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

Catalytic removal of NO

Removal of nitrogen monoxide from exhaust gases through novel catalytic processes

(Article begins on next page) Anyone can freely access the full text of works made available as \"Open Access\". Works made available under a Creative Commons license can be used according to the terms and conditions of said license. Use of all other works requires consent of the right holder (author or publisher) if not exempted from copyright protection by the applicable law. Availability: This is the author's manuscript

/pdf/reactivity-of-surface-species-in-heterogeneous-catalysts-1vtf7rqr9y.pdf

Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

A predominant challenge to both industrial and academic research institutions is the selective reduction of NOx during lean exhaust conditions. Despite a proliferation of publications, papers and reviews, a large number of catalysts fall short of a credible and consistent diesel application. Herein are reviewed systems designed specifically with the goal of assisting researchers in their assessment of catalytic performance. By way of conclusion, three principal types of catalysts active for HC-SCR are discussed.

The current state of research on automotive lean NOx catalysis

Cu-ZSM-5 zeolite as highly active catalyst for removal of nitrogen monoxide from emission of diesel engines

Among various metal ion-exchanged zeolites, metal loading alumina, and oxides, iron ion-exchanged mordenite was the most active for the selective reduction of nitrogen monoxide to nitrogen by ethene in the presence of oxygen at the temperature as low as 473 K. The catalytic activities of iron ion-exchanged zeolites depended on the zeolite structure and the iron ion exchange level. The effects of the zeolite structure are in the order of MOR > FER > MFI > Y > LTL at 473 K. The activity of iron ion-exchanged mordenite increased with the increment in the exchange level and levelled off above about 60%.

Iron ion-exchanged zeolite: the most active catalyst at 473 K for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere

There is provided a filtering means regenerating system for a diesel engine, in which the filtering means provided in an exhaust gas passage oxidizes NO in exhaust gas of the engine into NO 2 , and collects particulates in exhaust gas to thereby oxidize the particulates by NO 2 and remove the same at a temperature higher than a predetermined exhaust gas temperature. Also, an in-line fuel injection system for injecting fuel into the engine is provided with a variable timer mechanism for regulating the injection timing of fuel, and the deposit of particulates deposited on the filtering means is detected by deposit detecting means. A controller controls the variable timer mechanism based on the detection output of the deposit detecting means. The filtering means is prevented from becoming in an excessively collecting state in all operation statuses of the engine, thereby preventing a decrease in fuel economy and power performance of the engine.

Filtering means regenerating system for diesel engine

The Study of NOx and PM Reduction Using Urea Selective Catalytic Reduction System for Heavy Duty Diesel Engine

PROBLEM TO BE SOLVED: To successively execute favorable reduction and purification of NOx even under conditions of drop in urea water to less than the necessary minimum amount (less than a set lower limit value of a level sensor) and of abnormality in concentrations. SOLUTION: A reducing agent supply device for supplying reducing agent to a selection reduction type catalyst 10 provided at some midpoint in an exhaust pipe 9, is equipped with a urea water tank 14 for storing urea water 11 as reducing agent for regular use, a fuel tank 18 for storing light oil 12 as an engine fuel and an injection device 19 for selectively leading the urea water 11 or light oil 12 from either of the urea water tank 14 or fuel tank 18 through the medium of a three-way switch valve 17 (a flow path switching means) and injecting the urea water 11 or light oil 12 to the inlet side of the selective reduction catalyst 10. COPYRIGHT: (C)2006,JPO&NCIPI

Shinya Sato

Papers

Cu-ZSM-5 zeolite as highly active catalyst for removal of nitrogen monoxide from emission of diesel engines

Iron ion-exchanged zeolite: the most active catalyst at 473 K for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere

Filtering means regenerating system for diesel engine

The Study of NOx and PM Reduction Using Urea Selective Catalytic Reduction System for Heavy Duty Diesel Engine

Reducing agent supply device