A stock solution was prepared by suspending TiO2 nanoparticles (Titanium oxide, anatase, less than25 nm, 637253-50G, Sigma-Aldrich) in a solution of 4-(trifluoromethyl)benzyl alcohol (SC034058, Fluorochem Limited) in acetonitrile (MeCN, HPLC-R, Biosolve Chimie SARL). For the exact concentrations, we refer to the corresponding experiments (see section 3.2). The TiO2 particles were smaller than 25 nm, which is, however, the initial size of these particles. The actual powder consists of aggregates and agglomerations of these primary particles. The actual particle size distribution of TiO2 particles in the solution was measured by a laser particle sizer (Analysette 22 microtec plus, Fritsch). As shown in Fig. S1 (See Supporting Information), the measured size distribution shows a wide distribution with three agglomeration peaks, falling in the range of 0.1–1, 1–10 and 10–40 µm respectively. The average size is 3.8 µm. Next, the stock solution was taken up in a 60 mL plastic syringe, in which a magnetic stir bar was placed. The syringe was mounted on a syringe pump (Fusion 720 Fusion 200, Chemyx Inc.).
Magnetic stirring was applied by putting a compact magnetic stirrer (Topolino, IKA) beneath the front part of the syringe (as shown in Fig. 2). In this way a uniform suspension was maintained inside the syringe and could reliably be introduced into the ultrasonic milli-reactor. To prevent particles settling down at the inlet microfluidic connections, these connections were kept as short as possible (ca. 5 cm) and were placed in a downward trajectory before reaching the reactor. The gas phase was fed from an oxygen gas line and dosed into the liquid stream using a mass flow controller (F-200CV-002-AAD-22-K, Bronkhorst Nederland BV). The gas and liquid phase were combined in a stainless-steel tee junction (VALCO) to establish a gas–liquid Taylor flow regime and were subsequently delivered to the photochemical ultrasonic milli-reactor. Therefore, a gas–liquid-solid three phases flow was formed in the millichannel, which was exposed to the UV light. The physical properties of the three phases are listed in Table 1.
Date Published: June 2021
Read the full article here: A mesoscale ultrasonic milli-reactor enables gas-liquid-solid photocatalytic reactions in flow
Authors: Zhengya Dong Zhengya Dong, Stefan D. A. Zondag Matthias, Schmid Zhenghui Wen (University of Amsterdam), Timothy Noel Eindhoven (University of Technology).