THE INVESTIGATION OF REDOX PROPERTIES OF PALLADIUM-ZEOLITE CATALYSTS

Palladium catalysts based on A, X, Y, chabazite, erionite, mordenite, TsVM, and TsVK zeolites are studied by the methods of temperature-prog rammed reduction and hydrogen desorption. Palladium is shown to be loc ated in zeolite pores in all catalysts except Pd/mordenite for which 2 4 % of the palladium is located on the external surface of the zeolite . The dispersity of the palladium on the zeolites is determined by the amount of H-2 evolved in the decomposition of the beta-phase of PdH a nd by the value of the O/Pd ratio obtained by palladium oxidation in t he 100 to 500 degrees C temperature range. According to the O/Pd ratio , the catalysts are divided into two groups: samples based on X, Y, ch abazite, erionite, and mordenite (O/Pd = 0.4 to 0.7), and catalysts co ntaining A, TsVM, and TsVK zeolites (O/Pd = 0.2 to 0.3). The catalysts of the first group are weakly active in the oxidative acetoxylation o f propylene, while all of the catalysts of the second group except Pd/ NaA are very active. The conclusion is drawn that the oxidation of pal ladium is not the limiting stage in the oxidative acetoxylation of pro pylene.