclic crystallization; and / or The mother liquor of the primary crystallization obtained in step (11) is returned to the pre-crystallization device for cyclic crystallization; and / or The secondary crystallization mother liquor obtained in step (12) is returned to the primary crystallization device for cyclic crystallization.

10. A system for separating dichlorobenzene isomers in the method according to any one of claims 1 to 9.

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