Adsorption And Catalytic Properties
ADSORPTION AND CATALYTIC PROPERTIES
OF Co/ZSM-5 ZEOLITES
L. P. Oleksenko, V. K. Yatsimirsky, L. V. Lutsenko
Kiev Shevchenko National University, Kiev, Ukraine
The investigation of adsorption and catalytic properties of the metalcontaining zeolite systems is actual for the studying of peculiarities of metal-carrier interaction in zeolite systems. The Co/ZSM-5 zeolites using ion exchange method have been obtained and their structural, acidic and catalytic properties in the CO oxidation have been investigated in our work.
The Co-containing zeolites with different metal contents were obtained from Co(NO3)2 and [Co(NH3)6]Cl3 solutions. The Co/ZSM-5 zeolites were used in initial state - directly after cation exchange and in the partly reduction state -after treatment in hydrogen flow at 300-5000C.
The catalytic activity of Co-zeolites was studied in CO oxidation using reaction gas mixture with oxygen excess. It was shown that catalysts after reduction treatment in hydrogen flow have more higher catalytic activity, than initial Co-containing zeolites as for Co3+/ as for Co2+/ZSM-5. The zeolites Co2+-Co3+/ZSM-5 with cobalt ions in different valent state after reduction treatment have higher activity as compared with zeolites contained only Co3+ ions. It may be connected with precence of diffe rent coordination states (oktahedral and tetrahedral) of Co ions in zeolite.
The investigation of acidic properties of Co/ZSM-5 zeolites were carried out by TPD method. Before measurements the Co- zeolites were heated to 5500C for removing of water molecules and adsorbed gases. Two types of adsorbed ammonia molecules which correspond to strong and weak acidic centres in Co-zeolites were fixed in TPD spectra at 100-380 and 400-7000C, correspondingly. The introduction of metal cations into the zeolites and their reduction in hydrogen flow causes to acidity decreasing. The c orrelation of catalytic activity and acidic properties was found. When acidity of zeolites was decreased the catalytic activity in CO oxidation was increased.
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