Study On Sulfer Tolerant Of Hydrogenation Ctalysts Basing Pt/NaA Zeolite

The metal-supported material is a kind of important hydrogenation catalyst. It has widely used in the fuel oil hydrofining, modification. Especially the noble metal-supported catalyst has high hydrogenation activity of aromatic saturation and it is important to process high aromatic content of fuel oil. But this kind of catalyst is very sensitive for sulfer and is easy to be poisoning deactivation. The sulfur tolerant noble metal catalyst applied in hydrogenation reaction is prepared in the experiment. This paper study the different calcium ion exchange degree of Pt/Na(Ca)A zeolite, the different mixture ratio of Pt/NaA-Pt/CaA catalyst, Pt/NaA-HY catalyst, Pt/NaA-HZSM-5catalyst, Pt/NaA-Al2O3catalyst, Pt/NaA-SiO2catalyst. The hydrogen spillover ability and acid of hydrogen spillover receptors are investigated through H2-TPD and NH3-TPD. The sulfur tolerant ability is showed by benzene hydrogenation reaction. The results are given in following.(1) The typical characteristic peaks of Pt/NaA zeolite are completely consistent with that of NaA zeolite, so the NaA zeolite encapsulated Pt have been synthetized successfully. And the crystallization degree of the Pt/NaA zeolite is higher, the hydrogen spillover ability is stronger, thus improving crystallization degree of the Pt/NaA zeolite is the primary task.(2) we adopt two methods in order to make the Pt/NaA zeolite have catalytic activity. one is to expand zeolite aperture to adsorb benzene molecules. After the Calcium ion exchange the crystal structure of Pt-supported LTA zeolite does not change. With the increase of calcium ion exchange degree, the H2desorption curve of Pt/Na(Ca)A zeolite gradually shift in the direction of high temperature. with the increase of exchange degree, reaction conversion rate of Pt/Na(Ca)A zeolite also increases, and conversion rate will no longer increases to a certain extent. with the increase of the content of Pt/NaA, the hydrogenation activity of Pt/NaA-Pt/CaA catalyst will decrease gradually. Different exchange degree of Pt/Na(Ca)A zeolites do not have catalytic activity after poisoning processing. When Pt/NaA-Pt/CaA catalyst poisoning processing catalyst still have a little catalytic activity, but this part of experiment need further proof.(3) The introduction of hydrogen spillover receptors is also to adsorb benzene molecules. With the increase of HY zeolite mixture ratio, the H2desorption curve of Pt/NaA-HY raise and gradually shift in the direction of high temperature. however, as the mix proportion continue to increase, the H2desorption curve gradually reduced. So the appropriate increasing proportion of the HY zeolite will be conducive to hydrogen spillover ability. And with the increase of HY zeolite mixture ratio, the hydrogenation activity has been increased. As the increase of silica alumina ratio of HY, HZSM-5zeolite, the hydrogenation activity and hydrogen spillover ability of catalysts do not change, and catalysts will no conversion rate to a certain extent.(4) After the overall catalyst poisoned the hydrogen spillover ability of Pt/NaA-HY catalyst will decrease and the hydrogenation activity will also decrease. So Pt/NaA-HY catalyst is not resistant to sulfur poisoning. However, after Pt/NaA is treated the hydrogen spillover ability of Pt/NaA-HY catalyst is hardly change and the hydrogenation activity is also change slightly, therefore the Pt/NaA zeolite has a certain resistance to sulfur poisoning. after HY is treated the hydrogen spillover ability of Pt/NaA-HY catalyst descend and the hydrogenation activity is none. So HY zeolite is poisoned and can not serve as a suitable hydrogen spillover receptor. Acid content of HY zeolite is not change after it is treated, so poisoning treatment does not affect its acid content.When HZSM-5and Al2O3serve as hydrogen spillover receptors the regularity of hydrogen spillover and hydrogenation reaction are the same with HY. So HY, HZSM-5and Al2O3can not serve as suitable hydrogen spillover receptors, after the amorphous SiO2is treated the hydrogen spillover ability of Pt/NaA-SiO2catalyst is hardly change, but the catalyst is no hydrogenation activity, it cannot be used as hydrogen spillover receptor.Finally, it is also mentioned that when the hydrogen spillover receptor is treated the catalyst will have no hydrogenation activity. it may be associated with the redox reaction of surface.