Preparation of honeycombed holmium-modified Fe-Mn/TiO₂ catalyst and its performance in the low temperature selective catalytic reduction of NO_x

A series of honeycombed holmium-modified Fe-Mn/TiO₂ catalysts were prepared by moulding method and their performance in the low temperature selective catalytic reduction (SCR) of NO_x was investigated. The forming process was optimized as:the mass content of water in the forming additives is 40%, in which 10% structure strengthening agent (glass fiber), 5% binder (carboxymethyl cellulose), 10% squeezing agent (glycerin), 5% pore-forming agent (activated carbon) and a little lubricants (liquid paraffin) are added. The honeycombed Fe-Ho-Mn/TiO₂ catalyst prepared under these conditions exhibits excellent performance in the low-temperature SCR of NO_x; the conversion of NO_x exceeds 90% at 120℃ and a good resistance to SO₂ and H₂O is observed when the content of SO₂ in the stream is lower than 0.02%. The characterization results indicated that in comparison with the parent powder holmium-modified Fe-Ho-Mn/TiO₂ catalyst, the honeycombed catalyst exhibits lower surface area, more particle aggregation, and less acid sites and Mn⁴⁺ species on the surface, which has a certain negative influence on the catalytic performance of Fe-Ho-Mn/TiO₂.