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 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.
2 . The process of claim 1 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.
3 . The process of claim 2 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 ).
4 . 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.
5 . 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.
6 . The process of claim 5 wherein the refractory oxide is silica.
7 . The catalyst of claim 6 wherein the silica is an acid washed silica.
8 . The process of claim 1 wherein the refractory oxide support has a surface area of at least 50 m 2 /g.
9 . The process of claim 8 wherein the refractory oxide support has a surface area from about 80 to about 500 m 2 /g.
10 . The process of claim 1 wherein the olefins are present in an amount of at least 80% by weight of the hydrocarbon feedstock.
11 . 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.
12 . The process of claim 1 wherein the first olefin is ethylene, the second olefin is butylene, and the third olefin is propylene.
13 . 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 .
14 . The process of claim 12 wherein a butene feed is isomerized prior to being fed to the catalyst.
15 . The process of claim 1 wherein selectivity to the third olefin is greater than 75%.
16 . The process of claim 1 wherein selectivity to the third olefin is greater than 90%.
17 . The process of claim 12 wherein the selectivity to propylene is at least 90%.
18 . The process of claim 12 wherein the unconverted ethylene and butene are separated from the third olefin propylene and recycled as feed to the process.
19 . The process of claim 12 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 .
20 . The process of claim 12 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.