Toluene oxidn. over Pb/Li/MgO is investigated in a tubular fixed bed reactor at low conversions. A periodic process alternating toluene oxidn. in absence of oxygen in the feed and regeneration of the catalyst by oxygen presents important changes in product distribution in comparison with steady-state oxidn. Periodic conditions increase the selectivity in favor of the coupling reaction which leads to 1,2-diphenylethane and avoid formation of oxygenated products. [on SciFinder (R)]