The effects of different activated carbon supports and support modifications on the properties of Pt/AC catalysts

Two commercial activated carbons were used as catalyst supports in Pt/AC catalysts. Activated carbons were used in their unoxidized form or after either liquid phase oxidation with HNO3 or gas phase oxidation with 5% O-2. All six activated carbons were characterized by nitrogen adsorption, TPD. and SEM. Selected samples were tested by XPS. The types and abundance of the oxygen bearing surface groups on each of the activated carbon supports were determined from the deconvolution of the TPD profiles of the activated carbons. An evaluation of the results obtained from TPD and XPS together indicates that both oxidation treatments led to a nearly homogeneous increase of oxygen bearing groups on the outer surface as well as interior surfaces. XPS analysis revealed that the HNO3 oxidized samples have the highest concentration of oxygen bearing groups on the outermost surface. Pt/AC catalysts (1 wt.%) were prepared on these supports. The catalysts were characterized by TPR, H-2 adsorption, SEM-EDS and tested in structure insensitive benzene hydrogenation as well. The results obtained indicate that the oxidation treatments affect drastically the properties of the activated carbons as well as the catalysts prepared on them. A comparison between benzene hydrogenation activities validates the dispersion values obtained from H-2 adsorption at room temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.