Synthesis, characterization, and evaluation of nickel catalysts on nanocrystalline CeO2 promoted by K and Mn for medium-temperature shift reaction and hydrogen purification

Abstract

The performance of synthesized nickel catalysts was evaluated in medium-temperature shift reaction (MTS, 320–360 °C). The catalysts were characterized by X-ray diffraction, scanning electron microscopy, temperature-programmed reduction, and CO2 temperature-programmed desorption. Reactor test of 10 wt%Ni/CeO2 showed high CO conversion (91%), but with high CH4 selectivity (90%). Therefore, 10Ni–xK/CeO2 (x = 4, 6, 8, and 10 wt%) catalysts were synthesized via impregnation method to suppress the methanation reaction. Simultaneous impregnation of Ni and potassium led to better performance than sequential impregnation. Potassium, by increasing the hydroxyl group, led to decreased CH4 selectivity from 90 to 3% at 360 °C, and the 10Ni–6K/CeO2 catalyst exhibited the best activity, selectivity, and stability in severe conditions. Additionally, gas hourly space velocity of 12,000 h−1 and steam-to-carbon ratio of 3 were selected as optimal operating conditions. To determine the effect of Mn addition to the support, reactor test of 10Ni–6K/Ce0.8Mn0.2O2 was also carried out, showing that the catalytic activity was less than for the ceria-supported sample at low temperatures, but due to the appropriate interaction of Mn with Ni, preventing catalyst sintering, the stability of the catalyst at high temperatures was improved and the Mn-containing catalyst showed higher CO conversion.