Catalytic activity of Me/CeO2-based (Me=Rh, Pt) catalysts in pellet and monolith form towards the steam reforming of n-dodecane

Alternative sustainable energy technologies are needed for future power generation. Although the use of fuel cells as auxiliary electrical power units (APUs) is attractive, due to the high energy conversion efficiency and the quite low levels of emissions, the lack of infrastructure for hydrogen production and storage remains a big issue. As a practical solution, onboard fuel processing system was proposed to convert liquid hydrocarbon fuels into hydrogen or hydrogen-rich syngas through reforming reactions. Among various hydrocarbon fuels, diesel is a plausible source of H2 production, due to its existing logistic infrastructure, considerable well-to-wheel efficiency, safe handling feature, adequate world-wide fuel storage and high energy density. In the recent years many research projects were focused on the development of durable diesel reforming catalysts, overcoming the chemical and mechanical degrade mainly due to the deposition of deleterious carbon species. In this study, the catalytic activity and stability of Pt/CeO2 and Rh/CeO2 catalyst (0.5 wt.% of metal loading) was comparatively probed towards the steam reforming (SR) of n-dodecane (n-C12H26), as model compound of marine diesel. Catalysts in pellet or coated monolith form were used. Powders were synthesized by combustion synthesis, while structured systems were prepared combining the combustion method with the impregnation technique over conventional 400 cpsi cordierite monoliths (62 cells per cm2). Catalysts were characterized by XRD, TPR, TEM, SEM and CO-Chemisorption analysis. Catalytic tests (TSET=800°C, S/C=1.5-2.0-2.5, WSV=8000-32000 Nmlogcat-1oh-1) were conducted employing a temperature-controlled catalytic bed configuration (450?800°C) in order to avoid the carbon formation due to the n-C12H26 cracking phenomena. At powders level, both catalysts ensure a total n-dodecane conversion and the production of a syngas with a high H2/CO (4-5) ratio principally due to the contribute of Water Gas Shift (WGS) reaction. Rh-based catalyst shows stable catalytic activity after 200h of time-on-stream, while Pt-based system shows a degradation of catalytic performance due to the deposition of various types of carbon species, as evidenced from the TPO and TEM characterization of spent catalyst. Structured Rh-based catalyst, characterized by a uniform and thin coating (20-25 ?m) and high mechanical strength, enhances catalytic activity, especially at higher space velocity. Furthermore, the adopted coating methodology can enable new process designs characterized by reduced production costs and smaller package size, thus improving the process design of the fuel processor technologies.