Activation treatments and surface study of amorphous Fe90Zr10 and Fe87.8Zr10Co2Al0.2 catalysts

The activation behavior of amorphous Fe90Zr10 and Fe87.8Zr10Co2Al0.2 alloy ribbons and the effect of surface impregnation with KNO3 on the catalytic activity of Fe87.8Zr10Co2Al0.2 have been studied under the condition of ammonia systhesis. The changes of both the bulk structure and the surface state during activation have been investigated by XRD, AES, SAM, XPS and SEM. No activity was detected initially on as-received ribbon surface because the surface was covered by an oxide layer of Zr and Fe. With in situ activation the catalytic activity of the ribbon surface increased gradually, which is closely related to the reduction of Fe oxide, the crystallization of amorphous precursors and the enhancement of the surface area of the ribbons. Impregnation with KNO3 on stream on the ribbon surface could further cause a significant increase of activity, which is expected due to the decomposition of KNO3 into oxide of potassium during in situ activation. The strong surface enrichment of Al was observed on the surface of activated catalyst. The surface structure of active Fe87.8Zr10Co2Al0.2 consists of α-Fe particles and oxides of K, Al and Zr.