(Fe,Cr)_(3)O_(4)催化剂表面酸性的研究

Surface Acidity of Chromia-Promoted Magnetite Shift Catalyst

本文研究了(Fe,Cr)_(3)O_(4)催化剂的表面酸性,发现其表面结构具有可变性,表面主要存在Fe^(2+)(α位)和Fe^(3+)(β位)两种酸中心,β位上吸附吡啶的Ed=278.8±13.8 kJ/mol。

The surface acidity of chromia-promoted magnetite shift catalyst, (Fe,Cr)_(3)O_(4), was studied by TPD technique. The experimental results revealed the variability of surface structure of the catalyst. The adsorption of pyridine rearranges the surface structure and accelerates the establishment of a stable adsorption state of pyridine on the surface.There exist mainly two kinds of acidic site, α and β,on the surface of catalyst. The content of surface oxygen of the catalyst treated by CO at higher temperature will be lower and the TPD peaks of pyridine absorbed on the catalyst, which had been treated by CO at different temperatures, varied regularly: the higher the treated temperature, the taller the peak α and the shorter the peakβ. This fact in combination with the shape and the position of peaks α and β had led to the conclusion that the peaks α and βare relative to Fe^(2+) site snd Fe^(3 +) site, respectively.The activation energy of desorption of pyridine, Ed on the site βhas been determined by consulting table method. Its value is 278.8 + 1 3.8kJ/mol.