Inhibition Effect of Phosphorus Poisoning on the Dynamics and Redox of Cu Active Sites in a Cu-SSZ-13 NH₃-SCR Catalyst for NO_x Reduction

Abstract

Phosphorus (P) stemming from biodiesel and/or lubricant oil additives is unavoidable in real diesel exhausts and deactivates gradually the Cu-SSZ-13 zeolite catalyst for ammonia-assisted selective catalytic NO x reduction (NH3-SCR). Here, the deactivation mechanism of Cu-SSZ-13 by P-poisoning was investigated by ex situ examination of the structural changes and by in situ probing the dynamics and redox of Cu active sites via a combination of impedance spectroscopy, diffuse reflection infrared Fourier transform spectroscopy, and ultraviolet–visible spectroscopy. We unveiled that strong interactions between Cu and P led to not only a loss of Cu active sites for catalytic turnovers but also a restricted dynamic motion of Cu species during low-temperature NH3-SCR catalysis. Furthermore, the CuII ↔ CuI redox cycling of Cu sites, especially the CuI → CuII reoxidation half-cycle, was significantly inhibited, which can be attributed to the restricted Cu motion by P-poisoning disabling the formation of key dimeric Cu intermediates. As a result, the NH3-SCR activity at low temperatures (200 °C and below) decreased slightly for the mildly poisoned Cu-SSZ-13 and considerably for the severely poisoned Cu-SSZ-13.

Unravelling Phosphorus-Induced Deactivation of Pd-SSZ-13 for Passive NOx Adsorption and CO Oxidation

“…Taken together, our detailed ex situ physicochemical characterization and in situ spectroscopic interrogation unraveled the P-indued transformation of cationic Pd sites in Pd-SSZ-13 zeolites. The deteriorated performance in passive NO x adsorption and CO oxidation confirms a poisoning effect of P on Pd-SSZ-13, resembling that observed in Cu-SSZ-13 SCR catalysts in several previous studies. ,,, These findings may provide new considerations for the design of P-resistant Pd-zeolites for simultaneous abatement of NO x and CO at low temperatures.…”

“…The deteriorated performance in passive NO x adsorption and CO oxidation confirms a poisoning effect of P on Pd-SSZ-13, resembling that observed in Cu-SSZ-13 SCR catalysts in several previous studies. 16,18,33,48 These findings may provide new considerations for the design of Presistant Pd-zeolites for simultaneous abatement of NO x and CO at low temperatures.…”

“…The severe poisoning of [Pd­(OH)] + @8MR by P was also validated by the drastically weakened vibrational band at 3667 cm –1 for OH groups in IE-P (see the spectra in Figure S13 and related discussions in the Supporting Information). , …”

“…The severe poisoning of [Pd(OH)] + @8MR by P was also validated by the drastically weakened vibrational band at 3667 cm −1 for OH groups in IE-P (see the spectra in Figure S13 and related discussions in the Supporting Information). 47,48 We further performed in situ CO-DRIFTS, which is widely applied to identify supported metal active sites in different forms (e.g., single-atom, cluster, nanoparticle), 6,9,30,49 to verify the observations by in situ NO-and NH 3 -DRIFTS, and the collected spectra are displayed in Figure 6, as well as Figure S14 in the Supporting Information. Multiple characteristic bands appeared in the spectra of fresh Pd-SSZ-13 sample (IEfresh) upon exposure to CO at 25 °C and built up in intensity with increasing exposure time.…”

Review of the application of Cu-containing SSZ-13 in NH3-SCR-DeNOx and NH3-SCO

“…Several researchers suggest that phosphorus tends to poison ZCuOH more easily than Z 2 Cu. 96,155 To regenerate the P-poisoned Cu-SSZ-13 catalysts, phosphorous species in the catalysts should be removed. As an example of that approach, Chen et al 71 successfully applied the combination of washing with hot water (90 °C) and hydrothermal treatment (800 °C for 12 h) to recover the activity of the phosphorous-poisoned Cu-SSZ-13.…”