Catalytic bleach processes

(T. Topalovic, V.A. Nierstrasz and M.M.C.G. Warmoeskerken)

The goal of this project is to focus on the potentials of different innovative oxidative catalysts, redox-mediator systems and enzymes for the industrial bleaching of cotton fabrics. Environmentally friendly processes on the basis of oxidative catalysts can accomplish low temperatures (e.g. 40°C) and short residence time and therefore result in a dramatic decrease in energy consumption with significant reduction of chemicals and water compared to the conventional process. Our primary aim within this project is to delineate mechanisms, and in particular the factors governing reactivity and catalysis. For that the project extends the investigation by examining the reaction mechanisms of the catalytic hydrogen peroxide oxidation of cotton pigments and model compounds in a homogeneous model system. Model compounds, mostly polyphenolic compounds, should be well characterised and chosen in the way to adopt the structural motifs of pigments giving the colour to the cotton fibre. Using advanced analytical techniques this approach allows us to study reaction kinetics and analyse the nature of active bleaching species, reaction intermediates and products. Like this, by excluding transport phenomena and with the assumption that the mechanism of oxidation of pigments that are present in cotton fibre is similar to that in a homogeneous system, it is possible to provide direct information about kinetics and reaction mechanisms at molecular level and a comparison of structure-reactivity towards catalytic oxidation relationships of a series of polyphenolic substrates.