Sub-/Supercritical water hydrolysis
- How does it work?
- What can it be used for?
- What can it not be used for?
- Related Facilities
- Further Information
|Key words||Polymer hydrolysis, subcritical/supercritical fluid, biomass cleavage, dissolving, sustainability, hydrothermal, critical point, diffusivity, solvent power, ion product|
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.
|Important process parameters||
|Important product parameters||
What can it be used for?
|Operations||Conversion and hydrolysis of biomass.|
|Solutions for short comings||
What can it NOT be used for?
|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.|
|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.|
Facilities that might be interesting for you
|Institutes||DIL, TU Berlin, Karlsruhe Institute of Technology, University of Hamburg|
|Companies||Mothes Hochdrucktechnik, SITEC, Uhde-HPT|
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not applicable 2.1.1 physical, chemical separation, conversion biotechnology, nanotechnology, other Sciencedirect, Web of science Search terms: supercritical water, subcritical water, hydrothermal hydrolysis WikiSysop :Template:Review document :Template:Review status