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, 8 (12), 11184-11190

Selective Production of Biobased Phenol From Lignocellulose-Derived Alkylmethoxyphenols


Selective Production of Biobased Phenol From Lignocellulose-Derived Alkylmethoxyphenols

Xiaoming Huang et al. ACS Catal.


Lignocellulosic biomass is the only renewable source of carbon for the chemical industry. Alkylmethoxyphenols can be obtained in good yield from woody biomass by reductive fractionation, but these compounds are of limited value for large-scale applications. We present a method to convert lignocellulose-derived alkylmethoxyphenols to phenol that can be easily integrated in the petrochemical industry. The underlying chemistry combines demethoxylation catalyzed by a titania-supported gold nanoparticle catalyst and transalkylation of alkyl groups to a low-value benzene-rich stream promoted by HZSM-5 zeolite. In this way, phenol can be obtained in good yield, and benzene can be upgraded to more valuable propylbenzene, cumene, and toluene. We demonstrate that intimate contact between the two catalyst functions is crucial to transferring the methyl groups from the methoxy functionality to benzene instead of phenol. In a mixed-bed configuration, we achieved a yield of 60% phenol and 15% cresol from 4-propylguaiacol in a continuous one-step reaction at 350 °C at a weight hourly space velocity of ∼40 h-1.

Conflict of interest statement

The authors declare no competing financial interest.


Scheme 1
Scheme 1. Pathways for the Production of Phenol from Lignin Fraction of Lignocellulosic Biomass
The black arrows indicate the main focus of the present study, the green arrows known technologies outside the scope of the present study.
Figure 1
Figure 1
Product distribution of (a) 4-propylphenol- and (b) benzene-derived products of the transalkylation of 4-propylphenol with benzene over different zeolites (conditions: 400 mg 4-propylphenol, 4 mL benzene, 40 mg catalyst, 350 °C, 2 h, the zeolite Si/Al ratio given in brackets, the selectivity and yield of alkylbenzenes are based on the 4-propylphenol feedstock).
Figure 2
Figure 2
One-step process for demethoxylation and dealkylation over (a–d) stacked-bed and (e,f) mixed-bed Au/TiO2 and HZSM-5 (Si/Al = 15) catalysts in benzene using a fixed-bed down-flow reactor (conditions: 5 mol % 4-propylguaiacol in benzene, 350 °C, 100 bar, gas flow rate 30 N mL/min H2, weight hourly space velocity (WHSV): (a) 48 h–1, (b and e) 40 h–1, (c and f) 30 h–1, and (d) 20 h–1.
Scheme 2
Scheme 2. Conversion of (a) Guaiacol, (b) Catechol, and (c) Phenol over the Au/TiO2 and HZSM-5 Catalysts in Benzene Solvent Using a Batch Reactor (Conditions: 10 mmol Feedstock, 100 mg HZSM-5 or 50 mg Au/TiO2, 30 mL Benzene, 350 °C, 50 bar H2)
Scheme 3
Scheme 3. Proposed Reaction Network of the One-Step Process for Demethoxylation and Dealkylation over (a) Stacked-Bed and (b) Mixed-Bed of Au/TiO2 and HZSM-5 Catalysts in Benzene Using a Fixed-Bed Reactor (Conditions: 5 mol % 4-Propylguaiacol in Benzene, 350 °C, 100 bar, Gas Flow Rate 30 mL/min H2, WHSV 30 h–1)

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