C. Domingo et al., PRECIPITATION OF ULTRAFINE ORGANIC-CRYSTALS FROM THE RAPID EXPANSION OF SUPERCRITICAL SOLUTIONS OVER A CAPILLARY AND A FRIT NOZZLE, The Journal of supercritical fluids, 10(1), 1997, pp. 39-55
Benzoic acid, salicylic acid, aspirin or phenanthrene was dissolved in
supercritical CO2 and precipitated as a fine powder by the rapid expa
nsion of the supercritical solution over a nozzle (RESS process). A ne
w kind of expansion device is presented (the frit nozzle) which can be
manufactured more easily than the capillary nozzle, especially if sma
ll holes are required. The performances of the two expansion devices a
re compared. The process operating conditions (extraction pressure and
temperature, pre-and post-expansion temperature, mass flow rate and n
ozzle design) were varied systematically to analyze their impact on th
e crystal habit and size of the precipitated material. Except for phen
anthrene, the crystals obtained with the frit nozzle were smaller than
those precipitated with the capillary nozzle, as can be explained fro
m expansion paths and solubility diagrams. (C) 1997 Elsevier Science B
.V.