Metals that are active catalysts for methane (Ni, Pt, Pd), when dissolved in inactive low-melting temperature metals (In, Ga, Sn, Pb), produce stable molten metal alloy catalysts for pyrolysis of methane into hydrogen and carbon. All solid catalysts previously used for this reaction have been deactivated by carbon deposition. In the molten alloy system, the insoluble carbon floats to the surface where it can be skimmed off. A 27% Ni-73% Bi alloy achieved 95% methane conversion at 1065°C in a 1.1-meter bubble column and produced pure hydrogen without CO or other by-products. Calculations show that the active metals in the molten alloys are atomically dispersed and negatively charged. There is a correlation between the amount of charge on the atoms and their catalytic activity.

Hydrogen bromide (HBr) oxidation to molecular bromine (Br 2 ) is demonstrated in a chemical looping process using a molten bromide salt. The two-step process is operated at 500 °C and first contacts oxygen with molten KBr-LiBr-NiBr 2 to form Br 2 gas and a suspension of nickel oxide (NiO) particles in one reactor. The oxide suspension is then contacted with HBr to regenerate the bromide salt and produce steam. Sixty-eight metal oxides/bromides were considered. The cyclic interconversion between oxide and bromide, by alternating exposure to HBr and oxygen, at a single temperature was only possible with nickel. In contrast to solidbased chemical looping systems, the liquid bromide salt (NiBr 2 dissolved in KBr-LiBr eutectic) was found to be cycleable without attrition or deactivation. Further, when mixtures of olefins and hydrogen bromide were reacted with the oxide suspension, selective oxidation of HBr was observed without hydrocarbon oxidation. High selectivity for HBr oxidation is due to the solubility of HBr in the molten salt, which allows contact with NiO, whereas, the insoluble hydrocarbons do not contact the reactive oxide. A process model that makes use of reactive separation of HBr from hydrocarbons and process intensification using molten salt-based chemical looping is presented as a potentially lower cost alternative to a process model using conventional separations in bromine-based methane conversion. The total heat exchanged in a corrosive environment in the molten salt based process is 205 MW, and the heat exchanged in a corrosive environment in the conventional process is 581 MW.

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The partial oxidation of methane to carbon and steam was investigated in molten salts for a process to produce CO 2 -free electrical power and solid carbon. Lithium iodide and lithium bromide catalysts were used in a bubble column where insoluble carbon accumulates on the melt surface and could be continuously removed. The salt acts as a heat transfer medium and reacts with oxygen to produce halogens and consume hydrogen halides in a chemical looping cycle. The halogens react with methane in gas-phase bubbles and form hydrogen halides and carbon. Hydrogen halides are then neutralized by an oxide and form steam and a halide salt. The halide salt reacts with oxygen, forming an oxide and closing both the halogen and the salt chemical looping cycles in a single vessel. Selectivities to carbon of 90% were measured for 56% methane conversion in a 12 cm bubble column reactor. The carbon was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. Iodide and bromide salts were investigated along with the behavior of iodine, bromine, methyl iodide, and methyl bromide intermediates.