The Oxyiodination of Aromatic Compounds over Zeolite KX: The Case of Naphthalene

Aromatic compounds, iodine, and oxygen react in the vapor phase over basic faujasite zeolites at 225-350°C to produce iodoaromatic compounds and water. When the aromatic compound is naphthalene and the reaction is conducted in the region of 250°C over KX zeolite, a shape-selective catalytic oxyiodination occurs, resulting in predominant iodination at the 2-position of naphthalene. Typical product mixtures contain approximately 10% 1-iodonaphthalene, 65% 2-iodonaphthalene, 19% 2,6-diiodonaphthalene, 5% other diiodonaphthalene isomers, and 1% mixed triiodonaphthalene isomers at approximately 20% naphthalene conversion and 80-99% iodine conversion. Excessive conversion and excessive residence time reduce the selectivity to kinetic product, 2,6-diiodonaphthalene, but do not alter the selectivity for iodination in the 2-position. Selectivity for iodination in the 2-position is decreased by substituting sodium for potassium in the zeolite, by altering the faujasite zeolite Si/Al ratio significantly above or below 1.25, and by increasing the amount of iodine in the reactant feed.