Turning Glycerol to Value-Added Chemicals in the Absence of External Hydrogen over Copper Catalysts Supported on SBA-15-Type Materials Containing Zirconium

Nowadays, many industrial processes depend on fossil resources to obtain high-added-value chemical compounds, bringing with it significant environmental deterioration. Therefore, the implementation of green alternatives considering the use of biomass residues in hydrogen-free catalytic processes is of great relevance. In this work, a set of copper catalysts prepared by impregnating SBA-15 and Zr-SBA-15 (different Si/Zr ratios) supports were catalytically tested in the glycerol dehydration. The copper catalysts were characterized by ICP, SEM-EDS, N 2 physisorption, XRD, HRTEM, FT-IR, UV–Vis DRS, XPS, H 2 -TPR, N 2 O chemisorption, and TPO analyses. ICP revealed a suitable agreement between nominal and actual copper content in the catalysts. Copper catalysts exhibited textural and structural properties of mesoporous materials which are affected by increasing Zr content. Pyridine FT-IR indicated that copper catalysts with lower Zr content possess the highest values of Lewis acid sites. Higher Zr content makes the copper reduction more difficult, and the dispersion is unfavored. The catalytic system was studied using an 80% wt. aqueous glycerol solution in inert conditions at 220 °C without diffusional limitations according to the Weisz–Prater and Mears criteria. The highest values of specific initial reaction rate and rate constant were obtained in catalysts with zero (Cu/B catalyst, 1.50 × 10 −3 mol gl /min g cat , 7.79 × 10 −4 min −1 ) and low (Cu/B10 catalyst, 1.53 × 10 −3 mol gl /min g cat , 8.27 × 10 −4 min −1 ) Zr loading. Hydroxyacetone (HA) and 1,2-propanediol (1,2-PDO) were the main formed products. HA formation reached values greater than 90% selectivity in the first minutes of the reaction, while 1,2-PDO achieved a progressive evolution over time up to 9% selectivity. Initial formation rates of HA (3.29 × 10 −4 mol HA /min g cat ) and 1,2-PDO (2.13 × 10 −5 mol 1,2−PDO /min g cat ) were optimized on the Cu/B10 catalyst containing the lowest Zr load. 1,2-PDO generation in the absence of external hydrogen with a high concentration of glycerol simulating industrial wastes is highlighted. Finally, the Zr load in the copper catalysts modulates the textural, structural, acidic, surface, and reducible properties, which can also be considered as descriptors to understand the catalytic activity together with exposed copper species, stability against copper leaching, sintering, and carbon deposition.