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Transition metal oxides on reduced graphene oxide (TMO@rGO) nanocomposites were successfully prepared via a very simple one-step solvothermal process, involving the simultaneous (thermal) reduction of graphene oxide to graphene and the deposition of TMO nanoparticles over its surface. Texture and morphology, microstructure, and chemical and surface compositions of the nanocomposites were investigated via scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results prove that Fe2O3@rGO, CoFe2O4@rGO, and CoO@rGO are obtained by using Fe and/or Co acetates as oxide precursors, with the TMO nanoparticles uniformly anchored onto the surface of graphene sheets. The electrochemical performance of the most promising nanocomposite was evaluated as anode material for sodium ion batteries. The preliminary results of galvanostatic cycling prove that Fe2O3@rGO nanocomposite exhibits better rate capability and stability than both bare Fe2O3 and Fe2O3+rGO physical mixture.

Supported Pd/Ir bimetallic catalysts were synthesized by the “water-in-oil” microemulsion method at different precursor concentrations and characterized by XRD, XPS, SEM, TEM, and cyclic voltammetry. Depending on the preparation conditions, formation of bimetallic catalysts with different metal segregation and surface composition can be easily obtained, thus tuning the bimetallic structure of catalysts as well as their relative catalytic properties. Bimetallic Pd/Ir systems were efficiently tested in the hydrogenation of cinnamaldehyde showing a better performance than analogous monometallic catalysts.

The hydrogenolysis reaction of aromatic alcohols (benzyl alcohol, 1-phenylethanol and diphenylmethanol), promoted by supported palladium catalysts, such as Pd/TiO2, Pd/SiO2 and Pd/Co3O4, has been investigated at 0.1 MPa H2 and 323 K. The catalysts have been characterized by BET, TPR, XRD, TEM and XPS. A different kinetic behaviour was observed: in presence of Pd/TiO2 and Pd/SiO2 catalysts, prepared by impregnation, the hydrogenolysis activity follows the order benzyl alcohol > 1-phenylethanol ≥ diphenylmethanol, whereas it is totally reversed on Pd/Co3O4, prepared by co-precipitation. All results indicate that the reactivity of supported Pd catalysts, in the hydrogenolysis reaction, depends on the support nature, the preparation method of catalysts and the aromatic alcohols structure. Kinetic experiments carried out at different partial hydrogen pressure allow to elucidate the pathway of the C–OH bond scission, involving a radical substitution of the carbon bonded OH group by a hydrogen atom coming from the metal surface “via” associative and dissociative paths.

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 N2) 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.

a b s t r a c t A catalyst, Pd/B(OH)3, based on the cheap and environmentally friendly support, was synthesized by using the impregnation method with the aim of investigating the Lewis acid effect on hydrogenation and hydrogenolysis reactions. The sample was reduced at 353 K under hydrogen flowing and characterized by various physico-chemical techniques, such as BET, TPR, XRD, TEM, FESEM and XPS. Its catalytic performance, in hydrogenation reactions of carbonyls and hydrogenolysis of aromatic alcohols, carried out at 0.1 MPa H2 pressure and 323 K, was investigated. It was demonstrated that Pd/B(OH)3 is active using cyclohexane as solvent and the reactivity depends on the steric hindrance of the substrate. Conversely, in ethanol, boric acid dissolves and does not influence catalytic reactions.

Hematite/reduced graphene oxide (Fe2O3/rGO) nanocomposite was successfully fabricated via a facile solvothermal reaction of iron precursor solution and GO leading to simultaneous deposition of iron oxide nanoparticles and in situ reduction of GO without any reducing agent. Texture and morphology, microstructure, chemical and surface composition of the nanocomposite were investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, thermo-gravimetric analysis and X-ray photoelectron spectroscopy, respectively. Its electrochemical performance as anode material for sodium ion batteries was preliminarily evaluated via galvanostatic cycling. The results prove that the Fe2O3 nanoparticles are uniformly anchored onto the surface of graphene nanosheets and that the Fe2O3/rGO nanocomposite shows interestingly higher specific capacities compared to the bare Fe2O3

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.

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.

Silica supported Group VIII metal catalysts (Pd, Pt, Ru, Rh and Ir) have been tested at 303 K in liquid-phase reaction of cis-2-butene-1,4-diol with hydrogen at atmospheric pressure. The catalysts have been characterized by TPR, XRD and TEM. The catalytic activity changes in the order: Pd ≫ Rh > Pt > Ru > Ir. Significant differences were observed in products distribution. Ir/SiO2 and Pt/SiO2 favour the hydrogenation reaction to butane-1,4-diol, whereas Rh/SiO2, Pd/SiO2 and Ru/SiO2 significantly promote double bond and geometric isomerization processes, leading to 2-hydroxytetrahydrofuran and trans-2-butene-1,4-diol, respectively. Formation of products, deriving from isomerization and hydrogenation reactions, is explained on the basis of a mechanism involving a common σ-alkyl metal bonded intermediate and the variation in products distribution among the various metals is rationalized taking into account electronic factors.

The gas-phase interaction of cis-2-butene-1,4-diol (C-2-OL) with silica supported Pd and Pt nanoparticles has been studied using infrared spectroscopy at room temperature. Samples were prepared according to standard recipes and characterized through TEM and the IR spectroscopy of adsorbed carbon monoxide at room temperature. Whereas the reaction with hydrogen of C-2-OL in ethanol solutions yields hydrogenated products through a complex network, and no reaction takes place in the absence of hydrogen, in the present case C-2-OL is converted first to 2,5-dihydrofuran (2,5-DHF) and water. This step occurs on the silica support at room temperature, probably through the intermediacy of the surface species –Si–O–CH2–CH CH–CH2–OH. The presence of Pd nanoparticles allows, at ca. 100 °C, the subsequent isomerization of 2,5-DHF to 2,3-dihydrofuran (2,3-DHF). The same reaction requires a higher temperature (ca. 150 °C) with the Pt catalyst. At higher temperatures, the expected dehydrogenation of both 2,5- and 2,3-DHFs to furan takes place. On the support alone at 350 °C 2,5-DHF is converted to furan, and 2,3-DHF to carbonyl-containing species (as suggested in the literature), through thermal reactions.

The catalytic reduction of aliphatic aldehydes (propanal, pentanal and hexanal) and ketones (pentan-2-one, pentan-3-one and cyclohexanone) to the corresponding alcohols promoted by palladium catalysts, such as Pd/CoO, Pd/NiO, Pd/ZnO, Pd/Fe 2 O 3 and Pd/CeO 2 , was performed under mild conditions (0.1 MPa H 2 and 323 K) for the first time. All the catalysts were obtained by the co-precipitation technique and characterized by BET, TPR, XRD, TEM and XPS. The co-precipitation method allows, after reduction, formation of bimetallic ensembles (Pd/CoO and Pd/ZnO in less extent) or alloys (Pd/NiO) thus changing the electronic properties of the palladium on the surface, increasing the d-orbital energy at the Fermi level and permitting the activation of the C O bond also in aliphatic carbonyls. Accordingly the reactivity of Pd/Fe 2 O 3 and Pd/CeO 2 towards aliphatic aldehydes is attributed to a redox interaction of Fe 3+ or Ce 4+ with the oxygen moiety of the carbonyl bond, leading to the π* orbital energy decrease. Analogous reactions, carried out with Pd/CoO and Pd/Fe 2 O 3 , prepared by impregnation, gave a very slow reduction. Additional catalytic tests were performed with aromatic carbonylic compounds in order to compare their reactivity with that of aliphatic systems: the differences were interpreted taking into account the Δ energy value between π and π* orbitals, much lower in aromatic carbonyls, that favours an easier activation of the aromatic C O bond.

The effect of K, Ca and Ba metals addition on the catalytic properties of SiO2 supported ruthenium catalysts in the selective liquid phase conversion of cis-2-butene-1,4-diol affording, when hydrogenated, 2-hydroxytetrahydrofuran has been investigated. Catalysts containing 5 wt% Ru and promoted with a different amount of selected first and second group metals salts have been prepared and characterized by TPR, XRD, TEM, FT-IR of adsorbed pyridine and CO. It has been found that promoters modify the microstructural and electronic properties of Ru particles compared with those of the undoped Ru/SiO2 sample, depending on the metal nature and loading. Consequently, the catalytic activity and selectivity towards reaction products, in cis-2-butene-1,4-diol hydrogenation, is strongly affected by the presence of promoters. In particular, K-promoted systems give an excellent selectivity to 2-hydroxytetrahydrofuran but a poor activity; whereas group IIA metals salts addition leads to an enhancement of activity and a slight increase of selectivity to the desired product with respect to the bare Ru sample. The promoted Ru catalysts behaviour is discussed in terms of charge/ionic radius ratio effect of doping cations. Finally, the salient result is the maximum yield to 2-hydroxytetrahydrofuran of 80%, so far obtained, over the sample promoted with the highest potassium loading and mainly attributed to kinetic factors.

Bifunctional Pt–Sn/SiO 2 catalysts described in the Part I, prepared by co-impregnation varying the Pt and Sn loading and the Sn/Pt ratio, have been tested in the one-pot synthesis of α-campholenic alcohol (naturanol) from α-pinene oxide. The process involves the sequential isomerization of the substrate into α-campholenic aldehyde and the subsequent hydrogenation of this intermediate to naturanol. In this Part II, a kinetic investigation of the catalytic process is reported. First, the isomerization and hydrogenation steps were studied separately. Results obtained indicate that the role of tin in the Pt–Sn/SiO 2 catalysts formulation is crucial, affecting strongly the activity and/or selectivity in both steps. In the isomerization step, the catalytic activity increases linearly with tin loading whereas the selectivity to campholenic aldehyde remains essentially unchanged. In the second step, high tin loadings increase the selectivity to naturanol but a careful control on the Sn/Pt ratio is necessary to obtain a satisfactory hydrogenation rate, because for Sn/Pt > 1 the catalytic activity falls out dramatically. The overall transformation of α-pinene oxide into naturanol was then investigated. It was found that the isomerization of α-pinene oxide to campholenic aldehyde is the step limiting the naturanol yield. Moreover, kinetic tests have shown that the ratio between the isomerization and hydrogenation rate is the other critical factor in order to synthesize naturanol in high yield. Optimizing the formulation of the Pt–Sn/SiO 2 catalysts, a maximum naturanol yield of about 60% was obtained.

Bifunctional Pt-Sn/SiO2 catalysts with different Sn/Pt ratios have been prepared by co-impregnation, reduced in H2 and tested by means of the one-pot synthesis of α-campholenic alcohol (naturanol) from α-pinene oxide. All results are reported in two sections. In Part I, here presented, characterization of catalysts in terms of microstructure chemical and surface properties by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and acid properties investigated by FT-IR of adsorbed pyridine are included. In the reduced Pt-Sn/SiO2 catalysts, oxidized and/or metallic species, having different microstructural and acid characteristics, strongly dependent on the Sn/Pt ratio have been identified. For Sn/Pt ratios A clear relationship between the intensity of FT-IR bands and the activity in α-pinene oxide isomerization was observed indicating that Lewis acid sites, associated with ionic tin species, present on the surface of bifunctional Pt-Sn/SiO2 catalysts, are active centres favouring the isomerization reaction. Sn addition also increases the selectivity to naturanol, in the subsequent consecutive hydrogenation of campholenic aldehyde intermediate. However, at high loading, the bifunctional effect is less significant because the excess of oxidized tin strongly decreases the catalytic activity. Our results indicate that the Sn/Pt ratio is the key factor in Pt-Sn/SiO2 bifunctional catalysts and influences both activity and selectivity in the one-pot synthesis of naturanol from α-pinene oxide.

Palladium catalysts on different supports (SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , MgO and ZnO) have been tested in selective liquid phase conversion of cis -2-butene-1,4-diol affording also, when hydrogenated, 2-hydroxytetrahydrofuran. The metal particle size was determined by TEM. The acidic properties of the catalysts were studied by FT-IR spectroscopy using pyridine as probe molecule. The influence of some preparative variables, such as the particle size, the support, the partial hydrogen pressure, on the catalytic behaviour of palladium catalysts has been investigated. TEM measurements indicated that Pd particles diameter observed was in the range 2.5–10 nm. No significant variation of TOF and selectivity values with the metal particle size was observed in this range. Moreover, the activity and the selectivity towards reaction products were found to be strongly dependent on the acid–base characteristics of the support. The acid systems have been found more active and selective to isomerisation and hydrogenolysis products than the basic ones. No hydrogenolysis reaction was observed on basic supports. Among the examined catalysts, Pd/TiO 2 resulted the most selective to 2-hydroxytetrahydrofuran. A maximum yield to this compound of about 74% was, in fact, obtained at 0.01 MPa of H 2 pressure.

Lewis acids (FeCl 3 , ZnCl 2 , H 3 BO 3 ) supported on SiO 2 and TiO 2 nanoparticles have been tested in the selective isomerization of α-pinene oxide to campholenic aldehyde. The spherical nanoparticle supports with a narrow particles size distribution have been synthesized by the sol–gel method. The morphological and microstructural characterization of the supports and catalysts was carried out by XRD, SEM–EDX and BET surface area measurements. Acid properties were investigated by DTA and FT-IR after adsorption of triethylamine and pyridine as probe molecules. SiO 2 and TiO 2 nanoparticles used as supports have shown negligible acidity and consequently low activity in the isomerization of α-pinene oxide. After Lewis acid promoters addition, the activity was markedly enhanced with a high selectivity to campholenic aldehyde. Lewis acids supported on titania have been found more actives than analogous supported silica catalysts due to the higher surface area of the TiO 2 support. The selectivity instead was found to be independent on the support used. Among the investigated samples, Zn-doped catalysts resulted the most selective. On the basis of FT-IR of adsorbed pyridine, the selectivity to campholenic aldehyde on these catalysts has been correlated to the strength of the Lewis acid sites. Optimising the preparation of the catalysts and reaction conditions, a maximum yield to campholenic aldehyde of 74% was obtained.

The liquid phase hydrogenation of cis -2-butene-1,4-diol has been studied in ethanol, using different platinum-supported catalysts, at a temperature ranging from 273 to 303 K and at a partial H 2 pressure between 0.01 and 0.1 MPa. Formation of only hydrogenation and hydrogenolysis products was detected and their selectivity was found to depend on the acid–base characteristics of the support. A yield of 96% to the fully hydrogenated product, butane-1,4-diol, at 303 K and 0.1 MPa H 2 pressure was obtained on Pt/MgO. The experimental data, in presence of platinum supported on TiO 2 , was explained on the basis of a two paths mechanism: one leading to butane-1,4-diol, as usually, through a σ-alkyl species and the other, affording cis -crotyl alcohol and 3-buten-1-ol, involving the same unique intermediate, η 3 -allyl. Reaction rates were described on the basis of a Langmuir–Hinshelwood type model, assuming a non-competitive adsorption of organic species and hydrogen on the platinum active sites. Kinetic parameters for individual reaction steps were determined by a non-linear regression analysis. Furthermore, an adsorption of the olefinic substrate in a tilted mode was discussed in order to explain the hydrogenolysis reaction.

Homogeneous hydrogenation and isomerization reaction of cis -2-butene-1,4-diol has been investigated in ethanol by using tris(triphenylphosphine)chlororhodium(I), RhCl(PPh 3 ) 3 , and triethylamine at 303 K and 0.01–0.1 MPa partial hydrogen pressure. Under reduced H 2 pressure, the geometric isomerization reaction occurs, to a high extent, leading to trans -2-butene-1,4-diol up to 93% selectivity at 90% conversion of the cis analogous. Effects of H 2 partial pressure as well as triethylamine, added phosphine and olefin concentrations on the rate of reaction and on the products distribution were also investigated. The results obtained can be interpreted on the basis of a proposed mechanism in which RhH(PPh 3 ) 3 is the active species. The high selectivity towards cis - trans isomerization of cis -2-butene-1,4-diol is attributed to steric factors of the Rh(I) coordinated triphenylphosphine groups.

Liquid phase hydrogenation and isomerization of some α,β-unsaturated primary and secondary alcohols have been investigated in tetrahydrofuran over a 2.5% TiO 2 supported palladium catalyst at 303 K and 0.01 MPa partial hydrogen pressure. The double bond isomerization reaction of these substrates leads also to formation of the corresponding saturated aldehydes or ketones. Catalytic activity and selectivity were found to depend strongly on the steric and electronic effects of the substituents on the double bond of the alcohol. The less crowded is the olefinic bond of the unsaturated alcohol, the higher is the activity. Formation of two σ-alkyl palladium bonded intermediates was postulated to explain the different selectivity towards hydrogenated and isomerized products observed for α,β-unsaturated alcohols used. 2-Propen-1-ol exhibited the highest activity and selectivity for double bond migration leading to propanal up to 80% yield.

The liquid phase hydrogenation of cis-2-butene-1,4-diol over a supported palladium catalyst has been investigated in ethanol at 0.01≤PH2≤0.5 MPa and 273≤T≤303 K. The effect of substrate concentration, catalyst amount, agitation speed and H2 pressure on the reaction rate has also been studied under isothermal conditions. Under reduced H2 pressure, double bond isomerization reaction occurs to a high extent leading to 2-hydroxytetrahydrofuran up to 60% yield. Formation of all reaction products was explained on the basis of a reaction model in which a surface σ-alkyl derivative was postulated and the results were clarified on applying the steady-state approximation to this intermediate. Kinetic rate equations were derived following the Langmuir–Hinshelwood model by assuming a non-competitive adsorption of organic species and hydrogen on the palladium active sites. Rate constants and the adsorption constant for each reaction were determined by a non-linear regression analysis. An excellent agreement between the predicted concentrations versus time profiles and the experimental data was observed. Furthermore, the model predictions of hydrogenated and isomerized compounds formation at different pressures agree well with the experimental results obtained.

Hydrogenation of 2-butyne-1,4-diol has been investigated over palladium supported catalysts. It was found that, besides butane-1,4-diol, side products such as cis- and trans-2-butene-1,4-diol, 2-hydroxytetrahydrofuran, cis- and trans-crotyl alcohol and n-butanol were also formed. The hydrogenation of the intermediates cis- and trans-2-butene-1,4-diol has been investigated too. On the basis of the results reported, a reaction scheme for the hydrogenation of 2-butyne-1,4-diol is proposed. The influence of proton, nature of solvent and carbon support on activity and products distribution has been studied in the hydrogenation of cis-2-butene-1,4-diol. The use of water as solvent shows a better activity and selectivity to butane-1,4-diol and suppresses the hydrogenolysis reaction more than other solvents used. Addition of proton leads to a major formation of hydrogenolysis and isomerisation products. A higher activity and selectivity to isomerisation products were obtained on the palladium catalysts supported on acid modified carbon.

A microstructural characterization by XRD, FT-IR and temperature programmed reduction (TPR) of unsupported FeV and K-FeV catalysts, prepared by solid-state synthesis, is reported. The formation of FexVyOz mixed phases of different compositions has been evidenced depending on the V/Fe ratio and calcination temperature. The catalytic activity of the samples in the combustion of diesel soot has been investigated with the aim to understand the role of FexVyOz mixed phases in the title reaction.

Vanadium oxide-based catalysts promoted with KCl and a transition metal chloride (M=Cu, Ce, Fe, Co, Zn) have been investigated in the oxidation of diesel soot and characterized by thermal analysis techniques, such as temperature-programmed reduction (TPR) and differential scanning calorimetry (DSC). Aim of the study was to acquire information on the reaction mechanism of the catalytic soot combustion over these catalytic systems. Data presented suggest that the activity of investigated catalysts is correlated to their reducibility which favor the redox activity of the active vanadium species. The formation of eutectics between components of the catalyst also occur improving the catalyst–carbon contact.

The liquid phase hydrogenation of 2,4-dinitrotoluene (2,4-DNT) to 2,4-diaminotoluene (2,4-DAT) has been studied over palladium supported on carbon. Catalytic activity and selectivity to the intermediate products were found to depend on the metal particle size. The larger metal particles were the most active and selective towards the formation of the 2,4-nitrohydroxyaminotoluene isomers. The catalysts have been characterized by TPR, XRD, TEM and CO chemisorption. TPR analysis has shown that no formation of a palladium β-hydride phase occurs on these systems irrespectively of the metal particle size. This apparently anomalous behavior has been attributed to the contamination of the Pd metal particles by impurities and/or C atoms migrating from the support. On the basis of the reported results the relationships between the catalytic activity and the metal particle size in the hydrogenation of 2,4-DNT is discussed.

The activity of different metal oxides in the catalytic combustion of a diesel soot having a high amount of adsorbed hydrocarbons has been investigated and tested in a TPO apparatus. Two different steps have been observed. The first is related to the combustion of hydrocarbons adsorbed on soot and the second one to the combustion of the graphitic solid fraction. A high surface area Fe2O3 was found to be the most active catalyst for the oxidation of hydrocarbons, whereas V2O5 was also able to promote the combustion of graphitic carbon. The oxidation of the hydrocarbon fraction has been correlated with the surface area and the strength of the metal-oxygen bond of the metal oxide. The combustion of graphitic carbon is favoured instead on metal oxides having a low melting point. The effect of platinum addition to γ-alumina has been also investigated. Spillover of activated oxygen from Pt to the support has been postulated to take into account the promotion of the oxidation of graphitic carbon.

The catalytic hydrogenation of 2,4-DNT over palladium supported on carbon catalysts is reported. The 2-(hydroxyamino)-4-nitrotoluene (2HA4NT) was identified as a reaction intermediate. The characterization of this compound and the reasons for its formation are discussed.

Hydrogenation of benzene to cyclohexene has been studied over Ru/Al 2 O 3 catalysts in the presence of water. Attention has been paid to the influence of reaction conditions, ruthenium precursors, and catalyst pretreatment. The reaction was carried out under kinetic control and under strong mass transfer limitation. In the presence of water the formation of cyclohexene cannot be simply ascribed to physical effects. Mass transfer limitations are, however, important to obtain high selectivities at high conversion. A pretreatment of the catalyst under hydrogen, in the absence of benzene, increases the selectivity to cyclohexene. No effect has been observed when the pretreatment is carried out under nitrogen. Catalysts prepared from RuCl 3 are more selective with respect to samples prepared from chlorine-free precursors.

The kinetics of liquid phase hydrogenation of 2,4-dinitrotoluene (2,4-DNT) to 2,4-diaminotoluene (2,4-DAT) were studied in ethanol with a 5% Pd/C catalyst using a slurry reactor, in the temperature range between 278 and 323 K and at a pressure of 0.1 MPa. the reaction pathway has been described by a Langmuir-Hinshelwood model with a noncompetitive adsorption of the organic species and hydrogen on the active sites. Different reaction mechanisms have been tested. The best fitting of the experimental data was obtained with a reaction mechanism involving three parallel routes leading from 2,4-DNT to 4-(hydroxyamino)-2-nitrotoluene (4HA2NT), 4-amino-2-nitrotoluene (4A2NT), and 2-amino-4-nitrotoluene (2A4NT) which are then hydrogenated to 2,4-DAT through a series of consecutive reactions. The rate constants and activation energy for each reaction step have been reported.

The activity of different metal oxides in the catalytic combustion of a diesel soot having a high amount of adsorbed hydrocarbons has been investigated and tested in a TPO apparatus. Two different steps have been observed. The first is related to the combustion of hydrocarbons adsorbed on soot and the second one to the combustion of the graphitic solid fraction. A high surface area Fe2O3 was found to be the most active catalyst for the oxidation of hydrocarbons, whereas V2O5 was also able to promote the combustion of graphitic carbon. The oxidation of the hydrocarbon fraction has been correlated with the surface area and the strength of the metal-oxygen bond of the metal oxide. The combustion of graphitic carbon is favoured instead on metal oxides having a low melting point. The effect of platinum addition to γ-alumina has been also investigated. Spillover of activated oxygen from Pt to the support has been postulated to take into account the promotion of the oxidation of graphitic carbon.

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.

The selective catalytic reduction of the unsaturated campholenic aldehyde to the corresponding unsaturated alcohol, naturanol, was investigated over 2 wt.% Pd supported on different metal oxides (MeO x = SiO 2 , TiO 2 , ZnO, Fe 2 O 3 , NiO, Co 3 O 4 ). Pd/MeO x catalysts have been prepared by impregnation (series I) and coprecipitation (series CP) and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and temperature programmed reduction (TPR). Results obtained in the hydrogenation of campholenic aldehyde have shown that the activity and products distribution depend both on the nature of the support and the preparation method. Regarding the catalysts of series I, palladium supported on SiO 2 and TiO 2 resulted totally unselective towards formation of naturanol, but, when Pd was supported on reducible metal oxides (ZnO, Fe 2 O 3 , NiO, and Co 3 O 4 ), the selectivity to naturanol strongly increases. Higher selectivity values to naturanol have been obtained on catalysts of the CP series. Among these latter, the Pd/Co 3 O 4 catalyst resulted the most selective, with a yield to the unsaturated alcohol > 85%. On the basis of characterization and kinetic data, the role of the support and of the preparation method in the catalytic behaviour of Pd catalysts for the selective reduction of the carbonyl group is discussed.

Selective catalytic reduction of campholenic aldehyde to naturanol was investigated over Sn-and Fe-doped SiO2, and Fe2O3-supported Pd catalysts. On Pd/SiO2 and Pd-Sn/SiO2 only saturated campholenic aldehyde is formed. Addition of Fe increases the C=O hydrogenation rate producing the corresponding unsaturated alcohol with a good selectivity. Also Fe2O3-supported catalysts were found to be more selective towards carbonyl hydrogenation. Addition of tin to Pd/Fe2O3 contributes to a further selectivity enhancement towards naturanol.

Pd/C catalysts doped with Fe, Sn and Ca for the selective hydrogenation of 2,4-dinitrotoluene (2,4-DNT) have been characterized by CO chemisorption, X-ray diffraction (XRD) and electron microscopy techniques (TEM-EDX). The promoters modify the microstructural and chemisorption properties of the noble metal particles with respect the undoped-Pd/C catalyst depending on the promoter nature and loading. Particles smaller than those observed on the monometallic catalysts were detected on Fe- and Sn-doped catalysts whereas larger particles were observed on the Ca-promoted samples. The promoters are located on the palladium particles, covering them and/or forming alloys with palladium. The role of the promoters in the selective hydrogenation of 2,4-DNT is discussed on the basis of the characterization results.

An improved HPLC method was developed for the separation and quantification of 2,4-dinitrotoluene and its reduction products. Gradient elution, with a water–acetonitrile mobile phase, was selected for the separation of all components including the 2,4-nitrohydroxyaminotoluene isomers. Provisional identification of the isomer intermediates has been obtained by their UV–Vis spectra.

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.

Hydrogenation of 2,4-dinitrotoluene (DNT) to 2,4-diaminotoluene (DAT) has been carried out over a 5% Pd/C catalyst. Gas chromatography and liquid chromatography have been used to detect the reaction intermediates. 4-Hydroxylamine,2-nitrotoluene (4HA2NT) is the main reaction intermediate. The two amino-nitro compounds 4-amino,2-nitrotoluene (4A2NT) and 2-amino,4-nitrotoluene (2A4NT) are the other relevant intermediates found. 4HA2NT decomposes by exposure to air and in the GC injector thus complicating the analysis of the reaction mixture. A simple procedure has been developed to perform the GC analysis without interference of the hydroxylamine. A kinetic study has been also carried out and a reaction pathway has been proposed. Intermediates are formed from DNT through three parallel reactions. They are then hydrogenated to the final product DAT by a series of consecutive reactions.