Intérêt de l'autohydrolyse du bois pour la production de sucres dans une usine de production de cellulose

Transcription

1 Les hémicelluloses du bois : une ressource inexploitée Intérêt de l'autohydrolyse du bois pour la production de sucres dans une usine de production de cellulose Christine CHIRAT Enseignant-chercheur Grenoble INP-Pagora / LGP2 Responsable équipe de recherche Bioraffinerie : chimie et éco-procédés Responsable lot 3-projet PLYWD

2 Historique du projet Polywood Chronology of the PLYWD project 2009 : Brigitte HL from Schneider Electric contacted Grenoble INP-Pagora to launch a literature survey on the possibilities of using wood components to produce biobased and non food BIPLYMERS 2010 : the conclusions of the survey were positive and Schneider Electric and Grenoble INP-Pagora decided to launch a research collaborative project : we have been looking for adequate partners with the help of Philippe le Thuault and his team from AXELERA (competitive cluster in the area of ecoprocesses and green chemistry), and the project was submitted to the 2011 FUI call (FUI: Fonds Unique Interministériel) 2012 : the PLYWD project was granted about 1 million euros funds from FUI, for a total budget of about 5 million euros : running of the PLYWD project.

3 Wood structure H C H H Fibrils H H H H H H Extractives H H H H H H H H H H H H CH Stem Wood cells Lignin Me H Hemicelluloses Cellulose H H H H H H H H H H H o o o

4 Wood composition Cellulose, hemicelluloses and lignin are the most frequently products found in nature. Their are the essential constituants of plants. Chemical composition of wood (excluding extractives and bark) Constituants Softwoods Hardwoods Cellulose Hemicelluloses : -Glucomannans -Xylans Lignin

5 Galactoglucomannans in softwood species Ratio mannose/glucose/galactose; 2,3 to 4,3 / 1 / 0,1 to 1 4 to 9% of acetyl groups Partial structure of -acetylgalactoglucomannans in softwood Ref : T. Stefanovic, D. Perrin, Chimie du bois, Presses Polytechniques Universitaires Romandes, 2009

6 The cellulose industry - Worldwide annual production of cellulosic fibers produced via a chemical way: 135 millions tons, using about 300 millions tons of wood (as dry weight) -95% use an alkaline process (the Kraft process), 5% use an acidic process (sulfite or bisulfite process) -The pulp industry is thus the biggest player in wood chemistry and has been working as biorefineries for more then 100 years. ne of the best example is the Borregaard mill in Norway. - In kraft mills, the main valorised product are the cellulose fibers to make paper and board principally. Cellulose only represents about 40-45% of wood. The other %, lignin and hemicelluloses, are solubilised and degraded in the effluent that is used for combustion. This makes the kraft pulp mills net producers of energy.

7 A kraft mill : an incomplete biorefinery Tall oil and turpentine (extractives) Extra energy (electricity) Cooking chemicals and energy recovery Lignin + degraded hemicelluloses Kraft cook : NaH, Na2S Bleaching Cellulose + C 2 + H 2

8 The cellulose industry - Worldwide annual production of cellulosic fibers produced via a chemical way: 135 millions tons, using about 300 millions tons of wood (as dry weight) -95% use an alkaline process (the Kraft process), 5% use an acidic process (sulfite or bisulfite process) -The pulp industry is thus the biggest player in wood chemistry and has been working as biorefineries for more then 100 years. ne of the best example is the Borregaard mill in Norway. - In kraft mills, the main valorised product are the cellulose fibers to make paper and board principally. Cellulose only represents about 40-45% of wood. The other %, lignin and hemicelluloses, are solubilised and degraded in the effluent that is used for combustion. This makes the kraft pulp mills net producers of energy. -Hemicelluloses could be recovered prior to the process using a green process. The potential quantity is huge : for a mill producing tons of cellulose per year, from to tons of hemicelluloses can be easily extracted without impairing cellulose quality.

9 Extraction and valorisation of hemicelluloses in a cellulose mill Tall oil and turpentine Material and chemicals Cooking chemicals and energy recovery Lignin + degraded carbohydrates Alkaline cook Bleaching Cellulose + C 2 + H 2 Hemicelluloses extraction by autohydrolysis Sugar monomers or oligomers Hemicellulosic ethanol Surface active agents Prebiotics,.

10 Autohydrolysis of wood Treatment of wood chips with water or steam, at a T higher than 150 C : - Acetyl groups contained in hemicelluloses will partly be hydrolysed to yield acetic acid - This decrease in ph, and the high temperature applied will lead to hemicelluloses hydrolysis and solubilisation : oligomers; monomer, sugar degradation products (furfural, HMF) - Lignin fragments can also end up in the hydrolysate Autohydrolysis usually improves delignification in cooking and oxygen bleaching*, which facilitates the production of cellulose *References : Chirat, C., et al Tappi Journal, 12 (11), 49-53, 2013 : SANGLARD, Met alholzforschung, 67 (5), , 2013

11 Schéma général du lot 3-PLYWD Cooking chemicals and energy recovery Lignin +degraded carbohydrates Cuisson PAGRA Blanchiment et purification PAGRA Cellulose FE Extraction des hémicelluloses par autohydrolyse PAGRA + CTP Lavage et fabrication de Panneaux Clextral Hydrolyse secondaire pour l obtention de monomères PAGRA + CTP 11 Purification pour l obtention de sucres répondant aux spécifications du lot 4 NVASEP

12 Partie extraction et hydrolyse secondaire Extraction process 170 C, 1.5 hrs, L/B 3 1 tonne de bois sec contient : 180 kg de C6 issus des galactoglucomannanes Hydrolysat : 48 kg de C6 dont 12 kg de monomères : 25% monomères 12 kg de C5 dont 10 kg de monomères 3,9 kg d acide acétique 1,8 kg HMF et 3,1kg furfural + lignine soluble et insoluble Hydrolyse secondaire acide des oligomères. 100% des oligomères hydrolysés Soit 4% H 2 S 4, 100 C, 90 min Soit 0,5% H 2 S 4, 140 C, 60 min Augmentation acide acétique à 8 kg 12

13 Conclusion - Potential quantities of sugars from wood hemicelluloses are huge and should be available in a near future in wood biorefineries that are currently developing in existing cellulose production sites (cf projet FUI BI3) - It has been shown that cellulose of good quality could be obtained, suitable for viscose application - Aotohydrolysates contain contaminants (organic acids, furfural, HMF, lignin) that have to be eliminated to a certain degree depending on the final application

14 Thank you for your attention Contact : christine.chirat@pagora.grenoble-inp.fr