MXPA96003165A - Improved epoxidation process - Google Patents

Abstract

In an epoxidation process wherein an olefin is reacted with hydrogen peroxide in the presence of a titanium-containing molecular sieve catalyst and a salt, the tendency of the catalyst to produce greater quantities of oxygen as it ages due to non-selective decomposition of the hydrogen peroxide may be counteracted by the addition of a chelating agent bearing hydroxyl, carboxyl, amino, and/or phosphoryl groups. The use of such a chelating agent enables selectivity to epoxide to be maintained at a desirably high level for a prolonged period of time in a continuous epoxidation unit.

Description

IMPROVED EPOXIDATION PROCESS FIELD OF THE INVENTION This invention relates to methods by means of which the efficiency of an olefin epoxidation reaction can be increased. In particular, the invention relates to an epoxidation process wherein a chelating agent is used to eliminate or suppress the non-selective decomposition of hydrogen peroxide to oxygen.

BACKGROUND OF THE INVENTION It is well known that the epoxidation of olefinic compounds with hydrogen peroxide can be catalyzed effectively by certain synthetic zeolites containing titanium atoms (see, for example, U.S. Patent No. 4,833,260). While the selectivity towards the desired epoxide is generally high, U.S. Patent No. 4,824,976, proposes that the non-selective ring-opening reactions that take place when the epoxidation is carried out in a protic medium, such as water or alcohol, it can be suppressed or eliminated by treating the catalyst, before the reaction or during the reaction, with an acid neutralizing agent. It is said that the neutralizing agent neutralizes the acid groups, on the surface of the catalyst, which tend to Pl 'j / ßM / promote the formation of by-products. The neutralization, according to the patent, can be carried out with water-soluble basic substances selected from strong bases such as NaOH and KOH and weak bases such as NH4OH, a2CC > 3, NaHCC > 3, Na2HPC > 4 and analogous salts of potassium and lithium, including K2C0, Li2C03, KHCO3, LiHC03, and K2HP04, alkaline and / or alkaline earth salts of carboxylic acids having from 1 to 10 carbon atoms and alkali and / or alkaline earth alcoholates having 1 to 10 carbon atoms. Co-pending United States Application Serial No. 08 / 396,319, filed on February 28, 1995, discloses that by performing titanium silicalite-catalyzed epoxidation in the presence of low concentrations of a non-basic salt (ie, a neutral or acid salt) the selectivity of epoxidation can be improved, unexpectedly, significantly, by reducing the amount of open ring by-products that are formed. We have now found that while the ring opening of the epoxide can be removed or effectively suppressed by epoxidation in the presence of a suitable source of ammonium, alkali metal or alkaline earth metal cations, regardless of whether it is basic, neutral or acid, the non-selective decomposition of peroxide P1 05 / 9OMX hydrogen in oxygen and water tends to increase gradually as the titanium silicalite catalyst ages. For example, when titanium silicalite is used in a continuous fixed-bed system to epoxide propylene in the presence of a cation source, such as ammonium hydroxide, the selectivity for the desired propylene oxide product decreases over time as the oxygen selectivity increases in a range of about 8 to 15%. The mechanism responsible for this loss in epoxide selectivity is not well understood. However, it would be very desirable to find a means of attenuating the effects of aging on the performance of the catalyst, such that the epoxide ring opening and the hydrogen peroxide decomposition are eliminated or suppressed simultaneously to maximize the yield of the catalyst. epoxide obtained during the life of a particular catalyst load.

SUMMARY OF THE INVENTION Currently and unexpectedly we have discovered that the tendency of a molecular sieve catalyst containing titanium to gradually deteriorate its performance (measured by the non-selective decomposition of hydrogen peroxide in Pl .'05 / qoM? oxygen), when used in an olefin epoxidation reaction together with a source of cations, it can be improved by effecting the epoxidation in the presence of a chelating agent, sas a compound having two or more groups selected from the group consisting of amino, hydroxyl, carboxyl, phosphoryl and combinations thereof. In one embodiment of the invention, the chelating agent is used in anionic (deprotonated) form with the salt generated which functions as a source of the ammonium, alkali metal or alkaline earth metal cation. The present invention thus provides a method for epoxidizing an olefin, comprising the reaction of the olefin with hydrogen peroxide in liquid phase, within a reaction zone, in the presence of: a molecular sieve catalyst containing titanium, - a salt comprising an anionic species and a cation selected from the group consisting of ammonium cations, alkali metal cations and alkaline earth metal cations; and an effective amount of chelating agent to reduce the non-selective decomposition of hydrogen peroxide to molecular oxygen as the catalyst ages.

DETAILED DESCRIPTION OF THE INVENTION Hydrogen peroxide (H202) used as an oxidant in the present invention can be obtained from any suitable source, including, for example, the autoxidation of secondary alcohols using air or another source of molecular oxygen. Suitable secondary alcohols include both aliphatic alcohols, such as isopropanol and cyclohexanol, as well as aromatic alcohols, such as alpha methylbenzyl alcohol and anthrahydroquinone (including alkyl-substituted anthrahydroquinones). The crude product of the reaction generated in this form can be used either directly in the epoxidation process of this invention or, if desired, purified, fractionated, concentrated, ion exchanged, or processed in some other way before said use. For example, the ketone generated as a co-product of auto-oxidation can be separated, totally or partially, from hydrogen peroxide by distillation (since the ketone is relatively volatile) or by extraction with water (since the ketone is substantially immiscible or insoluble). in water). Hydrogen peroxide can, alternatively, be generated in situ, for example, by combining oxygen, secondary alcohol, olefin, a titanium-containing molecular sieve catalyst, a chelating agent, and salt, within a reaction zone subject to effective to carry out the simultaneous autoxidation of the secondary alcohol and the olefin epoxidation. Speaking in Pl O 'lnM - in general, it will be desirable to use initial concentrations of hydrogen peroxide of from about 0.5 to 20 weight percent in the liquid phase within the reaction zone. The ethylenically unsaturated and epoxidized substrate in the process of this invention is preferably an organic compound having from two to ten carbon atoms and at least one ethylenically unsaturated functional group (ie, a carbon-carbon double bond) and can be a aliphatic, cyclic, branched or straight-chain olefin. More than one carbon-carbon double bond can be present in the olefin; in this way substrates can be used with dienes, trienes and other polyunsaturated substrates. Examples of suitable olefins for use in the process of this invention include: ethylene, propylene, butenes, butadiene, pentenes, isoprene, 1-hexene, 3-hexene, 1-heptene, 1-octene, diisobutylene, 1-nonene , the trimers and tetramers of propylene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclooctadiene, dicyclopentadiene, methylenecyclopropane, methylenecyclopentane, methylenecyclohexane, vinylcyclohexane and vinyl cyclohexene. Mixtures of olefins can be epoxidized and the resulting mixture of epoxides can be used either in Pl. ' 05/9? IMX form mixed or separated in the different epoxy components. The process of this invention is especially useful for the epoxidation of C-C olefins or having the general structure R1 R < \ / c I "1 / \ R2 R4 where R1, R2, R ^, and R4, are the same or different and are selected from the group consisting of hydrogen and C ^ -Cg alkyl (selected such that the total number carbon atoms in the olefin does not exceed 10.) The process of this invention is also suitable for use in the epoxidation of olefins containing functional groups in addition to the aliphatic hydrocarbyl entities.For example, the carbon-carbon double bond can be substituted with groups such as -C0H, -C0R, -CN, or -OR, wherein R is an alkyl, cycloalkyl, aryl or aralkyl substituent The radicals R1, R2, R3, and R4, in the structural formula shown above, they may contain aryl, aralkyl, halo, nitro, sulphonic, cyano, carbonyls (eg, ketone, aldehyde), hydroxyl, carboxyl (eg, ester, acid) or ether groups Examples of olefins of these types include allyl alcohol, Pl, 05 / 9oMX styrene, allyl chloride, allyl methyl ether, allyl phenyl ether, methyl methacrylate, acrylic acid, methyl acrylate, stilbene and the like. The amount of hydrogen peroxide related to the amount of olefin is not critical but, more conveniently, the mole ratio of olefin: hydrogen peroxide ranges from about 100: 1 to 1:10 when the olefin contains an ethylenically unsaturated group . The molar ratio of the ethylenically unsaturated groups in the olefin to the hydrogen peroxide is preferably in the range of 1: 2 to 10: 1. The titanium-containing molecular meshes useful as catalysts in the epoxidation step of the process comprises the class of zeolitic substances wherein the titanium is replaced by a portion of the silicon atoms in the network structure of a molecular mesh. These substances are well known in the art. Particularly preferred catalysts include the; classes of reagent moleeulaies commonly referred to as "TS-1" (which have an MFI topology analogous to that of aluminosilicate zeolites ZSM-5), "TS-2" (which have a ME topology analogous to that of zeolites of aluminosilicate ZSM-11), and "TS-3" (as per Fl 'ür > / 9nMX describes in Belgian Patent No. 1,001,038). Also suitable for use are molecular meshes containing titanium and having structures isomorphic to zeolite beta. The titanium catalyst preferably does not contain non-oxygenated elements other than titanium and silica in the network structure, although smaller amounts of boron, iron, aluminum and the like may be present. Suitable titanium-containing molecular sieve catalysts for use in the process of this invention will generally have a composition corresponding to the following empirical formula xTi02: (l-x) Si02, where x is between 0.0001 and 0.500. More preferably, the value of x varies from 0.01 to 0.125. The molar ratio of Si: Ti in the structure of the molecular mesh network in advantageous form varies from 9.5: 1 to 99: 1 (more preferably from 9.5: 1 to 60: 1). The use of catalysts relatively rich in titanium may also be desirable. The amount of catalyst used is not critical, but it must be sufficient to substantially complete the desired epoxidation reaction in a short period of time in a practicable manner. The optimal amount of catalyst will depend on several factors including reaction temperature, reactivity and Pl. N 'inMX concentration of the olefin, the concentration of hydrogen peroxide, types and concentration of organic solvent, as well as the activity of the catalyst and the type of reactor or reaction system used (eg, batch versus continuous). For example, in a batch or pulp reaction, the amount of catalyst will usually vary from 0.001 to 10 grams per mole of olefin. In a fixed or packed bed system, the optimum amount of catalyst will be influenced by the flow of reagents through the fixed bed, - normally, from about 0.05 to 2.0 kilograms of hydrogen peroxide per kilogram of catalyst per hour will be used. The concentration of titanium in the reaction mixture in liquid phase will generally be from about 10 to 10,000 ppm. The catalyst can be used in the form of powder, granulate, microspherical, extruded, monolithic or any other suitable physical form. The use of a binder (co-gel) or support in combination with the molecular mesh containing titanium can be advantageous. Supported or agglutinated catalysts can be prepared by methods known in the art to be effective for zeolite catalysts in general. Preferably, the binder or support is essentially not acidic and does not catalyze the non-selective decomposition of hydrogen peroxide or ring opening of the epoxide.

Pl. ' < ) '> / < Illustrative binders and carriers include titania, silica, alumina, silica-alumina, silica-titania, silica-toria, silica-magnesia, silica-zirconia, silica-berilia, and ternary compositions of silica with other refractory oxides. Also useful are clays such as montmorillonites, kaolins, bentonites, haloisites, dickites, nacrites, and ananxites. The ratio of molecular sieve to binder or support can vary from 99: 1 to 1:99, but preferably are from 5:95 to 80:20. A critical feature of the process of this invention is the presence of a salt. While the precise mechanism by which process improvements are effected is unknown, it is believed that the salt interacts favorably with the titanium-containing molecular sieve catalyst to suppress or eliminate undesirable side reactions such as the opening of the catalyst. epoxide ring and oxidation of the solvent. In one embodiment, the catalyst is pretreated (i.e., prior to epoxidation) with the salt. A suitable pretreatment method includes forming a catalyst pulp in a dilute solution of the salt in a suitable solvent for the salt, such as water and / or alcohol, and stirring the pulp at a temperature of from 20 ° C to 100 ° C during an effective time to incorporate enough salt l'l O 'o.M in the pores of the molecular mesh. After which the catalyst is separated from the pulp by suitable means such as filtration, centrifugation or decantation, it is washed if desired, and subsequently optionally the residual solvent is dried. In another pretreatment method, a catalyst as synthesized is impregnated with a solution of the salt and then calcined. However, in a preferred embodiment, the salt is introduced into the reaction zone separately from the catalyst during epoxidation. For example, the salt can be suitably dissolved in the feed oxygen peroxide, which normally also contains a solvent such as water, alcohol and / or ketone. In a continuous process, the concentration of salt in the feed entering the reaction zone can be adjusted periodically, as desired or necessary, in order to optimize the epoxidation results achieved. For example, it may be advantageous to use a constant salt concentration, to introduce the salt at intermittent intervals, or to increase or decrease the salt concentration over time. A salt is a compound formed when the proton of an acid is replaced by a metal cation or its equivalent (for example, NH4 +). Salts suitable for the purpose of this invention include those Pl. n './' H.MX substances comprising an anion and a cation, wherein the cation is preferably selected from ammonium (NH4), alkali metals (especially Li, Na, K), alkaline earth metals. The salt can be acidic, neutral or basic. Preferred anions include, without limitation, the following: halides (especially Cl and Br), nitrate (NO3) and sulfate (S04). Other anions such as carboxylates (e.g., formate, acetate), carbonates (e.g., carbonate, bicarbonate), hydroxide, alkoxides and the like can also be used. Exemplary non-basic salts suitable for use include: lithium chloride, lithium bromide, sodium chloride, sodium bromide, lithium nitrate, sodium nitrate, potassium nitrate, lithium sulfate, sodium sulfate, potassium sulfate, lithium, magnesium, calcium, barium and ammonium acetate (and other non-basic salts of carboxylic acids, especially carboxylic acids C? _c?) diacid ammonium phosphate, sodium diacid phosphate, potassium diacid phosphate, and monoacid pyrophosphate sodium. Basic salts include: sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, sodium bicarbonate, sodium dibasic phosphate, tribasic sodium phosphate, and potassium analogue salts and, if necessary, limitation. of lithium. From p] OVInM advantageous mixtures or combinations of salts can be used. Preferably, the salt is soluble in the liquid phase of the epoxidation reaction mixture (which is usually comprised of hydrogen peroxide, solvent and olefin). The process of this invention also requires a chelating agent containing a plurality of donor atoms (e.g., 0, N, S) that can be combined by coordinate bonding with a single metal atom to form a cyclic structure called a chelation complex. (what side) . The chelating agent may be of organic or inorganic character and preferably per molecule has at least two oxygen-containing functional groups, wherein the functional groups are desirably selected from the group consisting of hydroxyl, carboxyl, phosphoryl or combinations thereof . In this way, the chelating agent can be of bidentate, tridentate, tetradentate or multidentate character. Functional groups may be in protonated form or deprotonated 0 II. For example, "carboxyl" includes -COH O group as well as -C ~ group, "hydroxyl" includes -OH groups as well as -0"groups, and" phosphoryl "includes groups F'l.Ob ioMX 0 0 0 II II II -P-OH, -P-0"and -P-0". Preferably, at least 1 I OH OH OH 0" A carboxyl group or a phosphoryl group is present. The functional groups are advantageously located in the chelating agent, in such a way that the atoms capable of coordinating with a single metal ion are separated by between 3 and 7 atoms; the atoms involved can be phosphorus, carbon and the like. Nitrogen-containing functional groups, such as tertiary amino groups, capable of coordinating with metal ions may also be present in the chelating agent. Specific illustrative polyfunctional chelating agents include polyphosphonic acids (eg, aminotrimethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid, hydroxyethylidene diphosphonic acid), polyphosphoric acids (Hn + zpn? 30 + l 'where n> 1, including pyrophosphoric acid, triphosphoric acid, and metaphosphoric acid, as well as, organophosphoric acids such as phytic acid), hydroxycarboxylic acids (eg, malic acid, gluconic acid, hydroxyethylenediamine triacetic acid, N, N-bis (2-hydroxyethyl) glycine, tartaric acid, citric acid), acids aminocarboxylics (for example, acid l.'O'i / ibHX ethylenediamine tetraacetic acid, ethylenediamine-di-o-hydroxy phenyl acetic acid, 1,2-diamino cyclohexane tetraacetic acid, nitrilotriacetic acid), polyamines (e.g., triethylene tetramine, triaminotriethylamine, ethylenediamine), polycarboxylic acids (for example, diglycolic acid) aminoalcohols (for example triethanolamine), as well as alkali metal, alkaline earth metal and ammonium salts thereof. When the chelating agent is used in deprotonated form it can, advantageously, function simultaneously as the ionic species in the salt. That is, the salt may be an alkali metal, alkaline earth metal or ammonium salt of a chelating agent as defined herein. These species can be introduced directly into the reaction zone or alternatively formed in situ by the combination of the chelating agent in protonated form and a base such as a • alkali metal or ammonium hydroxide. The chelating agent in this embodiment may be partially or totally deprotonated. To avoid an undesirable decrease in the conversion rate of hydrogen peroxide, the concentration of the salt in the liquid phase within the reaction zone should generally not be greater than 0.02 M. Below 0.00001 M, an improvement is generally not observed Pl '(>', / 'IDMX in the epoxide selectivity The optimum salt concentration will vary depending on various factors including, for example, the chemical identity of the salt, the temperature, the solvent, the space velocity and the like , but can be easily determined by routine experimentation Generally speaking, the level of the salt in the liquid phase epoxidation reaction mixture is maintained in a desirable form from about 1 to 1000 ppm.The amount of chelating agent present within the The liquid phase of the reaction zone is selected to effectively reduce the non-selective decomposition of hydrogen peroxide to molecular oxygen during the aging of the titanium-containing molecular sieve catalyst, compared to the generation level of 02 that would result in the absence of the chelating agent, the optimal amount of the chelating agent will vary depending on the parameters Chemical properties of the salt and the agent selected for use as well as the epoxidation conditions, but can be easily determined by routine experimentation. Normally, the chelating agent is used at a concentration of from about 1 to 1000 ppm in the liquid phase of the reaction mixture. The epoxidation reaction temperature PJ.'ÜS ibMX preferably ranges from 0 ° C to 100 ° C (more preferably 20 ° C to 80 ° C), which has been found to be sufficient to effect the selective conversion of the olefin to epoxide, within a reasonably short period of time, with a minimum of non-selective decomposition of hydrogen peroxide. It is generally advantageous to carry out the reaction in order to achieve a conversion of hydrogen peroxide as high as possible, preferably at least 50%, more preferably at least 90%, and more preferably at least 99%, consistent and with reasonable selectivities. The optimum reaction temperature will be influenced by the concentration and activity of the catalyst, the reactivity of the substrate, the reagent concentrations and the type of solvent used, among other factors. Reaction or residence times ranging from approximately 10 minutes to 48 hours will normally be appropriate, depending on the variables identified above. The reaction is preferably carried out at atmospheric pressure or at an elevated pressure (normally between 1 and 100 atmospheres). Generally, it will be desirable to keep the reaction components as a liquid mixture. For example, when an olefin such as propylene having a boiling point at atmospheric pressure that is less than the epoxidation temperature is used, a higher than atmospheric pressure is preferably used to maintain the desired concentration of propylene in the liquid phase. The epoxidation process of this invention can be batchwise, continuously or semicontinuously using any suitable type of reaction vessel or apparatus, such as a fixed bed, transported bed, stirred pulp or CSTR reactor. It will generally also be suitable to use the known methods for conducting metal catalyzed epoxidations using hydrogen peroxide. In this way, the reagents can be combined all at once or sequentially. For example, hydrogen peroxide and / or olefin can be added in an increase to the reaction zone. The epoxidation can be carried out in the presence of a suitable solvent in order to dissolve or disperse the reactants and facilitate the control of the temperature. Suitable solvents include, but are not limited to, the following: water, alcohols (especially aliphatic alcohols C)C C C o such as methanol and isopropanol), ketones (especially C ^-C? G ketones such as acetone), and mixtures of these solvents. Once the epoxidation has been carried out to the desired degree of conversion, the epoxide product can be separated and recovered from the reaction mixture.

I 1 'OS / XiiM using any suitable technique such as fractional distillation, extractive distillation, liquid-liquid extraction, crystallization, or the like. After separation of the epoxidation reaction mixture by any suitable method such as filtration (as when using for example a pulp reactor), the recovered titanium-containing molecular sieve catalyst can be reused economically in subsequent epoxidations. When the catalyst is exhausted in the form of a fixed bed, the epoxidation product extracted as a stream from the epoxidation zone will be free of catalyst and the catalyst will be retained within the epoxidation zone. Similarly, any amount of olefin or unreacted hydrogen peroxide can be separated and recycled or otherwise disposed of. In certain embodiments of the present process, when the epoxide is produced on a continuous basis it may be desirable to periodically or constantly regenerate all or a portion of the catalyst used, in order to maintain optimum activity and selectivity. Suitable regeneration techniques are well known and include, for example, calcination and solvent treatment. Regeneration may also include retreatment or reimpregnation with salt. From the above description, any ?? . nr, 'i?, M experienced in the art can easily determine the essential characteristics of this invention and, without deviating from the spirit and scope thereof, can make various changes and modifications in it to adapt it to various uses, conditions and modalities.

EXAMPLES To demonstrate the benefits and advantages of the claimed process, a series of continuous epoxidation runs of propylene was performed using a rotating basket CSTR, wherein the catalyst comprised an extruded catalyst containing 50% titanium silicalite TS-1. The conditions of the runs were, in each case, 60 ° C (140 ° F), 1.38 MPa gauge (200 psig), and a hourly space velocity in weight of 0.2 Ib H202 / lb. / catalyst / hour. The base feed contained 2.5% by weight of H202, 75% by weight of isopropanol, 24% by weight of water, 0.2% by weight of methanol, 0.29% by weight of acetic acid, and 0.1% by weight of formic acid. To the base feed were added varying amounts of ammonium hydroxide and, in the runs illustrating the present invention, "Dequest 2000" ATMP (aminotrimethylene phosphonic acid) was added. The results obtained are in Table 1 Pl O.VóMX TABLE I Example No. lI33 22 33 4 5 6 NH40H in Food, ppm 7788 7788 234 234 234 234 ATMP in Food, ppm 0 0 1 12200 0 90 120 240 Catalyst in the Current, r 350 455 230 630 510 590 Rust Selectivity 77 77 84 86 85 85 Propylene2,% Selectivity to Oxygen2,% 5.0 2.5 4.0 2.5 2.5 3.0 Selectivity2 to ROP1,% 13 14 6 6 7 7 Conversion of H 0,% 78 75 79 69 70 70 1ROP = propylene oxide ring opening products = monopropylene glycol + propylene glycol isopropyl ether + the addition product of hydrogen peroxide and propylene oxide. 2based on hydrogen peroxide. 3 comparative example.

Comparative examples 1 and 3, in which the ammonium hydroxide but not the ATMP were present in the epoxidation feed, indicated that as the concentration of ammonium hydroxide increases, the amount of undesirable open-ring products produced (according to suggested by United States Patent No. 4,824,976), the catalyst tends to generate relatively high levels of 02 (from the non-selective decomposition of H202) as it ages. However, the 120 ppm co-feed of the ATMP chelating agent with the ammonium hydroxide in Example 2 significantly reduces the selectivity to 02 even though the catalyst had been in use much longer than in Example 1 (455 hours against 350 hours). Similarly, in Examples 4-6 under prolonged continuous reaction conditions, oxygen production was effectively suppressed or eliminated when the chelating agent was used together with ammonium hydroxide in the feed. Surprisingly, the chelating agent, although acidic in nature, did not interfere with the beneficial effect of ammonium hydroxide (a basic substance) on the side reactions of propylene oxide.

F 1 '0', / hMY

Claims (20)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A method for the epoxidation of an olefin characterized in that it comprises reacting the olefin with : hydrogen peroxide in liquid phase, within a reaction zone, in the presence of a titanium-containing molecular mesh catalyst; a salt comprising an anionic species and a cation selected from the group of ammonium cations, alkali metal cations and alkaline earth metal cations; and an effective amount of chelating agent to reduce the non-selective decomposition of hydrogen peroxide to molecular oxygen during aging of the titanium-containing molecular sieve catalyst.
2. 2. A method according to claim 1, characterized in that the chelating agent has per molecule at least two functional groups, the functional groups are selected from amino, hydroxyl, carboxyl, phosphoryl, and combinations thereof.
3. 3. A method according to claim 1 or 2, characterized in that the salt is basic, neutral or acidic.
4. 4. A method according to any of the I 1 p './' l MX preceding claims, characterized in that the chelating agent is selected from polyphosphonic acids, polyphosphoric acids, hydroxycarboxylic acids, polycarboxylic acids, aminocarboxylic acids, polyamides and alkali metal, alkaline earth metal and ammonium salts of the same.
5. 5. A method according to claim 4, characterized in that the chelating agent is aminotrimethylene phosphonic acid.
6. 6. A method according to any of the preceding claims, characterized in that the anionic species are selected from halides, phosphates, sulfates, carbonates, carboxylates, hydroxide, alkoxides, and nitrate.
7. 7. A method according to any of the preceding claims, characterized in that the reaction is carried out at a temperature of from 0 ° C to 100 ° C.
8. 8. A method according to any of the preceding claims, characterized in that the reaction is carried out at a temperature of from 20 ° C to 80 ° C.
9. 9. A method according to any of the preceding claims, characterized in that the hydrogen peroxide is obtained by oxidation of [j tlS / 'ínM-isopropanol.
10. A method according to any of the preceding claims, characterized in that the liquid phase is comprised of a solvent selected from the group consisting of water, C? -Cig alcohols, C3-C? -ketones and mixtures thereof.
11. 11- A method according to any of the preceding claims, characterized in that the titanium-containing molecular sieve catalyst has an MFI, MEL or zeolite beta topology.
12. 12. A method according to any of the preceding claims, characterized in that the olefin is an aliphatic olefin of C2-C? G- 13.
13. A method according to claim 12, characterized in that the aliphatic olefin C2 ~ c10 is propylene.
14. A method according to any of the preceding claims, characterized in that the titanium-containing molecular sieve catalyst has a composition corresponding to the chemical formula axTi02: (l-x) Si02 wherein x is from 0.01 to 0.125.
15. 15. A method according to any of the preceding claims, when carried out continuously.
16. 16. A method according to any of the , / • < M preceding claims, characterized in that the titanium-containing molecular sieve catalyst is exhausted in the reaction zone in the form of a fixed bed or in the form of a pulp in the liquid phase.
17. 17. A method according to any of the preceding claims, characterized in that the salt is present in a concentration from 0.00001M to 0.02M in the liquid phase.
18. 18. A method according to any of claims 1 to 17, characterized in that the salt is present at a concentration of 1 to 1000 ppm in the liquid phase.
19. 19. A method according to any of the preceding claims, characterized in that the polyfunctional chelating agent is present in a concentration of from 1 to 1000 ppm in the liquid phase. A method according to any of the preceding claims, characterized in that the salt and chelating agent combination is replaced by a salt comprising a chelating agent in deprotonated form. Pl I TI M