【摘要】 采用等体积浸渍法制备了Ni/SiC甲烷化催化剂,研究了SiC载体表面氧化程度对催化剂低温活性和高温稳定性的影响,并采用热重-差示扫描量热、N2物理吸附、傅立叶变换红外光谱、氨程序升温脱附、X射线衍射、氢程序升温还原和氢化学吸附技术对样品进行了表征.结果表明,随着载体氧化温度的提高,催化剂的比表面积和镍分散度降低,但还原性和反应稳定性提高.未氧化载体所负载催化剂的高温稳定性最差,其原因在于载体对镍粒子的固定作用最弱.负载于500和700℃处理的SiC载体上的催化剂具有较好的低温活性和高温稳定性,这是因为适度氧化后的载体能较好地分散并固定镍粒子.900℃处理的载体因过度氧化形成了低活性的氧化层,使负载的镍粒子变大,因而催化剂的低温活性最差.更多还原

【Abstract】 Ni/SiC methanation catalysts were prepared by an incipient wetness impregnation method. Effects of the oxidation extent of the SiC surface on low-temperature activity and high-temperature stability of the catalysts were investigated. Samples were characterized by thermogravimetry and differential scanning calorimetry, N2 adsorption-desorption, Fourier transform infrared spectra, temperature-programmed desorption of NH3 , X-ray diffraction, temperature-programmed reduction of H2 and H2 chemisorption. The surface area and nickel dispersion of the catalysts decreased with increasing oxidation temperature of the SiC supports, while both reducibility and stability of the catalysts increased. The Ni/SiC catalyst with the unoxidized SiC support showed the poorest high-temperature stability probably because of the weak anchorage of Ni particles to the support. The Ni/SiC samples prepared on the SiC supports oxidized at 500 and 700 ℃ had better low-temperature activity and high-temperature stability, which was because Ni particles were well dispersed on and strongly anchored to these properly oxidized supports. The Ni/SiC catalyst with the SiC support oxidized at 900 ℃ showed the worst low-temperature activity because of the larger Ni particles caused by the less active oxide layer due to the overoxidation of the support.更多还原