Continuous synthesis of palladium nanorods in oxidative segmented flow

Abstract

in Wiley Online Library (wileyonlinelibrary.com)Laminar and segmented flow methods are presented for producing Pd rod-shaped nanostructures from Na 2 PdCl 4 in mixtures of water, ethylene glycol, polyvinyl pyrrolidone, and KBr. Synthesis in laminar flow produced an evolution from Pd nanoparticles to short nanorods with residence time. Use of air as the segmentation gas tuned the oxidative environment promoting anisotropic growth of Pd. Moreover, the elevated temperatures (1608C and 1908C) and pressure (0.8 MPa) reduced the synthesis time from hours for most batch systems to 2 min. The ratio of polyol and Pd precursor metal flow streams controlled the anisotropic growth, obtaining nanorods with a diameter approximately 4 nm and an aspect ratio up to 6. Nanorods were single crystal with the {100} lattice spacing of fcc structure, and without any dislocation, stacking fault, or twin defects. The resulting Pd nanorods had high activity at moderate temperature (40 C) and pressure (0.2 MPa) in the catalytic hydrogenation of styrene.

Shape-controlled continuous synthesis of metal nanostructures

“…Micro and meso scale flow reactors have been used to improve particle size distribution of nanomaterials 17,18 and to effect shape control. [10][11][12][19][20][21] Herein, we report a MFR approach to synthesize anisotropic palladium and platinum nanostructures under kinetic control, in order to fine tune the size and shape of nanocrystals, as part of a continuous flow system. Gasliquid segmented flow in a silicon-pyrex MFR is used as a versatile tool that not only realises better control of the nanostructures size distribution, but also achieves excellent shape control.…”

Manipulation and Control of Structure and Size of Inorganic Nanomaterials in Microchemical Systems

“…Correspondingly, novel quantum dots, small-sized nanocubes, nanosheets, and nanorods have been successfully prepared in microchemical systems. Sebastian et al synthesized nanocubes, nanosheets, and nanorods in a silicon-Pyrex microreactor containing a cooled mixing zone and a heated reaction zone, which could withstand higher temperature (the maximum was approximately 350°C) and pressure (nearly 1 MPa) [28,65]. Gas was introduced to form the segmented flow, as indicated in Fig.…”

Understanding the Influence of Rheological Properties of Shear‐Thinning Liquids on Segmented Flow in Microchannel using CLSVOF Based CFD Model

“…They pointed out that due to differences in the surface energies of the phases involved, mass transfer rate and mixing characteristics were improved in the T‐junction microchannel. A kinetic study of palladium nano‐rod synthesis in a segmented flow regime suggested that residence time distributions were narrower, which reduced the raw material costs, and mass transfer rates were found to be enhanced, thus promoting anisotropic growth of the nanocrystals . Wang et al studied segmented flow for a range of reaction schemes such as oxidation, etherification of benzyl bromide and phenoxide, and C‐C and C‐N coupling reactions.…”