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<p>Phenolic oligomers, abundant by-products from phenol and methanol alkylation and lignin valorization processes, contain resistant interunit C–C bonds that hinder their further utilization. Herein, we report a green and efficient catalytic system for the C–C bond cleavage of phenolic dimers over tartaric acid-modified HY zeolite, enabling the upcycling of phenolic wastes into valuable phenolic monomers. Moderate tartaric acid treatment (0.1&#xa0;M) effectively removes both extra-framework and a portion of the framework aluminum species, generating secondary mesopores and exposing more accessible Brønsted acid sites on the external surface and within mesopores. Among the catalysts tested, 0.1 TA-HY exhibits the best performance, increasing the phenolic dimer conversion from 52.6% with unmodified HY to 61% and significantly enhancing the yield of monomeric phenols at 330&#xa0;°C for 2&#xa0;h. Under the optimal conditions of 7&#xa0;g phenolic dimer mixture, 0.49&#xa0;g catalyst, 14&#xa0;mL methanol, 330&#xa0;°C, and 2&#xa0;h, the conversion of phenolic dimers and the yield of monocyclic phenols reached maximum values of 75.1% and 65.3%, respectively. Comprehensive characterization (XRD, <sup>27</sup>Al MAS NMR, N₂ adsorption, Py-IR, DTBP-IR, and TG/DTG) confirms that mild acid modification optimizes both pore structure and acidity while maintaining the integrity of the FAU framework. Spearman correlation analysis (r = 0.8) indicates that the number of accessible external and mesoporous Brønsted acid sites is strongly correlated with catalytic activity for C–C bond cleavage. Mechanistic investigations suggest that the reaction proceeds via proton-assisted pathways on Brønsted acid sites, with methanol acting synergistically through its hydrogen-donating and solvent roles to enhance substrate activation and stabilize intermediates. This work provides a sustainable approach to converting phenolic residues into high-value monomers through zeolite acidity regulation and mild organic acid modification.</p> Graphical Abstract

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Tartaric Acid Modified HY Zeolite for Efficient C–C Bond Cleavage of Phenolic Dimers

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Wanchun Li,
  • Xin Wang,
  • Ziying Ju,
  • Kexin Xiao,
  • Xuan Meng,
  • Li Shi,
  • Naiwang Liu

摘要

Phenolic oligomers, abundant by-products from phenol and methanol alkylation and lignin valorization processes, contain resistant interunit C–C bonds that hinder their further utilization. Herein, we report a green and efficient catalytic system for the C–C bond cleavage of phenolic dimers over tartaric acid-modified HY zeolite, enabling the upcycling of phenolic wastes into valuable phenolic monomers. Moderate tartaric acid treatment (0.1 M) effectively removes both extra-framework and a portion of the framework aluminum species, generating secondary mesopores and exposing more accessible Brønsted acid sites on the external surface and within mesopores. Among the catalysts tested, 0.1 TA-HY exhibits the best performance, increasing the phenolic dimer conversion from 52.6% with unmodified HY to 61% and significantly enhancing the yield of monomeric phenols at 330 °C for 2 h. Under the optimal conditions of 7 g phenolic dimer mixture, 0.49 g catalyst, 14 mL methanol, 330 °C, and 2 h, the conversion of phenolic dimers and the yield of monocyclic phenols reached maximum values of 75.1% and 65.3%, respectively. Comprehensive characterization (XRD, 27Al MAS NMR, N₂ adsorption, Py-IR, DTBP-IR, and TG/DTG) confirms that mild acid modification optimizes both pore structure and acidity while maintaining the integrity of the FAU framework. Spearman correlation analysis (r = 0.8) indicates that the number of accessible external and mesoporous Brønsted acid sites is strongly correlated with catalytic activity for C–C bond cleavage. Mechanistic investigations suggest that the reaction proceeds via proton-assisted pathways on Brønsted acid sites, with methanol acting synergistically through its hydrogen-donating and solvent roles to enhance substrate activation and stabilize intermediates. This work provides a sustainable approach to converting phenolic residues into high-value monomers through zeolite acidity regulation and mild organic acid modification.

Graphical Abstract