Investigation Of Adsorption And Catalytic
INVESTIGATION OF ADSORPTION AND CATALYTIC
PROPERTIES OF Cu/ZSM-5 AND Cu/ERIONITE ZEOLITE SYSTEMS
L.P. Oleksenko1, V.K. Yatsimirsky1, I.V. Kuzmich1,
G.M. Telbiz2, A.V. Shvetz2
1Kiev Shevchenko National University, Kiev, Ukraine
2Institute of Physical Chemistry, Ukrainian National Academy of Science,
Nauky avenue 31, 03028 Kiev, Ukraine
Synthetic zeolites are important class of solid materials which are used extensively as catalysts and adsorbents in a variety of chemical reactions and separation processes. The specific properties of zeolites ZSM-5 and erionite give possibility to modify the zeolite matrix by different metals for using them as effective catalysts.
The zeolite systems Cu/ZSM-5 and Cu/erionite were obtained by ion-exchanging from [Cu(NH3)4]Cl2 and Cu(CH3COO)2 solutions. The initial Cu-containing zeolite catalysts and systems after their preliminary treatment in hydrogen flow were investigated in catalytic reaction of CO oxidation.
It was established that the increasing of catalytic activity for initial Cu/ZSM-5 and Cu/erionite systems take place with simultaneously decreasing of the band absorption intensity of N-H bond oscillation of complex cations in IR-spectrum of these zeolite systems. This dependence is explained by decreasing of number of ligands in coordination sphere of metal.
The catalytic activity of Cu/ZSM-5 and Cu/erionite in the reaction of carbon monoxide oxidation by molecular oxygen were compared. It was determined by ESR-method that the difference in catalytic properties of copper/zeolite systems is connected with the peculiarities of copper ions state in them. According to ESR spectrum, copper ions form clusters in the channels of Cu/ZSM-5 matrix. Isolated copper ions existed in the case of Cu/erionite.
IR-spectroscopy of adsorbed CO was used for obtaining the knowledge about the electronic state and dispersion of the supported metals in the ion-exchanged zeolites. Carbon monoxide adsorption demonstrates multiple binding states, providing information about the oxidation and coordination state of the charge-balancing cations as well as on their surface concentration.
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