Handbook of Solvents - George Wypych - ChemTech - Ventech!

1422 Aydin K. Sunol and Sermin G. Sunol
Figure 21.1.4. Annual number of patents related to supercritical fluids.
21.1.1.1 A promising path to green chemistry
One of significant paradigm shifts in chemical processing for the new millennium is the increased
use of environmentally benign technology. The effectiveness of green solvents
such as supercritical water and supercritical carbon dioxide for carrying out reactions, difficult
separations, and materials processing is naturally very promising. The effectiveness of
the supercritical solvents is related to their state, critical temperature, and pressure. Obviously,
synergy between the physical characteristics of solvent and the conditions favorable
for the desired chemistry is of paramount importance for the success of the application.
21.1.1.2 Unique and tunable physico-chemical properties
Supercritical fluids have the mobility of gases and the dissolving power of liquid solvents
resulting in efficient penetration into porous matrices, high mass transfer rates, and high solvency.
Furthermore, these properties are extremely sensitive to perturbations in temperature,
pressure and composition resulting in innovative processing concepts. Furthermore,
tailored products with tunable performance could be produced through synthesis and creative
operating policies. Thus, over the last three decades, a spate of supercritical processes
have been developed particularly for manufacture of high value added products that are superior
in performance and exhibit conscious regard for a more socially responsible manufacturing
practice.
21.1.1.3 Sustainable applications in many different areas
Despite the higher capital charges associated with relatively high pressures, the necessity to
often add a new component into the processing environment, and operational challenges at
conditions foreign to most process engineers, the interest in supercritical fluids had been
growing steadily since the early eighties beyond the select number of areas. We see applications
in the food and beverage industries, pharmaceutical, biomedical, micro-electronic industries,
textiles, forest products, petrochemicals, chemicals, environmental clean-up,
syn-fuel production, polymeric materials, ceramics, auto industry, coatings and paint industry,
energetic materials, and fuels. As depicted in Figures 21.1.2-4, the number of the publications,
dissertations, and patents in the area are still growing from one year to next.