Abstract: The present work studies a possibility to regulate the size and structure of magnetic associates of copper ions by varying the OH/Cu2+ ratio in a wide range (from 0 to 30) during the hydrolytic polycondensation of copper chloride in the zeolite pores. The redox properties and reactivity in N2O decomposition and NO-SCR by propane of the Cu-modified ZSM-5 catalysts prepared by the hydrolytic polycondensation are examined and compared with the properties of copper-substituted ZSM-5 zeolites having a close copper content (1wt.%) and produced by the ion exchange with water-ammonia solutions of copper chloride at OH/Cu equal to 6-30. The origin of active copper species, which are formed during hydrolytic polycondensation under variation of ОН/Cu and at subsequent thermal treatment, has been studied by ESR and UV-Vis DR spectroscopy. It was shown that an increase in ОН/Cu from 1-3 to 6-30 leads to the orbital ordering of Cu2+ ions in the weak associates, which shows up as a change of the symmetric signal (g0 = 2.18) from disordered polynuclear copper hydroxocomplexes to the rhombic signals (gz1 = 2.18, gy1 = 2.08, gx1 = 2.03 and gz2 = 2.24, gy2 = 2.08, gx2 = 2.03) corresponding to the ordered polynuclear complexes of copper ammoniate. The 1%Cu(30)ZSM-5-HPC sample prepared at OH/Cu = 30 has a higher amount of isolated tetraammine-copper complex and a lower number of weak associates of Cu2+ ions among samples of this series. Thermal treatment of 1%CuZSM-5-HPC leads to a gradual removal of ammonia from the copper environment. Hence, these samples calcined at 500oC comprise the isolated Cu2+ ions surrounded by the oxygen-containing ligands, similar to the samples prepared at OH/Cu equal to 0-3. The addition of ammonia solution to the copper-impregnated zeolite for hydrolytic polycondensation and variation of the ammonia to copper ratio (OH/Cu from 1 to 30) have a favorable impact on the Cu-ZSM-5 activity in N2O decomposition and NO-SCR by propane. In the low-temperature region, the ion-exchanged CuZSM-5 catalysts were more active in N2O decomposition, while at high temperatures the ex-polycondensation provided a high N2O conversion. It is suggested that the ordered associated Cu2+ ions of ex-polycondensation catalyst have higher activity and selectivity in both DeNOx processes as compared to the isolated copper ions.

Cite: Yashnik S.A. , Salnikov A.V. , Vasenin N.T. , Anufrienko V.F. , Ismagilov Z.R.
Regulation of the Copper-OIxide Cluster Structure and DeNOx Activity of Cu-ZSM-5 Catalysts by Variation of OH/Cu2+
Catalysis Today. 2012. V.197. N1. P.214-227. DOI: 10.1016/j.cattod.2012.08.033 WOS Scopus РИНЦ ANCAN OpenAlex

Dates:

Submitted:	Apr 29, 2012
Accepted:	Aug 26, 2012
Published online:	Oct 9, 2012
Published print:	Dec 1, 2012

Identifiers:

Web of science:	WOS:000310598600024
Scopus:	2-s2.0-84868345746
Elibrary:	24936041
Chemical Abstracts:	2012:1487652
Chemical Abstracts (print):	157:742477
OpenAlex:	W1984341319

Citing:

DB	Citing
Web of science	42
Scopus	48
Elibrary	49
OpenAlex	42

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