The open literature concerning chemical and mechanistic aspects of the selective catalytic reduction of NO by ammonia (SCR process) on metal oxide catalysts is reviewed. Catalytic systems based on supported V2O5 (including the industrial TiO2-supported V2O5–WO3 and/or V2O5–MoO3 catalysts) and catalysts containing Fe2O3, CuO, MnOx and CrOx are considered. The results of spectroscopic studies of the adsorbed surface species, adsorption–desorption measurements, flow reactor and kinetic experiments are analyzed. The proposed reaction mechanisms are described and critically discussed. Points of convergence and of disagreement are underlined.

Chemical and mechanistic aspects of the selective catalytic reduction of NOx by ammonia over oxide catalysts: A review

https://chemistry.mdma.ch/hiveboard/rhodium/pdf/indole.synth.review.1994-99.pdf

Recent developments in indole ring synthesis—methodology and applications

Performance and kinetics study for low-temperature SCR of NO with NH3 over MnOx–CeO2 catalyst

A series of catalysts of manganese oxide supported on TiO 2 and iron–manganese oxide supported on TiO 2 with different amounts of manganese and iron were studied for low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. It was found that the addition of iron oxide not only increased the NO conversion and N 2 selectivity but also increased the resistance to H 2 O and SO 2 . The Fe–Mn/TiO 2 catalysts yield high activities and high N 2 product selectivity. The N 2 O product selectivity increased with the amount of MnO x as well as temperature. Crystalline phase of MnO x was present at ≥15% Mn on TiO 2 , and the amount increased with Mn content. In addition, SO 2 and H 2 O decreased the activities only slightly, while such effect was reversible. The Fe–Mn/TiO 2 with Mn/Fe=1 showed the highest activity. The results showed that this catalyst yielded nearly 100% NO conversion at 120 °C at a space velocity of 15,000 h −1 . The effect of oxygen was also studied. Reversible transient behaviors similar to that on other oxide catalysts, including vanadia and chromia, were observed for the Fe–Mn/TiO 2 catalyst.

Low-temperature selective catalytic reduction of NO with NH3 over iron and manganese oxides supported on titania

TiO2-supported metal oxide catalysts for low-temperature selective catalytic reduction of NO with NH3. I. Evaluation and characterization of first row transition metals

A catalyst compositions for reducing nitrogen oxide comprising, as its chief ingredient, an intimate mixture of A. titanium (Ti) as component A, with B. at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), iron (Fe), vanadium (V), nickel (Ni), cobalt (Co), copper (Cu), chromium (Cr), and uranium (U), as component B, in the form of their oxides, and a process for reducing nitrogen oxides to nitrogen, which comprises contacting a gaseous mixture containing nitrogen oxides and molecular oxygen and a reducing gas with aforesaid catalyst compositions at an elevated temperature.

Catalytic process for reducing nitrogen oxides to nitrogen

The reduction of NO with NH/sub 3/ on iron oxide-titanium oxide was studied by using a flow reactor between 250 and 450/sup 0/C. It was found that NO reacts with NH/sub 3/ at a 1:1 mole ratio in the presence of excess O/sub 2/ and the reaction is completely inhibited by the absence of O/sub 2/. The formation of N/sub 2/O, if any, was negligible in all experiments. The experimental data show that the NO-NH/sub 3/ reaction in the presence of O/sub 2/ is represented by NO + NH/sub 3/ + 1/4 O/sub 2/ = N/sub 2/ + 3/2 H/sub 2/O.

Reduction of nitric oxide with ammonia on iron oxide-titanium oxide catalyst

A denitration catalyst comprising at least three metal components, (A) titanium, (B) tungsten and/or magnesium, and (C) vanadium, the titanium and tungsten being contained as oxides and the magnesium and vanadium being contained in the form of an oxide or a sulfate or both, said catalyst being composed of a porous molded article of a mixture of an oxide of component A and an oxide and/or a sulfate of component B, the atomic ratio of component B to component A being from 0.01 to 1, and a vanadium compound localized in that area of said molded article which extends from its outermost surface to a depth of 500 microns or less, the content of the vanadium compound in said area being 0.1 to 15% by weight; and a method for removing nitrogen oxides from a waste gas, which comprises contacting a waste gas containing nitrogen oxides, together with ammonia and molecular oxygen, at a temperature of 150° to 650° C., with the aforesaid catalyst.

Denitration catalyst and denitrating method

Verfahren zur reduktion von stickstoffoxiden zu stickstoff und katalysatormassen hierfuer

An ammonia gas to be determined, and an oxidative gas containing nitrogen oxides in moles more than those of the ammonia are brought into contact with an analytical catalyst capable of forming nitrogen and water from ammonia and nitrogen oxides. Concentrations of nitrogen oxides of the gas before and after the contact with the analytical catalyst are determined, and an ammonia concentration of the gas is determined by converting the difference between the concentrations of nitrogen oxides to the ammonia concentration by calculation.

Makoto Imanari

Papers

Catalytic process for reducing nitrogen oxides to nitrogen

Reduction of nitric oxide with ammonia on iron oxide-titanium oxide catalyst

Denitration catalyst and denitrating method

Verfahren zur reduktion von stickstoffoxiden zu stickstoff und katalysatormassen hierfuer

Method and apparatus for determining ammonia concentration of gas