Olefin metathesis process using a catalyst containing tungsten fluorine bonds
A process for the metathesis of olefins has been developed. The process comprises contacting a hydrocarbon feedstock with a catalyst at metathesis conditions. The catalyst comprises a tungsten compound, which contains at least one tungsten-fluoro bond, dispersed or grafted onto a support. A specific example of the catalyst is the compound WOF(CH 2 CMe 3 ) 3 grafted onto a silica support. The feedstock comprises a first and a second olefin wherein the second olefin has a carbon number of at least two greater than the first olefin and the product is an olefin with a carbon number intermediate between the first and second olefin. Specifically the process produces propylene from ethylene and butylene.
1. An olefin metathesis process comprising contacting a hydrocarbon feedstock with a catalyst that does not comprise a promoter comprising a niobium compound at metathesis conditions to produce an olefin product, wherein the hydrocarbon feedstock comprises olefins including a first olefin and a second olefin having a carbon number of at least two greater than that of the first olefin, to produce a third olefin having an intermediate carbon number and the catalyst comprises a tungsten metal compound characterized in that it contains at least one tungsten-fluorine bond, the compound dispersed on a refractory oxide support wherein the compound is chemically bonded to the support,
wherein the tungsten containing compound is selected from the group consisting of WR 4 F, WOFR 3 , W(NR′)FR 3 , and mixtures thereof and wherein R is an organic group which does not have any hydrogen atoms beta to the tungsten and R′ is an organic group selected from the group consisting of H, phenyl, 2,6-dimethylphenyl and methyl.
2. The process of claim 1 wherein R is selected from the group consisting of neopentyl (—CH 2 CMe 3 ); methyl, 2,2-diethylpropyl (—CH 2 C(CH 2 CH 3 ) 2 Me), and 2,2-diethylbutyl (—CH 2 C(CH 2 CH 3 ) 2 CH 2 CH 3 ).
3. The process of claim 1 wherein the tungsten is present in an amount from about 0.5 to about 10 wt % of the catalyst as the metal.
4. The process of claim 1 wherein the refractory oxide support is selected from the group consisting of silica, aluminas, silica-aluminas, titania, zirconia and mixtures thereof.
5. The process of claim 4 wherein the refractory oxide is silica.
6. The process of claim 5 wherein the silica is an acid washed silica.
7. The process of claim 1 wherein the refractory oxide support has a surface area of at least 50 m 2 /g.
8. The process of claim 7 wherein the refractory oxide support has a surface area from about 80 to about 500 m 2 /g.
9. The process of claim 1 wherein the olefins are present in an amount of at least 80% by weight of the hydrocarbon feedstock.
10. The process of claim 1 wherein a molar ratio of the first olefin to the second olefin in the hydrocarbon feedstock is from about 0.5:1 to about 3:1.
11. The process of claim 1 wherein the first olefin is ethylene, the second olefin is butylene, and the third olefin is propylene.
12. The process of claim 1 wherein the hydrocarbon feedstock is contacted with the catalyst at a temperature from about 75° C. (167° F.) to about 400° C. (752° F.), an absolute pressure from about 0.5 bar (7.3 psi) to about 35 bar (508 psi), and a weight hourly space velocity from about 1 to about 100 hr −1 .
13. The process of claim 11 wherein a butene feed is isomerized prior to being fed to the catalyst.
14. The process of claim 1 wherein selectivity to the third olefin is greater than 75%.
15. The process of claim 1 wherein selectivity to the third olefin is greater than 90%.
16. The process of claim 11 wherein the selectivity to propylene is at least 90%.
17. The process of claim 11 wherein the unconverted ethylene and butene are separated from the third olefin propylene and recycled as feed to the process.
18. The process of claim 11 wherein the hydrocarbon feedstock is contacted with the catalyst at a temperature from about 75° C. (167° F.) to about 400° C. (752° F.), an absolute pressure from about 0.5 bar (7.3 psi) to about 35 bar (508 psi), and a weight hourly space velocity from about 1 to about 100 hr −1 .
19. The process of claim 11 wherein at a least a portion of the ethylene in the hydrocarbon feedstock is obtained from a low boiling fraction of an ethylene/ethane splitter and/or at least a portion of the butylene is obtained from an oxygenate to olefins conversion process.