July 4, 2011
Make 1-octene from a natural fatty acid with a bacterial enzyme. 1-Octene demand is growing, mainly because it is used as a comonomer in the manufacture of linear low-density polyethylene. Most 1-octene is made in linear α-olefin (LAO) plants, where ethylene is oligomerized to a range of α-olefins from 1-butene through C20s. Limited control over the relative production of LAOs is possible, but outlets for all of the products must be found for these plants to be profitable.
Sasol has developed three alternative methods for making 1-octene selectively: extraction from its synthetic fuels stream, hydroformylation of 1-heptene (also extracted from the synthetic fuels stream) followed by hydrogenation to 1-octanol and dehydration to 1-octene, and ethylene tetramerization. Dow Chemical recently commercialized a unique process to make 1-octene that involves telomerization of butadiene followed by hydrogenation of the double bonds and cracking of the methyl octyl ether to 1-octene.
J. R. Millis and colleagues disclose a process for making 1-octene from a renewable resource. Their technique is based on enzymatically isomerizing natural linoleic acid (with double bonds at the 9- and 12-positions) to a conjugated linoleic acid with the double bonds at the 9- and 11-positions. The conventional method for this isomerization is to heat the unsaturated acid in the presence of strong base. This method, however, gives a mixture of positional isomers of conjugated acids. Example 1 of this patent (which is oddly titled “Method for making industrial chemicals”), describes an enzymatic method for converting natural linoleic acid to the desired Δ-9,11-conjugated linoleic acid with cells from a strain of Lactobacillus reuteri.
The Δ-9,11-isomer is converted to its methyl ester and then metathesized with ethylene (at 150 psi and 60 °C) in CH2Cl2 over a homogeneous ruthenium Grubbs-type catalyst. After 6.75 h, the reaction mixture contains 13.2% 1-octene, 23.7% 1,3-decadiene, 35.2% methyl 9-decenoate, 8.2% methyl 9,11-dodecadienoate, and 16.2% unreacted starting material. (Elevance Renewable Sciences [Bolingbrook, IL]. US Patent 7,960,599, June 14, 2011; Jeffrey S. Plotkin)