Partial Hydrogenation of Soybean Oil with Minimal Trans Fat Production Using a Pt-Decorated Polymeric Membrane Reactor

Partial hydrogenation of vegetable oils is carried out to improve the chemical stability and raise the melting point to produce semi-solid products such as margarine. Trans fatty acids formed during traditional hydrogenation have come under intense scrutiny with regard to human health. Here we report partial hydrogenation of soybean oil using a high performance integral-asymmetric polyetherimide membrane sputtered with platinum to deliver hydrogen directly to or near the catalytic sites. Oil flows past the platinum-coated skin side of the membrane while dissolved molecular and some atomic hydrogen is supplied from the highly porous substructure of the membrane. The membrane has a high hydrogen flux but is essentially impermeable to soybean oil. Hydrogenation using our metal/polymer catalytic composite membrane produced oil with only 4 wt.% total trans fatty acids and 14.5 wt.% C18:0 saturates at IV of 95 while the conventional Pt/C slurry reactor produced more than 10 wt.% TFA and the same amount of C18:0 saturates under similar conditions of temperature and pressure. Our concept requires hydrogen pressures of only about 65 psi and temperatures near 70 A degrees C. The polymeric base membranes used here have been mass produced and can be packaged in spiral wound modules. The relatively mild reaction conditions and the direct pathway to produce useful membrane modules combine to make our concept promising for near-term application.