Acylation of aromatic compounds such as veratrole (1,2-dimethoxybenzene), anisole, isobutyl benzene, and 2-methoxynaphthalene with acetic anhydride (Ac2O) has been investigated over different solid acid catalysts such as MWW, BEA, FAU, MOR, and MFI. MWW catalysts have been characterized by X-ray diffraction, N2 adsorption-desorption isotherm, and HR-FESEM characterization techniques. The reaction is studied in the temperature range 313-353 K under N2 atmosphere. Among the catalysts tested, MWW was found to be more active than other zeolites. This is mainly due to its three dimensional porous structure with excellent textural characteristics. The effect of veratrole/Ac2O molar ratio, catalyst concentration, and reaction temperature has been optimized to get higher conversion of Ac2O. Under the optimized reaction conditions, MWW gave the Ac2O conversion of 64.3% with a selectivity to acetoveratrone (3',4'-dimethoxyacetophenone) (100%). It was also found that the structural features and acidity play an important role in the conversion and product distribution in the acylation of different aromatic substrates like anisole, isobutyl benzene, and 2-methoxy naphthalene. MWW catalyst has been reused in few cycles after regeneration by washing with ethyl acetate followed by calcination at 500 °C for 4 h without loss in its activity. The reaction kinetics of the catalyst was also studied and the results are discussed in detail.
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Acknowledgments This work was financially supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) under the Strategic Program for Building an Asian Science and Technology Community Scheme and World Premier International Research Center (WPI) Initiative on Materials Nanoarchitectonics, MEXT, Japan.