Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-6KINETICS OF STARCH OXIDATION USING HYDROGEN PEROXIDEAS AN ENVIRONMENTALLY FRIENDLY OXIDANT AND AN IRONCOMPLEX AS A CATALYSTP. Tolvanen a , P. Mäki-Arvela a , A.B. Sorokin b , T. Salmi a , D.Yu. Murzin aa Process Chemistry Centre, Åbo Akademi University, FI-20500 Turku/Åbo, Finland,b Institut de Recherches sur la Catalyse et l’Environnement de Lyon, UMR 5256, UniversitéLyon 1 - CNRS, 2 avenue A. Einstein, 69626 Villeurbanne Cedex, France1. IntroductionNative starch has been used for a long time in the preparation of different products(intermediates to paper industry), due to its large availability and low cost. Anenvironmentally friendly oxidizing agent, hydrogen peroxide, was used in starch oxidation inthis work to suppress the amount of by-products. Iron tetrasulfonatophthalocyanine complex(FePcS) was applied as a catalyst, since very low catalyst amounts of this catalyst are neededresulting in a pure oxidized starch, leading to the residual iron content lower compared to ironsalts. Typically, large amounts of products are needed for determination of the degree ofsubstitution [1] and thus oxidation kinetics has not been studied previously in detail using thiscatalyst. The aim of this work was to determine the kinetics of starch oxidation with hydrogenperoxide in the presence of FePcS catalyst.a) b)2. Experimental sectionStarch oxidation wasperformed in a semibatch glassreactor (V L =1000 ml).Typically 260 g starch and 140mg catalyst were used in theFig. 1. a) Reaction scheme for starch oxidation and b) catalystexperiments. pH was keptstructure [1].constant by continuouslyadding 2M NaOH The main parameters were pH and the hydrogen peroxide flow rate(between 11 and 22 ml/h). The reaction temperature was 55 °C and the experiments weretypically carried out for 7 hours. Carboxyl and carbonyl contents of the oxidized starch weredetermined by Smith procedures, according to which the sample is titrated with NaOH for thecarboxyl content and with HCl for the carbonyl content. Additionally, the carbonyl andcarboxyl contents were analyzed with HPLC by using an acidic hydrolysis method [2]. Theyield was determined by drying and weighing the product. The residual iron content wasdetermined by ICP. SEM pictures were obtained from the native and oxidized starch.3. Results and discussionKinetics of starch oxidation given as degree of substitution of carboxylic groups, is shownin Fig. 2. In the beginning of experiments, oxidation mainly occurred on the surface of the37