III International Conference

PP-II-94In the case of investigated Ag-containing zeolite catalysts formed in temperature interval20 – 700 °C the considerable difference in the sample activities, which depended on carriernature, occurred for the most active (Ag-NaX) and for the least active (Ag-NaM) systems in COoxidation ΔT 100 amounted to 79 °С in I cycle and 99 °С in II catalysis cycle. Ag-NaX revealed thehighest activity among the investigated Ag-containing catalysts (T foming = 20 – 700 °C). Thereason of activity difference for Ag-zeolite catalysts may be caused by the difference indistribution of active centers and their quantity in catalyst surface layer. According to TPR-H 2data the degree of interaction of active phase with the surface of investigated zeolites was various– the maximum temperatures of hydrogen absorption for less active catalysts Ag-NaZSM-5 (37)and Ag-NaM amounted T max = 255 – 265 °C; for more active samples Ag-Na,K-ERI andAg-NaZSM-5 (69) the value of T max equaled to 175 – 180 °C. Different influence of reactionenvironment on activity of catalysts Ag-carrier was noted – in the case of more active samplesAg-NaX and Ag-NaA the subsequent increasing of activity (ΔT 100 = 23 – 25 °C) was observed inII catalysis cycle.The investigation of activity of 1 – 10mas.% Ag-NaX systems formed in air intemperature interval T form. = 20 – 350 °C depending on silver content showed that the sample3% Ag-NaX had the highest activity. The catalyst with low content of active component3% Ag-NaX (T form. = 20 – 350 °C) had activity comparable with the activity of10% Ag-NaZSM-5 (37) (T form. = 20 – 700 °C). It was established that for 10% Ag-NaXcatalyst pretreatment at T form. = 20 – 700 °C was more favorable in comparison withT form. = 20 – 350 °C.The investigation of Ag-Co-NaX catalysts (T form. = 20 – 350 °C) in CO oxidation showedthat the introducing of cobalt as additional active component resulted in more high activity ofAg-Co-containing catalysts in comparison of 10%Ag-NaX. It was established that influenceof character of pretreatment (oxidative or reductive) on activity of Ag-Co-NaX systems wasdefined by the ratio of active component (Ag/Co) in catalyst.References1. J.Jansson // J. Catalysis 194 (2000) 55–60.2. X.Tang, B.Zhang, Y.Li, Y.Xu, Q.Xin // Appl. Catalysis A: General 288 (2005) 116–125.3. H.Hayashibara, S. Nishiyama, S. Tsuruya and M. Masai //J. Catalysis 153 (1995)254-264.334