K_2O-Fe_2O_3系催化剂的穆斯堡尔谱研究

Abstract

利用穆斯堡尔谱在k2 O fE2 O3催化剂中检出了α fE2 O3(大晶粒及微晶 )、kfEO2 、k1+ XfE11O17、α fEOOH和γ fEOOH等物相 ,它们的相对含量取决于催化剂的含钾量及煅烧温度 ,相对含量的改变导致样品的穆斯堡尔谱图出现了复杂的变化 .与Xrd相比 ,穆斯堡尔谱可对钾与氧化铁的相互作用进行更有效的表征 ,穆斯堡尔谱和TPr研究都表明钾可延缓催化剂中fE(III)的被还原 .

Fe 2O 3 K 2O Catalysts with different content of K 2O and calcined at different temperature were characterized by using Mssbauer spectroscopy.It was found from the experiments that only a sextuplet assignable to Fe 3+ of α Fe 2O 3 could be detected while the K 2O content in these catalysts were lower than 5%and the calcination temperature was below 900℃;and complex spectra ,which could be fitted with several sextuplets of trivalent irons present in α Fe 2O 3, KFeO 2, K 1+ x Fe 11 O 17 and α FeOOH ,and a doublet of Fe 3+ in γ FeOOH ,would be observed if the K 2O content were 10%～27%and the calcination temperature were 800～900℃.The γ FeOOH,as a hydrous iron oxide ,was the decomposition product of KFeO 2 which was strong hydroscopic by absorbing moisture from the atmosphere.The results also suggested that Mssbauer spectroscopy was a better mean than XRD for the characterizations of Fe 2O 3 K 2O catalysts,by which ,α FeOOH ,γ FeOOH and α Fe 2O 3 in amorphous or crystallite forms ( unable to be found by XRD ) could be detected .It was also shown from the Mssbauer spectroscopy and a TPR studies that potassium could retard the reduction of Fe(III) to Fe(II) in the Fe 2O 3 K 2O catalysts.