Intermetallic PdZn/TiO2 catalysts for methanol production from CO2 hydrogenation: The effect of ZnO loading on PdZn-ZnO sites and its influence on activity

In this work, intermetallic PdZn-ZnO catalysts supported on high surface area TiO 2 were synthesized using metal-organic precursors and different Zn/Pd molar ratio (2.5, 5 and 7.5). The use of organic Pd and Zn precursors in the impregnation of TiO 2 has made it possible to achieve the formation of PdO and ZnO nanoparticles that facilitate the uniform formation of small intermetallic β-PdZn particles after reduction with hydrogen at 450 °C. No significant differences in formation, crystallinity or size of intermetallic PdZn particles when varying the Zn concentration in the supported catalysts were observed. The differences were in the characteristics of the ZnO particles that lead to enhanced development of the contacts between the PdZn and ZnO particles as the Zn loading on the catalysts increases. The best methanol yield (78.9 mmol MeOH ·min -1 ·mol Pd -1 ) was obtained over the catalyst with highest ZnO content. This was consequence of the higher development of PdZn-ZnO interfaces where CO 2 adsorption and hydrogenation of intermediate species to methanol increases as well as the higher stability of the largest ZnO particles under reaction conditions. • β-PdZn nanoparticles were supported by impregnation with Pd and Zn acetylacetonate • Enhanced contacts between PdZn and ZnO particles with increase in Zn loading • Crystallinity and size of the ZnO particles affect their stability in reaction • Methanol yield on the PdZn/Ti catalysts increases with increase the Zn content • Hydrogenation of CO 2 to methanol increases with PdZn-ZnO interfaces