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Author Arjun, Kumar K. ♦ Mamata, Mukhopadhyay ♦ Madhu, Vinjamur ♦ Dalvi, Sameer V.
Source IIT Gandhinagar
Content type Text
Language English
Subject Domain (in DDC) Technology ♦ Chemical engineering
Subject Keyword Gas Expanded ♦ Liquids ♦ Mathematical Modeling ♦ Supercritical fluid processes
Abstract Supercritical fluid processes provide a good alternative to conventional nanoparticle production methods. However,use of high pressures (100-400 bar), high temperatures (up to 300 oC) and specially designed fine nozzles (50-70μm) are the main drawbacks of these processes as high pressures require pumps which increase the cost of operation, high temperatures cause loss of activity and thermal degradation of heat sensitive materials and fine nozzles can get clogged anytime leading to the operational difficulty. Therefore, a novel process “PPRGEL”(Precipitation by Pressure reduction of Gas-Expanded Liquids) has been developed for the production of ultra-fine particles using subcritical CO2, without using high pressure pumps and specially designed nozzles. A rapid, high, and uniform supersaturation is attained by a rapid pressure reduction over a CO2-expanded liquid solution from 40−70 to 1 bar at 303 K. This reduces the solution temperature by 30−80 K in a very short span of time (0.5−1.5min) and facilitates precipitation of ultrafine particles. The process has been optimized for the production of temperature drop using various gas (CO2)-expanded liquids (GEL) by systematic parametric studies on the effects of process parameters. This temperature drop was then used for particle production of cholesterol from 100 mL of its acetone and ethanol solutions (5−10 mg/mL) at 40–70 ba and 303 K using a 1 L high-pressure vessel. Particles with a size range of 200 nm to 7 μm and morphologies of near-spherical to needles were produced with a change in operating conditions. Thermodynamic analysis of the process has been carried out for the better understanding of the process. Total volume expansion (T-V-E) criteria have been used to find out the pressure at which the vessel gets completely filled, by calculating molar volumes of CO2-expanded liquids. A model has been developed for the prediction of number of moles of CO2 liberated from the solution after pressure reduction using total volume expansion (T-V-E) criteria, high pressure vapor-liquid equilibria (V-L-E) and low pressure gas-liquid-equilibria (GL-E) for binary CO2 (1)-solvent (2) system. The mathematical modeling of the PRGEL (Precipitation by Pressure Reduction of Gas-Expanded Liquids) process is also done to predict the temperature drop obtained by depressurization and the particle size distribution obtained after precipitation.
Spatial Coverage California, US
Learning Resource Type Article