Production of Renewable Light Olefins from Fatty Acid Methyl Esters by Hydroprocessing and Sequential Steam Cracking

A route to produce renewable light olefins from fatty acid methyl esters (FAMEs), which are originally derived from waste cooking oils, has been demonstrated on a laboratory scale. Presaturation of FAMEs prior to their hydrodeoxygenation over sulfided NiMo/Al2O3 catalysts in a fixed bed reactor avoided an undesirable guard bed fouling, which would appear inevitably when hydrotreating unsaturated FAMEs under the identical conditions, leading to a smooth operation during a period of 1000 h. Cracking performance of the resulting bioparaffins with straight chains were then evaluated in a micropilot furnace and compared with naphtha cracking. Under a coil outlet pressure of 0.10 MPa, a coil outlet temperature of 820 degrees C, a residence time of 0.23 s, and a steam dilution of 0.75, the overall yield of C-2-C-4 olefins when cracking bioparaffins was 68.4%, much higher than that of naphtha cracking (52.9%). In particular, the yields of valuable ethylene (36.3%), propylene (18.1%), and 1,3-butadiene (7.5%) added up to 61.9%, 30% higher than that from naphtha cracking, indicating the viable potential of the route to produce renewable light olefins in the existing cracking units.