Commercial hopcalite calcined at different temperatures and hopcalite modified with noble metals (Pt, Pd, and Au) were studied in oxidation of thiophene. Surface and bulk properties of catalysts were studied using temperature-programmed reduction (TPRH2), X-ray diffraction method (XRD) and thermal analysis (TG-DTA-MS). It was shown that calcined samples displayed higher activity in comparison with commercial untreated hopcalite; however, a lower temperature of calcination was favourable. High temperature of thermal treatment induced an increase in the crystallinity and a decrease in the surface area of the samples, and, as a consequence, the loss of catalysts activity. Moreover, marked improvement in the catalytic performance of platinum and palladium modified catalysts in relation to base hopcalite was observed. The obtained results indicate that the higher activity of samples containing Pt and Pd was accompanied by better reducibility of the catalysts.

In this paper the comparison of activity of hopcalite (Mn-Cu mixed oxides) modified with noble metals (Pd, Pt and Au) calcined at 300, 400 and 500°C in oxidation of thiophene was presented. Hopcalite modified with Pd demonstrated the highest activity among the studied samples, thus the results of a more detailed study of the most promising palladium catalyst were also shown. Surface and bulk properties of catalyst were studied with BET, XRD, TPR H2 and TG-DTA-MS. The redox properties and distribution of active components on the catalyst surface seem to be important factors influencing the modified hopcalite performance in the oxidation reactions. It was found that irreversible changes occurred during thermal treatment in the Pd-modified hopcalite structure, however they have no marked influence on activity of modified catalysts.