One pot menthol synthesis via hydrogenations of citral and citronellal over montmorillonite-supported Pd/Ni-heteropoly acid bifunctional catalysts

Abdul Karim Shah*, Ghulamullah Maitlo, Ahmed Shah, Iftekhar Ahmed Channa, Ghulam Abbas Kandhro, Hubdar Ali Maitlo, Umair Hassan Bhatti, Ahmed Shah, Abdul Qayoom Memon, Abdul Sattar Jatoi, Yeung Ho Park

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Menthol synthesis is possible through citral and citronellal hydrogenations via following multistage chemical reactions such as hydrogenation and cyclization. This research mainly focuses on a design of selective, active and cost-effective metal-acid (bifunctional) catalysts for menthol production via citral and citronellal hydrogenations. More specifically, Pd and Ni metals were impregnated over acidic support (e.g., hetero-poly acid supported montmorillonite, HPA_MM). The prepared catalysts were characterized by BET, pyridine adsorption and amine titration methods. Some of the most important parameters such as metal type and loading; applied pressure and reaction time have been investigated throughout this work. The obtained results reveals that the 8 wt% Ni-HPA-MM catalyst (Cat-5) has produced 63% menthols (initial reaction rate 0.126 mmol/min) from citral hydrogenation (80 °C, 1.0 MPa) within 24 h. Similarly, during lower applied pressure (0.5 MPa), the production of menthol was significantly improved (approximately 98% of menthol, initial reaction rate ~ 0.138 mmol/min) with the application of 8 wt% Ni-HPA-MM catalyst (Cat-5) in citronellal hydrogenation. Higher menthol selectivity was achieved from both reactions (citral and citronellal hydrogenation) which might be due to the presence of strong Lewis and medium Brønsted acid sites.

Original languageEnglish (US)
Pages (from-to)917-934
Number of pages18
JournalReaction Kinetics, Mechanisms and Catalysis
Volume128
Issue number2
DOIs
StatePublished - Dec 1 2019

Bibliographical note

Publisher Copyright:
© 2019, Akadémiai Kiadó, Budapest, Hungary.

Keywords

  • Bifunctional catalysts
  • Citral
  • Citronellal
  • Isopulegol
  • Menthol

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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