Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

Abstract

Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

Controlling Catalytic Selectivity Mediated by Stabilization of Reactive Intermediates in Small-Pore Environments: A Study of Mn/TiO2 in the NH3-SCR Reaction

“…These microporous TiO 2 particles have a fine pore structure (pore size of less than 1 nm, similar to zeolite), which seems to be formed by Li + intercalation. Details of the synthetic method for microporous TiO 2 have been reported previously . Before Mn impregnation, it was confirmed that there was no residual Li ion on the as-synthesized microporous TiO 2 from the ICP-AES results.…”

“…Microporous structure inside TiO 2 particle was made using the hydrothermal synthesis method as previously reported. 21 In a typical synthesis, 70.5 g of lithium hydroxide (Aldrich, >98%) and 6.4 g of anatase titanium(IV) oxide (Aldrich, >99.8%) were mixed in 141 mL of deionized H 2 O and vigorously stirred at room temperature for 2 h. The mixture was transferred to a 200 mL Teflon cup and placed in a stainless-steel autoclave. The autoclave was then heated at 127 °C for 30 h in a rotating oven with a speed of 17 rpm.…”

“…It is necessary to regulate N 2 O emissions because it has a high greenhouse gas (GHG) potential (∼300 times higher than that of CO 2 ) . Commercial SCR catalysts, including V 2 O 5 –WO 3 /TiO 2 and Cu-zeolites, also release N 2 O during the SCR reaction. − While V 2 O 5 –WO 3 /TiO 2 catalysts release a negligible amount of N 2 O under standard SCR, they emit a small amount of N 2 O under NO 2 -rich conditions. , In the case of Cu-zeolites, only a slight amount of N 2 O is released at low temperatures (below 300 °C), although more N 2 O is formed under NO 2 -rich conditions . The type of zeolite framework also affects the generation of N 2 O; for example, Cu-CHA having a cage opening smaller than that of Cu-BEA shows lower N 2 O formation.…”

Chemisorption of NH3 on Monomeric Vanadium Oxide Supported on Anatase TiO2: A Combined DRIFT and DFT Study

“…Vanadium oxide supported on anatase titania catalyst (VO x /TiO 2 ) is active for various reactions including selective oxidation or reduction. − It has been well known as a conventional catalyst used in the selective catalytic reduction (SCR) process, which selectively reduces harmful NO x with NH 3 in lean conditions. − Many studies have been performed to investigate structure–activity relationship in VO x /TiO 2 catalyst, where it is widely accepted that the degree of polymerization of vanadia on TiO 2 is a key factor that determines the activity or selectivity in the reaction. , …”

Simple physical mixing of zeolite prevents sulfur deactivation of vanadia catalysts for NOx removal

“…water. 1 g of a microporous TiO 2 support (Lab made) 33 was added into the precursor solution and stirred for 30 min. The solution with microporous TiO 2 support was dehydrated by using a rotary evaporator and completely dried at 105 °C overnight.…”