Clean synthesis of acetaldehyde oxime through ammoximation on titanosilicate catalysts

Abstract

Acetaldehyde oxime has been synthesized though the liquid-phase ammoximation of acetaldehyde with ammonia and hydrogen peroxide over various titanosilicate catalysts. Titanium mordenite (Ti-MOR), prepared from highly dealuminated mordenite and TiCl4 vapor by a secondary synthesis method, was superior to TS-1 and Ti-MWW catalysts both in aldehyde conversion and in oxime selectivity. The reaction parameters were investigated systematically in a batch-type reactor for Ti-MOR, such as solvent effect, temperature, time, catalyst loading, amounts of ammonia and hydrogen peroxide relative to aldehyde as well as addition methods of the reactants. Under optimized conditions, Ti-MOR was capable of showing an aldehyde conversion of 99% and an oxime selectivity of 97%. In comparison with TS-1 and Ti-MWW, the advantage of Ti-MOR in acetaldehyde ammoximation was mainly attributed to its lower ability for oxidation to convert the aldehyde to acetic acid. There was almost no effect resulting from the addition mode of the reactants; Ti-MOR with its special characteristics was unique in catalytic behavior and easy handling. An overview of the reaction routes involved in acetaldehyde ammoximation has been provided.