A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation

Abstract

The invention discloses a process for removing perfluoroisopropyl vinyl ether from perfluoro n-propyl vinyl ether by reactive distillation, belongs to the technical field of fluorine chemical industry, is carried out in a reactive distillation tower, a PPVE raw material containing i-PPVE is sent to the reaction section of the reactive distillation tower, a catalyst is filled in the reaction section, and i-PPVE is removed by selective reaction; the light component of the reaction product enters the distillation section of the reactive distillation tower and is removed from the top of the tower, and unreacted trace i-PPVE and PPVE are collected from the bottom of the tower. The present invention not only simplifies the process flow, thereby reducing reactor equipment and reducing costs; but also can improve the conversion rate of i-PPVE, thereby reducing the residual amount of i-PPVE in the distillation tower; and reduces energy consumption losses, and realizes the comprehensive utilization of energy.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether. Background Art

[0002] Perfluoro-n-propyl vinyl ether (PPVE for short) is an important comonomer of organic fluorine chemical materials, mainly used in the synthesis of fluorine-containing plastics to improve certain properties of polymers, such as low temperature resistance, solvent resistance, toughness, tear resistance, and adhesion to substrates. It is mainly used in the synthesis of fluorine-containing polymers (such as PFA, modified polytetrafluoroethylene, etc.). It can also be used to introduce organic fluorine functional groups into organic molecules for use in agriculture and pharmaceutical industries, and has broad market prospects.

[0003] PPVE is made of hexafluoropropylene oxide as raw material, and perfluoro-n-propoxy propionyl fluoride is prepared in polar solvent with metal halide as catalyst, and then it is obtained by decarboxylation and distillation. The preparation process is relatively complicated, so a certain amount of isomer impurities, i-PPVE (abbreviated as i-PPVE), are usually generated during the preparation process. Since the two are isomers, it is difficult to remove them by conventional separation methods. The isomer of i-PPVE has a strong chain transfer effect, which will cause PPVE and tetrafluoroethylene to generate low molecular weight copolymers in the polymerization reaction of copolymerizing fusible polytetrafluoroethylene PFA, making the performance of the obtained polymer worse. In today's market, the demand for high-quality PFA is increasing, so it is of great significance to control the content of i-PPVE in perfluoro-n-propyl vinyl ether within 0.1%.

[0004] The existing methods for reducing the isomer content in PPVE mainly include further heat treatment of the reaction product to remove perfluoroisopropyl vinyl ether, or adding an aromatic inhibitor at the front end of the reaction to inhibit the formation of isomers.

[0005] In U.S. Pat. No. 3,896,179 and U.S. Re 29,534, DuPont of the United States mainly heats the mixture composed of isomers to 250° C.-350° C., thermally decomposes perfluoroisopropyl vinyl ether (i-PPVE), and then removes the thermal decomposition product of perfluoroisopropyl vinyl ether (i-PPVE) by washing with a caustic solution and distilling, thereby reducing the isomer content in perfluoro-n-propyl vinyl ether (PPVE) to less than 0.1%, and obtaining high-purity perfluoro-n-propyl vinyl ether (PPVE). The recovery rate is about 90%, which will cause about 10% product loss. In the above content, it is necessary to use a reaction device, an alkali washing device and a distillation device, which makes the process complicated and the equipment investment high.

[0006] Patent CN111170835A discloses a method for catalytically removing perfluoroisopropyl vinyl ether from perfluoro n-propyl vinyl ether. The method uses an inert gas to bring a mixture of PPVE and i-PPVE into a fixed bed tubular furnace reactor equipped with a catalyst, and through reaction, i-PPVE is converted into a component with a large difference in boiling point from PPVE, and after distillation and purification, PPVE of not less than 99.0% is obtained, and after secondary distillation, PPVE of not less than 99.8% can be obtained. The catalyst is modified alumina, and the active components of metal hydroxide, cadmium salt and nickel salt are loaded, and OH- / Gd2+ / Ni2+ / Al2O3 catalyst is obtained after drying and high-temperature activation. The invention can basically remove i-PPVE from PPVE, and the generated by-products have a large difference in boiling point from PPVE. Through distillation and purification, high-purity PPVE can be obtained. The reaction operation is simple and the loss of PPVE is small. Although the invention can completely remove i-PPVE, it requires a reactor and two distillation towers. In industrial applications, the process is complicated, the equipment cost is high, and the yield is low.

[0007] Patent CN115043711A discloses a method for preparing perfluoro n-propyl vinyl ether. In order to overcome the problem of high content of isomer impurities in existing perfluoro n-propyl vinyl ether (PPVE) products, the invention provides a method for preparing perfluoro n-propyl vinyl ether with low isomer content, comprising the following steps: using hexafluoropropylene oxide to undergo addition reaction in a catalytic reaction system, wherein the catalytic reaction system comprises aromatic compounds, solvents and catalysts to obtain hexafluoropropylene oxide dimers; the hexafluoropropylene oxide dimers are subjected to salt formation and decarboxylation reaction with alkali metal carbonates to generate perfluoro n-propyl vinyl ether. The method for preparing perfluoro n-propyl vinyl ether provided by the invention can effectively control the generation of isomers in the product, control the isomer content to 0.1% or less, and improve the yield and purity of the product perfluoro n-propyl vinyl ether. This invention suppresses the production of hexafluoropropylene oxide dimer isomers by adding aromatic compounds in the synthesis stage, thereby reducing the amount of i-PPVE generated. However, it is actually unable to achieve the effect described in the patent, so it is also necessary to consider removing i-PPVE in the subsequent distillation of the PPVE product. Summary of the invention

[0008] In view of the defects of the prior art, the present invention provides a process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation, which simplifies the process flow and reduces the number of reactors and equipment.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation is carried out in a reactive distillation tower, wherein a PPVE raw material containing i-PPVE is fed into a reaction section of the reactive distillation tower, a catalyst is filled in the reaction section, and i-PPVE is removed by selective reaction in the reaction section; light components of the reaction product enter the distillation section of the reactive distillation tower and are removed from the tower top, and unreacted trace i-PPVE and PPVE are collected from the tower bottom.

[0011] Preferably, the catalyst is a Ni-based catalyst supported on an activated carbon carrier, wherein Ni is an active component and the auxiliary component includes one of Zn, Cu, Co, Fe, Mn, Al, Cr and Cd.

[0012] Preferably, the preparation method of the catalyst is:

[0013] (1) Modifying activated carbon to obtain a modified carbon carrier;

[0014] (2) adding the active component Ni salt solution and the auxiliary agent salt solution to the impregnation solution in proportion, adding the dispersant at the same time, stirring and strengthening until the salt solution is completely dissolved, and adding the modified carbon support;

[0015] (3) evaporating the impregnation solution until no obvious liquid is left, and then drying it under different atmospheres to obtain a uniformly dispersed precursor;

[0016] (4) placing the dried precursor in a muffle furnace for calcining;

[0017] (5) The calcined precursor is loaded into a tubular furnace, and the catalyst is reduced. After the reduction is completed, the prepared Ni-based catalyst supported on the activated carbon carrier is obtained.

[0018] Preferably, the activated carbon modification method in step (1) is: placing the activated carbon in a reactor, pre-treating it with dilute acid or dilute alkali, then washing it with deionized water until it is neutral, and ultrasonicating it for 10 minutes, and drying it at 80-120°C for 6-24 hours to obtain a modified carbon carrier; and / or evaporating the impregnation liquid at 60-100°C until there is no obvious liquid, and drying it at 80-120°C under different atmospheres for 2-12 hours to obtain a uniformly dispersed precursor; and / or, the Ni salt and auxiliary salt solution include one or more of the corresponding aqueous solutions of nitrates, acetates, chlorides, oxychlorates, phosphates, isopropoxides, and citrates.

[0019] Preferably, the calcination process in step (4) is protected by an inert gas, the calcination temperature is 450-500°C, and the calcination time is 4-12h; and / or, in step (5), the catalyst is reduced by N2 / H2, the reduction temperature is 350-400°C, and the reduction time is 4h.

[0020] Preferably, the reaction distillation tower has a pressure of 1.0-1.5 MPa, a reflux ratio of 20-50, a tower top temperature of <80°C, and a tower bottom temperature of 130-350°C.

[0021] Preferably, the distillation section uses structured packing and is located at the upper part of the tower, and the packing height is 1.0-3.0 meters; the reaction section uses structured packing and packaged catalysts arranged alternately and is located in the middle part of the tower, and the packing height is 1.0-3.0 meters.

[0022] Preferably, the structured packing of the reactive distillation tower is one of wire mesh corrugated packing or perforated plate corrugated packing.

[0023] Preferably, the feed position of the reactive distillation tower is the upper middle part of the reaction section.

[0024] Preferably, the PPVE raw material containing i-PPVE has a PPVE content of not less than 95% and an i-PPVE content of not more than 5%. After the reaction is completed, a PPVE product having an i-PPVE content of less than 0.1% is obtained from the bottom of the tower.

[0025] The technical solution of the present invention utilizes the reaction distillation technology to keyhole feed the PPVE raw material containing i-PPVE into a reaction distillation tower for reaction, which can reduce the i-PPVE in the raw PPVE to below 0.1%, and while removing the i-PPVE, its reaction product is directly reacted and removed from the reaction distillation tower, and finally a high-purity PPVE product with an i-PPVE content of less than 0.1% can be directly obtained in the tower bottom.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] In the traditional reaction to remove impurities to obtain high-purity products, a combination of reactor and distillation tower equipment is used. The reactive distillation technology can realize the reaction and distillation in a single distillation tower equipment at the same time, thereby simplifying the process flow, reducing one reaction equipment, and also reducing the pipes, valves, pumps and other accessories between equipment, thereby saving equipment investment costs while avoiding industrial problems such as leakage of accessories. At the same time, the reduction in the number of equipment can also save the area occupied by the equipment.

[0028] Secondly, since the removal of i-PPVE adopts reactive distillation technology, the reaction product can be directly removed by distillation while the i-PPVE is being removed, thereby shifting the reaction in the positive direction, thereby improving the conversion rate of i-PPVE and reducing the residual amount of i-PPVE in the distillation tower.

[0029] Then, since the boiling point difference between i-PPVE and PPVE is less than 1°C, it is difficult to separate them by conventional distillation. However, by using reactive distillation, i-PPVE can be removed in the reactive distillation tower equipment, and the light component by-products generated can be easily separated from PPVE. Therefore, the height of the reactive distillation tower can be reduced, and high-purity PPVE can be obtained through a single distillation at a relatively low tower height.

[0030] Finally, in the reaction distillation tower, the heat absorbed by the i-PPVE cracking reaction can be directly provided by the reboiler of the distillation tower, while the traditional reactor and distillation tower dual equipment requires heat sources to be provided on both equipment at the same time, making the thermal utility engineering more complicated. In addition, considering the heat loss between multiple equipment, energy consumption will increase. On the other hand, since the reaction is an endothermic reaction, the heat absorbed during the reaction cannot be effectively utilized in the traditional dual-equipment route, while the heat absorbed by the reaction in the reaction distillation tower can be used to reduce the load of the reaction distillation tower condenser. Combining the above two aspects, this process technology can reduce energy consumption losses and achieve comprehensive energy utilization.

[0031] Therefore, the present invention effectively removes i-PPVE in PPVE through reactive distillation technology, and directly separates PPVE from the reaction product, which not only simplifies the process flow, thereby reducing reactor equipment and reducing costs; but also can improve the conversion rate of i-PPVE, thereby reducing the residual amount of i-PPVE in the distillation tower; and reduce energy consumption losses, thereby realizing comprehensive energy utilization.

[0032] The specific technical solutions and beneficial effects of the present invention will be described in detail in the following specific embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0034] Figure 1 Schematic diagram of the reactive distillation tower used in the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the existing production of perfluoro n-propyl vinyl ether (PPVE), a certain amount of perfluoro isopropyl vinyl ether (i-PPVE) will be produced, and this substance has a strong chain transfer effect, which will seriously affect the performance of the polymer, so its content must be controlled within 0.1%. Since the boiling point of PPVE is 35°C and the boiling point of i-PPVE is 34.2°C, although the general distillation separation can be separated, the high distillation tower and energy consumption make it more expensive.

[0037] In order to reduce the i-PPVE content in existing PPVE raw materials, an embodiment of the present invention provides a process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation. The i-PPVE in PPVE is effectively removed by reactive distillation technology, and PPVE is directly separated from the reaction product.

[0038] like Figure 1 As shown, the reaction distillation tower 100 is used for the reaction, and the reaction process includes the following steps:

[0039] (1) A PPVE raw material containing a certain amount of i-PPVE is pumped into a reactive distillation tower.

[0040] Typically, the PPVE content is not less than 95%, and the i-PPVE content is not more than 5%.

[0041] (2) In the reaction section of the reaction distillation tower, i-PPVE is removed by selective reaction under the action of the catalyst. The light components of the reaction product enter the distillation section and are removed from the top of the tower. The unreacted trace i-PPVE and PPVE are collected from the bottom of the tower.

[0042] Wherein, the light components are tetrafluoroethylene, perfluoroacetyl fluoride, perfluoroacetone and other light components.

[0043] Preferably, the pressure of the reaction distillation tower is selected from 1.0-1.5MPa, the reflux ratio is selected from 20-50, the tower top temperature is selected from <80°C, and the tower bottom temperature is selected from 130-350°C. The distillation section adopts structured packing and is located at the top of the tower, and the packing height is 1.0-3.0 meters; the reaction section adopts structured packing and packaged catalysts arranged alternately and located in the middle of the tower, and the packing height is 1.0-3.0 meters. The structured packing of the reaction distillation tower is one of wire mesh corrugated packing or perforated plate corrugated packing. The feed position of the reaction distillation tower is the middle and upper part of the reaction section.

[0044] The above-mentioned process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation is to feed the PPVE raw material containing i-PPVE into a reactive distillation tower for reaction, thereby reducing the i-PPVE in the raw material PPVE to below 0.1%, and while removing the i-PPVE, its reaction product is directly reacted and removed from the reactive distillation tower, and finally a high-purity PPVE product with an i-PPVE content of less than 0.1% can be directly obtained in the tower bottom.

[0045] The catalyst in step (1) is a Ni-based catalyst supported on an activated carbon carrier, wherein Ni is an active component and the auxiliary agent includes one of Zn, Cu, Co, Fe, Mn, Al, Cr, and Cd.

[0046] The preparation method is as follows:

[0047] (1) The purchased commercial coconut shell charcoal activated carbon is placed in a reactor and pretreated with dilute acid or dilute alkali for a certain period of time under constant temperature reflux to completely remove residual heavy metal particles, obtain better metal ion adsorption performance and increase the oxygen-containing functional groups on the surface of the activated carbon. Then, it is washed with deionized water while hot until it is neutral. Subsequently, the neutral activated carbon sample is ultrasonicated for 10 minutes with an ultrasonic instrument at an ultrasonic intensity of 500w to reduce the ash content in the sample and remove unstable oxygen-containing functional groups on the surface. Finally, it is dried at 80-120°C for 6-24h to obtain the modified carbon carrier.

[0048] (2) Ni salt solution and precursor salt solution of any one of Zn, Cu, Co, Fe, Mn, Al, Cr, and Cd are added to an impregnation solution of a certain concentration in proportion, and a dispersant is added at the same time. The mixture is stirred and intensified until the salt solution is completely dissolved, and a modified activated carbon carrier is added. The mixture is stirred at a certain speed for 2 to 24 hours.

[0049] Wherein, the Ni salt solution and the precursor salt solution include one or more of the corresponding aqueous solutions of nitrate, acetate, chloride, oxychlorate, phosphate, isopropoxide, and citrate. Precursors of nitrate, acetate, chloride, etc. are further preferred. The dispersant can be selected from one of polyethylene glycol, sodium tripolyphosphate, sodium dodecyl sulfate, and polymethylsiloxane.

[0050] Preferably, the content of active components is 1 to 5% by weight, and the content of auxiliary agents is 0.01 to 1% by weight.

[0051] (3) The impregnation liquid is evaporated to dryness at 60-100°C until no obvious liquid is present, and then dried at 80-120°C under different atmospheres for 2-12 hours to obtain a uniformly dispersed precursor.

[0052] (4) The dried precursor is placed in a muffle furnace for calcination. The calcination process is protected by an inert gas such as nitrogen or argon. The calcination temperature is 450-500° C. and the calcination time is 4-12 hours.

[0053] (5) The calcined precursor is placed in a tubular furnace, and the catalyst is reduced by passing N2 / H2 (N2:H2=1-20:1) at a reduction temperature of 350-400°C for 4 hours. After the reduction is completed, the prepared Ni-based catalyst supported on the activated carbon carrier is obtained.

[0054] Example 1

[0055] The PPVE content in the raw material is 95.0%, the i-PPVE content is 5.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.5MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 34, the tower top temperature is 32.99°C, the tower bottom temperature is 140.21°C, the tower top exhaust volume is 8% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.9468%, the i-PPVE purity is 0.0532%, and the PPVE recovery rate is 96.84%.

[0056] Example 2

[0057] The PPVE content in the raw material is 95.0%, the i-PPVE content is 5.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.5MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 48, the tower top temperature is 21.87°C, the tower bottom temperature is 141.28°C, the tower top exhaust volume is 6% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.9180%, the i-PPVE purity is 0.0820%, and the PPVE recovery rate is 98.95%.

[0058] Example 3

[0059] The PPVE content in the raw material is 99.0%, the i-PPVE content is 1.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.5MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 47, the tower top temperature is 62.91°C, the tower bottom temperature is 142.3°C, the tower top exhaust volume is 5% of the feed amount, and the final PPVE purity collected in the bottom of the tower is 99.9731%, the i-PPVE purity is 0.0269%, and the PPVE recovery rate is 92.96%.

[0060] Example 4

[0061] The PPVE content in the raw material is 99.0%, the i-PPVE content is 1.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.5MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 33, the tower top temperature is 65.68°C, the tower bottom temperature is 139.49°C, the tower top exhaust volume is 5% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.9508%, the i-PPVE purity is 0.0492%, and the PPVE recovery rate is 90.27%.

[0062] Example 5

[0063] The PPVE content in the raw material is 98.0%, the i-PPVE content is 2.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.3MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 46, the tower top temperature is 54.37°C, the tower bottom temperature is 133.52°C, the tower top exhaust volume is 5% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.9153%, the i-PPVE purity is 0.0847%, and the PPVE recovery rate is 96.94%.

[0064] Example 6

[0065] The PPVE content in the raw material is 98.0%, the i-PPVE content is 2.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.1MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 45, the tower top temperature is 50.41°C, the tower bottom temperature is 125.98°C, the tower top exhaust volume is 6% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.8971%, the i-PPVE purity is 0.1039%, and the PPVE recovery rate is 98.29%.

[0066] Example 7

[0067] The PPVE content in the raw material is 96.0%, the i-PPVE content is 4.0%, the packing height of the reaction section of the reaction distillation tower is 3 meters, the packing height of the distillation section is 2 meters, the packing type is wire mesh corrugated regular packing, the catalyst is Ni-based catalyst, the tower pressure is 1.2MPa, the feed position is 1 / 3 of the reaction section packing, the reflux ratio is 38, the tower top temperature is 58.46°C, the tower bottom temperature is 129.86°C, the tower top exhaust volume is 7% of the feed amount, and the final PPVE purity collected in the tower bottom is 99.8910%, the i-PPVE purity is 0.1090%, and the PPVE recovery rate is 93.28%.

[0068] Combined with the technical solutions and application examples in the above specific implementations, compared with the prior art, the present invention has the following beneficial effects:

[0069] In the traditional reaction to remove impurities to obtain high-purity products, a combination of reactor and distillation tower equipment is used. The reactive distillation technology can realize the reaction and distillation in a single distillation tower equipment at the same time, thereby simplifying the process flow, reducing one reaction equipment, and also reducing the pipes, valves, pumps and other accessories between equipment, thereby saving equipment investment costs while avoiding industrial problems such as leakage of accessories. At the same time, the reduction in the number of equipment can also save the area occupied by the equipment.

[0070] Secondly, since the removal of i-PPVE adopts reactive distillation technology, the reaction product can be directly removed by distillation while the i-PPVE is being removed, thereby shifting the reaction in the positive direction, thereby improving the conversion rate of i-PPVE and reducing the residual amount of i-PPVE in the distillation tower.

[0071] Then, since the boiling point difference between i-PPVE and PPVE is less than 1°C, it is difficult to separate them by conventional distillation. However, by using reactive distillation, i-PPVE can be removed in the reactive distillation tower equipment, and the light component by-products generated can be easily separated from PPVE. Therefore, the height of the reactive distillation tower can be reduced, and high-purity PPVE can be obtained through a single distillation at a relatively low tower height.

[0072] Finally, in the reaction distillation tower, the heat absorbed by the i-PPVE cracking reaction can be directly provided by the reboiler of the distillation tower, while the traditional reactor and distillation tower dual equipment requires heat sources to be provided on both equipment at the same time, making the thermal utility engineering more complicated. In addition, considering the heat loss between multiple equipment, energy consumption will increase. On the other hand, since the reaction is an endothermic reaction, the heat absorbed during the reaction cannot be effectively utilized in the traditional dual-equipment route, while the heat absorbed by the reaction in the reaction distillation tower can be used to reduce the load of the reaction distillation tower condenser. Combining the above two aspects, this process technology can reduce energy consumption losses and achieve comprehensive energy utilization.

[0073] Therefore, the present invention effectively removes i-PPVE in PPVE through reactive distillation technology, and directly separates PPVE from the reaction product, which not only simplifies the process flow, thereby reducing reactor equipment and reducing costs; but also can improve the conversion rate of i-PPVE, thereby reducing the residual amount of i-PPVE in the distillation tower; and reduce energy consumption losses, thereby realizing comprehensive energy utilization.

[0074] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation, characterized in that: The process is carried out in a reactive distillation tower. A PPVE raw material containing i-PPVE is fed into a reaction section of the reactive distillation tower. A catalyst is filled in the reaction section. i-PPVE is removed by selective reaction in the reaction section. Light components of the reaction products enter the distillation section of the reactive distillation tower and are removed from the top of the tower. Unreacted trace i-PPVE and PPVE are collected from the bottom of the tower.

2. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 1, characterized in that: The catalyst is a Ni-based catalyst supported by an activated carbon carrier, wherein Ni is an active component and the auxiliary component comprises one of Zn, Cu, Co, Fe, Mn, Al, Cr and Cd.

3. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 2, characterized in that: The preparation method of the catalyst is: (1) Modifying activated carbon to obtain a modified carbon carrier; (2) adding the active component Ni salt solution and the auxiliary agent salt solution to the impregnation solution in proportion, adding the dispersant at the same time, stirring and strengthening until the salt solution is completely dissolved, and adding the modified carbon support; (3) evaporating the impregnation solution until no obvious liquid is left, and then drying it under different atmospheres to obtain a uniformly dispersed precursor; (4) placing the dried precursor in a muffle furnace for calcining; (5) The calcined precursor is loaded into a tubular furnace, and the catalyst is reduced. After the reduction is completed, the prepared Ni-based catalyst supported on the activated carbon carrier is obtained.

4. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 3, characterized in that: The activated carbon modification method in step (1) is as follows: placing the activated carbon in a reactor, pre-treating it with a dilute acid or a dilute alkali, then washing it with deionized water until it is neutral, ultrasonicating it for 10 minutes, and drying it at 80-120° C. for 6-24 hours to obtain a modified carbon carrier; And / or, the impregnation liquid is evaporated at 60-100°C until there is no obvious liquid, and dried at 80-120°C under different atmospheres for 2-12 hours to obtain a uniformly dispersed precursor; and / or, the Ni salt and auxiliary salt solution includes one or more corresponding aqueous solutions of nitrate, acetate, chloride, oxychlorate, phosphate, isopropoxide, and citrate.

5. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 3, characterized in that: In step (4), the calcination process is protected by inert gas, the calcination temperature is 450-500°C, and the calcination time is 4-12h; and / or, in step (5), the catalyst is reduced by N2 / H2, the reduction temperature is 350-400°C, and the reduction time is 4h.

6. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 1, characterized in that: The reaction distillation tower has a pressure of 1.0-1.5 MPa, a reflux ratio of 20-50, a tower top temperature of <80°C, and a tower bottom temperature of 130-350°C.

7. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 1, characterized in that: The distillation section uses structured packing and is located at the upper part of the tower, with a packing height of 1.0-3.0 meters; the reaction section uses structured packing and packaged catalysts arranged alternately and is located in the middle part of the tower, with a packing height of 1.0-3.0 meters.

8. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 7, characterized in that: The structured packing of the reaction distillation tower is one of wire mesh corrugated packing and perforated plate corrugated packing.

9. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 7, characterized in that: The feed position of the reaction distillation tower is the middle and upper part of the reaction section.

10. A process for removing perfluoroisopropyl vinyl ether from perfluoro-n-propyl vinyl ether by reactive distillation according to claim 1, characterized in that: The PPVE raw material containing i-PPVE has a PPVE content of not less than 95% and an i-PPVE content of not more than 5%. After the reaction is completed, a PPVE product having an i-PPVE content of less than 0.1% is obtained from the bottom of the tower.

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