High Sulfur Resistance Research Articles

Selective Hydrogenation of Cyclopentadiene over Supported Metal Catalysts

The selective hydrogenation of cyclopentadiene to cyclopentene has been studied in the liquid phase using Pd and PdMe/Al2O3 bimetallic catalysts (Me = Mn, Ni, Co, W). The highest activity was obtained with PdCo and PdW/Al2O3. For these catalysts, no hydrogen or CO chemisorption was detected although Pd could be seen by XPS at 335·8 eV; it is considered that new species, more active for the selective hydrogenation of cyclopentadiene, appeared at the catalyst surface. The sulfur resistance towards thiophene has also been studied. It was observed that the highest sulfur resistance is coincident with the highest activity. XPS analysis shows that the poisoning species is thiophene adsorbed on the catalyst surface.

Aromatics reduction over supported platinum catalysts. 2. Improvement in sulfur resistance by addition of palladium to supported platinum catalysts

Supported Pt catalysts were modified by adding a second metal such as Co, Mo, Ni, Re, Ag, and Pd. The effects of a second metal on the sulfur resistance were first investigated by accelerated aging test reactions. The test reactions were hydrogenation of tetralin containing 1,000 ppm sulfur at 280 C, 380 psig, and H{sub 2}/oil (mol) = 2.7. The results indicated that Pd-Pt catalyst had the highest sulfur resistance. Aromatics reduction, hydrodesulfurization, and hydrodenitrogenation of straight run distillate diesel over supported Pt and Pd-Pt catalysts were further examined by long-term stability tests. The operation conditions of these tests are the same as those run in a commercial diesel hydrotreating process. The results again indicated that the Pd-Pt catalyst exhibited much better catalytic performance. These results, together with electronic properties of the metal clusters on the catalysts characterized by FFT-IR spectroscopy, provide a basis to speculate the role of Pd in enhancing sulfur resistance; the Pd-Pt bimetallic interactions decrease the electron density of Pt and thereby inhibit the adsorption of H{sub 2}S.