3747 results about "Selective catalytic reduction" patented technology

Catalysts and catalytic articles for treating exhaust gas streams are described. In one or more embodiments, a catalyst system includes a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons. Methods for treating the exhaust gas stream are also provided. Methods of making and using such catalysts and catalytic articles are also described.

A NOx abatement system comprising: a first NOx adsorber (18) capable of being disposed in-line and downstream of and in fluid communication with an engine (12); a selective catalytic reduction catalyst (20) disposed in-line and downstream of and in direct fluid communication with the first NOx adsorber (18), wherein the selective catalytic reduction catalyst (20) is capable of storing ammonia; and an off-line reformer (24) disposed in selective communication with and upstream of the first NOx adsorber (18) and the selective catalytic reduction catalyst (20), wherein the reformer (24) is capable of producing a reformate comprising primarily hydrogen and carbon monoxide.

A reductant delivery unit (10) is provided for selective catalytic reduction (SCR) after-treatment for vehicles. The unit includes a solenoid fluid injector (10) constructed and arranged to be associated with an exhaust gas flow path (14) upstream of a SCR catalytic converter (17). The fluid injector has a fluid inlet (13) and a fluid outlet (15) with the fluid inlet being constructed and arranged to receive a source of urea solution and the fluid outlet being constructed and arranged to communicate directly with the exhaust flow path so as to control injection of urea solution into the exhaust gas flow path. An interface (24) is constructed and arranged to couple the fluid injector to the gas flow path. The interface defines a thermal barrier constructed and arranged to decoupled a body of the injector from exposure to heat in the exhaust gas flow path.

A reductant dosing control system, for use in a Selective Catalytic Reduction (SCR) system of a motor vehicle includes an input receiving a NOx feedback signal from an NOx sensor provided to the SCR system. A base dosing module calculates a required quantity of reductant to inject in front of a SCR catalyst of the SCR system based on the NOx feedback signal. The SCR catalyst has ammonia storage properties. An output signals a reductant metering mechanism to periodically or continuously inject excess reductant based on the required quantity of reductant.

The invention discloses recovery process of honeycomb type selective catalytic reduction (SCR) waste catalyst. The process includes the following steps: a, preprocessing the SCR waste catalyst and leaching at the high temperature and under high pressure; b, adding hydrochloric acid into leaching liquid, adjusting pH, and removing impurities; c, adding hydrochloric acid into the leaching liquid, reacting, calcining and preparing rutile titanium dioxide; d, preparing ammonium paratungstate; e, preparing ammonium metavanadate; and f, recycling and treating waste water. Main products of ammonium paratungstate, ammonium metavanadate and rutile titanium dioxide obtained in the process are high in purity and recovery rate. By-products of silicon magnesium slags, salty mud, high-concentration sodium chloride liquid and barium sulfate dregs are high-purity harmless useful goods. The process is free of harmful secondary pollutant emission, environment-friendly and capable of circulating, has high economical and social benefit and is practicable.

A composite oxide catalyst for removing NOx from the tail gas generated by combustion through low-temp selective catalytic reduction reaction in which ammonia gas or urea is used as reducing agent for reducing the NOx into N2 and H2O is prepared from a composite metallic oxide (whose main component is manganese oxide) and a porous inorganic oxide as carrier through citric acid complexing method.

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO₂, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N₂O was not detected (detection limit: 0.6 percent N₂O).

A preferred process arrangement utilizes the enthalpy of the flue gas, which can be supplemented if need be, to convert urea (30) into ammonia for SCR. Urea (30), which decomposes at temperatures above 140 ° C., is injected (32) into a flue gas stream split off (28) after a heat exchanger (22), such as a primary superheater or an economizer. Ideally, the side stream would gasify the urea without need for further heating; but, when heat is required it is far less than would be needed to heat either the entire effluent (23) or the urea (30). This side stream, typically less than 3% of the flue gas, provides the required temperature and residence time for complete decomposition of urea (30). A cyclonic separator can be used to remove particulates and completely mix the reagent and flue gas. This stream can then be directed to an injection grid (37) ahead of SCR using a blower (36). The mixing with the flue gas is facilitated due to an order of magnitude higher mass of side stream compared to that injected through the AIG in a traditional ammonia-SCR process.

The invention discloses a method for extracting tungsten, titanium and vanadium from a waste SCR (selective catalytic reduction) catalyst, which comprises the following steps: crushing the waste SCR catalyst, adding a strongly alkaline solution, and reacting; filtering, separating, then adding strong acid into the sodium tungstate and sodium vanadate mixed solution, and reacting to obtain tungstic acid and a sodium salt and vanadic acid mixed solution; regulating the pH value of the sodium salt and vanadic acid mixed solution until precipitate is separated out, thus obtaining ammonium vanadate; then adding sulfuric acid into the tungsten-and-vanadium-removed SCR catalyst, and reacting to obtain a titanyl sulfate solution and solids such as aluminum slag and the like; then adding water into the titanyl sulfate solution, and hydrolyzing to obtain titanic acid and a waste acid solution; and finally, respectively calcining the obtained ammonium vanadate, tungstic acid and titanic acid to obtain vanadium pentoxide, tungsten trioxide and titanium dioxide. According to the invention, tungsten, titanium and vanadium can be extracted from the SCR catalyst through the reaction with strong alkali and strong acid at a low temperature, the equipment requirement is low, the energy consumption is low, some products having added values can be coproduced, and no secondary pollution is generated, thereby facilitating popularization and application.

One aspect of the invention relates to an exhaust treatment apparatus having an NOx reduction system comprising first and second catalyst beds in series with associated first and second ammonia injectors. The first catalyst bed with its associated ammonia injector preferably targets removing only about 80 to about 95% percent of the NOx in the vehicle exhaust. The second catalyst bed with its associated injector preferably target removing about 70 to about 100% of the remaining NOx. Staging the reduction system in this manner improves control over NOx reduction and reduces the risk of ammonia slip. Other aspects of the invention relate to methods of treating vehicle exhaust to remove NOx and an SCR reactor comprising a housing having an entrance port, an exit port, and an ammonia injection port, wherein the injection port is configured to inject ammonia in between SCR catalyst beds contained in the housing.

An exhaust treatment system includes a catalyzed particulate filter disposed in a first passageway and configured to receive a first portion of a flow of exhaust. The catalyzed particulate filter is at least partially coated with a catalytic material for converting NO to NO₂. The exhaust treatment system also includes a second passageway configured to direct a second portion of the flow of exhaust around the catalyzed particulate filter and a selective catalytic reduction device disposed downstream from the first passageway and the second passageway. The selective catalytic reduction device is configured to receive a combined flow of exhaust including the first and second portions of the flow of exhaust.

An exhaust gas treatment system includes an exhaust passage through which exhaust gas from an internal combustion engine is allowed to flow, a selective catalytic reduction catalyst provided in the exhaust passage, a mixing chamber provided upstream of the selective catalytic reduction catalyst in the exhaust passage as viewed in the direction of exhaust gas flow, a fuel injection valve for injection of fuel, an air injection valve for injection of air, and a urea water injection valve for injection of urea water. The fuel injection valve, the air injection valve and the urea water injection valve each has an injection port directed to the mixing chamber.

Embodiments are described to improve the durability of a lean NO_x aftertreatment system. According to one embodiment of the present invention an air injection system is used to inject air continuously into the exhaust system between the upstream three-way catalyst and the downstream selective catalytic reduction (SCR) catalyst when the engine is operating at stoichiometric or rich air/fuel ratios and the exhaust temperatures are above a calibratible level (e.g., 700° C.). In another embodiment, an oxidation catalyst is positioned downstream of the air injection point to prevent exothermic reactions from occurring on the SCR. In another embodiment, the reductant for the SCR is generated in-situ. In yet another embodiment, a diverter valve with a reduction catalyst in a bypass arm is utilized to bypass the SCR during high load conditions.

The invention relates to a method for recovering tungsten trioxide and ammonium metavanadate from a selective catalytic reduction (SCR) denitration catalyst. The method comprises the following steps of: crushing the SCR denitration catalyst, sieving to obtain catalyst powder, mixing with sodium carbonate, and stirring fully and uniformly; putting the mixed powder into a sintering furnace, and sintering to obtain a sintered material; keeping temperature for 1 hour, and sieving to obtain sintered material powder; pouring warm water, so that Na2WO4 and NaVO3 in the sintered material powder are dissolved fully, filtering, and removing precipitates to obtain a mixed solution of Na2WO4 and NaVO3; regulating the pH value to be 6.5-7.5, adding an ammonium bicarbonate solution or an ammonium chloride solution, and precipitating ammonium metavanadate precipitate; filtering, washing by using a diluted ammonium bicarbonate solution for 2 to 3 times, washing by using 30 percent ethanol for 1 to 2 times, and drying to obtain an ammonium metavanadate finished product; and converting the Na2WO4 in the residual solution into ammonium paratungstate, evaporating the residual solution to obtain ammonium paratungstate crystals, and calcining to obtain the tungsten trioxide. By the method, the ammonium metavanadate and the tungsten trioxide can be recovered, and the discharge of pollutants is reduced.