Performance of Mn-based H2S sorbents in dry, reducing atmosphere - Manganese oxide support effects

High temperature H2S sorbents comprising manganese oxide (15 wt.%) supported on TiO2, ZrO2, CeO2 and Al2O3 were prepared by wet impregnation using Mn(NO3)(2)center dot 4H(2)O as Mn precursor. Upon activation in H-2, the sorbent performance testing was conducted at 650 degrees C in a model gas mixture with a composition of 0.4 vol.% of H2S in 40 vol.% of H-2, the balance being inert gas. Sorbent regeneration was performed at 650 degrees C with 5.2 vol.% of O-2 in N-2. The initial sorption performance is first reported for the parent (Mn-free) supports showing a considerable H2S sorption on ZrO2 and CeO2 and a minor sorption on Al2O3 and TiO2. The Mn sorbents were subject to 13 sorption/regeneration cycles. The highest initial sorption capacity is reported for cerium supported Mn oxide, which is also the sample that deactivates most. A prolonged exposure to H-2 at 650 degrees C results in a reversible loss of the sorption capacity that was observed for all the samples except for Mn on zirconia suggesting its superior stability in H-2. The supports, fresh and regenerated Mn sorbents were characterized by means of N-2 sorption measurements, X-ray Diffraction and Raman spectroscopy. Temperature-Programmed Reduction was performed on the parent supports and fresh sorbents. The changes in material properties caused by the testing as well as a different degree of a metal oxide-support interaction influencing the sorption performance are discussed. (C) 2017 Elsevier Ltd. All rights reserved.