Nanosized NiO, CeO2 and NiO-CeO2 mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method. All the samples were characterized by different techniques as to their chemical composition, structure, morphology and texture. On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined. NiO and CeO2 nanocrystals of about 4 nm in size were obtained, regardless of the Ni/Ce molar ratio. The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO2 interface, where Ni species are in strong interaction with the support. The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that, unlike metallic nickel, CeO2 is able to effectively adsorb CO2, forming carbonates and hydrogen carbonates. After reduction in H2 at 400 °C for 1 h, the catalytic performance was studied in the CO and CO2 co-methanation reaction. Catalytic tests were performed at atmospheric pressure and 300 °C, using CO/CO2/H2 molar compositions of 1/1/7 or 1/1/5, and space velocities equal to 72000 or 450000 cm3·h−1·gcat−1. Whereas CO was almost completely hydrogenated in any investigated experimental conditions, CO2 conversion was strongly affected by both the CO/CO2/H2 ratio and the space velocity. The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO2 methanation. On a selected sample, the influence of the reaction temperature and of a higher number of space velocity values, as well as the stability, were also studied. Provided that the Ni content is optimized, the NiCe system investigated was very promising, being highly active for the COx co-methanation reaction in a wide range of operating conditions and stable (up to 50 h) also when submitted to thermal stress.

NiO–CeO2–ZrO2 mixed oxides, with Ni/(Ce + Zr) = 1 mol/mol and different Ce/Zr molar ratios, were prepared by the soft-template method. The chemical composition, texture, structure, and redox features of the synthesized systems were investigated by different techniques. All samples were nanocrystalline (NiO nanocrystal average size 4 nm) and had high surface area and quite an ordered mesoporous system. The catalytic performances in the CO2 conversion into methane were studied at atmospheric pressure, 300 °C, and stoichiometric H2/CO2 molar ratio. Prior to reaction the catalysts were submitted to a mild reduction pretreatment (H2 at 400 °C for 1 h). XRD analysis of the samples after pretreatment showed the presence of small Ni crystals (4–7 nm) on all the samples as well as of some unreduced NiO nanocrystals on the systems with high Zr content, in accordance with H2-TPR experiments, which indicated that NiO reduction is promoted by CeO2 but hindered by ZrO2. The catalytic tests were performed at two different space velocities (72000 and 900000 cm3 h−1 g−1cat) on a series of Ni-based catalysts supported on CeO2–ZrO2 systems with different Ce/Zr ratios, including the two pure oxides. CO2 conversion and selectivity to CH4 (which was always close to 100 mol%) were constant throughout the 6-hour runs. CO2 conversion resulted to increase with CeO2 content in the catalyst, thus indicating the role of the CeO2 component of the support in activating CO2, whereas H2 is activated on the Ni nanoparticles.

Supported nickel catalysts were synthesized, characterized, and employed in the carbon oxides co-methanation process. Five NiO/CeO2-ZrO2 mixed oxides, with the same Ni content and different Ce/Zr molar ratios, were prepared by the soft-template method. They were characterized through ICP-AES, N2 adsorption, XRD, and TPR. Reduced Ni/CeO2-ZrO2 catalysts were obtained by submitting the oxide systems to reduction treatment in H2 at 400 °C. They were characterized by XRD, H2-TPD, and CO2 adsorption microcalorimetry and their catalytic performances in the carbon oxides co-methanation were investigated. Catalytic tests were performed in a fixed-bed continuous-flow microreactor at atmospheric pressure. The effect of experimental conditions (reaction temperature, space velocity, reactants molar ratio) was also studied. Almost complete CO conversion was obtained on any catalyst, whereas CO2 conversion was much lower and increased with Ce content, at least up to Ce/Zr = 1. The beneficial effect of the Ce content could be related to the increased NiO reducibility and to the higher ability to adsorb and activate CO2. However, at high Ce/Zr ratios, it is probably counterbalanced by an interplay of reactions involving CO and CO2.

NiO-CeO₂-ZrO₂ mixed oxides, with Ni/(Ce + Zr) = 1 mol/mol and different Ce/Zr molar ratios, were prepared by the soft-template method. The chemical composition, texture, structure, and redox features of the synthesized systems were investigated by different techniques. All samples were nanocrystalline (NiO nanocrystal average size 4 nm) and had high surface area and quite an ordered mesoporous system. The catalytic performances in the CO₂ conversion into methane were studied at atmospheric pressure, 300 °C, and stoichiometric H₂/CO₂ molar ratio. Prior to reaction the catalysts were submitted to a mild reduction pretreatment (H₂ at 400 °C for 1 h). XRD analysis of the samples after pretreatment showed the presence of small Ni crystals (4-7 nm) on all the samples as well as of some unreduced NiO nanocrystals on the systems with high Zr content, in accordance with H₂-TPR experiments, which indicated that NiO reduction is promoted by CeO₂ but hindered by ZrO₂. The catalytic tests were performed at two different space velocities (72000 and 900000 cm³ h-1 g-1cat) on a series of Ni-based catalysts supported on CeO₂-ZrO₂ systems with different Ce/Zr ratios, including the two pure oxides. CO₂ conversion and selectivity to CH₄ (which was always close to 100 mol%) were constant throughout the 6-hour runs. CO₂ conversion resulted to increase with CeO₂ content in the catalyst, thus indicating the role of the CeO₂ component of the support in activating CO₂, whereas H₂ is activated on the Ni nanoparticles.

The combined influence of the catalyst acidity and porosity features on the transesterification of soybean oil with methanol was investigated over micro/mesoporous hierarchical Beta (Si/Al = 18 and 30), conventional microporous Beta (Si/Al = 23 and 43) and MCM-22 (Si/Al = 40) zeolites. All the catalysts were characterized as to their structure and texture by X-ray diffraction and N2 physisorption, respectively. Their acid features were assessed by adsorption microcalorimetry, using NH3 as probe molecule. Catalytic testing was carried out in batch at 453 K and 4 MPa. The nature of the organic material adsorbed/trapped in the catalyst during reaction (“coke”) was determined by GC/MS after solvent extraction. Fatty acid methyl esters (FAMEs) yields of 22–40 mol% were attained with a reaction time of 24 h over the conventional Beta and MCM-22 samples, whereas remarkably higher values (50–70 mol%) were observed over the hierarchical Beta zeolites. For both the hierarchical and conventional zeolites, the initial FAMEs yield was found to increase with the concentration of the acid sites able to adsorb ammonia with strength higher than ca. 100 kJ mol−1. In comparison with the conventional zeolites of similar acidity, the methyl esters yield over the hierarchical zeolites was twice to three times higher, as a consequence of the enhanced reactants diffusion in their secondary mesoporous system. The presence of free fatty acids in the reaction mixture and the nature of the coke revealed that several acid-catalyzed reactions and thermal degradation processes can occur simultaneously with transesterification. A general scheme for the different reaction pathways for the oil transformation was outlined.

A catalytic system where gold nanoparticles are dispersed on the surface of a conventional mesoporous silica was investigated. The sample (2.25wt% Au) was prepared by functionalizing the silica surface with 3-mercaptopropyltrimethoxysilane, anchoring gold from an HAuCl4 solution and then reducing it with sodium citrate. Prior to the catalytic runs, the Au/SiO2–SH system was submitted to different thermal treatments. The catalyst, either as-made or after each thermal treatment, was characterized by N2 adsorption–desorption at −196°C, CHS elemental analysis, solid state 29Si CPMAS NMR spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy of CO at −196°C. The bare and functionalized supports were also characterized. Large Au nanoparticles (ca. 30nm) form readily by adding the HAuCl4 solution to the functionalized support and, besides such particles, a second family of small ones originates upon thermal treatment (2–5nm, depending on the temperature and the atmosphere), leading to a bimodal gold particle size distribution. Remarkable CO conversion is obtained when the catalyst is calcined in air at 560°C and subsequently treated in H2/He at 600°C or directly treated in H2/He at 600°C. Based on the treatment-induced modifications in the physico-chemical properties of both the carrier and the supported phase, a reaction mechanism is outlined.

Obiettivo dell’attivita e stato quello di studiare, sintetizzare, caratterizzare e testare l’efficienza di materiali innovativi basati in particolare su nanocompositi da utilizzare nel sistema di desolforazione a caldo dell’H2S in alternativa sia all’uso di sorbenti tradizionali come ossido si zinco e carbone attivi, che ai processi per via umida, basati sull’impiego di ammine. Si e proceduto con un’estensiva analisi della letteratura e stato dell’arte con l’intento di fornire una panoramica sull’importanza dell’argomento in studio e dei sistemi attualmente utilizzati. E stata selezionata pertanto come fase attiva l’ossido di ferro, e come supporto sul quale confinarla, una silice mesostrutturata denominata SBA‐15. E stata inoltre condotta un’estesa caratterizzazione strutturale, morfologica e tessiturale del materiale prodotto attraverso diffrazione di raggi‐X, spettroscopia infrarossa, microscopia elettronica in trasmissione e fisisorbimento di azoto. Queste hanno rivelato che la tecnica di impregnazione impiegata ha permesso un’alta dispersione della fase attiva sul supporto e che la mesostruttura viene preservata insieme ad un’alta area superficiale. Le prestazioni desolforanti hanno messo in luce che la capacita di ritenzione dello zolfo e significativamente piu elevata se posta a confronto con l’ossido di zinco. Inoltre sulla base dei risultati maturati nella scorsa annualita si e optato per la preparazione di sistemi a base di ZnO su silice mesostrutturata sotto forma di pellet e di geometrie definite e dell’ordine dei 3‐8 mm. Tali sistemi compositi sono stati caratterizzati con le tecniche di caratterizzazione succitate. Uno studio preliminare sulla cattura di CO2 e stato condotto sintetizzando due sistemi di SBA‐15 modificata con diverse quantita di un funzionalizzante amminico. Tali sistemi sono stati caratterizzanti mediante diffrazione di raggi‐X e fisisorbimento di azoto e sottoposti a diversi cicli di adsorbimento/desorbimento di CO2. I risultati ottenuti mostrano che tali materiali sono promettenti in termini di capacita di adsorbimento e di rigenerabilita.

SBA-15 functionalization with mercaptopropyltrimethoxysilane has been used to prepare supported gold catalysts for the low temperature CO oxidation reaction. Supports and catalysts have been characterized by chemical analysis, CHS analysis, XRD, TGA, nitrogen adsorption-desorption at 77 K, TEM, CPMAS NMR, XPS and EPR. Catalytic runs have been carried out at atmospheric pressure and 313-623 K and the influence of diverse thermal treatments of the samples prior to reaction has been investigated. The presence of organic residues and the size of the gold nanoparticles strongly affect catalytic activity. Only high-temperature calcination in air followed by treatment under H-2 atmosphere leads to active catalysts. After complete elimination of the functionalizing agent, caused by the calcination step, a gold-mediated "activation'' process of the silica support takes place during the hydrogen treatment. As a consequence, active catalysts for the low temperature CO oxidation are obtained, even though the size of the Au particles is too large for establishing direct Au-oxygen interactions, usually assumed to be essential for the reaction over silica-supported gold catalysts.

The acidity of H-MCM-22 zeolite has been investigated by ammonia adsorption microcalorimetry and by IR spectroscopy of adsorbed nitriles (isobutyronitrile and pivalonitrile) and of aromatics (p-, o-, and m-xylene). The most abundant "zeolitic" OHs are exposed in the supercage system, absorbing predominantly at ca. 3618-3625 cm(-1). Less abundant are those exposed in the sinusoidal channel system, predominantly absorbing in the range 3600-3618 cm(-1). A third OH family, responsible for a weak band at 3575 cm(-1), is also observed. The adsorption of the hindered probe pivalonitrile strongly supports the conclusion that emisupercages are exposed at the 001 basal plane of the MCM-22 layered structure, where zeolitic OHs of the same nature of those exposed in the supercages indeed exist. At the external surface, weakly Bronsted acidic silanol groups (possibly two slightly different families) and strongly acidic Lewis sites are also well-evident. Monoaromatics, as well as para-disubstituted benzenes (such as p-xylene) and isopropyl-group containing molecules (such as isobutyronitrile), enter easily not only the emisupercages but also both internal channel systems of MCM-22. On the contrary, the entrance of tert-butyl-containing molecules, such as pivalonitrile, to the internal cavities is forbidden or at least strongly hindered. These data suggest that alkylation of benzene could occur both at the external emisupercages (with no diffusion limits) and in the internal cavities, without strong diffusion limits. The reactivity in the internal supercages could become significant above 200 degrees C when the selectivity to monoalkylation increases significantly. Alkylation of phenol with tert-butyl alcohol very likely occurs at the external surface catalyzed by Lewis acid sites.

The present work deals with the study of the liquid phase phenol alkylation by t-butanol over the three types of catalysts derived from MWW-precursor: MCM-22, MCM-36 and ITQ-2. It was assumed that by pillaring and/or delamination the contribution of acid sites located on the hemicages will increase and it could be evidenced during the alkylation of phenol by t-butanol, process involving large reaction intermediates and products which are difficult to be accommodated within sinusoidal channels. The reaction pathway involves many parallel and/or successive steps, the main reactions being O-alkylation and C-alkylation. The catalytic activity and selectivity of these materials are discussed. A general scheme of the process is proposed on the basis of the structural and acidic features of the catalysts.

MCM-22 zeolites with various Si/Al and/or Si/Fe ratios were synthesized and characterized by XRD, microcalorimetry and other techniques. The catalytic activity and selectivity of MCM-22 zeolites were investigated in the gas-phase oxidation of benzene with N2O at 673 K. The oxidation of benzene produces phenol as main product. The influence of the nature of catalysts (i.e., the content of iron, the nature of active sites) on catalytic activity of MCM-22 was investigated. In addition, some results about the nature of coke, which causes the Fe-MCM-22 deactivation, are exposed.

Marongiu, B., Monaci, R. and Porcedda, S., 1993. Excess Gibbs energies and excess enthalpies of liquid binary mixtures containing nitroalkanes. Fluid Phase Equilibria, 84:281-296.