Effects of a sodium carbonate (Na2CO3) additive on the conversion of phenethyl phenyl ether (PPE) in high-temperature water

• PPE is applied as the model compound of β-ether bond in lignin.
• The conversion of PPE under HTW was highly promoted with addition of Na2CO3.
• Phenol, styrene and ethylbenzene were mainly produced by hydrolysis of PPE.
• The formation of a Na+–PPE adducts accelerated the hydrolysis reaction.
• Na2CO3 accelerated the heterolytic β-ether bond cleavage and α-hydrogen abstraction.

The use of high-temperature water (including near/super-critical water) has been studied as a promising reaction method for the valorization of lignocellulose biomass (lignin). The dissociation of lignin usually begins with the cleavage of ether bonds which are the weakest chemical linkages in a lignin structure. Of the ether bonds, the most prevalent type is a β-ether bond; phenethyl phenyl ether (PPE) is regarded as a suitable model compound for studying the cleavage of this bond. This study investigates the conversion of PPE in high-temperature water, with sodium carbonate (Na2CO3) serving as an additive to promote ionic pathways. The addition of sodium carbonate greatly enhanced the conversion of PPE and produced phenol as the primary product. It was proposed that phenol was obtained through the dissociation of a Na+–PPE adduct, which progressed via heterolytic ether cleavage and α-hydrogen abstraction.

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