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: January 8th 2007

	Scientific report of the LGP2 (2002-2005)
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Researchers of the LGP2 (EFPG, INPG, CNRS, CTP) (November 2006)

	Documents taken from the "Scientific Report of the Laboratory of Pulp and Paper Science and Graphic Arts - UMR 5518 Grenoble - France Janvier 2002-Novembre 2005" recherche@efpg.inpg.fr

II - Chemical processes

II - 1 - Introduction

The manufacture of cellulosic fibres from lignocellulosics material is a sophisticated chemical process. The objective is to remove lignin with chemicals which do not affect cellulose severely. The fact that these two components are intimately mixed inside the fibre walls makes this operation particularly difficult. A mixture of sodium hydroxide and sodium sulphide is generally, applied under drastic conditions (160 – 170°C). Lignin is then depolymerised by cleavage of interunit alkyl – aryl ether bonds. However, the carbohydrate fraction (hemicellulose, cellulose) is also partly hydrolysed by the alkaline medium.80 % of the hemicellulose are lost. Cellulose depolymerisation occurs too, but can be limited at a level which does not impair the fibre properties.

The two problems on which most of the research effort of the Chemical processes team is focussed are:

• the low yield of fibre production. More than 50 % of the wood components are dissolved during this operation. As said before, this reflects the loss of most of the hemicelluloses. Increasing the pulp yield would save the raw materials.
• after treatment, the fibres are brown because of the presence of some coloured residual lignin fragments. It is then necessary to perform bleaching stages, at least for the production of white papers. Till recently, oxidising agents such as chlorine, chlorine dioxide and sodium hypochlorite were used. However the new environmental regulations make it necessary to replace these chlorinated reagents by cleaner oxidising chemicals such as oxygen, hydrogen peroxide and ozone.

The topics under investigation in our team are the following:

• macromolecular structure of lignin in lignocellulosic substrates. 13C NMR, 19F NMR, FTIR, GC–MS spectroscopies are used in combination with isolation or controlled degradation techniques (enzymatic extraction, acidolysis, pyrolysis…)
• effect of lignin structure on delignification and bleaching
• modelling of delignification and bleaching processes from mechanistic and kinetic data
• improvement of mass transfer
• development of clean cooking and bleaching processes
• behaviour of fibre components during ageing and recycling.

The main partners in these studies are the French Agency for Environment and Energy (ADEME), CTP, ATOCHEM, AIR LIQUIDE and DEGREMONT.
Cooperation with foreign companies and institutes is also very active in the frame work of European Projects (FAIR and Quality of life).

The two main areas of research investigated these last three years are shortly presented below.

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