Explorations into the Nature of Cu2+ Ions in SSZ-13 Zeolites for the Selective Catalytic Reduction of NOx with NH3

SiO2/Al2O3 Mole Ratio: 22
Na2O Weight %: 0.05
Surface Area, m2/g:530
Size:2-3um; 300-800nm

SSZ-13 is a high silica zeolite with the CHA topology. Materials with this topology are of industrial interest, as potential catalysts for application in the methanol to olefins (MTO) reaction.

Recently SSZ-13 has attracted attention as the catalyst for selective catalytic reduction (SCR) of NOx. Actually copper-loading SSZ-13 is industrially applied to the emission control of diesel engines.

SSZ-13 shows superior performance in NOx abatement,methanol to olefin (MTO) and adsorption and separation of gas.

SSZ-13 Zeolite Application

• 1) Methanol to Olefins (MTO)
• 2) Selective Catalytic Reduction of Nitrogen Oxides (SCR) for diesel engines
• 3) Gas adsorption separation of small organic molecules i.e., alkanes, olefins, CO2 etc.
• 4) Industrial waste gas treatment, VOC abatement and Air purification (removal of toxic molecules i.e., H2S, SO2, HCHO, NH3, CO etc.)
• 5) Hydrogen Storage

Explorations into the Nature of Cu2+ Ions in SSZ-13 Zeolites for the Selective Catalytic Reduction of NOx with NH3

Zeolites are porous silica frameworks with localized aluminum anionic sites throughout its crystalline framework. Loose cations (often H+ or metals) charge balance these anionic sites. Due to these unique properties, zeolites have been used in ion-exchange, gas separation, and catalysis technologies [1]. The SSZ-13 zeolite used in this work is used in the automotive industry for NOx pollution abatement and has promise in the petrochemical industry for hydrocarbon and oxygenate conversion to fuels and chemicals - particularly partial methane oxidation [2-4].

The overall goal of this work is to understand the active site requirements for and the mechanistic details of NH3-SCR by combining operando X-ray absorption spectroscopy (XAS) measurements with other in-situ and ex-situ characterization techniques and density functional theory (DFT) calculations. We elucidate the presence of two types of Cu2+ ions and molecular details on how Cu2+ ions undergo a reduction-oxidation catalytic cycle dependent on the spatial density of Cu2+ to reduce NOx [5-6]. These discoveries compel us to reconsider the turnover rate (catalytic reaction rate normalized per active site), which are traditionally used to characterize single-site heterogenous catalysts, independent of the spatial density of active sites. This study also opens avenues to better understand the nature of Cu2+ sites for various reactions, and to strategically synthesize Cu-zeolites tailored for a broad range of chemistries.

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