Continuous synthesis of nickel nanopowders: Characterization, process optimization, and catalytic properties

The preparation of nanoparticles with tailored properties and in quantities in the order of 10-100 g prepared with laboratory-scale equipment is a target of great interest. In this study, Ni nanoparticles with different sizes, surface morphologies, magnetic, and catalytic properties were obtained from NiCl2, N2H4, NaOH, and ethylene glycol as solvent by tuning the synthesis parameters. Preliminary syntheses were done in batch reactors and then the continuous synthesis carried out in the Segmented Flow Tubular Reactor (SFTR). For the first time a SFTR system was applied to a non-aqueous system. By combining SEM, HRTEM, XRD, TGA, XPS, FTIR, specific surface area, SQUID, and catalytic tests, the complete structural, morphological, and functional characterization of the produced nanoparticles were performed. The continuous production of 2.1 g h(-1) of Ni nanoparticles was carried out up to 6 h without product properties deterioration. The results allow estimating a production > 300 g d(-1) in an ad-hoc low-cost single-tube SFTR system. Catalytic tests of CO methanation showed good activity at 769 K with stable methane yield of 83%. The results presented in this study demonstrate that reliable and reproducible synthesis of relatively high amounts of metal nanoparticles with lab-scale equipment can be achieved. This approach opens new opportunities for reliable and controlled preparation of advanced materials in quantities suitable for a full functional characterization. (C) 2014 Elsevier B.V. All rights reserved.