Methane dry reforming reaction on Ru(0 0 1) surfaces

Abstract Methane dry reforming on a Ru(0 0 1) single-crystal surface was investigated using a high-pressure reactor directly combined with an ultra-high-vacuum system for temperatures between 700 and 800 K and under initial CH 4 and CO 2 pressures in a range of 50–240 Pa. In the CH 4 –CO 2 reaction, dry reforming (DRM) proceeds accompanied by a quasi-equilibrated reverse water gas shift reaction. The rate of the DRM reaction exhibits first-order dependence on CH 4 pressure and is almost independent of CO 2 pressure, giving an apparent activation energy of 110 kJ/mol. These kinetic parameters are in good agreement with those reported on Ru-supported oxide catalysts. From the exchange reaction between 13 CO 2 and CO, a very low activation energy of 7.2 kJ/mol and a TOF around 18 are obtained for CO 2 dissociation on the bare Ru(0 0 1) surface. In the CH 4 – 13 CO 2 reaction, the exchange reaction between 13 CO 2 and CO is also quasi-equilibrated. These results are consistent with ultraviolet photoelectron spectroscopy and low-energy electron diffraction measurements for postreaction Ru surfaces, which show that carbon species derived from the decomposition of CH 4 are substantially removed as CO by oxygen atoms supplied from the dissociation of CO 2 . Taking the respective reaction orders of CH 4 and CO 2 into consideration, it is concluded that the rate-limiting step for the DRM reaction is the breaking of the C H bond in CH 4 .

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