Effect of catalyst morphology on the performance of submerged nanocatalysis/membrane filtration system

Coupling systems of nanocatalysis and membrane filtration (nanocatalysis/MF) are features of convenience for the in situ separation of nanocatalysts from the reaction mixture. In this work, a submerged nanocatalysis/MF system with a tubular ceramic membrane as the separation unit was developed for the liquid-phase hydrogenation of p-nitrophenol to p-aminophenol over nickel nanoparticles with various particle morphologies obtained by hydrogen annealing at different temperatures. We extensively characterized the nickel nanoparticles using X-ray diffractometry (XRD), nitrogen adsorption, transmission electron microscopy (TEM), and highresolution transmission electron microscopy (HRTEM), and we determined that the annealing temperature significantly influenced the particle size, specific surface area, and crystalline morphology of the nickel nanoparticles. We then evaluated the catalytic performance and separation efficiency of the submerged nanocatalysis/MF system. The nickel nanoparticles annealed at different temperature showed remarkably different catalytic activity, because of their specific structural properties. There was an unexpected nonlinear relationship between the nickel particle size and the flux, which was due to the changed nature of the cake layer formed on the membrane surface and a pore blocking effect. The results from both aspects of catalysis and separation performance indicated that the nickel nanoparticles annealed at 100 °C displayed a best balanced catalytic performance and separation efficiency for the submerged nanocatalysis/MF system.