ИСТИНА

In this work 2 wt.% of Pd was supported by wet impregnation on two types of alumina (E, produced by Engelhard, and C, produced by calcination of boemite at 600°C), both pristine and modified with 20 wt.% of Н8[Si(W2O7)6]×6Н2О (HPS), and tested in multi-phase HDC [1] of 1,3,5-trichlorobenzene. Using IR DO spectroscopy after CO adsorption, it was found that relatively large Pd0 particles are the major form of palladium in nonmodified catalysts. In modified catalysts the fraction of Pd0 is much lower, and single Pd+ and Pd2+ions are also found. The features of Lewis Catalyst TOF, h-1 t50, min Pd/Al2O3 (Е) 11 180 Pd/Al2O3 (C) 30 250 Pd/ГПС-Al2O3 (Е) 18.2 62 Pd/ГПС-Al2O3 (C) 34.6 105 acidity of the catalysts surface and the presence of HPS and/or the products of its thermal decomposition define the possibility of TCB adsorption and activation not only on Pd, but also on a support. Then adsorbed moieties can be reduced with hydrogen spilling over the surface from Pd and W centers. Also the new types of active centers can be formed on the border between Pd and HPS particles. All listed phenomena provide an improvement of catalysts activity (Table 1, t50 is time of 50% TCB conversion) and stability in aggressive reaction medium after modification of a support with HPS. The catalysts on Al2O3 (Е) have better performance due to the feature of structure, as it was found by TEM and XRD.