Synthesis gas production by dry reforming of methane over Neodymium-modified hydrotalcite-derived nickel catalysts

Abstract

Neodymium-modified hydrotalcite-derived nickel catalysts (NixNdMgAlO) by adjusting the Nd content (x) at a range of 2.5–10% were synthesized via co-precipitation method. The catalytic properties of these catalysts were evaluated in the reaction of dry reforming of methane (DRM) at 750 °C. The initial CH4 conversion decreased with the order of Ni7.5NdMgAlO > Ni5NdMgAlO > NiMgAlO > Ni2.5NdMgAlO > Ni10NdMgAlO. The Ni7.5NdMgAlO catalyst with a compromised proportion of Nd at 7.5% had the smallest nickel crystallite size (8.1 nm), highest metal dispersion (11.8%), the highest exposed active sites on the surface (6.3 m2/g) as well as the relatively intimate interaction between small Ni2+ species and the support. Moreover, Ni7.5NdMgAlO with the largest amount of CO2 desorption (736.6 μmol/g-cat) effectively oxidized the coke on the catalyst surface, and manifested the excellent coke resistance (2.4%) in addition to the highest CH4 and CO2 conversion in the DRM reaction. In addition, the optimal addition (7.5%) of Nd to NiMgAlO resulted in a lowering of the activation energy of CO2 by 15%. At excessive Nd content, Ni10NdMgAlO exhibited larger nickel crystallite size (10.5 nm) and was subject to severe accumulation of encapsulating carbon leading to pronounced deactivation.