Experimental investigations and simulation of antisolvent crystallization processes in supercritical fluids

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Cocrystallization induced by compressed CO2 as antisolvent: Simulation of a batch process for the estimation of nucleation and growth parameters

A mathematical model describing the GAS antisolvent process applied to cocrystal formation has been developed with the aim of estimating nucleation and growth parameters that are critical issues in crystallization in general. The estimates are obtained by fitting the particle sizes distribution predicted by the model to experimental data. The investigated system was naproxen + nicotinamide that assembled as cocrystals when recrystallized by adding CO2 to acetone solution. The concentration of naproxen + nicotinamide in the liquid phase was calculated from the experimental data of the quaternary system. Particle formation was described by primary and secondary nucleations and a growth rate driven by diffusion. The population balance equation was solved by the standard method of moments assuming a log-normal distribution. Particles of NPX2:NCTA cocrystals of 40-80 mu m mean size were experimentally produced and the experimental size distributions were well fitted by the proposed cocrystallization model. (C) 2014 Elsevier B.V. All rights reserved

Investigation of the precipitation of Na2SO4 in supercritical water

SuperCritical Water Oxidation process (SCWO) is a promising technology for treating toxic and/or complex chemical wastes with very good efficiency. Above its critical point (374 °C, 22.1 MPa), water exhibits particular properties and organic compounds can be easily dissolved and degraded with the addition of oxidizing agents. But these interesting properties imply a main drawback regarding inorganic compounds. Highly soluble at ambient temperature in water, these inorganics (such as salts) are no longer soluble in supercritical water and precipitate into solids, creating plugs in SCWO processes. Although this precipitation phenomenon is well known as a limiting factor for SCWO process, it is still not well understood. This work intends to investigate the precipitation phenomenon with a new methodology. A common salt, disodium sulfate (Na2SO4), is taken as a reference for the study. Na2SO4 solubility in sub- and supercritical water is determined on a wide temperature range using a continuous set-up. Crystallite sizes formed after precipitation are measured with in situ synchrotron wide angle X-ray scattering (WAXS). Combining these experimental results, a numerical modeling of the precipitation in supercritical conditions is performed by taking into account all the implied physical phenomena: thermodynamic, hydrodynamic and nucleation & growth

Highly Reactive Pd NCs by Versatile Continuous Supercritical Fluids Synthesis for the Preparation of Metal–Nonmetal Pd-Based NCs

International audienceNanostructured palladium is of huge importance for a large range of applications, especially in the field of catalysis. Therefore, the development of synthetic procedures to gain control over palladium physicochemical properties is of paramount importance. Lately, the attention has been focused on combining Pd with other elements, even metal or nonmetal, because of enhanced or new properties arising from synergetic effects, diversity in composition, structures, along with others. Of interest for catalysis, nanoscaled materials made of Pd and a nonmetal part such as C, P, B, or N are envisioned. In the present work, we present the possibility of nonmetal (C or H) atom incorporation into the Pd lattice under ambient conditions as the subsequent step to nucleation and growth of highly reactive crude palladium nanocrystals in supercritical fluids. The as-modified Pd NCs present different physicochemical properties, allowing us to envision the possibilities of other materials preparation, for example, phosphides or borides, by this chemical colloidal approach

Review of Reduced Order Models for Heat and Moisture Transfer in Building Physics with Emphasis in PGD Approaches

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