The addition of Ga to Cu/SiO2 generates new active sites increasing selectivity to methanol. The mechanistic implications are studied by in situ DRIFTS and kinetic experiments.

The hydrogenation of CO2 to methanol is a viable alternative for mitigating greenhouse gases net emissions as well as a route for hydrogen storage and transportation. In this work, we...

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

Catalytic pyrolysis has been used to upgrading the quality of pyrolytic liquids. Herein, we report a comprehensive study on the catalytic pyrolysis of waste tires using Ni/SiO2 as catalysts. The analyses were carried out by combining thermogravimetry (TGA), TGA interfaced to a Fourier Transform Infrared spectrometer (TGA-FTIR), and pyrolysis coupled to gas chromatography/mass spectrometer (Py-GC/MS) techniques. During waste tire decomposition, the main functional groups detected in the FTIR were alkenes, aromatics, and heteroatoms-containing groups such as nitrogen, sulfur, and oxygen. Meanwhile, by Py-GC/MS were identified mainly D,L-limonene, isoprene, benzene, toluene, xylenes (BTX), and p-cymene. The Py-GC/MS experiments at three different temperatures (350, 400, and 450 °C) suggested an effect of the catalyst on product distribution. The Ni catalyst promoted cyclization reactions and subsequently aromatization, leading to an improved vapors composition. The use of iso-conversional kinetic models along with master plots allows proposing a multiple-step reaction mechanism, which was well described by the Avrami-Erofeev, Random Scission, and truncated Sestak-Berggren models. The values of activation energies show differences for the catalyzed and uncatalyzed pyrolysis (111.0 kJ mol -1 and 168.4 kJ mol -1 ), validating the effectivity of Ni/SiO2. Finally, the thermal Biot (>1) and Py I and Py II numbers (10 -3

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