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

Abstract

The successful scale-out and process intensification using a segmented flow tubular reactor (SFTR) for ultrafine CaCO 3 , BaTiO 3 , and nanosized ZnO from optimized minibatch (20 mL) conditions is presented. The capacity of the SFTR in process intensification was demonstrated by producing ∼ 5 kg batches of BaTiO 3 powders with excellent batch-to-batch reproducibility. The SFTR scale-out or numbering-up capacity was demonstrated for a nanostructured CaCO 3 in 500 g batches by scaling-out from one to six segmented flow tubular reactors run in parallel (scale-out/-up ratio of 5000 compared to lab batch experiments). The SFTR was then used to demonstrate its potential for nanosized ZnO powders producing 50 g lots of these nanopowders in a continuous process, a scale-out/-up ratio of 250 compared to lab batch experiments without any loss of powder quality. The SFTR allows a precise control of precipitation conditions, leading to an excellent reproducibility in powder characteristics, and shows great promise as a simple production process of powders and advanced nanomaterials with highly controlled properties.

Synthesis and Sintering of ZnO Nanopowders

“…The details of the synthesis have been given in a previous publication [42], thus only a brief description is given here (Figure 1). The SFTR has three distinct zones: a micromixer, a segmenter, and a tubular reactor placed in a thermostatic bath, here set at 90 • C. The reactants in the solution pass through the micromixer where initial supersaturation is rapidly created with a mixing time of around 10 milliseconds [41]. The mixed reactants are then segmented by an immiscible solvent, here dodecane.…”

“…This process has proven its versatility and its robustness through the preparation of several different products (CaCO 3 [35], BaTiO 3 [36], and various oxalates [37,38]) ensuring a high powder quality (chemical and phase composition, particle size, and shape) and reproducibility over time. The transfer of the laboratory conditions to an industrial scale of production can be easily achieved by multiplying the number of individual tubular reactors running in parallel-that is to say, to "scale-out" rather than "scale-up" [39][40][41].…”

Synthesis and Sintering of ZnO Nanopowders

“…The SFTR has three distinct zones: a micromixer, a segmenter, and a tubular reactor placed in a thermostatic bath here set at 90 °C. The reactants in solution pass through the micromixer where initial supersaturation is rapidly created with a mixing time of around 10 milliseconds [20]. The mixed reactants are then segmented by an immiscible solvent, here dodecane.…”

“…The NaOH solution at 0.11 M was made by diluting a titrated solution NaOH 1 M in ultra pure water. Poly(acrylic acid) (PAA Mw 2000) at 0.05 wt.% was used as a dispersant in the NaOH reaction solution to decrease the degree of agglomeration of the synthesized nanopowders [20], [33]. The collected powder was washed with ultrapure water 4 times, and then filtered and dried during 24 hours at 70 °C.…”

“…This process has proven its versatility and its robustness through the preparation of several different products (CaCO3 [14], BaTiO3 [15], and various oxalates [16], [17]) ensuring a high powder quality (chemical and phase composition, particle size, and shape) and reproducibility over time. The transfer of the laboratory conditions to an industrial scale of production can easily be achieved by multiplying the number of individual tubular reactors running in parallel -that is to say to "scale-out" rather than "scale-up" [18][19] [20].…”