Palladium Nanoparticles in Glycerol: A Versatile Catalytic System for CX Bond Formation and Hydrogenation Processes (original) (raw)
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Applied Catalysis B: Environmental, 2015
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 1hydroxyacetone and the subsequent hydrogenation of 1-hydroxyacetone to propylene glycol. Highlights The transfer hydrogenolysis of glycerol is promoted by coprecipitated Pd-catalysts The reaction solvent (2-propanol) was used as hydrogen-donor Pd-Co and Pd-Fe ensembles have been identified as the active catalytic phases CTH mechanism involves the glycerol dehydration and subsequent hydrogenation
Silica-supported palladium nanoparticles show remarkable hydrogenation catalytic activity
Journal of Molecular Catalysis A: Chemical, 2003
Palladium nanoparticles (1.9 nm) stabilized on silica were obtained from the reduction of an organometallic precursor (palladium(II) bis-dibencylidene acetone) with dihydrogen. This material was investigated in the hydrogenation catalysis of different substrates (1-hexene, cyclohexene, benzene, 2-hexanone, cyclohexanone and benzonitrile). The solid was used as a heterogeneous catalyst. The highest hydrogenation rate was found with 1-hexene with a TOF of 38,250 mole of product/(mole of metal/h) at 25 • C and 30 psi pressure. The [Pd/SiO 2 ] nanocatalyst has shown remarkably high activity for the catalytic hydrogenation of cyclohexene (TOF 33,000) and benzene (TOF 10,000). This is the first reported palladium nanocatalyst with high catalytic activity towards the hydrogenation of 2-hexanone TOF 16,000, cyclohexanone TOF 15,000 and benzonitrile TOF 5000 reported to the date.
Chemistry – A European Journal, 2016
Bifunctional mesoporous silica was prepared by co‐condensation of tetraethyl orthosilicate (TEOS) with functionalized organosilanes containing azides or alkoxyamines. Orthogonal functional groups at the particles were selectively addressed in subsequent chemical modifications through “click”‐chemistry (“click to ligand” strategy) and radical nitroxide exchange. Palladation with PdCl2 delivered Pd nanoparticle‐loaded silica material bearing sulfoxides and additional aminoamides as stabilizing ligands by means of in situ reduction of the PdII‐salt. These functional particles were successfully applied to the hydrogenation of alkynes and alkenes. Aldehyde hydrodeoxygenation and benzyl ether cleavage were achieved with these hybrid catalysts under mild conditions. Particles were analyzed by IR, TEM/STEM, EDX, and solid‐state NMR spectroscopy.
Catalysts
The catalytic conversion of glycerol to value-added propanols is a promising synthetic route that holds the potential to overcome the glycerol oversupply from the biodiesel industry. In this study, selective hydrogenolysis of 10 wt% aqueous bio-glycerol to 1-propanol and 2-propanol was performed in the vapor phase, fixed-bed reactor by using environmentally friendly bifunctional Pd/MoO3-Al2O3 catalysts prepared by wetness impregnation method. The physicochemical properties of these catalysts were derived from various techniques such as X-ray diffraction, NH3-temperature programmed desorption, scanning electron microscopy, 27Al NMR spectroscopy, surface area analysis, and thermogravimetric analysis. The catalytic activity results depicted that a high catalytic activity (>80%) with very high selectivity (>90%) to 1-propanol and 2-propanol was obtained over all the catalysts evaluated in a continuously fed, fixed-bed reactor. However, among all others, 2 wt% Pd/MoO3-Al2O3 catalys...
Journal of Catalysis, 2012
We developed an efficient, simple chemical reduction method to produce highly active palladium (Pd) nanoparticles in polyethylene glycol (PEG) with no other stabilizer. The as-prepared Pd/PEG catalyst demonstrated a remarkable catalytic activity toward hydrogenation of both styrene and nitrobenzene under mild conditions. The Pd-PEG catalyst could be easily removed from the reaction mixture and its recyclability with no loss of activity was possible for seven times in case of styrene and three cycles for nitrobenzene. The catalytic performance was found to depend essentially on the catalyst and target concentrations and the reaction time. The catalyst was fully characterized by a variety of techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and N 2 adsorption-desorption isotherm. The reactivity of the Pd/PEG catalyst toward hydrogenation reactions is attributed to the high degree of dispersion of Pd(0) nanoparticles in PEG with small average particle size distribution of 5 nm. Results of the synthesis and characterization of Pd/PEG catalyst and its catalytic performance for hydrogenation reactions are presented and thoroughly discussed.
RSC Advances, 2014
The development of green, economical and sustainable chemical processes is one of the primary challenges in organic synthesis. Herein, we report an efficient and heterogeneous palladium-catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates via decarboxylative cross-coupling. Both aliphatic and aromatic sulfinate salts react with various vinyl cyclic carbonates to deliver the desired allylic sulfones featuring tri-and even tetrasubstituted olefin scaffolds in high yields with excellent selectivity. The process needs only 2 mol% of Pd 2 (dba) 3 and the in situ formed palladium nano-particles are found to be the active catalyst. Scheme 1 Cross coupling of vinyl cyclic carbonates for C-S bond formation. (a) Homogeneous catalysis (b) heterogeneous catalysis.
Hydrogenation of Allyl Alcohols Catalyzed by Aqueous Palladium and Platinum Nanoparticles
RSC Adv., 2015
A series of Pd and Pt nanoparticles (NPs) was prepared starting from the corresponding metal ions and lignosulphonates; NPs were tested as catalysts for allyl alcohols hydrogenation in water at room temperature and pressure. All NPs were active with sharp differences in conversions and selectivities: Pt NPs formed mainly saturated alcohols, whereas Pd NPS were more active, but less selective, forming, in addition to saturated alcohols, also isomeric unsaturated alcohols and aldehydes, both saturated and unsaturated.
Journal of Catalysis, 2000
We here report the preparation of supported palladium nanoparticles (NPs) stabilized by pendant phosphine groups by reacting a palladium complex containing the ligand 2-(diphenylphosphino)benzaldehyde with an amino-functionalized silica surface. The Pd nanocatalyst is active for Suzuki cross-coupling reaction avoiding any addition of other sources of phosphine ligands. The Pd intermediates and Pd NPs were characterized by solid-state nuclear magnetic resonance and transmission electron microscopy techniques. The synthetic method was also applied to prepare magnetically recoverable Pd NPs leading to a catalyst that could be reused for up to 10 recycles. In summary, we gathered the advantages of heterogeneous catalysis, magnetic separation and enhanced catalytic activity of palladium promoted by phosphine ligands to synthesize a new catalyst for Suzuki cross-coupling reactions. The Pd NP catalyst prepared on the phosphine-functionalized support was more active and selective than a similar Pd NP catalyst prepared on an amino-functionalized support.Magnetically recoverable supported Pd nanoparticles stabilized by pendant phosphine groups exhibited good activity and high selectivity in Suzuki cross-coupling reaction.
Advanced Synthesis & Catalysis, 2008
A series of palladium nanoparticles stabilized by five chiral sugar-based oxazolinyl-phosphite ligands, containing various substituents at the oxazoline and phosphite moieties has been synthesized. They were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and elemental analysis. These nanoparticles were applied in Pd-catalyzed asymmetric allylic alkylation and Heck coupling reactions. A detailed study to elucidate the nature of the active species using a continuous-flow membrane reactor (CFMR), accompanied by TEM observations, classical poisoning experiments, and kinetic measurements have been carried out. Conclusive evidence of the nature of the species involved in the use of PdNPs in asymmetric catalytic reactions has been obtained. The CFMR experiments proved the molecular nature of the true catalysts and all conversions can be justified by the amount of molecular palladium that leached as measured by ICP-AES.