4-Acetamido-TEMPO+ oxidizes primary alcohol groups rapidly to carboxylate groups. The target of this laboratory work is to show if dissolved cellulose (commercial microcrystalline cellulose, MCC) could be oxidized quantitatively to cellouronate.
MCC will first be dissolved in (i) an ionic liquid (1-ethyl-3-methylimidazolium acetate, EmimAc) and (ii) aqueous sodium zincate. Mixing MCC-in-EmimAc with excess of water leads to regeneration of cellulose in some form depending on the way of mixing. This will be used as reference treatment.
Mixing of sodium zincate with an excess of aqueous acid precipitates ZnO. The cellulose dissolved in sodium zincate will coprecipitate with ZnO. When the dope is mixed with an aqueous solution of 4-AcNHTEMPO+, the primary alcohol groups of cellulose convert in seconds to aldehyde and carboxylate groups. Adding aqueous phosphoric acid neutralizes the solution and precipitates Zn3(PO4)2. The oxidized cellulose stays in solution. After removing the precipitate by filtration, the oxidized cellulose can be isolated b precipitation with ethanol or by dialysis. The dialysis removes the salts while the cellouronate remains in the dialysis bag. After freeze drying, the product, cellouronate, can be analyzed by NMR spectroscopy.
Read the attached articles and instructions before the laboratory works.
Oxidation and chlorination of lignin Folder
The aim of this work is to verify if
a base, such as acetate ion, can suppress chlorination of lignin during its
reaction with hypochlorous acid (HOCl) which is formed in situ in
chlorine dioxide bleaching. The testing will be done with oxygen delignified
birch kraft pulp at low consistency (for practical reasons). The extent of
chlorination will be measured as the OX value of the pulp after a treatment
with sulfite that removes aliphatic, HexA derived OX. The extent of HexA and
lignin removal will be estimated from UV Raman spectra of the pulps before and
after the treatments.
On the second week, the effect of a tertiary amine catalyst on the oxidation reaction will be studied in pH 7 phosphate buffer. The experiments will be done otherwise similar as described above (and in the instructions). A scientific paper is attached for more reading.