Improvement of Furan Yield in Oxidation of Crotonaldehyde by Modifying 12-Molybdophosphoric Acid Catalysts

Abstract 12-Molybdophosphoric acid effective for oxidation of crotonaldehyde to furan was modified in two ways; by adding various cations and by replacing Mo with V or W. Among cations caesium was proved to be most effective in improving the furan yield, by decreasing reactivity of product furan relative to crotonaldehyde, thus minimizing the secondary oxidation of furan to maleic anhydride. The highest efficiency of caesium is associated with its high basicity, while the active catalyst species responsible for the furan formation is acidic in nature. The replacement of Mo by V or W gave rise to decreased activity, in contrast to other oxidations on the same catalyst. The unique character of crotonaldehyde oxidation is discussed.