WO1997047613A1 - Process for producing epoxides from olefines and hydrogen peroxide or hydroperoxides using a zeolithic oxidation catalyst - Google Patents

Abstract

A process for producing epoxides from olefines and hydrogen peroxide or hydroperoxides in the liquid phase using an oxidation catalyst based on titanium or vanadium silicalites with a zeolithic structure, in which the concentration of the hydrogen peroxide or hydroperoxides in the reaction mixture is in the range from 0.05 to less than 1 wt.% during the reaction.

Description

METHOD FOR PRODUCING EPOXIES FROM OLEFINES AND HYDROGEN PEROXIDES OR HYDROPEROXIDES USING A ZEOLITE OXIDAΗON CATALYST

5 Description

The present invention relates to an improved process for the production of epoxides from olefins and hydrogen peroxide or hydroperoxides using an oxidation catalyst based on titanium or vanadium silicates with a zeolite structure.

Processes for the preparation of epoxides from olefins and aqueous hydrogen peroxide using titanium silicates as epoxidation catalysts are described in EP-A 100 119 (1) and the 5 literature reference M.G. Clerici et al., J. Catal. 129, 159-167 (1991) (2).

According to (1), the epoxidation of ethylene, propene, allyl chloride, 2-butene, 1-octene, 1-tridecene, mesityl oxide, isoprene, 0 cyclooctene and cyclohexene by means of dilute aqueous hydrogen peroxide in the presence of a titanium silicalite in an autoclave ven carried out. The hydrogen peroxide concentration in the reaction mixture can be reduced by up to 10% by weight.

5 From (2) it is known that the hydrogen peroxide concentration can even be reduced by up to 1% in such epoxidations. 30 to 35% strength aqueous H ₂ 0 ₂ solutions are used as hydrogen peroxide sources for the titanium silicalite-catalyzed epoxidations of propene to propylene oxide described in (2).

However, such epoxidation processes known from the prior art have disadvantages. When using concentrated hydrogen peroxide solutions (with approx. 10 to 70% by weight H ₂ 0 ₂ ) 5, considerable safety problems in the course of the reaction can occur, in particular because of possible spontaneous decomposition of the hydrogen peroxide or its by-products (eg hydroperoxides) in the presence of certain organic solvents. The elimination of such security problems leads to considerably more effort and higher process costs. Even without the safety aspect mentioned, the process costs are already high, since medium to highly concentrated hydrogen peroxide solutions are relatively expensive.

5 The object of the present invention was therefore to provide a simple, efficient and, in particular, economical epoxidation process for olefins which no longer has the disadvantages of the prior art.

Accordingly, a process for the production of epoxides from olefins and hydrogen peroxide or hydroperoxides in the liquid phase using an oxidation catalyst based on titanium or vanadium silicates with a zeolite structure was found, which is characterized in that the concentration of the hydrogen peroxide or the hydroperoxides in the reaction - Mix in the implementation in the range of 0.05 to less

1% by weight, in particular from 0.1 to 0.8% by weight, especially from 0.2 to 0.6% by weight.

All of the organic hydroperoxides of the formula R-O-O-H used as customary oxidizing agents for such epoxidations can be used as hydroperoxides, where R generally represents an organic radical having 1 to 30 C atoms. Cumene and diisopropylbenzene hydroperoxide are of particular interest.

In a preferred embodiment, the hydrogen peroxide sources used for the epoxidation according to the invention are aqueous hydrogen peroxide solutions, in particular technical (ie not purified) hydrogen peroxide solutions with a content of 0.1 to 10% by weight, in particular 0.15 up to 5% by weight, especially 0.2 to

2% by weight of hydrogen peroxide.

Such technical hydrogen peroxide sources are particularly suitable as extraction solutions containing hydrogen peroxide from an anthraquinone working solution for the production of hydrogen peroxide.

Such technical hydrogen peroxide sources are furthermore suitable hydrogen peroxide-containing streams or residues, for example vapors or bottoms, from a hydrogen peroxide distillation, these streams or residues mostly not having been further concentrated in their H ₂ 0 ₂ content.

Such technical hydrogen peroxide sources are also particularly suitable extraction solutions containing fermenter broths or enzyme mixtures containing hydrogen peroxide, ie from naturally occurring or biotechnologically accessible sources. The oxidation catalysts based on titanium or vanadium silicates with a zeolite structure are known from the prior art. As is known, zeolites are crystalline alumino-silicates with ordered channel and cage structures, the pore openings of which are in the range of micropores which are smaller than 0.9 nm. The network of such zeolites is made up of Si0 ₄ and A10 ₄ tetrahedra, which are connected via common oxygen bridges. An overview of the known structures can be found, for example, in WM Meier and DH Olson, "Atlas of Zeolite Structure Types", Butterworth, 2nd Ed., London 1987.

Zeolites are now also known which do not contain aluminum and in which titanium (Ti) is used instead of Si (IV) in the silicate lattice. These titanium zeolites, in particular those with an MFI-type crystal structure, and possibilities for their production are described, for example in EP-A 311 983 or EP-A 405 978. In addition to silicon and titanium, such materials can also contain additional elements such as aluminum, Contain zirconium, tin, iron, cobalt, nickel, gallium, boron or small amounts of fluorine.

In the oxidation catalyst described, the titanium of the zeolite can be partially or completely replaced by vanadium. The molar ratio of titanium and / or vanadium to the sum of silicon plus titanium and / or vanadium is generally in the range from 0.01: 1 to 0.1: 1.

Titanium zeolites with an MFI structure are known to have a certain pattern when determining their X-ray diffraction images and also a framework vibration band in the

Infrared range (IR) can be identified at about 960 cm ^"1 and thus differ from alkali metal titanates or crystalline and amorphous Ti0 ₂ phases.

Typically, the titanium and also vanadium zeolites mentioned are prepared by adding an aqueous mixture of an SiO ₂ source, a titanium or vanadium source such as titanium dioxide or a corresponding vanadium oxide and a nitrogenous organic base ( "Template compound"), for example tetrapropylammonium hydroxide, optionally with the addition of alkali metal compounds, in a pressure vessel under elevated temperature over a period of several hours or a few days, the crystalline product being formed. This is filtered off, washed, dried and fired at elevated temperature to remove the organic nitrogen base. In the powder thus obtained, the titanium or the vanadium is at least partially in varying proportions within the zeolite framework with four, five or six-fold coordination. In order to improve the catalytic behavior, a repeated washing treatment with sulfuric acid hydrogen peroxide solution can follow, after which the titanium or vanadium zeolite powder must be dried and fired again; this can be followed by treatment with alkali metal compounds in order to convert the zeolite from the H form into the cation form.

Preferred titanium or vanadium zeolites are those with a pentasil zeolite structure, in particular the types with X-ray assignment to the BEA, MOR, TON, MTW, FER, MFI, MEL or MFI / MEL mixed structure. Zeolites of this type are described, for example, in W.M. Meier and D.H. Olson, "Atlas of Zeolite Structure Types", Butterworths, 2nd Ed., London 1987. Titanium-containing zeolites with the structure of ZSM-48, ZSM-12, ferrierite or β-zeolite and mordenite are also conceivable for the present invention.

In principle, the process according to the invention for the preparation of epoxides can be carried out using all customary reaction procedures and in all customary reactor types, for example using the suspension procedure or in a fixed bed arrangement. You can work continuously or discontinuously.

The epoxidation according to the invention is expediently carried out in the liquid phase in water alone or in a mixture of water and water-miscible organic solvents. Such organic solvents are particularly suitable alcohols such as methanol, ethanol, iso-propanol, tert. -Butanol or mixtures thereof. If such organic solvents are used in a mixture with water, their proportion of the total mixture is usually 5 to 95% by volume, in particular 30 to 85% by volume.

The epoxidation according to the invention is generally carried out at a temperature of from -20 to 70 ° C., in particular from -5 to 50 ° C., and at a pressure of 1 to 10 bar.

The olefin used can be any organic compound which contains at least one ethylenically unsaturated double bond. It can be aliphatic, aromatic or cycloaliphatic in nature, it can consist of a linear or a branched structure. The olefin preferably contains 2 to 30 carbon atoms. There may be more than one ethylenically unsaturated double bond, for example in dienes or trienes. The olefin can additionally contain functional groups such as halogen atoms, carboxyl groups, carboxylic ester functions, hydroxyl groups, ether bridges, sulfide bridges, carbonyl functions, cyano groups, nitro groups or amino groups.

Typical examples of such olefins are ethylene, propene, 5 1-butene, ice and trans-2-butene, 1, 3-butadiene, pentene, isoprene, hexene, octene, nonene, decene, undecene, dodecene, cyclopentene, cyclohexene, Dicyclopentadiene, methylene cyclopropane, vinyl cyclohexane, vinyl cyclohexene, allyl chloride, acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, allyl alcohol, alkyl acrylates, alkyl

10 methacrylates, oleic acid, linoleic acid, linolenic acid, esters and glycerides of such unsaturated fatty acids, styrene, α-methylstyrene, divinylbenzene, indene and stilbene. Mixtures of the olefins mentioned can also be epoxidized by the process according to the invention.

15

The process according to the invention is particularly suitable for the epoxidation of propene to propylene oxide.

According to the present invention, it is possible to successfully epoxidize olefins far below the hydrogen peroxide concentration known in the prior art by means of titanium or vanadium silicalites. Because of the low concentration of hydrogen peroxide in the system, there are no longer any safety problems. Furthermore, hydrogen peroxide solutions can be used without disturbing stabilizers, which are necessary at high concentrations. In addition, the process according to the invention has the advantage that inexpensive technical hydrogen peroxide sources can be used as feedstock; the impurities present in such sources surprisingly do not interfere with the epoxidation according to the invention.

The following examples are intended to explain the process according to the invention in more detail, without any limitation being understood thereby.

35

example 1

455 g of tetraethyl orthosilicate were placed in a four-necked flask (2 1 contents) and from a dropping funnel within

40 30 min with 15 g tetraisopropyl orthotitanate with stirring

(250 rpm, blade stirrer) added. A colorless, clear mixture was formed. Finally, 800 g was added to one

20 wt. -% tetrapropylammonium hydroxide solution (alkali content

<10 ppm) and stirred for another hour. Was at 90 to 100 ° C

45 distilled off the alcohol mixture formed from the hydrolysis (approx. 450 g). It was filled with 1.5 l of deionized water and placed the now slightly opaque sol in a 2.5 liter stirred autoclave made of stainless steel.

The sealed autoclave (anchor stirrer, 200 rpm) was brought to a reaction temperature of 175 ° C. at a heating rate of 3 ° / min. The reaction was complete after 92 hours. The cooled reaction mixture (white suspension) was centrifuged off and washed neutral with water several times. The solid obtained was dried at 110 ° C. in the course of 24 hours (weight 149 g).

Finally, the template still remaining in the zeolite was burned off in air at 550 ° C. in 5 hours (loss of calcination: 14% by weight).

According to wet chemical analysis, the pure white product had a Ti content of 1.5% by weight and a residual alkali content below 100 ppm. The yield on Si0 _{2 used} was 97%. The crystallites had a size of 0.05 to 0.25 μm and the product showed a typical band at approx. 960 cm ¹ in the IR.

Example 2

45 ml of methanol and 0.5 g of titanium silicate powder from Example 1 were introduced into a 250 ml glass autoclave and the suspension was stirred with a magnetic stirrer. The sealed glass autoclave was then cooled to -30 ° C. and 20.7 g of propene were pressed on. The glass autoclave was then heated to 0 ° C. and 23 g of 0.5 wt. -% hydrogen peroxide solution was added. The reaction mixture was stirred at 0 ° C. under autogenous pressure for 5 h. The catalyst was then centrifuged off and the propylene oxide content was determined by gas chromatography. The propylene oxide content was 0.3% by weight.

Example 3

45 ml of methanol and 0.5 g of titanium silicalite from Example 1 were introduced into a 250 ml glass autoclave and the suspension was stirred with a magnetic stirrer. The sealed glass autoclave was then cooled to -30 ° C. and 20.2 g of propene were pressed on. The glass autoclave was then heated to 0 ° C. and 23 g of 0.5 wt. -% hydrogen peroxide solution metered. The reaction mixture was stirred at 0 ° C. under autogenous pressure for 30 minutes. The catalyst was then centrifuged off and the content of propylene oxide was determined by gas chromatography. The propylene oxide content was 0.18% by weight.

Claims

claims 1. A process for the preparation of epoxides from olefins and hydrogen peroxide or hydroperoxides in the liquid phase using an oxidation catalyst based on titanium or vanadium silicates with a zeolite structure, characterized in that the concentration of the hydrogen peroxide or the hydroperoxides in the reaction mixture during the settlement is in the range from 0.05 to less than 1% by weight. 2. The method according to claim 1, characterized in that aqueous hydrogen peroxide solutions containing 0.1 to 10% by weight of hydrogen peroxide are used as the hydrogen peroxide sources for the epoxidation. 3. The method according to claim 2, characterized in that hydrogen peroxide sources used hydrogen peroxide-containing extraction solutions from an anthraquinone working solution for the production of hydrogen peroxide. 4. The method according to claim 2, characterized in that hydrogen peroxide sources are used as hydrogen peroxide sources or residues from a hydrogen peroxide distillation. 5. The method according to claim 2, characterized in that hydrogen peroxide sources used hydrogen peroxide-containing extraction solutions from fermenter broths or from enzyme-containing mixtures. 6. A process for the preparation of propylene oxide from propene and hydrogen peroxide or hydroperoxides according to claims 1 to 5.