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Application of the beta PdH Decomposition for Characterization of Supported Palladium Catalysts

Bonarowska M., Karpiński Z.

Polish Journal of Chemistry

2008

Vol. 82, nr 10

1973-1979

Temperature-programmed (palladium) hydride decomposition (TPHD) appeared to be a convenient method for characterization of supported palladium catalysts. Both the amount of hydrogen released from the catalyst and the temperature of hydride decomposition are sensitive diagnostic parameters to wards determining the mean size and, especially, the size distribution of palladium particles. On the other hand, carbiding of Pd/SiO2 catalysts hinders in corporation of hydrogen into Pd bulk. The rate of temperature increase during the temperature-programmed hydride decomposition experiments seems to be an important factor. Application of too steep temperature ramps (e.g. 20°C/min) leads to the results which are less in formative than the results obtained for lower ramps because the TPHD components characteristic for hydride decompositions from differently sized Pd crystal lites merge into a single feature.

Hydrodechlorination of 1,2-Dichloroethane over Differently Reduced Pd/SiO2 Catalysts

Śrębowata A., Juszczyk W., Karpiński Z.

Polish Journal of Chemistry

2003

Vol. 77 / nr 12

1841-1848

Samples of 5 wt.% Pd/SiO2 catalyst reduced at moderate (400 graduateC) and high temperature (600 graduate C) were investigated in the reaction of 1,2-dichloroethane hydrodechlorination (HDC). The highly reduced catalyst exhibited a higher selectivity towards ethylene, approaching 70% at 300 graduate C, whereas the catalyst reduced at 400 graduateC gave mainly ethane (SC2H6 ~90% at 300 graduate C). Reduction of Pd/SiO2 at 600 graduate C leads to the formation of palladium silicide. In consequence, incorporation of Si in Pd surface lowers the hydrogenating strength of palladium, contributing to a higher ethylene selectivity. Such a behaviour resembles an analogous situation with Pd modified by Ag. It was shown that the catalysts deactivated rapidly at temperatures between 200 and 300 graduate C. After reaction, much larger amounts of carbon were found in the sample reduced at 400 graduate C. X-ray diffraction studies showed that a considerable part of this carbon was located in the bulk of palladium phase, i.e. forming a PdCx solution.