Simultaneous production of hydrogen and nanosized zinc oxide by hydrolysis of zinc vapor

Abstract

Hydrogen and zinc oxide (ZnO) nanoparticles were simultaneously produced by the steam-hydrolysis of zinc vapor. This process was experimentally demonstrated using a tubular flow reactor. Zinc vapor was evaporated at temperature below its boiling point and carried to the reaction zone by an inert carrier gas. Steam was generated in separated vessel and fed co-currently with the zinc vapor into the reaction zone. Solid products collected by filter downstream were characterized by X-ray diffraction and scanning electron microscopy (SEM) while the gas was periodically sampled and analyzed by gas chromatography (GC). In this research influence of process parameters including zinc evaporation temperature, reaction temperature, flow rate of zinc vapor, and resident time were investigated. The experimental results show that low zinc evaporation temperature resulted in decreased yield of H2. By increasing the reaction temperature from 500oC to 900oC, the yield of H2 increased from 24.4% to 59.71%, while the fraction of ZnO within the collected products increased from 16.9% to 30.71 %. Higher carrier gas flow rate resulted in lower achieved yield of H2 and smaller particle size. The highest yield of H2 production achieved was 72.59% with respect to theoretical value.