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Challenging Thermodynamics: Hydrogenation of Benzene to 1,3‐Cyclohexadiene by Ru@Pt Nanoparticles
Author(s) -
Weilhard Andreas,
Abarca Gabriel,
Viscardi Janine,
Prechtl Martin H. G.,
Scholten Jackson D.,
Bernardi Fabiano,
Baptista Daniel L.,
Dupont Jairton
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201601196
Subject(s) - catalysis , benzene , bimetallic strip , ionic liquid , chemistry , hexafluorophosphate , selectivity , cyclohexene , ruthenium , inorganic chemistry , nanoparticle , organic chemistry , materials science , nanotechnology
Since the earliest reports on catalytic benzene hydrogenation, 1,3‐cyclohexadiene and cyclohexene have been proposed as key intermediates. However, the former has never been obtained with remarkable selectivity. Herein, we report the first partial hydrogenation of benzene towards 1,3‐cyclohexadiene under mild conditions in a catalytic biphasic system consisting of Ru@Pt nanoparticles (NPs) in ionic liquid (IL). The tandem reduction of [Ru(COD)(2‐methylallyl) 2 ] (COD=1,5‐cyclooctadiene) followed by decomposition of [Pt 2 (dba) 3 ] (dba=dibenzylideneacetone) in 1‐ n ‐butyl‐3‐methylimidazolium hexafluorophosphate (BMI ⋅ PF 6 ) IL under hydrogen affords core–shell Ru@Pt NPs of 2.9±0.2 nm. The hydrogenation of benzene (60 °C, 6 bar of H 2 ) dissolved in n ‐heptane by these bimetallic NPs in BMI ⋅ PF 6 affords 1,3‐cyclohexadiene with an unprecedented 21 % selectivity at 5 % benzene conversion. Conversely, almost no 1,3‐cyclohexadiene was observed when using monometallic Pt 0 or Ru 0 NPs under the same reaction conditions and benzene conversions. This study reveals that the selectivity is related to synergetic effects of the bimetallic composition of the catalyst material as well as to the performance under biphasic reaction conditions. It is proposed that colloidal metal catalysts in ILs and under multiphase conditions (“dynamic asymmetric mixtures”) can operate far from the thermodynamic equilibrium akin to chemically active membranes.