| Popis: |
Catalysts containing ca.2% (w/w) of ruthenium were prepared by using [Ru(NH 3 ) 6 ]Cl 3 as a precursor compound and HY, NaY and KY zeolites as supports. Ru/KY catalyst modified by Na 2 S via impregnation was also investigated. Prior to the catalytic tests, the catalysts were sulphided with a H 2 -H 2 S mixture. The hydrodesulphurization (HDS) of thiophene at atmospheric pressure, the conversion of biphenyl, the hydrogenation (HN) of pyridine and the hydrodenitrogenation (HDN) of piperidine under medium-high pressure were carried out under dynamic conditions. The fast deactivation and, thus, the low activity of Ru/HY and Ru/NaY catalysts in the HDS of thiophene are attributed to coke formation on the Bronsted acid sites of the support. The stability and the activity of the catalysts in this reaction can be improved by decreasing the strength of the Bronsted acid sites. In the conversion of biphenyl, the activity towards the formation of cracking products increases with the acidity of the supports. The activity of the catalysts in the HN of pyridine and in the HDN of piperidine is less affected by the acid strength of the support. Only a slight decrease on the activities is observed for the most acidic support. |
