Exploring the catalytic properties of supported palladium catalysts in the transfer hydrogenolysis of glycerol

Abstract

The transfer hydrogenolysis of glycerol promoted by supported palladium catalysts is reported. The reactions were carried out under mild conditions (453 K and 5 bar of N 2 ) in absence of added hydrogen by using the reaction solvent, 2-propanol, as hydrogen source. The catalytic results are interpreted in terms of metal (Pd) -metal (Co or Fe) interaction that modifies the electronic properties of palladium and affords bimetallic PdM sites (M = Co or Fe), thus enhancing the catalytic properties of the systems in the conversion of glycerol as well as in the selectivity to 1,2-propanediol and 1-propanol. The transfer hydrogenolysis mechanism is here elucidated and involves the glycerol dehydration to 1-hydroxyacetone and the subsequent hydrogenation of 1-hydroxyacetone to propylene glycol.3

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…The same conclusions were drawn by other authors on the H 2 -TPR analysis of various heterogeneous Pd-Fe catalysts, that all agree on the promoting effect of Pd nanoparticles in the reduction of support [128,[131][132][133][134]138]. On this regard, Asakura remarks that Pd nanoparticles can produce hydrogen-spillover onto the Fe oxide surface [138]; Qiao suggests that the promoting effect of Pd in the reduction of hematite to magnetite derives directly from the catalyst preparation method (co-precipitation) [128]; while Tsang highlights that the reduction of the iron support can be further promoted by the assistance of Zn(II) nanoparticles in co-precipitated Pd/Fe catalysts blended with Zn(II) [132,133].…”

“…In general, supported Pd-Fe catalysts with a strong metal-metal and/or metal-support interaction can be prepared through the co-precipitation technique [131][132][133][134][135][136][137][138][139]. As highlighted by Tsang and co-workers [131], it is very important to control pre-reduction treatments, in terms of temperature and duration, because they affect the induction time.…”

“…Diffraction patterns of the impregnated catalysts show peaks related to the metallic Pd species and corresponding support structures Fe2O3 and Fe3O4 [205]. Conversely, co-precipitated Pd/Fe catalysts shows only the Fe3O4 pattern and no peaks related to metallic palladium, indicating the presence of ultra-small palladium particles highly dispersed [128,135,138,206,207]. After 24 h of reaction, no structural modification of the Fe3O4 support was monitored, while the presence of the diffraction peak relative to the (111) plane of the palladium is indicative of Pd particles agglomeration [128].…”

“…This method was, so far, used for the synthesis of Pd/Fe 3 O 4 and Pd/Fe 2 O 3 catalysts [135,138,142,193]. In a typical preparation procedure, palladium (II) acetylacetonate is dissolved in acetone and then added to commercially available Fe 3 O 4 or Fe 2 O 3 supports [135,138,192]. After impregnation, samples are dried and reduced under a flow of molecular hydrogen.…”

“…Specifically, results obtained in important "green and sustainable" reactions will be presented including: aqueous-phase reforming [128][129][130], hydrogenolysis [131][132][133][134][135][136] and CTH [137,138] of C6-C2 polyols, hydrogenolysis and transfer hydrogenolysis of furfural [139,140], hydrodeoxygenation of phenol derivatives [141,142], HDO and CTH of aromatic ethers [143][144][145]. All these reactions will be discussed in details with the aim to show the unicity of heterogeneous Pd-Fe catalysts that are suitable for a wide reductive valorization processes of all constituent components of lignocellulosic biomasses having the potential to be successfully used in modern biorefineries to produce simple bulk compounds.…”