Ce1-xMxO2 (M=Ti, Zr and Hf) solid solution with controlled morphologies and porous structure of ceria applied on ethanol steam reforming

• Main Authors: Chen, Wei-Ta, 陳韋達
• Other Authors: Lee, Chi-Shen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/20593551788957977579

碩士 === 國立交通大學 === 應用化學系所 === 97 === I. Two Steps Synthesis of Ce1-xMxO2 (M=Ti, Zr and Hf) Solid- Solution with Controlled Morphologies Nanoscale Ce1-xMxO2 solid solution (M=Ti, Zr and Hf) with cube, rod and tube shapes are prepared via a simple two-step synthesis method. It is found that the effect of composition and morphology is related to reaction time, temperature and molar ratio of M/Ce. The structural and morphological analyses are investigated by Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Further, homogeneity in composition is confirmed by SEM/EDS, TEM/EDS and ICP-MS. STEM-EDX mapping images reveal uniform distribution of dopant element within the ceria matrix. Moreover, Surface area measurement indicates nanorods have the highest surface area. And TPR results demonstrate Ti-doped CeO2 nanorods have the highest oxidative power. For 5%Ru/Ce1-xMxO2 /Al2O3 as catalyst, the GC test shows the prepared Ce1-xMxO2 solid solution (M=Ti, Zr and Hf) with cube, rod and tube shapes exhibit a higher hydrogen selectivity for ethanol reforming compared to CeO2 nanoparticles. II. Porous Structure of CeO2 and ZrO2 sol-gel Applied on Ethanol Steam Reforming Ethanol is more attractive than methanol because of its relatively high hydrogen content, availability, non-toxicity and facile storage and handling safety. By utilizing the catalytic steam reforming reaction, it is possible to produce H2 from ethanol with the ideal hydrogen selectivity of 166%. For the purpose of manufacturing highly active catalysts, porous materials were used to enhance surface area that may affect the catalytic activity. In this research, two methods were introduced: (1)3-DOM CeO2 and ZrO2 were prepared through the interstitial spaces between polystyrene spheres assembled on glass substrates. (2)The porous Al2O3 supports (BET= 288 m2/g) immersed with CeO2 and ZrO2 sol-gel were used as catalysts. The characterization was investigated by scanning electron microscope (SEM) and Powder X-ray diffraction (PXRD). Steam reforming of ethanol were studied by catalysts of 5% Ru/ 3-DOM MO2, 5% Ru/ SixCe1-xO2 gel/Al2O3 and 3-9% Ru-SixM1-xO2 gel/Al2O3 (M=Ce,Zr) under different carbon-to-oxygen ratio (C/O). The best results indicate that the catalyst 9% Ru-Si0.33 Ce0.67 /Al2O3 exhibits optimized hydrogen selectivity (SH2 = 113.1%) at C/O = 0.6, and the catalyst is stable for at least 50 hrs with decay less than 4%.