NH3 and urea in the selective catalytic reduction of NOx over oxide-supported copper catalysts

Abstract

Abstract.The temperature programmed activity of a series of oxide supported (TiO 2 , Al 2 O 3 and SiO 2 ) Cu catalysts formed from two different Cu precursors (Cu(NO 3 ) 2 and CuSO 4 ) for the selective catalytic reduction of NO x using solutions of urea as a reductant have been determined. These activities are compared to those found using NH 3 as a reducing agent over the same catalysts in the presence of H 2 O and it is found that catalysts that are active for the selective reduction of NO x with NH 3 are inactive for its reduction using solutions of urea. Poisoning of the surface by H 2 O ads is not responsible for all of this decrease in activity and it is postulated that the urea is not hydrolysing to form NH 3 over the catalysts but rather is oxidising to form N 2 or forming passivated layers of polymeric melamine complexes on the surface.

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

“…For instance, Sullivan et al [11] introduced water and solutions of urea from a calibrated syringe driver, which is technically rather far from the industrial conditions and not adapted to vaporization of low flow. Regarding Koebel et al [9], they used a modified prototype from Bosch as dosing unit for urea injection to achieve various model-based algorithms for urea dosage in the diesel engine.…”

“…Conversely, SCR is a continuous process. It is described as an attractive way to reduce NOx in excess of O2, with the possible use of a large choice of reductants like hydrocarbons (HC) [3][4][5][6][7][8], ammonia [9][10][11][12], urea [13], hydrogen, alcohol [14,15], etc. While HC-SCR has been largely studied in the past decades for automotive applications, the NH3-SCR is now accepted as exhibiting the highest potential to reduce NOx emission in the lean condition, with different reaction pathways described by Equations (1)- (3).…”

Design and Implementation of Mixing Chambers to Improve Thermal Decomposition of Urea for NOX Abatement

“…Many previous studies have shown that it has ideal performance in NO X conversion efficiency compared with that of urea-SCR. Sullivan and Doherty (2005) showed that NO X conversion with the H 2 O-urea-SCR is lower than that of the H 2 O-NH 3 -SCR using Cu-Al 2 O 3 and Cu-TiO 2 SCR catalysts. Koebel and Strutz (2003) presented that the NO X conversion of the NH 3 -SCR is better than that of the urea-SCR.…”

Preparation of Ni‐Based Metal Monolithic Catalysts and a Study of Their Performance in Methane Reforming with CO2

“…[1][2][3] Thus, methane reforming with CO 2 to synthesis gas has gained considerable attention in the field of catalysis. [4][5][6] Noble metals (Pt, Rh, Ru, Pd) exhibit a good level of activity and selectivity in methane reforming reactions with CO 2 , [7][8][9] however, their restricted availability and high cost make them unsuitable for industrial-scale operation. In recent years, supported nickel-based catalysts have attracted increasing interest owing to their similar activity to noble-metal catalysts and low costs.…”