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Sub-/Supercritical water hydrolysis

Identification

Key words Polymer hydrolysis, subcritical/supercritical fluid, biomass cleavage, dissolving, sustainability, hydrothermal, critical point, diffusivity, solvent power, ion product
Latest version 2012/07/17
Completed by DIL

How does it work?

Primary objective Conversion of polymers, winning of functional ingredients
Working principle Change of physicochemical properties of water to increase solvent power and catalyse hydrolytic reactions.

By increasing pressure and temperature the physicochemical properties of water are varied. A decrease of dielectric constant results in an increasing solvent power for non-polar substances. By dissociation of water, the ion product increases and hydrolytic reactions are catalysed. Exposure to sub- and supercritical water therefore allows hydrolysis of biopolymers such as cellulose, starch or proteins or other by-products of food- and bio-processing. Termination of the reaction can be achieved by pressure release or temperature reduction to allow winning of intermediate products. Nevertheless, major challenges of the technique are potential side reactions, the formation of by products or undesired hydrothermal reactions such as caramellization or Maillard reactions. From a technical point of view the aggressivity of sub- and supercritical fluids and related corrosion of reactors, pumps and valves have to be considered. Major benefits of this technique include short residence times and continuous operability. In comparison to acid hydrolysis no neutralization is required. In comparison to an enzymatic treatment a higher conversion rate but lower specificity is observed.

Images
Additional effects
  • Thermal degradation
  • Extraction of functional ingredients
  • Removal/Cleavage of toxic substances
Important process parameters
  • temperature
  • time
  • pressure
Important product parameters
  • pH
  • presence of catalysts

What can it be used for?

Products
  • Liquids, semisolid and solid products
  • Biopolymers such as cellulose, starch, pectin or lignin
Operations Conversion and hydrolysis of biomass.
Solutions for short comings
  • Biopolymer hydrolysis
  • Dissolution of non-soluble polymers
  • Waste degradation

What can it NOT be used for?

Products
  • Not suitable for heat sensitive media, due to the high thermal stress.
  • Not suitable for oxidation sensitive media.
  • Mainly applicable for pumpable media, otherwise batch operation might be required.
Operations For dissolving and hydrolysis, mainly. Extraction associated to hydrolysis of extracts.
Other limitations Considerable investment and maintenance costs, corrosion of equipment.
Risks or hazards Formation of undesired, potentially toxic substances.

Implementation

Maturity Technical scale for food applications; industrial scale equipment available for hydrolysis of toxic waste material.
Modularity /Implementation An implementation in existing lines is possible; the hydrolysis process is scalable based on temperature-time-conditions. More research is needed in order to remove undesired substances at downstream processing.
Consumer aspects Not known.
Legal aspects Not known. Heat/pressure application is commonly accepted, but the content of undesired substances has to be monitored.
Environmental aspects Energy efficient if heat recovery is applied. No organic solvents or other chemical/agent required.

Further Information

Institutes DIL, TU Berlin, Karlsruhe Institute of Technology, University of Hamburg
Companies Mothes Hochdrucktechnik, SITEC, Uhde-HPT
References
  1. Brunner, G. (2009). Near critical and supercritical water. Part I. Hydrolytic and hydrothermal processes. The Journal of Supercritical Fluids 47(3): 373-381.
  2. Doncheva, D. and G. Brunner (2007). Cleaning of animal-derived bone material for implantation by combined extraction/reaction process of organic matrix with subcritical water and characterisation of hydrolysates. Proceedings of Fifth International Symposium on High Pressure Process Technology and Chemical Engineering Segovia, Spain.
  3. He, W., G. Li, L. Kong, H. Wang, J. Huang and J. Xu (2008). Application of hydrothermal reaction in resource recovery of organic wastes. Resources, Conservation and Recycling 52(5): 691-699.
  4. Kabyemela, B. M., T. A. Takigawa, T. Adschiri, R. M. Malaluan and K. Arai (1998). Mechanism and kinetics of cellobiose decomposition in sub- and supercritical water. Industrial and Engineering Chemistry Research 37: 357-361.
  5. Kang, K., A. Quitain, H. Daimon, N. R., N. Goto, H. Y. Hu and K. Fujie (2001). Optimization of amino acids production from waste fish entrails by hydrolysis in sub- and supercritical water. Canadian Journal of Chemical Engineering 79: 65-70.
  6. Khajavi, S. H., Y. Kimura, T. Oomori, R. Matsuno and S. Adachi (2005). Kinetics on sucrose decomposition in subcritical water. Lebensmittel-Wissenschaft und Technologie. 38(297-302).
  7. Rogalinski, T., K. Liu, T. Albrecht and G. Brunner (2008b). Hydrolysis kinetics of biopolymers in subcritical water. The Journal of Supercritical Fluids 46(3): 335-341.
  8. Wang, J.-s., Z.-y. Wei, L. Li, K. Bian and M.-m. Zhao (2009). Characteristics of enzymatic hydrolysis of thermal-treated wheat gluten. Journal of Cereal Science 50(2): 205-209.
  9. Watanabe, M., Y. Aizawa, T. Iida, T. M. Aida, C. Levy, K. Sue and H. Inomata (2005a). Glucose reactions with acid and base catalysts in hot compressed water at 473 K. Carbohydrate Research 340(12): 1925-1930.

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Created by 78.48.235.35 on 23 February 2011, at 10:31