Production of carboxylic acids by controlling the active form of iridium catalyst in response to infrared absorption spectra

摘要

The present invention relates to an improved process for the preparation of carboxylic acids, specifically by the reaction of ethylenically unsaturated compounds with carbon monoxide and water, in the presence of catalyst compositions essentially comprising iridium compounds and complexes, together with an iodide promoter, the improvement being the provision of at least 50 percent by weight of the iridium in the reaction solution in a highly catalytically active form as a species having infrared absorption bands at 2098 cm.sup.-.sup.1 (vs), 2155 cm.sup.-.sup.1 (w), 2180 cm.sup.-.sup.1 (vw, br) . By monitoring the infrared absorption spectra of reacting solutions and following the magnitude of the 2098 cm.sup.-.sup.1 band the operating conditions are adjusted so that this band is present in 50 percent or more concentration relative to the infrared absorption spectral bands of the other iridium species in solution. Through this monitoring and control process significantly increased reactor productivity to carboxylic acids is achieved.