Low-Temperature and Highly Active Nickel Catalyst Based on Hydrotalcite Mg-Al for CO2 Methanation

Ni/hydrotalcite catalysts are synthesized by the coprecipitation method. Synthesis times are decreased and activation is performed with just a reductive calcination under mild conditions without the usual air-calcination step. Compared with the other reported catalysts made of Ni/hydrotalcite, in terms of space-time yield (STY), the best synthesized catalyst is the most efficient one (STY = 137.19 mol CH4 h(-1) L-1 at 300 degrees C) and this high efficiency is kept at low temperature (STY = 132.67 mol CH4 h(-1) L-1 at 250 degrees C). Results show that the amount of reduced Ni, created upon the mild reduction, increases with the Ni loading and the Ni-0 amount correlates with the catalytic activity. CO2 adsorption capacity remarkably increases with the Ni content but this trend does not correlate with the conversion. Surface areas, neither pore sizes, do not show a correlation with catalytic results. The most important result is the very high activity observed at temperatures below 300 degrees C. Characterization results indicate that the outstanding low-temperature performance must be due to the presence of high amounts of small and reduced Ni crystallites with low interaction with the support. Developed catalysts are stable for 28 h at 300 degrees C.