High Carbon Ash from Stoker Fired Boiler of a Thermal Power Station as Support in the Reduction of Ketones: A Novel Application

Abstract

Reduction of a few substituted cyclohexanones adsorbed on size classified high carbon ash fractions from a stoker fired boiler of a thermal power station using NaBH₄ as the reducing agent with ethanol as the medium resulted in the formation of two epimeric alcohols. However, trans-4-t-butyl and trans-4-methylcyclohexanols are exclusively formed when the corresponding ketones adsorbed on one particular size classified ash fraction are reduced with NaBH₄. In all other cases, a fairly high degree of stereoselectivity has been obtained. It has been observed that low carbon ash does not activate the ketones towards similar stereoselectivity, clearly establishing that the high carbon ash has a definite role to play. The stereochemical outcome of the reductions has been rationalized on the basis of a probable transition state involving Lewis/Br⊘nsted acid sites present in the ash. Mesopores and macropores present in the ash are most likely to act as pockets for adsorption of ketones. Product analysis has been carried out using ¹HNMR and ¹³CNMR.

Keywords:

• high carbon ash
• macropores
• mesopores
• reduction
• stereoselectivity

Notes

^aResults reported are averages of at least three experiments. For 4-t-butylcyclohexanone and 4-methyl cyclohexanone, wherever 100% stabler alcohol was formed, at least five experiments were carried out to check the reliability of the results obtained.

^bValues in parentheses are those reported for the reduction of the same ketones using NaBH₄ under homogeneous conditions of reactions. Source: Nasipuri et al. (1982).