In the last years, much attention has been devoted to the valorization of glycerol. Glycerol is obtained as byproduct in the transesterification reaction of fatty acids to produce biodiesel. With the significant increase of worldwide biodiesel production, there is also an important in­crease in glycerol availability. Due to the increments in biodiesel manufacture, important amounts of glycerol have been placed in the market, and glycerol has become a waste difficult to handle. The volumes of glycerol remaining unsold in recent years are a clear example of wasted energy and material resources. This is the reason why intense research activity has started worldwide in order to find an exit to the big amounts of glycerol produced. Glycerol price has experimented constant reduction during the last years. Low glycerol prices allow new interesting applications like the production of high added value chemicals. Effective val­orization of glycerol will enable to make more cost effective biodiesel production and to re­place fossil fuels as the raw material for the production of commodity chemicals.

Among the different possible transformations of glycerol, the hydrogenolysis to propane­diols (PDO) presents special interest due to the big number of applications of both 1,2 and 1,3-propanediol (PDO). 1,3-PDO has traditionally been considered a specialty chemical; it has been used in the synthesis of polymers and other organic chemicals, but its market has been quite small. However, over the past years this situation has changed significantly. 1,3- PDO is a starting material in the production of polyesters. It is used together with tereph — thalic acid to produce polytrimethylene terephthalate (PTT), which is in turn used for the manufacture of fibers and resins. This polymer is currently manufactured by Shell Chemical (Corterra polymers) and DuPont (Sorona 3GT).1,2-PDO is a major commodity chemical tra­ditionally derived from propylene oxide, and hence also based on fossil feedstock. It is a widely used commodity chemical that plays a significant role in the manufacture of a broad array of industrial and consumer products, including unsaturated polyester resins, plasticiz­ers and thermoset plastics, antifreeze products, heat-transfer and coolant fluids, aircraft and runway deicing products, solvents, hydraulic fluids, liquid detergents, paints, lubricants, cosmetics and other personal care products. Today, the industry estimates a global demand for 1,2- PDO between 2.6 and 3.5 billion lb/yr [48]. One of the future main markets for 1,2- PDO shall be the substitution of ethylene glycol (EG) in cooling water systems to prevent freezing, as ethylene glycol is harmful to health.