H2 from biofuels and carriers: gas-phase and surface ethanol conversion pathways on Rh/Al2O3 investigated by annular microreactor coupled with Raman and FTIR spectroscopy

Abstract

Catalytic Partial Oxidation (CPO) and Steam Reforming of ethanol are studied on Rh/Al2O3. The main goal of the work is the development of a comprehensive methodological approach coupling catalytic activity testing and surface characterization, in order to investigate both ethanol-to-H2 conversion pathways and C-deposits formation.Experiments are performed in an annular reactor and four reaction regimes in CPO are identified: ethanol oxidative dehydrogenation to acetaldehyde (T < 200 °C); total oxidation and initial ethanol O2-assisted ethanol decomposition (200 °C < T < 300 °C); early H2 and CO production for reforming of surface CHx fragments (300 °C < T < 500 °C); development of ethanol steam reforming (T > 500 °C).Adsorbed species and C-deposits are characterized via operando FTIR, ex-situ Raman and TPO. These analyses proved that the different reaction regimes are reflected in continuous changes of catalytic surface coverage, passing from the co-existence of ethanol and O2 at low temperature, to wide C-coverage when O2 is consumed. At 700 °C gasification is favoured and promotes surface cleaning.