Negative-pressure low-temperature catalysis method and device for rectifying still liquid in trichloroethylene production

Abstract

The invention provides a negative-pressure low-temperature catalysis method and device for rectifying still liquid in trichloroethylene production, and belongs to the field of trichloroethylene production. The negative-pressure low-temperature catalysis method for the rectifying still liquid in trichloroethylene production comprises the following steps: feeding, negative pressure pumping of a system, continuous vaporization of materials, continuous contact reaction and material condensation. According to the negative-pressure low-temperature catalysis method and device for the rectifying still liquid in trichloroethylene production, the reaction process can be effectively simplified, the controllability can be improved, the reaction energy consumption can be reduced, the combined conversion treatment of 1, 1, 2, 3, 4-pentachloro-1, 3-butadiene and perchloro-1, 3-butadiene in the rectifying still liquid can be effectively realized, and the production cost can be reduced. And effective treatment and recycling of the rectifying still liquid in trichloroethylene production are realized.

Description

Technical Field

[0001] The invention relates to the field of trichloroethylene production, in particular to a negative pressure low temperature catalytic method and device for rectifying kettle liquid in trichloroethylene production. Background Art

[0002] 1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene are by-products in the production of trichloroethylene. In the prior art, there is no joint treatment technology that can effectively reuse all by-products (1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene) in the production of trichloroethylene. In actual production, they are usually treated as distillation hazardous waste by qualified units, or incinerated, which not only wastes a lot of production raw materials and production energy consumption, but also produces a lot of toxic wastes during the incineration process, which is not environmentally friendly.

[0003] At present, the only method disclosed in the prior art is to prepare hexachloroethane by liquid phase reaction of perchloro-1,3-butadiene and chlorine in the presence of a catalyst. However, this method is an intermittent reaction, and the catalyst needs to be added again before each reaction. At the same time, the reaction liquid after the reaction by this method needs to be filtered, washed with water, washed with alkali, dried, sublimated and other treatment steps to finally obtain the hexachloroethane product. Its treatment process is complicated, the controllability is poor, the equipment investment and the floor space are large, and it cannot meet the requirements of large-scale production.

[0004] Furthermore, the prior art also discloses a method for treating high-boiling substances in trichloroethylene production, in which the high-boiling substances are vaporized, condensed with tetrachloroethane, and then reacted with liquid chlorine; and in the process of reacting with liquid chlorine, it is necessary to adjust the feed rate of liquid chlorine in real time according to the temperature change in the reactor, and control the reaction pressure to not exceed the threshold value throughout the process. Although this method can treat 1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene in high-boiling substances to a certain extent, it requires a high temperature of more than 240°C to continuously vaporize the high-boiling substances during its vaporization process; and after condensation and liquefaction, it is necessary to react with liquid chlorine under the conditions of reaction temperature exceeding 220°C and reaction pressure exceeding 400KPa. The method of continuous vaporization followed by condensation wastes a lot of production energy consumption; and in the subsequent reaction with chlorine, a high-temperature and high-pressure reaction environment is required, the production process is complicated, difficult to control, and the reaction economy is poor. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a negative pressure low-temperature catalytic method and device for distillation kettle liquid in trichloroethylene production, which can effectively simplify the reaction process, improve controllability, reduce reaction energy consumption, effectively realize the combined conversion treatment of 1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene in the distillation kettle liquid, and realize the effective treatment and recycling of the distillation kettle liquid in trichloroethylene production.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production, comprising the following steps: adding material, pumping negative pressure from the system, continuous vaporization of the material, continuous contact reaction, and condensation of the material; The method of adding materials is as follows: tetrachloroethane and distillation kettle liquid are added into the distillation kettle at the same time; and the liquid levels of tetrachloroethane and distillation kettle liquid in the distillation kettle are controlled to 75-80%; The distillation kettle liquid includes: tetrachloroethane, pentachloroethane, pentachlorobutadiene, hexachlorobutadiene, and hexachloroethane; The method of pumping negative pressure in the system is to maintain the internal pressure of each pressure vessel used in the negative pressure low temperature catalytic method within the range of -85KPa to -95KPa; The method for continuously vaporizing the material is to control the temperature of the distillation kettle to rise under negative pressure conditions, and continuously vaporize the material in the distillation kettle to obtain a vaporized mixture; The method of continuous contact reaction is to simultaneously introduce the vaporized mixture and chlorine into a catalytic reactor filled with a modified catalyst, control the temperature in the catalytic reactor to 80-100° C., and continuously carry out the contact reaction to obtain a contact reactant; The preparation method of the modified catalyst comprises the following steps: pretreatment, composite treatment; The pretreatment method comprises adding activated carbon to an aqueous solution containing hydrochloric acid and ethanol, heating and stirring the solution, washing the solution with water, and drying the solution to obtain pretreated activated carbon. The composite treatment method is to add the pretreated activated carbon into an aqueous solution containing ferric chloride, cupric chloride and nickel chloride, heat and stir the mixture, and then calcine the mixture under nitrogen protection to obtain a modified catalyst. The contact reactants are condensed to obtain a condensate whose main components are tetrachloroethane, pentachloroethane and hexachloroethane.

[0007] Furthermore, the step of adding materials also includes: preheating; The preheating method is to load the modified activated carbon into a catalytic reactor, then replace it with nitrogen, heat it to 90-100° C., and complete the preheating after heat preservation.

[0008] Preferably, in the added material, the weight ratio of tetrachloroethane to distillation kettle liquid is 2-3:1.

[0009] Preferably, during the continuous vaporization of the material, the heating rate of the distillation kettle is 30-35°C / h; The temperature of the still is raised to 110-130°C and the top temperature is 100-120°C.

[0010] Preferably, during the continuous vaporization of the material, tetrachloroethane and distillation kettle liquid are continuously added to the still at a weight ratio of 2-3:1 to maintain the liquid level in the still at 75-80%.

[0011] Preferably, in the continuous contact reaction, the volume flow ratio of chlorine gas to the vaporized mixture entering the catalytic reactor is 1:2-3.5; Preferably, during the material condensation, the condensate temperature is controlled at 60-80°C.

[0012] Preferably, in the pretreatment, the particle size of the activated carbon is 3-5 mm; In the aqueous solution containing hydrochloric acid and ethanol, the mass percentage of hydrochloric acid is 8-10%, and the mass percentage of ethanol is 30-35%; The weight ratio of the activated carbon to the aqueous solution containing hydrochloric acid and ethanol is 1:3-5.

[0013] Preferably, in the composite treatment, the aqueous solution containing ferric chloride, cupric chloride and nickel chloride has a ferric chloride content of 10-15wt%, a cupric chloride content of 3-5wt% and a nickel chloride content of 1-3wt%; The weight ratio of the pretreated activated carbon to the aqueous solution containing ferric chloride, cupric chloride and nickel chloride is 1:3-5.

[0014] A negative pressure low temperature catalytic device for rectifying still liquid in trichloroethylene production for realizing the above method, comprising: a still, a catalytic reactor, and a condenser; The first feed port and the second feed port of the distillation kettle are respectively connected to the tetrachloroethane feed pipe and the distillation kettle liquid feed pipe, so that the tetrachloroethane and the distillation kettle liquid are continuously fed into the distillation kettle; The upper air inlet of the distillation kettle is connected to a nitrogen gas source pipeline; The top gas outlet of the distillation kettle is connected to the first gas inlet pipeline at the top of the catalytic reactor, so that the vaporized compounds in the distillation kettle are continuously fed into the catalytic reactor; The second gas inlet at the top of the catalytic reactor is connected to a chlorine gas source pipeline so that chlorine gas is continuously fed into the catalytic reactor; The bottom discharge port of the catalytic reactor is connected to the top feed port pipeline of the condenser so as to continuously introduce the contact reactants into the condenser for material condensation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The negative pressure low temperature catalytic method and device for rectifying kettle liquid in trichloroethylene production of the present invention change the traditional liquid-liquid contact reaction mode and adopt a gas phase contact reaction mode, wherein the rectifying kettle liquid is negatively pressure vaporized and then reacted with chlorine in a catalytic reactor filled with a catalyst in a gas phase; at the same time, in combination with a modified catalyst prepared by pretreatment and composite treatment, it is possible to effectively realize long-term continuous reaction on an industrial scale without frequent replacement of the catalyst; at the same time, the negative pressure reaction mode is adopted, while avoiding affecting the normal reaction, effectively reducing the boiling point of the material and reducing the amount of heat medium (such as hot water) and coolant (such as cooling water); various technical means cooperate with each other and work synergistically, which can effectively simplify the treatment reaction process of the rectifying kettle liquid in trichloroethylene production, improve controllability, reduce treatment energy consumption, effectively realize the combined conversion treatment of 1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene in the rectifying kettle liquid, and realize the effective treatment and recycling of the rectifying kettle liquid in trichloroethylene production.

[0016] (2) The negative pressure low temperature catalytic method and device for the distillation kettle liquid in the production of trichloroethylene of the present invention change the traditional liquid-liquid contact reaction mode and adopt a gas phase contact reaction mode to make the vaporized mixture of tetrachloroethane and distillation kettle liquid contact and react with chlorine gas; compared with the traditional liquid-liquid contact reaction mode (in the liquid chlorine treatment process, -35°C frozen brine must be used for condensation), it further reduces production energy consumption, simplifies the process flow, reduces the requirements for related devices and ancillary pipelines, and effectively reduces production investment.

[0017] (3) According to the negative pressure low temperature catalytic method and device for treating the distillation kettle liquid in the production of trichloroethylene, after treating the distillation kettle liquid in the production of trichloroethylene, analysis of the reaction liquid (i.e., condensate) shows that pentachlorobutadiene and hexachlorobutadiene in the original distillation kettle liquid can be effectively converted into pentachloroethane and hexachloroethane, with a pentachlorobutadiene conversion rate of 92.8% and a hexachlorobutadiene conversion rate of 91.3%; the condensate obtained by the treatment can be subsequently reused as a raw material for cracking and producing trichloroethylene and tetrachloroethylene, thereby effectively realizing the recycling of the distillation kettle liquid in the production of trichloroethylene.

[0018] (4) The negative pressure low temperature catalytic method and device for treating distillation kettle liquid in trichloroethylene production of the present invention can achieve an effective service life of the modified catalyst of up to 1.5 years under the condition of continuously treating 3,000 tons of distillation kettle liquid per year. The modified catalyst in the catalytic reactor does not need to be replaced within 1.5 years of continuous operation of the device, which effectively reduces the difficulty of equipment maintenance and improves the treatment efficiency of distillation kettle liquid in trichloroethylene production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a schematic diagram of a treatment device for distillation kettle liquid in trichloroethylene production in Example 1; In the figure, 1-tetrachloroethane tank; 2-distillation kettle liquid tank; 3-tetrachloroethane feeding pump; 4-distillation kettle liquid feeding pump; 5-vacuum pump; 6-distillation kettle; 7-catalytic reactor; 8-condenser; 9-crude product tank; 10-crude product pump; 11-hot water tank; 12-hot water pump. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0021] Example 1 This embodiment provides a method and device for treating distillation kettle liquid in trichloroethylene production. The components and weight percentages of the trichloroethylene distillation kettle liquid used in this embodiment are: 25% tetrachloroethane, 7% pentachloroethane, 29% pentachlorobutadiene, 31% hexachlorobutadiene, 7% hexachloroethane, and 1% others. The tetrachloroethane feed liquid contains 97.5% tetrachloroethane, 1% pentachloroethane, 1% hexachloroethane, and 0.5% others.

[0022] The method for treating the rectification kettle liquid in the production of trichloroethylene comprises the following specific steps: 1. Preheating The inner diameter of the tube bundle is 50mm and the heat exchange area is 80m 2 The tubes of the tube-in-tube reactor (i.e., catalytic reactor 7) are filled with activated carbon modified catalyst (filling volume 1.2m 3 ); After the modified catalyst is loaded, a layer of activated carbon with a thickness of 10 cm is laid on the upper part of the catalytic reactor 7, and the nitrogen valve of the distillation kettle 6 is opened to replace the system with nitrogen until the volume percentage of oxygen in the system is less than 2%; then the hot water pump 12 of the catalytic reactor 7 is turned on, and the catalytic reactor 7 is heated at a rate of 20°C / h until the internal temperature of the catalytic reactor 7 reaches 90°C, and the temperature is kept for 5 hours, and then the nitrogen valve is closed to complete the preheating treatment.

[0023] Wherein, the preparation method of the modified catalyst is: 1) Preprocessing Activated carbon with an average particle size of 3 mm was added to an aqueous solution of 10% by mass of hydrochloric acid and 30% by mass of ethanol, and the temperature was raised to 40°C with stirring. The mixture was kept warm and stirred for 8 hours. The solid was filtered and washed with clean water to a pH of 6.5, and dried to obtain pretreated activated carbon.

[0024] Wherein, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:3.

[0025] 2) Composite treatment The pretreated activated carbon was immersed in an aqueous solution of 15% by mass ferric chloride, 5% by mass cupric chloride and 3% by mass nickel chloride, heated to 45°C with stirring, kept stirring for 4 hours, and then filtered to obtain a solid; the solid was then calcined at 210°C for 8 hours under a nitrogen protection environment to obtain a modified catalyst.

[0026] Among them, the weight ratio of activated carbon to aqueous solution of ferric chloride, cupric chloride and nickel chloride is 1:3.

[0027] 2. Adding materials Turn on the tetrachloroethane feed pump 3 and the distillation kettle liquid feed pump 4, and add the tetrachloroethane in the tetrachloroethane tank 1 and the distillation kettle liquid in the distillation kettle liquid tank 2 to the distillation kettle 6 (kettle volume is 20m 3 ) and control the liquid level of tetrachloroethane and distillation kettle liquid in the distillation kettle 6 to 75%.

[0028] The weight ratio of tetrachloroethane to distillation kettle liquid is 2:1.

[0029] 3. System negative pressure extraction Turn on the vacuum pump 5 to draw negative pressure to the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6 in the device system, and continue to maintain the negative pressure in the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6; specifically, keep the pressure before the vacuum pump 5 at -95KPa, the upper pressure of the crude product tank 9 at -94KPa, the upper pressure of the condenser 8 at -93KPa, the upper pressure of the catalytic reactor 7 at -90KPa, and the upper pressure of the distillation kettle 6 at -87KPa.

[0030] 4. Continuous vaporization of materials Slowly open the steam regulating valve of the still 6, heat the material in the still 6 at a heating rate of 30°C / h, heat the still 6 to a temperature of 120°C and a top temperature of 115°C, and continuously vaporize the material in the still 6 to obtain a vaporized mixture; and by adjusting the opening of the upper regulating valve of the still 6, control the volume flow rate of the vaporized mixture continuously introduced into the catalytic reactor 7 to be 30Nm 3 / h.

[0031] At the same time, during the material vaporization process, tetrachloroethane and distillation kettle liquid are continuously added into the still 6 at a weight ratio of 2:1, and the liquid level in the still 6 is maintained at 75%.

[0032] In order to maintain the continuous and stable operation of the distillation still liquid treatment in the production of trichloroethylene, the non-volatile matter at the bottom of the still 6 is discharged after the material is vaporized continuously for 6 months.

[0033] 5. Continuous contact reaction While the vaporized mixture is introduced into the catalytic reactor 7, the chlorine regulating valve on the upper part of the catalytic reactor 7 is opened to control the volume flow rate of chlorine gas continuously introduced into the catalytic reactor 7 to be 13.5 Nm 3 / h; and hot water is used to control the temperature in the catalytic reactor 7 to 80°C; the vaporized compound and chlorine gas are continuously contacted and reacted in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reactant, which is continuously introduced into the condenser 8.

[0034] The volume flow ratio of chlorine gas to vaporized mixture entering the catalytic reactor 7 is 1:2.2.

[0035] 6. Material condensation The contact reactants are continuously introduced into the condenser 8 for condensation treatment, and the lower liquid temperature of the condenser 8 is controlled to be 70°C by adjusting the cooling water regulating valve of the condenser 8, so as to continuously obtain condensate, and continuously introduce it into the crude product tank 9 for temporary storage; the material in the crude product tank 9 is subsequently transported to the cracking section through the crude product pump 10 for cracking and co-production of trichloroethylene and tetrachloroethylene.

[0036] The above condensate was sampled and analyzed, and the specific composition and weight percentage were: tetrachloroethane 64%, pentachloroethane 9%, pentachlorobutadiene 1%, hexachlorobutadiene 1.3%, hexachloroethane 24%, and others 0.7%.

[0037] In the method for treating the distillation still liquid in the production of trichloroethylene in this embodiment, since the weight ratio of tetrachloroethane to the distillation still liquid during the treatment process is 2:1, based on the distillation still liquid content of 33.3wt%, the conversion rate of pentachlorobutadiene is 89.6%, and the conversion rate of hexachlorobutadiene is 87.4%.

[0038] Furthermore, the effective catalytic service life of the modified catalyst used in the present embodiment was tested. When the method and device for treating distillation kettle liquid in trichloroethylene production of the present embodiment are used and the distillation kettle liquid is continuously treated at 3,000 tons / year, the effective service life of the modified catalyst can reach 1.5 years; that is, under the condition of continuously treating the distillation kettle liquid at 3,000 tons / year, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0039] The processing device for rectifying kettle liquid in trichloroethylene production comprises: a tetrachloroethane tank 1, a rectifying kettle liquid tank 2, a tetrachloroethane feeding pump 3, a rectifying kettle liquid feeding pump 4, a vacuum pump 5, a distillation kettle 6, a catalytic reactor 7, a condenser 8, a crude product tank 9, and a crude product pump 10.

[0040] The bottom discharge port of the tetrachloroethane tank 1 is connected to the first feed port pipeline of the distillation kettle 6 via the tetrachloroethane feeding pump 3, so that the tetrachloroethane in the tetrachloroethane tank 1 is continuously fed into the distillation kettle 6.

[0041] The bottom discharge port of the distillation kettle liquid tank 2 is connected to the second feed port pipeline of the distillation kettle 6 through the distillation kettle liquid feeding pump 4, so that the distillation kettle liquid in the distillation kettle liquid tank 2 is continuously fed into the distillation kettle 6.

[0042] The air inlet at the upper part of the still 6 is connected to the nitrogen gas source pipeline so as to replace the air in the whole processing device system and keep the oxygen volume percentage in the whole processing device system less than 2%; the still 6 is also provided with a liquid level meter, and is interlocked with the tetrachloroethane feeding pump 3, the distillation kettle liquid feeding pump 4 and the regulating valves at the first feeding port and the second feeding port so as to control the continuous feeding of tetrachloroethane and the distillation kettle liquid into the still 6 during the material vaporization process and keep the liquid level in the still 6 at 75-80%; the top and bottom of the still 6 are also provided with a pressure gauge and a thermometer so as to monitor the pressure and temperature in the still 6 in real time; and the thermometer is interlocked with the heater of the still 6 so as to control and maintain the still temperature of the still 6 at 110-130°C and the top temperature at 100-120°C.

[0043] The top gas outlet of the distillation kettle 6 is connected to the first gas inlet pipeline on the top of the catalytic reactor 7 via a regulating valve and a flow meter, so that the vaporized compounds in the distillation kettle 6 can be continuously fed into the catalytic reactor 7 at a predetermined volume flow rate after being measured; at the same time, the chlorine gas source is connected to the second gas inlet pipeline on the top of the catalytic reactor 7 via a regulating valve and a flow meter, so that the chlorine gas can be continuously fed into the catalytic reactor 7 at a predetermined volume flow rate after being measured.

[0044] The catalytic reactor 7 is a shell-and-tube reactor; the catalytic reactor 7 is also equipped with a hot water tank 11 and a hot water pump 12. The lower shell-side liquid inlet of the catalytic reactor 7 is connected to the bottom outlet pipe of the hot water tank 11 through the hot water pump 12; the upper shell-side liquid outlet of the catalytic reactor 7 is connected to the top inlet pipe of the hot water tank 11; so that hot water can be used to control the temperature in the catalytic reactor 7 to 80-100°C; at the same time, the catalytic reactor 7 is also provided with a thermometer and a pressure gauge, so as to detect the temperature and pressure of the catalytic reactor 7 in real time.

[0045] The bottom discharge port of the catalytic reactor 7 is connected to the top feed port pipeline of the condenser 8, the bottom discharge port of the condenser 8 is connected to the top feed port pipeline of the crude product tank 9, and the bottom discharge port of the crude product tank 9 is connected to the cracking section via the crude product pump 10; so that the contact reactants are continuously introduced into the condenser 8 for condensation treatment, the condensate is introduced into the crude product tank 9 for temporary storage, and then transported to the cracking section via the crude product pump 10 for cracking and co-production of trichloroethylene and tetrachloroethylene.

[0046] The condenser 8 is equipped with cooling water supply and cooling water return pipelines. By supplying cooling water to the condenser 8, the lower liquid temperature of the condenser 8 is controlled to be 60-80°C; at the same time, the top air outlets of the condenser 8 and the crude product tank 9 are connected to the vacuum pump 5 pipeline to continuously maintain the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6 of the processing device system in a negative pressure state.

[0047] Example 2 This embodiment provides a method and device for treating distillation kettle liquid in trichloroethylene production. The components and weight percentages of the trichloroethylene distillation kettle liquid used in this embodiment are: 25% tetrachloroethane, 7% pentachloroethane, 29% pentachlorobutadiene, 31% hexachlorobutadiene, 7% hexachloroethane, and 1% others. The tetrachloroethane feed liquid contains 97.5% tetrachloroethane, 1% pentachloroethane, 1% hexachloroethane, and 0.5% others.

[0048] The method for treating the rectification kettle liquid in the production of trichloroethylene comprises the following specific steps: 1. Preheating The inner diameter of the tube bundle is 50mm and the heat exchange area is 80m 2 The tubes of the tube-in-tube reactor (i.e., catalytic reactor 7) are filled with activated carbon modified catalyst (filling volume 1.2m 3 ); After the modified catalyst is loaded, a layer of activated carbon with a thickness of 10 cm is laid on the upper part of the catalytic reactor 7, and the nitrogen valve of the distillation kettle 6 is opened to replace the system with nitrogen until the volume percentage of oxygen in the system is less than 2%; then the hot water pump 12 of the catalytic reactor 7 is turned on, and the catalytic reactor 7 is heated at a rate of 22°C / h until the internal temperature of the catalytic reactor 7 reaches 95°C, and the temperature is kept for 6 hours, and then the nitrogen valve is closed to complete the preheating treatment.

[0049] Wherein, the preparation method of the modified catalyst is: 1) Preprocessing Activated carbon with an average particle size of 3-5 mm was added to an aqueous solution of 9% by mass of hydrochloric acid and 32% by mass of ethanol, and the temperature was raised to 38°C with stirring. The mixture was kept warm and stirred for 7 hours. The solid was filtered and washed with clean water to pH 6.5, and dried to obtain pretreated activated carbon.

[0050] Wherein, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:4.

[0051] 2) Composite treatment The pretreated activated carbon was immersed in an aqueous solution of 13% by mass of ferric chloride, 4% by mass of cupric chloride and 2% by mass of nickel chloride, and the temperature was raised to 42°C with stirring. After being kept stirring for 5 hours, the solid was filtered to obtain the solid. The solid was then calcined at 200°C for 9 hours under a nitrogen protection environment to obtain a modified catalyst.

[0052] Among them, the weight ratio of activated carbon to aqueous solution of ferric chloride, cupric chloride and nickel chloride is 1:4.

[0053] 2. Adding materials Turn on the tetrachloroethane feed pump 3 and the distillation kettle liquid feed pump 4, and add the tetrachloroethane in the tetrachloroethane tank 1 and the distillation kettle liquid in the distillation kettle liquid tank 2 to the distillation kettle 6 (kettle volume is 20m 3 ) and control the liquid level of tetrachloroethane and distillation kettle liquid in distillation kettle 6 to 78%.

[0054] Among them, the weight ratio of tetrachloroethane to distillation kettle liquid is 3:1.

[0055] 3. System negative pressure extraction Turn on the vacuum pump 5 to draw negative pressure to the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6 in the device system, and continue to maintain the negative pressure in the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6; specifically, keep the pressure before the vacuum pump 5 at -95KPa, the upper pressure of the crude product tank 9 at -94KPa, the upper pressure of the condenser 8 at -93KPa, the upper pressure of the catalytic reactor 7 at -90KPa, and the upper pressure of the distillation kettle 6 at -87KPa.

[0056] 4. Continuous vaporization of materials Slowly open the steam regulating valve of the still 6, heat the material in the still 6 at a heating rate of 32°C / h, heat the still 6 to a temperature of 125°C and a top temperature of 120°C, and continuously vaporize the material in the still 6 to obtain a vaporized mixture; and by adjusting the opening of the upper regulating valve of the still 6, control the volume flow rate of the vaporized mixture continuously introduced into the catalytic reactor 7 to be 30Nm 3 / h.

[0057] At the same time, during the material vaporization process, tetrachloroethane and distillation kettle liquid are continuously added into the still 6 at a weight ratio of 3:1 to maintain the liquid level in the still 6 at 78%.

[0058] In order to maintain the continuous and stable operation of the distillation still liquid treatment in the production of trichloroethylene, the non-volatile matter at the bottom of the still 6 is discharged after the material is vaporized continuously for 6 months.

[0059] 5. Continuous contact reaction While the vaporized mixture is introduced into the catalytic reactor 7, the chlorine regulating valve on the upper part of the catalytic reactor 7 is opened to control the volume flow rate of chlorine continuously introduced into the catalytic reactor 7 to be 10Nm 3 / h; and hot water is used to control the temperature in the catalytic reactor 7 to 80°C; the vaporized compound and chlorine gas are continuously contacted and reacted in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reactant, which is continuously introduced into the condenser 8.

[0060] The volume flow ratio of chlorine gas and vaporized mixture entering the catalytic reactor 7 is 1:3.

[0061] 6. Material condensation The contact reactants are continuously introduced into the condenser 8 for condensation treatment, and the lower liquid temperature of the condenser 8 is controlled to be 72° C. by adjusting the cooling water regulating valve of the condenser 8, so as to continuously obtain condensate, and continuously introduce it into the crude product tank 9 for temporary storage; the material in the crude product tank 9 is subsequently transported to the cracking section through the crude product pump 10 for cracking and co-production of trichloroethylene and tetrachloroethylene.

[0062] The above condensate was sampled and analyzed, and the specific composition and weight percentage were: tetrachloroethane 72%, pentachloroethane 7%, pentachlorobutadiene 1.1%, hexachlorobutadiene 1.4%, hexachloroethane 18%, and others 0.5%.

[0063] In the method for treating the distillation still liquid in the production of trichloroethylene in this embodiment, since the weight ratio of tetrachloroethane to the distillation still liquid during the treatment process is 3:1, based on the distillation still liquid content of 25wt%, the conversion rate of pentachlorobutadiene is 84.8%, and the conversion rate of hexachlorobutadiene is 81.9%.

[0064] Furthermore, the effective catalytic service life of the modified catalyst used in the present embodiment was tested. When the method and device for treating distillation kettle liquid in trichloroethylene production of the present embodiment are used and the distillation kettle liquid is continuously treated at 3,000 tons / year, the effective service life of the modified catalyst can reach 1.5 years; that is, under the condition of continuously treating the distillation kettle liquid at 3,000 tons / year, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0065] The device for treating the distillation kettle liquid in the production of trichloroethylene is the same as that in Example 1.

[0066] Example 3 This embodiment provides a method and device for treating distillation kettle liquid in trichloroethylene production. The components and weight percentages of the trichloroethylene distillation kettle liquid used in this embodiment are: 25% tetrachloroethane, 7% pentachloroethane, 29% pentachlorobutadiene, 31% hexachlorobutadiene, 7% hexachloroethane, and 1% others. The tetrachloroethane feed liquid contains 97.5% tetrachloroethane, 1% pentachloroethane, 1% hexachloroethane, and 0.5% others.

[0067] The method for treating the rectification kettle liquid in the production of trichloroethylene comprises the following specific steps: 1. Preheating The inner diameter of the tube bundle is 50mm and the heat exchange area is 80m 2 The tubes of the tube-in-tube reactor (i.e., catalytic reactor 7) are filled with activated carbon modified catalyst (filling volume 1.2m 3); After the modified catalyst is loaded, a layer of activated carbon with a thickness of 10 cm is laid on the upper part of the catalytic reactor 7, and the nitrogen valve of the distillation kettle 6 is opened to replace the system with nitrogen until the volume percentage of oxygen in the system is less than 2%; then the hot water pump 12 of the catalytic reactor 7 is turned on, and the catalytic reactor 7 is heated at a rate of 25°C / h until the internal temperature of the catalytic reactor 7 reaches 100°C, and the temperature is kept for 8 hours, and then the nitrogen valve is closed to complete the preheating treatment.

[0068] Wherein, the preparation method of the modified catalyst is: 1) Preprocessing Add activated carbon with an average particle size of 3-5 mm to an aqueous solution of 8% by mass of hydrochloric acid and 30% by mass of ethanol, stir and heat to 35°C, keep stirring for 6 hours, filter to obtain the solid, wash with clean water to pH 7.0, and dry to obtain pretreated activated carbon.

[0069] Wherein, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:5.

[0070] 2) Composite treatment The pretreated activated carbon was immersed in an aqueous solution of 10% by mass ferric chloride, 3% by mass cupric chloride and 1% by mass nickel chloride, heated to 40°C with stirring, kept stirring for 3 hours, and then filtered to obtain a solid; then, the solid was calcined at 180°C for 10 hours under a nitrogen protection environment to obtain a modified catalyst.

[0071] Among them, the weight ratio of activated carbon to the aqueous solution of ferric chloride, cupric chloride and nickel chloride is 1:5.

[0072] 2. Adding materials Turn on the tetrachloroethane feed pump 3 and the distillation kettle liquid feed pump 4, and add the tetrachloroethane in the tetrachloroethane tank 1 and the distillation kettle liquid in the distillation kettle liquid tank 2 to the distillation kettle 6 (kettle volume is 20m 3 ) and control the liquid level of tetrachloroethane and distillation kettle liquid in the distillation kettle 6 to 80%.

[0073] The weight ratio of tetrachloroethane to distillation kettle liquid is 2:1.

[0074] 3. System negative pressure extraction Turn on the vacuum pump 5 to draw negative pressure to the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6 in the device system, and continue to maintain the negative pressure in the crude product tank 9, condenser 8, catalytic reactor 7 and distillation kettle 6; specifically, keep the pressure before the vacuum pump 5 at -95KPa, the upper pressure of the crude product tank 9 at -94KPa, the upper pressure of the condenser 8 at -93KPa, the upper pressure of the catalytic reactor 7 at -90KPa, and the upper pressure of the distillation kettle 6 at -87KPa.

[0075] 4. Continuous vaporization of materials Slowly open the steam regulating valve of the still 6, heat the material in the still 6 at a heating rate of 30°C / h, heat the still 6 to a temperature of 120°C and a top temperature of 115°C, and continuously vaporize the material in the still 6 to obtain a vaporized mixture; and by adjusting the opening of the upper regulating valve of the still 6, control the volume flow rate of the vaporized mixture continuously introduced into the catalytic reactor 7 to be 20Nm 3 / h.

[0076] At the same time, during the material vaporization process, tetrachloroethane and distillation kettle liquid are continuously added into the still 6 at a weight ratio of 2:1, and the liquid level in the still 6 is maintained at 80%.

[0077] In order to maintain the continuous and stable operation of the distillation still liquid treatment in the production of trichloroethylene, the non-volatile matter at the bottom of the still 6 is discharged after the material is vaporized continuously for 6 months.

[0078] 5. Continuous contact reaction While the vaporized mixture is introduced into the catalytic reactor 7, the chlorine regulating valve on the upper part of the catalytic reactor 7 is opened to control the volume flow rate of chlorine gas continuously introduced into the catalytic reactor 7 to be 9Nm 3 / h; and hot water is used to control the temperature in the catalytic reactor 7 to 90°C; the vaporized compound and chlorine gas are continuously contacted and reacted in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reactant, which is continuously introduced into the condenser 8.

[0079] The volume flow ratio of chlorine gas to vaporized mixture entering the catalytic reactor 7 is 1:2.2.

[0080] 6. Material condensation The contact reactants are continuously introduced into the condenser 8 for condensation treatment, and the lower liquid temperature of the condenser 8 is controlled to be 70°C by adjusting the cooling water regulating valve of the condenser 8, so as to continuously obtain condensate, and continuously introduce it into the crude product tank 9 for temporary storage; the material in the crude product tank 9 is subsequently transported to the cracking section through the crude product pump 10 for cracking and co-production of trichloroethylene and tetrachloroethylene.

[0081] The above condensate was sampled and analyzed, and the specific composition and weight percentage were: tetrachloroethane 63%, pentachloroethane 9%, pentachlorobutadiene 0.7%, hexachlorobutadiene 0.9%, hexachloroethane 25%, and others 1.4%.

[0082] In the method for treating the distillation kettle liquid in the production of trichloroethylene in this embodiment, since the weight ratio of tetrachloroethane to the distillation kettle liquid during the treatment process is 2:1, based on the distillation kettle liquid content of 33.3wt%, the conversion rate of pentachlorobutadiene is 92.8%, and the conversion rate of hexachlorobutadiene is 91.3%.

[0083] Furthermore, the effective catalytic service life of the modified catalyst used in the present embodiment was tested. When the method and device for treating distillation kettle liquid in trichloroethylene production of the present embodiment are used and the distillation kettle liquid is continuously treated at 3,000 tons / year, the effective service life of the modified catalyst can reach 1.5 years; that is, under the condition of continuously treating the distillation kettle liquid at 3,000 tons / year, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0084] The device for treating the distillation kettle liquid in the production of trichloroethylene is the same as that in Example 1.

[0085] Comparative Example 1 Comparative Example 1 adopts the technical solution of Example 3, except that unmodified activated carbon is used instead of the modified catalyst.

[0086] In Comparative Example 1, the condensate was sampled and analyzed, and the specific components and weight percentages were: tetrachloroethane 73%, pentachloroethane 3%, pentachlorobutadiene 9.5%, hexachlorobutadiene 10%, hexachloroethane 3.7%, and others 0.8%.

[0087] In the method for treating the distillation kettle liquid in the production of trichloroethylene of Comparative Example 1, since the weight ratio of tetrachloroethane to the distillation kettle liquid during the treatment process is 2:1, the conversion rate of pentachlorobutadiene is 1.6% and the conversion rate of hexachlorobutadiene is 3.1% calculated based on the distillation kettle liquid content of 33.3wt%.

[0088] Unless otherwise specified, all percentages used in the present invention are by mass.

[0089] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production, characterized in that: The process includes the following steps: adding materials, pumping negative pressure from the system, continuous vaporization of materials, continuous contact reaction, and condensation of materials; The method of adding materials is as follows: tetrachloroethane and distillation kettle liquid are added into the distillation kettle (6) at the same time; and the liquid levels of tetrachloroethane and distillation kettle liquid in the distillation kettle (6) are controlled to 75-80%; The distillation kettle liquid includes: tetrachloroethane, pentachloroethane, pentachlorobutadiene, hexachlorobutadiene, and hexachloroethane; The method of pumping negative pressure in the system is to maintain the internal pressure of each pressure vessel used in the negative pressure low temperature catalytic method within the range of -85KPa to -95KPa; The method for continuously vaporizing the material comprises: controlling the temperature of the distillation kettle (6) to rise under negative pressure, and continuously vaporizing the material in the distillation kettle (6) to obtain a vaporized mixture; The method of continuous contact reaction is to simultaneously introduce the vaporized mixture and chlorine into a catalytic reactor (7) filled with a modified catalyst, control the temperature in the catalytic reactor (7) to be 80-100° C., and continuously carry out the contact reaction to obtain a contact reactant; The preparation method of the modified catalyst comprises the following steps: pretreatment, composite treatment; The pretreatment method comprises adding activated carbon to an aqueous solution containing hydrochloric acid and ethanol, heating and stirring the solution, washing the solution with water, and drying the solution to obtain pretreated activated carbon. The composite treatment method is to add the pretreated activated carbon into an aqueous solution containing ferric chloride, cupric chloride and nickel chloride, heat and stir the mixture, and then calcine the mixture under nitrogen protection to obtain a modified catalyst. The contact reactants are condensed to obtain a condensate.

2. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: The method also includes: preheating before adding materials; The preheating method is to load the modified activated carbon into the catalytic reactor (7), then replace it with nitrogen, heat it to 90-100°C, and perform heat preservation treatment to complete the preheating.

3. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: In the added material, the weight ratio of tetrachloroethane to the distillation kettle liquid is 2-3:

1.

4. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: During the continuous vaporization of the material, the heating rate of the distillation kettle (6) is 30-35°C / h; The temperature of the distillation kettle (6) is raised to 110-130°C and the top temperature is 100-120°C.

5. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: While the material is continuously vaporizing, tetrachloroethane and distillation kettle liquid are continuously added into the still (6) at a weight ratio of 2-3:1 to maintain the liquid level in the still (6) at 75-80%.

6. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: In the continuous contact reaction, the volume flow ratio of chlorine gas to the vaporized mixture entering the catalytic reactor (7) is 1:2-3.

5.

7. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: During the condensation of the material, the condensate temperature is controlled at 60-80°C.

8. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: In the pretreatment, the particle size of the activated carbon is 3-5 mm; In the aqueous solution containing hydrochloric acid and ethanol, the mass percentage of hydrochloric acid is 8-10%, and the mass percentage of ethanol is 30-35%; The weight ratio of the activated carbon to the aqueous solution containing hydrochloric acid and ethanol is 1:3-5.

9. The negative pressure low temperature catalytic method for rectifying still liquid in trichloroethylene production according to claim 1, characterized in that: In the composite treatment, the aqueous solution containing ferric chloride, cupric chloride and nickel chloride has a ferric chloride content of 10-15wt%, a cupric chloride content of 3-5wt% and a nickel chloride content of 1-3wt%; The weight ratio of the pretreated activated carbon to the aqueous solution containing ferric chloride, cupric chloride and nickel chloride is 1:3-5.

10. A negative pressure low temperature catalytic device for rectifying still liquid in trichloroethylene production for realizing the method according to any one of claims 1 to 9, characterized in that: It comprises: a distillation kettle (6), a catalytic reactor (7), and a condenser (8); The first feed port and the second feed port of the distillation kettle (6) are respectively connected to the tetrachloroethane feed pipe and the distillation kettle liquid feed pipe, so that the tetrachloroethane and the distillation kettle liquid are continuously fed into the distillation kettle (6); The upper air inlet of the distillation kettle (6) is connected to a nitrogen gas source pipeline; The top gas outlet of the distillation kettle (6) is connected to the top first gas inlet pipeline of the catalytic reactor (7) so that the vaporized compounds in the distillation kettle (6) are continuously fed into the catalytic reactor (7); The second gas inlet at the top of the catalytic reactor (7) is connected to a chlorine gas source pipeline so that chlorine gas can be continuously fed into the catalytic reactor (7); The bottom discharge port of the catalytic reactor (7) is connected to the top feed port pipeline of the condenser (8) so that the contact reactants can be continuously introduced into the condenser (8) for material condensation.

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