Flucidation of behavior of sulfur on alumina-supported platinum and palladium using a ~(35)S radioisotope tracer method

摘要

The growing knowledge about the aromatics contained in diesel fuels in respect to their adverse effects causing undesired emissions in exhaust gases and resultant health hazards has led to limitations on the use of these aromatics around the world. Under such circumstances, refiners are require to develop new catalysts capable of higher hydrogenation activity in order to meet the emission standards that have been made more and more stringent each year (1-3). Noble metal catalysts such as #gamma#-Al_2O_3-supported platinum and palladium catalysts are known to be highly active in the hydrogenation of aromatics (4-6). Recently, the behavior of noble metal catalysts in the HDS has been investigated using a ~(35)S radioisotope pulse tracer method (~(35)S RPTM Method), which has been recently developed by the authors (7-9). The hydrogenation activity of phenanthrene (PHE) over the monometallic and bimetallic catalysts. Pt/Al_2O_3, Pd/Al_2O_3, and Pt/Pd/Al_2O_3. was investigated in the presence of dibenzothiophene (DBT). Although the bimetallic catalyst (Pt-Pd/Al_2O_3) did not show some synergetic effects in HDS reaction, this catalyst showed better performance in the HYD reaction of PHE in the presence of 1 wt% DBT than the CoMo catalyst. It was also found that only a small amount of labile sulfur was accommodated on the test noble metal catalysts in both HDS reaction of DBT and HYD reaction of PHE (5). These findings suggest that the test noble metal catalysts differed from those conventional Mo- or W-based 3 hydrotreating catalysts. Moreover, it was found that both the amount of the sulfur (S_(TOTAL)) accommodated on the catalyst and the amount of the labile sulfur (S_0) participating in the reaction increased linearly with increase in active metal loading (6). At the same time, it was found that almost all labile sulfur on these catalysts was mobile in the HDS reaction although their amounts was much less those on the conventional Mo-or W-based catalysts.