Rapid Crystallization of Silicalite Nanocrystals in a Capillary Microreactor

Abstract

Silicalite nanocrystals were synthesized in a pressurized capillary microreactor at 150°C within 11 min with synthesis solutions aged at 80 or 100°C for 1-6 h. The effects of aging of the synthesis solution and the reaction pressure were examined. The resulting products were characterized by XRD, DLS, TEM, FT-IR and TG-DSC. Aging of the synthesis solution played an important role in shortening the crystallization time of the silicalites. The synthesis pressure should be higher than the saturation vapor pressure of water at 150°C (∼0.5 MPa) and silicalite nanocrystals with crystallinities of 70 % and 100 % could be produced from the synthesis solution aged at 100°C for 2 h with residence times of 11 min at 0.7 MPa and 1 MPa, respectively. The mean particle sizes of these two samples were 102.2 nm and 166.4 nm, respectively. Thus, the crystallization time of the silicalite nanocrystals is shown to be significantly reduced in the capillary microreactor compared to a traditional batch system.

Porous Nanosized Particles: Preparation, Properties, and Applications

“…The smallest crystals (60–260 nm) with mean particle size of 140 nm were obtained after adding sodium silicate solution. Pan et al have also synthesized silicailite-1 nanocrystals using a capillary microreactor with an inner diameter of 1 mm . The best result was achieved at 150 °C for 11 min, in which MFI-type material was obtained with 70% crystallinity.…”

Synthesis of micro and nanostructures in microfluidic systems

“…140 More recently, silicalite nanoparticles (50-100 nm) have been synthesized in solvothermal conditions (150 1C, 1 MPa) in a stainless steel capillary by the reaction of TEOS with tetrapropyl ammonium hydrate (TPAOH) in water. 136 The second family of methods takes advantages of the size and shape of micro droplets that can be generated inside microfluidic devices to form microparticles, similarly to what is done for organic materials processing (synthesis of polymersomes or polymer-based hollow spheres, cf. sections III-1 and III-2).…”

Technische Chemie 2009

“…Die Mikroreaktionstechnik ist auch nützlich für die Herstellung moderner Funktionsmaterialien: Nanokristalle des Zeoliths Silicalit‐1 wurden in einer Kapillare mit einem Innendurchmesser von 1 mm bei einem Druck von etwa 1 MPa mit einer Verweilzeit von elf Minuten synthetisiert, nachdem die Syntheselösung zuvor zwei Stunden bei 100 °C gealtert worden war 33. Mit dieser Methode sollte die kommerzielle Herstellung von nanopartikulären Zeolithen deutlich kostengünstiger werden.…”