Benzene selectivity in competitive arene hydrogenation: Effects of single-site catalyst···acidic oxide surface binding geometry
Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2–WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS >> AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3+/ZrS–, 83% > Cp*ZrMe2+/ZrS–, 80% > Cp*ZrBz2+/ZrS–, 67% > Cp*ZrPh2+/ZrS–, 57%. For Cp*ZrBz2+/ZrS–, which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2+/AlS– vs Cp*ZrMe2+/AlS–. Furthermore, the combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the “cationic” metalmore »
- Northwestern Univ., Evanston, IL (Unuted States). Dept. of Chemistry.
- UOP LLC, Des Plaines, IL (United States)
- Sapienza University of Rome (Italy). Dipartimento di Chimica.
- Argonne National Lab., Argonne, IL (United States). Chemical Sciences and Engineering Div.
- Iowa State Univ., Ames, IA (United States). Ames Lab.
- Publication Date:
- Report Number(s):
Journal ID: ISSN 0002-7863
- Grant/Contract Number:
- AC02-06CH11357; FG02-86ER13511; AC02-07CH11358
- Published Article
- Journal Name:
- Journal of the American Chemical Society
- Additional Journal Information:
- Journal Volume: 137; Journal Issue: 21; Journal ID: ISSN 0002-7863
- American Chemical Society (ACS)
- Research Org:
- Argonne National Lab. (ANL), Argonne, IL (United States); Ames Lab., Ames, IA (United States)
- Sponsoring Org:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Country of Publication:
- United States
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
- OSTI Identifier:
- Alternate Identifier(s):
- OSTI ID: 1214127; OSTI ID: 1234445