59. Thakur, Ranjit; Gupta, Ram B., Rapid expansion of supercritical
solution with solid cosolvent (RESS-SC) process:
Formation of 2-aminobenzoic acid nanoparticle, Journal of Supercritical Fluids
(2006), 37, 307-315.
A high soly.
in supercrit. fluid is desired for performing rapid expansion of supercrit. solns.
(RESS) to produce particles. Unfortunately, extremely
low soly. of polar compds. in supercrit.
CO2 makes RESS unviable for com. applications.
Liq. cosolvents can
improve the soly., but are unsuitable due to the dissoln.
of particles in expansion chamber. This work uses a solid cosolvent,
menthol, for 2-aminobenzoic acid (ABA)
solubilization in CO2. ABA soly. is increased from
57-6600 mmol/mol at 236 bar and
50° by using menthol-satd. CO2. The other
drawback of the conventional RESS process is the size of the particles obtained
which is mostly in the micron range, due to growth by agglomeration in
expansion chamber. In
rapid expansion of supercrit. soln. with solid cosolvent (RESS-SC) process, solid cosolvent
hinders the particle growth resulting in small nanoparticles. For example, RESS-SC process produced
.apprx.80 nm size ABA
particles, which is significantly smaller than .apprx.610 nm size particles
obtained from RESS process. Menthol is
easily removed from ABA
nanoparticles by sublimation (lyophilization). DSC, XRD and SEM analyses are used to
characterize the particles.
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