Composition of Ethoxylated Dodecanoic Acid Obtained with Three Different Catalysts as Determined by Means of Liquid Exclusion Adsorption Chromatography (LEAC)

摘要

Comparative ethoxylation of dodecanoic acid was performed with a conventional alkaline catalyst, a homogeneous alkaline earth metal catalyst, and a heterogeneous rare earth metal catalyst, respectively. As a result, three series of products were obtained in a wide range of average polyaddition degrees from Nav. = 4 up to Nav. = 100. The content of the obtained products was determined analytically by different chromato-graphic techniques: size exclusion chromatography (SEC) with dual detection, gradient liquid adsorption chromatography (LAC) with evaporative light-scattering detection (ELSD), and liquid exclusion adsorption chromatography (LEAC), a new technique, which allows quantitatively accurate determination of the oligomer distribution of ethoxylates. It was found that the applied catalyst significantly influenced the obtained homolog distributions and the content of di-esters and polyethylene glycols as by-products. More selective ethoxylation is observed in the presence of the multiva-lent metal catalysts. As a result, the equivalent product series exhibit significant differences in physicochemical properties and surface activity. The new capabilities in analytical deter-mination of the complex mixture of ethoxylated acids and the detected substantial differences in their chemical content can provide new input for more detailed investigation of these products.