Ar^+溅射对铁系催化剂表面物相影响的XPS研究

XPS study on the effect of Ar^+ sputtering on the surface phase of iron catalysts

乙苯脱氢Fe-K催化剂经长时间使用后表面物相以Fe3O4为主。采用Ar+溅射对标准Fe3O4样品及使用后的乙苯脱氢Fe-K催化剂进行XPS剖面分析。研究表明,Ar^+溅射能够择优溅射两个样品表面上的O^2-、OH^-阴离子,引起样品表面上的Fe^3+还原生成Fe^2+甚至是Fe0;从而导致Fe 2p及O 1s主峰结合能向低结合能方向漂移,同时O/Fe原子比也随溅射深度加大随之减少。对比实验发现,Fe-K催化剂表面的Fe^3+还原程度要小于标准Fe3O4样品。分析认为催化剂中K^+的存在抑制了Ar^+溅射的诱导还原效应,从侧面证明了钾助剂在乙苯脱氢过程中能够抑制Fe^3+的深度还原,某种程度上维持了表面Fe^3+/Fe^2+比,从而使Fe-K催化剂在反应中保持较高活性。

The surface phase of Fe-K catalyst was mainly Fe3O4 after a long time of use for ethylbenzene dehydrogenation.The XPS profile analysis was carried out on the standard Fe3O4 sample and the used Fe-K catalyst by Ar+sputtering.The results showed that Ar+sputtering can preferentially sputter O^2-,OH-anions and cause Fe^3+reduction to form Fe^2+or even Fe0 on the surface of samples.As a result,the binding energy of the main peaks of Fe 2p and O 1s drifted to the low binding energy and the O/Fe atomic ratio also decreased with the increase of sputtering depth.The results of comparative experiments indicated that the Fe^3+reduction on the surface of Fe-K catalyst is smaller than that of standard Fe3O4 sample.It is suggested that the presence of K+in catalyst inhibit the reduction effect of Ar+sputtering,which proves that K promoter can inhibit the deep reduction of Fe^3+in the process of ethylbenzene dehydrogenation and maintain the surface Fe^3+/Fe^2+ratio to some extent,so that the catalytic activity of Fe-K catalyst remains high in the reaction.