Cellulose co-crystallization and related phenomena occurring in hydrothermal treatment of sugarcane bagasse

Abstract

Lateral dimensions of cellulose crystallites have been widely reported to increase as plant biomasses are submitted to a variety of high-temperature chemical treatments. Cellulose co-crystallization is often indicated to be the phenomenon underlying crystallite dimensional change, but precise mechanisms and relationships with concurrent phenomena are not well understood. This work investigates cellulose structural evolution in sugarcane bagasse submitted to wide range (160-190°C, up to &50 % solubilization) of hydrothermal treatments, performed in pressurized liquid hot water. Cellulose structural characterization combines fiber and powder X-ray diffraction with analysis of two-dimensional diffraction patterns employing the Cellulose Rietveld Analysis for Fine Structure (CRAFS) model. We observe that increases in lateral dimensions of cellulose crystallites closely follow changes in bagasse chemical composition. For a given composition, treatment temperature per se seems to be secondary for changes in crystallites. Partial cellulose de-crystallization and decreasing distortion of crystallite unit cell are found to co-occur with increasing crystallite lateral dimensions. Our interpretation of results emphasizes the importance of removing hemicelluloses acting as intercrystallite spacers, which seems to be the limiting factor for cellulose cocrystallization.

Lignin contributions to the nanoscale porosity of raw and treated lignocelluloses as observed by calorimetric thermoporometry

“…Comparison among the raw samples shows significant variability in lignin contents. Hydrothermal treatments increase lignin contents (as percentage of treated solid mass) because hydrothermal conditions remove mainly hemicelluloses, with much less removal of lignin (Garrote et al, 1999;Driemeier et al, 2015). On the other hand, major removal of lignin takes place in the delignification step, which is clear from data of Table 1.…”

“…These feedstocks were submitted to hydrothermal treatments (i.e., pressurized hot water) performed in a 195 mL batch reactor at 180 • C for 1 h in a solid:liquid ratio of 1:10 (Garrote et al, 1999;Driemeier et al, 2015). Reaction products were washed until neutral pH.…”

“…The selected samples submitted to acidic treatments include: poplar wood submitted to steam explosion at either 160 • C or 200 • C, depithed sugarcane bagasse submitted to hydrothermal treatments at 170 • C for either 25 min or 90 min (Driemeier et al, 2015), and sugarcane bagasse submitted to dilute acid treatments in either 1.5% (m/v) H 3 PO 4 or 1% (m/v) H 2 SO 4 (Silva, 2014). The delignified samples selected from lab records were previously reported (Driemeier et al, 2012).…”

Produção de etanol celulósico por >i<Spathaspora passalidarum>/i< a partir do bagaço de cana-de-açúcar: estratégia para melhorar fermentabilidade e estudo do perfil metabólico durante fermentação de hidrolisado hemicelulósico

“…Tais arranjos tornam a celulose um polímero rígido, insolúvel e resistente a depolimerização (MOSIER, 2005b). Técnicas, como a difração de raios X tem sido utilizada para mensurar a cristalinidade da celulose em material bruto e pré-tratado (DRIEMEIER et al, 2011(DRIEMEIER et al, , 2015…”

“…13,14 Since hydrothermal pretreatments are already employed at commercial scale, the advantages and disadvantages of the processes have been clearly diagnosed and thereby provide a benchmark for new concepts. Disadvantages of hydrothermal processes include the generation of inhibitory compounds toxic for fermentation, 15,16 chemical condensation of lignin, which impedes its conversion into high-value chemicals, 17,18 and high temperature introduction of the morphological cohesive phenomena of cellulose cocrystallization 12,19,20 and lignin aggregation. 12,21−23 Furthermore, due to the acidity of the medium and abrasiveness of the feedstock, industrial-scale pressurized reactors for biomass pretreatment are complex and costly, and feeding biomass into pressurized reactors has proven to be nontrivial.…”