Uptake precious metal

E. Gomez, The Nanoparticle Formation and uptake of Precious Metals by Living alfalfa Plants. Master Thesis, the University of Texas at El Paso, Chemistry Department, El Paso, TX, 2002, p. 81. 

Precious metal catalysts have shown to be effective for the desulfurization of the steri-cally hindered compounds. One example is given with a commercial catalyst using both, palladium and platinum [23]. The high activity of these metals towards hydrogenation would result in aromatic saturation reactions, and consequently an increase in operating costs (not only for the catalyst cost but also for the increase in hydrogen uptake). 

Figure 1 shows the TPR profiles of the catalyst as received and after laboratory aging at 1173, 1273 and 1373 K. The main features correspond to those observed on model catalysts [10]. In the fi-esh state, there is a weU-resolved peak at 570 K, ascribable to the reduction of the oxidized precious metals and the ceria surface. After aging, the curve becomes flattened with much lower Hz uptakes. When the aging temperature is increased firom 1173 to 1373 K, the intensity of the first peak is reduced to nearly zero, whilst two other curve inflexions or small peaks become more distinct at around 800 and 970-1000 K. 

Data for sulfur uptake and HDS activity of precious metals promoted... 

---