Selective Hydrogenation in Biodiesel Production

Another pool of ra v materials that up to now has not been considered for the manufacture of biodiesel is highly unsaturated vegetable oils, such as those obtained from linseed or camelina, which give a yield of oil per hectare higher than soybean. 

The degree of unsaturation of the fatty acids is normally expressed as the iodine value (IV), that is, the number of grams of iodine that have reacted with 100 g of product analyzed, under controlled experimental conditions. The higher is IV, the greater is the degree of unsaturation. For example, for biodiesel intended for haulage use, the most remunerative use, a maximum IV limit of 120 g I2 per 100 g is envisaged. 

Biodiesel is normally produced by starting from vegetable oils having an IV of 130, that is, having a low unsaturation index, such as rapeseed oil (IV = 110-115), sunflower oil (IV = 120-130) and soybean oil (IV = 125-135). 

On the other hand, in order to preserve the cold properties of the fuel (cloud point, pour point and low-temperature filterability), it is essential not to increase the melting point, which in turn depends on both the saturated compound (stearic acid, C18 0, 

For all these reasons, the monounsaturated methyl oleate and methyl palmitoleate (C16 l) have been identified as the ideal components of biodiesel [41]. 

---