Hydrogenation of sulfur dioxide to hydrogen sulfide on chromium promoted Fe/SiO_2 catalysts

摘要

The hydrogenation of sulfur dioxide to hydrogen sulfide was studied over a series of Fe-Si-Cr catalysts in a flow reactor.These catalysts were prepared by co-precipitation of iron nitrate,sodium silicate and chromium nitrate,which had Cr/Fe atomid ratios of 0-0.04 and Si/Fe atomic ratios of 0-1.2.The addition of Cr and Si dramatically improved the SO_2 hydropgenationactivity of the iron-based catalyst.The chromia was a textural promote45 of iron,increased the catalyst surface area by preventing the iron sintering,and hence resulted in the improved hydrogenatio activity.The silica acted as a support for disprsing the active species.The interaction between iron cation and silica was observed by using temperature-programmed reduction active species.The interaction between iron cation and silica was observed by using temprture-programmed reduction (TPR) of the fresh Fe-Si-Cr catalysts.The catalyst with a Fe/Si/Cr atomic ratio of 1/0.6/0.01 had the highest activity,which exhibited much better SO_2 hydrogenation activity than the best Fe/gamma-Al_2O_3 catalyst reported before.With a given space velocity,the former catalyst achieved 100% H_2S yield at a temperature 50 deg C lower than the latter catalyst.X-ray diffraction (XRD) meaurements indicated that FeS_2 was the active species for SO_2 hydrogenation,and the Fe-Si-Cr catalyst had smaller FeS_2 crystal size than the Fe/gamma-Al_2O_3 catalyst.The iron-silica interaction and the smaller crystal size might be responsible for the better SO_2 hydrogenation activity observed on the Fe-Si-Cr catalyst.