摘要:
A catalyst and a process for selective catalytic reduction of nitrogen oxides in diesel engine exhaust gases with ammonia or a compound decomposable to ammonia are described. The exhaust gas to be cleaned is passed together with ammonia or a compound decomposable to ammonia over a catalyst which comprises a zeolite or a zeolite-like compound containing 1-10% by weight of copper, based on the total weight of the zeolite or of the zeolite-like compound, and a homogeneous cerium-zirconium mixed oxide and/or a cerium oxide. The zeolite used or the zeolite-like compound used is selected from the group consisting of chabazite, SAPO-34, ALPO-34 and zeolite-β.
摘要:
A catalyst for the selective catalytic reduction of nitrogen oxides in diesel engine exhaust gases using ammonia or a precursor compound decomposable to ammonia. The catalyst includes two superposed coatings applied to a support body, of which the first coating applied directly to the support body includes a transition metal-exchanged zeolite and/or a transition metal-exchanged zeolite-like compound, and effectively catalyzes the SCR reaction. The second coating is applied to the first coating to cover it on the exhaust gas side and prevent hydrocarbons having at least three carbon atoms present in the exhaust gas from contacting the first coating, without blocking the passage of nitrogen oxides and ammonia to the first coating. The second coating may be formed from small-pore zeolites and/or small-pore, zeolite-like compounds, and from suitable oxides, especially silicon dioxide, germanium dioxide, aluminum oxide, titanium dioxide, tin oxide, cerium oxide, zirconium dioxide and mixtures thereof.
摘要:
The invention relates to a catalytically active material for reacting nitrogen oxides with ammonia in the presence of hydrocarbons. The material consists of an inner core (1) made of a zeolite exchanged with one or more transition metals or a zeolite-like compound exchanged with one or more transition metals. The core of the catalytically active material is encased by a shell (2), which is made of one or more oxides selected from silicon dioxide, germanium dioxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, zirconium dioxide, and mixed oxides thereof.
摘要:
A process for improving catalytic activity of a copper-promoted zeolitic catalyst with a chabazite structure, the copper-promoted zeolitic catalyst having a temperature-programmed reduction (TPR) signal in a temperature range from 230° C. to 240° C. as examined in a TPR with a test gas having a hydrogen content of 5% by volume, a heating rate of 10 K/min, and a catalyst sample weight containing from 3 to 8 milligrams of copper calculated as metal.
摘要:
The invention relates to the use of mixed oxides made of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide as catalytically active materials for the selective catalytic reduction of nitrogen oxides with ammonia or a compound that can decompose to form ammonia in the exhaust gas of internal combustion engines in motor vehicles that are predominantly leanly operated, and to compositions or catalysts which contain said mixed oxides in combination with zeolite compounds and/or zeolite-like compounds and are suitable for the denitrogenation of lean motor vehicle exhaust gases in all essential operating states.
摘要:
The invention relates to the use of mixed oxides made of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide as catalytically active materials for the selective catalytic reduction of nitrogen oxides with ammonia or a compound that can decompose to form ammonia in the exhaust gas of internal combustion engines in motor vehicles that are predominantly leanly operated, and to compositions or catalysts which contain said mixed oxides in combination with zeolite compounds and/or zeolite-like compounds and are suitable for the denitrogenation of lean motor vehicle exhaust gases in all essential operating states.
摘要:
The invention relates to a catalytically active material for reacting nitrogen oxides with ammonia in the presence of hydrocarbons. The material consists of an inner core (1) made of a zeolite exchanged with one or more transition metals or a zeolite-like compound exchanged with one or more transition metals. The core of the catalytically active material is encased by a shell (2), which is made of one or more oxides selected from silicon dioxide, germanium dioxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, zirconium dioxide, and mixed oxides thereof.
摘要:
A catalyst for the selective catalytic reduction of nitrogen oxides in diesel engine exhaust gases using ammonia or a precursor compound decomposable to ammonia is described. The catalyst comprises two superposed coatings applied to a support body, of which the first coating applied directly to the support body comprises a transition metal-exchanged zeolite and/or a transition metal-exchanged zeolite-like compound, and effectively catalyzes the SCR reaction. The second coating has been applied to the first coating so as to cover it on the exhaust gas side. It is configured so as to prevent the contact of hydrocarbons having at least three carbon atoms present in the exhaust gas with the layer beneath, without blocking the passage of nitrogen oxides and ammonia to the first coating. The second coating may be formed from small-pore zeolites and/or small-pore zeolite-like compounds, and from suitable oxides, especially silicon dioxide, germanium dioxide, aluminum oxide, titanium dioxide, tin oxide, cerium oxide, zirconium dioxide and mixtures thereof. As well as the catalyst, routes for production thereof are described.
摘要:
The present invention relates to a process for improving the catalytic activity of a copper-promoted zeolitic catalyst with chabazite structure, to a copper-promoted zeolitic catalyst with chabazite structure and to a process for reducing nitrogen oxides in an offgas stream.
摘要:
The invention relates to a process for treating diesel engine exhaust gases comprising nitrogen oxides (NOx) and hydrocarbons (HC) by selective catalytic reduction of the nitrogen oxides with ammonia or a compound decomposable to ammonia as a reducing agent over an SCR catalyst based on a molecular sieve. The properties of the catalyst used are such that the hydrocarbons present in the exhaust gas are kept away from the catalytically active sites in the catalyst over which the reactions take place by the molecular sieve-like action of the zeolite present in the catalyst. This prevents HC-related degradation and aging effects of the SCR catalyst and achieves a considerable improvement in nitrogen oxide conversions in HC-containing exhaust gas.