Liquid-phase glycerol hydrogenolysis to 1,2-propanediol under nitrogen pressure using 2-propanol as hydrogen source

2-Propanol was studied as a hydrogen donor molecule in the transfer hydrogenation process to selectively convert glycerol into 1,2-propanediol under N2 pressure and using Ni or/and Cu supported on Al2O3 catalysts. The results were compared to those obtained under the same operating conditions but under H2 pressure. The results of the activity tests and catalyst characterization techniques (N2-physisorption, H2-chemisorption, TPD of NH3, TPR, TPO and XPS) suggest that glycerol hydrogenolysis to yield 1,2-propanediol occurred through a different mechanism regarding the origin of the hydrogen species. When atomic hydrogen came from dissolved molecular hydrogen dissociation, glycerol was first dehydrated to acetol and then hydrogenated to 1,2-propanediol. On the other hand, when the hydrogen atoms were produced from 2-propanol dehydrogenation, glycerol was directly converted to 1,2-propanediol through intermediate alkoxide formation.

Proposed reaction pathway through alkoxide formation for glycerol hydrogenolysis to yield 1,2-propanediol under N2 pressure using 2-propanol as a hydrogen donor molecule.Figure optionsDownload high-quality image (46 K)Download as PowerPoint slideHighlights
► Glycerol hydrogenolysis under N2 pressure with 2-propanol as hydrogen source.
► 1,2-propanediol was selectively formed on Ni–Cu/Al2O3 catalyst.
► Results were compared to the traditional process under H2 pressure.
► Different mechanisms are involved regarding the origin of hydrogen species.