B. Trathnigg, W. Hreczuch, J. Szymanowski, C. Rappel, R. Hödl
May 1, 2013
Oxyethylation of dodecanoic acid was performed in the presence of a conventional alkaline catalyst, a homogeneous alkaline earth metal catalyst and a heterogeneous rare earth metal catalyst, respectively. As the result, three series of products were obtained in a range of average polyaddition degrees from N = 3 up to N = 9. The content of the obtained products was determined analytically by different chromatographic 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 catalysts significantly influenced the obtained homologue distributions and the content of di-esters and polyethylene glycols as byproducts. Much more selective ethoxylation is observed in the presence of the multivalent metal catalysts. As the result, the equivalent product series exhibit significant differences of physicochemical properties and surface activity. The new capabilities in analytical determination of the complex mixture of ethoxylated acids and the detected substantial differences in their chemical content can give a new input for more detailed investigation of these products.