Alkylation of phenol with tert-butyl alcohol over dealuminated HMCM-68 zeolites

• Dealuminated HMCM-68 zeolites were prepared by steaming or acid leaching.
• Their catalytic properties were studied using the alkylation of phenol with TBA.
• HMCM-68 modified by citric acid for 8 h (CAZ8) showed the best catalytic activity.
• CAZ8 had improved adsorption polarity and enlarged pore volume.
• Both of the improved structural and acidic properties played important roles.

A series of dealuminated HMCM-68 zeolites were prepared by treatment with steaming or hydrochloric/citric acid leaching. Their catalytic properties were studied using the alkylation of phenol with tert-butyl alcohol as a test reaction. The HMCM-68 zeolite modified by citric acid for 8 h (CAZ8) showed the best catalytic performance due to its improved structural and acidic properties, confirmed by methods of XRD, ICP-AES, SEM, N2-adsorption, 27Al MAS NMR and NH3-TPD. Furthermore, it is proposed that citric acid treatment is the most suitable method for dealumination of HMCM-68 zeolite in the alkylation of phenol, which results in the zeolites having improved adsorption polarity, as well as enlarged surface area and pore volume for the desired transformation. The factors affecting the reaction over CAZ8 have also been extensively investigated.

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