592 results about "Selective reduction" patented technology

A noninvasive method and apparatus for treating living tissue with pulsed electromagnetic fields (PEMFs) having selectively reduced high-frequency signal components, with improved bioresponse provided by magnetic field amplitudes less than approximately 40 μT, and most preferably in the range of 4–10 μT. Such amplitude levels for the disclosed PEMF signal are particularly effective with a treatment duration in the range of 0.25–2 hours/day.

A catalyst comprising a plurality of support nanoparticles and a plurality of catalytic nanoparticles. At least one catalytic nanoparticle is bonded to each support nanoparticle. The catalytic particles have a size and a concentration, wherein a first configuration of the size and the concentration of the catalytic nanoparticles enables a first catalysis result and a second configuration of the size and the concentration of the catalytic nanoparticles enables a second catalysis result, with the first and second configurations having a different size or concentration, and the first and second catalysis results being different. In some embodiments, the first catalysis result is a selective reduction of a first selected functional group without reducing one or more other functional groups, and the second catalysis result is a selective reduction of a second selected functional group without reducing one or more other functional groups.

A structured catalyst for selective reduction of nitrogen oxides with ammonia using an ammonia-supplying compound. The catalyst is preferably used for exhaust gas treatment of diesel vehicles powered by diesel motors. The catalyst is characterized by the fact that it contains a reduction catalyst for selective reduction of nitrogen oxides with ammonia and a hydrolysis catalyst for the hydrolysis of urea, where the hydrolysis catalyst is applied in the form of a coating onto the reduction catalyst. By this arrangement of the two catalytic functions in one catalyst the exhaust gas system can be made very compactly and space saving. Moreover, advantageous synergistic effects result from the direct contact of the hydrolysis catalyst and the reduction catalyst.

The present invention relates to method for selective reduction and derivatization of recombinantly prepared engineered proteins comprising at least one non-native cysteine, wherein the reduction reaction is conducted in the presence of a redox buffer or in the presence of a triarylphosphine reducing agent.

A method for producing a catalyst, in particular for the selective reduction of acetylenic compounds in hydrocarbon streams. An impregnation solution is provided, which contains a mixture of water and at least one water-miscible organic solvent as solvent in which at least one active metal compound and also preferably at least one promoter metal compound is dissolved. A support is provided, the support is impregnated with the impregnation solution, and the impregnated support is calcined. Palladium is preferably used as active metal and silver is preferably used as promoter metal. Also, a catalyst as is obtained by the method and also its preferred use for the selective hydrogenation of acetylenic compounds.

The invention discloses a technique for treating the tail gas of an acrylonitrile device, which is suitable for treating acrylonitrile tail gas discharged by the acrylonitrile device. The technique is characterized in that: after free water is separated out by a gas-liquid separator, the acrylonitrile tail gas is mixed with air, a noble metal monolithic catalyst is taken as a catalyst and catalytic oxidation reaction is carried out to turn harmful volatile organic compounds into carbon dioxide and water; then a selective reduction monolithic catalyst is taken as a catalyst and selective catalytic reduction reaction with added ammonia is carried out to reduce nitrogen oxide in the tail gas into nitrogen and water. The technique has the advantages of simple technique, turning the harmful volatile organic compounds and nitrogen oxide in the tail gas into carbon dioxide, nitrogen and water, without secondary pollution, the test results totally meeting the environmental protection control requirements of the State Standard of China, adopting a tail gas heat exchanger to recycle reaction heat to heat input tail gas, needing no additional fuel during the normal operation process, small system resistance and low operation cost.

A catalyst and a method for selectively reducing nitrogen oxides with ammonia are provided. The catalyst includes a first component of copper, chromium, cobalt, nickel, manganese, iron, niobium, or mixtures thereof, a second component of cerium, a lanthanide, a mixture of lanthanides, or mixtures thereof, and a zeolite. The catalyst may also include strontium as an additional second component. The catalyst selectively reduces nitrogen oxides to nitrogen with ammonia at low temperatures. The catalyst has high hydrothermal stability. The catalyst has high activity for conversion of nitrogen oxides in exhaust streams, and are not significantly influenced by the NO/NO₂ ratio. The catalyst and the method may have special application to selective reduction of nitrogen oxides in exhaust gas from diesel vehicles, although the catalyst and the method have broad application to a wide range of gas streams that contain nitrogen oxides. The temperature of exhaust gas from diesel vehicles is low, and the exhaust gas generally has a high NO/NO₂ ratio. Both the low temperature and the high NO/NO₂ ratio are challenging for selective catalytic reduction (SCR) catalysts.

An exhaust gas purifying apparatus and method for an internal combustion engine, and an engine control unit are provided for appropriately determining the amount of reducing agent supplied to a NOx selective reduction catalyst to ensure good exhaust gas characteristics. The exhaust gas purifying apparatus comprises an ECU; a NOx selective reduction catalyst for purifying NOx in exhaust gases in an exhaust pipe; a NOx sensor disposed in the exhaust pipe at a location downstream of the NOx selective reduction catalyst for detecting a NOx concentration in exhaust gases; and an injector for supplying the NOx selective reduction catalyst with ammonia produced in an ammonia production unit. The ECU determines the amount of ammonia injected to the NOx selective reduction catalyst by the injector such that an estimate of the NOx concentration detected by the NOx sensor reaches a minimum value.

According to one embodiment of the present invention a selective reduction catalyst system with a broad temperature window for lean-burn gasoline and diesel engines is disclosed. The system includes a first and second zone, wherein the first zone is composed of an iron SCR catalyst and a second zone is composed of a copper SCR catalyst, and wherein the second zone is positioned downstream of the first zone. In another embodiment, a small copper SCR catalyst is placed in front of a second zone composed of an iron SCR catalyst and a third zone composed of a copper SCR catalyst, wherein the volume of the first copper SCR catalyst is a fraction of the volume of the second copper SCR catalyst. In yet another embodiment, a diverter valve would be included in the system to eliminate any NO_x penalty produced by the front Cu SCR catalyst.

Ag/Al₂O₃ materials may be packaged in a suitable flow-through reactor, close coupled to the exhaust manifold of a diesel engine, and upstream of other exhaust gas treatment devices, such as a diesel oxidation catalyst and a selective reduction catalyst for NOx. The silver/alumina catalyst material uses hydrogen in a cold-start engine exhaust and serves to oxidize NO to NO₂ in the relatively low temperature, hydrocarbon-containing, exhaust during a short period following the engine cold start, and to temporarily store NOx during the start-up period. After the exhaust has heated downstream catalytic devices, the silver yields its nitrogen oxides for conversion to nitrogen by the then-operating devices before NOx is discharged to the atmosphere.

The object of the invention is to improve mountability on a vehicle by realizing a compact arrangement of a particulate filter 5 and selective reduction catalyst 6 while ensuring satisfactory reaction time for generation of ammonia from urea water. In an exhaust emission control device having particulate filter 5 incorporated in an exhaust pipe 4, selective reduction catalyst 6 capable of selectively reacting NO_x with ammonia under the presence of oxygen being arranged downstream of the particulate filter, urea water as reducing agent being adapted to be added between the selective reduction catalyst 6 and the particulate filter 5, the particulate filter 5 is arranged in parallel with the selective reduction catalyst 6. An S-shaped communication passage 9 is arranged for introduction of the exhaust gas 3 from a rear end of the particulate filter 5 to a front end of the adjacent selective reduction catalyst 6 in a forward folded manner. A urea water addition injector 11 is arranged midway of the communication passage 9.

In an exhaust emission control system of an internal combustion engine, a NOx selective reduction catalyst is disposed in an engine exhaust passage, and an aqueous solution of urea stored in an aqueous-urea tank is supplied to the NOx selective reduction catalyst so as to selectively reduce NOx. A NOx sensor is provided in the engine exhaust passage downstream of the NOx selective reduction catalyst for detecting the NOx conversion efficiency of the NOx selective reduction catalyst, and the concentration of aqueous urea in the aqueous-urea tank is estimated from the detected NOx conversion efficiency. The exhaust emission control system and method make it possible to detect the concentration of aqueous urea at reduced cost.

An exhaust aftertreatment system comprising a selective reduction catalyst, a NO_x sensor or an NH₃ sensor, a urea injector, and a dosing control unit, wherein the dosing control unit calculates the rate of urea injection by estimating the concentrations of NO and NO₂ in the exhaust downstream of the SCR catalyst.

An exhaust emission control device for an internal combustion engine, capable of supplying a just enough amount of reducing agent to a selective reduction catalyst even when a NOx purification ratio of the catalyst is changed by various causes, thereby enabling a high NOx purification ratio and very low exhaust emissions to be maintained. An ECU calculates a filtered value based on a signal from an exhaust gas concentration sensor, calculates a moving average value of a product of the filtered value and a reference input, calculates a control input such that the moving average value becomes equal to 0, and adds a reference input to the control input to calculate an FB injection amount. The ECU calculates an FF injection amount with a predetermined feedforward control algorithm, and adds the FF injection amount to the FB injection amount, to thereby calculate a urea injection amount.

An ammonia selective reduction-type NOx catalyst (48) is interposed in an exhaust passage of an engine (2) provided in a series-type hybrid electric vehicle (1), and a urea water injector (52) is disposed in the exhaust passage to supply a urea water into exhaust gas existing upstream of the ammonia selective reduction-type NOx catalyst (48). The engine (2) is started and stopped in accordance with the storage state of a battery (8), and the urea water injector (52) is controlled in accordance with the operating state of the engine (2). When the engine (2) is to be stopped, an adsorption increasing operation for increasing the amount of ammonia adsorbed by the ammonia selective reduction-type NOx catalyst (48) is executed over a predetermined period before the engine (2) is stopped.

Provided is a method of controlling a NOx purification system configured to reduce NOx contained in an exhaust gas by including an oxidation catalyst device (12) and a selective reduction type NOx catalyst device (14), which are arranged in this order from the upstream side, as well as the NOx purification system (1). The method and the system estimates whether a volume (Vn) of NO₂ adsorbed in the oxidation catalyst device (12) increases or decreases, and controls a flow rate (Vgb) of exhaust gas which bypasses the oxidation catalyst device (12) on the basis of the increase or decrease in the estimated volume (Vn) of adsorbed NO₂. Thereby, the method and the system avoid problems which occur due to shortage and excessive supply of ammonia by: estimating how much of NO₂ is adsorbed in the oxidation catalyst device; thus making the ratio of NO to NO₂ in NOx, which flows into the selective reduction type NOx catalyst device, closer to 1:1 as much as possible; and adding a necessary amount of ammonia-based solution.

An exhaust purification system for an internal combustion engine is provided that can steadily maintain a NOx purification rate of a selective reduction catalyst to be high without allowing the fuel economy or marketability to deteriorate. The exhaust purification system includes a NO₂—NOx ratio adjustment mechanism that causes a NO₂—NOx ratio to change; and a NO₂—NOx ratio perturbation controller that executes NO₂—NOx ratio perturbation control so that a NO₂ balance of the selective reduction catalyst in a predetermined time period, with NO₂ adsorption being positive and NO₂ release being negative, is 0. Herein, NO₂—NOx ratio perturbation control is defined as control that alternately executes NO₂ increase control to cause the NO₂—NOx ratio to be greater than a reference value near 0.5, and NO₂ decrease control to cause the NO₂—NOx ratio to be less than the reference value.