Structural Changes in Microcrystalline Cellulose in Subcritical Water Treatment

Tolonen, Lasse; Zuckerstätter, Gerhard; Penttilä, Paavo A.; Milacher, Walter; Habicht, W.; Serimaa, Ritva; Kruse, Andrea; Sixta, Herbert

doi:10.1021/bm200351y

Cited by 41 publications

(43 citation statements)

References 33 publications

(78 reference statements)

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“…The crystallinity analysis of the whiskers and MCC samples resulted in values between 50 and 55 %, with the exception of 58 % for the freeze-dried cotton whiskers. Even though the crystallinity values are not as high as some of those reported for cellulose whiskers in literature (Moon et al 2011), our values are assumed to give an accurate estimate of the absolute crystallinity (Park et al 2010), because they are based on the analysis of the entire WAXS pattern and they have been previously shown to be in accordance with NMR crystallinities of MCC (Andersson et al 2004;Tolonen et al 2011). …”

Section: Chemical and Crystal Structurementioning

confidence: 89%

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

et al. 2012

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Cellulose whiskers were prepared from wood-and cotton-based microcrystalline cellulose and dried by two methods: freeze-drying or air-drying. The effect of drying method on the properties and structure of the whiskers were studied. Furthermore, the influence of the source of cellulose on the nanoscale structure was investigated. Drying method was observed to slightly influence the thermal stability of cellulose whiskers, whereas the char residue varied significantly depending on the drying process performed. Small-and wide-angle X-ray scattering and solid state nuclear magnetic resonance spectroscopy were used to examine the crystallinity and nanoscale structure of the dried whiskers. It was observed that the crystal structure and crystallinity of cellulose whiskers remained during all treatments, whereas their nanoscale structure was significantly influenced by drying method, neutralization, and source of cellulose. Relationships between thermal behavior and nanoscale structure were reported and discussed.

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Section: Chemical and Crystal Structurementioning

confidence: 89%

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

et al. 2012

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“…However, both methods can be interpreted with a simplified twophase model in which a material consists of only purely crystalline and amorphous components. In this model the paracrystalline contribution is included in the NMR-crystallinity (Tolonen et al 2011). This streamlined model is used in this article when NMRand XRD-crystallinities are compared.…”

Section: Discussionmentioning

confidence: 99%

“…MCC1 is known as Avicel PH-102, MCC2 as Vivapur 105 and MCC3, which was measured earlier (Tolonen et al 2011), is from Merck (No. 1.02330.0500).…”

Section: Samplesmentioning

confidence: 99%

Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

2016

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Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger (n ¼ 16) and more varied collection of samples than previous studies have presented is used. In particular, samples (n ¼ 6) with low crystallinity and small crystallite sizes are included. A good linear correlation (r 2 ! 0:90) between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.

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“…The dominant sugar-based macromolecule of wood cell walls, cellulose is known for its ability to form very stable aggregated structures which are only accessible for water in harsh physical conditions of elevated temperature and pressure (above 200°C and 25 MPa;Deguchi et al 2008). Although cellulose is also thermally degraded under such conditions (Tolonen et al 2011(Tolonen et al , 2013, the crystals are seen to completely dissolve in water under very short reaction times (less than 10 s) forming amorphous cellulose fragments (Deguchi et al 2008;Tolonen et al 2013), which nonetheless re-crystallises upon drying (Tolonen et al 2011). From this it is seen that cellulose has an innate tendency to form aggregated structures which are partly inaccessible for water.…”

Section: Introductionmentioning

confidence: 99%

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

2017

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The first drying of wood cell walls from the native state has sometimes been described as producing irreversible structural changes which reduce the accessibility to water, a phenomenon often referred to as hornification. This study demonstrates that while changes do seem to take place, these are more complex than what has hitherto been described. The accessibility of wood cell wall hydroxyls to deuteration in the form of liquid water was not found to be affected by drying, since vacuum impregnation with liquid water restores the native cell wall accessibility. Contrary to this, hydroxyl accessibility to deuteration by water vapour was found to decrease to different levels depending on the drying conditions. Vacuum drying at 60°C for 3 days reduced the accessibility more than drying for 1 day at 103°C without vacuum. Drying for 3 days at 103°C increased the hydroxyl accessibility compared to 1 day. Moreover, the decrease in hydroxyl accessibility to deuteration by water vapour induced by the first drying could be at least partially erased by subsequent vacuum impregnation with liquid water, indicating reversibility. For the drying of solid, non-degraded wood cell walls the results challenge the often supposed process of hornification, understood as a permanent decrease in hydroxyl accessibility to water.

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Structural Changes in Microcrystalline Cellulose in Subcritical Water Treatment

Cited by 41 publications

References 33 publications

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

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