Reactivity characteristics of Pt-encapsulated zeolite catalysts for hydrogenation and hydrodesulfurization

Noble metal catalysts are commonly used in hydrogenation processes. They are more effective than base metal catalysts such as Mo, Ni, or Co catalysts. However, noble metal catalysts are generally used in environments with sulfur concentrations below 10 ppm since they are susceptible to sulfur poisoning. This paper presents a noble metal catalyst specially prepared by using a Pt-encapsulated zeolite material. A set of pilot plant tests were conducted with naphthalene as a model hydrogenation compound and dibenzothiophene as a model sulfur compound. Based on catalyst evaluation with the noble metal catalyst and a base catalyst using novel 2-dimensional GC × GC analysis, it was observed that the Pt-encapsulated noble metal catalyst behaved differently from what is normally expected. When exposed to a high sulfur concentration of ∼600 ppm, the Pt-encapsulated catalyst gave almost the same naphthalene conversion as the Mo-Ni catalyst at 360 °C. Furthermore, both the Pt and Mo-Ni catalysts yielded a primary hydrogenation product tetralin instead of the secondary hydrogenation product decalin. The Pt-encapsulated catalyst also showed selectivity toward the direct desulfurization pathway instead of the hydrogenation–desulfurization pathway that is expected for desulfurization with noble metal catalysts.

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► The Pt-encapsulated catalyst behaved differently from what is normally expected.
► The Pt-encapsulated catalyst gave similar naphthalene conversion as the Mo-Ni catalyst.
► Both the Pt and Mo-Ni catalysts yielded tetralin instead of decalin.
► The Pt catalyst favors direct desulfurization pathway instead of hydrogenation pathway.