Siemens Aktiengesellschaft

Frank Witzel

G&uuml;nther Pajonk

Stefan Fischer

Ronald Neufert

Wieland Mathes

Thomas Hammer

Lothar Hofmann

Günther Pajonk

Steffen Schnapp

Andreas Girschik

Stefan Br&ouml;er

To reduce the number of particles in an exhaust gas (A), in particular in the exhaust gas (A) from an internal-combustion engine, sulfur dioxide SOwhich is contained in the exhaust gas (A) is at least partially catalytically oxidized, in the presence of ammonia NHin a catalytic converter system having a catalytic activity which increases in the direction of flow, to form sulfur trioxide SO. The simultaneous presence of sulfur trioxide SOand ammonia NHin the exhaust-gas stream which is brought about in this way results in an agglomeration of the small and very small particles and reduction in the number thereof.

Method and device for reducing the number of particles in an exhaust gas

The invention relates to a catalytic converter and a method for cleaning the exhaust gas from an internal combustion engine which is operated with excess air. The catalytic converter has an active material made from the oxides TiO , V O , CaO and SiO , as well as WO and/or MoO . An active material of this type has the property of using the SCR method to reduce to equal extents the levels of nitrogen oxides and hydrocarbons. The CO oxidation activity of a material of this type can be increased by metering in elements selected from the group consisting of Pt, Pd, Rh, Ru and Ir in any desired inorganic form.

Catalytic converter and method for cleaning exhaust gas

Catalyst body for breaking down halogenated hydrocarbons, in particular dioxins and/or furans, having an active material which comprises titanium dioxide, carbon and at least one active component which is selected from the group consisting of oxides and mixed oxides of the transition metals, of the lanthanides, of the actinides, of the alkali metals and alkaline-earth metals, of aluminum, of tin and of silicon. In an off-gas flowing through the catalyst body, the levels of hydrocarbons contained therein are effectively reduced in part by adsorption and in part by oxidation, in particular at temperatures below 250&deg; C.

Process for reducing the levels of halogenated hydrocarbons

A process for producing a catalyst body includes providing titanium dioxide, tungsten trioxide, vanadium pentoxide, aluminum oxide, and/or silicon oxide for the catalyst body. A kneadable and/or shapable compound is processed to form a shaped body by extrusion or by coating of a support body. The shaped body is dried and is calcined to form an active compound. The calcined shaped body is artificially aged by a final heat treatment at a temperature higher than the calcination temperature to produce a catalyst body having a high resistance to deactivation at high temperatures. The starting materials include from 65 to 95% by weight of titanium dioxide, 2 to 30% by weight of tungsten trioxide, 0 to 2% by weight of vanadium pentoxide, preferably, less than 1.5%, 0.1 to 10% by weight of aluminum oxide, and 0.1 to 10% by weight of silicon dioxide. The final heat treatment is done is at 660 to 700&deg; C., drying is at 20 to 100&deg; C. prior to calcination, and calcination is at 400&deg; C. to less than 700&deg; C.

Process for producing a catalyst body

A gas stream that contains nitrogen oxides is passed, in the presence of a reducing agent, over a catalyst body with an active material that contains a zeolite and titanium dioxide. The zeolite is a hydrogen-ion-exchanged, acid zeolite. Even at temperatures above 450&deg; C., the nitrogen oxides contained are still effectively converted into nitrogen and water.

Catalyst body and process for breaking down nitrogen oxides

A configuration for decomposing nitrogen oxides in a gas stream includes a plurality of catalytic converters disposed one after the other through which the gas stream can flow. Each of the catalytic converters has a honeycomb structure with many parallel cells through which the gas stream can flow. Each of the catalytic converters also has a predetermined cell density and a predetermined average level of activity defined as a proportion by weight of the catalytically active agent. The predetermined cell density of a second catalytic converter through which the gas stream flows after a first catalytic converter is lower than the predetermined cell density of the first catalytic converter. The predetermined average level of activity of the second catalytic converter is also higher than the predetermined average level of activity of the first catalytic converter. The configuration is preferably used in conjunction with an exhaust gas from a combustion drive unit.

Configuration for decomposing nitrogen oxides in a gas stream and method for using the configuration

To produce a catalytically active material, titanium dioxide, together with an oxide or with a dissolved compound of tungsten and/or vanadium, is processed into a shapeable material. the shapeable material is dried to form a shaped body, and the shaped body is calcined. After the calcining, the shaped body is additionally impregnated with a dissolved compound of titanium and vanadium and is dried again. A catalytically active material of this type has a high catalytic activity with regard to breaking down dioxins and/or furans even in a temperature range of below 250&deg; C. The catalytically active material is particularly suitable for producing dioxin and/or furan catalytic converters.

PROCESS FOR PRODUCING A CATALYTICALLY ACTIVE MATERIAL, CATALYTIC CONVERTER HAVING A CATALYTICALLY ACTIVE MATERIAL PRODUCED IN THIS MANNER, AND USE OF THE CATALYTIC CONVERTER TO BREAK DOWN DIOXINS AND/OR FURANS

An injection device for a reducing agent, a mixing device and a catalyst device are provided in an exhaust pipe. The mixing device is disposed upstream of the injection device as seen in the direction of flow of the exhaust gas. An exhaust gas inlet pipe is connected to the exhaust pipe along the main axis of the exhaust pipe. A first level of the catalyst device may advantageously be a hydrolysis-catalyst module, while the other levels may be SCR catalyst modules.

Exhaust emission control system for the exhaust gas of a diesel engine

A catalyst body, which contains a number of passages through which a medium can flow in a preferred direction, is to be able to operate reliably with little cleaning outlay. It is also intended for cracking during the process of manufacturing the catalyst body to be particularly rare. For this purpose, each passage, disposed at right angles to the preferred direction, is approximately rectangular in cross section, as defined by a longitudinal side and a shorter transverse side. The number of passages per unit surface area lies in the range from 0.5 to 2.5 cm,, and the longitudinal sides of a first group of the passages are disposed approximately at right angles to the longitudinal sides of a second group of the passages. The passages are in this case combined to form subgroups, the passages of each subgroup, in terms of their cross sections, forming an approximately square configuration, and each subgroup containing in each case passages from the same group.

Catalyst body

To clean the exhaust gas of internal-combustion engines or other machines which are operated with fossil fuel, it is proposed to firstly pretreat the exhaust gas in a non-thermal normal-pressure gas discharge and subsequently allow a selective catalytic reduction of oxidic noxious substances to take place with the addition of a suitable reduction substance, or to allow a selective catalytic decomposition to take place. The device for removing the oxidic noxious substances is characterized by a series circuit of at least one module with a gas discharge section and at least one module with a catalytic-converter section, and is suitable in particular for use in a diesel engine.

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Bloomfield Hills, MI, United States of America

Frank Witzel