Microwave-Assisted Catalytic Heating for Enhanced Clean Hydrogen Generation from Methane Cracking in Shale Rocks

Steam methane reforming (SMR) technology generates about 95% hydrogen (H₂) in the United States using natural gas as a main feedstock. While hydrogen is clean, the process of hydrogen generation via SMR is not, as it emits about 10 times more carbon dioxide (CO₂) than hydrogen. The CO₂ has to be captured and sequestrated in reservoirs or aquifer systems, which is costly. A revolutionary approach is to generate and extract hydrogen directly from petroleum reservoirs by taking advantage of the abundant unrecovered hydrocarbons in reservoirs. This approach does not involve natural gas production, transportation, or refinery. Meanwhile, the CO₂, if generated, will be sequestrated simultaneously in reservoirs without being produced to surface. This approach is therefore potentially low cost and environmentally friendly. In this paper, we propose to use microwave-assisted catalytic heating to enhance methane conversion to hydrogen within shale gas reservoirs. To validate this concept, we conducted a series of experiments to crack methane streams flowing through shale rock samples and powders in a microwave reactor. With silicon carbide (SiC) as the microwave receptor, the temperature of shale samples can quickly reach to above 700 °. The methane conversion efficiency is up to 40.5% and 100% in the presence of Fe and Fe₃O₄ catalysts at the measured temperature of 500° and 600 °, respectively. Interestingly, the presence of shale is favorable for methane cracking at a relatively lower temperature compared to the case with the same weight percentage of SiO₂ in heated samples. The thermal decomposition of carbonate in shale rocks also benefits the improvement of permeability of shale. The influences of different shale weight ratios and methane flow rates are also investigated.