Hydrodeoxygenation of cracked vegetable oil using CoMo/Al2O3 and Pt/C catalysts

During the continuous catalytic hydrodeoxygenation (HDO) of cracked vegetable oil (CVO), CO2 and CO occur as the main reaction gases, in addition to hydrocarbon gases such as CH4 and C2H6. The catalysts used were cobalt-molybdenum (CoMo) on an Al2O3 support and platinum (Pt) on an active carbon. All named gas components can result directly from the decomposition of CVO. The results of batch experiments for gas phase reactions (GPRs) under the same 50 bar H2 atmosphere using the same catalysts (CoMo, Pt) indicate that CO and CH4 can also be formed by GPRs. CO can result from the reverse water–gas shift reaction (RWGS), and CH4 from CO- or CO2-methanation. The found CO-yields from GPRs are within the theoretical thermodynamic limits based on equilibrium. An unexpected inhomogeneity of the gas component concentrations in the reactor during batch investigations was observed despite the elevated temperature (380 °C) and high RPM (1100) due to the high density difference compared to H2, especially in the case of CO2.