CO2 hydrogenation to light olefins over highly active and selective Ga-Zr/SAPO-34 bifunctional catalyst

Abstract

The production of light olefins from the hydrogenation of CO₂ is an efficient way to utilize CO₂, where the surface oxygen vacancy in metal oxide plays an important role in CO₂ adsorption and activation. Here, the Ga-Zr metal oxides were prepared by hydrolysis of urea at different temperatures and combined with SAPO-34 to prepare the bifunctional catalyst for CO₂ hydrogenation to light olefins. The surface oxygen vacancy content of Ga-Zr oxide increases with increasing urea hydrolysis temperature, and a high CO₂ conversion of 26.4% and C₂⁼–C₄⁼ hydrocarbon selectivity of 87.2% were obtained by a well-matched amount of desorbed CO₂ and H₂. Using the CO₂ and H₂/HCOOH/CH₃OH as probe molecules, the in-situ DRIFT spectra reveal that the CO₂ could be activated on surface oxygen vacancy and converted to CO₃* and HCO₃* species, which were further hydrogenated to HCOO* and CH₃O* species. While the by-product CO mainly originates from the decomposition of HCOO* and the presence of SAPO-34 converts CH₃O* to C₂⁼–C₄⁼. The current study illustrates that boosting the surface oxygen vacancy in defected surfaces of metal oxide and providing a matching H₂ dissociation ability is the key to improve the performance of CO₂ hydrogenation to light olefins.