Abstract
Platinum’s (Pt) poisoning effect on Cu-SSZ-13 and its regeneration were investigated. The Pt enhanced the parallel reactions, such as NH3 oxidation and NO oxidation reactions, which decreased the deNOx activities. In the temperature range below 330 °C, the deactivation of Cu-SSZ-13 by Pt poisoning was primarily caused by the overconsumption of NH3, due to the enhanced NH3-selective oxidation reaction, while the formation of NOx in NH3 oxidation and NO oxidation into NO2 further aggravated the degradation when the temperature was above 460 °C. The non-selective NH3 oxidation and non-selective NOx catalytic reduction reactions resulted in increased N2O formation over Pt-doped samples. The transformation of Pt0 into PtOx after hydrothermal aging recovered the deNOx activities of the Pt-poisoned samples.
Highlights
Cu-exchanged SSZ-13 has recently been commercialized as a catalyst for the selective catalytic reduction of NOx with a NH3 (NH3-SCR) section in a diesel engine exhaust aftertreatment system [1]
Specific to the sulfur poisoning, the deactivation caused by SO2 poisoning is mostly reversible, as NH4HSO4 and CuHSO4 intermediates formed on Cu-SSZ-13 can be decomposed after thermal treatment at high temperatures [8]
The Cu-SSZ-13 presented above 75% NOx conversion at 150–550 ◦C, and the N2O concentration was below 20 ppm, indicating that the NO and NH3 were primarily converted via the standard NH3-SCR reaction (R.1) pathway over Cu-SSZ-13
Summary
Cu-exchanged SSZ-13 has recently been commercialized as a catalyst for the selective catalytic reduction of NOx with a NH3 (NH3-SCR) section in a diesel engine exhaust aftertreatment system [1]. The deactivation of Cu-SSZ-13 is typically attributed to the destruction and transformation of cupric sites from SCR-active to -inactive forms, which is irreversible [5,9]. In addition to the poisoning effect of the destruction and transformation of isolated Cu2+ ions into inactive forms [6,10,11,12], the additional chemical contaminants may act as active sites that catalyze side reactions in the NH3-SCR reaction system. Lezcano-Gonzalez et al [6] investigated the effect of series pollutants (Pt, Zn, Ca and P) on Cu/SSZ-13 catalysts during the NH3-SCR process, and Pt poisoning The effect of hydrothermal treatment on the recovery of a Pt-contaminated sample was analyzed
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