Synergy effect of MgO and ZnO in a Ni/Mg–Zn–Al catalyst during ethanol steam reforming for H2-rich gas production

Nickel based mixed oxide catalysts derived from Ni–Mg–Zn–Al hydrotalcite-like precursors are prepared and evaluated for H2-rich gas production via ethanol steam reforming. It has been found that the catalyst properties (e.g. BET surface area, Ni dispersion and reducibility) and catalytic performance depend on the Mg:Zn molar ratio. MgO and ZnO have a synergetic effect. At 700 °C, the quaternary catalyst with a Mg:Zn ratio of 4 exhibits the highest H2 yield and best stability, viz. no apparent variation of the product distribution over 100 h operation, whereas the ternary catalyst without Mg suffers severe coke accumulation after 7 h on-stream. Two types of carbon (filamentous and amorphous) are found deposited on the catalyst surface. The carbon deposited is dominated by filamentous carbon, which is likely originated from the decomposition of methane, and does not cause immediate deactivation.

Long-term stability test over a catalyst with Mg:Zn ratio = 4 at 700 °C.Figure optionsDownload high-quality image (94 K)Download as PowerPoint slideHighlights
► Ni/Mg–Zn–Al catalysts derived from hydrotalcite-like precursors are active in ethanol steam reforming.
► The quaternary catalyst with a Mg:Zn ratio of 4 is hard to reduce, has a high Ni dispersion and good catalytic performance.
► TPO and HR-TEM verify that two types of carbon deposited on the catalyst surface.