Thursday, November 8, 2007 - 2:00 PM
587e

Partial Hydrogenation Of Vegetable Oil Using Membrane Reactor: Composite Membrane Properties And Their Influence On Hydrogenation

Devinder Singh, Mary E. Rezac, and Peter Pfromm. Chemical Engineering, Kansas State University, Manhattan, KS 66506

Partially hydrogenated vegetable oil is used in margarines and baked and fried food products. U.S. consumption of partially hydrogenated vegetable oil is nearly 14 billion pounds per year. The conventional hydrogenation process used produces trans fatty acids (TFA), the content of which can be as high as 45-50% in some margarines. Dietary TFAs are associated with increased risk of ischemic heart disease, colon cancer, type-2 diabetes and allergic diseases in children. FDA regulations require listing of the TFA content on food labels. The design of a commercial hydrogenation process/technology that produces minimum amounts of TFA becomes essential.

In the current technology catalyst particles are immersed in oil that contains small amounts of dissolved hydrogen which results in the catalyst surface being hydrogen starved and thus promotes the isomerisation to TFAs. Our approach is to combine the existing and productive catalysts available for liquid phase hydrogenation with a novel approach for the delivery of hydrogen to the catalyst surface. In this approach, the multiple phase reactors currently employed are replaced by a membrane reactor capable of selectively supplying hydrogen to the catalyst surface at the rate of consumption. A membrane capable of selectively transporting hydrogen while acting to prevent any loss of liquid phase is incorporated in the reactor housing. Oil is pumped on one surface of the membrane where it comes into contact with the catalytic metal surface supported on the polymeric integral-asymmetric membrane support. The metal catalyst has a high hydrogen coverage achieved by diffusion through the membrane due to an imposed chemical potential driving force. High concentrations of hydrogen on the catalyst surface, and the resulting decrease in necessary temperature and pressure, promote the hydrogenation reaction at the expense of the unwanted cis to trans isomerization. The metal-polymer composite membrane properties like gas flux, selectivity, and catalyst concentration / surface area have a significant influence on the hydrogenation and cis-trans isomerization. The surface of the membrane was studied using SEM and TEM techniques. The presentation will discuss the concept, the properties of the composite membranes and the effect it has on the hydrogenation and cis-trans isomerization.