CO₂ Hydrogenation to Methanol over a Highly Active Cu–Ni/CeO₂–Nanotube Catalyst

A series of Cu–Ni/CeO 2 -nanotube catalysts is prepared by an impregnation method for CO 2 hydrogenation to CH 3 OH. Regular CeO 2 nanotubes are perfectly formed with a tube diameter of about 30–50 nm and Cu–Ni alloy is well dispersed on CeO 2 nanotube without nanotube morphology change. There is a synergistic effect between Ni and Cu, promoting the bimetallic Cu–Ni dispersion, reducibility, CO adsorption and hydrogenation. Additionally, a strong interaction is observed between Cu–Ni alloy and CeO 2, and it contributes to partial reduction of Ce 4+ to Ce 3+ and formation of oxygen vacancies which adsorb and activate CO 2 . It is shown that both CO 2 conversion and CH 3 OH space-time yield increase at first, reach their maximum values at a Ni/(Cu+Ni) ratio of 2/3, and then decrease with increasing the Ni/(Cu+Ni) ratio. The CeO 2 -nanotube supported CuNi 2 catalyst gives CO 2 conversion of 17.8% and CH 3 OH space-time yield of 18.1 mmol/(g cat ·h) after preliminary optimization. Furthermore, it exhibits an excellent catalytic performance within a wide range of space velocity.