CuO-In 2 O 3 Catalysts Supported on Halloysite Nanotubes for CO 2 Hydrogenation to Dimethyl Ether.

Hydrogenation of CO₂ relative to valuable chemical compounds such as methanol or dimethyl ether (DME) is an attractive route for reducing CO₂ emissions in the atmosphere. In the present work, the hydrogenation of CO₂ into DME over CuO-In₂O₃, supported on halloysite nanotubes (HNT) was investigated in the temperature range 200–300 °C at 40 atm. HNT appears to be novel promising support for bifunctional catalysts due to its thermal stability and the presence of acidic sites on its surface. CuO-In₂O₃/HNT catalysts demonstrate higher CO₂ conversion and DME selectivity compared to non-indium CuO/HNT catalysts. The catalysts were investigated by N₂ adsorption, X-ray diffraction, hydrogen-temperature programmed reduction and transition electron microscopy. The acid sites were analyzed by temperature programmed desorption of ammonia. It was shown that CuO/HNT was unstable under reaction conditions in contrast to CuO-In₂O₃/HNT. The best CuO-In₂O₃/HNT catalyst provided CO₂ conversion of 7.6% with 65% DME selectivity under P = 40 atm, T = 250 °C, gas hour space velocity 12,000 h⁻¹ and H₂:CO₂ = 3:1. [ABSTRACT FROM AUTHOR]