Cobalt-Alumina Coprecipitated Catalysts for Green Diesel Production

Cobalt-alumina catalysts with high Co loading (35-70 wt %) were synthesized by coprecipitation. The influence of activation (reduction) temperature and the Co loading on their efficiency for green diesel production via selective deoxygenation (SDO) of solvent-free sunflower oil (SO) and waste cooking oil (WCO) has been investigated. The change of reduction temperature and the cobalt content caused remarkable changes in the physicochemical properties and catalytic behavior of the catalysts. A catalyst containing 55 wt % Co, activated at 500 degrees C, proved the most efficient. Its high efficiency has been attributed to its high metallic cobalt surface, the synergy between Co-0/CoO phases, and its relatively enhanced moderate and strong acidity. The catalysts studied exhibited relatively lower performance in the SDO of WCO than that in the SDO of SO. This has been attributed to their deactivation caused by extended coking and concomitant pore blockage.