Continuous liquid phase acylation of toluene over HBEA zeolite: Solvent effects and origin of the deactivation

•Multiple perspectives analysis of deactivation of HBEA zeolite.•Moderate acetic acid increases the yield and selectivity of 4-methylacetophenone.•Prove that toluene acylation is primarily a Broensted acid catalyzed reaction.

The continuous liquid phase Friedel–Crafts acylation of toluene (T) by acetic anhydride (AA) over HBEA zeolite was carried out in a fixed bed reactor, with acetic acid (AC) as a solvent. 4-Methylacetophenone (4-MAP) was selectively formed in the initial reaction stage. However, a rapid catalyst deactivation occurred with a sharp decrease of the conversion of acetic anhydride, and this was mainly caused by 4-MAP and heavy compounds (‘coke’) existing in the zeolite pore, which poisoned the active sites of the catalyst. The use of excess toluene and moderate acetic acid enhanced catalyst activity and stability to some extent as it limited both the retention of 4-MAP and the formation of ‘coke’. Moreover, a considerable reduction of Broensted acid sites after deactivation revealed that the toluene acylation is primarily a Broensted acid catalyzed reaction.

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