OPTIMIZATION OF THE SODA-ETHANOL DELIGNIFICATION IN THE BIOREFINERY OF RICE HUSK

DAGNINO, E. P.; FELISSIA, F. E.; CHAMORRO, E. R.; AREA, M. C.

Concepción

Congreso; 4 Congreso Latinoamericano sobre Biorrefinerias; 2015

Universidad de Concepción

Lignocellulosicmaterials are an interesting alternative to obtain products with high addedvalue, such as bioethanol, food and cosmetics additives, and adhesives, amongmany others. Rice hulls (RHs) is an abundant residue in the Argentine Northeastregion (provinces of Corrientes, Entre Rios, Santa Fe, Formosa and Chaco). Riceproduction in Argentina in 2012/13 reached 1,397,242 tons, of which about 20% wasRHs [1]. RHs is composed of 48.7% carbohydrates (34.1% cellulose and 14.6%hemicelluloses), 17.2% and 1.8% of insoluble and soluble lignin acidrespectively, 15% of inorganic components, and others [2], so the applicationof the biorefinery concept, i.e. the separation and valorization of itsindividual components, is of high interest. Delignification of RHs pretreatedwith acid (previously optimized process) [2] was carried out using an Organosolvsoda-ethanol process. This treatment is advantageous since the reaction isfaster, it uses smaller amount of soda than the conventional soda process, andthe ethanol can be recovered and reused. A Central Composite Experiment Designof two variables with three replicas of the center point was used. Soda concentrationsbetween 9 and 17g per liter, and ethanol concentrations between 46 and 60% wereevaluated. The liquor was placed in a reactor of AISI 316 stainless steel of180ml, with a closing screw gauge. It was heated in a heat resistant siliconebath to 160¡ãC. The reaction time was 60min, and it was necessary aroundadditional 25min to reach 160¡ãC. The mixture was then cooled in a cold waterbath and filtered through a 100 mesh sieve. The solid was washed repeatedly toremove the remaining solution. The concentration of residual lignin (NRELprocess/TP-510-42618) in the pretreated solid was measured as response variableand delignification relative to initial lignin was calculated on this basis.The results were analyzed using multivariate analysis of variance (ANOVA).Statgraphics statistical software was used, with a level of significance of95%. The adjusted model explained the 92% of the variability. Both variablesshowed significant effect (p ¡Ü 0.05) on the residual lignin in the treatedsolid. The percentage of delignification ranged from 63% in the treatment with13g/l NaOH and 46% EtOH; to 87% in the treatment with 13g/l NaOH and 53% EtOH. Theoptimal response corresponded to 13 g/l NaOH (central point) and 50% EtOH (-0.8as coded variable), with a theoretical value of residual lignin in the solid of3.26% (equivalent to 88% of delignification). In conclusion, the sequence acid/ soda-ethanol allowed hemicelluloses extraction in the first stage and ligninextraction in the second stage. The residual solid was composed almost entirelyof cellulose with approximately 25% of inorganic components, which will beseparated in future studies, to fully implement the biorefinery concept.