High activity of mononuclear copper present in the framework of CuSiBEA zeolites in the selective catalytic reduction of NO with NH3

• Cu(II) was incorporated in zeolite framework by two-steps postsynthesis method.
• CuSiBEA zeolite catalysts were very active in SCR of NO with ammonia.
• N2 selectivity and NO conversion were depended on copper speciation and reaction temperature.
• Framework mononuclear Cu(II) were responsible for high activity and excellent N2 selectivity in NH3-SCR.

CuxSiBEA zeolites (with x = 1–7.5 Cu wt %) prepared by a two-step postsynthesis method which consists in the first step of dealumination of parent BEA zeolite to obtain aluminum-free SiBEA support and then in the second step, of contacting the obtained material with an aqueous solution of copper nitrate, were used in this work as catalysts of SCR of NO with ammonia. XRD, TPR and FTIR investigations showed that up to 2 wt % of Cu was successfully incorporated into zeolite beta structure as framework mononuclear Cu(II). The FTIR of pyridine sorption revealed that the incorporation of copper into zeolite framework led to the creation of new Lewis acidic sites which were responsible for high activity of CuxSiBEA zeolite catalysts in SCR of NO with ammonia. The catalytic activity of CuxSiBEA in SCR of NO with ammonia used as a reducing agent strongly depends on the nature and environmental of copper in BEA structure. The Cu1.0SiBEA catalyst with predominantly framework Cu(II) was the most active and selective among the tested samples in wide temperature range. In contrast, the application of CuxSiBEA zeolite catalysts with higher Cu content (>than 2 wt % of Cu) containing a mixture of framework and extra-framework Cu(II) resulted in low NO conversion in SCR at high temperature range, as well as, the high concentration of undesired N2O in outgas stream. It indicates that octahedral Cu(II) and/or copper oxides present in extra-framework position of SiBEA zeolite promote at high temperature ammonia oxidation.

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