Isolated Metal Species in Metal-Zeolite Catalytic Material for Low Temperature Scr of Nox with Nh3

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This patent describes a novel synthesis method for creating iron-zeolite (specifically Fe/ZSM-5) catalysts with a very high proportion of isolated iron atoms, rather than clusters or particles. Isolated iron species show superior effectiveness in reducing nitrogen oxides (NOx) using ammonia at low temperatures. The method involves dealumination of ZSM-5 zeolite followed by incorporation of a stabilized iron-EDTA complex, resulting in a catalyst with enhanced low-temperature performance and improved redox activity.

Use CasesContent extracted from patent full text and abstract with AI.

• Automotive exhaust treatment systems (diesel and gasoline engines) for reducing NOx emissions
• Industrial flue gas treatment for NOx abatement in power plants and factories
• Retrofit applications to improve efficiency of existing SCR (Selective Catalytic Reduction) reactors
• Catalyst systems for ships and locomotives subject to stringent emission regulations
• Stationary source emission control, including incinerators and chemical plants

BenefitsContent extracted from patent full text and abstract with AI.

• Significantly improved activity and selectivity for NOx removal at lower temperatures compared to conventional iron-zeolite catalysts
• Enhanced understanding and control of the active site structure due to high isolated iron content
• Reduced formation of unwanted byproducts such as N2O due to higher selectivity
• Potential for lower noble metal usage (cost savings), as iron is abundant and inexpensive
• Enables compliance with stricter environmental regulations due to higher NOx conversion efficiencies
• Greater catalyst durability and stability since the active iron species are less prone to agglomeration and deactivation

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Patent Abstract

Iron zeolites have been intensively studied as promising catalytic systems for reduction of nitrogen oxides by ammonia, which is an important environmental issue. Nevertheless, the structure of the most active Fe species in the low temperature NH3-SCR region, which are considered as isolated Fe, is still not fully clear. The most important limitation is the formation of oligomeric species, which are inactive at low temperature NH3-SCR, making bulky spectroscopic studies such as X-ray absorption spectroscopy challenging.Herein,a novel synthesis method for an SCR catalyst is disclosed which results in the fabrication of Fe/ZSM-5 catalyst with almost exclusively isolated Fe species. This approach allows to get more insight into the structure and role of Fe isolated species using in-situ X-ray absorption spectroscopy. The obtained results point to the existence of distorted square-planar Fe2+ species under reducing atmosphere, which is in good agreement with XANES simulations. At lower temperatures Fe species are partially moving out of square-planar to distorted square pyramidal geometry, which is caused by adsorption of one of the reactants. Such findings allow to improve the knowledge of structure-activity relationships and rational development and the application of Fe zeolites in NOx abatement.