specialists in production of supercritical fluids systems.

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One of the first plants produced in ItalyA supercritical fluid (SCF) is a low molecular weight fluid, having critical temperature next to the environmental one (TC~10÷40ºC) and a not too high critical pressure (PC~40÷60 bar). Light hydrocarbons have these physical properties, but they have flammability and toxicity problems. Some chlorine-fluorocarbons are fit for the utilization, but they are expensive if obtained with high purity degree and nowadays they have been banished due to the environmental unacceptability. Carbon dioxide, although its slightly higher critical pressure(PC=72.1 bar), offers other advantageous properties that make of it the most utilized fluid for SC applications:

  • It is not flammable;
  • It is environmentally friendly;
  • It is not toxic;
  • It is cheap also at high purity level.

The possibility to modulate SCFs density, thanks to modest temperature and pressure variations, especially around the critical point (CP), represents the characterizing factor of these fluids. In this way it is possible to introduce pressure as an addictive variable in the control of the separation e/o extraction process.At the current state, it is our belief that the utilization of supercritical fluids has interesting industrial perspectives in the cases in which:

  • Small volumes of samples to treat are available, like in the food field;
  • There is a high value in the samples to treat;
  • There are thermolabile substances altered with the common technologies, with a consequent loss in the product activity.

The utilization of supercritical fluids as solvents in the separations techniques started in the last two decades, and it found wide application in the extraction operations (SFE – Supercritical Fluid Extraction). The limit represented by the high plant cost always limited the utilization in the commercial field, and only recently the increase in the raw materials, manpower, energetic resources cost made possible their application, together with the advantages of being able to work with reduced volumes and of the separation ease of the solvent from the extracted product.After the first industrial applications of supercritical fluids technologies (decaffeinization, purification) and two decades of R&D in the food field, nowadays SCF utilization finds applications in the pharmaceutical industry. One particular interest has risen about the possibility to reduce the size of valuable and thermolabile substances, such as pharmaceutical products. In fact the control of drugs size would allow a specific utilization in the  administration to the patients. Conventional size reduction processes show certain disadvantages:

  • during grinding, because of the high particles friction, temperature undergoes localized increases and consequently substances degradation;
  • during crystallization solvent englobement always happens, and it is difficult to control the precipitate size.

Anyway, current techniques do not allow neither particles size nor particle morphology control. Recent SCFs applications demonstrated the possibility to overcome these limits, opening a new path in the micronization field (Particle Science). The utilization of SCFs in industrial processes remains strictly bond to purification, extraction, solubilization and backup for other technologies issues. The SFE fundamental properties can be summarized as follows:

  • solvent power and selectivity of the employed fluid,
  • the utilized fluid is a non flammable gas having a total environmental acceptability;
  • operative temperatures make a cold technology of it;
  • it is possible to modulate pressure and temperature to optimize both the extraction and separation processes.

In reference to the flavors and essences production, a rapid analysis allows to state that, compared to the classic production processes, SFE totally eliminates the issues connected to the organic solvents utilization and steam current extraction:

  • in the solvent extraction an amount of solvent remains in the final product;
  • in the second case, high temperatures and water reactivity are such to generate product composition modifications, either qualitative and quantitative ones. Despite this problems, the technique remains a valuable one, employable only in particular niches interested in high added value extracts or where classic technologies jeopardize the extract quality.

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