Effect of Mixing and Other Operating Parameters in Sol−Gel Processes

Abstract

In this work the effect of mixing on a sol-gel process is quantitatively investigated. Titanium dioxide synthesis from titanium tetra-isopropoxide is used as a test reaction. Solutions of titanium alkoxide in isopropyl alcohol and water in isopropyl alcohol are mixed in a special mixing device (i.e., vortex reactor) at different mixing rates, and the effect of mixing is quantified and compared with the effect of the other relevant operating parameters, namely the water to alkoxide, acid to alkoxide ratios, and alkoxide initial concentration. Dynamic light scattering, specific surface area measurement through nitrogen adsorption, X-ray diffraction, and field emission scanning electron microscopy are employed to determine particle size distribution, morphology, and crystallite size of the different particulate products (i.e., sols, gels, powders) obtained before and after thermal treatments under different synthesis conditions. A factorial design is used to plan the experimental campaign and results show that the role of mixing cannot be neglected. Moreover results show that mixing can be actively used to control the final product characteristics and must be taken into account when a process is transferred from the laboratory to the industrial scale. Eventually a scale-up criterion based on our previous work will be discussed.

Preparation of Poly(MePEGCA-co-HDCA) Nanoparticles with Confined Impinging Jets Reactor: Experimental and Modeling Study

“…Our previous studies show that this quantity is related to the mean particle size of the obtained particles; in fact, the faster mixing is (namely, the smaller the global mixing time is) the smaller the obtained particles are. 16,17,19,21 The global mixing time is here calculated by using the commercial CFD code FLUENT 6.3. The computational grid for the CIJR was created with GAMBIT, and only half of the real geometry was considered, under the hypothesis of symmetry.…”

“…In other works, mixing was quantified in the very same devices by using barium sulfate precipitation and mathematical modeling, resulting in characteristic mixing times of the order of magnitude of milliseconds. [17][18][19] Other innovative and highly efficient mixers such as tee mixers, 20 standard vortex reactors, 21 and multi-inlet vortex reactors [22][23][24] have also been proposed and employed for a variety of applications. 25,26 The main advantage of these mixers/reactors stands in their ability to guarantee reproducible mixing conditions, and therefore as a consequence, reproducible product characteristics, when compared with classical laboratory-scale preparation methods (i.e., flask equipped with magnetic stirrers).…”

SYNTHESIS OF CHITOSAN-FILM COMPOSITE TiO2 USING SORBITOL AS PLASTICIZER

“…Menurut Marchisio et al (2008) Pembentukan komposit film dalam penelitian ini dapat dimungkinkan karena adanya gaya kohesi atau proses saling sambung menyambung antar molekul polimer kitosan sebagai backbone komposit membentuk rangkaian lapisan polimer kitosan. Gaya kohesi ini menjadikan interaksi antar polimer kitosan menjadi semakin kuat.…”

Precipitation of Nanosized and Nanostructured Powders: Process Intensification and Scale‐Out Using a Segmented Flow Tubular Reactor (SFTR)

“…The powder characteristics obtained with a simple batch volume or with the SFTR is compared and the robustness of the SFTR is investigated. The effect of the micromixer used in the process on the material properties is also studied, as it is well-known that the mixing conditions can determine the resulting product properties in precipitation systems, especially influencing the particle size [26][27][28]. A key factor for nanopowder production is its colloidal stability and capacity to be dried and redispersed without loss of powder quality.…”