Vegetable Oils Yield Polymer Precursors

A reaction sequence for converting raw olive, rapeseed, and sunflower oils into polymer precursors could one day provide inexpensive replacement feedstocks for petroleum-derived monomers used to make high-volume polymers, an international research team reports (Green Chem., DOI: 10.1039/c1gc16094j). Led by Stefan Mecking of the University of Konstanz, in Germany, and David J. Cole-Hamilton of the University of St. Andrews, in Scotland, the researchers combined the oil, a palladium phosphine catalyst, carbon monoxide, methanol, and methanesulfonic acid in a high-pressure reactor. The oil’s triglycerides first break apart to form unsaturated methyl esters, and then the ester double bond isomerizes to the end of the fatty acid chain, where it’s trapped by a methoxycarbonylation step to form a terminal diester—dimethyl 1,19-nonadecanedioate, CH₃OC(O)(CH₂)₁₇C(O)OCH₃. The team showed that this diester can be hydrogenated using a ruthenium phosphine catalyst to form a diol or hydrolyzed to form a diacid. The diester, diol, and diacid can all serve as polymer precursors, the researchers note. For example, a polyester made from the diester and diol has properties similar to those of polyethylene, Cole-Hamilton says. “We now have a simple catalytic route to a possibly biodegradable polyethylene replacement from renewable resources,” he adds, at a cost of just a few dollars per kilogram for the polymer precursors.