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AssigneeTosoh Corporation
InventorsYusuke NARAKI, Kou ARIGA, Hidekazu AOYAMA
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A first catalyst for reducing nitrogen oxides comprising a crystalline silicate containing an iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is 20-300 and at least 80% of the contained iron is an isolated iron ion Fe3+. A second catalyst for reducing nitrogen oxides comprising a crystalline silicate containing an iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is 20-300 and log (SiO2/Al2O3) by mol is at least 2. A predominant part of the contained iron is isolated iron ion Fe3+ and at least a part thereof preferably has a tetrahedral coordination. These catalysts have high hydrothermal stability and exhibit enhanced activity for reducing nitrogen oxides by a reaction with a reducing agent such as ammonia, urea or an organic amine in a broad temperature range between lower temperature and higher temperature.
A catalyst for reducing nitrogen oxides comprising a crystalline silicate containing iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is in the range of 20 to 300 and at least 80% of the contained iron is an isolated iron ion Fe3+.
A catalyst for reducing nitrogen oxides comprising a crystalline silicate containing iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is in the range of 20 to 300 and log(SiO2/Al2O3) by mol is at least 2.
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Processes characterised by a specific catalyst: for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a…
Catalysts comprising molecular sieves: ferrosilicates; Ferroaluminosilicates
Reductants: ammonium compounds
Transition metals: iron
Term end not estimated
This invention relates to reduction of nitrogen oxides in the exhaust gas from internal combustion engines. More particularly, it relates to a catalyst for reducing nitrogen oxides comprising a ferrosilicate having β-framework structure, and a process for reducing nitrogen oxides comprising reacting nitrogen oxides with at least one of ammonia, urea and an organic amine using the catalyst.
Silicates having a framework structure containing a substituted heteroatom are expected to have characteristics, different from those of ordinary aluminosilicate zeolites, and their usage for catalytic reaction has been investigating.
As specific examples of such ferrosilicates, a ferrosilicate having platinum supported thereon has been proposed as a catalyst for isomerization of xylene in Japanese Patent 3269828; an ferrosilicate has been proposed as a catalyst for selective methylation of naphthalene compounds in Japanese Translation of PCT International Application 2004-524142 (U.S. Pat. No. 7,022,637), and a method for producing polyalkylene glycol using a ferrosilicate as a catalyst for ring-opening polymerization of a cyclic ether in Japanese patent 3477799 (U.S. Pat. No. 5,648,558).
FIG. 1 is an ultraviolet-visible light absorption spectrum of β-type ferrosilicate 1 prepared in Example 3.
FIG. 2 is an electron spin resonance (ESR) spectrum of β-type ferrosilicate 1 prepared in Example 3, as analyzed before and after aging.
FIG. 3 is an electron spin resonance (ESR) spectrum of iron-loaded β zeolite prepared in Comparative Example 3, as analyzed before and after aging.
The catalyst for reduction of nitrogen oxides according to the present invention will be described in detail.
The β-type ferrosilicate 1 according to the present invention has a composition represented by following formula:
(x+y)M(2/n)O.xFe2O3.yAl2O3.zSiO2.wH2O