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.

In 2 O 3 has recently emerged as a promising catalyst for methanol synthesis from CO 2 . In this work, we present the promotional effect of Pd on this catalyst and investigate structure−performance relationships using in situ X-ray spectroscopy, ex situ characterization, and microkinetic modeling. Catalysts were synthesized with varying In:Pd ratios (1:0, 2:1, 1:1, 1:2, 0:1) and tested for methanol synthesis from CO 2 /H 2 at 40 bar and 300 °C. In:Pd(2:1)/SiO 2 shows the highest activity (5.1 μmol MeOH/g InPd s) and selectivity toward methanol (61%). While all bimetallic catalysts had enhanced catalytic performance, characterization reveals methanol synthesis was maximized when the catalyst contained both In−Pd intermetallic compounds and an indium oxide phase. Experimental results and density functional theory suggest the active phase arises from a synergy between the indium oxide phase and a bimetallic In−Pd particle with a surface enrichment of indium. We show that the promotion observed in the In−Pd system is extendable to non precious metal containing binary systems, in particular In−Ni, which displayed similar composition−activity trends to the In−Pd system. Both palladium and nickel were found to form bimetallic catalysts with enhanced methanol activity and selectivity relative to that of indium oxide.

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Ru 0.05 Ce 0.95 O x is an active catalyst for methanation of CO 2 with H 2 . Under reaction conditions one expects that oxygen vacancies are present on the oxide catalyst surface and that their steady-state concentration depends upon the relative ratio of the oxidant (CO 2 ) to the reductant (H 2 ). We show that the activity of the catalyst is sensitive to the degree of surface reduction: a surface that is too reduced or too oxidized loses activity. Exposing the oxidized surface to CO 2 and then to H 2 produces no methane, while on a reduced surface methane is produced by exposure to CO 2 followed by H 2 . If the reaction is carried out at the steady state, purged, and then exposed to only hydrogen, methane is produced. Methane is formed through the reaction of hydrogen with surface species, whose infrared spectrum is associated with a variety of surface carbonates, and not through CO or a formate intermediate.