Kinetic and modeling investigation on two-stage reverse-flow reactor as applied to dilute-acid pretreatment of agricultural residues

Kinetic characterization of biomass dilute sulfuric acid hydrolysis: Mixtures of hardwoods, softwood, and switchgrass

“…According to that study, while mixtures, such as corn cobs and corn stover may be pretreated simultaneously because each has similar kinetics, hardwoods have much slower kinetics in comparison, and need higher acid concentrations and/or temperatures. This leads to the conclusion that there is a limit to which mixtures of biomass could be most efficiently utilized, 11 and that the dilute acid hydrolysis pretreatment process may still need to be optimized for different groups of mixtures. The high xylose yields obtained in our current study show that the kinetics of the five biomass species are similar, and that mixtures of these species may be pretreated to achieve the expected xylose yields obtained from single species experiments.…”

“…19 However, none of these studies focused specifically on the effects of feedstock mixtures on hemicellulose hydrolysis kinetics with comparison to pure species data. One study on biomass mixtures 11 states that there are significant kinetic differences in the various types of biomass. According to that study, while mixtures, such as corn cobs and corn stover may be pretreated simultaneously because each has similar kinetics, hardwoods have much slower kinetics in comparison, and need higher acid concentrations and/or temperatures.…”

“…This approach also depends on the biphasic relationship of biomass, and utilizes two first-order rate constants for the breakdown of fast and slow reacting xylan, and is shown in Eq. 2 11 …”

Countercurrent Process for Lignin Separation from Biomass Matrix

“…This is because Schell et al (2003) conclude that the most important predictions from their kinetic modeling of biomass pretreatment are that low pHs are required to achieve the highest xylose yields and that yields improve at higher temperatures (although shorter residence times are required). Esteghlalian et al (1997) also reported similar kinetic behavior, even though other researchers have reported that temperature has only a modicum of effect on maximum xylose yields (Chen et al 1996;Wright and d'Agincourt 1984). …”

Delignification Process of Agro-Industrial Wastes an Alternative to Obtain Fermentable Carbohydrates for Producing Fuel

“…High activation energies may serve as an indication that the system follows a chemical reaction-limited kinetics rather than a mass transport limited kinetics. Some interesting conclusions from the diverse dilute sulfuric acid kinetic studies are: (i) xylose yields are favored at high temperatures and short times (Chen et al, 1996;Esteghlalian et al, 1997;Grohmann et al, 1985;Lee et al, 2000;Morinelly et al, 2009;Schell et al, 2003); (ii) selectivity defined in terms of either Arrhenius constants ratios or activation energies ratios shows that high temperatures have an enhancing effect on the hemicelluloses breakdown to oligomers (i.e., in Fig. 7a, E 1 /E 2 > 1 ), however, the hydrolysis of oligomers is less favored than the formation of degradation products (i.e., in Fig 7a, E 2 /E 3 < 1) (Morinelly et al, 2009); (iii) high solids concentration is desirable because in addition to help the process economics, less degradation of xylose to furfural is obtained, and these solids act as a barrier that protects monomers from degradation, though the main drawback of is slow reaction rates (Morinelly et al, 2009); (iv) total carbohydrates yields are lower at pilot scale than they are in laboratory scale, demonstrating the importance of pilot plant scale measurements in the scaling up of the process (Schell et al, 2003); (v) countercurrent shrinking bed reactors result in solubilisation of both cellulose and hemicellulase, but selectivity of desired monomers is better than with other reactors because of lower residence times (Lee et al, 2000); and (vi) no direct comparisons among different studies can be made due to important differences in reaction conditions.…”