Francesco Mauriello

Selective transfer hydrogenolysis of glycerol promoted by palladium catalysts in absence of hydrogen

Selective conversion of glycerol into 1,2-propanediol in the presence of a Pd/Fe2O3catalyst, under inert atmosphere, is reported for the first time; the hydrogen necessary for the hydrogenolysis reaction derives from the dehydrogenation of the solvent (2-propanol or ethanol), promoted by supported palladium, itself reduced “in situ” by alcohols.

Glycerol hydrogenolysis promoted by supported palladium catalysts.

Catalytic hydrogenolysis, with high conversion and selectivity, promoted by supported palladium substrates in isopropanol and dioxane at a low H(2) pressure (0.5 MPa), is reported for the first time. The catalysts, characterized by using BET isotherms, transmission electron microscopy (TEM), temperature-programmed reduction (TPR), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were obtained by coprecipitation and impregnation techniques. The coprecipitation method allows catalysts with a metal-metal or a metal-support interaction to be obtained, which enhances the catalytic performance for both the conversion of glycerol and the selectivity to 1,2-propanediol. Analogous reactions carried out with catalysts prepared by using impregnation are less efficient. A study of the solvent and temperature effect is also presented. The obtained results allow the hydrogenolysis mechanism to be inferred; this involves both the direct replacement of the carbon-bonded OH group by an incoming hydrogen or the formation of hydroxyacetone as an intermediate, which subsequently undergoes a hydrogenation process to give 1,2-propanediol. Finally, catalytic tests on a large-scale reaction at a higher H(2) pressure and recycling of the samples were carried out with the better performing catalysts (Pd/CoO and Pd/Fe(2)O(3) prepared by using coprecipitation) to verify possible industrial achievements.

Hydrogenolysis vs. aqueous phase reforming (APR) of glycerol promoted by a heterogeneous Pd/Fe catalyst

The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated under mild reaction conditions, using water as the reaction medium and Pd/Fe as the catalyst. The experiments, in the presence of added H2 or under inert atmosphere, clearly show that the dehydration/hydrogenation route is the key step in the case of C–O bond cleavage (hydrogenolysis) while dehydrogenation is a prerequisite for C–C bond breaking (APR), with the latter favoured at higher reaction temperatures. The temperature dependence of the C–C and C–O bond rupture is discussed by taking into account the bond energies involved in the competitive hydrogenolysis and APR reactions. Finally, the Pd/Fe catalyst was also tested in the hydrogenolysis and APR of ethylene glycol in the same temperature range, with the aim of clarifying the selective cleavage of C–O and C–C bonds in biomass derived C2–C3 polyols.

Selective arene production from transfer hydrogenolysis of benzyl phenyl ether promoted by a co-precipitated Pd/Fe3O4 catalyst

The catalytic transfer hydrogenolysis of benzyl phenyl ether has been investigated using Pd/Fe3O4 as a heterogeneous catalyst and 2-propanol as a H-donor. After 90 minutes at 240 °C, the cleavage of the ether C–O bond occurs as the only reaction route without hydrogenation of the aromatic ring.

Directing the Cleavage of Ester C−O Bonds by Controlling the Hydrogen Availability on the Surface of Coprecipitated Pd/Fe3O4

The ready availability of esters from natural sources makes them promising substrates for the sustainable production of key intermediates of the chemical industry. In this context, methods to selectively cleave the alkoxy or ester C−O bond to obtain either alkane+acid or alcohol+aldehyde were investigated. Using Pd/Fe3O4(r) [(r)=reduced] as the catalyst of choice and either 2‐propanol—as indirect H source—or molecular hydrogen—as ample H source—the hydrogen coverage on the surface of the catalyst was controlled. This enabled selective cleavage of either the alkoxy C−O bond or the ester C−O bond in aromatic esters as shown for the hydrogenolysis of 2‐phenylethylacetate as model substrate. Noteworthy, hydrogenation of the aromatic ring was not observed. Thus, an exceptionally high chemoselectivity of Pd/Fe3O4(r) to hydrogenolysis of the ester group is combined with the option to readily direct the regioselectivity.

Photoresponsive polymers containing side-chain chiral azocarbazole chromophores as multifunctional materials

A new optically active photochromic polymethacrylate containing the carbazole moiety, deriving from the chiral monomer (S)-(4-cyanophenyl)-[3-[9-[2-(2-methacryloyloxypropanoyloxy) ethyl]carbazolyl]]diazene [(S)-MLECA] has been prepared and fully characterized with the aim to obtain a multifunctional material which can be considered at the same time as a photonic material for NLO and optical storage, for chiroptical switches, and for photorefractive and photoconductive applications. The complete reversibility of the photoinduced linear birefringence, which is related to fatigue resistance properties seems to be promising for use in optical storage or more generally in the field of photoresponsive systems, and it is not necessary to add dopants in order to observe photoconduction thanks to the presence of the carbazole moiety, which is well known for its hole conducting properties.

New Prospects for the Characterization of Heterogeneous Catalysts by Using Slow Muon Spectroscopy

In this contribution we show two examples concerning catalyses to consider the possible applications of slow muon to characterize catalytic systems. One is a Pd/Fe3O4 catalyst that can be used in the catalytic valorization of glycerol, a product from biomass. The other is Pt/SnO2 for a CH4 sensor application. We present the unsolved problems and stress the importance on the in situ characterization. We discuss the possibility of slow muon for the in situ characterization of oxide catalyst material.

Synthesis and chiroptical properties of methacrilic copolymers containing in side-chain optically active carbazole and azochromophores

Novel optically active multifunctional methacrylic copolymers bearing in the side chain azoaromatic and carbazole groups linked to the main chain with a chiral rigid group of one prevailing absolute configuration have been prepared and characterized in order to observe possible effects on the optical activity of the resulting materials. All the polymeric derivates have good thermal stability with glass transition temperature around 200°C and high decomposition temperatures in the range 280-300°C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions between side chain moieties and the presence of an ordered chiral conformation at least for chain segments of the macromolecules.