EP1318989A1

EP1318989A1 - Method for producing an epoxide

Info

Publication number: EP1318989A1
Application number: EP01978346A
Authority: EP
Inventors: Joaquim Henrique Teles; Alwin Rehfinger; Ulrich Müller; Anne Berg; Peter Rudolf; Wolfgang Harder; Norbert Rieber; Peter Bassler
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-09-11
Filing date: 2001-09-06
Publication date: 2003-06-18
Also published as: WO2002020503A1; DE10044787A1; CA2421866A1; ZA200301925B; US20030187284A1; AU2002210490A1; MXPA03002010A; CN1494534A

Abstract

The invention relates to a method for producing an epoxide in the presence of a zeolite catalyst, whereby (i) an alkene is reacted with a hydroperoxide in the presence of the catalyst in order to obtain the epoxide, and at least one alkali metal salt is supplied to the reaction in at least one educt flow. The inventive method is characterised in that (ii) the supply of the at least one alkali metal salt is cut off during the reaction, and the supply of hydroperoxide and alkene is continued.

Description

Process for the preparation of an epoxide

The present invention relates to a process for the preparation of an epoxide by reacting an alkene with hydroperoxide in the presence of a zeolite catalyst, the reaction being carried out with alkali metal salt in at least one educt stream. The ner driving is characterized in that the alkali metal salt supply is stopped after a certain time, but the supply of hydroperoxide and alkene is continued. The present invention also relates to an integrated ner process for producing an epoxide in which the zeolite catalyst is regenerated and used again for the reaction.

It is known from the prior art that the addition of an alkali metal salt or more alkali metal salts for the reaction, in which an epoxide is prepared from alkene and hydroperoxide, influences the selectivity of the catalyst, in the presence of which the reaction takes place and which comprises at least one titanium zeolite, and leads to better selectivities with regard to epoxidation.

EP-A 0 712 852 discloses that a non-basic salt is used to improve the selectivity of a titanium silicalite catalyst which is used for the epoxidation of olefinic compounds by means of hydrogen peroxide.

EP-B 0 230 949 discloses a ner process for the epoxidation of olefinic ner bonds by means of hydrogen peroxide, in which the selectivity of the catalysts used, synthetic zeolites, is improved by adding compounds which adhere to the acid groups before or during the reaction neutralize the catalyst surface.

EP-A 0757043 describes a process for the preparation of epoxides from olefins and hydrogen peroxide in the presence of a zeolite containing titanium atoms. then as a catalyst in which neutral or acidic salts are added to the catalyst before or during the reaction.

DE-A 199 36 547.4 describes a process in which, in order to influence the pH, the alkali metal salt is added to the reaction medium in which the reaction of alkene with hydroperoxide takes place in the presence of a heterogeneous catalyst, and at the same time the reaction temperature and, if appropriate, the pressure, under to which the reaction is carried out.

In processes in which an epoxide is prepared from an alkene and a hydroperoxide in the presence of a catalyst comprising a titanium zeolite, the activity and / or the selectivity of the catalyst generally decreases with the progress of the reaction. In order to take account of the procedural economic requirements, it is generally desirable to regenerate the catalyst after it has unacceptable values in terms of activity and / or selectivity. It is known that catalysts which comprise a titanium zeolite can be regenerated by, for example, burning off with oxygen or gas mixtures comprising oxygen, as is described, for example, in WO 98/55228.

When combining the methods of adding alkali metal salt and burning off with oxygen or a gas mixture comprising oxygen, however, the effect occurs that when the catalyst comprising a titanium zeolite is brought into contact with alkali metal salts, an ion exchange takes place and the catalyst is loaded with a certain amount of A] ___ alimetal. When the catalyst loaded in this way is regenerated, however, at the required temperatures, thermodynamically very stable alkali metal titanates are formed, which reduce the catalytic activity of the catalyst with regard to the epoxidation reaction for which the regenerated catalyst is to be used again. Another disadvantage is that this alkali metal titanate formation is irreversible, so that when the catalyst is regenerated several times, the maximum activity of the catalyst steadily decreases. An object of the present invention was therefore to provide a simple process which makes it possible to add alkali metal salt to the reaction medium during the reaction and at the same time to avoid the undesired formation of alkali metal titanate.

The present invention therefore relates to a process for the preparation of an epoxide in the presence of a zeolite catalyst in which

(i) an alkene is reacted with a hydroperoxide in the presence of the catalyst to give the epoxide, at least one alkali metal salt being fed to the reaction in at least one reactant stream, characterized in that

(ii) in the course of the reaction, the addition of the at least one alkali metal salt is stopped and hydroperoxide and alkene are fed to the reaction. The hydroperoxide is preferably hydrogen peroxide.

Surprisingly, it was found that at least one acid is formed in the epoxidation reaction and this acid, which actually arises as an undesirable by-product, can be used to remove from the catalyst the alkali metal with which the catalyst has been loaded to a certain extent.

It is known from the prior art that a zeolite catalyst, which is used, inter alia, for the production of an epoxide starting from hydroperoxide and olefin, can be washed with an acid. For example, WO 98/55228 proposes washing the catalyst with a solvent such as, for example, an acid such as formic acid, acetic acid or propionic acid, before contacting it with an oxygen-containing gas mixture. There, however, it is explicitly described that this washing process serves to remove valuable product and organic deposits adhering to the catalyst. Another significant difference from the preferred embodiment of the process according to the invention is that WO 98/55228 as acid, which is used for washing is set, not the acid that is formed in the reaction, but rather acid is supplied from the outside in at least one separate step.

Examples of acids which are formed when the alkene is reacted with a hydroperoxide in the presence of the zeolite catalyst, which preferably comprises at least one titanium zeolite, are formic acid and acetic acid.

Depending on the solvent or solvent mixture used for the reaction, acids can also be formed under the reaction conditions chosen for the epoxidation. For example, if methanol is used as the solvent, formic acid is formed during the reaction. If another alcoholic component is used as a solvent or as a constituent of the solvent, other organic acids can also be formed.

Alkali metal salts include, above all, lithium, sodium, potassium and cesium salts. The anions of these salts include, for example, halides such as chloride and bromide, nitrate, sulfate or hydroxide, and the anions of acids containing phosphorus, arsenic, antimony and tin, e.g. Phosphate, hydrogen phosphate, dihydrogen phosphate, arsenate and stannate. Other anions such as perchlorate, formate, acetate, hydrogen carbonate or carbonate are also conceivable.

Examples include lithium chloride, lithium bromide, sodium bromide, lithium nitrate, sodium nitrate, potassium nitrate, lithium sulfate, sodium sulfate, potassium sulfate, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, lithium carbonate, potassium hydrogen carbonate, sodium pyrophosphate, potassium hydrogen phosphate, potassium phosphate phosphate and called disodium hydrogen phosphate and diceium hydrogen phosphate. Also to be mentioned are lithium, sodium or potassium carboxylates of carbon acids, in particular carboxylic acids with 1 to 10 carbon atoms, and lithium, sodium or potassium alcoholates of alcohols with 1 to 10 carbon atoms. Other examples include sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium dihydrogen pyrophosphate, potassium and sodium phosphate. Dipotassium hydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate and sodium acetate are particularly preferably used.

In principle, all methods of how the alkali metal salt is fed into the reaction are conceivable as long as it is ensured that the feed of the alkali metal salt is stopped and alkene and hydroperoxide are further fed to the reaction.

In general, it is possible to add the alkali metal salt to the reaction in a separate stream. To implement step (ii), the supply of this stream is simply interrupted for conversion. The alkali metal salt is preferably fed to the reaction in solution, an aqueous solvent mixture being particularly preferably used for this purpose. In addition to water, this solvent mixture mainly uses solvents which are also used for the reaction of alkene with hydroperoxide.

It is also possible to feed the alkali metal salt together with the hydroperoxide, together with the alkene or with the solvent, ie as a mixture with the solvent, to the reaction by alkali metal salt, optionally dissolved in a, preferably aqueous, solvent mixture, the hydroperoxide stream or is fed to the alkene stream before it is fed to the reaction. Alkali metal salt can also be added to both the alkene and hydroperoxide streams. The alkali metal salt is preferably added to the circulating solvent after it has been separated from the reaction mixture for the preparation of the epoxide, and is thus fed to the reaction. The alkali metal salt is more preferably added to the feed stream, ie the mixture of hydrperoxide, alkene and solvent, in particular a mixture of aqueous hydrogen peroxide, propene and methanol. Alternatively, the alkali metal salt can be fed to the reaction in a mixture with the hydroperoxide, preferably an aqueous hydrogen peroxide solution.

If two or more different alkenes are fed into the reaction in two or more feed streams, which is also encompassed by the process according to the invention, the alkali metal salt can be added to one or more of these streams before this or these are fed to the reaction.

Likewise, two or more different alkali metal salts can also be fed to the reaction in one or more streams, preferably as stated above. The term “different alkali metal salts” denotes salts which differ either in terms of the cations or the anions or both the cations and the anions. If two or more alkali metal salt streams are used, these in turn can differ in terms of the solvent or solvent mixture used.

The period of time during which alkali metal salt is also added to the reaction in addition to alkene and hydroperoxide can essentially be chosen as desired and can be adapted to the requirements of the reaction.

The same applies to the period of time during which the alkene and hydroperoxide are reacted without the addition of alkali metal salt. Generally, this time period is in the range of less than ten days, preferably less than one day.

The proportions between the supplied alkali metal to hydroperoxide or alkene are selected as follows: Alkene to hydroperoxide, especially propene to H ₂ O ₂ :

0.8 to 20, preferably 0.9 to 5 and in particular 0.95 to 2 mol mol.

Alkali metal to hydroperoxide: <1000, preferably <500 and in particular 100-400, in each case μmol MVmol hydroperoxide, where M * stands for an alkali metal cation.

After the alkene has been reacted with hydroperoxide and the feed has been switched off, the catalyst is washed for a certain time with a dilute solution of an acid. It is possible to use both those acids which have already formed in the reaction of alkene with hydroperoxide and which were used in (ii) to remove alkali metal from the catalyst. Any other inorganic or organic acid or an acid mixture with a pKa of less than 6 in water is also suitable. Examples of such acids are, for example, carboxylic acids such as formic acid, acetic acid, propionic acid, inorganic oxo acids such as sulfuric acid, nitric acid, phosphoric acid , Hydrogen halide (e.g. HC1, HBr) or sulfonic acids (e.g. pTosSO ₃ H, CH ₃ SO ₃ H).

The solvent or solvent mixture in which the reaction of alkene and hydroperoxide was carried out is preferably used as the solvent for the acid or acids. Such solvents include

Water,

Alcohols, preferably lower alcohols, more preferably alcohols with less than 6 carbon atoms, such as, for example, methanol, ethanol, propanols,

Butanols, pentanols, again more preferably methanol,

Diols or polyols, preferably those with fewer than 6 carbon atoms, Ethers such as diethyl ether, tetrahydrofuran, dioxane, 1,2-diethoxyethane, 2-methoxyethanol,

Esters such as methyl acetate or butyrolactone,

Amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone,

Ketones such as acetone,

Nitriles such as acetonitrile or mixtures of two or more of the aforementioned compounds.

Methanol is particularly preferably used as the solvent in which the reaction of the alkene with hydroperoxide, preferably hydrogen peroxide, is carried out. Accordingly, methanol is also preferably used as a solvent for the acid or the acid mixture with a pKa value of less than 6 in water, with one also improving ^" the solubility of the acid or acids with a pKa value of less than 6 water or several further solvent components can be added to the methanol, water being mentioned in particular.

The present invention therefore also relates to a method as described above, characterized in that

(iii) the addition of alkene and hydroperoxide is stopped and the catalyst is washed with a solution comprising at least one acid with a pKa in water of less than 6.

The time period during which the catalyst is rinsed with the acid solution is generally in the range from less than ten days, in particular 30 minutes to 4 hours, and can be matched to the time during which the catalyst tor has already been brought into contact with acid during the ongoing reaction according to (ii).

Depending on the procedure, the catalyst can be used in powder form as a suspension or packed in a fixed bed. If the catalyst was used in the suspension mode, it is first separated from the reaction solution in one or more separation steps, such as filtration or centrifugation, before rinsing with the acid solution. In the regeneration of the catalyst which was used packed in a fixed bed, washing with the acid solution is preferably carried out in the conversion device itself, the catalyst not having to be removed or installed, so that it is not subject to any additional stress.

In principle, the alkene can be reacted with hydroperoxide by any suitable method.

Among other things, it is possible to remove hydroperoxide in an intermediate separation from the reaction discharge from a first reaction stage and to react it again with alkene in a second reaction stage. Such methods are described, for example, in PCT / EP99 / 05740 and DE-A 100 15 246.5. One-step processes without intermediate separation are also possible.

With regard to the continuous process introduction used with particular preference in the present process, all suitable reactor arrangements are conceivable. For example, the epoxy can be produced in a cascade from two or more reactors that are connected in series. Methods are also conceivable in which reactors arranged in parallel are used. Combinations of these methods are also possible. In the event that two or more reactors are connected in series, between the reactors suitable intermediate treatments can also be carried out. In this context, reference is made, inter alia, to PCT / EP99 / 05740 and DE-A 100 15 246.5, which are fully incorporated by reference into the context of the present application with regard to reactor arrangement and intermediate treatment. Tube or tube bundle reactors are particularly preferred as reactors.

Furthermore, the temperature and pressure of the reaction medium can be changed during the production of the epoxide from alkene and hydroperoxide during the process. The pH value and the temperature of the reaction medium can also be changed. In this regard, the change in the pH value relates to changes by adding one or more compounds which differ from the alkali metal salts added to the reaction according to the invention in (i). It is also possible to change the pressure at which the reaction takes place in addition to the pH and temperature of the reaction medium. In this regard, reference is made to DE-A 199 36 547.4, which is hereby incorporated in its entirety by reference into the context of the present application.

The mixture which results from the production of the epoxide from alkene and hydroperoxide can be worked up in the process according to the invention in accordance with all suitable processes. With regard to a preferred embodiment of the process according to the invention, in which propene is reacted with hydrogen peroxide in the presence of methanol as solvent to form propylene oxide, a mixture which contains methanol, water and unreacted hydrogen peroxide is preferably removed from the reaction mixture after the propene has been reacted separated and this mixture subjected to a separation process, which results in a further mixture containing methanol and methyl formate. With regard to this method and further possible work-up steps and also possible procedures, reference is made to DE-A 100 32 884.7 and DE-A 100 32 885.9, which refer to this are fully incorporated into the context of the present application by reference.

In a preferred embodiment of the process according to the invention, the catalyst which has been washed in accordance with (iii) with a solution comprising at least one acid with a pKa in water of less than 6 is then washed with a solvent or a solvent mixture to which no acid is added was rinsed.

Therefore, the present invention also relates to a method as described above, characterized in that

(iv) the catalyst resulting from (iii) is washed with at least one solvent.

Likewise, the catalyst can be rinsed with a solvent or a solvent mixture to which no acid has been added both before and after rinsing with the solution comprising at least one acid with a pKa in water of less than 6.

The solvents listed above can be used as solvents, and mixtures of two or more of these solvents can also be used. Methanol, water or mixtures thereof are preferably used for washing.

Among other things, the catalyst is preferably washed with solvent at a temperature in the range from 40 to 200 ° C., optionally under pressure in a range from <40 bar. The solvent or the solvent mixture can be separated off from the catalyst by any suitable method. If, in a preferred embodiment, the catalyst is washed in the reaction device, as described above, the solvent is preferably first let out of the reaction device. The solvent or the solvent mixture is preferably removed from one or more inert gases by treatment with one or more streams. The temperatures are preferably in a range from -50 to 250 ° C. Inert gases include nitrogen, carbon dioxide, argon, hydrogen, synthesis gas, methane, ethane and natural gas. Nitrogen is preferably used. The inert gas loaded with solvent is either disposed of thermally or worked up to recover the solvent contained therein.

In a particularly preferred embodiment of the process according to the invention, the washing with solvent is carried out under pressure at a temperature above the boiling point of the solvent and, after the solvent has been discharged, the pressure is reduced to such an extent that part of the solvent already evaporates due to the latent heat of the reactor before or during the start of the supply of gas for drying. Both a gas and a liquid can be used for the jacket-side heat transfer of the conversion device. It is preferred to use a liquid for a temperature range below 150 ° C. and a gas for the temperature range above 150 ° C.

After the solvent or the solvent mixture has been separated off from the catalyst or after the solvent or the solvent mixture in which one or more acids having a pKa value of less than 6 are dissolved in the catalyst, in a further preferred process the catalyst is reacted with oxygen or in contact with a gas mixture comprising oxygen. Accordingly, the present invention also relates to a method as described above, characterized in that

(v) the catalyst resulting from (iii) or (iv) is brought into contact with oxygen or a gas mixture comprising oxygen.

The following processes can be used for this regeneration step:

1. A method which comprises heating a spent catalyst at a temperature less than 400 ° C but higher than 150 ° C in the presence of molecular oxygen for a period of time sufficient to increase the activity of the spent catalyst, such as it is described in EP-A 0 743 094;

2. a method that heating a spent catalyst at a temperature of 150 ° C to 700 ° C in the presence of a gas stream containing at most 5% by volume of molecular oxygen for a period of time sufficient for the activity of the spent Improving catalyst comprises, as described in EP-A 0 790 075;

3. a process in which a spent catalyst by heating at 400 to 500 ° C in the presence of an oxygen-containing gas or by washing with a solvent, preferably at a temperature which is 5 ° C to 150 ° C higher than that during the Reaction temperature used is treated as described in JP-A 3 11 45 36;

4. a process in which a spent catalyst is treated by calcining at 50 ° C. in air or by washing with solvents, where the activity of the catalyst is restored, as described in “Proc. 7 * Intern. Zeolite Conf. 1986 (Tokyo) ";

5. A process for the regeneration of a catalyst which comprises the following stages (A) and (B):

(A) heating an at least partially deactivated catalyst to a temperature in the range from 250 ° C. to 600 ° C. in an atmosphere which contains less than 2% by volume of oxygen, and

(B) loading the catalyst at a temperature in the range of 250 to 800 ° C, preferably 350 to 600 ° C, with a gas stream containing an oxygen-supplying substance or oxygen or a mixture of two or more thereof in the Has a range from 0.1 to 4% by volume,

the process also comprising the further stages (C) and (D)

(C) loading the catalyst at a temperature in the range of 250 to 800 ° C, preferably 350 to 600 ° C, with a gas stream containing an oxygen-supplying substance or oxygen or a mixture of two or more thereof in the range of more than 4 to 100% by volume,

(D) cooling the regenerated catalyst obtained in step (C) in an inert gas stream containing up to 20% by volume of a liquid vapor selected from the group consisting of water, an alcohol, an aldehyde, a ketone, an ether, an acid , an ester, a Nitrile, a hydrocarbon and a mixture of two or more thereof,

may include. Details regarding this process can be found in DE-A 197 23 949.8;

6. A process in which a spent catalyst is regenerated by thermal treatment under a gas stream at temperatures of at least 130 ° C such that the mass-related residence time of the gas stream over the catalyst, as defined therein, does not exceed 2 hours. Details regarding this method can be found in WO 98/18556.

Of course, the methods described above can also be combined with one another in a suitable manner.

If necessary, the catalyst for regeneration could additionally be washed with at least one hydroperoxide solution or with one or more oxidizing acids before or according to the methods described above. Of course, the methods described above can also be combined with one another in a suitable manner.

After cooling to generally temperatures below 200 ° C., the catalyst regenerated in this way can be conditioned, if necessary, for renewed use in the reaction of alkene with hydroperoxide in order to remove the heat of sorption of the solvent or the starting materials in a controlled manner. This is possible using all conceivable methods. In the case of the catalysts packed as a fixed bed, small amounts of a solvent are preferably admixed with the inert gas flowing past the catalyst, and the inert gas stream which is solvent vapor is passed through the catalyst bed. The preferred solvent tel used that which is used for the implementation and / or the laundry, as described above. Methanol is very particularly preferred. The solvent content and the volume flow of the inert gas are preferably selected so that no impermissible peak temperature (hot spot) occurs on the catalyst.

The temperature increase should preferably not be more than 100 ° C. above the average temperature of the heat exchanger in the jacket space. After the release of heat has subsided, the supply of inert gas and solvent vapor is interrupted and the catalyst bed is filled with liquid and put back into operation.

In a particularly preferred embodiment, the catalyst regenerated according to the process of the invention is reused for the reaction of alkene with hydroperoxide.

Therefore, the present invention also relates to an integrated process for the preparation of an epoxide, comprising steps (i), (ii), (iiϊ), (v) and optionally (iv) as described above, characterized in that (vi) the the catalyst resulting from (v) is used to react the alkene with hydroperoxide according to (i).

There are no particular restrictions with regard to the zeolite catalysts regenerated in the context of the present process.

Zeolites are known to be crystalline aluminosilicates with ordered channel and kg structures that have micropores that are preferably smaller than approximately 0.9 nm. The network of such zeolites is made up of SiO ₄ - and AlO ₄ - Tetrahedra connected by common oxygen bridges. An overview of the known structures can be found, for example, in WM Meier, DH Olson and Ch. Baerlocher, "Atlas of Zeolite Structure Types", Elsevier, 4th edition, London 1996.

Zeolites are now also known which contain no aluminum and in which titanium (Ti) is partly substituted for Si (IV) in the silicate lattice. These titanium zeolites, in particular those with a MFI-type crystal structure, and possibilities for their production are described, for example in EP-A 0 311 983 or EP-A 405 978. In addition to silicon and titanium, such materials can also contain additional elements such as, for example, As aluminum, zirconium, tin, iron, cobalt, nickel, gallium, boron or a small amount of fluorine. In the zeolite catalysts which are preferably regenerated using the Ner process according to the invention, the titanium of the zeolite can be partially or completely replaced by vanadium, zirconium, chromium or Νiobium or a mixture of two or more thereof. The molar ratio of titanium and / or vanadium, zirconium, chromium or Νiob to the sum of silicon and titanium and / or vanadium and / or zirconium, and / or chromium and / or Νiobium is generally in the range from 0.01: 1 up to 0.1: 1.

Titanium zeolites, in particular those with an MFI-type crystal ricture, and possibilities for their production are described, for example, in WO 98/55228, WO 98/03394, WO 98/03395, EP-A 0 311 983 or EP-A 0 405 978 described, the scope of which is fully included in the context of the present application.

Titanium zeolites with an MFI structure are known to be identified by a certain pattern in the determination of their X-ray diffraction measurements and additionally by a framework vibration band in the infrared range (TOR.) At about 960 cm ^" and are thus different from alkali metal titanates or crystalline and amorphous TiO ₂ -Differentiate phases. Zeolites with pentasil-zeolite structure containing titanium, germanium, tellurium, vanadium, chromium, niobium and zirconium, in particular the types with X-ray assignment to ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ATN , ATO, ATS, ATT, ATV, AWO, AWW, BEA, BIK, BOG, BPH, BRE, CAN, CAS, CFI, CGF, CGS, CHA -, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESN, EUO, FAU, FER, GIS, GME, GOO, HEU, IFR, ISN, ITE, JBW, KFI, LAU, LEN, LIO, LOS, LOV , LTA, LTL, LTΝ, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MOΝ, MOR, MSO, MTF, MTΝ, MTT, MTW -, MWW-, ΝAT-, ΝES-, ΝOΝ-, OFF-, OSI-, PAR-, PAU-, PHI-, RHO-, RON-, RSN-, RTE-, RTH-, RUT-, SAO-, SAT, SBE, SBS, SBT, SFF, SGT, SOD, STF, STI, STT, TER, THO, TON, TSC, VET, VFI, VNI , VSV, HOW, WEN, YUG, ZON structure and mixed structures of two or he called more of the above structures. Titanium-containing zeolites with the structure of ITQ-4, SSZ-24, TTM-1, UTD-1, CIT-1 or CIT-5 are also conceivable for use in the process according to the invention. Further titanium-containing zeolites are those with the structure of ZSM-48 or ZSM-12.

Ti zeolites with an MFI, MEL or MFIvMEL mixed structure are to be regarded as particularly preferred for the process according to the invention. In particular, the Ti-containing zeolite catalysts, which are generally referred to as “TS-1”, “TS-2”, “TS-3”, and Ti zeolites with an isomorphic structure to β-zeolite are further preferred to call.

Accordingly, the present invention also relates to a process as described above, characterized in that the catalyst is a titanium silicalite having the structure TS-1. The term “alkene”, as used in the context of the present invention, is understood to mean all compounds which have at least one CC double bond.

The following alkenes are mentioned as examples of such organic compounds with at least one C-C double bond:

Ethene, propene, 1-butene, 2-butene, isobutene, butadiene, pentene, piperylene, hexene, hexadiene, heptene, octene, diisobutene, trimethylpentene, nonene, dodecene, tridecene, tetra- to eicosene, tri- and tetrapropene, polybutadienes, Polyisobutenes, isoprene, terpenes, geraniol, linalool, linalyl acetate, methylene cyclopropane, cyclopentene, cyclohexene, norbornene, cycloheptene, vinylcyclohexane, vinyloxirane, vinylcyclohexene, styrene, cyclooctene, cyclooctadiene, vinylnorbomen, dienes, methylodododoladienadieno, cyclodentylbenzene dienodolododoladienol, cyclodentene Stilbene, diphenylbutadiene, vitamin A, beta-carotene, vinylidene fluoride, allyl halides, crotyl chloride, methallyl chloride, dichlorobutene, allyl alcohol, methallyl alcohol, butenols, butenediols, cyclopentenediols, pentenols, octadienols, tridecenols, ethylenated unsaturated ethoxylates, unsaturated carboxylates, such as unsaturated carboxylic acid, such as unsaturated carboxylates, such as unsaturated carboxylates, Acrylic acid, methacrylic acid, crotonic acid, maleic acid, vinyl acetic acid, unsaturated fatty acids such as e.g. Oleic acid, linoleic acid, palmitic acid, naturally occurring fats and oils.

Alkenes containing 2 to 8 carbon atoms are preferably used in the process according to the invention. Ethene, propene and butene are particularly preferred. Propene is particularly preferably reacted.

Accordingly, the present invention also relates to a process as described above or an integrated process as described above, characterized in that the alkene is propene. The hydroperoxides used according to the invention can be obtained by all processes known to the person skilled in the art. To produce the hydrogen peroxide that is preferably used, the anthraquinone process can be used, for example, according to which practically the entire amount of the hydrogen peroxide produced worldwide is produced. This process is based on the catalytic hydrogenation of an anti__rachinon compound to the corresponding anthrahydroquinone compound, subsequent reaction of the same with oxygen to form hydrogen peroxide and subsequent separation of the hydrogen peroxide formed by extraction. The catalytic cycle is closed by renewed hydrogenation of the re-formed anthraquinone compound.

"Ullmanns Encyclopedia of Industrial Chemistry", 5th edition, volume 13, pages 447 to 456 provides an overview of the antirachinone process.

It is also conceivable to convert sulfuric acid to hydrogen peroxide by anodic oxidation with simultaneous cathodic hydrogen evolution into peroxodisulfuric acid. The hydrolysis of the peroxodisulfuric acid then leads via the peroxosulfuric acid to hydrogen peroxide and sulfuric acid, which is thus recovered.

It is of course also possible to display hydrogen peroxide from the elements.

Before using hydrogen peroxide in the process according to the invention, it is possible, for example, to free a commercially available hydrogen peroxide solution from unwanted ions. Among other things, methods are conceivable, such as those described in WO 98/54086, in DE-A 42 22 109 or in WO 92/06918. Likewise, at least one salt contained in the hydrogen peroxide solution can be removed from the hydrogen peroxide solution by means of ion exchange by means of a device, is characterized in that the device has at least one non-acidic ion exchange bed with a flow ^{cross-sectional area} F and a height H, the height H of the ion exchange ^{bed being} less than or equal to 2.5 • F ^lß and in particular less than or equal to 1.5 • F ^1/2 is. In principle, all non-acidic ion exchanger beds with a cation exchanger and / or anion exchanger can be used within the scope of the present invention. Cation and anion exchangers can also be used as so-called mixed beds within an ion exchange bed. In a preferred embodiment of the present invention, only one type of non-acidic ion exchanger is used. It is further preferred to use a basic ion exchanger, particularly preferably that of a basic anion exchanger and further particularly preferably that of a weakly basic anion exchanger.

The present invention also relates to the use of an acid with a pKa value in water of less than 6 for removing alkali metal from a zeolite catalyst.

The present invention also relates to a process for the regeneration of a zeolite catalyst which comprises: (a) washing a zeolite catalyst used in a process according to any one of claims 1 to 8 with a solution comprising at least one acid with a pKa value in water of less than 6, the acid being formed in the reaction of alkene and hydroperoxide, (b) washing the catalyst resulting from (a) with methanol and

(c) contacting the catalyst resulting from (b) with oxygen or a gas mixture comprising oxygen. The invention is explained in more detail in the following examples.

Examples:

example 1

Epoxidation with dipotassium hydrogen phosphate as base (Nergleichsbeispiel)

The epoxidation of propylene with hydrogen peroxide was carried out in a tubular jacket provided with a cooling jacket and 45 mm in diameter and 2 m in length, which was treated with approx. 620 g of a fresh epoxidation catalyst (titanium silicalite TS-1 in the form of strands with a diameter of 1.5 mm and alkali metal content <200 ppm) was filled. The feed quantities of the individual educts were as follows:

Methanol: 1834 g / h

Hydrogen peroxide (40% in water): 332 g / h propene: 244 g / h

K ₂ HPO ₄ solution (1.25% by weight in water): 4 g / h

The individual starting materials were brought together under pressure (approx. 20 bar) in front of the reactor and passed through the reactor. The temperature of the cooling medium in the jacket space was chosen so that the hydrogen peroxide conversion at the reactor outlet was approximately 90% (the temperature was in the range between 25 and 45 ° C., depending on the degree of deactivation of the catalyst). The reaction was stopped after 300 hours, the catalyst was washed free of propylene oxide with methanol at room temperature and then dried at 40 ° C. in a stream of nitrogen. After removal, the catalyst was analyzed for its potassium content. The potassium concentrations in the dry catalyst were: At the reactor inlet: 1400 ppm by weight

In the middle of the reactor: 1000 ppm by weight

At the reactor outlet: 800 ppm by weight

The organic carbon content was 1.1% by weight. The removed catalyst was then heated in a muffle furnace with circulating air at 550 ° C. for 2 hours in order to remove the organic deposits by burning off. After burning, the organic carbon content was <0.1% by weight. The catalyst (minus about 5 g which was used for the analyzes) was refilled into the reactor and the reaction was continued for a further 300 hours. A slight decrease in catalyst activity was evident from the approximately 2 ° C higher temperature (compared to the first run) that was required to achieve the same hydrogen peroxide conversion. After the second run, the catalyst was washed again, dried and analyzed for potassium. The concentrations were:

At the reactor inlet: 1500 ppm by weight

In the middle of the reactor: 1100 ppm by weight

At the reactor outlet: 900 ppm by weight.

Example 2

Epoxidation with sodium pyrophosphate as base (comparative example)

Example 1 was repeated, but instead of the dipotassium hydrogen phosphate solution, a 1.25% by weight solution of sodium pyrophosphate (Na P ₂ O, 2 g / h) was used as the base. The first reaction was also stopped after 300 hours, the catalyst was washed free of propylene oxide at room temperature with methanol and then dried at 40 ° C. in a stream of nitrogen. After removal, the catalyst was analyzed for its sodium content. The sodium concentration in the dry catalyst was:

At the reactor inlet: 700 ppm by weight

In the middle of the reactor: 500 ppm by weight

At the reactor outlet: 400 ppm by weight.

The organic carbon content was 1.3% by weight. After the regeneration (analogous to example 1; after burning off, the organic carbon content was <0.1% by weight), the catalyst was used again for 300 hours, again with a slightly lower activity than in the first run , After washing and drying, the catalyst was analyzed for its sodium content. The sodium concentrations in the dry catalyst were:

At the reactor inlet: 800 ppm by weight In the middle of the reactor: 600 ppm by weight

At the reactor outlet: 400 ppm by weight.

Example 3

Epoxidation with diceium hydrogen phosphate as base (comparative example) Example 1 was repeated, but instead of the dipotassium hydrogen phosphate solution, a 2.5% by weight solution of dicesium hydrogen phosphate (Cs ₂ HPO ₄ , 3.6 g / h, prepared in solution from Cs CO ₃ and phosphoric acid) was used as the base.

The first reaction was also stopped after 300 hours, the catalyst was washed free of propylene oxide at room temperature with methanol and then dried at 40 ° C. in a stream of nitrogen. After removal, the catalyst was analyzed for its cesium content. The cesium concentrations in the dry catalyst were:

At the reactor inlet: 4400 ppm by weight

In the middle of the reactor: 2800 ppm by weight

At the reactor outlet: 2100 ppm by weight.

The organic carbon content was 2.4% by weight. After the regeneration (analogous to Example 1; after burning off, the organic carbon content was <0.1% by weight), the catalyst was used again for 300 hours, with a loss of activity compared to the first run being found (for the same turnover was required in the second run at a temperature which was about 3 ° C higher than in the first run). After washing and drying, the catalyst was analyzed for its cesium content. The cesium concentrations in the dry catalyst were.

At the reactor inlet: 4600 ppm by weight In the middle of the reactor: 3100 ppm by weight

At the reactor outlet: 2300 ppm by weight Example 4

Epoxidation with dipotassium hydrogen phosphate as base (according to the invention)

The first run of Example 1 was repeated. After the 300 hours, the propylene, hydrogen peroxide and dipotassium hydrogenphosphate feeds were shut off and rinsed with methanol for 1 hour. Then about 2 g / h of formic acid were metered into the running methanol stream. The catalyst was washed with this ~ 0.1% by weight solution for 1 hour. The acid metering was then switched off and washed with methanol for a further 1 hour. After the methanol had been discharged, the catalyst was dried in a stream of nitrogen as in Example 1. The potassium levels were as follows:

At the reactor inlet: <100 ppm by weight

In the middle of the reactor: - <100 ppm by weight At the reactor outlet: 100 ppm by weight

The organic carbon content was 0.9% by weight. The removed catalyst was then heated in a muffle furnace with circulating air at 550 ° C. for 2 hours in order to remove the organic deposits by burning off. After burning, the organic carbon content was <0.1% by weight. The catalyst (minus about 5 g which was used for the analyzes) was refilled into the reactor and the reaction was continued for a further 300 hours. There was no decrease in activity compared to the first run.

Example 5

Epoxidation with sodium pyrophosphate as base (according to the invention) The first run of Example 2 was repeated. The sodium pyrophosphate dosage was stopped ten hours before the end of the experiment. After the 300 hours, the propylene and hydrogen peroxide feeds were then shut off and rinsed with methanol for 3 hours. After the methanol had been discharged, the catalyst was dried in a stream of nitrogen as in Example 1. The sodium content was as follows:

At the reactor inlet: 200 ppm by weight

In the middle of the reactor: 200 ppm by weight. At the reactor outlet: 100 ppm by weight.

The organic carbon content was 1.3% by weight. The removed catalyst was then heated in a muffle furnace with circulating air at 550 ° C. for 2 hours in order to remove the organic deposits by burning off. After burning, the organic carbon content was <0.1% by weight. The catalyst (minus about 5 g which was used for the analyzes) was refilled into the reactor and the reaction was continued for a further 300 hours. There was no decrease in activity compared to the first run.

Example 6

Epoxidation with diceium hydrogen phosphate as base (according to the invention)

The first run of Example 3 was repeated. After the 300 hours, the propylene, hydrogen peroxide and diceium hydrogenphosphate feeds were shut off and rinsed with methanol for 1 hour. Then about 2 g / h of phosphoric acid were metered into the running methanol stream. The catalyst was washed with this -0.1% by weight solution for 1 hour. The sauce was then Redosing stopped and washed with methanol for 1 hour. After the methanol had been discharged, the catalyst was dried in a stream of nitrogen as in Example 1. The cesium content was as follows:

At the reactor inlet: 100 ppm by weight

In the middle of the reactor: 200 ppm by weight

At the reactor outlet: 200 ppm by weight.

The organic carbon content was 2.0% by weight. The removed catalyst was then heated in a muffle furnace with circulating air at 550 ° C for 2 hours to remove the organic deposits by burning. After burning, the organic carbon content was <0.1% by weight. The ^• Catalyst (g minus about 5 that were used for the analyzes) was re-introduced into the reactor and the reaction further 300 hours, dangerous situations. It was no decrease in activity are observed in comparison with the first run.

Claims

claims

1. A process for the preparation of an epoxide in the presence of a zeolite catalyst, in which (i) an alkene is reacted with a hydroperoxide in the presence of the catalyst to give the epoxide, at least one alkali metal salt being fed to the reaction in at least one educt stream, characterized in that that

(ii) in the course of the reaction, the addition of the at least one alkali metal salt is stopped and hydroperoxide and alkene are fed to the reaction.

2. The method according to claim 1, characterized in that

3. The method according to claim 2, characterized in that

(iv) the catalyst resulting from (iii) is washed with at least one solvent.

4. The method according to claim 2 or 3, characterized in that (v) the catalyst resulting from (iii) or (iv) is brought into contact with oxygen or a gas mixture comprising oxygen.

5. Integrated method for producing an epoxide, comprising steps (i), (ii), (iii), (v) and optionally (iv) according to claims 1 to 4, characterized in that

(vi) the catalyst resulting from (v) is used to react the alkene with hydroperoxide according to (i).

6. The method according to any one of claims 1 to 5, characterized in that the catalyst is a titanium silicalite of the structure TS-1.

7. The method according to any one of claims 1 to 6, characterized in that the alkene is propene.

8. The method according to any one of claims 1 to 7, characterized in that the hydroperoxide is hydrogen peroxide.

9. Use of an acid with a pKa in water of less than 6 for removing alkali metal from a zeolite catalyst.

10. A method of regenerating a zeolite catalyst comprising: (a) washing a zeolite catalyst used in a process according to any one of claims 1 to 8 with a solution comprising at least one acid with a pKa in Water of less than 6, the acid being formed in the reaction of alkene and hydroperoxide, (b) washing the catalyst resulting from (a) with methanol and

(c) contacting the catalyst resulting from (b) with oxygen or a gas mixture comprising oxygen.