Prereadings, supporting readings, lecture slides and video recordings will be shared under this section.
Introductory lecture March 1st Folder
Lecture of March 8th (nanostructure) Folder
Lecture of March 15th (reactivity) Folder
Lecture of March 22nd (cellulose oxidation) Folder
Lecture of March 29th (lignin and HexA with HOCl) Folder
Lecture of April 19th (pulp bleaching) Folder
Read Chapters 3.3.3-3.3.8 (p. 255-271) from European Commission's JRC Science and Policy Report "Best Available Techniques (BAT)
Reference Document for the
Production of Pulp, Paper and Board" (Best Available Techniques (BAT) Reference Document for the Production of Pulp, Paper and Board (europa.eu)). These chapters describe the current BATs for bleaching of kraft pulps. Aspects to be considered included emissions into waters (AOX, COD, chlorate, toxicity, etc.) but use of water and energy and techno economical aspects must be considered as well.
After a short introduction, the lecture will continue with group discussions on the aspects of the BAT document. Each group will present a summary on their discussion regarding possible development needs in this field. We will then continue the discussion jointly and the more detailed lecture on pulp bleaching will be on April 26th. Aspects to be considered include at least emissions into waters (AOX, COD, chlorate, toxicity, etc.), use of water and techno economy.
Lecture of April 26th (pulp bleaching) Folder
Lecture of May 3rd (nucleophilic reactions) Folder
Nucleophilic substitution reactions are mostly responsible for the depolymerization of lignin and polysaccharides in chemical pulping processes. In acidic conditions the degradation follows SN1 mechanism and the degradation rate depends on the acidity of the treatment but not on the nucleophiles. In neutral and alkaline conditions SN2 mechanism dominates and the reaction rate depends on the nucleophilicity and concentration of the nucleophiles. In kraft pulping ionized hydroxyl groups act as intramolecular nucleophiles. However, intermolecular reactions by strong sulfur nucleophiles (hydrogen sulfide and mercaptide ions) may also take place. Some other sulfur compounds, such as sulfite, thiosulfate and polysulfide ions, are even stronger nucleophiles.
The reading includes a paper on the nucleophilicity of a larger number of nucleophiles. I have been using table III of this paper in developing ideas on modified lignocellulose treatments. The n values (relative reaction rate in logarithmic scale) for CH3I tell about the nucleophilicity in SN2 reactions. Another paper describes the reactions that take place when pulps are treated with strongly nucleophilic neutral sulfite solutions. In this study we originally planned to demethylate the residual lignin for improving its reactivity towards oxygen but to our surprise many other reactions, such as depolymerization of cellulose and degradation of lignin and HexA took also place.
Lecture of May 10th Folder
Delignification is often limited by the porosity of the cell wall and occurrence of covalent bonds between lignin and the cell wall polysaccharides. During this lecture I want to pay attention on these factors especially.