(343g) Carbon Deposition Over Supported Rh-Ni Catalysts in Steam Reforming of Liquid Hydrocarbon Fuel for H2 Production: Influence of Support, Temperature, and Sulfur

Carbon Deposition over Supported Rh-Ni Catalysts in Steam Reforming of Liquid Hydrocarbon Fuel for H₂ production: Influence of Support, Temperature, and Sulfur

Chao Xie^a, Yongsheng Chen^a,b, Chunshan Song^a,b*

^a Clean Fuels and Catalysis Program, EMS Energy Institute, The Pennsylvania State University, 209 Academic Projects Building, University Park, PA, 16802, USA..

^b Department of Energy and Mineral Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.

*Corresponding author: E-mail: csong@psu.edu; Tel: 814-863-4466; Fax: 814-865-3573

 

This contribution aims at elucidating the effects of support (Al₂O₃, CeO₂-Al₂O₃, and CeO₂-SiO₂), reaction temperature (550 and 800 ºC) and the presence of sulfur (350 ppm by weight) on the carbon deposition over bimetallic Rh-Ni catalysts in steam reforming of liquid hydrocarbon fuel for H₂ production. The amount, morphology, and chemical nature of carbon deposits on used catalysts were studied by temperature-programmed oxidation (TPO), scanning electron microscopy (SEM), and X-ray absorption near edge structure (XANES) spectroscopy. It was revealed that (I) CeO₂ modification facilitates carbon removal due to its superior redox property, and (II) Al₂O₃ is much more effective than SiO₂ in suppressing the growth of filamental carbon. As revealed by X-ray Diffraction (XRD) and temperature-programmed reduction (TPR), the Ni particles in Rh-Ni/CeO₂-Al₂O₃ were remarkably smaller than those in Rh-Ni/CeO₂-SiO₂ very likely because of the stronger interaction of Ni-Al₂O₃ as compared with that of Ni-SiO₂. Therefore, the growth of filamental carbon on Rh-Ni/CeO₂-Al₂O₃ was greatly hindered as carbon deposition becomes less favorable on smaller Ni particles. Comparative study of the used Rh-Ni/CeO₂-Al₂O₃ catalysts after the reactions without and with sulfur at 550 and 800 ºC indicated that both reaction temperature and the presence of sulfur dramatically affected the catalyst behavior of carbon deposition: (I) in the absence of sulfur, the formation of filamental carbon was significant at 550 ºC, which was prohibited by increasing the temperature to 800 ºC, and (II) for the sulfur-containing reaction, sulfur was able to suppress the growth of filamental carbon at 550 ºC, while catalyst deactivation caused by sulfur poisoning gave rise to abundant carbon deposits at 800 ºC as a result of severe hydrocarbon pyrolysis at such a high-temperature condition.