DK150593B - METHOD FOR PREPARING METAL / SILICONE-OXID TYPE SOLID CATALYST - Google Patents

Description

150593

The present invention relates to a process for producing a solid metal / silicon oxide-type catalyst, i.e. a catalyst containing an inorganic oxygen compound of silicon and a metal oxide or hydroxide, for use in the preparation of oxirane compounds by reacting an olefinically unsaturated compound with an organic hydroperoxide. The epoxidation of olefinically unsaturated compounds with hydroperoxide compounds takes place according to the following general reaction scheme:

I ^ / ° \ ^ I

C = C + -C-O-O-H - »_C-C. ^ + -C-OH

I I

olefinic hydroperoxide oxirane group hydroxyl group group group

The catalysts disclosed in Danish patent application no.

4741/71, consists of an inorganic oxygen compound of silicon and 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. pentyl hydroperoxide and aralkyl hydroperoxides, wherein the hydroperoxy group is bonded to the carbon atom of an alkyl side chain linked directly to an aromatic ring, e.g. 1-phenylethyl-1-hydroperoxide and 2-phenylpropyl-2 ~ hydroperoxide ( often referred to as ethylbenzene hydroperoxide and cumene hydroperoxide, respectively).

150593 2

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.

In particular, catalysts consisting of 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 show improved catalytic properties when treated with an organic silylating agent. Advantageously, the silicon solids have an average specific surface area of at least 1 mz / g and preferably from 25 m 2 / g to 800 mVg. Preferred silicon solids contain at least 99% by weight of silica.

As a rule, the catalysts are prepared 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 titanium dioxide of 20 silica.

The catalyst materials disclosed in Danish Patent Application No. 4741/71 may also contain non-interfering substances, especially those which are inert to the reactants and products, for example smaller amounts of the alkali metals or the alkaline earth metals.

The catalyst materials of the aforementioned patent application can be prepared by a variety of methods which are not critical to their operation or effect. A particularly suitable method consists in impregnating a silicon-containing support with a suitable metal-containing solution followed by heating.

Suitable impregnation solvents are non-basic oxygen-containing hydrocarbons which are substantially inert with ordinary betines, and which generally contain from 1 to 12 carbon atoms, e.g., alkanols, ketones, ethers (acyclic and cyclic) and esters.

Hydroxy or oxo-substituted hydrocarbons having 1-8 carbon atoms are preferred. Monofunctional alkanols having 1-8 carbon atoms, for example 5 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, the organosilylamines and the organosilazanes. Very good results are obtained using tetrasubstituted silanes having 1-3 carbohydrate and / or halogen substituents, e.g. dichlorodimethylsilane and chloro trimethylsilane.

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 catalysts 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 the organo-disilazanes will generally take place at lower temperatures in comparison with silylation using organosilanes. The selectivity to epoxides formed using a catalyst silylated according to the present invention has been found to be excellent.

The process of the present invention is of the kind in which the catalyst is prepared by modifying 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, and the process is characterized in that the 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 is contacted with an organic disilazane of the general formula: R1 R * R2—— Si - N - Si-R5 H R6.

wherein four or six of the symbols R1, R2, R3, R **, R5 and R5 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, with hydration treatment optionally before the silylation treatment.

It is preferred to use a disilazane in which four or 10 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. Hexamethyldisilazane is particularly preferred.

Surprisingly, it has been found that in the process 15 of the present invention using organodisilanes 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 compounds. hydroperoxides, which is of course technically attractive. Suitable silylation temperatures are between 100 and 300 ° C, preferably about 200 ° C.

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 above, 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 which are silylated at lower temperatures decreases rapidly.

It has been found that catalysts prepared by the process of the present invention by silylation at lower temperatures with an organodisilazane as set forth above provide at least as good hydroperoxide conversion and epoxide selectivity as the catalysts described in Application No. 4741/71. and remain much more active and selective, even after a longer period of time (more than 1000 hours) than the catalysts known from the prior application, and thus the catalysts prepared by the process of the invention are more stable.

In general, the catalysts to be silylated by the process of the present invention 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 for treatment by the process of the present invention consists essentially of silica which is chemically combined with from 0.5 to 5% by weight of titanium oxide.

The catalyst materials to be subjected to the process of the present invention 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 are in the range of 0.01 to 5% by weight, based on the total amount of catalyst. A suitable catalyst to be silylated by the process of the present invention contains substantially silica in chemical combination with 0.5-5% by weight titanium oxide and 0.01-5% by weight calcium in the form of calcium oxide as promoter.

The silylation can be carried out in many different ways as described in Danish Patent Application No. 4741/71. The silylation can be carried out charge-wise, semi-continuously or continuously. It has been found that, regardless of the method used, the best results are obtained when the appropriate silylation using organodisilazanes is carried out at temperatures in the range between 100 and 300 ° C, especially between 150 and 250 ° C.

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The time required for the reaction of the disilazane with the catalyst surface depends on the temperature used. Generally, treatment times of 0.5-5 hours are very convenient.

The amount of disilazan used may vary within wide limits.

Disilazane amounts of from 1 to 75% by weight, based on the entire catalyst material, are very suitable; amounts of from 2% to 50% by weight are preferred. 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 accomplished by contacting and then heating the catalyst with water prior to 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 1 / 2-6 hours. The best results are obtained when the hydration treatment is carried out by steam treatment at a temperature of 300-450 ° C for 1-6 hours.

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 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 silica 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

Claims (2)

Hexamethyldisilazane vapor at 200 ° C for 1 hour to give the silylated catalyst of the invention. 75 g of hexamethyldisilazane are taken up by the catalyst. The catalyst described above, as well as a similar catalyst which, however, has not been treated with hexamethyldisilazane, are subjected to comparative experiments as catalysts for the epoxidation of olefins. In each experiment, a 1 g sample of the catalyst mass is contacted 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 Catalyst Hydroperoxidome Epoxide Selectivity Formation (%) (%) 15 Unsilylated 95 72 S in the Clay 95 93 The data in the table clearly show that the silylated catalyst 20 has significantly higher selectivity over the desired epoxide. A process for preparing a metal / silicon-containing oxide-type solid catalyst for use in the preparation of oxirane compounds by reacting an olefinically unsaturated compound with an organic hydroperoxide, which catalyst is prepared by modifying a solid inorganic oxygen compound of chemical in chemical combination with at least 0.1% by weight of an oxide or hydroxide of titanium, molybdenum, vanadium, zirconium or boron, characterized in that the solid inorganic oxygen compound of silicon in chemical combination with at least 0.1% by weight of