Dry Reforming of Methane in Molten Metal Alloys

Dry reforming of methane (DRM) has had limited practical application due to the relatively low H₂:CO product ratio and challenges in catalyst coking. Syngas with a H₂:CO ratio of 2:1 is required for oxo-alcohol and hydrocarbon production; however, the DRM processes explored thus far produce H₂:CO ratios of at most 1:1. The low ratio is a result of the trade-off between the thermodynamics of the reforming reaction and coking kinetics. By combining dry reforming of methane with methane pyrolysis to produce H₂-rich syngas and solid carbon in a single catalytic molten metal-based reactor, high H₂:CO ratios can be obtained and catalyst deactivation from coke is eliminated. In molten metal bubble column reactors, the low-density solid carbon is continually removed from the high-density melt and methane is activated within the rising bubble with a continuously-renewed metal surface. DRM is demonstrated using a molten alloy of 65 mole % nickel – 35 mole % indium with 92% CO₂ conversion and 55% CH₄ conversion to produce a H₂:CO ratio of 1.2:1. The system produces a nanocrystalline graphitic carbon product as measured by Raman spectroscopy. The variability of the syngas H₂:CO ratio with changes in the feed ratios of methane to carbon dioxide, the reaction temperature, and the residence time is demonstrated.