Influence of Na, P and (Na + P) poisoning on a model copper-ferrierite NH3-SCR catalyst

Abstract

To highlight the deactivation mechanisms encountered by minerals impurities from biodiesel, the effects caused by Na, P or (Na+P) additions were studied over a model Cu-FER catalyst. Na, P or (Na+P) were added by wet-impregnation in water in a wide concentration range up to 2 wt-%. The catalytic behaviors were evaluated by NH3/NO oxidation and standard/fast NH3-SCR reactions. In addition, a combination of several characterization techniques (ICP-AES, N2 adsorption/desorption, XRD, NH3-TPD, NO adsorption monitored by FTIR and H2-TPR) was applied to provide useful information regarding the deactivation mechanism caused by the minerals addition. Sodium and phosphorus interacted differently with the Cu-FER catalyst. Na addition induced a loss of Brønsted acid sites and a back-exchange of Cu 2+ with Na + , with formation of external CuO species, thus favoring the oxidation of NO and NH3. After phosphorus addition, the exchanged Cu 2+ species remained moderately affected, but direct interactions with copper were evidenced which were primarily responsible for catalyst deactivation toward the oxidation reactions. After equimolar addition of phosphorus and sodium, both Na and P effects were observed. For the NH3-SCR process, the ammonia adsorption ability, which depends on both acidity and copper units, appeared the main key parameter driving the catalytic activity at low temperature (T ≤ 250 °C). Phosphorus appeared to be the major responsible for catalyst deactivation after (Na+P) co-poisoning.

Efficient Strategy to Regenerate Phosphorus-Poisoned Cu-SSZ-13 Catalysts for the NH3-SCR of NOx: The Deactivation and Promotion Mechanism of Phosphorus

“…All of the catalysts show adsorption bands at 1916, 1908, and 1891 cm −1 , which can be attributed to NO adsorbed on Cu 2+ sites. 23,25,48,61 The amount of Cu 2+ ions follows the order Cu-F > Cu-0.3P-R3 > Cu-0.3P-R2 > Cu-0.3P-R1 > Cu-0.3P, which is consistent with the EPR result. This illustrates that the NO adsorption ability of Cu-SSZ-13 is reduced after phosphorus impregnation and then recovered by washing with hot water.…”

“…Recently, a growing number of studies have focused on the deactivation mechanism of Cu-zeolite catalysts by phosphorus poisoning. ,,− Regrettably, to the best of our knowledge, there is no report on the regeneration of phosphorus-poisoned SCR catalysts in the open literature. If phosphorus-poisoned catalysts can be regenerated, the service life of Cu-SSZ-13 catalysts can be greatly improved.…”

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

“…Depending on the reaction conditions, Pd in zeolites could interconvert between highly dispersed and aggregated states, , which can be distinguished by in situ DRIFTS using different molecular probes (e.g., NO, CO, NH 3 , etc.). Here, we first used NO as a probe molecule, which could form stable nitrosyl adducts upon interaction with metal ions, to interrogate the state of Pd sites in SSZ-13 before and after P-poisoning. , Figure a presents the DRIFT spectra in the range of 1800–2000 cm –1 for the Pd-SSZ-13 catalysts during NO adsorption at 100 °C. An intense band at 1865 cm –1 and a feeble shoulder at 1811 (1817) cm –1 were observed, and it can be attributed to nitrosyl complexes adhering on two types of cationic Pd sites, i.e., Pd 2+ in 6MR and [Pd­(OH)] + in 8MR (denoted as [Pd­(OH)] + @8MR), respectively. ,,,,, After P-poisoning, band intensities related to NO species at [Pd­(OH)] + @8MR decreased dramatically, while the IR band for NO at isolated Pd 2+ was preserved without a significant change in intensity.…”

Mechanochemical Synthesis of Highly Porous CeMnOx Catalyst for the Removal of NOx

“…Nitrogen oxides (NO and NO 2 ), released from stationary and mobile source exhaust, have generated a series of serious environmental issues, such as photochemical smog, acid rain, greenhouse effects, and ozone depletion. − Selective catalytic reduction with NH 3 (NH 3 -SCR) is currently regarded to be one of the most effective strategies to reduce NO x emissions. , Meanwhile, V 2 O 5 –MoO 3 (WO 3 )/TiO 2 has been the extensively employed and currently commercial NH 3 -SCR catalyst. , However, several disadvantages are still present in this system, which considerably limit its further utilization in practical applications, for instance, the toxicity of vanadium species, the high operation temperature, the low specific surface area of TiO 2 , and so forth. − Furthermore, the temperature of emitted NO x from stationary coal-fired plants and boilers is generally lower than 250 °C, yet the V 2 O 5 –WO 3 (MoO 3 )/TiO 2 catalyst is not effective for the abatement of exhaust smoke NO x at the so-low temperature region. Therefore, it is necessary and imperative to develop environmentally friendly NH 3 -SCR catalysts with excellent low-temperature activity for the conversion of NO x .…”