Ortho-selective vapour phase methylation of phenol over nanocrystalline ferrospinels of varying Zn2+/Mn2+ ionic composition
✍ Scribed by Vanga S Reddy; A Radhe Shyam; R Dwivedi; RK Gupta; VR Chumbale; R Prasad
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2004
- Tongue
- English
- Weight
- 169 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0268-2575
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✦ Synopsis
Abstract
Ortho‐selective vapour phase methylation of phenol with methanol has been carried out over Zn~(1−x)~Mn~x~Fe~2~O~4~ (x = 0, 0.25, 0.5, 0.75, 1.0) in the temperature range 423–698K in a fixed‐bed, down‐flow reactor. o‐Cresol and 2,6‐xylenol were found to be the major products. Reaction parameters were optimized over MnFe~2~O~4~ (MF). Maximum yields of 68.3% and 14% with selectivities of 81% and 17% were obtained for 2,6‐xylenol and o‐cresol respectively, giving a total selectivity of 98% over MnFe~2~O~4~ at 598K, methanol to phenol molar ratio 6, and 0.4 h^−1^ weight hour space velocity. It was found that the product selectivity is greatly influenced by the acido‐basic properties of the catalysts. o‐Cresol formation is favoured over catalysts with weak acid sites whereas formation of 2,6‐xylenol occurs in the presence of stronger acid sites. Catalyst characterization has been carried out by X‐ray diffraction, infrared spectroscopy and ammonia desorption methods. X‐ray diffractograms were used to determine the unit cell length and correlated with the acidity and catalytic activity of the spinel systems. IR absorption bands observed around 700 cm^−1^ and 500 cm^−1^ are respectively attributed to the tetrahedral and octahedral metal‐oxygen stretching mode of the spinel. Shifting of bands towards lower wave numbers is correlated with composition and acidity of the spinel systems. The results are discussed on the basis of the Zn^2+^ and Mn^2+^ composition and acidity of the spinel systems. Copyright © 2004 Society of Chemical Industry