Ni/Ce-Zr-Al-O催化剂的表面碱性和CO2＋CH4重整性能

用水热法制备了不同NiO含量的Ni/Ce-Zr-Al-O催化剂.用H2-TPD (程序升温脱附),DRIFTS(漫反射红外傅立叶变换光谱),CO2-TPD等方法考察了NiO的含量对催化剂表面碱性的影响,并和反应稳定性以及抗积碳性能相关联.H2-TPD结果表明,随NiO含量的增加,催化剂表面的Ni含量增加.DRIFT和CO2-TPD结果表明CO2的化学吸附主要是碳酸盐和碳酸氢盐形式.添加少量Ni能够使表面碱性位数量显著增加,碱强度减弱.Ni可能优先占据在催化剂表面较强的碱性位上,再增加Ni的含量则会使碱强度减弱,碱性位有所减少,降低CO2的吸附性能,从而减弱从CO2获得活动氧以消碳的能力.这种作用使NiO含量为7.0％(w)的样品活性随反应进行而减低,积碳量是NiO含量为4.0％(w)的样品的3.7倍.

Surface Basicity and Catalytic Performance on Ni/Ce-Zr-Al-O Catalyst for CO2+CH4 Reforming

Ni/Ce Zr Al O catalysts were prepared by hydrothermal synthesis method.The effect of NiO content on the basicity of catalyst was investigated by using H2 TPD (temperature programmed desorption),DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy),and CO2 TPD.The catalytic performance was tested and the amount of coke deposition was measured.The H2 TPD result shows that the amount of Ni on the catalyst surface increases with the NiO content.DRIFT and CO2 TPD results show that the bicarbonate and carbonate are the predominant species of the CO2 chemisorptions.The addition of few Ni can promote obviously CO2 chemisorption and weaken the intensity of basicity.While Ni metal is preferable to reside on stronger basic site,the increase of NiO content can weaken the basicity,decrease the amount of basic site and weaken the CO2 adsorption performance.It weakens the performance of eliminating coke by mobile oxygen originated from CO2.So the catalytic activity of the sample with 7.0%(w) NiO decreases during reaction,the amount of coke deposition is much higher than that of the sample with 4.0%(w) NiO.