CO₂ Hydrogenation to Methanol with Ga‐ and Zn‐Doped Mesoporous Cu/SiO₂ Catalysts Prepared by the Aerosol‐Assisted Sol‐Gel Process**

Abstract

The preparation of copper-based heterogeneous catalysts dedicated to the hydrogenation of CO2 to methanol typically relies on multi-step procedures carried out in batch. These steps are precisely tailored to introduce the active phase (Cu) and the promoters (e.g. zinc, gallium) onto a preformed support, to maximize catalyst performance. However, each process step-often carried out in batch-can be associated with the formation of waste and with the consumption of energy, thereby negatively impacting the environmental performance of the overall catalyst preparation procedure. Here, we propose a direct and continuous production process for the synthesis of efficient catalysts for the CO2 to methanol reaction. Gallium-and zinc-promoted mesoporous Cu-SiO2 catalysts are prepared in one step by the aerosol-assisted sol-gel process. The catalysts consist of spherical microparticles and feature high specific surface area and pore volume, with interconnected pores of about 6 nm. A strong promoting effect of Ga and Zn is highlighted, boosting the selectivity for methanol at the expense of CO. Upon calcination, we show that Cu species-initially trapped in the silica matrix-undergo a migration towards the catalyst surface and a progressive sintering. After optimization, the catalysts obtained via such direct route compete with the best catalysts reported in the literature and obtained via multi-step approaches. File list (2) download file view on ChemRxiv Debecker CO2 MeOH aerosol Cu Ga Zn SiO2-preprint.pdf (1.82 MiB) download file view on ChemRxiv Debecker CO2 MeOH aerosol Cu Ga Zn SiO2-GA.docx (238.46 KiB) CO 2 hydrogenation to methanol with Ga-and Zn-doped mesoporous Cu/SiO 2 catalysts prepared by the aerosol-assisted sol-gel process

Why ZnO is the Support for Cu in Methanol Synthesis? A Systematic Study of the Strong Metal Support Interactions

“…Aside from Zn, only Ga is capable of partial wetting of the Cu(211) surface/step-edge, although to a less extent, compared to Zn. Promotion of Cu and CuZn by Ga for methanol synthesis has been widely reported, − although seldom has it been discussed as a result of SMSI along the lines of ZnO.…”

Cu–Ga2O3nanoparticles supported on ordered mesoporous silica for the catalytic hydrogenation of cinnamaldehyde

“…It was also suggested that the Ga 2 O 3 particles supported on mesoporous silica supports can act as strong anchoring sites for the Cu species, leading to a better dispersion, as compared with the monometallic Cu materials [38]. It was stressed that the dispersion of Ga 2 O 3 should be equally high to create a high interfacial area between the oxide promoter and the metallic Cu NPs [40].…”

“…Hence, it can be possible to generate electron deficient Ga δ+ sites with affinity to the C=O groups, near the metallic Cu 0 sites. There are few encouraging reports on the efficient Ga 2 O 3 promotion for other Cu NPs-catalysed selective hydrogenation reactions, such as the hydrogenation of CO 2 to methanol over CuZnGaO x [33], Cu-Ga 2 O 3 /ZrO 2 [34], Cu-Ga 2 O 3 -ZnO/ZrO 2 [35,36], Cu-Ga 2 O 3 /SiO 2 [37][38][39], Cu-Ga 2 O 3 -ZnO/SiO 2 [40], and Cu-Ga 2 O 3 -ZnO/HZSM-5 [41]. Nevertheless, the Ga 2 O 3 promoter effects are little studied for the hydrogenation of α, β-unsaturated aldehydes (i.e., the hydrogenation of citral over Pt-Ga 2 O 3 /C, and the hydrogenation of cinnamaldehyde over Cu-Ga 2 O 3 /HNZY) [30,42].…”

Aerosol-assisted sol-gel synthesis of mesoporous Ag-Ta-SiO2 catalysts for the direct upgrading of ethanol to butadiene

“…This aerosol route was shown to give access to a variety of efficient (mixed) oxide catalysts with a high degree of control on homogeneity and texture [32][33][34][35] . The method can also be used to prepare supported metal nanoparticles [36][37][38] . This prompted us to explore the potential of AASG to obtain mesoporous Ta-SiO2 catalysts promoted with Ag nanoparticles and to assess their performance in the ETB reaction.…”