Sebastiano Campisi

Pd‐modified Au on Carbon as an Effective and Durable Catalyst for the Direct Oxidation of HMF to 2,5‐Furandicarboxylic Acid

Mixed noblility: We show that the modification of a gold/carbon catalyst with platinum or palladium produces stable and recyclable catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA): the support and nanoparticle chemistry directly mediate the selective oxidation of terminal hydroxyl groups in bio-derived HMF. This finding is a significant advance over current conversion technology because of the technological importance of FDCA.

NiO as a peculiar support for metal nanoparticles in polyols oxidation

The peculiar influence of a NiO support was studied by preparing gold catalysts supported on NiO1−x–TiO2 x mixed oxides. PVA protected Au nanoparticles showed high activity when supported on NiO for the selective oxidation of glycerol and ethane-1,2-diol. A detailed characterization of the resulting Au catalysts revealed a preferential deposition of the metal nanoparticles on the NiO phase. However, the activity of Au on NiO1−x–TiO2 x decreased with respect to pure NiO and the selectivity evolved with changes in the support.

Tailoring the selectivity of glycerol oxidation by tuning the acid–base properties of Au catalysts

Supported gold nanoparticles are very effective catalysts for the selective oxidation of glycerol which represents an important bio-derived feedstock. In this paper we report that the acid/base properties, especially the acid site density, of these catalysts are the key factor in tuning the selectivity. A range of supported AuPt catalysts have been prepared by sol immobilization using acidic (H-mordenite, SiO2, MCM-41, and sulfated ZrO2) and basic (NiO and MgO) oxides as supports. In particular, using MCM-41 as the support, a high selectivity to glyceraldehyde, an important labile intermediate, was found.

Operando Attenuated Total Reflectance FTIR Spectroscopy: Studies on the Different Selectivity Observed in Benzyl Alcohol Oxidation

Au, Pd, and AuPd supported on TiO2 were prepared by a sol immobilization route. Operando attenuated total reflectance (ATR) IR spectroscopy and catalytic batch reactor experiments were performed in parallel to elucidate the different catalytic performance of the catalysts in the liquid‐phase oxidation of benzyl alcohol. Pd/TiO2 exhibited a higher activity than AuPd/TiO2 and Au/TiO2, but the modification of Pd with Au demonstrated a significant stability enhancement. ATR‐IR spectroscopy evidenced that the presence of Au facilitates the desorption of byproducts, which thus reduces the extent of deactivation of the active sites caused by the irreversible adsorption of benzoate species. Although benzaldehyde was the main product in both catalysts, the nature of the byproducts differs. Pd/TiO2 favored the deoxygenation of benzyl alcohol to produce toluene as the main byproduct. Conversely, AuPd/TiO2 promoted the transformation of benzaldehyde to benzoic acid.

The confinement effect on the activity of Au NPs in polyol oxidation

We demonstrate a confinement effect where gold nanoparticles trapped within N-functionalized carbon nanofibers (N-CNFs) are more active for polyol oxidation and promote selectivity towards di-acid products, whereas AuNPs trapped on the surface produce as a major by-product the one derived from C–C cleavage. The behaviour of NPs confined inside the N-CNF channels can be attributed to a different, possibly multiple, coordination of glycerol on the active site.

Fragrances by selective oxidation of long-chain alcohols

Abstract The activity and the selectivity of Ru and Pt based carbon catalysts in the selective oxidation of long-chain aliphatic alcohols (C8, C10, C12) have been investigated. Ru/AC and Pt/AC always showed good initial activity, however deactivation phenomena rapidly depressed the catalytic performance of the catalysts. These phenomena can be limited by modification of Ru/AC and Pt/AC with Au improving the durability of the catalyst. Ru/AC and AuRu/AC showed good selectivity to the corresponding aldehyde (>95%) making these catalysts promising for fragrances manufacturing. The advantage in using Au modified catalyst lies on the easier regeneration procedure compared to the one necessary for Ru/AC. Pt/AC and AuPt/AC showed a lower selectivity to aldehyde promoting the formation of the acid and the ester formation respectively. The addition of water in the solvent system speeds up the reaction rate but drastically decreased the selectivity to aldehyde especially in the case of Pt based catalysts.

N-Modified Carbon-Based Materials: Nanoscience for Catalysis

Carbon-based materials constitute a large family of materials characterized by some peculiarities such as resistance to both acidic and basic environments, flexibility of structure, and surface chemical groups. Moreover, they can be deeply modified by simple organic reactions (acid-base or redox) to acquire different properties. In particular, the introduction of N-containing groups, achieved by post-treatments or during preparation of the material, enhances the basic properties. Moreover, it has been revealed that the position and chemical nature of the N-containing groups is important in determining the interaction with metal nanoparticles, and thus, their reactivity. The modified activity was addressed to a different metal dispersion. Moreover, experiments on catalysts, showing the same metal dispersion, demonstrated that the best results were obtained when N was embedded into the carbon structure and not very close to the metal active site.

Au-Based Catalysts: Electrochemical Characterization for Structural Insights.

Au-based catalysts are widely used in important processes because of their peculiar characteristics. The catalyst performance depends strongly on the nature and structure of the metal nanoparticles, especially in the case of bimetallic catalysts where synergistic effects between the two metals can be occasionally seen. In this paper, it is shown that electrochemical characterisation (cyclovoltammetry CV and electrochemical impedance spectroscopy EIS) of AuPd systems can be used to determine the presence of an electronic interaction between the two metals, thus providing a strong support in the determination of the nature of the synergy between Au and Pd in the liquid phase oxidation of alcohols. However, it seems likely that the strong difference in the catalytic behavior between the single metals and the bimetallic system is connected not only to the redox behaviour, but also to the energetic balance between the different elementary steps of the reaction.

Tailored N-Containing Carbons as Catalyst Supports in Alcohol Oxidation

The introduction of N-containing functionalities in carbon-based materials is brought to stable and highly active metal-supported catalysts. However, up to now, the role of the amount and the nature of N-groups have not been completely clear. This study aims to clarify these aspects by preparing tailored N-containing carbons where different N-groups are introduced during the synthesis of the carbon material. These materials were used as the support for Pd nanoparticles. Testing these catalysts in alcohol oxidations and comparing the results with those obtained using Pd nanoparticles supported on different N-containing supports allowed us to obtain insight into the role of the different N-containing groups. In the cinnamyl alcohol oxidation, pyridine-like groups seem to favor both activity and selectivity toward cinnamaldehyde.

Amino Alcohol Oxidation with Gold Catalysts: The Effect of Amino Groups

Gold catalysts have been prepared by sol immobilization using Tetrakis(hydroxymethyl) phosphonium chloride (THPC) as a protective and reducing agent or by deposition on different supports (Al2O3, TiO2, MgAl2O4, and MgO). The catalytic systems have been tested in the liquid phase oxidation of aminoalcohols (serinol and ethanolamine) and the corresponding polyols (glycerol and ethylene glycol). This comparison allowed us to state that the presence of amino groups has a crucial effect on the catalytic performance, in particular decreasing the durability to the catalysts, but did not substantially vary the selectivity. A support effect has been as well established.