(661e) Direct Conversion of Ethylene to Propylene through Simultaneous Ethylene Dimerization and Olefin Metathesis with 8%NiSO4/8%ReO4/?-Al2O3 Catalyst

Propylene is a major petrochemical building block used to generate a variety of important chemicals. Historically, propylene has been produced as a byproduct of steam cracking. With an increase in shale gas production, however, steam cracking processes are switching to lighter feedstocks that produce less propylene. Thus, there is a need for the development of “on-purpose” methods for producing propylene. The direct conversion of ethylene to propylene (ETP) through simultaneous ethylene dimerization and olefin metathesis is a promising method for propylene production that is currently in development. In ethylene dimerization, two ethylene molecules dimerize to form butene molecules and through olefin metathesis, ethylene and 2-butene form two propylene molecules. Many catalysts have been proposed for this reaction. One method for designing a catalyst for ETP is to combine elements of catalysts for ethylene dimerization and catalysts for olefin metathesis. Ethylene dimerization catalysts are typically Ni-based and olefin metathesis catalysts are typically Mo-, W-, or Re-based. In the present study, a supported NiSO₄/ReO₄/γ-Al₂O₃ catalyst was synthesized for the direct conversion of ethylene to propylene, in which NiSO₄ performs ethylene dimerization to butenes and ReO₄ performs olefin metathesis to propylene. The catalyst was extensively characterization at the molecular level with in situ IR spectroscopy, in situ UV-vis spectroscopy, C₂⁼-TPSR spectroscopy, and ammonia adsorption to probe the nature of the surface acid sites. Preliminary findings at 60℃ achieved an ethylene conversion of 63% and a selectivity towards propylene of 76%. The structure-activity relationships of this catalytic system will be discussed during the presentation.