Kinetic Modeling of Hemicellulose Hydrolysis from Triticale Straw in a Pressurized Low Polarity Water Flow-Through Reactor

Abstract

Two classic and one modified kinetic models were used to study the hydrolysis of triticale straw using pressurized low-polarity water (PLPW) in a flow-through reactor. Results indicated that for these experiments hemicellulose did not follow a biphasic reaction pathway. High yields of 72% were achieved at 170 °C, but these decreased to 60% at 150 °C and only 13% at 130 °C. The kinetics were controlled more by increases in temperature than flow rate in the reactor. Increases in flow rate reduced the overall hemicellulose yields but increased the portion extracted as oligomers. The kinetic rate constants when plotted as an Arrhenius-type temperature relationship displayed a dependency with flow rate. Curvature in the Arrhenius plots of the kinetic rate constants was due to differences in acetic acid formation with temperature. A modified monophasic kinetic model which incorporated reactor geometry and fluid flow was successful at modeling the yield of xylo-oligomers and monomers in PLPW.

Autohydrolysis of Hemicelluloses from Sugarcane Bagasse During Hydrothermal Pretreatment: a Kinetic Assessment

“…The poor fit of data, mainly from 20 to 30 min, suggests that the sugars were produced by different mechanisms, i.e., either from oligomers or directly from hemicelluloses. Similar behavior was previously reported elsewhere [12,31]. The difference was particularly notable for the decay curve of sugars, which shows a less pronounced decay for the experimental data compared to the obtained model.…”

“…Under autohydrolysis conditions, there is a significant change of pH during the reactions and, consequently, the observed rate constants should include a term for the acid concentration. As described by Pronyk and Mazza [12], this increase of acid concentration at higher temperatures (as indicated by pH values in the present study) resulted in a deviation of the Arrhenius-type profile (Fig. 5, light blue diamond), wherein there were no isoacidic conditions along the reactions.…”

“…Different from the model proposed by Saeman [11], which considers a one-step reaction of carbohydrates, Pronyk's model describes the hydrolysis of hemicelluloses into xylooligomers prior to the formation of monomeric sugars, as represented in Eq. 1 [12].…”

“…Beyond this assumption, some authors have presented a different approach to include the formation of oligomer in kinetic models for autohydrolysis of hemicelluloses. As an example, Pronyk and Mazza [12] considered one-and two-step models of hemicellulose hydrolysis. Garrote et al [15] classified the oligomers into high and low molecular weight compounds, whereas Conner [16] assumed the occurrence of fast and slow rates for the hydrolysis of hemicelluloses.…”

Kinetics and genetic algorithm study of acid catalysed hydrolysis of water hyacinth biomass

“…4 Feedstock in the form of lignocellulosic biomass makes the process cheap, viable, and eco-friendly. It falls under second generation of energy production which addresses the major drawback of competition with food a) Author to whom correspondence should be addressed.…”