Hydrogenolysis of glycerol to obtain 1,2-propanediol on Ce-promoted Ni/SBA-15 catalysts
Metallic Ni (10 wt.%) supported on SBA-15 silica and promoted with cerium loading ranged between 2.5 and 10 wt.%, reduced at 723 K during 1 h, were used as catalysts in the hydrogenolysis of a glycerol aqueous solution (80 wt.%) at 473 K and 2.4 MPa of H2 pressure. Whereas pure Ni catalyst mainly produces volatile products by CC hydrogenolysis reaction, the promoted cerium catalysts lead to the formation of 1,2-propanediol (1,2-PDO) as majority product. After 8 h of reaction the catalyst with 10 wt.% of Ni and 7.5 wt.% of Ce gives the maximum glycerol conversion and selectivity to 1,2-PDO, with yield of this substance of 24.2%/g of catalyst. The presence of cerium species is essential to produce 1,2-PDO. The effect of cerium oxide is to act as strong acid sites (TPD-NH3), improve the metallic Ni dispersion (XRD, H2 chemisorption and XPS) and to make more difficult their reduction (TPR). The stronger acidity suggests that the formation of acetol takes place easier in these catalysts and subsequently this intermediate is reduced by activated hydrogen from the nearby Ni metallic sites.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Bifunctional catalysts were prepared by impregnation of SBA-15 silica with nickel and cerium. ► The catalysts are active in the hydrogenolysis of glycerol at 473 K and 2.4 MPa of H2 pressure. ► The presence of cerium ions is essential to produce 1,2-PDO. ► Cerium ions act as strong acid sites producing acetol as intermediate.
Journal: Applied Catalysis B: Environmental - Volumes 117–118, 18 May 2012, Pages 253–259