Influence of viscosity on crystallization of sugars and sugar alcohols from aqueous solutions

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School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2024-11-14
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Date

2024

Department

Kemian tekniikan ja metallurgian laitos
Department of Chemical and Metallurgical Engineering

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Mcode

Degree programme

Language

en

Pages

75 + app. 63

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Aalto University publication series DOCTORAL THESES, 246/2024

Abstract

This dissertation presents a detailed study on the crystallization of sugars and sugar alcohols, with a particular focus on the crucial role of viscosity in influencing process efficiency, crystal morphology, and product purity. The research covers various crystallization techniques, including cooling, evaporative, and antisolvent methods, applied to substances such as xylitol, α-D-galactose, glucose, erythritol, and xylose. High viscosity, especially in xylitol solutions, was found to impede crystallization by slowing nucleation and crystal growth. The addition of ethanol as an antisolvent effectively reduced viscosity by up to 40%, leading to more uniform crystals and improved filterability. In a laboratory-scale stirred reactor, optimal crystallization conditions for xylitol included a tip speed of 0.90 m/s and a temperature range of 40 °C to 25 °C. For α-D-galactose, a stepwise cooling method was most effective in managing high-viscosity industrial side streams. Moreover, the research expanded its focus to include other sugars and sugar alcohols, such as glucose, xylose, and erythritol, providing a broader understanding of how different viscosities impact crystallization dynamics. The stark contrast between lower viscosity of erythritol and xylitol's higher viscosity illustrated the direct correlation between viscosity and crystallization efficiency. Simulations demonstrated how elevated viscosity can reduce mass transfer rates and extend micromixing times. VisiMix simulations further provided valuable insights into the scale-up process, showing how changes in reactor size and mixing conditions influence crystallization dynamics in substances with varying viscosities. The dissertation also tackled the challenges of directly crystallizing xylitol from impure, viscous fermentation broths. Despite the complexities introduced by high viscosity due to impurities, the study developed effective methodologies, achieving xylitol crystal purity levels of up to 99% using chromatographic separation pretreatment. Overall, this dissertation emphasizes the importance of viscosity management in crystallization processes, offering insights that bridge the gap between laboratory research and industrial application. The findings highlight the critical role of viscosity in achieving efficient, high-purity crystallization in biorefinery applications.

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Supervising professor

Louhi-Kultanen, Marjatta, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland

Thesis advisor

Louhi-Kultanen, Marjatta, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland

Keywords

batch crystallization, xylitol, erythritol, galactose, xylose, sugar alcohols, sugars, viscosity, mixing, mass transfer, crystal size distribution

Other note

Parts

  • [Publication 1]: Zaykovskaya, Anna; Louhi-Kultanen, Marjatta. 2023. Batch crystallization of xylitol by cooling, evaporative, and antisolvent crystallization. Crystal Growth & Design, volume 23, issue 3, pp.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202302282222
  • [Publication 2]: Zaykovskaya, Anna; Louhi-Kultanen, Marjatta. 2023. Cooling and evaporative crystallization of α-d-galactose from a highly viscous industrial side stream. Chemical Engineering and Technology, volume 46, issue 11, pp. 2330-2336.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202311016724
  • [Publication 3]: Zaykovskaya, Anna; Amano, Bernadeth; Louhi-Kultanen, Marjatta. 2024. Influence of viscosity on variously scaled batch cooling crystallization from aqueous erythritol, glucose, xylitol, and xylose solutions. Crystal Growth & Design, volume 24, issue 7, pp. 2700–2712.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202404113036
  • [Publication 4]: Zaykovskaya, Anna; Illa, Mitra; Ginter, Michael; Temmel, Erik; Schwiderski, Martin; Stepanski, Manfred; Louhi-Kultanen, Marjatta. Crystallization-based purification of xylitol produced by biotechnological route. Submitted to the journal Food and Bioproducts Processing in 2024

Citation

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https://urn.fi/URN:ISBN:978-952-64-2134-6

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[diss] Kemian tekniikan korkeakoulu / CHEM