DescriptionHighly anionic cellulose was selectively prepared at room or higher temperature by using ClO2 activated TEMPO as the catalyst and NaOCl as the oxidant at pH 8. TEMPO radical or its derivative was spontaneously converted to oxoammonium cation by ClO2 in a closed vessel before the catalytic oxidation (Scheme 1). The pretreatment initiated the catalytic cycle immediately after mixing the chemicals. The oxoammonium cation oxidized C6 alcohols of cellulose to carboxylates via an aldehyde intermediate. HOCl repeatedly reoxidized the formed hydroxyl amine to the oxoammonium cation. Conversion of the residual aldehydes to carboxylates by HClO2 stabilized the oxidized pulp which was then fibrillated mechanically to nanofibrillar cellulose (NFC). The optimized oxidation level for preparation of NFC was 0.8 mmol COOH / g pulp. The main advantage of the novel oxidation route over the traditional TEMPO/NaBr/NaOCl oxidation, which is widely reported in literature, is the exclusion of bromide that is difficult to remove from NFC. Furthermore, ClO2 is a widely used chemical at pulp mills, which are convenient sites for NFC production if bleached pulps are used as the raw material.
|Period||10 Oct 2012 → 12 Oct 2012|
|Event title||International Cellulose Conference|
|Location||Sapporo, JapanShow on map|