Citrate-mediated sol–gel synthesis of Al-substituted sulfated zirconia catalysts for α-pinene isomerization

Abdallah I.M. Rabee, Lee Durndell, Nasr Fouad, Lucia Frattini, Mark Isaacs, Adam Lee, Gamal A.H. Mekhemer, Vannia Cristina dos Santos, Karen Wilson, Mohamed I. Zaki

Research output: Contribution to journalArticle

Abstract

Solid acids are desirable heterogeneous catalysts for green chemistry, with zirconia and its sulfated analogues offering tunable Lewis/Brønsted character. A new route to sulfated ZrO2, and Al-substituted ZrO2 (SO4/AlxZrO2), via carbonization and calcination of metal citrate gels and their subsequent sulfation by (NH4)2SO4 is reported. Structural and acidic properties of these materials were characterized by XRD, Raman, XPS, TGA-MS, N2 porosimetry, and propylamine and pyridine titration. Parent and sulfated materials all adopted the tetragonal zirconia phase, with Al-substitution (evidenced by contraction of the zirconia lattice parameter) at between 0.38–3.50wt% increasing the surface area but decreasing acid strength, accompanied by an overall increase in total acid site loading and Lewis character. Low Al concentrations enhance α-pinene isomerization activity by up to 50% due to the increase acid site loading, however the Turnover Frequency (TOF) remained constant indicating a common active site. The TOF decreased for Al concentrations >3.5wt% due to a further fall in acid strength, manifest as higher selectivity to polycyclic versus monocyclic products.
Original languageEnglish
Pages (from-to)206-212
JournalMolecular Catalysis
Volume458
Issue numberPart B
Early online date11 Nov 2017
DOIs
Publication statusPublished - 1 Oct 2018

Bibliographical note

Funding: Alexander von Humboldt foundation (Bonn) , EPSRC (EP/K000616/2 and EP/G007594/4). Royal Society Industry Fellowship, government of Egypt.

Keywords

  • Citrate mediated sol-gel
  • Sulfated zirconia
  • Terpenes
  • α-pinene
  • Solid acidity

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    Citrate-mediated sol–gel synthesis of Al-substituted sulfated zirconia catalysts for α-pinene isomerization

    Rabee, A. I. M. (Creator), Durndell, L. (Creator), Fouad, N. (Creator), Frattini, L. (Creator), Isaacs, M. (Creator), Lee, A. (Creator), Mekhemer, G. A. H. (Creator), dos Santos, V. C. (Creator), Wilson, K. (Creator) & Zaki, M. I. (Creator), Aston Data Explorer, 11 Oct 2017

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    Cite this

    Rabee, A. I. M., Durndell, L., Fouad, N., Frattini, L., Isaacs, M., Lee, A., Mekhemer, G. A. H., dos Santos, V. C., Wilson, K., & Zaki, M. I. (2018). Citrate-mediated sol–gel synthesis of Al-substituted sulfated zirconia catalysts for α-pinene isomerization. Molecular Catalysis, 458(Part B), 206-212. https://doi.org/10.1016/j.mcat.2017.10.029