One-pot synthesis of cyclohexylphenol via isopropyl alcohol-assisted phenol conversion using the tandem system RANEY® Nickel plus hierarchical Beta zeolite

Cyclohexylphenols are valuable intermediate chemicals applied in the manufacture of dyes, resins, and pharmaceutical drugs. However, they are synthesized using raw chemicals derived from fossil fuels rather than sustainable sources (e.g., lignin-derived phenol). In this article, we report a one-pot synthesis of cyclohexylphenols via phenol-assisted conversion with isopropyl alcohol over the tandem catalytic system formed by RANEY (R) Nickel plus hierarchical Beta zeolite. Over this tandem catalytic system, cyclohexylphenols were synthesized with remarkable selectivity (similar to 70%) at high conversion rates (64%) after 1 h of reaction at 150 degrees C. In contrast, higher temperatures (175 degrees C) were required to obtain alkylphenols over the Al-SBA-15 catalyst, which is highly accessible thanks to its uniform mesoporous structure, albeit with weaker Lewis acid sites. Additionally, selectivity to cyclohexylphenols over Al-SBA-15 was far lower (19%) than over hierarchical Beta zeolite, and cresols were instead the most abundant alkylphenol (26%). Therefore, the combination of suitable accessibility and Bronsted acidity of hierarchical Beta with the hydrogenating ability of RANEY (R) Ni through catalytic hydrogen transfer from isopropyl alcohol drives the selectivity of this tandem system towards the production of cyclohexylphenols.

Automated summary

This article reports a one-pot synthesis of cyclohexylphenols using a tandem catalytic system formed by RANEY (R) Nickel and hierarchical Beta zeolite, with phenol-assisted conversion of isopropyl alcohol. The system exhibited remarkable selectivity for cyclohexylphenols at high conversion rates and lower temperatures compared to other catalysts.