Regeneration method of epoxidation reactor

Abstract

The present invention relates in a first aspect to a process for regeneration of an epoxidation reactor that has been used in a process for the preparation of oxidized olefins, the process comprising: (i) providing an organic solvent, an olefin, an epoxidation agent and water to the reactor comprising a heterogeneous epoxidation catalyst in an epoxidation zone, to form a reaction mixture comprising an olefin, hydrogen peroxide, water, and an organic solvent; (ii) subjecting the mixture of (i) in the epoxidation zone of the reactor to epoxidation conditions in the presence of the catalyst, thereby obtaining a mixture comprising water, the organic solvent and an olefin oxide; (iii) removing the mixture comprising water, the organic solvent and the olefin oxide as obtained in (ii) from the reactor; whereby the precipitate is deposited in the reactor; the regeneration method comprises the following steps: (a) stopping supplying the organic solvent, the olefin, the epoxidation agent and the water to the reactor; (b) introducing a liquid aqueous system into the reactor wherein the liquid aqueous system comprises a chelating agent comprising a bisphosphonic acid of formula (I): (OH) 2 (O =) P-CR1R2-P (= O) (OH) 2 (I) wherein R1 and R2 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group and a C1 to C5 alkyl group wherein R1 is preferably a hydroxyl group and R2 is preferably a methyl group (1-hydroxyethylidene-1, 3, 4-triazole-1-yl), 1, 1-diphosphonic acid, HEDP). A second aspect of the invention relates to a combined preparation process of an olefin oxide comprising a preparation stage and a regeneration stage of an epoxidation reactor, the preparation stage comprising steps (i), (ii) and (iii), whereby precipitates are deposited in the reactor; the regeneration stage comprises steps (a) and (b).

Description

[0001] The present invention relates, in a first aspect, to a method for regenerating an epoxidation reactor that has been used in a process for the preparation of an epoxidized olefin, the preparation process comprising: (i) supplying an organic solvent, an olefin, an epoxidizing agent, and water to the reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone so as to form a reaction mixture comprising an olefin, hydrogen peroxide, water, and an organic solvent; (ii) subjecting the mixture of (i) in the epoxidation zone of the reactor to epoxidation conditions in the presence of the catalyst, thereby obtaining a mixture comprising water, the organic solvent, and an epoxidized olefin; (iii) removing from the reactor the mixture comprising water, the organic solvent, and an epoxidized olefin obtained in (ii); whereby a precipitate is deposited in the reactor; the regeneration method comprising: (a) ceasing to supply the organic solvent, the olefin, the epoxidizing agent, and water to the reactor; and (b) introducing a liquid aqueous system into the reactor, wherein the liquid aqueous system comprises a chelating agent that comprises at least three oxygen atoms and optionally one or more nitrogen atoms in its structure, and when forming a chelate with a metal cation, the chelating agent is capable of forming at least three coordination bonds with the metal cation via said at least three oxygen atoms and optionally via one or more of its nitrogen atoms. The second aspect of the present invention relates to a combined process for the preparation of an epoxidized olefin, the combined process comprising a preparation stage and a regeneration stage of an epoxidation reactor, the preparation stage comprising steps (i), (ii), and (iii), whereby a precipitate is deposited in the reactor; the regeneration stage comprising steps (a) and (b).

[0002] Propylene oxide (PO) is one of the most important chemical intermediates in industry. It represents a starting compound for a wide range of products such as foams, solvents, or de-icing agents. Conventionally, PO has been produced via the chlorohydrin process, which is still in use, as well as the ethylene oxide process. The development of catalysts based on zeolite materials having a framework structure comprising Si, O, and Ti (such as titanium silicalite-1) together with the improved availability of large amounts of hydrogen peroxide has enabled the large-scale implementation of the HPPO technology without by-products. This new process enables the production of PO in excellent yields and selectivities.

[0003] The HPPO process produces propylene oxide from propylene and hydrogen peroxide in an aqueous organic solvent using a zeolite material having a framework structure comprising Si, O, and Ti as a catalyst. In one case, methanol is used as the solvent, usually in combination with a zeolite material having an MFI framework type and a framework structure comprising Si, O, and Ti (titanium silicalite-1, TS-1) as the catalyst. In another case, acetonitrile is used as the solvent, usually in combination with a zeolite material having an MWW framework type and a framework structure comprising Si, O, and Ti (TiMWW) as the catalyst.

[0004] In the production of propylene oxide according to the HPPO process, it is known that precipitates deposit in certain critical areas of the process equipment over time. Specifically, the deposition of these precipitates at the inlet of the epoxidation reactor hinders the flow of the feed into these reactors. This results in an increase in the pressure drop across the system and an uneven flow distribution. The higher pressure drop across the reactor can lead to a reduction in the throughput (production) of the process, and the uneven flow distribution can lead to a loss of selectivity to the desired product, as some tubes will experience high residence times / low conversions while other tubes will experience low residence times / high conversions compared to the process conditions that yield optimal performance.

[0005] It is hypothesized that the precipitates contain deposited salts that are derived from a combination of components intentionally added to the process to enhance reactor performance, stabilizers present in the hydrogen peroxide feed, corrosion products, and other metal sources. Once deposited, the salts are difficult to remove from the process equipment. Spraying or purging the deposits requires access and entry to the areas to be cleaned, which results in an extended downtime of the reactor and a risk of catalyst damage. This technique also cannot remove the precipitates / salts deposited on, within, or around the catalyst particles themselves. In principle, chemical methods such as solvation / dissolution can be used without the need for access and entry or physical damage to the catalyst. However, these precipitates / salts are relatively insoluble. For example, WO 2016 / 128538 A1 describes a method for regenerating a catalyst comprising a titanium-containing zeolite as the catalytically active material, wherein the catalyst is washed with a liquid aqueous system consisting mainly of water. However, water is generally ineffective as a solvent for removing the precipitates / deposited salts. Aggressive cleaning agents can damage the catalyst or corrode the process equipment and are therefore undesirable. For example, WO 2015 / 010994 A1 discloses a regeneration method wherein the catalyst is washed with a liquid aqueous system. The liquid aqueous system employed consists mainly of water, and the addition of acids should be avoided, i.e., the liquid aqueous system must have an alkaline pH value. However, this process scheme also originally fails to dissolve the highly insoluble complex salts in a satisfactory manner.

[0006] Accordingly, a basic object of the present invention is to provide an improved method for dissolving highly insoluble complex salts without damaging the catalyst or the process equipment.

[0007] First aspect - regeneration method

[0008] In a first aspect, this object is solved by a method for regenerating an epoxidation reactor that has been used in a process for the preparation of an epoxidized olefin, the method comprising:

[0009] (i) Provide an organic solvent, an olefin, an epoxidizing agent, and water to a reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone to form a reaction mixture containing the olefin, hydrogen peroxide, water, and the organic solvent;

[0010] (ii) Subject the mixture of (i) in the epoxidation zone of the reactor to epoxidation conditions in the presence of the catalyst to obtain a mixture containing water, the organic solvent, and an epoxidized olefin;

[0011] (iii) Remove from the reactor the mixture containing water, the organic solvent, and the epoxidized olefin obtained in (ii);

[0012] Thereby, a precipitate is deposited in the reactor;

[0013] The regeneration method comprises:

[0014] (a) Stop providing the organic solvent, the olefin, the epoxidizing agent, and water to the reactor;

[0015] (b) Introduce a liquid aqueous system into the reactor, wherein the liquid aqueous system contains a chelating agent that contains at least three oxygen atoms and optionally one or more nitrogen atoms in its structure, and when forming a chelate with a metal cation, the chelating agent is capable of forming at least three coordination bonds with the metal cation via the at least three oxygen atoms and optionally via one or more of its nitrogen atoms.

[0016] In some embodiments, the log K value of the chelating agent relative to the trivalent iron cation (Fe 3+ ) is at least 10, preferably in the range of 11 to 30, more preferably in the range of 15 to 30, where these values are based on measurements at a temperature in the range of 20 °C to 25 °C in a constant temperature room at a constant ionic strength I of 0.1 mol l -1 established by a suitable salt of an alkali metal cation such as KNO3.

[0017] In some embodiments, when forming a chelate with a metal cation, a chelating agent that contains at least three oxygen atoms and optionally one or more nitrogen atoms in its structure can form or forms, preferably forms 3 to 8 coordination bonds with the metal cation via the one or more nitrogen atoms and / or one or more oxygen atoms. The expression "can form or forms, preferably forms 3 to 8 coordination bonds with a metal cation via the one or more nitrogen atoms and / or one or more oxygen atoms" means that the chelating agent forms or can form at least 3 coordination bonds with one (1) metal cation. In cases where the chelating agent can form more than 3 coordination bonds, these more than three coordination bonds may point to the same metal cation as the initial three coordination bonds, but can also point to one or more additional metal cations. For example, if the chelating agent is EDTA (or its complete salt or partial salt), the chelating agent can form a total of six coordination bonds - three of these six coordination bonds must point or can point to a single metal cation. Contrary to the preferred chelating agents listed below, pyrophosphates, such as in the form of acid sodium pyrophosphate (SAPP), although having more coordination sites, can only form 2 coordination bonds with one metal cation due to their structure.

[0018] In some embodiments, the chelating agent is selected from the group consisting of:

[0019] - Ethylenediaminetetraacetic acid (EDTA),

[0020] - Diethylenetriaminepentaacetic acid (DTPA)

[0021] - N-(Hydroxyethyl)ethylenediaminetriacetic acid (HEDTA),

[0022] - N-(1-Carboxyethyl)-iminodiacetic acid (MGDA),

[0023] - Nitrilotriacetic acid (NTA),

[0024] - L-Glutamic acid-N,N-diacetic acid (GLDA),

[0025] - Aminotris(methylenephosphonic acid) (AMTP),

[0026] - Ethanoldiglycine (EDG),

[0027] - Diphosphonic acid of formula (I)

[0028] (OH)2(O=)P-CR 1 R 2 - P(=O)(OH)2 (I),

[0029] where R 1 and R 2independently selected from the group consisting of a hydrogen atom, a hydroxyl group, and a C1 to C5 alkyl group,

[0030] and mixtures of two or more of these chelating agents.

[0031] In some embodiments, the chelating agent is selected from the group consisting of: EDTA, DTPA, HEDTA, MGDA, NTA, AMTP, the diphosphonic acids of formula (I) as described above, and mixtures of two or more of these chelating agents.

[0032] In some preferred embodiments, the chelating agent comprises, preferably a diphosphonic acid of formula (I), wherein R 1 is preferably a hydroxyl group and R 2 is preferably a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP).

[0033] The chelating agent is used in its protonated form or in at least a partially deprotonated form, for example in the form of a partial salt or a complete salt, i.e., one of its corresponding anions has a suitable cation to compensate for the charge of the anion. In some preferred embodiments, the chelating agent is used in its fully protonated form.

[0034] Compared with pure water and a washing solution containing sodium acid pyrophosphate (SAPP), the use of a liquid aqueous system containing a chelating agent as defined above, especially a diphosphonic acid of formula (I), significantly improves the dissolution of the precipitate. It can also be shown that the liquid aqueous system containing a chelating agent as defined above, especially a diphosphonic acid of formula (I), does not damage the catalyst or weaken the performance of the catalyst in any way. In addition, it is shown that the process vessel is not damaged by the liquid aqueous system containing a chelating agent as defined above, especially a diphosphonic acid of formula (I).

[0035] In some preferred embodiments of the method for regenerating an epoxidation system, the liquid aqueous system used in (b) contains a chelating agent in the range of 0.01 wt% to 50 wt%, preferably in the range of 0.02 wt% to 25 wt%, more preferably in the range of 0.05 wt% to 10 wt%, preferably a diphosphonic acid, more preferably HEDP, more preferably a chelating agent in the range of 0.1 wt% to 5 wt%, preferably a diphosphonic acid, more preferably HEDP, each based on 100 wt% of the total weight of the liquid aqueous system.

[0036] In some preferred embodiments of the method for regenerating an epoxidation system, step (b) comprises:

[0037] (b.1) introducing a first portion of the liquid aqueous system containing the chelating agent into the reactor;

[0038] (b.2) Remove at least a portion of the first part of the liquid aqueous system from the reactor.

[0039] In some preferred embodiments of the method for regenerating an epoxidation system, step (b) comprises:

[0040] (b.1) Introduce a first part of the liquid aqueous system comprising a chelating agent into the reactor;

[0041] (b.2) Remove at least a portion of the first part of the liquid aqueous system from the reactor;

[0042] (b.3) Optionally introduce another part of the liquid aqueous system comprising a chelating agent into the reactor;

[0043] (b.4) Optionally remove at least a portion of the other part of the liquid aqueous system from the reactor;

[0044] Wherein steps (b.3) and (b.4) are optionally repeated from 1 to 10 times.

[0045] In some preferred embodiments of the method for regenerating an epoxidation system, the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out with a gaseous stream passing through the liquid aqueous system, wherein the gaseous stream preferably contains at least 90% by volume, more preferably at least 95% by volume, more preferably at least 98% by volume of an inert gas based on the total volume of the gaseous stream. "Inert gas" is preferably selected from the group consisting of helium, neon, argon, krypton, xenon, nitrogen, and mixtures of two or more of these inert gases, and more preferably the inert gas contains at least 90% by volume, more preferably at least 95% by volume, more preferably at least 98% by volume of nitrogen.

[0046] In some preferred embodiments of the method for regenerating an epoxidation system, the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a temperature in the reactor in the range of 0.1 °C to the boiling point of the liquid aqueous system, preferably in the range of 0.5 °C to 90 °C, more preferably in the range of 5 °C to 50 °C, more preferably in the range of 10 °C to 40 °C.

[0047] In some preferred embodiments of the method for regenerating an epoxidation system, the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a pressure in the reactor in the range of 0.05 MPa to 5.0 MPa, preferably in the range of 0.08 MPa to 1.0 MPa, more preferably in the range of 0.1 MPa to 0.15 MPa.

[0048] In some preferred embodiments of the method for regenerating an epoxidation system, the reactor comprises one or more vertically arranged tubes, each tube having a specific length (height), having a bottom end and a top end, wherein the catalyst is present between positions H1 and H2 in the tube, where H2 is higher in the tube than H1, and the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that the liquid level in the tube is at least at the height of H2, preferably at a height within the range between H1 and H2, more preferably at a height within the range of 80% to 5% below H2, more preferably at a height within the range of 70% to 10% below H2, more preferably at a height within the range of 60% to 20% below H2, more preferably at a height within the range of 50% to 25% below H2, more preferably at a height within the range of 40% to 30% below H2, each relative to the distance between H1 and H2 being 100%. In other words, in these preferred embodiments, the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that at least all of the catalyst is immersed in the liquid aqueous system, preferably all of the catalyst is immersed in the liquid aqueous system, more preferably 20% to 95% of the catalyst is immersed in the liquid aqueous system, more preferably 30% to 90% of the catalyst is immersed in the liquid aqueous system, more preferably 40% to 80% of the catalyst is immersed in the liquid aqueous system, more preferably 50% to 75% of the catalyst is immersed in the liquid aqueous system.

[0049] The term "vertical" includes any substantially vertical arrangement, i.e., vertical also includes an arrangement in which the tube is placed at an angle of ±45° relative to the vertical axis. Preferably, the tubes are arranged in a tube sheet, which is present in the lower part of the reactor. The catalyst, i.e., the catalyst packing, is preferably held in place in the tube by a catalyst support, which is present in the region between the bottom end of each tube in the tube and H1. The catalyst support is permeable to gaseous and liquid components, such as the liquid aqueous system, but holds the catalyst in place in the tube. In some embodiments, the position of the tube sheet is higher than the position of the catalyst support, each position being relative to the height of each tube. In some embodiments, there is also an inert material located in the tube between the catalyst support and H1. The inert material is permeable to gaseous and liquid components, such as the liquid aqueous system.

[0050] In some preferred embodiments of the method for regenerating an epoxidation system, the amount of precipitate dissolved in the liquid aqueous system that is at least partially removed from the reactor is determined after step (b.2). More preferably, the amount of precipitate dissolved in the liquid aqueous system determined after step (b.2) is further set to be related to the amount of catalyst. If the percentage value of the dissolved precipitate of each catalyst ≤ 1%, more preferably ≤ 0.9%, more preferably ≤ 0.8%, then in some preferred embodiments, after step (b.2), no further step (b.3) and step (b.4) are carried out. If the percentage value of the dissolved precipitate of each catalyst is higher than 1%, then in some preferred embodiments, step (b.3) and step (b.4) are carried out and optionally repeated 1 to 10 times, wherein preferably after each step (b.4), the amount of precipitate dissolved in the liquid aqueous system that is at least partially removed from the reactor is determined, and steps (b.3) and (b.4) are repeated until the percentage value of the dissolved precipitate of each catalyst ≤ 1%, more preferably ≤ 0.9%, more preferably ≤ 0.8%.

[0051] In some embodiments, in order to determine the amount of precipitate dissolved in the liquid aqueous system, the concentrations of the various components in the liquid aqueous system before use are initially determined as a baseline (initial concentration, c0), and then the amount of precipitate dissolved in the liquid aqueous system after removal from the reactor (concentration c x ) is determined, and the amount of precipitate dissolved in the liquid aqueous system is determined by forming the difference between c x and c0. Preferably, in order to determine the concentrations of the various components in the liquid aqueous system, the metals, preferably one or more metals selected from the group consisting of aluminum (Al), silicon (Si), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), and zinc (Zn), and also the concentration of phosphorus (P) are studied.

[0052] The indication of "metal" or the naming of a specific metal such as aluminum or iron means that these metals do not exist in elemental form, i.e., their oxidation state is zero, but exist in the form of metal cations, where the positive charge is compensated by one or more anions. This also applies to other chemical elements, such as P, which usually exists as an oxygen anion, for example, phosphate (PO4 3- ) or hydrogen phosphate (HPO4 2- ) or pyrophosphate (H2P2O7 2- ).

[0053] Means for determining the concentration of metals (cations) as well as the concentration of other chemical elements and their cations or anions are well known to those skilled in the art, such as evaporating the sample to dryness and then determining the amount of the remaining solid by weighing. In some preferred embodiments, inductively coupled plasma-optical emission spectrometry (ICP-OES) is used for analysis, i.e., for determining the concentration, preferably directly in the liquid sample. If ICP-OES is used, for each metal, a suitable anion is selected, such as preferably a suitable oxygen- and / or phosphorus-based anion, and the weight of the precipitated salt is calculated based on the amounts of metal, oxygen, and / or phosphorus. Exemplary salts for analysis and calculation are Al2(H2P2O7)3, SiO2, Mg3(PO4)2, K2HPO4, Ca3(PO4)2, TiO2, Cr2O3, Fe2(H2P2O7)3, NiO; and in some embodiments, sodium (Na) is calculated directly based on the Na concentration.

[0054] Second aspect - combination method

[0055] In a second aspect, the present invention relates to a combined preparation method of an epoxidized olefin, the combined preparation method comprising a preparation stage and a regeneration stage of an epoxidation reactor,

[0056] The preparation stage comprises:

[0057] (i) Supplying an organic solvent, an olefin, an epoxidizing agent, and water to a reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone so as to form a reaction mixture containing an olefin, hydrogen peroxide, water, and an organic solvent;

[0058] (ii) Subjecting the mixture formed in (i) in the epoxidation reactor to epoxidation conditions in the presence of the catalyst, thereby obtaining a mixture containing water, an organic solvent, and an epoxidized olefin;

[0059] (iii) Removing from the reactor the mixture containing water, an organic solvent, and an epoxidized olefin obtained in (ii);

[0060] Thereby, a precipitate is deposited in the reactor;

[0061] The regeneration stage comprises:

[0062] (a) Stopping introducing the mixture of (i) into the reactor;

[0063] (b) A liquid aqueous system is introduced into the reactor, wherein the liquid aqueous system contains a chelating agent which contains at least three oxygen atoms and optionally one or more nitrogen atoms in its structure, and when forming a chelate with a metal cation, the chelating agent is capable of forming at least three coordination bonds with the metal cation via said at least three oxygen atoms and optionally via one or more of its nitrogen atoms.

[0064] In some preferred embodiments of the combined preparation process of the epoxidized olefin, the combined preparation process includes a preparation stage and a regeneration stage of the epoxidation reactor, and the log K value of the chelating agent relative to the ferric cation (Fe 3+ ) is at least 10, preferably in the range of 11 to 30, more preferably in the range of 15 to 30, where these values are based on measurements at a temperature in the range of 20 °C to 25 °C in a thermostat at a constant ionic strength I established by a suitable salt of an alkali metal cation such as KNO3 at 0.1 mol l -1 .

[0065] In some preferred embodiments of the combined preparation process of the epoxidized olefin, the combined preparation process includes a preparation stage and a regeneration stage of the epoxidation reactor. When forming a chelate with a metal cation, a chelating agent containing at least three oxygen atoms and optionally one or more nitrogen atoms in its structure can form or forms, preferably forms 3 to 8 coordination bonds with the metal cation via said one or more nitrogen atoms and / or one or more oxygen atoms. The expression "can form or forms, preferably forms 3 to 8 coordination bonds with the metal cation via said one or more nitrogen atoms and / or one or more oxygen atoms" means that the chelating agent forms or can form at least 3 coordination bonds with one (1) metal cation. In the case where the chelating agent can form more than 3 coordination bonds, these more than three coordination bonds may point to the same metal cation as the initial three coordination bonds, but can also point to one or more additional metal cations. For example, if the chelating agent is EDTA (or its (partial) salt), then the chelating agent can form a total of six coordination bonds - three of these six coordination bonds must point or can point to a single metal cation.

[0066] In some preferred embodiments of the combined preparation process of the epoxidized olefin, the combined preparation process includes a preparation stage and a regeneration stage of the epoxidation reactor, and the chelating agent is selected from the group consisting of:

[0067] - Ethylenediaminetetraacetic acid (EDTA),

[0068] - Diethylenetriaminepentaacetic acid (DTPA)

[0069] - N-(Hydroxyethyl)ethylenediaminetriacetic acid (HEDTA),

[0070] -N-(1-carboxyethyl)-iminodiacetic acid (MGDA),

[0071] -nitrilotriacetic acid (NTA),

[0072] -L-glutamic acid-N,N-diacetic acid (GLDA),

[0073] -aminotris(methylenephosphonic acid) (AMTP),

[0074] -ethanoldiglycine (EDG),

[0075] -diphosphonic acid of formula (I)

[0076] (OH)2(O=)P-CR 1 R 2 -P(=O)(OH)2 (I),

[0077] wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, and C1 to C5 alkyl groups,

[0078] and mixtures of two or more of these chelating agents.

[0079] In some preferred embodiments of the combined preparation process of the epoxidized olefin, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor, and the chelating agent is selected from the group consisting of: EDTA, DTPA, HEDTA, MGDA, NTA, AMTP, the diphosphonic acid of formula (I) as described above, and mixtures of two or more of these chelating agents.

[0080] In some preferred embodiments of the combined preparation process of the epoxidized olefin, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor, and the chelating agent is the diphosphonic acid of formula (I), wherein R 1 is preferably a hydroxyl group and R 2 is preferably a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP).

[0081] The chelating agent is used in its protonated form or in at least a partially deprotonated form, for example in the form of a salt, i.e., one of its corresponding anions has a suitable cation to compensate for the charge of the anion. In some preferred embodiments, the chelating agent is used in its fully protonated form.

[0082] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor. The liquid aqueous system used in (b) contains a chelating agent in the range of 0.01% to 50% by weight, preferably in the range of 0.02% to 25% by weight, more preferably in the range of 0.05% to 10% by weight, preferably a diphosphonic acid of formula (I), more preferably HEDP, more preferably a chelating agent in the range of 0.1% to 5% by weight, preferably a diphosphonic acid, more preferably HEDP, each based on 100% by weight of the total weight of the liquid aqueous system.

[0083] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor:

[0084] (b.1) Introduce a first portion of the liquid aqueous system containing the chelating agent into the reactor;

[0085] (b.2) At least partially remove the first portion of the liquid aqueous system from the reactor.

[0086] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor, and step (b) includes:

[0087] (b.1) Introduce a first portion of the liquid aqueous system containing the chelating agent into the reactor;

[0088] (b.2) At least partially remove the first portion of the liquid aqueous system from the reactor;

[0089] (b.3) Optionally introduce another portion of the liquid aqueous system containing the chelating agent into the reactor;

[0090] (b.4) Optionally at least partially remove another portion of the liquid aqueous system from the reactor; wherein steps (b.3) and (b.4) are optionally repeated 1 to 10 times.

[0091] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor. The introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out by a gaseous stream passing through the liquid aqueous system, wherein the gaseous stream preferably contains at least 90% by volume, more preferably at least 95% by volume, and even more preferably at least 98% by volume of an inert gas based on the total volume of the gaseous stream. The "inert gas" is preferably selected from the group consisting of helium, neon, argon, krypton, xenon, nitrogen, and mixtures of two or more of these inert gases. More preferably, the inert gas contains at least 90% by volume, more preferably at least 95% by volume, and even more preferably at least 98% by volume of nitrogen.

[0092] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor. The introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a temperature in the reactor within the range of 0.1 °C to the boiling point of the liquid aqueous system, preferably within the range of 0.5 °C to 90 °C, more preferably within the range of 5 °C to 50 °C, and even more preferably within the range of 10 °C to 40 °C.

[0093] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of an epoxidation reactor. The introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a pressure in the reactor within the range of 0.05 MPa to 5.0 MPa, preferably within the range of 0.08 MPa to 1.0 MPa, and more preferably within the range of 0.1 MPa to 0.15 MPa.

[0094] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of the epoxidation reactor. The reactor includes one or more tubes arranged vertically, each tube having a specific length (height), with a bottom end and a top end, wherein the catalyst is present between positions H1 and H2 in the tube, where H2 is higher than H1 in the tube, and the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that the liquid level in the tube is at least at the height of H2, preferably at a height within the range between H1 and H2, more preferably at a height within the range of 80% to 5% below H2, more preferably at a height within the range of 70% to 10% below H2, more preferably at a height within the range of 60% to 20% below H2, more preferably at a height within the range of 50% to 25% below H2, more preferably at a height within the range of 40% to 30% below H2, each relative to the distance between H1 and H2 being 100%. In other words, in these preferred embodiments, the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that at least all of the catalyst is immersed in the liquid aqueous system, preferably all of the catalyst is immersed in the liquid aqueous system, more preferably 20% to 95% of the catalyst is immersed in the liquid aqueous system, more preferably 30% to 90% of the catalyst is immersed in the liquid aqueous system, more preferably 40% to 80% of the catalyst is immersed in the liquid aqueous system, more preferably 50% to 75% of the catalyst is immersed in the liquid aqueous system.

[0095] The term "vertical" includes any substantially vertical arrangement, i.e., vertical also includes an arrangement in which the tube is placed at an angle of ±45° relative to the vertical axis. Preferably, the tubes are arranged in a tube sheet, and the tube sheet is present in the lower part of the reactor. The catalyst, i.e., the catalyst packing, is preferably held in place within the tube by a catalyst support, which is present in the region between the bottom end of each tube in the tube and H1. The catalyst support is permeable to gaseous and liquid components, such as the liquid aqueous system, but holds the catalyst in place within the tube. In some embodiments, the position of the tube sheet is higher than the position of the catalyst support, each position being relative to the height of each tube.

[0096] In some preferred embodiments of the combined preparation process of the alkylene oxide, the combined preparation process includes a preparation stage and a regeneration stage of the epoxidation reactor. After step (b.2), the amount of precipitate dissolved in the liquid aqueous system that is at least partially removed from the reactor is determined. More preferably, the amount of precipitate dissolved in the liquid aqueous system determined after step (b.2) is further set to be related to the amount of the catalyst. If the percentage value of the dissolved precipitate of each catalyst ≤ 1%, more preferably ≤ 0.9%, more preferably ≤ 0.8%, then in some preferred embodiments, after step (b.2), no additional step (b.3) and step (b.4) are carried out. If the percentage value of the dissolved precipitate of each catalyst is higher than 1%, then in some preferred embodiments, step (b.3) and step (b.4) are carried out and optionally repeated 1 to 10 times, where preferably after each step (b.4), the amount of precipitate dissolved in the liquid aqueous system that is at least partially removed from the reactor is determined, and steps (b.3) and (b.4) are repeated until the percentage value of the dissolved precipitate of each catalyst ≤ 1%, more preferably ≤ 0.9%, more preferably ≤ 0.8%. Regarding the determination of the amount of precipitate dissolved in the liquid aqueous system, the same applies as disclosed above in the first part.

[0097] Epoxidizing agent

[0098] In some preferred embodiments of the regeneration process of the epoxidation reactor according to the first aspect or the combined preparation process of the alkylene oxide according to the second aspect, the epoxidizing agent is hydrogen peroxide, wherein hydrogen peroxide is preferably provided in the form of an aqueous hydrogen peroxide solution, and the aqueous hydrogen peroxide solution preferably has a total organic carbon content (TOC) of hydrogen peroxide contained per kg of the aqueous hydrogen peroxide solution in the range of 100 mg to 800 mg, preferably in the range of 120 mg to 750 mg per kg of the aqueous hydrogen peroxide solution, more preferably in the range of 150 mg to 700 mg per kg of the aqueous hydrogen peroxide solution, as determined according to DIN EN 1484;

[0099] and / or

[0100] wherein hydrogen peroxide has a pH in the range of 0 to 3.0, preferably in the range of 0.1 to 2.5, more preferably in the range of 0.5 to 2.3, as determined with a pH-sensitive glass electrode according to AM7160; and / or wherein, relative to the total weight of the aqueous hydrogen peroxide solution, hydrogen peroxide contains 20% to 85% by weight, preferably 30% to 75% by weight, more preferably 40% to 70% by weight of hydrogen peroxide;

[0101] and / or

[0102] Wherein the hydrogen peroxide is obtained from or obtainable from the anthraquinone process.

[0103] Organic solvent

[0104] In some preferred embodiments of the method for regenerating an epoxidation reactor according to the first aspect or the combined preparation method of an oxidized olefin according to the second aspect, the organic solvent is an organic epoxidation solvent, preferably the organic solvent is selected from the group consisting of alcohols, acetonitrile, propionitrile, and mixtures of two or more thereof; more preferably selected from the group consisting of alcohols, acetonitrile, and mixtures of alcohols and acetonitrile; more preferably the organic solvent contains at least one alcohol, wherein the alcohol is preferably a C1-C5 monohydric alcohol or a mixture of two or more C1-C5 alcohols, and more preferably the alcohol contains at least methanol.

[0105] Olefin

[0106] In some preferred embodiments of the method for regenerating an epoxidation reactor according to the first aspect or the combined preparation method of an oxidized olefin according to the second aspect, the olefin is a C2-C10 chain olefin, preferably a C2-C5 chain olefin, more preferably a C2-C4 chain olefin, more preferably ethylene (C2 olefin) or propylene (C3 chain olefin), and more preferably propylene (C3 chain olefin).

[0107] Additive / buffer

[0108] In some preferred embodiments of the method for regenerating an epoxidation reactor according to the first aspect or the combined preparation method of an oxidized olefin according to the second aspect, the mixture formed in (i) further contains an additive, preferably selected from the group consisting of potassium salts, ammonia, ammonium salts, hydroxyethylphosphonic acid, hydroxyethylphosphate, and mixtures of two or more thereof; wherein the additive is selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium formate, potassium acetate, potassium bicarbonate, hydroxyethylphosphonic acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonia, and mixtures of two or more thereof, and is preferably selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, hydroxyethylphosphonic acid, ammonia, and mixtures of two or more thereof.

[0109] Catalyst

[0110] In some preferred embodiments of the method for regenerating an epoxidation reactor according to the first aspect or the combined preparation method of an oxidized olefin according to the second aspect, the catalyst containing a titanium-containing zeolite has a framework structure containing Si, O, and Ti.

[0111] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the alkylene oxide according to the second aspect, the catalyst comprising a titanium-containing zeolite contains Ti in an amount in the range of 0.2% to 5% by weight, preferably in the range of 0.5% to 4% by weight, more preferably in the range of 1.0% to 3% by weight, more preferably in the range of 1.2% to 2.5% by weight, more preferably in the range of 1.4% to 2.2% by weight, calculated as elemental Ti and based on the total weight of the titanium-containing zeolite.

[0112] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the alkylene oxide according to the second aspect, the titanium-containing zeolite having a framework structure containing Si, O, and Ti in the titanium-containing zeolite has the following framework structures or a mixed structure of two or more of these framework structure types: ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITQ, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAR, MAZ, MCM-22(S), MCM-36, MCM-56, MEI, MEL, MEP, MER, MIT-1, MMFI, MFS, MON, MOR, MSE, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NEES, NON, NPO, OBW, OFF, OSI, OSO, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZON SVR, SVY; more preferably, the titanium-containing zeolite having a framework structure containing Si, O, and Ti is a titanium-containing zeolite having an MFI framework type, a MEL framework type, a MWW framework type, a MCM-22(S) framework type, a MCM-56 framework type, an IEZ-MWW framework type, a MCM-36 framework type, an ITQ framework type, a BEA framework type, a MOR framework type, or a mixed structure of two or more of these framework types; more preferably, the MFI framework type or the MWW framework type; more preferably, the titanium-containing zeolite having a framework structure containing Si, O, and Ti has the framework type MFI;More preferably, the zeolite material having a framework structure containing Si, O and Ti is titanium silicalite-1 (TS-1).;

[0113] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxy olefin according to the second aspect, the catalyst containing the titanium-containing zeolite further contains a binder.

[0114] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxy olefin according to the second aspect, the catalyst containing the titanium-containing zeolite is in the form of a molded article, preferably in the form of an extrudate or granules.

[0115] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxy olefin according to the second aspect, 95 wt% to 100 wt%, preferably 98 wt% to 100 wt%, more preferably 99 wt% to 100 wt%, more preferably 99.5 wt% to 100 wt%, more preferably 99.9 wt% to 100 wt% of the molded article is composed of the titanium-containing zeolite and the binder.

[0116] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxy olefin according to the second aspect, 95 wt% to 100 wt%, preferably 98 wt% to 100 wt%, more preferably 99 wt% to 100 wt%, more preferably 99.5 wt% to 100 wt%, more preferably 99.9 wt% to 100 wt% of the binder contained in the molded article is composed of Si and O.

[0117] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxy olefin according to the second aspect, the catalyst containing the titanium-containing zeolite, preferably the molded article, contains a binder, calculated as SiO2, in an amount in the range of 2 wt% to 90 wt%, preferably in the range of 5 wt% to 70 wt%, more preferably in the range of 10 wt% to 50 wt%, more preferably in the range of 15 wt% to 30 wt%, more preferably in the range of 20 wt% to 25 wt% based on the total weight of the catalyst containing the titanium-containing zeolite, preferably based on the total weight of the molded article, and / or wherein the catalyst containing the titanium-containing zeolite, preferably the molded article, contains the titanium-containing zeolite in an amount in the range of 10 wt% to 98 wt%, preferably in the range of 30 wt% to 95 wt%, more preferably in the range of 50 wt% to 90 wt%, more preferably in the range of 70 wt% to 85 wt%, more preferably in the range of 75 wt% to 80 wt% based on the total weight of the catalyst containing the titanium-containing zeolite, preferably based on the total weight of the molded article.

[0118] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxidized olefin according to the second aspect, at least three separate feed streams are provided in (i), wherein at least one feed stream is a feed stream provided to the reactor together with an organic solvent, wherein at least one feed stream is a feed stream provided to the reactor together with an olefin, and wherein at least one feed stream is a feed stream provided to the reactor together with hydrogen peroxide and water, and wherein optionally, at least one additional separate stream is provided to the reactor, and the at least one additional separate stream is a feed stream provided to the reactor together with an additive.

[0119] The separate feed streams can be combined and introduced into the reactor as a single feed stream or as a combined feed stream, such as, for example, a feed stream containing an organic solvent, hydrogen peroxide and water and a feed stream containing an olefin, or a feed stream containing an organic solvent and an olefin and a feed stream containing hydrogen peroxide and water, or a feed stream containing an organic solvent and a feed stream containing an olefin, and a feed stream containing hydrogen peroxide and water. The optional additive can be added as a separate feed stream or can be mixed into one or more of the above feed streams. If more than one feed stream is used, the separate feed streams are mixed before they are introduced into the reactor or are appropriately mixed after they have been introduced into the reactor.

[0120] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxidized olefin according to the second aspect, the organic solvent, hydrogen peroxide, water, olefin and optional additive are mixed before entering the reactor so as to provide a single feed stream containing the organic solvent, hydrogen peroxide, water, olefin and optional additive to the reactor.

[0121] Preferably, the respective separate streams are appropriately mixed to obtain a reaction feed consisting of at least one liquid phase. Even more preferably, the separate streams are appropriately mixed to obtain a feed stream consisting of one liquid phase.

[0122] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxidized olefin according to the second aspect, the epoxidation reaction conditions according to (ii) include fixed bed conditions.

[0123] In some preferred embodiments of the regeneration method of the epoxidation reactor of the first aspect or the combined preparation method of the epoxidized olefin according to the second aspect, the epoxidation reaction conditions according to (ii) include trickle bed conditions. According to this embodiment, the organic solvent, water and hydrogen peroxide and optionally the additive are mixed before entering the reactor. The olefin is introduced into the reactor as a separate stream. Then a reaction mixture is formed in the reactor.

[0124] In some preferred embodiments of the regeneration method of the epoxidation reactor according to the first aspect or the combined preparation method of the alkylene oxide according to the second aspect, steps (i), (ii) and (iii) are carried out in a continuous mode or in a batch mode, preferably in a continuous mode.

[0125] The present invention is further illustrated by the following groups of embodiments and combinations of embodiments resulting from the indicated dependencies and cross-references. In particular, it should be noted that in each case where a range of embodiments is mentioned, for example in the context of terms such as "any one of embodiments (1) to (4)", each embodiment within that range is meant to be explicitly disclosed to a person skilled in the art, i.e., the wording of the term should be understood by the skilled person as being synonymous with "any one of embodiments (1), (2), (3) and (4)". Additionally, it is expressly pointed out that the following groups of embodiments are not groups of claims defining the scope of protection, but rather appropriate structured parts of the description of the general and preferred aspects of the present invention.

[0126] 1. A method for regenerating an epoxidation reactor that has been used in a process for preparing an alkylene oxide, the process comprising:

[0127] (i) Supplying an organic solvent, an olefin, an epoxidizing agent and water to the reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone, so as to form a reaction mixture comprising an olefin, hydrogen peroxide, water and an organic solvent;

[0128] (ii) Subjecting the mixture of (i) in the epoxidation zone of the reactor to epoxidation conditions in the presence of the catalyst, thereby obtaining a mixture comprising water, the organic solvent and an alkylene oxide;

[0129] (iii) Removing from the reactor the mixture comprising water, the organic solvent and an alkylene oxide obtained in (ii);

[0130] Thereby a precipitate is deposited in the reactor;

[0131] The regeneration method comprises:

[0132] (a) Stopping the supply of the organic solvent, the olefin, the epoxidizing agent and water to the reactor;

[0133] (b) Introducing a liquid aqueous system into the reactor, wherein the liquid aqueous system contains a chelating agent that contains at least three oxygen atoms and optionally one or more nitrogen atoms in its structure, and when forming a chelate with a metal cation, the chelating agent is capable of forming at least three coordination bonds with the metal cation via the at least three oxygen atoms and optionally via one or more of its nitrogen atoms.

[0134] 2. The method for regenerating an epoxidation system according to Embodiment 1,

[0135] wherein the chelating agent is selected from the group consisting of: ethylenediaminetetraacetic acid (EDTA); diethylenetriaminepentaacetic acid (DTPA); N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA); N-(1-carboxyethyl)iminodiacetic acid (MGDA); nitrilotriacetic acid (NTA); L-glutamic acid-N,N-diacetic acid (GLDA); amino-tris

[0136] (methylenephosphonic acid) (AMTP); ethanol diglycine (EDG); diphosphonic acid of formula (I)

[0137] acid

[0138] (OH)2(O═)P-CR 1 R 2 -P(═O)(OH)2 (I),

[0139] wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxy group, and C1-C5 alkyl groups; and mixtures of two or more of these chelating agents.

[0140] 3. The method for regenerating an epoxidation system according to Embodiment 1 or 2,

[0141] wherein the chelating agent comprises, preferably is diphosphonic acid of formula (I)

[0142] (OH)2(O═)P-CR 1 R 2 -P(═O)(OH)2 (I),

[0143] wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxy group, and C1-C5 alkyl groups, wherein R 1 is preferably a hydroxy group and R 2 is preferably a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, hydroxyethane diphosphonic acid, HEDP).

[0144] 4. The regeneration method of an epoxidation reactor according to any one of Embodiments 1 to 3, wherein the liquid aqueous system used in (b) contains a chelating agent in the range of 0.01% to 50% by weight, preferably in the range of 0.02% to 25% by weight, more preferably in the range of 0.05% to 10% by weight, preferably a diphosphonic acid of formula (I), more preferably HEDP, more preferably a chelating agent in the range of 0.1% to 5% by weight, preferably a diphosphonic acid of formula (I), more preferably HEDP, each based on 100% by weight of the total weight of the liquid aqueous system.

[0145] 5. The regeneration method of an epoxidation reactor according to any one of Embodiments 1 to 4,

[0146] wherein step (b) includes:

[0147] (b.1) introducing a first portion of the liquid aqueous system containing a chelating agent into the reactor;

[0148] (b.2) at least partially removing the first portion of the liquid aqueous system from the reactor.

[0149] 6. The regeneration method of an epoxidation reactor according to any one of Embodiments 1 to 5,

[0150] wherein step (b) includes:

[0151] (b.1) introducing a first portion of the liquid aqueous system containing a chelating agent into the reactor;

[0152] (b.2) at least partially removing the first portion of the liquid aqueous system from the reactor;

[0153] (b.3) optionally introducing another portion of the liquid aqueous system containing a chelating agent into the reactor;

[0154] (b.4) optionally at least partially removing the liquid aqueous system from the reactor;

[0155] wherein steps (b.3) and (b.4) are optionally repeated 1 to 10 times.

[0156] 7. The regeneration method of an epoxidation reactor according to any one of Embodiments 1 to 6, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out with a gaseous stream passing through the liquid aqueous system, wherein the gaseous stream preferably contains at least 90% by volume, more preferably at least 95% by volume, more preferably at least 98% by volume of an inert gas based on the total volume of the gaseous stream.

[0157] 8. The regeneration method of the epoxidation reactor according to any one of embodiments 1 to 7, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a temperature in the reactor within the range of 0.1 °C to the boiling point of the liquid aqueous system, preferably within the range of 0.5 °C to 90 °C, more preferably within the range of 5 °C to 50 °C, and even more preferably within the range of 10 °C to 40 °C.

[0158] 9. The regeneration method of the epoxidation reactor according to any one of embodiments 1 to 8, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a pressure in the reactor within the range of 0.05 MPa to 5.0 MPa, preferably within the range of 0.08 MPa to 1.0 MPa, and more preferably within the range of 0.1 MPa to 0.15 MPa.

[0159] 10. The regeneration method of the epoxidation reactor according to any one of embodiments 1 to 9, wherein the reactor comprises one or more vertically arranged tubes, each tube having a specific length (height), with a bottom end and a top end, wherein the catalyst is present between positions H1 and H2 in the tube, where H2 is higher than H1 in the tube, and the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that the liquid level in the tube is at least at the height of H2, preferably at a height within the range between H1 and H2, more preferably at a height within the range of 80% to 5% below H2, more preferably at a height within the range of 70% to 10% below H2, more preferably at a height within the range of 60% to 20% below H2, more preferably at a height within the range of 50% to 25% below H2, and more preferably at a height within the range of 40% to 30% below H2, each relative to the distance between H1 and H2 being 100%.

[0160] 11. A combined preparation method of an alkylene oxide, the combined preparation method comprising a preparation stage and a regeneration stage of an epoxidation reactor,

[0161] The preparation stage comprises:

[0162] (i) Supplying an organic solvent, an alkene, an epoxidizing agent, and water to the reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone so as to form a reaction mixture comprising an alkene, hydrogen peroxide, water, and an organic solvent;

[0163] (ii) In the presence of the catalyst, subjecting the mixture formed in (i) in the epoxidation reactor to epoxidation conditions to obtain a mixture comprising water, the organic solvent, and an alkylene oxide;

[0164] (iii) Removing from the reactor the mixture comprising water, the organic solvent, and an alkylene oxide obtained in (ii);

[0165] Thereby causing a precipitate to deposit in the reactor;

[0166] The regeneration stage comprises:

[0167] (a) Stopping the introduction of the mixture of (i) into the reactor;

[0168] (b) Introducing a liquid aqueous system into the reactor, wherein the liquid aqueous system comprises a chelating agent that comprises at least three oxygen atoms and optionally one or more nitrogen atoms in its structure, and when forming a chelate with a metal cation, the chelating agent is capable of forming at least three coordination bonds with the metal cation via the at least three oxygen atoms and optionally via one or more of its nitrogen atoms.

[0169] 12. The combined preparation method of an alkylene oxide comprising a preparation stage and a regeneration stage of an epoxidation reactor according to embodiment 11,

[0170] wherein the chelating agent is selected from the group consisting of: ethylenediaminetetraacetic acid (EDTA); diethylenetriaminepentaacetic acid (DTPA); N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA); N-(1-carboxyethyl)iminodiacetic acid (MGDA); nitrilotriacetic acid (NTA); L-glutamic acid-N,N-diacetic acid (GLDA); aminotris(methylenephosphonic acid) (AMTP); ethanol diglycine (EDG); diphosphonic acid of formula (I) (OH)2(O=)P-CR 1 R 2 -P(=O)(OH)2 (I),

[0171] wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, and C1 to C5 alkyl groups;

[0172] and mixtures of two or more of these chelating agents.

[0173] 13. The combined preparation method of an alkylene oxide comprising a preparation stage and a regeneration stage of an epoxidation reactor according to embodiment 11 or 12,

[0174] wherein the chelating agent comprises, preferably is the diphosphonic acid of formula (I)

[0175] (OH)2(O=)P-CR 1 R 2 -P(=O)(OH)2(I),

[0176] wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxy group, and a C1 to C5 alkyl group, wherein R 1 is preferably a hydroxy group and R 2 is preferably a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP).

[0177] 14. The combined preparation method of an epoxidized olefin including a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 13, wherein the liquid aqueous system used in (b) contains a chelating agent in the range of 0.01 wt% to 50 wt%, preferably in the range of 0.02 wt% to 25 wt%, more preferably in the range of 0.05 wt% to 10 wt%, preferably a diphosphonic acid, more preferably HEDP, more preferably a chelating agent in the range of 0.1 wt% to 5 wt%, preferably a diphosphonic acid, more preferably HEDP, each based on the total weight of the liquid aqueous system being 100 wt%.

[0178] 15. The combined preparation method of an epoxidized olefin including a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 10 to 12, wherein step (b) includes:

[0179] (b.1) Introducing a first portion of the liquid aqueous system containing a chelating agent into the reactor;

[0180] (b.2) Removing at least part of the first portion of the liquid aqueous system from the reactor.

[0181] 16. The combined preparation method of an epoxidized olefin including a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 15, wherein step (b) includes:

[0182] (b.1) Introducing a first portion of the liquid aqueous system containing a chelating agent into the reactor;

[0183] (b.2) Removing at least part of the first portion of the liquid aqueous system from the reactor;

[0184] (b.3) Optionally introducing another portion of the liquid aqueous system containing a chelating agent into the reactor;

[0185] (b.4) Optionally, at least partially remove the other portion of the liquid aqueous system from the reactor;

[0186] Wherein steps (b.3) and (b.4) are optionally repeated from 1 to 10 times.

[0187] 17. The combined preparation method of an epoxidized olefin comprising a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 16, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out with a gaseous stream passing through the liquid aqueous system, wherein the gaseous stream preferably contains at least 90% by volume, more preferably at least 95% by volume, more preferably at least 98% by volume of an inert gas based on the total volume of the gaseous stream.

[0188] 18. The combined preparation method of an epoxidized olefin comprising a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 17, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a temperature in the reactor in the range of 0.1 °C to the boiling point of the liquid aqueous system, preferably in the range of 0.5 °C to 90 °C, more preferably in the range of 5 °C to 50 °C, more preferably in the range of 10 °C to 40 °C.

[0189] 19. The combined preparation method of an epoxidized olefin comprising a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 18, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out at a pressure in the reactor in the range of 0.05 MPa to 5.0 MPa, preferably in the range of 0.08 MPa to 1.0 MPa, more preferably in the range of 0.1 MPa to 0.15 MPa.

[0190] 20. A combined preparation method of an epoxidized olefin including a preparation stage and a regeneration stage of an epoxidation reactor according to any one of embodiments 11 to 19, wherein the reactor includes one or more vertically arranged tubes, each tube having a specific length (height), having a bottom end and a top end, wherein the catalyst is present between positions H1 and H2 in the tube, where H2 is higher than H1 in the tube, and introducing the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) such that the liquid level in the tube is at a height of at least H2, preferably at a height within the range between H1 and H2, more preferably at a height within the range of 80% to 5% below H2, more preferably at a height within the range of 70% to 10% below H2, more preferably at a height within the range of 60% to 20% below H2, more preferably at a height within the range of 50% to 25% below H2, more preferably at a height within the range of 40% to 30% below H2, each relative to the distance between H1 and H2 being 100%.

[0191] 21. A regeneration method of an epoxidation reactor according to any one of embodiments 1 to 10 or a combined preparation method of an epoxidized olefin according to any one of embodiments 11 to 20, wherein the epoxidizing agent is hydrogen peroxide, wherein the hydrogen peroxide is preferably provided in the form of an aqueous hydrogen peroxide solution, and the aqueous hydrogen peroxide solution preferably has a total organic carbon content (TOC) of hydrogen peroxide contained per kg of the aqueous hydrogen peroxide solution in the range of 100 mg to 800 mg, preferably in the range of 120 mg to 750 mg, more preferably in the range of 150 mg to 700 mg, as determined according to DIN EN 1484;

[0192] And / or

[0193] wherein the hydrogen peroxide has a pH in the range of 0 to 3.0, preferably in the range of 0.1 to

[0194] 2.5, more preferably in the range of 0.5 to 2.3, as determined with a pH-sensitive glass electrode according to AM7160;

[0195] And / or

[0196] wherein relative to the total weight of the aqueous hydrogen peroxide solution, the hydrogen peroxide contains 20% to 85% by weight, preferably 30% to 75% by weight, more preferably 40% to 70% by weight of hydrogen peroxide;

[0197] And / or

[0198] wherein the hydrogen peroxide is obtained from or obtainable from the anthraquinone process.

[0199] 22. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the organic solvent is an organic epoxidation solvent, preferably the organic solvent is selected from the group consisting of alcohols, acetonitrile, propionitrile, and mixtures of two or more thereof; more preferably selected from the group consisting of alcohols, acetonitrile, and mixtures of alcohols and acetonitrile; more preferably the organic solvent contains at least one alcohol, wherein the alcohol is preferably a C1-C5 monohydric alcohol or a mixture of two or more C1-C5 alcohols, and more preferably the alcohol contains at least methanol.

[0200] 23. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the alkene is a C2-C10 chain alkene, preferably a C2-C5 chain alkene, more preferably a C2-C4 chain alkene, more preferably ethylene (C2 alkene) or propylene (C3 chain alkene), and more preferably propylene (C3 chain alkene).

[0201] 24. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the mixture formed in (i) further contains an additive, preferably selected from the group consisting of potassium salts, ammonia, ammonium salts, hydroxyethylphosphonic acid, hydroxyethylphosphate, and mixtures of two or more thereof; wherein the additive is selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium formate, potassium acetate, potassium bicarbonate, hydroxyethylphosphonic acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonia, and mixtures of two or more thereof, and preferably selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, hydroxyethylphosphonic acid, ammonia, and mixtures of two or more thereof.

[0202] 25. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the catalyst containing titanium zeolite has a framework structure containing Si, O, and Ti.

[0203] 26. A method for regenerating an epoxidation reactor according to any one of Embodiments 1 to 10 or a method for preparing a combination of alkylene oxides according to any one of Embodiments 11 to 20, wherein the catalyst containing a titanium-containing zeolite contains Ti in an amount in the range of 0.2% by weight to 5% by weight, preferably in the range of 0.5% by weight to 4% by weight, more preferably in the range of 1.0% by weight to 3% by weight, more preferably in the range of 1.2% by weight to 2.5% by weight, more preferably in the range of 1.4% by weight to 2.2% by weight, calculated as elemental Ti and based on the total weight of the titanium-containing zeolite.

[0204] 27. The method for regenerating an epoxidation reactor according to any one of Embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of Embodiments 11 to 20, wherein the titanium-containing zeolite having a framework structure containing Si, O, and Ti in the titanium-containing zeolite has the following framework structure or a mixed structure of two or more of these framework structure types: ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITQ, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAR, MAZ, MCM-22(S), MCM-36, MCM-56, MEI, MEL, MEP, MER, MIT-1, MMFI, MFS, MON, MOR, MSE, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NEES, NON, NPO, OBW, OFF, OSI, OSO, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZONSVR, SVY; more preferably, the titanium-containing zeolite having a framework structure containing Si, O, and Ti is a titanium-containing zeolite having an MFI framework type, a MEL framework type, a MWW framework type, a MCM-22(S) framework type, a MCM-56 framework type, an IEZ-MWW framework type, a MCM-36 framework type, an ITQ framework type, a BEA framework type, a MOR framework type, or a mixed structure of two or more of these framework types; more preferably, the MFI framework type or the MWW framework type;More preferably, the titanium-containing zeolite having a framework structure containing Si, O, and Ti has a framework type of MFI; more preferably, the zeolite material having a framework structure containing Si, O, and Ti is titanium silicalite-1 (TS-1).;

[0205] 28. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the catalyst containing the titanium-containing zeolite further contains a binder.

[0206] 29. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein the catalyst containing the titanium-containing zeolite is in the form of a molded article, preferably in the form of an extrudate or granules.

[0207] 30. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein 95% to 100% by weight, preferably 98% to 100% by weight, more preferably 99% to 100% by weight, more preferably 99.5% to 100% by weight, more preferably 99.9% to 100% by weight of the molded article consists of the titanium-containing zeolite and the binder.

[0208] 31. The method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or the method for preparing a combination of alkylene oxides according to any one of embodiments 11 to 20, wherein 95% to 100% by weight, preferably 98% to 100% by weight, more preferably 99% to 100% by weight, more preferably 99.5% to 100% by weight, more preferably 99.9% to 100% by weight of the binder contained in the molded article consists of Si and O.

[0209] 32. A method for regenerating an epoxidation reactor according to any one of Embodiments 1 to 10 or a method for preparing a combination of alkylene oxides according to any one of Embodiments 11 to 20, wherein the catalyst containing titanium zeolite, preferably the molded article, contains the binder, calculated as SiO2, in an amount in the range of 2% to 90% by weight, preferably in the range of 5% to 70% by weight, more preferably in the range of 10% to 50% by weight, more preferably in the range of 15% to 30% by weight, more preferably in the range of 20% to 25% by weight, based on the total weight of the catalyst containing titanium zeolite, preferably based on the total weight of the molded article, and / or wherein the catalyst containing titanium zeolite, preferably the molded article, contains the titanium zeolite, in an amount in the range of 10% to 98% by weight, preferably in the range of 30% to 95% by weight, more preferably in the range of 50% to 90% by weight, more preferably in the range of 70% to 85% by weight, more preferably in the range of 75% to 80% by weight, based on the total weight of the catalyst containing titanium zeolite, preferably based on the total weight of the molded article.

[0210] 33. A method for regenerating an epoxidation reactor according to any one of Embodiments 1 to 10 or a method for preparing a combination of alkylene oxides according to any one of Embodiments 11 to 20, wherein at least three separate feed streams are provided in (i), wherein at least one feed stream is a feed provided to the reactor together with the organic solvent, wherein at least one feed stream is a feed provided to the reactor together with the alkene, and wherein at least one feed stream is a feed provided to the reactor together with the hydrogen peroxide and the water, and wherein optionally, at least one additional separate stream is provided to the reactor, and the at least one additional separate stream is a feed provided to the reactor together with the additive.

[0211] 34. A method for regenerating an epoxidation reactor according to any one of Embodiments 1 to 10 or a method for preparing a combination of alkylene oxides according to any one of Embodiments 11 to 20, wherein the organic solvent, hydrogen peroxide, water, alkene and optional additive are mixed before entering the reactor so as to provide a single feed stream containing the organic solvent, hydrogen peroxide, water, alkene and optional additive to the reactor.

[0212] 35. A method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or a method for preparing a combination of epoxidized olefins according to any one of embodiments 11 to 20, wherein the epoxidation reaction conditions according to (ii) include fixed bed conditions, wherein preferably an organic solvent, hydrogen peroxide, water, an olefin and an optional additive are mixed before entering the reactor so as to provide a single feed stream comprising the organic solvent, hydrogen peroxide, water, the olefin and the optional additive to the reactor.

[0213] 36. A method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or

[0214] a method for preparing a combination of epoxidized olefins according to any one of embodiments 11 to 20, wherein the epoxidation reaction conditions according to (ii) include trickle bed conditions, wherein preferably

[0215] an organic solvent, water and hydrogen peroxide and optionally an additive are mixed before entering the

[0216] reactor, and the olefin is introduced into the reactor as a separate stream.

[0217] 37. A method for regenerating an epoxidation reactor according to any one of embodiments 1 to 10 or

[0218] a method for preparing a combination of epoxidized olefins according to any one of embodiments 11 to 20, wherein steps (i), (ii) and (iii) are carried out in continuous mode or in batch mode, preferably in continuous mode.

[0219] The present invention is further illustrated by the following reference examples, comparative examples and examples. Examples

[0220] Reference Example 1: Preparation of titanium-containing zeolite (TS-1)

[0221] In a reaction vessel, 550 kg of deionized water was provided and stirred. 400 kg of TPAOH (tetra-n-propylammonium hydroxide) was added under stirring. Stirring was continued for 1 hour. The resulting mixture was transferred to a suitable container. The reaction vessel was washed twice with a total of 2000 l of deionized water. In the washed reaction vessel, 300 kg of TEOS (tetraethyl orthosilicate) was provided and stirred. A mixture of 80 kg of TEOS and 16 kg of TEOT (tetraethyl orthotitanate) was added to 300 kg of TEOS. The remaining 340 kg of TEOS was added.

[0222] Subsequently, TPAOH solution was added and the resulting mixture was stirred for another hour. Then, the reaction vessel was heated and the ethanol obtained was separated by distillation. When the internal temperature of the vessel reached 95 °C, the reaction vessel was cooled. 1143 kg of water was added to the resulting suspension in the vessel and the mixture was stirred for another hour. Crystallization was carried out at 175 °C under autogenous pressure for 24 hours. The resulting titanium silicalite-1 crystals were separated, dried and calcined in air at a temperature of 500 °C.

[0223] The resulting powder and were mixed in a grinder and mixed for 5 minutes. Within 10 minutes, a polystyrene dispersion was continuously added. Subsequently, 15 l of AS-40 was continuously added. The resulting mixture was mixed for 5 minutes and poly(ethylene oxide) was continuously added within 15 minutes, followed by mixing for 10 minutes. Then, water was added. The formable material was extruded through a matrix with round holes having a diameter of 1.5 mm. The resulting strands were dried in a belt dryer at a temperature of 120 °C for 2 hours and calcined in lean air (100 m 3 / h air / 100 m 3 / h nitrogen) at a temperature of 550 °C. The yield was 89 kg of extrudate.

[0224] For subsequent water treatment of the extrudate, 880 kg of deionized water was filled into the corresponding stirring vessel and the extrudate was added. The vessel was heated to an internal temperature of 139 °C to 143 °C under a pressure of 84 mbar. The resulting pressure was in the range of 2.1 bar to 2.5 bar. The water treatment was carried out for 36 hours. The extrudate was separated by filtration, dried in air at 123 °C for 16 hours, heated to a temperature of 470 °C at 2 °C / min and held at a temperature of 490 °C in air for 5 hours. The yield was 81.2 kg.

[0225] Reference Example 2: Experimental setup for epoxidation in a small-scale apparatus

[0226] The TS-1 catalyst obtained according to Reference Example 1 above was charged into the reaction tube of a small-scale apparatus with a length of 180 cm and a volume of 300 ml. The tube diameter was 0.75 inches (1.905 cm) and the wall thickness was 0.07 inches (0.19 cm). A smaller (0.125 inches (0.3175 cm)) tube containing a thermocouple for measuring the temperature in the catalyst bed was installed in the center of the reaction tube.

[0227] Feed: 54 g / h propylene (liquid)

[0228] 94 g / h H2O2 aqueous solution (40 wt% H2O2)

[0229] Solvent: 370 g / h methanol

[0230] Additive solution: 4 g / h aqueous solution of K2HPO4 (0.3 wt% K2HPO4)

[0231] (Adjust the flow rate to maintain 130 μmol K + / (mol H2O2))

[0232] Propylene is stored in a 50 l gas cylinder including a dip tube for transfer to a small-scale device by a nitrogen pressure of 25 bar. The exact amount is measured using a Bronkhorst flow meter in the range of 0 g / h - 500 g / h, and the flow rate is controlled by a Flowserve control valve. Hydrogen peroxide is transferred to the reactor using a Grundfos pump DME2. The amount is determined using a balance. The measurement result is shown in liters per minute. The corresponding additive solution is fed into the reactor using a hydrogen peroxide LC pump. The exact amount is determined using a balance. To feed methanol, a Lewa pump with a range of 0 ml / h - 1500 ml / h is used. The feed control is completed using a Lewa KMM. A Flowserve control valve is used for nitrogen feed. The amount is measured using a Bronkhorst flow meter in the range of 0 Nl / h - 200 Nl / h. "Nl / h" means standard liters per hour, where 1 standard liter is the amount of gas that fills 1 liter at 0 °C and 1013 mbar (see DIN 1343 from January 1990).

[0233] Methanol, propylene, aqueous hydrogen peroxide solution, and aqueous K2HPO4 additive solution enter the reactor tube via a static mixer [0.25 inches (0.635 cm) - mixer], such that a combined feed stream is formed, where the feed direction is from the bottom to the top of the reaction tube.

[0234] The experiment is carried out at an absolute pressure of 20 bar. The temperature in the reactor is controlled using a cooling jacket circuit with oil to ensure a conversion of approximately 90% of H2O2. The typical starting temperature is approximately 40 °C - 45 °C. Then the temperature is slowly increased to approximately 60 °C - 65 °C over a run time of 600 hours to 700 hours. At the start of the run, the reactor is cooled because otherwise the exotherm would overheat the reactor. Near the end of the run, the reactor is heated to reach a temperature of 60 °C - 65 °C.

[0235] Pass the reactor effluent through a 2-micron filter to remove fine (catalyst) particles before it enters the first separator. The bottom water level valve controls the water level at 25% in the first separator, while the upper pressure valve sets a pressure of 20 bar on the entire upstream reaction system. The second separator also operates at a liquid level of 25%, while the upper pressure valve reduces the pressure to 2 bar. This lower pressure is used to allow the flashing of unreacted propylene, thus allowing safe sampling and having an additional safety buffer. Each of the two separators has a volume of 2 liters and is maintained at a temperature of 5 °C using cooling water. Feed a nitrogen gas stream of 5 Nl / h through the entire system (reactor → 1st separator → 2nd separator → exhaust system) to maintain a sufficient gas flow in the exhaust direction to ensure that trace oxygen formed by the partial decomposition of H2O2 is flashed out and can be analyzed at the end of the exhaust pipe.

[0236] Reference Example 3: Sample of feed precipitate

[0237] Obtain a sample of the feed precipitate from a (large-scale) HPPO plant, where propylene is epoxidized using titanium silicate zeolite catalyst of MFI framework type, i.e., TS-1 catalyst, with hydrogen peroxide in a solvent mixture containing water and methanol.

[0238] The plant includes several reactors operating in parallel, where each reactor is a shell-and-tube reactor having a bundle of vertically arranged tubes made of stainless steel. The selected tubes are equipped with coaxially placed multipoint thermocouples with multiple equally spaced measurement points wrapped in a suitable thermocouple sheath. All the tubes of the reactor contain heterogeneous titanium silicate zeolite-1 (TS-1) catalyst strands. Through the tubes, the feed mixture passes from the bottom to the top, i.e., in an upstream mode.

[0239] The feed mixture consisting of methanol (69.0 wt%), propylene (11.9 wt%), water (11.7 wt%), and hydrogen peroxide (7.4 wt%) is composed of a single liquid phase and is fed to the shell-and-tube reactor via a feed line at room temperature (25 °C), divided into sub-streams, where one sub-stream S(i) is fed to each tube via a feed line. In addition, the liquid reaction mixture in the reactor is composed of a single phase. The feed mixture has been made from a methanol stream, a propylene stream, and an aqueous hydrogen peroxide solution stream with a hydrogen peroxide concentration of about 40 wt%.

[0240] The heat of reaction is removed by circulating a constant-temperature heat transfer medium (water / glycol mixture) in parallel flow with the feed mixture on the shell side. The flow rate of the heat transfer medium is adjusted such that the temperature difference between the inlet and the outlet does not exceed 1 °C. The reaction temperature mentioned below is defined as the temperature of the heat transfer medium entering the reactor shell. At the reactor outlet, the pressure is controlled by a pressure regulator and maintained constant at 2 MPa. The temperature of the cooling medium is selected in such a way that the total conversion of hydrogen peroxide at the outlet of the shell-and-tube reactor is exactly 90%.

[0241] Precipitates are formed during the operation of the plant and deposited in the feed line, on the filter (if any) inside the feed line, and in the reactor, especially on the catalyst support at the inlet of the inlet tubes, and also partially on the catalyst, and are removed during the regeneration interruption of each reactor.

[0242] The removed precipitates are characterized by X-ray fluorescence (XRF) analysis of solid samples, and the results are shown in Table 1. Here and below, for simplicity, all elements are shown without charge but exist in the form of cations, where the charge is compensated by appropriate anions.

[0243] Table 1

[0244] Elemental metal composition of precipitate in collected precipitate (solid sample)

[0245]

[0246] Example 1: Dissolution test with water and different acidic phosphates in an aqueous solution

[0247] The following procedure is used for the dissolution test of the feed precipitate sample as described in Reference Example 3:

[0248] 1. An aqueous solution of hydroxyethylidene diphosphonic acid (HEDP) with a specific strength (in the range of 0.050 wt% to 0.985 wt%, details are shown in Table 2) is prepared from a 62.6 wt% aqueous solution of HEDP (Spectrum Lab Products) and deionized water. For comparison, another acidic phosphate, namely sodium acid pyrophosphate (SAPP, 99.1 wt% solution from Sigma-Aldrich), is used, and the concentration of the aqueous solution is also adjusted to a specific strength with deionized water (details are shown in Table 2).

[0249] 2. Approximately 0.1 g of the feed precipitate is weighed into 20 ml vials, a total of 10 vials. The correct starting amount of the precipitate is shown in Table 2.

[0250] 3. 10 g of water or an aqueous solution of HEDP with a specific concentration or an aqueous solution of SAPP with a specific concentration is weighed into the vials.

[0251] 4. Shake the vial at room temperature (25 °C) for at least 2 hours (Thermo Scientific Multipurpose Rotator, model 2314), but check after 1 hour to see if the precipitate has dissolved.

[0252] 5. Visually inspect if there is still precipitate.

[0253] 6. Vacuum filter the solution, where:

[0254] a. Dry a 5-μm Millipore Durapore SVPP 47-mm filter disc in a vacuum oven at approximately 60 °C for 1 hour. After that, weigh the filter disc and record the weight.

[0255] b. Place the filter disc from a. in place in the vacuum filter.

[0256] c. Shake the vial and pour the mixture onto the filter under vacuum.

[0257] d. Rinse the vial with deionized water (3 times, 5 g each time), and pour through the filter to get all the solids out of the vial.

[0258] 7. Dry the used filter disc in a vacuum oven at approximately 60 °C for 1 hour.

[0259] 8. Weigh the dried filter disc with the solid on it and record the weight.

[0260] 9. Calculate the amount of solid that has dissolved by the difference in weight.

[0261] All data were collected at room temperature of approximately 23 °C. A baseline check was first performed by passing 25 g of water through each of 3 blank filters (equivalent to phosphate solution + rinse water). The amount of solid collected on the filter ≤ 0.0004 g or ≤ 0.4% of the initial precipitate charge used in the experiment. Therefore, the contribution of deionized water to the final result is very small.

[0262] The results are shown in Table 2.

[0263]

[0264] In the case of pure water as the solvent, only 4.6 wt% and 17.8 wt% of the solid dissolved. When SAPP was added to water up to 1 wt%, the result was not greatly improved, with dissolution in the range of 20 wt%. On the other hand, incremental addition of HEDP to water significantly improved dissolution. With 0.05 wt% HEDP, the solid dissolution was more than twice that with 0.05 wt% SAPP (see Table 2, No. 2 and No. 6). For 0.5 wt% and 1.0 wt% HEDP solutions, the solid dissolved in the mid - 90 wt% range (see Table 2, No. 7, 8 and 10).

[0265] By visual observation, increasing the concentration of HEDP in the aqueous solution promoted dissolution. The mixture made with the aqueous solution having 0.5 wt% HEDP was still quite turbid with solids after shaking for 1 hour, while when using the aqueous solution having 1 wt% HEDP, the solids seemed to be almost completely dissolved. The mixture made with the aqueous solution having 0.5 wt% HEDP solution clarified after shaking for 2 hours. It was later determined that the precipitate (0.1 g) mixed with the aqueous solution having 5 wt% HEDP (10 g) dissolved within about 2 minutes when gently shaken by hand, and even faster when the HEDP concentration in the aqueous solution was increased to 10 wt%.

[0266] The ratio of HEDP or SAPP to metal in the precipitate was calculated to see if there was a relationship with dissolution. Based on the concentrations shown in Table 1 in Reference Example 3, the two main metals Al and Fe in the precipitate were used as the basis. In the case of 1 wt% HEDP (which easily dissolves the precipitate), there was more than 1 mole of phosphate / mole of precipitate metal. For the case of 0.5 wt% HEDP (which can dissolve the precipitate although at a slower rate), the ratio was 0.8. Aiming for at least a 1:1 molar ratio of HEDP:precipitate metal should be a fairly good guide for determining the minimum amount of HEDP required for cleaning.

[0267] The characterization of the original precipitate and the residue remaining after dissolution with 1% HEDP is shown in Table 3, where the data on the precipitate metal concentration before treatment is the same as that shown in Table 1, and the analyzed residue is from No. 10 listed in Table 2. The data is based on X - ray fluorescence (XRF) analysis of solid samples.

[0268] Elemental metal composition of precipitate before and after dissolution of HEDP in Table 3

[0269]

[0270] *Data is the same as that shown in Table 1

[0271] **No. 10 in Table 2

[0272] “---” Not determined

[0273] The remaining insolubles after treatment with 1.043 wt% HEDP aqueous solution mainly consist of Fe, Si, and Al.

[0274] Among the most concentrated elements in the raw materials, according to the mass balance in the rightmost column of Table 3, the HEDP aqueous solution dissolved approximately 90% of Al, Fe, and Ca. The mass balance is based on the starting and residual solid weights and concentrations. HEDP removed almost all of P and K.

[0275] The Si and Ti concentrations increased significantly. The mass balance shows that these components are highly insoluble. The form of this Si and Ti is unknown, but since the TS-1 epoxidation catalyst consists of Si and Ti, the observation is encouraging. The washing medium must not damage the catalyst or its performance to be a viable candidate.

[0276] Example 2: Determination of the effect of washing with HEDP on process vessels

[0277] To determine whether metals might leach from the process walls to a significant level during reactor washing, a compatibility check was run. There were concerns that metals could deposit on the catalyst and reduce its performance, as well as very minor concerns about equipment corrosion. A 1 wt% HEDP aqueous solution was brought into contact with passivated stainless steel (316SS) for one week, after which the metal concentration in the solution was measured. The following procedure was followed:

[0278] 1. Clean an 8 oz. (227 g) wide-mouth bottle and seven 20 ml wide-mouth bottles:

[0279] a. Fill each wide-mouth bottle with approximately 5% HNO3 and let it stand overnight, then

[0280] b. Discard the acid and wash the wide-mouth bottles 3 times with deionized water.

[0281] 2. Prepare a 1 wt% HEDP aqueous solution in an 8 oz. (227 g) wide-mouth bottle:

[0282] a. Add 3.7 g of a nominally 60 wt% HEDP aqueous solution to the wide-mouth bottle,

[0283] b. Add deionized water to make up a total weight of 220 g, then

[0284] c. Shake to mix.

[0285] 3. Fill six 20 ml wide-mouth bottles to approximately 50% full with the 1 wt% HEDP aqueous solution, vortex, then discard the contents. Let the wide-mouth bottles drain dry.

[0286] 4. Each of six rinsed 20 ml wide-mouth bottles was filled with approximately 17 g of a 1 wt% HEDP aqueous solution. Record the weight.

[0287] 5. Four 1 / 4" (6.350 mm) passivated Swagelok end connector fittings were placed into the last empty 20 ml wide-mouth bottle. Passivation consisted of treatment with a series of solutions: trisodium phosphate / sodium metasilicate, sodium hydroxide, and then nitric acid. Rinse and vortex three times with deionized water. Add methanol for covering. Gently shake for 15 minutes, then discard the methanol and allow the remaining methanol to evaporate in a fume hood.

[0288] 6. One fitting was added to each of the four wide-mouth bottles containing the HEDP solution. The end connector fittings each weighed approximately 4.3 g and had a surface area of approximately 9.3 cm 2 in area.

[0289] 7. The wide-mouth bottles were placed in an oven preheated to 60 °C. Loosen the lids so that pressure can be released. Record the time.

[0290] 8. After 24 hours, two of the wide-mouth bottles containing the fittings were removed from the oven. Carefully remove the fittings using a plastic spatula that had been cleaned with a 5 wt% HNO3 aqueous solution and rinsed with reverse osmosis water. Label the wide-mouth bottles "1% HEDP solution from 316SS contact, 24 hours at 60 °C".

[0291] 9. After a total of 1 week, the other wide-mouth bottles were removed from the oven. Carefully remove the fittings using a plastic spatula that had been cleaned with a 5 wt% HNO3 aqueous solution and rinsed with reverse osmosis water. Label these wide-mouth bottles "1% HEDP solution from 316SS contact, 168 hours at 60 °C". Label the other wide-mouth bottles "1% HEDP solution, 168 hours at 60 °C".

[0292] 10. Analyze the metal concentration in the solutions using inductively coupled plasma mass spectrometry (ICP-MS).

[0293] The results of the metal leaching tests are shown in Table 4. Li, Be, V, Ga, Se, Rb, Sr, Nb, Rh, Ag, Cd, Sn, Cs, Ba, Pb, and Bi were all non-detectable (<5 ppb). A very small increase in two 316SS components was observed (the difference between the solution in contact with the metal for 168 hours and the 1% HEDP only), Ni and Cr <100 ppb. The increase in Fe was larger, but there was still a relatively small increase of 390 ppb after 24 hours and 570 ppb after 168 hours. After 24 hours, the rate of increase in Fe decreased significantly, possibly indicating that HEDP was completing the passivation of the surface.

[0294] The removed Fe calculated through the changes in solution mass, solution concentration, and the fitted surface area is equal to 0.01 g / m 2 / week of metal. This confirms that there are no corrosion problems.

[0295] Table 4

[0296] Average solution metal concentration from HEDP-316SS compatibility test

[0297] 1% HEDP for 168 hours 1% HEDP with 316ss for 24 hours 1% HEDP with 316ss for 168 hours ng / ml ng / ml ng / ml Mg 48 60 48 Al 158 94 154 K 22 39 25 Ti 25 24 24 Cr <5 33 69 Mn 11 32 28 Fe 14 402 583 Co <5 <5 6 Ni <5 32 48 Cu <5 12 21 Zn 6 39 35 As 18 18 17 Zr 10 <5 <5 Mo <5 8 11 Sb 12 13 14

[0298] Example 3: Performance of TS-1 catalyst after HEDP treatment

[0299] Pilot runs were carried out in a small-scale unit as described in Reference Example 2 to further confirm that the proposed HEDP treatment of TS-1 catalyst has no adverse effect on catalyst performance under HPPO reaction conditions. For this purpose, a dual-reactor system was used. When one reactor was loaded with fresh untreated TS-1 catalyst, the second reactor was loaded with the same catalyst, and then a 1 wt% HEDP aqueous solution was fed to the catalyst bed at a feed rate of 1 liter per hour at a temperature of 50 °C for 24 hours. After this treatment, the catalyst was washed with softened water at a feed rate of 1 liter per hour at a temperature of 50 °C for 2 hours.

[0300] After this pretreatment, in both reactors, under the standardized catalyst screening conditions as described in Reference Example 2, the conventional HPPO reaction was started in parallel. The pilot run was carried out for a period of 600 hours. The results of this screening experiment are shown in Figure 1 .

[0301] No significant performance differences were observed between the treated and untreated catalysts under these conditions during the entire pilot run, further supporting that the HEDP treatment has no negative impact on catalyst activity.

[0302] To evaluate the effect on catalyst composition and mechanical stability, samples of the treated and untreated TS-1 catalysts were analyzed after the pilot run. There was no titanium loss in the HEDP-treated catalyst compared to the untreated material.

[0303] Example 4: Evaluation of mechanical stability

[0304] Due to the potential risk associated with softening the catalyst by treating it with HEDP, subsequent laboratory tests were carried out and crush strength analysis was performed.

[0305] The treated catalyst samples were prepared using the TS-1 catalyst according to Reference Example 1. In a 20 ml glass vial, 1 g of the TS-1 sample was mixed with 10 g of water or a 1 wt% aqueous HEDP solution. Water treatment was chosen as a comparison. One set of samples was shaken for 24 hours and then allowed to stand at ambient temperature (23 °C) for 3 days. In another case, the mixture was allowed to stand for 3 days. Fresh, untreated catalyst samples and spent catalyst samples according to Reference Example 3, in which the epoxidation of Reference Example 3 had been carried out for 1044 hours, were used for reference. The catalyst had been used in 5 previous runs for a total of 3679 hours of operation and had been calcined after each previous run to restore its activity before being used for the next run.

[0306] At the end of the treatment, the samples treated with the HEDP solution were washed with deionized water. Then all the samples were dried overnight in an oven at 80 °C.

[0307] The crushing strength of 15 random particles for each treatment was measured using an Instron 5543-C7585 type load frame. The crosshead speed was set at 2 mm / min. The instrument load cell was calibrated.

[0308] The ends of the catalyst particles that were treated including shaking were significantly rounder, and there was a small amount of catalyst dust in the wide-mouth bottle, but they were otherwise intact. All the other catalyst samples visually appeared to be in good condition. There was no discernible difference in the crushing strength for any of the tested catalysts. The results are shown in Table 5.

[0309] Table 5

[0310] Subsequent study on the effect of treatment on the crush strength of the catalyst

[0311]

[0312] Example 5: Tube cleaning simulation

[0313] Further experiments were conducted to scale up the laboratory precipitation results and to find out how much catalyst had to be exposed to the washing solution and whether cycling improved the removal of the precipitate.

[0314] Example 5a: HEDP aqueous solution only in the bottom region

[0315] In an HPPO plant with a vertically arranged tubular reactor, most of the precipitate accumulates in the bottom head of the reactor and does not penetrate deeply into the tubes. Therefore, experiments were conducted using a vertically arranged tubular reactor in which an aqueous HEDP solution was introduced into the bottom head in a volume sufficient to reach only the lowest 10% of the catalyst, i.e., the catalyst was located in the bottom region of the tube. In the laboratory simulation, the first method was carried out with the "fluctuation" of the solution. A glass tube (1 / 2" inner diameter (12.7 mm)) with a coarse glass frit at the bottom was prepared. The tube was loaded with the TS-1 catalyst according to Reference Example 1 and a thin layer of the feed precipitate sample as described in Reference Example 3. The tube was dried in an 80 °C oven and then weighed. The tube was then vertically immersed in a wide-mouth bottle containing a sufficient level of 1 wt% aqueous HEDP solution to cover the catalyst when the catalyst filled the tube through the frit. The tube was lifted to drain the water and then immersed again at different time intervals to simulate the evacuation and refilling of the exchanger tubes. At the end, the tube was rinsed with 10 cm of deionized water from the top of the tube. 3 The tubes were then dried in an 80 °C oven and reweighed.

[0316] Three tubes were used for this experiment and all were immersed in the same wide-mouth bottle of 1 wt% aqueous HEDP solution. The total immersion period was 24 hours. One tube remained in the solution throughout the time, one tube was drained and refilled every 4 hours, and the last tube was drained and refilled every hour. The weights are given in Table 6. Approximately 30% of the precipitate was removed by simply allowing it to stand for 24 hours. However, renewing the HEDP solution in the tube was effective in increasing dissolution. For the tube drained every hour, the removal amount was 76 wt%.

[0317] Table 6

[0318] Results of intermittent immersion tube simulation

[0319] Tube 1 Tube 2 Tube 3 Treatment Stand still for 24 hours Drain water every 4 hours Drain water every hour Initial precipitate weight (g) 0.4913 0.4896 0.4926 Initial total tube weight (g) 28.812 28.132 28.378 Final total tube weight (g) 28.663 27.899 28.006 Weight change (g) 0.149 0.233 0.372 Weight percentage of removed precipitate 30 48 76 Number of updates 0 6 24

[0320] Visual inspection of the tubes showed that in the tubes renewed every hour, there was more downward movement of the darker insoluble precipitate particles. The frit effectively contained the particles inside the tube, so that no precipitate migrated outside the tube except for the dissolved precipitate.

[0321] Example 5b: Induced circulation

[0322] To further simplify the tube renewal, the bottom head of the exchanger was explored with nitrogen injection to simulate induced circulation. A tube with a 1” (2.54 cm) inner diameter was fabricated, which included flared “bell pieces” at either end. The bottom bell piece was used to collect the nitrogen gas supplied to the tube metered by a valve-type rotameter. The top bell piece was used to allow the gas to disengage well upon leaving. A metal screen was placed at the bottom of the straight section to support the tube contents. During the water test, it was found that the screen needed rather large holes, i.e., 3 / 32” (2.38 mm) perforations, to allow the gas to pass through it easily. To retain small TS-1 catalyst particles (1.5 mm diameter extrudates), a layer of 1 / 4” (6.350 mm) Denstone alumina balls was laid on top of the screen. Then a layer of catalyst was added, followed by a thin layer of precipitate and another layer of catalyst until the top of the straight section. The tube was dried in an 80 °C oven and then weighed. Approximately 900 ml of 1 wt% HEDP aqueous solution was added to a 1000 ml beaker. The loaded glass tube was slowly lowered into the solution with the bell pieces centered above the ends of the nitrogen tubes located at the bottom of the beaker.

[0323] Two tests were conducted with this setup. The first test involved maintaining a constant nitrogen gas flow rate over a given period. A flow rate of 0.5 scfh (0.24 l / min) was selected as an appropriate flow rate. The reason for choosing this flow rate was that during the water test, flow rates significantly greater than this caused some upward movement of the catalyst. At sufficiently high nitrogen gas flow rates (in the 2+ scfh range), small catalyst agglomerates could be ejected from the top. The movement was most pronounced when the gas flow was first started. This test ran for 19 hours. As in the batch immersion test, there was some downward migration of the precipitate. Overall, it seemed to be effective as only a small amount of precipitate was visible at the end of the test.

[0324] The second injection test is carried out with an intermittent nitrogen stream. The nitrogen stream is again 0.5 scfh (0.24 l / min). After every 5 minutes, the nitrogen stream is shut off for about 15 seconds and then restarted. This test runs for 2 hours and consists of 24 of these cycles. From visual inspection, it is obvious that there is more movement and mixing inside the tube by this method. After 15 minutes, a trace of precipitated dust migrating downward is visible in the bell on the left side. The solution is quite turbid in about 30 minutes. This is probably because of the catalyst dust washed off the catalyst (such turbidity was also observed during the water test without precipitate in the tube) and another indication of the increased turnover rate in the tube. At the end of the test, a small number of black insoluble precipitate spots are visible in the tube, but the normally soluble gray precipitate cannot be seen. The initial charge of the precipitate into the tube is 1.02 g. The tube weight change is a loss of 0.9 g. The solids settled in the beaker total 0.08 g and seem to be a combination of catalyst dust and insoluble precipitate (some light-colored particles and some dark-colored particles). If this amount is added back together with the tube contents, the precipitate solubility is 80%. Considering that the test only runs for 2 hours, this is the most effective technique attempted. Description of the Drawings

[0325] Figure 1 Shows the performance comparison of the HEDP-washed TS-1 catalyst and the untreated TS-1 catalyst.

[0326] Cited literature

[0327] -WO 2016 / 128538 A1

[0328] -WO 2015 / 010994 A1

Claims

1. A regeneration method for an epoxidation reactor, which has been used in a method for preparing an epoxidized olefin, the preparation method comprising: (i) providing an organic solvent, an olefin, an epoxidizing agent, and water to the reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone to form a reaction mixture containing the olefin, hydrogen peroxide, water, and the organic solvent; (ii) subjecting the mixture of (i) in the epoxidation zone of the reactor to epoxidation conditions in the presence of the catalyst to obtain a mixture containing water, the organic solvent, and the epoxidized olefin; (iii) removing from the reactor the mixture containing water, the organic solvent, and the epoxidized olefin obtained in (ii); whereby a precipitate is deposited in the reactor; the regeneration method comprising: (a) stopping the supply of the organic solvent, the olefin, the epoxidizing agent, and water to the reactor; (b) introducing a liquid aqueous system into the reactor, wherein the liquid aqueous system contains a chelating agent, and the chelating agent comprises a diphosphonic acid of formula (I): (OH)2(O=)P-CR 1 R 2 -P(=O)(OH)2(I), wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxy group, and C1 to C5 alkyl groups.

2. The regeneration method for the epoxidation system according to claim 1, wherein the chelating agent is the diphosphonic acid of formula (I).

3. The regeneration method of the epoxy system according to claim 1 or 2, wherein R 1 is a hydroxyl group and R 2 is a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP).

4. The regeneration method for the epoxidation reactor according to any one of claims 1 to 3, wherein the liquid aqueous system used in (b) contains a chelating agent, preferably the diphosphonic acid of formula (I), preferably HEDP, more preferably in the range of 0.01 wt% to 50 wt%, preferably in the range of 0.02 wt% to 25 wt%, more preferably in the range of 0.05 wt% to 10 wt%, based on 100 wt% of the total weight of the liquid aqueous system. Even more preferably, the chelating agent, preferably the diphosphonic acid of formula (I), more preferably HEDP, is in the range of 0.1 wt% to 5 wt%.

5. The regeneration method for the epoxidation reactor according to any one of claims 1 to 4, wherein step (b) comprises: (b.1) introducing a first portion of the liquid aqueous system containing the chelating agent into the reactor; (b.2) at least partially removing the first portion of the liquid aqueous system from the reactor; wherein step (b) preferably comprises: (b.1) introducing a first portion of the liquid aqueous system containing the chelating agent into the reactor; (b.2) at least partially removing the first portion of the liquid aqueous system from the reactor; (b.3) optionally introducing another portion of the liquid aqueous system containing the chelating agent into the reactor; (b.4) optionally at least partially removing the another portion of the liquid aqueous system from the reactor; wherein steps (b.3) and (b.4) are optionally repeated 1 to 10 times.

6. The regeneration method of an epoxidation reactor according to any one of claims 1 to 5, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out with a gaseous stream through the liquid aqueous system, and wherein the gaseous stream preferably contains at least 90% by volume, more preferably at least 95% by volume, more preferably at least 98% by volume of an inert gas based on the total volume of the gaseous stream.

7. The regeneration method of an epoxidation reactor according to any one of claims 1 to 6, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out in the reactor at a temperature in the range of 0.1 °C to the boiling point of the liquid aqueous system, preferably in the range of 0.5 °C to 90 °C, more preferably in the range of 5 °C to 50 °C, more preferably in the range of 10 °C to 40 °C.

8. The regeneration method of an epoxidation reactor according to any one of claims 1 to 7, wherein the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out in the reactor at a pressure in the range of 0.05 MPa to 5.0 MPa, preferably in the range of 0.08 MPa to 1.0 MPa, more preferably in the range of 0.1 MPa to 0.15 MPa.

9. The regeneration method of an epoxidation reactor according to any one of claims 1 to 8, wherein the reactor comprises one or more vertically arranged tubes, each tube having a specific length (height), with a bottom end and a top end, and wherein the catalyst is present between positions H1 and H2 in the tube, where H2 is higher than H1 in the tube, and the introduction of the liquid aqueous system in step (b) and / or step (b.1) and / or step (b.3) is carried out such that the liquid level in the tube is at a height within the range between H1 and H2, preferably at a height within the range of 80% to 5% below H2, more preferably at a height within the range of 70% to 10% below H2, more preferably at a height within the range of 60% to 20% below H2, more preferably at a height within the range of 50% to 25% below H2, more preferably at a height within the range of 40% to 30% below H2, each relative to the distance between H1 and H2 being 100%.

10. A combined preparation method of an olefin oxide, the combined preparation method comprising a preparation stage and a regeneration stage of the epoxidation reactor, The preparation stage comprises: (i) providing an organic solvent, an olefin, an epoxidizing agent and water to the reactor containing a heterogeneous epoxidation catalyst in an epoxidation zone so as to form a reaction mixture containing an olefin, hydrogen peroxide, water and an organic solvent; (ii) subjecting the mixture formed in (i) in the epoxidation reactor to epoxidation conditions in the presence of the catalyst, thereby obtaining a mixture containing water, the organic solvent and an olefin oxide; (iii) Remove from the reactor the mixture obtained in (ii) comprising water, the organic solvent and the epoxidizing olefin; Thereby the precipitate deposits in the reactor; The regeneration stage comprises: (a) Stop introducing the mixture of (i) into the reactor; (b) Introduce a liquid aqueous system into the reactor, wherein the liquid aqueous system comprises a chelating agent, and the chelating agent comprises a diphosphonic acid of formula (I): (OH)2(O=)P-CR 1 R 2 -P(=O)(OH)2(I), wherein R 1 and R 2 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, and a C1 to C5 alkyl group, wherein R 1 is preferably a hydroxyl group and R 2 is preferably a methyl group (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP).

11. The method for regenerating an epoxidation reactor according to any one of claims 1 to 9 or the method for preparing a combination of epoxidizing olefins according to claim 10, wherein at least three separate feed streams are provided in (i), wherein at least one feed stream is a feed provided to the reactor together with the organic solvent, wherein at least one feed stream is a feed provided to the reactor together with the olefin, and wherein at least one feed stream is a feed provided to the reactor together with the hydrogen peroxide and the water, and wherein optionally, at least one additional separate stream is provided to the reactor, and the at least one additional separate stream is a feed provided to the reactor together with an additive.

12. The method for regenerating an epoxidation reactor according to any one of claims 1 to 9 or the method for preparing a combination of epoxidizing olefins according to claim 10, wherein the organic solvent, hydrogen peroxide, water, olefin and optionally the additive are mixed before entering the reactor so as to provide a single feed stream comprising the organic solvent, hydrogen peroxide, water, olefin and optionally the additive to the reactor.

13. The method for regenerating an epoxidation reactor according to any one of claims 1 to 9 or the method for preparing a combination of epoxidizing olefins according to claim 10, wherein the epoxidation reaction conditions according to (ii) comprise fixed bed conditions, wherein preferably the organic solvent, hydrogen peroxide, water, olefin and optionally the additive are mixed before entering the reactor so as to provide a single feed stream comprising the organic solvent, hydrogen peroxide, water, olefin and optionally the additive to the reactor, or wherein the epoxidation reaction conditions according to (ii) comprise trickle bed conditions, wherein preferably the organic solvent, water and hydrogen peroxide and optionally the additive are mixed before entering the reactor and the olefin is introduced into the reactor as a separate stream.

14. The method for regenerating an epoxidation reactor according to any one of claims 1 to 9 or the method for preparing a combination of epoxidizing olefins according to claim 10, wherein steps (i), (ii) and (iii) are carried out in continuous mode or in batch mode, preferably in continuous mode.

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