Catalytic partial oxidation of ethanol over Rh-coated monoliths investigated by the axially resolved sampling technique: Effect of H2O co-feed

The catalytic partial oxidation (CPO) of ethanol with H2O co-feed was studied in a laboratory scale adiabatic reactor on Rh/α-Al2O3 catalysts deposited on honeycomb monoliths. In order to understand the behavior of the homogeneous and the heterogeneous reactions taking place in the CPO process, axial temperature and concentration profiles were collected using a spatially resolved sampling technique. The effect of steam co-feed was studied at C/O ratio of 0.65, varying the H2O molar concentration in the feed from 0% to 10 %. H2O was added to the system by replacing part of the diluting N2, keeping a constant ethanol concentration. At increasing H2O feed content, ethanol conversion grew close to 100 %. The water gas shift reaction was promoted, which resulted in increased H2 yield and H2/CO ratio. Globally, thermal effects of the water co-feed were negligible. Noteworthy, a significant drop of the concentration of cracking products such as CH4, and C2H4 in the initial part of the reactor was observed in the presence of water co-feed. Beneficial effects on the catalyst stability were also observed by performing tests of CH4-CPO (a reference reacting system that, due to the sensitivity of the temperature profile to the catalyst activity, is used to detect catalyst deactivation processes in between ethanol CPO tests) and by TPO measurements on the used catalysts. Less pronounced drift of the temperature-profile in CH4-CPO and lower carbon deposition were in fact associated with the water co-feed operation of the reactor.