Continuous process for the production of epichlorohydrin

Abstract

The present application relates to the field of epichlorohydrin production, and discloses a continuous production method of epichlorohydrin, which is carried out in a system composed of an in-use epoxidation reactor and a standby epoxidation reactor, and comprises the following steps: 1) feeding reaction raw materials to the in-use epoxidation reactor to contact with a catalyst; the reaction raw materials comprise 3-chloropropylene, an oxidizing agent and a solvent; 2) when the conversion rate of the oxidizing agent in the in-use epoxidation reactor is reduced to below 95%, the feeding of the solvent in the reaction raw materials is kept unchanged, and the feeding of the remaining reaction raw materials is switched to the standby epoxidation reactor; after the concentration of the oxidizing agent at the outlet of the in-use epoxidation reactor is reduced to below 50 ppm, the reaction raw materials are fed to the standby epoxidation reactor; 3) the in-use epoxidation reactor is cut out of the system for regeneration, and then is put into the system as a new standby epoxidation reactor; and 4) steps 1)-3) are repeated. The method can reduce the composition fluctuation of the product, reduce the safety risk, and be beneficial to subsequent extraction treatment.

Description

Technical Field

[0001] This invention relates to the field of epichlorohydrin production, and more specifically to a continuous production method for epichlorohydrin. Background Technology

[0002] Epichlorohydrin (ECH), also known as 1-chloro-2,3-epoxypropane, commonly called epichlorohydrin, is an important basic organic chemical product. ECH molecules contain epoxy groups and active chlorine, making them chemically reactive. Epoxy resins made from epichlorohydrin are characterized by strong adhesion, resistance to chemical corrosion, low shrinkage, good chemical stability, and high impact strength. The direct oxidation method for producing epichlorohydrin involves the epoxidation of allyl chloride with hydrogen peroxide using titanium-silicon molecular sieve catalysis, directly synthesizing epichlorohydrin in one step from allyl chloride.

[0003] CN101747296A discloses a method for producing epichlorohydrin, which includes contacting 3-chloropropene and hydrogen peroxide in the presence of a titanium silicate molecular sieve catalyst, an alkaline additive, and a solvent to produce epichlorohydrin.

[0004] CN105524028A discloses a method for synthesizing epichlorohydrin by oxidizing chloropropene. The method includes introducing 3-chloropropene, hydrogen peroxide, solvent and alkaline additive into two micro fixed-bed reactors connected in series and respectively loaded with different titanium silicate molecular sieve catalysts, so that 3-chloropropene and hydrogen peroxide can undergo an epoxidation reaction.

[0005] CN112209902A discloses an olefin epoxidation method that can significantly extend the single-pass reaction time of the catalyst by controlling the reaction temperature rise, while maintaining high hydrogen peroxide conversion and product selectivity. The single-pass epoxidation reaction time can be extended to 1640 hours while maintaining high epoxidation selectivity.

[0006] However, in actual production, the composition of epoxidation products is highly susceptible to fluctuations due to changes in catalyst activity and the regeneration process of the epoxidation reactor, which increases the difficulty of subsequent extraction processes. Direct discharge of oxidant-containing materials from the system also poses certain safety risks. Therefore, eliminating compositional fluctuations in epoxidation products and improving the safety of the reaction system are crucial for enhancing the stability and continuity of epichlorohydrin production. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of large compositional fluctuations in epoxidation products, poor stability and continuity in epichlorohydrin production, and safety risks in existing technologies, and to provide a continuous production method for epichlorohydrin. This method produces epoxidation products with small compositional fluctuations, good stability and continuity in epichlorohydrin production, and higher safety.

[0008] To achieve the above objectives, the present invention provides a continuous production method for epichlorohydrin, wherein the continuous production of epichlorohydrin is carried out in an epoxidation reaction system, the system comprising an in-use epoxidation reactor and a standby epoxidation reactor; the method comprising:

[0009] (1) The reaction raw materials are fed into an in-use epoxidation reactor and contacted with the catalyst to carry out an epoxidation reaction to obtain product I containing epichlorohydrin;

[0010] The reaction raw materials include 3-chloropropene, an oxidant, and a solvent;

[0011] (2) When the conversion rate of the oxidant in the working epoxidation reactor drops below 95%, the outlet of the working epoxidation reactor will be connected to the inlet of the standby epoxidation reactor.

[0012] Keeping the solvent feeding method in the reaction raw materials unchanged, the remaining reaction raw materials are fed to the standby epoxidation reactor; at this time, product II containing epichlorohydrin is obtained at the outlet of the standby epoxidation reactor; when the oxidant concentration at the outlet of the active epoxidation reactor drops to below 50 ppm, the reaction feed is switched, and all reaction raw materials are fed to the standby epoxidation reactor.

[0013] (3) The system will be cut out of the epoxidation reactor, the catalyst will be regenerated, and then the system will be put into the system as a new standby epoxidation reactor;

[0014] (4) Repeat steps (1)-(3) to achieve continuous production of epichlorohydrin.

[0015] Preferably, product I containing epichlorohydrin and product II containing epichlorohydrin each independently include epichlorohydrin, solvent, oxidant and impurity components; wherein, based on the epichlorohydrin content in product I containing epichlorohydrin, the fluctuation rate of the epichlorohydrin content in product II containing epichlorohydrin does not exceed 10%.

[0016] In actual production, the composition of epoxidized products is highly susceptible to fluctuations due to changes in catalyst activity and the regeneration process of the epoxidation reactor, which increases the difficulty of subsequent extraction processes. The continuous production method of epichlorohydrin provided by this invention feeds the reactants into an epoxidation system for the epoxidation reaction. This epoxidation system includes an in-service epoxidation reactor and a standby epoxidation reactor. Both reactors have parallel and series operation capabilities. By switching the reactor connections and feeding methods, fluctuations in product composition can be reduced, while avoiding safety risks caused by oxidant residue, which is beneficial for subsequent product extraction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an epoxidation reaction apparatus used in one embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures

[0019] 1. In-use epoxidation reactor; 2. Standby epoxidation reactor.

[0020] Solvent a1 is used in the solvent inlet of the epoxidation reactor.

[0021] a2 Backup epoxidation reactor solvent inlet b Oxidant

[0022] c. 3-Chloropropene d. Alkaline additive

[0023] e Feeding to the in-use epoxidation reactor; f Feeding to the standby epoxidation reactor

[0024] g is the discharge from the epoxidation reactor in use; h is the discharge from the standby epoxidation reactor.

[0025] 3. Heat exchanger unit for the in-use epoxidation reactor; 4. Heat exchanger unit for the standby epoxidation reactor. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] This invention provides a continuous production method for epichlorohydrin, wherein the continuous production of epichlorohydrin is carried out in an epoxidation reaction system, which consists of an in-use epoxidation reactor and a standby epoxidation reactor; the method includes:

[0028] (1) The reaction raw materials are fed into an in-use epoxidation reactor and contacted with the catalyst to carry out an epoxidation reaction to obtain product I containing epichlorohydrin;

[0029] The reaction raw materials include 3-chloropropene, an oxidant, and a solvent;

[0030] (2) When the conversion rate of the oxidant in the working epoxidation reactor drops below 95%, the outlet of the working epoxidation reactor will be connected to the inlet of the standby epoxidation reactor.

[0031] Keeping the solvent feeding method in the reaction raw materials unchanged, the remaining reaction raw materials are fed to the standby epoxidation reactor; at this time, product II containing epichlorohydrin is obtained at the outlet of the standby epoxidation reactor; when the oxidant concentration at the outlet of the active epoxidation reactor drops to below 50 ppm, the reaction feed is switched, and all reaction raw materials are fed to the standby epoxidation reactor.

[0032] (3) The system will be cut out of the epoxidation reactor, the catalyst in it will be regenerated, and then it will be put into the system as a new standby epoxidation reactor;

[0033] (4) Repeat steps (1)-(3) to achieve continuous production of epichlorohydrin.

[0034] In actual production, the composition of epoxidation products is highly susceptible to fluctuations due to changes in catalyst activity and the regeneration process of the epoxidation reactor. Understandably, subsequent product extraction requires adjustments based on the product composition. Even subtle compositional variations in industrial-scale production increase the difficulty of subsequent extraction processes. Compositional fluctuations can affect the phase equilibrium results of subsequent product extraction and separation, even leading to short-term miscibility, thus impacting the epichlorohydrin yield and the overall production continuity and batch stability. Furthermore, residual oxidant during conventional reactor switching can pose potential safety risks. The continuous epichlorohydrin production method provided by this invention feeds the reactants into an epoxidation system for the epoxidation reaction. This system includes an operational epoxidation reactor and a standby epoxidation reactor, both capable of parallel and series operation. By switching the reactor connections and feeding methods, fluctuations in product composition can be reduced. Solvents are used to replace some of the material in the epoxidation reactor requiring regeneration, minimizing the concentration of residual reactants, especially the oxidant, thus avoiding safety risks caused by oxidant residue and facilitating subsequent product extraction.

[0035] In this invention, the terms "in-use epoxidation reactor" and "standby epoxidation reactor" are not specific to any particular reactor, but are used only to distinguish between an operating epoxidation reactor and an idle standby epoxidation reactor. It is understood that when an in-use epoxidation reactor is regenerated and put back into the system, it becomes a new standby epoxidation reactor, and the corresponding original standby epoxidation reactor becomes a new in-use epoxidation reactor.

[0036] In this invention, the conversion rate of the oxidant is calculated using the following formula:

[0037] Oxidant conversion rate (%) = (mass of oxidant in feed - mass of oxidant in discharge) / mass of oxidant in feed × 100%.

[0038] In this invention, the concentration of the oxidant is determined by potassium permanganate titration.

[0039] According to the present invention, the above method can reduce fluctuations in product composition, thereby stabilizing the composition of the effluent product throughout the entire reaction process. In this invention, product I containing epichlorohydrin and product II containing epichlorohydrin refer to the system effluent before and during reactor switching, respectively. Each of product I and product II independently comprises epichlorohydrin, solvent, oxidant, and impurity components; wherein, based on the epichlorohydrin content in product I, the fluctuation rate of the epichlorohydrin content in product II does not exceed 10%, preferably not more than 5%, and more preferably not more than 1%; preferably, based on the solvent content in product I, the fluctuation rate of the solvent content in product II does not exceed 10%, preferably not more than 5%, and more preferably not more than 1%; preferably, based on the oxidant content in product I, the fluctuation rate of the oxidant content in product II does not exceed 10%, preferably not more than 5%, and more preferably not more than 1%.

[0040] Wherein, the volatility (%) of epichlorohydrin = (|epicohydrin content of product II of epichlorohydrin - epichlorohydrin content of product I of epichlorohydrin|) / epichlorohydrin content of product I of epichlorohydrin × 100%.

[0041] The volatility of oxidant (%) = (|Oxidant content in product II of epichlorohydrin - Oxidant content in product I of epichlorohydrin|) / Oxidant content in product I of epichlorohydrin × 100%;

[0042] The solvent volatility (%) = (|solvent content in product II of epichlorohydrin - solvent content in product I of epichlorohydrin|) / solvent content in product I of epichlorohydrin × 100%.

[0043] In this invention, the content of each component in product I containing epichlorohydrin and product II containing epichlorohydrin is determined by chromatography.

[0044] According to the present invention, it is understood that as the reaction time is prolonged, the conversion rate of the oxidant gradually decreases. In order to improve the regeneration effect, preferably, when the conversion rate of the oxidant in the working epoxidation reactor decreases to below 99%, preferably 95-99%, the outlet of the working epoxidation reactor is connected to the inlet of the standby epoxidation reactor; while keeping the feeding method of the solvent in the reaction raw materials unchanged, the remaining reaction raw materials are fed to the standby epoxidation reactor.

[0045] Preferably, when the concentration of the oxidant at the outlet of the epoxidation reactor decreases to below 30 ppm, the reaction feed is switched, and all reaction raw materials are fed into the standby epoxidation reactor.

[0046] In this invention, there are no particular limitations on the specific structure of the in-use epoxidation reactor and the standby epoxidation reactor; conventional equipment in the art can be used. Preferably, each of the in-use and standby epoxidation reactors is independently equipped with an epoxidation reaction heat exchange device, which includes a heat exchange medium for controlling the temperature of the epoxidation reaction. By adopting the above-mentioned preferred embodiment, the temperature difference between the reaction inlet and outlet can be better controlled, improving the selectivity of the target product and the raw material conversion rate, and extending the single-pass epoxidation reaction time.

[0047] Preferably, the epoxidation reaction heat exchange device includes a heat exchange medium circulation pump, and optionally a heat exchange medium cooler and a heat exchange medium buffer tank, wherein the heat exchange medium circulation pump is used to control the flow rate of the heat exchange medium in the epoxidation reaction heat exchange device.

[0048] According to a preferred embodiment of the present invention, when the epoxidation reaction heat exchange device includes a heat exchange medium circulation pump, a heat exchange medium cooler, and a heat exchange medium buffer tank, the heat exchange medium is buffered by the buffer tank and then pressurized by the heat exchange medium circulation pump. The circulation rate of the heat exchange medium is controlled by the heat exchange medium circulation pump rate. After being pressurized, the heat exchange medium is cooled by the heat exchange medium cooler and then sent back to the epoxidation reactor for heat exchange.

[0049] According to another preferred embodiment of the present invention, the epoxidation reaction heat exchange device consists of a heat exchange medium circulation pump and a heat exchange medium cooler. This preferred embodiment eliminates the heat exchange medium buffer tank, using the flow space of the heat exchange medium in the epoxidation reactor as a buffer zone.

[0050] According to another preferred embodiment of the present invention, the epoxidation reaction heat exchange device consists of a heat exchange medium circulation pump, the circulation rate of the heat exchange medium is controlled by the heat exchange medium circulation pump, part of the heat exchange medium is discharged from the reaction system, and a corresponding mass of cold heat exchange medium is replenished.

[0051] According to the present invention, preferably, the average flow velocity of the heat exchange medium in the epoxidation reaction heat exchange device is 0.5-2 m / s, more preferably 0.5-1.5 m / s. Controlling the average flow velocity of the heat exchange medium within the above range in the epoxidation reaction heat exchange device is beneficial for ensuring the temperature uniformity within the epoxidation reactor.

[0052] In this invention, in order to better control the reaction temperature of the epoxidation reaction, preferably, in the epoxidation reactor in use and / or the standby epoxidation reactor, the temperature difference between the outlet temperature of the heat exchange medium and the outlet temperature of the epoxidation reactor is not less than 2°C, preferably not less than 3°C, and more preferably 3-10°C.

[0053] Preferably, in the epoxidation reactor in use and / or the standby epoxidation reactor, the temperature difference between the inlet temperature of the heat exchange medium and the feed inlet of the epoxidation reactor is not higher than 30°C, more preferably not higher than 20°C, and more preferably 2-10°C.

[0054] In this invention, there is no particular limitation on the heat exchange medium; any conventional choice in the art can be used. For example, the heat exchange medium can be a liquid with a boiling point above 80°C at atmospheric pressure. Preferably, the heat exchange medium is water and / or heat transfer oil. Preferably, the heat transfer oil is selected from at least one of alkylbenzene-type heat transfer oil, alkylnaphthalene-type heat transfer oil, and alkylbiphenyl-type heat transfer oil.

[0055] According to the present invention, the epoxidation reaction can be carried out at any pressure equal to or higher than the saturated vapor pressure of the reactants, and it is advantageous to use a lower reaction pressure while ensuring that the reactants are in the liquid phase. Preferably, the epoxidation reaction conditions include: a reaction temperature of 20-100°C, preferably 25-65°C; a reaction pressure of 0.1-1.2 MPa, preferably 0.2-1 MPa; and an oxidant feed mass hourly space velocity of 0.01-1 h⁻¹. -1 Preferably, it is 0.03-0.4h. -1 The reaction pressure is gauge pressure.

[0056] Those skilled in the art will understand that, in the actual reaction process, the temperature of the epoxidation reactor is adjusted within the above-mentioned operating range as the reaction proceeds, and all of them meet the above-mentioned reaction conditions. The reaction temperature when the standby epoxidation reactor is switched into the system is the same as the initial reaction temperature of the epoxidation reactor in use.

[0057] In this invention, the range of solvents is relatively wide. Preferably, the solvent is selected from at least one of water, alcohols with 1-6 carbon atoms, ketones with 3-4 carbon atoms, ethers with 2-10 carbon atoms, nitriles with 2-4 carbon atoms, and carboxylic acid esters with 2-6 carbon atoms. More preferably, the solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, acetone, acetonitrile, and propionitrile. More preferably, methanol is selected from at least one of methanol.

[0058] In this invention, the oxidant can be selected from any conventional oxidant in the art, and can be chosen according to actual production needs. Preferably, the oxidant is hydrogen peroxide.

[0059] Preferably, the hydrogen peroxide is provided in the form of hydrogen peroxide solution, and preferably, the concentration of the hydrogen peroxide solution is 25-70 wt%.

[0060] In this invention, the selection of the catalyst is not particularly limited and can be any conventional choice in the art. Preferably, the catalyst is a titanium-silicon molecular sieve. This invention also does not have special requirements regarding the source of the catalyst; it can be commercially available or prepared using conventional methods in the art. For example, the titanium-silicon molecular sieve can be a molded catalyst prepared from TS-1 molecular sieve powder having a ZSM-5 topology.

[0061] According to the present invention, preferably, the feed molar ratio of the solvent to 3-chloropropene is 2-20:1, more preferably 2-15:1.

[0062] Preferably, the molar ratio of 3-chloropropene to the total feed amount of the oxidant is 1-15:1, more preferably 1-10:1.

[0063] According to the present invention, preferably, the reaction raw materials also include an alkaline additive. It is understood that when the reaction raw materials also include an alkaline additive, during the reaction feed switching in step (2), the feeding method of the solvent in the reaction raw materials remains unchanged, and 3-chloropropene, oxidant and alkaline additive are fed to the standby epoxidation reactor.

[0064] Preferably, the alkaline additive is selected from at least one of ammonia, alkaline ammonium salts, organic amines, and quaternary ammonium bases.

[0065] Preferably, the basic ammonium salt is selected from at least one of ammonium carbonate, ammonium bicarbonate and ammonium acetate.

[0066] Preferably, the organic amine is selected from at least one of methylamine, ethylamine, propylamine, dimethylamine, trimethylamine, diethylamine, triethylamine, butylamine, pentylamine, and hexylamine.

[0067] Preferably, the quaternary ammonium base is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0068] Preferably, the feed molar ratio of the alkaline additive to the oxidant is 0.001-0.05:1, more preferably 0.002-0.03:1.

[0069] In this invention, the alkaline additive can be provided by an aqueous solution of the alkaline additive, preferably with a concentration of 10-80 wt%, more preferably 10-50 wt%.

[0070] In this invention, preferably, the regeneration includes: introducing the solvent into the epoxidation reactor of the cutting system, operating at a temperature of 150℃-200℃ and an operating pressure of 1.3-5 MPaG. The flow rate of the solvent can be the same as or different from the above-mentioned reaction feed rate, and those skilled in the art can adjust it according to actual needs, as long as the above-mentioned operating temperature is maintained.

[0071] According to a specific embodiment of the present invention, such as Figure 1 As shown, the mixture of solvent a, oxidant b, 3-chloropropene c, and basic additive d is fed as feed e into the inlet of the in-use epoxidation reactor 1. After reaction in the in-use epoxidation reactor 1, the effluent g from the in-use epoxidation reactor is discharged from the reaction system.

[0072] When the conversion rate of the oxidant in the epoxidation reactor 1 drops below 95%, the outlet of the epoxidation reactor 1 is connected to the inlet of the standby epoxidation reactor 2. The solvent is kept flowing into the epoxidation reactor 1 through the solvent inlet a1 and then to the standby epoxidation reactor 2 through the outlet of a1. At the same time, hydrogen peroxide b, 3-chloropropene c, and alkaline additive d are fed into the inlet of the standby epoxidation reactor 2 and mixed with the outlet material g of the epoxidation reactor 1 as feed f into the standby epoxidation reactor 2. When the oxidant concentration at the outlet of the epoxidation reactor 2 drops below 30 ppm, feed a1 is stopped and feed a2 is started. The epoxidation reactor 1 is cut out of the system, the catalyst in it is regenerated, and after regeneration, it is reintroduced into the reaction system as a new standby epoxidation reactor.

[0073] The present invention will be described in detail below through embodiments.

[0074] The reaction raw materials used in the following examples were all commercially available.

[0075] Example 1

[0076] The epoxidation reaction system used is as follows: Figure 1 As shown, the system consists of an in-use epoxidation reactor 1 and a standby epoxidation reactor 2. The epoxidation reactors are filled with TS-1 type titanium-silicon molecular sieve catalyst. The in-use epoxidation reactor 1 and the standby epoxidation reactor 2 are respectively equipped with an in-use epoxidation heat exchange device 3 and a standby epoxidation heat exchange device 4. Each epoxidation reaction heat exchange device includes a heat exchange medium circulation pump. The average flow velocity of the heat exchange medium in the epoxidation reaction heat exchange device is 1 m / s. In each epoxidation reactor, the temperature difference between the outlet temperature of the heat exchange medium and the outlet temperature of the epoxidation reactor is 10℃, and the temperature difference between the inlet temperature of the heat exchange medium and the inlet temperature of the epoxidation reactor is 10℃.

[0077] Methanol, hydrogen peroxide, 3-chloropropene, and ammonia were mixed in a molar ratio of 12:1:2.5:0.03, with the ammonia concentration being 25 wt%. The mixture was then fed into the inlet of an in-use epoxidation reactor. After reaction in the reactor, the product was discharged from the reaction system through the outlet. The epoxidation reaction conditions included: a reaction temperature of 30-50°C, a reaction pressure of 0.5 MPa (gauge pressure), and a hydrogen peroxide feed mass hourly space velocity of 0.13 h⁻¹. -1 .

[0078] When the epoxidation reactor in use has been running for 1000 hours, the effluent from the reactor (containing product I, epichlorohydrin) is collected for chromatographic monitoring. At this time, the hydrogen peroxide conversion rate drops below 99%. The effluent outlet of the reactor in use is connected to the influent inlet of the standby epoxidation reactor. Methanol continues to be fed into the reaction system from the inlet of the reactor in use, flowing from the outlet to the standby reactor. Hydrogen peroxide, 3-chloropropene, and ammonia are fed into the inlet of the standby reactor, at which point product II, containing epichlorohydrin, is obtained at the outlet of the standby reactor. After 24 hours of material feeding into the standby reactor, the hydrogen peroxide content at the outlet of the reactor in use is found to be below 10 ppm. At this point, methanol feeding into the reactor in use is stopped, and methanol is fed into the inlet of the standby reactor. The reactor in use is now ready for regeneration. Methanol is introduced into the reactor in use at the flow rate described in the above reaction, and the catalyst is regenerated at 180°C and 3.0 MPaG.

[0079] After the catalyst in the epoxidation reactor is regenerated, the first reactor is reconnected to the reaction system as a new standby epoxidation reactor, and the original standby epoxidation reactor becomes the new epoxidation reactor in use.

[0080] The contents of each component in product I and product II containing epichlorohydrin were determined by chromatography, and the fluctuation of each component was calculated. The fluctuation rate of epichlorohydrin content was 0.5%, the fluctuation rate of oxidant content was 0.3%, and the fluctuation rate of solvent content was 0.8%.

[0081] Example 2

[0082] The epoxidation reaction system used is the same as in Example 1, such as... Figure 1 As shown.

[0083] Methanol, hydrogen peroxide, 3-chloropropene, and ammonia were mixed in a molar ratio of 10:1:2.7:0.03, with the ammonia concentration being 25 wt%. The mixture was then fed into the inlet of an in-use epoxidation reactor. After reaction in the reactor, the product was discharged from the reaction system through the outlet. The epoxidation reaction conditions included: a reaction temperature of 30-60°C, a reaction pressure of 0.5 MPa (gauge pressure), and a hydrogen peroxide feed mass hourly space velocity of 0.1 h⁻¹. -1 .

[0084] When the operating epoxidation reactor has been running for 1500 hours, the effluent from the operating epoxidation reactor (containing product I, epichlorohydrin) is collected for chromatographic monitoring. At this time, the hydrogen peroxide conversion rate drops below 99.0%. The effluent outlet of the operating epoxidation reactor is connected to the inlet of the standby epoxidation reactor (the reaction conditions in the standby epoxidation reactor are the same as those in the operating epoxidation reactor). Methanol continues to be fed into the reaction system from the inlet of the operating epoxidation reactor, flowing through the outlet to the standby epoxidation reactor. Hydrogen peroxide, 3-chloropropene, and ammonia are fed into the inlet of the standby epoxidation reactor. At this time, product II, containing epichlorohydrin, is obtained from the outlet of the standby epoxidation reactor.

[0085] After the material is fed into the standby epoxidation reactor for 72 hours, hydrogen peroxide is not detected at the outlet of the reactor in use. At this time, the feeding of methanol into the reactor in use is stopped, and methanol is fed into the inlet of the standby epoxidation reactor. At this time, the reactor in use is ready for regeneration, including: feeding methanol into the reactor in use at the flow rate of the above reaction, and regenerating the catalyst at 190°C and 4.0 MPaG.

[0086] After the catalyst in the epoxidation reactor is regenerated, the first reactor is reconnected to the reaction system as a new standby epoxidation reactor, and the original standby epoxidation reactor becomes the new epoxidation reactor in use.

[0087] The contents of each component in product I and product II containing epichlorohydrin were determined by chromatography, and the fluctuation of each component was calculated. The fluctuation rate of epichlorohydrin content was 0.4%, the fluctuation rate of oxidant content was 0.2%, and the fluctuation rate of solvent content was 0.5%.

[0088] Comparative Example 1

[0089] Following the method of Example 1, except that after running the epoxidation reaction unit for 1000 hours, the effluent from the in-use epoxidation reactor (product I containing epichlorohydrin) was collected for chromatographic monitoring. At this point, the conversion rate of hydrogen peroxide decreased to below 99%; then, methanol, hydrogen peroxide, 3-chloropropene, and ammonia were all switched from the inlet of the in-use epoxidation reaction unit to the inlet of the standby epoxidation reactor to continue the reaction. Product II containing epichlorohydrin was obtained from the outlet of the standby epoxidation reactor.

[0090] The contents of each component in product I and product II containing epichlorohydrin were determined by chromatography, and the fluctuation of each component was calculated. The fluctuation rate of epichlorohydrin content was 12.8%, the fluctuation rate of oxidant content was 15%, and the fluctuation rate of solvent content was 13.6%.

[0091] The comparison shows that the traditional reactor switching method results in a large fluctuation in the composition of the material before and after the switch. This fluctuation can affect the phase equilibrium results of the extraction and separation of the subsequent reaction products, and may even lead to short-term miscibility, which in turn affects the epichlorohydrin yield of the unit.

[0092] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A continuous production method for epichlorohydrin, characterized in that, The continuous production of epichlorohydrin is carried out in an epoxidation reaction system, which consists of an in-use epoxidation reactor and a standby epoxidation reactor. The method includes: (1) The reaction raw materials are fed into an in-use epoxidation reactor and contacted with the catalyst to carry out an epoxidation reaction to obtain product I containing epichlorohydrin; The reaction raw materials include 3-chloropropene, an oxidant, and a solvent; (2) When the conversion rate of the oxidant in the epoxidation reactor decreases to below 99%, the outlet of the epoxidation reactor in use will be connected to the inlet of the standby epoxidation reactor. Keeping the solvent feeding method in the reaction raw materials unchanged, the remaining reaction raw materials are switched to the standby epoxidation reactor; at this time, product II containing epichlorohydrin is obtained at the outlet of the standby epoxidation reactor; when the oxidant concentration at the outlet of the active epoxidation reactor drops to below 30 ppm, the reaction feed is switched, and all reaction raw materials are fed to the standby epoxidation reactor. Product I containing epichlorohydrin and Product II containing epichlorohydrin each independently include epichlorohydrin, solvent, oxidant, and impurity components; wherein, based on the epichlorohydrin content in Product I containing epichlorohydrin, the fluctuation rate of the epichlorohydrin content in Product II containing epichlorohydrin does not exceed 10%; Based on the solvent content in product I containing epichlorohydrin, the fluctuation rate of the solvent content in product II containing epichlorohydrin shall not exceed 10%; Based on the oxidant content in product I containing epichlorohydrin, the fluctuation rate of the oxidant content in product II containing epichlorohydrin shall not exceed 10%; (3) The system will be cut out of the epoxidation reactor, the catalyst in it will be regenerated, and then it will be put into the system as a new standby epoxidation reactor; (4) Repeat steps (1)-(3) to achieve continuous production of epichlorohydrin.

2. The method according to claim 1, wherein, Product I containing epichlorohydrin and Product II containing epichlorohydrin each independently include epichlorohydrin, solvent, oxidant and impurity components; wherein, based on the epichlorohydrin content in Product I containing epichlorohydrin, the fluctuation rate of the epichlorohydrin content in Product II containing epichlorohydrin does not exceed 5%.

3. The method according to claim 1, wherein, When the conversion rate of the oxidant in the epoxidation reactor decreases to 95-99%, the outlet of the epoxidation reactor in use will be connected to the inlet of the standby epoxidation reactor; while keeping the feeding method of the solvent in the reaction raw materials unchanged, the remaining reaction raw materials will be fed to the standby epoxidation reactor.

4. The method according to claim 1, wherein, The in-use epoxidation reactor and the standby epoxidation reactor are each independently equipped with an epoxidation reaction heat exchange device, which includes a heat exchange medium for controlling the temperature of the epoxidation reaction.

5. The method according to claim 4, wherein, The average flow velocity of the heat exchange medium in the epoxidation reaction heat exchange device is 0.5-2 m / s.

6. The method according to claim 5, wherein, The average flow velocity of the heat exchange medium in the epoxidation reaction heat exchange device is 0.5-1.5 m / s.

7. The method according to claim 4, wherein, In the epoxidation reactor in use and / or in the standby epoxidation reactor, the temperature difference between the outlet temperature of the heat exchange medium and the outlet temperature of the epoxidation reactor is not less than 2°C. And / or, in the epoxidation reactor and / or the standby epoxidation reactor, the temperature difference between the inlet temperature of the heat exchange medium and the feed inlet of the epoxidation reactor is not higher than 30°C.

8. The method according to claim 7, wherein, In the epoxidation reactor in use and / or in the standby epoxidation reactor, the temperature difference between the outlet temperature of the heat exchange medium and the outlet temperature of the epoxidation reactor is not less than 3°C. And / or, in the epoxidation reactor and / or the standby epoxidation reactor, the temperature difference between the inlet temperature of the heat exchange medium and the feed inlet of the epoxidation reactor is not higher than 20°C.

9. The method according to claim 8, wherein, In the epoxidation reactor in use and / or in the standby epoxidation reactor, the temperature difference between the outlet temperature of the heat exchange medium and the outlet temperature of the epoxidation reactor is not less than 3-10°C. And / or, in the epoxidation reactor and / or the standby epoxidation reactor, the temperature difference between the inlet temperature of the heat exchange medium and the feed inlet of the epoxidation reactor is 2-10°C.

10. The method according to claim 1, wherein, The epoxidation reaction conditions are as follows: reaction temperature 20-100℃; reaction pressure 0.1-1.2MPa; oxidant feed mass hourly space velocity 0.01-1h. -1 .

11. The method according to claim 10, wherein, The epoxidation reaction conditions are as follows: reaction temperature 25-65℃; reaction pressure 0.2-1MPa; oxidant feed mass hourly space velocity 0.03-0.4h. -1 .

12. The method according to claim 1, wherein, The solvent is selected from at least one of water, alcohols having 1-6 carbon atoms, ketones having 3-4 carbon atoms, ethers having 2-10 carbon atoms, nitriles having 2-4 carbon atoms, and carboxylic acid esters having 2-6 carbon atoms. And / or, the oxidant is hydrogen peroxide; And / or, the catalyst is a titanium-silicon molecular sieve catalyst.

13. The method according to claim 12, wherein, The solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, acetone, acetonitrile, and propionitrile.

14. The method according to claim 13, wherein, The solvent is methanol.

15. The method according to claim 1, wherein, The feed molar ratio of the solvent to 3-chloropropene is 2-20:1; And / or, the molar ratio of 3-chloropropene to the total feed amount of the oxidant is 1-15:

1.

16. The method according to claim 15, wherein, The feed molar ratio of the solvent to 3-chloropropene is 2-15:1; And / or, the molar ratio of the total feed amount of 3-chloropropene to the oxidant is 1-10:

1.

17. The method according to claim 1, wherein, The reaction raw materials also contain alkaline additives.

18. The method according to claim 17, wherein, The alkaline additive is selected from at least one of ammonia, alkaline ammonium salts, organic amines, and quaternary ammonium bases.

19. The method according to claim 18, wherein, The basic ammonium salt is selected from at least one of ammonium carbonate, ammonium bicarbonate and ammonium acetate; And / or, the organic amine is selected from at least one of methylamine, ethylamine, propylamine, dimethylamine, trimethylamine, diethylamine, triethylamine, butylamine, pentylamine, and hexylamine; And / or, the quaternary ammonium base is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

20. The method of claim 17, wherein, The feed molar ratio of the alkaline additive to the oxidant is 0.001-0.05:

1.

21. The method according to claim 20, wherein, The feed molar ratio of the alkaline additive to the oxidant is 0.002-0.03:

1.

22. The method according to any one of claims 1-21, wherein, The catalyst regeneration step includes: introducing the solvent into the epoxidation reactor of the cut-out system at an operating temperature of 150℃-200℃ and an operating pressure of 1.3-5MPaG.

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