Mesoporous Al-MCM-41 (Si/Al = 55 and 104) and Al,Zn-MCM-41 (Si/(Al + Zn) = 102) were synthesized by the surfactant-templated route. The catalytic activity was evaluated in the vapour phase reaction of m-cresol with ethyl acetate in the temperature range 200-400 °C. The identified products were 4,7-dimethylcoumarin (4,7-DMC), 2-acetyl-5-methylphenol (2A-5MP), 3-methylphenyl acetate (3-MPA), 2-ethyl-5-methylphenol (2E-5MP) and 4-ethyl-3-methylphenol (4E-3MP). Reaction parameters such as temperature, feed ratio and WHSV were optimised to obtain high 4,7-DMC selectivity at maximum conversion of m-cresol. The time-on-stream study revealed slow deactivation of the catalyst under optimum conditions. Though alkylation of m-cresol was the reaction, acylation dominated over alkylation, suggesting that ethyl acetate is also an active acylating agent for m-cresol. Ring acylation followed by esterification, and subsequent intramolecular condensation observed in this study, suggest an interesting novel one-pot route for the synthesis of coumarin derivatives in the vapour phase.
Bibliographical noteFunding Information:
The authors are grateful to the Department of Science and Technology (DST), New Delhi, India, for the financial support for carrying out this research work. The authors acknowledge deeply the financial support for creation of instrumental facilities in the Department of Chemistry under DST-FIST program and University Grants Commission (UGC) under special assistance DRS. One of the authors, K. Shanmugapriya, is thankful to CSIR for the award of SRF fellowship.
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- Ethyl acetate