Preconversion catalytic deoxygenation of phenolic functional groups. Quarterly technical progress report, October 1--December 31, 1995

Recent research in the author`s laboratory has established the viability of the catalytic deoxygenation of phenols by Co monoxide. The deoxygenation of phenols is a problem of both fundamental and practical importance. The deoxygenation of phenols to arenes is a conceptually simple, yet a very difficult chemical transformation to achieve. The phenolic C-O bond energy of 103 kcal/mol is as strong as a benzene C-H bond and over 10 kcal/mol stronger than the C-O bonds of methanol or ethanol. Catalytic hydrodeoxygenation (HDO) of phenols over sulfided Mo/{gamma}-Al{sub 2}O{sub 3}, Ni-Mo/{gamma}-Al{sub 2}O{sub 3}, Co-Mo/{gamma}-Al{sub 2}O{sub 3} or other supported metal oxide catalysts can be achieved, at exceedingly high hydrogen pressures and temperature. Arene ring hydrogenation generally competes effectively with hydrodeoxygenation, and was found to occur an order of magnitude faster than HDO. As a consequence, most of the hydrogen is consumed in hydrogenation of the aromatic rings. HDO catalysts are easily poisoned. The inefficiency of catalysts for phenol deoxygenation in the presence of hydrogen can be attributed to the absence of a low energy mechanistic pathway for the hydrogenolysis of the strong phenol C-O bond. The authors are currently studying new transition metal catalysts for the efficient and selective deoxygenation of phenols using the Co/Co{sub 2} couple to remove phenolic oxygen atoms. The paper describes recent results on the mechanism of Co insertion into metal-oxygen bonds of phenoxides