Patent Watch

October 26, 2009

Oxidize benzene cleanly to phenol. A coproduct-free route to phenol has been an important goal of industry for many years. The current industrial process for making phenol is based on oxidizing cumene to cumene hydroperoxide followed by acid-catalyzed rearrangement to give 1 equiv of phenol and 1 equiv of acetone. On a weight basis, for every 10 t of phenol produced, 6 t of acetone is also produced. “Two-for-one” processes like this one are economical only if the demands for both products grow at the same rate. The fear is that phenol demand is growing faster than acetone demand and that there will be an oversupply of acetone that causes its price to fall. Falling acetone prices hurt the production economics of phenol because byproduct credit for acetone is taken.

Inventors D. Arunabha, S. Sakthivel, and S. J. Kumar found that vanadium-based catalysts can effectively hydroxylate benzene to phenol by using H₂O₂ as the oxidant. For example, 70 mmol of H₂O₂ is added to a flask containing ~0.05 mmol of vanadyl pyrophosphate [(VO)₂P₂O₇], 20 mL of MeCN, and 40 mmol of benzene. The contents are stirred at 60 °C for 1.5 h, at which point another 70 mmol of H₂O₂ is added and the mixture agitated for another 7 h. Benzene conversion is 53% and selectivity to phenol is 100%. Other experiments demonstrate the recyclability of the catalyst. Reused catalyst maintains phenol selectivity at 100% but benzene conversion drops to ~43%. (Council of Scientific and Industrial Research [New Delhi, India]. US Patent 7,586,014, Sept. 8, 2009; Jeffrey S. Plotkin)

View patent information from CAS.

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