DK151016B - PROCEDURE FOR THE PREPARATION OF OXIRAN COMPOUNDS BY CONVERSING AN OLEFINIC UNLAMATED COMPOUND WITH AN ORGANIC HYDROPEROXIDE IN THE PRESENT OF A CATALYST - Google Patents

Description

151016

The present invention relates to a process for preparing oxirane compounds by reacting an olefinically unsaturated compound with an organic hydroperoxide in the presence of catalyst prepared by modifying a solid inorganic oxygen compound of 5 silicon in chemical combination with at least 0.1% by weight of a oxide or hydroxide of titanium, molybdenum, vanadium, zirconium or boron.

The epoxidation of olefinically unsaturated compounds with hydroperoxide compounds proceeds according to the following general reaction scheme:

\ ^ 1 \ / ° \ I

C = C + -C-O-O-H-V C-C + -C-O-H

"I ^^ I

olefinic hydroperoxide oxirane group hydroxyl group group group

The catalysts disclosed in Danish Patent Application No. 4741/71 consist of an inorganic oxygen compound of silicon in chemical combination with a metal oxide or hydroxide which is treated before contact with an organic silylating agent. By using the solid metal-silicon oxide-type catalysts described in the above patent application, the selectivity to the desired olefin epoxides can be materially increased.

Olefinically unsaturated compounds having from 2 to 60 carbon atoms may conveniently be used for the epoxidation indicated. It is preferred to use alkenes having from 3 to 40 carbon atoms which may be optionally substituted by a hydroxyl group or a halogen atom, for example propylene, allyl alcohol and allyl chloride. The propylene is preferably used.

As hydroperoxide compounds, hydrocarbon hydroperoxides having 3-20 carbon atoms, e.g. tert.butyl hydroperoxide, tert may conveniently be used. penty I hydroperoxide and aralkyl hydroperoxides, wherein the hydroperoxy group is bonded to the carbon atom of an alkyl side chain which is directly linked to an aromatic ring, e.g. 1-phenyl-ethyl-1-hydroperoxide and 2-phenylpropyl-2-hydroperoxide (often referred to as ethylbenzene hydroperoxide and cumene hydroperoxide, respectively).

2 151016

Oxirane compounds are substances of known utility and many are chemical commodities, especially olefin oxides, for example ethylene oxide and propylene oxide. For example, propylene oxide can be converted into valuable polymer products by polymerization or copolymerization.

The hydroxyl compounds produced by this reaction can, if desired, be genome-formed to the hydroperoxide compound via subsequent dehydration, hydrogenation and oxidation.

Catalysts consisting of a solid inorganic oxygen compound of silicon in chemical combination with at least 0.1% by weight of an oxide 10 or hydroxide of titanium, molybdenum, vanadium, zirconium or boron show improved catalytic properties when treated by contact with an organic silylating agent. Advantageously, the silicon solids have an average specific surface area of at least 1 m 2 / g and preferably from 25 m 2 / g to 800 m 2 / g. Preferred silicon-containing solids contain at least 99% by weight of silica.

As a rule, the catalysts used are made from 0.2 to 50% by weight of oxides or hydroxides of titanium, vanadium, boron, molybdenum and zirconium. Very suitable are such catalysts which are prepared from 0.5 to 10% by weight of an oxide or hydroxide of 20 titanium dioxide on silica.

The catalyst materials may also contain non-interfering substances, especially those which are inert to the reactants and products, e.g., minor amounts of the alkali metals or the alkaline earth metals.

The inorganic compound being silylated may be prepared by a variety of methods which are not critical to their mode of action or effect. A particularly suitable method consists in impregnating a silicon-containing support with a suitable metal-containing solution followed by heating.

Suitable impregnating solvents are non-basic oxygen-containing hydrocarbons which are substantially inert under ordinary conditions and generally contain from 1 to 12 carbon atoms, for example, alkanols, ketones, ethers (acyclic and cyclic) and esters.

3 151016

Hydroxy or oxo-substituted hydrocarbons having 1-8 carbon atoms are preferred. Monofunctional alkanols having 1-8 carbon atoms, e.g., methanol, ethanol, isopropanol and n-butanol, are particularly preferred. Preferably, at least 80% by weight of the solvent is removed from the impregnated solid prior to calcination.

Suitable silylating agents for use in the silylation treatment described in Danish Patent Application No. 4741/71 are, for example, the organosilanes, organosilylamines and organosilazanes. Very good results are obtained using tetrasubstituted silanes having 1-3 hydrocarbon and / or halogen substituents, e.g. dichlorodimethylsilane and chlorotrimethylsilane.

It has now been found that very good results can also be obtained by using special organodisilazanes as silylating agents for metal oxide-on-silica catalysts. The use of the organodisilazanes as silylating agents for the catalyst used in the process of the present invention is advantageous since no corrosive components are formed when the metal oxide-on-silica catalyst is silylated (which is a disadvantage when using chlorosilanes). In addition, it has been found that silylation using organodisilazanes will generally take place at lower temperatures compared to silylation using organosilanes. The selectivity to epoxides formed using a catalyst silylated with disilazanes has been found to be excellent.

The invention is based on this disclosure and the process of the invention is characterized in that a catalyst is a solid inorganic oxygen compound of silicon in chemical combination with at least 0.1% by weight of an oxide or hydroxide of titanium, molybdenum, vanadium, zirconium or boron, the compound of which is treated by contact with an organic disilazane of the general formula: Si - N - Si R5 R3 ^ H \ R6.

wherein four or six of the symbols R1, R2, R3, R4, R5 and R6 represent an alkyl group of 1-4 carbon atoms, the optionally remaining two symbols each representing a hydrogen atom, at temperatures in the range of 100 to 450 ° C. , preferably in the range of 100-300 ° C, with hydration treatment optionally before the silylation treatment.

It is preferred to use a disilazane in which four or six of the symbols R1-R6 are methyl groups.

Examples of suitable disilazanes are thus 1,1,2,2-tetramethyldisilazane and 1,1,1,2,2,2-hexamethyldisilazane. However, for example, 1,1,2,2-tetraethyldisilazane can also be used. Especially preferred is hexamethyldisilazane.

Using the organodisilazanes of the above general formula, especially hexamethyldisilazane, at relatively low silylation temperatures, highly active and selective catalysts can be prepared for epoxidizing olefinic compounds with organic hydroperoxides, which is of course technically attractive. Suitable silylation temperatures are between 100 and 300 ° C, especially between 150 and 250 ° C, preferably about 200 ° C. The silylation can be performed batchwise, semi-continuously or continuously.

The silylation described in Danish Patent Application No. 4741/71 with chlorotrimethylsilane or dichlorodimethylsilane as a silylating agent is carried out at temperatures above 300 ° C, for example 325-350 ° C or more, to produce stable catalysts. It is clear from the examples in Danish Patent Application No. 4741/71 that catalysts thus treated have a long life. However, it is also seen that the effect of catalysts silylated at lower temperatures decreases rapidly.

5 151016

By using catalysts which are silylated at lower temperatures with an organodisilazane, as indicated above, at least as good hydroperoxide conversion and epoxide selectivity are obtained as with said known catalysts, and the catalysts remain much more active and selective, even after a prolonged period of time ( more than 1000 hours) than the catalysts known from the previous application, and thus the catalysts used in the process of the present invention are more stable.

In general, prior to silylation, the catalysts contain from 0.2 to 10% by weight of an oxide or hydroxide of titanium, vanadium, boron, molybdenum or zirconium, based on the total catalyst, in chemical combination with silica and / or inorganic silicate. Particularly suitable catalysts contain from 0.5 to 8% by weight of an oxide or hydroxide of titanium in chemical combination with silica.

A particularly preferred catalyst, prior to silylation, consists essentially of silica which is chemically combined with from 0.5 to 5% by weight of titanium oxide.

The catalyst materials to be silylated may contain non-interfering and / or catalysis accelerating agents. Suitable accelerating agents are, for example, the alkali metals or the alkaline earth metals in the form of oxides or hydroxides. Preferred amounts of alkali metal additives range from 0.1 to 5% by weight, based on the total amount of catalyst. A suitable catalyst to be silylated contains substantially silica in chemical combination with 0.5-5% by weight of titanium oxide and 0.01-5% by weight of calcium in the form of calcium oxide as a promoter.

The time required for the reaction of the silylating agent with the catalyst surface depends on the temperature used, generally reaction times of between 0.1 and 48 hours can be used. For organosilazanes, treatment times of 0.1-5 hours are very convenient.

The amount of silylating agent used may vary within wide limits. Silylating agent amounts of from 1 to 75% by weight, based on the entire catalyst material, are very suitable; there are preferred amounts of from 2 to 50% by weight. The silylation treatment can be repeated several times. For operational reasons, a single treatment is generally preferred.

It has been found that the best results are often obtained when the metal / silica catalyst is hydrated prior to silylation. The hydration can be carried out by contacting the catalyst with water and then heating it before silylation, or by contacting the catalyst with water vapor at elevated temperatures, especially at temperatures above 100 ° C, preferably in the range of 150 ° C. 450 ° C for 10 1 / 2-6 hours. Using organodisilazanes as a silylating agent, the best results are obtained when the hydration treatment is carried out by water vapor treatment at a temperature of 300-450 ° C for 1-6 hours.

The process according to the invention is further illustrated by the following example:

EXAMPLE

A portion of 1480 g of commercial silica gel (Davison I.D. type silica, 14-30 mesh) is contacted with a solution of 130 g of tetraisopropyl titanate and 97 g of acetylacetone in 1.25 liters of isopropanol.

The impregnated silica gel is placed in an electrically heated calcination tube and dried at a layer temperature of 500 ° C under a nitrogen atmosphere. The air is admitted and the temperature is raised to 800 ° C. This temperature is maintained for 4 hours to burn off remaining amounts of coal and to completely chemically combine the silicon dioxide and titanium dioxide, after which 1183 g of this material is rehydrated by contact with steam at 400 ° C for 3 hours. This rehydrated material is cooled to 200 ° C and then contacted with hexamethyldisilazan vapor at 200 ° C for 1 hour to give the silylated catalyst used in the process of the invention. 75 g of hexamethyldisilazane are taken up by the catalyst.

Claims (5)

The catalyst described above, as well as a similar catalyst, which, however, has not been treated with hexamethyldisilazane, is subjected to comparative experiments as catalysts for the epoxidation of olefins. In each experiment, a 1 g sample of the catalyst mass was contacted 5 with 17 g octene-1 and 28.6 g of a 12 wt% solution of ethyl benzene hydroperoxide in ethyl benzene in a 100 ml glass reactor. The reaction temperature is 100 ° C and the reaction time is 1 hour. The results are set forth in the following table: TABLE 10 Catalyst Hydroperoxidome Epoxide Selectivity Formation (%) (%) Unsilylated 95 72 Silylated 95 93 15 The data set forth in the table clearly show that the silylated catalyst has significantly higher selectivity over the desired epoxide. . A process for the preparation of oxirane compounds by reaction of an olefinically unsaturated compound with an organic hydroperoxide in the presence of a catalyst prepared by modifying a solid inorganic oxygen compound of silicon in chemical combination with at least 0.1% by weight of an oxide or a hydroxide of titanium, molybdenum, vanadium, zirconium or boron, characterized in that a catalyst is a solid inorganic oxygen compound of silicon in chemical combination with at least 0.1% by weight of an oxide or hydroxide of titanium, molybdenum, vanadium, zirconium or boron, which compound is treated by contact with an organic disilazane of the general formula: R 1 wherein four or six of the symbols R 1, R 2, R 3, R 1, R 5 and R 1 represent an alkyl group of 1-4 carbon atoms, the optionally remaining two symbols each representing a hydrogen atom, at temperatures in the range of 100 to 450 ° C, preferably in about at 100-300 ° C, with hydration treatment optionally before the silylation treatment. Method according to claim 1, characterized in that four or six of the symbols R * -R1 denote methyl groups. Process according to claim 1, characterized in that the organic disilazane is hexamethyldisilazane. Process according to any one of the preceding claims, characterized in that the amount of disilazane used in the silylation treatment is in the range of 1 to 75% by weight, based on the total catalyst material. Process according to claim 4, characterized in that the amount of disilazane used in the silylation treatment is in the range of 2 to 50% by weight, based on the total catalyst material. Process according to any one of the preceding claims, characterized in that the silylation temperature is in the range between 100 and 300 ° C, preferably 150-250 ° C.