Effect of the synthesis method on the performance of Ni-CeO2-ZrO2 catalysts for the hydrogenolysis of glycerol with endogenous hydrogen

In this work, we investigated the influence of the synthesis method of Ni-based CeZr catalysts on their physicochemical and catalytic properties in the hydrogenolysis (HDO) of glycerol with H2 in-situ produced by the aqueous-phase reforming (APR). Conventional impregnation method involved surface nickel deposition (NiCeZr-IM). The one-pot methods, which involved nickel embedment into CeZr lattice, included sol-gel (NiCeZr-SC) and coprecipitation (NiCeZr-CA and ultrasound-assisted NiCeZR-CS) methods. Differences in textural, structural, morphological, redox, and surface properties, together with and catalytic performance in the glycerol APR-HDO, were investigated systematically. As well, spent catalysts were deeply characterized. There were notable differences among textural properties, which significantly affected their activity in glycerol conversion. The structural characterization confirmed the successful integration of Ni into the CeZr lattice, especially for the catalysts synthesized using one-pot methods. One-pot synthesized catalysts showed stronger Ni-CeZr interaction, which affect the reducibility. The catalysts prepared by coprecipitation contained the highest metal-to-acid ratio, making them very active for C-O bond hydrogenation. Post-reaction characterization discloses a leaching of the nickel, in greater amount for both coprecipitated catalysts. This study revealed the potential of Ni-based catalysts derived from subsurface insertion of nickel into the CeZr matrix for the hydrogenolysis of glycerol without external hydrogen.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0

Hydrogenolysis of Glycerol over NiCeZr Catalyst Modified with Mg, Cu, and Sn at the Surface Level

Biomass valorization is an essential strategy for converting organic resources into valuable energy and chemicals, contributing to the circular economy, and reducing carbon footprints. Glycerol, a byproduct of biodiesel production, can be used as a feedstock for a variety of high-value products and can contribute to reducing the carbon footprint. This study examines the impact of surface-level modifications of Mg, Cu, and Sn on Ni-Ce-Zr catalysts for the hydrogenolysis of glycerol, with in situ generated hydrogen. The aim of this approach is to enhance the efficiency and sustainability of the biomass valorization process. However, the surface modification resulted in a decrease in the global conversion of glycerol due to the reduced availability of metal sites. The study found that valuable products, such as H2 and CH4 in the gas phase, and 1,2-PG in the liquid phase, were obtained. The majority of the liquid fraction was observed, particularly for Cu- and Sn-doped catalysts, which was attributed to their increased acidity. The primary selectivity was towards the cleavage of the C–O bond. Post-reaction characterizations revealed that the primary causes of deactivation was leaching, which was reduced by the inclusion of Cu and Sn. These findings demonstrate the potential of Cu- and Sn-modified Ni-Ce-Zr catalysts to provide a sustainable pathway for converting glycerol into value-added chemicals.This research was supported by grant PID2019-106692RB-I00 funded by MCIN/AEI/10.13039/501100011033. N.V.H. would like to thank MICINN for the pre-doctoral grant (BES-2017-081580). Likewise, the authors thank for technical support provided by SGIker of UPV/EHU and European funding (ERDF and ESF)