The influence of a silica pillar in lamellar tetratitanate for selective catalytic reduction of NOx using NH3

Silica-pillared layered titanate (SiO2–Ti4O9) was prepared by intercalating organosilanes into the interlayers of a layered K2Ti4O9 followed by calcination at 500 °C. The lamellar titanates produced were used as a support to prepare vanadium catalysts (1 and 2 wt%) through wet impregnation for selective catalytic reduction (SCR) of NO. The catalysts were characterized using nitrogen adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), nuclear magnetic resonance (29Si NMR), and infrared spectroscopy (FT-IR). Reduction of NO by NH3 was studied in a fixed-bed reactor packed with the catalysts and fed a mixture comprising 1% NH3, 1% NO, 10% O2, and 34 ppm SO2 (when used) in helium. The results demonstrate that activity is correlated with the support, i.e., with acidic strength of catalysts. The potassium in the support, K2Ti4O9, significantly affected the reaction and level of vanadium species reduction. The catalyst (1VSiT) with 1 wt% vanadium impregnated on the SiO2–Ti4O9 support reduced ∼80% of the NO. Approximately the same conversion rate was generated on the catalyst (2VSiT) with 2 wt% vanadium using the same support. The increased NH3 adsorption demonstrate that introduction of silica in the catalyst promotes the NH3-SCR reaction. More importantly, 2VSiT and 1VSiT were strongly resistant to SO2 poisoning.