Enhanced Hydrogen Generation from Olivine Sand

Abstract An experimental setup was created to study serpentinization of an olivine sand sample and study hydrogen production. Inspired by the so-called "white" hydrogen sources, enhanced serpentinization of olivine represents an attractive opportunity to produce hydrogen from geological resources. Literature offers examples of experimental conditions that achieve hydrogen production at laboratory scale with different degrees of success. We made a preliminary selection of experimental parameters and assembled a setup capable of replicating conditions suitable for hydrogen production from enhanced olivine serpentinization. Commercially available olivine sand was selected with a grain size range of 250 to 355 μm for the experiment. The sample was subjected to 18 days of high pH brine exposure via continuous inflow, while inside a reactor heated by a furnace. The operating temperature range inside the reactor was between 80 and 245°C. The produced gas phase was separated, periodically collected, and analyzed via gas chromatography calibrated for hydrogen. Analysis of the produced gas (uncorrected for the presence of air) showed hydrogen concentrations of 9 and 13% by mole. The precursor olivine sand was characterized in pre- and post-reaction states using scanning electron microscopy and analytical techniques (x-ray diffraction and x-ray fluorescence). A significant amount (14 wt% of the reacted sample) of serpentine precipitate was observed, coating the grains. The analysis suggests that the serpentinization reaction was maintained by the large grain size and the development of accessible porosity between the grains and grain-coating serpentine precipitates. Minor amounts of carbonate, magnetite, and variable composition (Ca-Fe-Mg-Ti) silicate precipitates were also observed. These preliminary results suggest that it is possible to enhance, at laboratory scale, serpentinization of olivine and generate hydrogen with significant H2 compositional yields. Our findings are supported by produced gas analysis and evidence collected on the reacted sample.