Hybrid Catalyst for Olefin Metathesis

Abstract

An olefin metathesis catalyst and method for producing same is provided.

Claims

1. A method of preparing a hybrid metathesis catalyst, the method comprising the steps of: contacting a metathesis catalyst present in an organic solvent with a silica support containing a halogen or hydroxyl ligand capable of participating in a ligand exchange reaction; appending the metathesis catalyst to the silica support via the ligand exchange reaction to form a hybrid metathesis catalyst; and recovering the hybrid metathesis catalyst from the organic solvent.

2. The method of claim 1, wherein the silica support is mesoporous silica.

3. The method of claim 1, wherein the metathesis catalyst contains a metal selected from the group consisting of tungsten, molybdenum and ruthenium.

4. The method of claim 1, wherein the metathesis catalyst is benzylidene-bis(tricyclohexylphosphine)dichlororuthenium.

5. The method of claim 1, wherein the metathesis catalyst is benzylidene[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium.

6. The method of claim 1, wherein the organic solvent is toluene.

7. The method of claim 1, wherein the step of contacting the metathesis catalyst with the silica support is performed by an incipient wetness method.

8. A method for the metathesis of butene to produce propene, the method comprising the steps of: providing, to a reaction chamber, a hybrid metathesis catalyst prepared by: contacting a metathesis catalyst present in an organic solvent with a silica support containing a halogen or hydroxyl ligand capable of participating in a ligand exchange reaction; appending the metathesis catalyst to the silica support via the ligand exchange reaction to form the hybrid metathesis catalyst; and recovering the hybrid metathesis catalyst from the organic solvent; contacting, in the reaction chamber, an olefin feedstream containing one or both of 1-butene or 2-butene with the hybrid metathesis catalyst to produce a product stream containing propene; withdrawing the product stream containing propene; and separating the hybrid metathesis catalyst from the product stream.

9. The method of claim 8, wherein the silica support is mesoporous silica.

10. The method of claim 8, wherein the metathesis catalyst contains a metal selected from the group consisting of tungsten, molybdenum and ruthenium.

11. The method of claim 8, wherein the metathesis catalyst is benzylidene-bis(tricyclohexylphosphine)dichlororuthenium.

12. The method of claim 8, wherein the metathesis catalyst is benzylidene[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium.

13. The method of claim 8, wherein the organic solvent is toluene.

14. The method of claim 8, wherein the olefin feedstream is a mixture of 1-butene and 2-butene in a ratio of concentration ranging from 40:60 to 50:50.

15. The method of claim 8, wherein the olefin feedstream further includes ethene.

16. The method of claim 8, wherein the product stream further includes one or more of ethene, pentene, and hexene.

17. The method of claim 8, wherein the step of contacting, in a reaction chamber, the olefin feedstream containing one or both of 1-butene or 2-butene with the hybrid metathesis catalyst is performed at a reaction temperature of less than 100 degrees Celsius.

18. The method of claim 8, wherein the step of contacting, in a reaction chamber, the olefin feedstream containing one or both of 1-butene or 2-butene with the hybrid metathesis catalyst is performed at a reaction temperature of 50 degrees Celsius.

19. The method of claim 8, wherein the olefin feed stream essentially contains 1-butene.

20. The method of claim 19, wherein the product stream further contains negligible amount of C.sub.7+ products.

Description

EXAMPLE 1

[0042] In a first example, a Grubbs first generation catalyst can be loaded onto a silica support material as follows:

SiOH+ClC.sub.43H.sub.72ClP.sub.2Ru.fwdarw.SiOC.sub.43H.sub.72ClP.sub.2Ru+HCl

[0043] In certain embodiments, it is assumed that only about 1% of the hydroxyl groups present on the surface of the support material will react with the Grubbs catalyst to produce the hybrid catalyst of the present invention. In the present example, approximately 0.05 g of the first generation Grubbs catalyst (benzylidene-bis(tricyclohexylphosphine)dichlororuthenium) is dissolved in approximately 10 mL of toluene. The catalyst is then loaded onto the silica gel support by impregnation with the incipient wetness method. In general, the Grubbs catalyst in the toluene solution is contacted with the silica gel for at least about 30 min., alternatively between about 10 and 20 min. The resulting silica gel, having been impregnated with the Grubbs catalyst, is removed from the toluene solution and dried in a vacuum oven at about 50 C. for at least about 2 hours, alternatively at least about 4 hours. The resulting dried, impregnated catalyst support material is then contacted with the toluene solution containing the Grubbs catalyst for sufficient time to further impregnate the support material, and dried under vacuum. The steps of contacting the support material with the toluene solution can be repeated until no toluene solution remains. The procedure can be used for either first or second generation Grubbs catalysts.

[0044] The above described incipient wetness method can be used to impregnate a solid silica support material with a catalyst mixture. For example, in certain embodiments, the mixture can include various ruthenium carbene catalysts, such as a mixture that includes Grubbs first and second generation ruthenium carbene catalysts, wherein the first generation Grubbs catalyst has a molecular formula C.sub.43H.sub.72Cl.sub.2P.sub.2Ru (IUPAC name benzylidene-bis(tricyclohexylphosphine)dichlororuthenium) and the second generation Grubbs catalyst has a molecular formula C.sub.46H.sub.65Cl.sub.2N.sub.2PRu (IUPAC name benzylidene[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium). In certain embodiments, the Hoveyda-Grubbs catalyst can also be used to prepare the hybrid catalyst.

EXAMPLE 2

[0045] A comparison of the activity, selectivity, and reaction conditions for a commercially available heterogeneous catalyst (WO.sub.3/SiO.sub.2), an unsupported homogeneous catalyst (first generation Grubbs catalyst; benzylidene-bis(tricyclohexylphosphine)dichlororuthenium), and the hybrid catalyst of the present invention (first generation Grubbs catalyst on SiO.sub.2 support) is provided in Table 1, below. The olefin metathesis reaction conditions for each catalyst are listed, and as shown, the commercial heterogeneous is shown to have higher conversion, lower selectivity and requires substantially greater operating temperatures. The olefin feed for the metathesis reaction is a mixture of 1-butene and 2-butene ranging from about a 40:60 to a 50:50 mixture thereof.

TABLE-US-00001 TABLE 1 Commercial Commercial Unsupported Hybrid Catalyst Heterogeneous Heterogeneous Homogeneous (homogeneous Catalyst Catalyst Catalyst supported catalyst) Conversion 60% 65.7% 53.3% ~53.5% Selectivity 27% 45.8% 49% ~49% Reaction Temperature 350 C. 400 C. 50 C. ~50 C. Reaction Pressure 20 bar 20 bar 20 bar ~20 bar C7+ products 2.5% 4.2% ~0% ~0%

[0046] With an olefin feed that is pure 1-butene, the hybrid catalyst can have a selectivity of at least about 95%, alternatively at least about 97%, or alternatively at least about 99%. In comparison, commercial WO.sub.3/SiO2 system are typically a lot less selective with considerable amounts of propene and 2-pentene being produced, due to a high isomerization activity.

[0047] Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations to the catalysts, methods for preparing the catalysts, and use of the catalysts can be made without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.

[0048] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0049] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0050] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0051] Throughout this application, where patents or publications are referenced, the disclosures of these references in their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these references contradict the statements made herein.