A method and device for negative-pressure low-temperature catalysis of rectification kettle liquid in trichloroethylene production

Abstract

The present invention provides a negative-pressure low-temperature catalytic method and device for the rectification kettle liquid in trichloroethylene production, belonging to the field of trichloroethylene production. The negative-pressure low-temperature catalytic method for the rectification kettle liquid in trichloroethylene production includes the following steps: feeding, evacuating the system to negative pressure, continuously vaporizing the material, continuously contacting and reacting, and condensing the material. The negative-pressure low-temperature catalytic method and device for the rectification kettle liquid in trichloroethylene production of the present invention can effectively simplify the reaction process, improve the controllability, reduce the 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 rectification kettle liquid, and realize the effective treatment and recycling of the rectification kettle liquid in trichloroethylene production.

Description

Technical Field

[0001] The present invention relates to the field of trichloroethylene production, and particularly to a negative-pressure low-temperature catalytic method and device for distillation 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 trichloroethylene production. There is no prior art disclosure of a combined treatment technology that can effectively recycle all by-products (1,1,2,3,4-pentachloro-1,3-butadiene and perchloro-1,3-butadiene) in trichloroethylene production. In actual production, they are usually treated as distillation hazardous waste by qualified units or incinerated, which not only wastes a large amount of production raw materials and production energy consumption, but also generates a large amount of toxic waste during the incineration process, resulting in poor environmental friendliness.

[0003] Currently, the prior art only discloses a method for preparing 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 re-added before each reaction starts. At the same time, the reaction solution after the reaction using this method also needs to be subjected to treatment steps such as filtration, water washing, alkali washing, drying, and sublimation to finally obtain the hexachloroethane product. Its treatment process is complex, the controllability is poor, the equipment investment and floor area 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. After vaporizing the high-boiling substances, they are condensed with tetrachloroethane and then reacted with liquid chlorine. During the reaction with liquid chlorine, it is necessary to adjust the feeding rate of liquid chlorine in real time according to the temperature change in the reactor and control the reaction pressure not to exceed the threshold 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 the vaporization process. And after condensation and liquefaction, it needs to react with liquid chlorine under the conditions of a reaction temperature exceeding 220°C and a reaction pressure exceeding 400 KPa. This continuous vaporization and then condensation treatment method wastes a large amount of production energy consumption. And in the subsequent reaction with chlorine, it requires a high-temperature and high-pressure reaction environment, the production process is complex, difficult to control, and the reaction economy is poor. Summary of the Invention

[0005] To solve the technical problems existing in the prior art, the present invention provides a negative-pressure low-temperature catalytic method and device for the rectification kettle liquid in trichloroethylene production, which can effectively simplify the reaction process, improve the controllability, reduce the 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 rectification kettle liquid, and realize the effective treatment and recycling of the rectification kettle liquid in trichloroethylene production.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A negative-pressure low-temperature catalytic method for the rectification kettle liquid in trichloroethylene production includes the following steps: feeding, system vacuum pumping, continuous material vaporization, continuous contact reaction, and material condensation;

[0008] The feeding method is to simultaneously add tetrachloroethane and the rectification kettle liquid into the distillation kettle; and control the liquid level of tetrachloroethane and the rectification kettle liquid in the distillation kettle to 75-80%;

[0009] The rectification kettle liquid includes: tetrachloroethane, pentachloroethane, pentachlorobutadiene, hexachlorobutadiene, hexachloroethane;

[0010] The system vacuum pumping method is to keep the internal pressure of each pressure vessel used in the negative-pressure low-temperature catalytic method within the range of -85 KPa to -95 KPa;

[0011] The method of continuous material vaporization is to control the temperature of the distillation kettle to rise under negative pressure conditions, and perform continuous material vaporization treatment on the materials in the distillation kettle to obtain a vaporized mixture;

[0012] The method of continuous contact reaction is to simultaneously introduce the vaporized mixture and chlorine gas into a catalytic reactor filled with a modified catalyst, control the temperature in the catalytic reactor to be 80-100 °C, and continuously carry out contact reaction to obtain contact reaction products;

[0013] The preparation method of the modified catalyst consists of the following steps: pretreatment, composite treatment;

[0014] The pretreatment method is to add activated carbon into an aqueous solution containing hydrochloric acid and ethanol, heat and stir, then wash with water and dry to obtain pretreated activated carbon;

[0015] The composite treatment method is to add the pretreated activated carbon into an aqueous solution containing ferric chloride, copper chloride, and nickel chloride, heat and stir, and then calcine under nitrogen protection to obtain a modified catalyst;

[0016] The contact reaction products are condensed by material condensation to obtain a condensate mainly composed of tetrachloroethane, pentachloroethane, and hexachloroethane.

[0017] Further, before the feeding, it further includes: preheating;

[0018] The method of preheating is to load the modified activated carbon into the catalytic reactor, then conduct nitrogen replacement, heat up to 90 - 100 °C, and after heat preservation treatment, the preheating is completed.

[0019] Preferably, in the feeding, the weight ratio of tetrachloroethane to the rectification still liquid is 2 - 3:1.

[0020] Preferably, during the continuous vaporization of the material, the heating rate of the distillation still is 30 - 35 °C / h;

[0021] Heat up to the still temperature of the distillation still being 110 - 130 °C and the top temperature being 100 - 120 °C.

[0022] Preferably, during the continuous vaporization of the material, according to the weight ratio of 2 - 3:1, tetrachloroethane and the rectification still liquid are continuously fed into the distillation still to keep the liquid level in the distillation still at 75 - 80%.

[0023] Preferably, during the continuous contact reaction, the volume flow ratio of chlorine gas to the vaporized mixture entering the catalytic reactor is 1:2 - 3.5;

[0024] Preferably, during the condensation of the material, the temperature of the condensate is controlled at 60 - 80 °C.

[0025] Preferably, in the pretreatment, the particle size of the activated carbon is 3 - 5 mm;

[0026] 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%;

[0027] The weight ratio of the activated carbon to the aqueous solution containing hydrochloric acid and ethanol is 1:3 - 5.

[0028] Preferably, in the composite treatment, the content of ferric chloride in the aqueous solution containing ferric chloride, copper chloride, and nickel chloride is 10 - 15 wt%, the content of copper chloride is 3 - 5 wt%, and the content of nickel chloride is 1 - 3 wt%;

[0029] The weight ratio of the pretreated activated carbon to the aqueous solution containing ferric chloride, copper chloride, and nickel chloride is 1:3 - 5.

[0030] A negative pressure low - temperature catalytic device for the rectification still liquid in the production of trichloroethylene implementing the foregoing method, including: a distillation still, a catalytic reactor, and a condenser;

[0031] The first feed port and the second feed port of the distillation still are respectively connected to the tetrachloroethane feed pipe and the rectification still liquid feed pipe, so that tetrachloroethane and the rectification still liquid are continuously fed into the distillation still;

[0032] The upper gas inlet of the distillation still is connected to the nitrogen gas source pipeline;

[0033] The top gas outlet of the distillation still is connected to the top first gas inlet of the catalytic reactor through a pipeline; so that the vaporized compounds in the distillation still can be continuously fed into the catalytic reactor;

[0034] The top second gas inlet of the catalytic reactor is connected to the chlorine gas source pipeline, so that chlorine gas can be continuously fed into the catalytic reactor;

[0035] The bottom discharge port of the catalytic reactor is connected to the top feed port of the condenser through a pipeline, so that the contacted reactants can be continuously introduced into the condenser for material condensation.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The negative pressure low-temperature catalytic method and device for the rectification kettle liquid in the production of trichloroethylene of the present invention change the traditional liquid-liquid contact reaction mode, adopt the gas-phase contact reaction mode, vaporize the rectification kettle liquid under negative pressure and carry out a gas-phase reaction with chlorine in a catalytic reactor filled with a catalyst; at the same time, in cooperation with the modified catalyst prepared by pretreatment and composite treatment, it can effectively realize long-term continuous reaction on an industrial scale without frequent catalyst replacement; at the same time, adopting the negative pressure reaction mode can effectively reduce the boiling point of the material while avoiding affecting the normal reaction, and reduce the consumption of heat medium (such as hot water) and cold medium (such as cooling water); each technical means cooperates with each other and acts synergistically, which can effectively simplify the treatment reaction process of the rectification kettle liquid in the production of trichloroethylene, improve the controllability, reduce the 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 rectification kettle liquid, and realize the effective treatment and recycling of the rectification kettle liquid in the production of trichloroethylene.

[0038] (2) The negative pressure low-temperature catalytic method and device for the rectification kettle liquid in the production of trichloroethylene of the present invention change the traditional liquid-liquid contact reaction mode, adopt the gas-phase contact reaction mode, and make the vaporized mixture of tetrachloroethane and the rectification kettle liquid react with chlorine; compared with the traditional liquid-liquid contact reaction mode (in the treatment process of liquid chlorine, -35°C frozen brine needs to be used for condensation), it further reduces the production energy consumption, simplifies the process flow, reduces the requirements for related devices and auxiliary pipelines, and effectively reduces the production input.

[0039] (3) The negative-pressure low-temperature catalytic method and device for the rectification kettle liquid in trichloroethylene production of the present invention, after treating the rectification kettle liquid in trichloroethylene production, through the analysis of the reaction liquid (i.e., condensate), it shows that pentachlorobutadiene and hexachlorobutadiene in the original rectification kettle liquid can be effectively converted into pentachloroethane and hexachloroethane. The conversion rate of pentachlorobutadiene can reach 92.8%, and the conversion rate of hexachlorobutadiene can reach 91.3%. The condensate obtained by treatment can be used as raw material to produce trichloroethylene and tetrachloroethylene again, effectively realizing the recycling of the rectification kettle liquid in trichloroethylene production.

[0040] (4) The negative-pressure low-temperature catalytic method and device for the rectification kettle liquid in trichloroethylene production of the present invention, under the working condition of continuously treating 3000 tons / year of rectification kettle liquid, the effective service life of the modified catalyst used can reach 1.5 years. During the 1.5 years of continuous operation of the device, there is no need to replace the modified catalyst in the catalytic reactor, effectively reducing the equipment maintenance difficulty and improving the treatment efficiency of the rectification kettle liquid in trichloroethylene production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the treatment device for the rectification kettle liquid in trichloroethylene production in Example 1;

[0042] In the figure, 1 - tetrachloroethane tank; 2 - rectification kettle liquid tank; 3 - tetrachloroethane feeding pump; 4 - rectification 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 OF THE INVENTION

[0043] In order to have a clearer understanding of the technical features, objectives and effects of the present invention, the specific embodiments of the present invention will be described below.

[0044] Example 1

[0045] This example provides a treatment method and device for the rectification kettle liquid in trichloroethylene production. The composition and weight percentage content of the trichloroethylene rectification kettle liquid used in this example are as follows: tetrachloroethane 25%, pentachloroethane 7%, pentachlorobutadiene 29%, hexachlorobutadiene 31%, hexachloroethane 7%, others 1%. In the tetrachloroethane liquid, tetrachloroethane is 97.5%, pentachloroethane is 1%, hexachloroethane is 1%, and others are 0.5%.

[0046] The treatment method for the rectification kettle liquid in trichloroethylene production specifically includes the following steps:

[0047] 1. Preheating

[0048] In the tube bundle with an inner diameter of 50 mm and a heat transfer area of 80 m 2In the tubes of the shell-and-tube reactor (i.e., the catalytic reactor 7), activated carbon modified catalyst is filled (loading amount 1.2 m 3 ); after the modified catalyst is filled, a layer of activated carbon with a thickness of 10 cm is laid on the upper part of the catalytic reactor 7. The nitrogen valve of the distillation kettle 6 is opened to conduct nitrogen replacement for the system until the volume percentage of oxygen in the system is less than 2%; then the hot water pump 12 supporting the catalytic reactor 7 is started, 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 it is kept warm for 5 h, and then the nitrogen valve is closed to complete the preheating treatment.

[0049] Among them, the preparation method of the modified catalyst is as follows:

[0050] 1) Pretreatment

[0051] Add activated carbon with an average particle size of 3 mm into an aqueous solution with a hydrochloric acid mass percentage of 10% and an ethanol mass percentage of 30%, stir and heat up to 40 °C, keep warm and stir for 8 h, filter to obtain solid matter, then wash it with clear water until the pH is 6.5, and dry it to obtain pretreated activated carbon.

[0052] Among them, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:3.

[0053] 2) Composite treatment

[0054] Soak the pretreated activated carbon in an aqueous solution of 15% ferric chloride, 5% copper chloride, and 3% nickel chloride, stir and heat up to 45 °C, keep warm and stir for 4 h, then filter to obtain solid matter; then under the protection of a nitrogen environment, calcine the solid matter at 210 °C for 8 h to obtain the modified catalyst.

[0055] Among them, the weight ratio of activated carbon to ferric chloride, copper chloride, and nickel chloride aqueous solution is 1:3.

[0056] 2. Feeding

[0057] Open the tetrachloroethane feeding pump 3 and the rectification kettle liquid feeding pump 4, and simultaneously add the tetrachloroethane in the tetrachloroethane tank 1 and the rectification kettle liquid in the rectification kettle liquid tank 2 into the distillation kettle 6 (the volume of the kettle is 20 m 3 ); and control the liquid levels of the tetrachloroethane and the rectification kettle liquid in the distillation kettle 6 to 75%.

[0058] Among them, the weight ratio of tetrachloroethane to rectification kettle liquid is 2:1.

[0059] 3. System evacuation to negative pressure

[0060] Turn on the vacuum pump 5 to draw negative pressure on the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6 in the device system, and continuously maintain a negative pressure state in the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6; specifically, maintain the pressure in front of the vacuum pump 5 at -95 KPa, the pressure on the upper part of the crude product tank 9 at -94 KPa, the pressure on the upper part of the condenser 8 at -93 KPa, the pressure on the upper part of the catalytic reactor 7 at -90 KPa, and the pressure on the upper part of the distillation kettle 6 at -87 KPa.

[0061] 4. Continuous vaporization of the material

[0062] Slowly open the steam regulating valve of the distillation kettle 6, heat the material in the distillation kettle 6 at a heating rate of 30 °C / h until the kettle temperature of the distillation kettle 6 reaches 120 °C and the top temperature reaches 115 °C. Continuously perform material vaporization treatment on the material in the distillation kettle 6 to obtain a vaporized mixture; and by adjusting the opening degree of the regulating valve on the upper part of the distillation kettle 6, control the volume flow rate of the vaporized mixture continuously introduced into the catalytic reactor 7 to be 30 Nm 3 / h.

[0063] Meanwhile, during the material vaporization process, trichloroethane and the rectification kettle liquid are continuously fed into the distillation kettle 6 at a weight ratio of 2:1, and the liquid level in the distillation kettle 6 is maintained at 75%.

[0064] To maintain the continuous and stable operation of the rectification kettle liquid treatment in trichloroethylene production, after continuously performing material vaporization for 6 months, discharge the non-volatile substances at the bottom of the distillation kettle 6 once.

[0065] 5. Continuous contact reaction

[0066] While the vaporized mixture is introduced into the catalytic reactor 7, open the chlorine regulating valve on the upper part of the catalytic reactor 7, and control the volume flow rate of chlorine continuously introduced into the catalytic reactor 7 to be 13.5 Nm 3 / h; and use hot water to control the temperature in the catalytic reactor 7 at 80 °C; the vaporized compound and chlorine continuously undergo a contact reaction in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reaction product, which is continuously introduced into the condenser 8.

[0067] Among them, the volume flow ratio of chlorine to the vaporized mixture entering the catalytic reactor 7 is 1:2.2.

[0068] 6. Material condensation

[0069] The contact reaction product is continuously introduced into the condenser 8 for condensation treatment, and by adjusting the cooling water regulating valve of the condenser 8, control the temperature of the liquid flowing out of the condenser 8 at 70 °C, 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 by the crude product pump 10 for cracking to co-produce trichloroethylene and tetrachloroethylene.

[0070] The foregoing condensate is sampled and analyzed, and its specific component composition and weight percentage are as follows: tetrachloroethane 64%, pentachloroethane 9%, pentachlorobutadiene 1%, hexachlorobutadiene 1.3%, hexachloroethane 24%, and others 0.7%.

[0071] In the method for treating the rectification still liquid in the production of trichloroethylene in this embodiment, since the weight ratio of tetrachloroethane to the rectification still liquid during the treatment process is 2:1, calculated based on the content of the rectification still liquid being 33.3 wt%, the conversion rate of pentachlorobutadiene is 89.6%, and the conversion rate of hexachlorobutadiene is 87.4%.

[0072] Furthermore, the effective catalytic service life of the modified catalyst used in this embodiment is tested. Under the condition of continuously treating 3000 tons / year of rectification still liquid by using the method and device for treating the rectification still liquid in the production of trichloroethylene in this embodiment, the effective service life of the modified catalyst can reach 1.5 years; that is to say, under the condition of continuously treating 3000 tons / year of rectification still liquid, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0073] The device for treating the rectification still liquid in the production of trichloroethylene includes: a tetrachloroethane tank 1, a rectification still liquid tank 2, a tetrachloroethane feeding pump 3, a rectification still 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.

[0074] The bottom discharge port of the tetrachloroethane tank 1 is connected to the first feed port of the distillation kettle 6 through the tetrachloroethane feeding pump 3, so that the tetrachloroethane in the tetrachloroethane tank 1 can be continuously fed into the distillation kettle 6.

[0075] The bottom discharge port of the rectification still liquid tank 2 is connected to the second feed port of the distillation kettle 6 through the rectification still liquid feeding pump 4, so that the rectification still liquid in the rectification still liquid tank 2 can be continuously fed into the distillation kettle 6.

[0076] The upper air inlet of the distillation kettle is connected to a nitrogen gas source pipeline to displace the air in the entire treatment device system and keep the volume percentage of oxygen in the entire treatment device system less than 2%; the distillation kettle 6 is also provided with a liquid level gauge, which is interlocked with the tetrachloroethane feeding pump 3, the rectification still liquid feeding pump 4, and the regulating valves at the first feed port and the second feed port, so as to control the continuous feeding of tetrachloroethane and rectification still liquid into the distillation kettle 6 during the material vaporization process and keep the liquid level in the distillation kettle 6 at 75 - 80%; pressure gauges and thermometers are also provided at the top and bottom of the distillation kettle 6 to monitor the pressure and temperature in the distillation kettle 6 in real time; and the thermometer is interlocked with the heater of the distillation kettle 6 to control and maintain the kettle temperature of the distillation kettle 6 at 110 - 130 °C and the top temperature at 100 - 120 °C.

[0077] The top gas outlet of the distillation still 6 is connected to the top first inlet of the catalytic reactor 7 through a regulating valve and a flow meter, so that the vaporized compounds in the distillation still 6 are continuously fed into the catalytic reactor 7 at a predetermined volume flow rate after being metered; meanwhile, the chlorine gas source is connected to the top second inlet of the catalytic reactor 7 through a regulating valve and a flow meter, so that chlorine is continuously fed into the catalytic reactor 7 at a predetermined volume flow rate after being metered.

[0078] 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 as to control the temperature in the catalytic reactor 7 at 80 - 100 °C with hot water; meanwhile, the catalytic reactor 7 is also provided with a thermometer and a pressure gauge to detect the temperature and pressure of the catalytic reactor 7 in real time.

[0079] The bottom discharge port of the catalytic reactor 7 is connected to the top feed port of the condenser 8 through a pipeline, the bottom discharge port of the condenser 8 is connected to the top feed port of the crude product tank 9 through a pipeline, and the bottom discharge port of the crude product tank 9 is connected to the cracking section through a crude product pump 10; so as to continuously introduce the contacting reactants into the condenser 8 for condensation treatment, and after the condensate is introduced into the crude product tank 9 for temporary storage, it is transported to the cracking section through the crude product pump 10 for co-production of trichloroethylene and tetrachloroethylene by cracking.

[0080] The condenser 8 is equipped with a cooling water supply and a cooling water return pipeline. By supplying cooling water to the condenser 8, the temperature of the lower liquid of the condenser 8 is controlled at 60 - 80 °C; meanwhile, the top gas outlets of the condenser 8 and the crude product tank 9 are connected to the vacuum pump 5, so as to continuously maintain a negative pressure state in the crude product tank 9, condenser 8, catalytic reactor 7, and distillation still 6 of the treatment device system.

[0081] Example 2

[0082] This example provides a method and device for treating the rectification kettle liquid in the production of trichloroethylene. The composition and weight percentage content of the trichloroethylene rectification kettle liquid used in this example are: tetrachloroethane 25%, pentachloroethane 7%, pentachlorobutadiene 29%, hexachlorobutadiene 31%, hexachloroethane 7%, and others 1%. In the tetrachloroethane feed liquid, tetrachloroethane is 97.5%, pentachloroethane is 1%, hexachloroethane is 1%, and others are 0.5%.

[0083] The method for treating the rectification kettle liquid in the production of trichloroethylene specifically includes the following steps:

[0084] 1. Preheating

[0085] In the tube bundle with an inner diameter of 50 mm and a heat transfer area of 80 m2 The tubular reactor (i.e., the catalytic reactor 7) is filled with an activated carbon modified catalyst in its tubes (the filling amount is 1.2 m 3 ); after the modified catalyst is filled, a layer of activated carbon with a thickness of 10 cm is laid on the upper part of the catalytic reactor 7. Then, the nitrogen valve of the distillation kettle 6 is opened to conduct nitrogen replacement for the system until the volume percentage of oxygen in the system is less than 2%; then, the hot water pump 12 supporting the catalytic reactor 7 is started, 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 it is kept warm for 6 h. Then, the nitrogen valve is closed to complete the preheating treatment.

[0086] Among them, the preparation method of the modified catalyst is as follows:

[0087] 1) Pretreatment

[0088] Activated carbon with an average particle size of 3 - 5 mm is added to an aqueous solution with a hydrochloric acid mass percentage of 9% and an ethanol mass percentage of 32%. Stir and heat it to 38 °C, keep stirring for 7 h, filter to obtain the solid, and then wash it with clear water until the pH is 6.5, and dry it to obtain the pretreated activated carbon.

[0089] Among them, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:4.

[0090] 2) Composite treatment

[0091] The pretreated activated carbon is soaked in an aqueous solution of 13% ferric chloride, 4% copper chloride, and 2% nickel chloride. Stir and heat it to 42 °C, keep stirring for 5 h, and then filter to obtain the solid; then, under the protection of a nitrogen environment, the solid is calcined at 200 °C for 9 h to obtain the modified catalyst.

[0092] Among them, the weight ratio of activated carbon to ferric chloride, copper chloride, and nickel chloride aqueous solution is 1:4.

[0093] 2. Feeding

[0094] Start the tetrachloroethane feeding pump 3 and the rectification kettle liquid feeding pump 4, and simultaneously add the tetrachloroethane in the tetrachloroethane tank 1 and the rectification kettle liquid in the rectification kettle liquid tank 2 to the distillation kettle 6 (the volume of the kettle is 20 m 3 ); and control the liquid levels of tetrachloroethane and rectification kettle liquid in the distillation kettle 6 to 78%.

[0095] Among them, the weight ratio of tetrachloroethane to rectification kettle liquid is 3:1.

[0096] 3. System evacuation

[0097] Turn on the vacuum pump 5 to draw negative pressure on the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6 in the device system, and continuously maintain a negative pressure state in the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6; specifically, maintain the pressure in front of the vacuum pump 5 at -95 KPa, the pressure on the upper part of the crude product tank 9 at -94 KPa, the pressure on the upper part of the condenser 8 at -93 KPa, the pressure on the upper part of the catalytic reactor 7 at -90 KPa, and the pressure on the upper part of the distillation kettle 6 at -87 KPa.

[0098] 4. Continuous vaporization of the material

[0099] Slowly open the steam regulating valve of the distillation kettle 6, heat the material in the distillation kettle 6 at a heating rate of 32 °C / h until the kettle temperature of the distillation kettle 6 reaches 125 °C and the top temperature reaches 120 °C. Continuously perform material vaporization treatment on the material in the distillation kettle 6 to obtain a vaporized mixture; and by adjusting the opening degree of the regulating valve on the upper part of the distillation kettle 6, control the volume flow rate of the vaporized mixture continuously introduced into the catalytic reactor 7 to be 30 Nm 3 / h.

[0100] At the same time, during the material vaporization process, add tetrachloroethane and rectification kettle liquid to the distillation kettle 6 continuously at a weight ratio of 3:1, and maintain the liquid level in the distillation kettle 6 at 78%.

[0101] To maintain the continuous and stable operation of the rectification kettle liquid treatment in the production of trichloroethylene, after continuously performing material vaporization for 6 months, discharge the non-volatile substances at the bottom of the distillation kettle 6 once.

[0102] 5. Continuous contact reaction

[0103] While the vaporized mixture is introduced into the catalytic reactor 7, open the chlorine regulating valve on the upper part of the catalytic reactor 7, and control the volume flow rate of chlorine continuously introduced into the catalytic reactor 7 to be 10 Nm 3 / h; and use hot water to control the temperature in the catalytic reactor 7 at 80 °C; the vaporized compound and chlorine continuously perform a contact reaction in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reaction product, and continuously introduce it into the condenser 8.

[0104] Among them, the volume flow ratio of chlorine to the vaporized mixture entering the catalytic reactor 7 is 1:3.

[0105] 6. Material condensation

[0106] The contact reaction product is continuously introduced into the condenser 8 for condensation treatment, and by adjusting the cooling water regulating valve of the condenser 8, control the lower liquid temperature of the condenser 8 at 72 °C, 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 by the crude product pump 10 for cracking to co-produce trichloroethylene and tetrachloroethylene.

[0107] The foregoing condensate is sampled and analyzed, and the specific component composition and weight percentage are as follows: tetrachloroethane 72%, pentachloroethane 7%, pentachlorobutadiene 1.1%, hexachlorobutadiene 1.4%, hexachloroethane 18%, and others 0.5%.

[0108] 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, and calculated based on the content of the distillation still liquid being 25 wt%, the conversion rate of pentachlorobutadiene is 84.8%, and the conversion rate of hexachlorobutadiene is 81.9%.

[0109] Furthermore, the effective catalytic service life of the modified catalyst used in this embodiment is tested. In the case of continuously treating 3000 tons / year of distillation still liquid by using the method and device for treating the distillation still liquid in the production of trichloroethylene in this embodiment, the effective service life of the modified catalyst can reach 1.5 years; that is to say, in the case of continuously treating 3000 tons / year of distillation still liquid, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0110] The device for treating the distillation still liquid in the production of trichloroethylene is the same as that in Example 1.

[0111] Example 3

[0112] This embodiment provides a method and device for treating the distillation still liquid in the production of trichloroethylene. The component composition and weight percentage content of the trichloroethylene distillation still liquid used in this embodiment are as follows: tetrachloroethane 25%, pentachloroethane 7%, pentachlorobutadiene 29%, hexachlorobutadiene 31%, hexachloroethane 7%, and others 1%. In the tetrachloroethane feed liquid, tetrachloroethane is 97.5%, pentachloroethane is 1%, hexachloroethane is 1%, and others are 0.5%.

[0113] The method for treating the distillation still liquid in the production of trichloroethylene specifically comprises the following steps:

[0114] 1. Preheating

[0115] In the tubes of a shell-and-tube reactor (i.e., catalytic reactor 7) with a tube inner diameter of 50 mm and a heat transfer area of 80 m 2 activated carbon modified catalyst is filled (the filling amount is 1.2 m 3 ); after the filling of the modified catalyst is completed, 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 conduct nitrogen replacement on the system until the volume percentage of oxygen in the system is less than 2%; then the hot water pump 12 supporting the catalytic reactor 7 is started, 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 it is kept warm for 8 h, and then the nitrogen valve is closed to complete the preheating treatment.

[0116] Among them, the preparation method of the modified catalyst is:

[0117] 1) Pretreatment

[0118] Add activated carbon with an average particle size of 3 - 5 mm into an aqueous solution containing 8% hydrochloric acid and 30% ethanol by mass percentage, stir and heat to 35°C, keep stirring for 6 h, filter to obtain solid matter, wash it with clear water until the pH reaches 7.0, and dry it to obtain pretreated activated carbon.

[0119] Among them, the weight ratio of activated carbon to hydrochloric acid and ethanol aqueous solution is 1:5.

[0120] 2) Composite treatment

[0121] Soak the pretreated activated carbon in an aqueous solution containing 10% ferric chloride, 3% copper chloride, and 1% nickel chloride by mass fraction, stir and heat to 40°C, keep stirring for 3 h, then filter to obtain solid matter; then calcine the solid matter at 180°C for 10 h under a nitrogen protection environment to obtain a modified catalyst.

[0122] Among them, the weight ratio of activated carbon to ferric chloride, copper chloride, and nickel chloride aqueous solution is 1:5.

[0123] 2. Feeding

[0124] Open the tetrachloroethane feeding pump 3 and the rectification still liquid feeding pump 4, and simultaneously add the tetrachloroethane in the tetrachloroethane tank 1 and the rectification still liquid in the rectification still liquid tank 2 into the distillation kettle 6 (the volume of the kettle is 20 m 3 ) inside; and control the liquid levels of tetrachloroethane and rectification still liquid in the distillation kettle 6 to 80%.

[0125] Among them, the weight ratio of tetrachloroethane to rectification still liquid is 2:1.

[0126] 3. System evacuation

[0127] Open the vacuum pump 5 to evacuate the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6 in the device system, and continuously maintain a negative pressure state in the crude product tank 9, condenser 8, catalytic reactor 7, and distillation kettle 6; specifically, keep the pressure in front of the vacuum pump 5 at -95 KPa, the pressure at the upper part of the crude product tank 9 at -94 KPa, the pressure at the upper part of the condenser 8 at -93 KPa, the pressure at the upper part of the catalytic reactor 7 at -90 KPa, and the pressure at the upper part of the distillation kettle 6 at -87 KPa.

[0128] 4. Continuous vaporization of materials

[0129] Slowly open the steam control valve of the distillation kettle 6, and heat the materials in the distillation kettle 6 at a heating rate of 30 °C / h until the kettle temperature of the distillation kettle 6 reaches 120 °C and the top temperature reaches 115 °C. Continuously vaporize the materials in the distillation kettle 6 to obtain a vaporized mixture; and control the volume flow rate of the continuously introduced vaporized mixture into the catalytic reactor 7 to be 20 Nm 3 / h.

[0130] Meanwhile, during the material vaporization process, trichloroethane and the rectification still liquid are continuously fed into the distillation kettle 6 at a weight ratio of 2:1, and the liquid level in the distillation kettle 6 is maintained at 80%.

[0131] To maintain the continuous and stable operation of the rectification still liquid treatment in trichloroethylene production, after continuously vaporizing the materials for 6 months, discharge the non-volatile substances at the bottom of the distillation kettle 6 once.

[0132] 5. Continuous contact reaction

[0133] While the vaporized mixture is introduced into the catalytic reactor 7, open the chlorine control valve at the upper part of the catalytic reactor 7, and control the volume flow rate of continuously introduced chlorine into the catalytic reactor 7 to be 9 Nm 3 / h; and use hot water to control the temperature in the catalytic reactor 7 to be 90 °C; the vaporized compound and chlorine continuously carry out a contact reaction in the catalytic reactor 7 in the presence of a modified catalyst to obtain a contact reaction product, and continuously introduce it into the condenser 8.

[0134] Among them, the volume flow ratio of chlorine to the vaporized mixture entering the catalytic reactor 7 is 1:2.2.

[0135] 6. Material condensation

[0136] The contact reaction product is continuously introduced into the condenser 8 for condensation treatment, and by adjusting the cooling water control valve of the condenser 8, control the temperature of the liquid flowing out of the condenser 8 to be 70 °C, continuously obtain condensate, and continuously introduce it into the crude product tank 9 for temporary storage; the materials in the crude product tank 9 are subsequently transported to the cracking section by the crude product pump 10 for cracking to co-produce trichloroethylene and tetrachloroethylene.

[0137] Sample and analyze the aforementioned condensate. The specific component composition and weight percentage are as follows: trichloroethane 63%, pentachloroethane 9%, pentachlorobutadiene 0.7%, hexachlorobutadiene 0.9%, hexachloroethane 25%, and others 1.4%.

[0138] In the treatment method of the rectification still liquid in the production of trichloroethylene in this embodiment, since the weight ratio of trichloroethane to the rectification still liquid during the treatment process is 2:1, calculated based on the rectification still liquid content of 33.3 wt%, the conversion rate of pentachlorobutadiene is 92.8%, and the conversion rate of hexachlorobutadiene is 91.3%.

[0139] Further, the effective catalytic service life of the modified catalyst used in this embodiment was tested. In the case of using the treatment method and device for the rectification still liquid in the production of trichloroethylene in this embodiment, under the condition of continuously treating 3000 tons / year of rectification still liquid, the effective service life of the modified catalyst can reach 1.5 years; that is to say, under the condition of continuously treating 3000 tons / year of rectification still liquid, the modified catalyst in the catalytic reactor 7 does not need to be replaced for at least 1.5 years.

[0140] The treatment device for the rectification still liquid in the production of trichloroethylene is the same as that in Embodiment 1.

[0141] Comparative Example 1

[0142] Comparative Example 1 adopted the technical solution of Embodiment 3, and the difference was that unmodified activated carbon was used to replace the modified catalyst.

[0143] In Comparative Example 1, the foregoing condensate was sampled and analyzed, and the specific component composition and weight percentage were: tetrachloroethane 73%, pentachloroethane 3%, pentachlorobutadiene 9.5%, hexachlorobutadiene 10%, hexachloroethane 3.7%, and others 0.8%.

[0144] In the treatment method of the rectification still liquid in the production of trichloroethylene in Comparative Example 1, since the weight ratio of tetrachloroethane to the rectification still liquid was 2:1 during the treatment process, calculated based on the rectification still liquid content of 33.3 wt%, the conversion rate of pentachlorobutadiene was 1.6%, and the conversion rate of hexachlorobutadiene was 3.1%.

[0145] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0146] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, 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: preheating, adding materials, system negative pressure extraction, continuous vaporization of materials, continuous contact reaction, and material condensation; 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 to complete the preheating; 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 is to control the temperature of the distillation kettle (6) to rise to 110-130° C. and the top temperature to 100-120° C. under negative pressure conditions, and continuously vaporize the material in the distillation kettle (6) to obtain a vaporized mixture; During the continuous vaporization of the material, the heating rate of the distillation kettle (6) is 30-35°C / h; 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: In the added material, the weight ratio of tetrachloroethane to the distillation kettle liquid is 2-3:

1.

3. 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%.

4. 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.

5. 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.

6. 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.

7. 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.

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