Evaluation of Au/ZrO2 Catalysts Prepared via Postsynthesis Methods in CO2 Hydrogenation to Methanol

Highly Efficient Au/ZnO−ZrO2 Catalysts for CO Oxidation at Low Temperature

A series of gold catalysts on ZnO−ZrO2 featuring nominal ZnO loads of 3, 5, and 10 wt. % were synthesized by the sol–gel method using Zn(NO3)2 and zirconium (IV) propoxide aqueous solutions. In addition, gold catalysts with nominal loads between 1 and 3 wt. % were produced by the method of deposition-precipitation with urea, and their performance in the CO oxidation reaction at low temperature was evaluated. HRTEM outcomes revealed high gold dispersion on the 3Au/5ZnO−ZrO2 catalyst with Zn/Zr atomic ratio of (5/95) and 3 wt. % of gold, which showed the highest CO conversion at low temperature (−5 °C) under air treatment when the CO oxidation was carried out with a space velocity of ~46,000 h−1. The incorporation of ZnO to ZrO2 provoked high dispersion of the gold nanoparticles on the support and close size distribution; moreover, the presence of Au1+ and Zr3+ species was increased by the Zr−O−Zn interaction, which was stronger than in the single Au/ZrO2 and Au/ZnO catalysts. DRIFT/GC−MS confirmed that the Au1+/Au0 ratio and formation of carbonate species played an important role in determining the CO conversion; likewise, the 3Au/5ZnO–ZrO2 catalyst was stable at 10 °C for 24 h.

A Review on Green Hydrogen Valorization by Heterogeneous Catalytic Hydrogenation of Captured CO2 into Value-Added Products

The catalytic hydrogenation of captured CO2 by different industrial processes allows obtaining liquid biofuels and some chemical products that not only present the interest of being obtained from a very low-cost raw material (CO2) that indeed constitutes an environmental pollution problem but also constitute an energy vector, which can facilitate the storage and transport of very diverse renewable energies. Thus, the combined use of green H2 and captured CO2 to obtain chemical products and biofuels has become attractive for different processes such as power-to-liquids (P2L) and power-to-gas (P2G), which use any renewable power to convert carbon dioxide and water into value-added, synthetic renewable E-fuels and renewable platform molecules, also contributing in an important way to CO2 mitigation. In this regard, there has been an extraordinary increase in the study of supported metal catalysts capable of converting CO2 into synthetic natural gas, according to the Sabatier reaction, or in dimethyl ether, as in power-to-gas processes, as well as in liquid hydrocarbons by the Fischer-Tropsch process, and especially in producing methanol by P2L processes. As a result, the current review aims to provide an overall picture of the most recent research, focusing on the last five years, when research in this field has increased dramatically.