Enhanced Sulfur Tolerance of Bimetallic PtPd/Al 2 O 3 Catalysts for Hydrogenation of Tetralin by Addition of Fluorine
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Enhanced Sulfur Tolerance of Bimetallic PtPd/Al2O3 Catalysts for Hydrogenation of Tetralin by Addition of Fluorine Siriporn Jongpatiwut Æ Nitchanun Rattanapuchapong Æ Thirasak Rirksomboon Æ Somchai Osuwan Æ Daniel E. Resasco
Received: 30 October 2007 / Accepted: 15 December 2007 / Published online: 23 January 2008 Ó Springer Science+Business Media, LLC 2008
Abstract A series of mono- and bi-metallic Pt-Pd/Al2O3 samples with and without F were studied as aromatic hydrogenation catalysts. The effects of changing the order of impregnation of the Pt precursor and F as well as varying the calcination temperature (300–500 °C) were investigated. Temperature programmed reduction (TPR) results demonstrate the presence of a higher fraction of dispersed metal precursor species left on the surface from the impregnation (PtOxCly ) on the Pt/Al2O3 sample calcined at high temperature. The impregnation of F before the Pt precursor significantly decreases the interaction between the metal and the support. However, this decrease is not observed when F is impregnated after the metal precursor. For the bimetallic Pt-Pd catalysts, the sample prepared adding F before the metal show a higher degree of Pt-Pd interaction than either the parent Pt-Pd/Al2O3 catalyst or the one prepared with F added later. TPD of ammonia result show the increase in strong acid sites when F is present. Activity tests for tetralin hydrogenation in the presence of 350 ppm dibenzothiophene indicate a better sulfur tolerance for all F-promoted catalysts, especially Pt-Pd. Keywords Hydrogenation Tetralin Pt Pd F TPR Hydrogen chemisorption XPS TPD of NH3
S. Jongpatiwut (&) N. Rattanapuchapong T. Rirksomboon S. Osuwan The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand e-mail: [email protected] D. E. Resasco School of Chemical, Biological, and Materials Science, The University of Oklahoma, Norman, OK 73019, USA
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1 Introduction There have been many attempts to upgrade different diesel fractions such as LCO by hydrogenation of polyaromatics. Catalysts that are typically used in industry for this upgrading are sulfided CoMo and NiMo catalysts, which have high sulfur tolerance and relatively low cost. However, these catalysts are not very active so high temperatures are required for the process. Thermodynamically, higher temperatures result in lower equilibrium conversions, so higher pressures are needed. During the last decade, studies have focused on noble metal catalysts which exhibit high activity at milder conditions [1–14]; however, the weakness of these catalysts is their sensitivity to the sulfur compounds present in the feed. In most studies, platinum-based catalysts have been employed with a second metal as a promoter (e.g., Pd, Ge, Cu, Ru) over different supports (e.g., alumina, silica-alumina, zeolite). The purpose of most of these studies has been to understand the deactivation by sulfur and improve the catalytic performance in the presence of sulfur. Many reports [6–9, 11–13] have demonstrate
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