3. Catalysts

Catalysts vary according to the degree of selectivity that they provide. Supported on various materials, nickel is invariably used commercially to hydrogenate fats. There are however other catalysts available such as copper, copper/chromium combinations, and platinum. Palladium has been shown to be more efficient than nickel due to the amount of catalyst required, although it invariably results in greater quantities os trans isomers. Homogeneous catalysts, soluble in oil, enable greater contact between oil and catalyst, thus providing more control of selectivity, but may prove elusively difficult to separate and recover.

A number of different compounds have the capacity to poison the catalyst used, and they are often the source of problems during commercial hydrogenation processes. These include: phospholipids, sulfur compounds, partial glycerol esters, mineral acids, CO₂, water and soaps.