Effect of Ce modification on the performance of CuLDH catalyst for CO2 hydrogenation to methanol

Abstract

A series of Ce modified CuLDH-Ce_x catalysts were synthesized by adding different amounts of Ce to CuMgAl hydrotalcite (CuLDH) catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), etc. The results showed that the addition of Ce changed the hydrotalcite structure of CuLDH catalyst, and an appropriate amount of Ce increased the surface area of the catalyst and improved the dispersion of Cu particles. At the same time, an appropriate amount of Ce was beneficial for increasing the density of strong alkaline sites and the number of oxygen vacancies on the catalyst surface, promoting the adsorption and conversion of CO₂. Ce was beneficial for adjusting the Cu⁺/Cu⁰ ratio on the catalyst surface, and a higher Cu⁺/Cu⁰ ratio was conducive to the formation of methanol. When the Ce/Cu ratio was 0.3, the catalyst exhibited higher activity with 7.5% CO₂ conversion, 78.4% methanol selectivity and 362.8 g/(kg·h) spatiotemporal yield at 240 °C under 2.5 MPa with a GHSV=9000 mL/(g·h). It was proved by in-situ DRIFTS that CuLDH-Ce0.3 catalyst followed HCOO* reaction path during CO₂ hydrogenation for methanol.