Alessandra Palella

Hydrogen is the cleanest energy vector among any fuels, nevertheless, many aspects related to its distribution and storage still raise serious questions concerning costs, infrastructure and safety. On this account, the chemical storage of renewable-hydrogen by conversion into green-fuels, such as: methanol, via CO2 hydrogenation assumes a role of primary importance, also in the light of a cost-tobenefit analysis. Therefore, this paper investigates the effects of chemical composition on the structural properties, surface reactivity and catalytic pathway of ternary CuO-ZnO-CeO2 systems, shedding light on the structure-activity relationships. Thus, a series of CuZnCeO2 catalysts, at different CuO/CeO2 ratio (i.e. 0.2-1.2) were performed in the CO2 hydrogenation reactions at 20 bar and 200-300 °C, (GHSV of 4800 STP L∙kg∙cat-1∙h-1). Catalysts were characterized by several techniques including X-ray Diffraction (XRD), N2-physisorption, single-pulse N2O titrations, X-ray Photoelectron Spec...

Huge water consumptions and pollutants releases in the environment urge effective water decontamination technologies, fostering extensive recycle and reuse of industrial process-water and wastewater. The heterogeneous catalytic wet air oxidation (CWAO) offers a practical solution to the problem of decontamination of industrial effluents characterised by high concentration of toxic-refractory compounds, which are also detrimental for the active sludge of biological systems. Therefore, this work shows the superior CWAO performance of a new class of nanostructured MnCeOx catalysts toward the mineralization of some common toxic and refractory industrial pollutants. Mechanistic and kinetic evidences are summarised into a Langmuir-Hinshelwood reaction mechanism, leading to a formal kinetic model predicting the CWAO performance of nanostructured MnCeOx catalysts and optimum reaction conditions.

Abstract Methane is classified as one of the most dangerous air pollutant with a warming potential over 20 times higher than that of CO2. Then, methane abatement trough catalytic oxidation processes, especially using low-cost, noble-metal-free catalysts, falls in line with the most important challenges of environmental catalysis. Therefore, a series of MnCeOx composite materials, with different compositions (0.10

Abstract Nowadays, the practical exploitation of the sun for industrial purposes is still almost limited to the photovoltaic and the solar-thermal technologies. As an alternative route, the direct photoconversion of CO 2 to methanol is potentially one of the most promising ways for a larger utilization of the solar source. Since the late 1970s, many studies have been proposed for reproducing artificially the photosynthesis process, aiming to convert CO 2 into high value products. Indeed, the direct photoconversion of CO 2 is energetically more effective than catalytic hydrogenation processes, although the energy density and the efficiency of the current photocatalytic systems are still far away from large scale application. Thus, advances in the photocatalytic CO 2 conversion deserve systematic efforts in the fields of material science and reactor engineering. To overcome this technological gap, two feasible routes are pursued; these consist in the development of efficient photocatalytic materials at higher “quantum yield” for improving activity and selectivity, and the optimization of the photoreactor configuration enhancing the light transmission over the photocatalytic phase.

Abstract The hydrogen production from ethanol by conventional steam reforming, partial oxidation, and autothermal reforming processes is investigated. A comparable analysis of processes configuration, reforming reactors, and catalyst features is provided. The processes are analyzed from theoretical and practical point of view, outlining the process efficiency for distributed application. The role of the catalyst and the process conditions in determining the ethanol conversion and the hydrogen yield is also elucidated.

Abstract The techno-economic feasibility of three biogas utilization processes was assessed through computer simulations on commercial process simulator Aspen HYSYS: HPC (biogas to methanol), BioCH4 (biogas to biomethane) and CHP (biogas to heat & electricity). The last two processes are already used commercially with the aid of subsidy policies. The economic analysis indicates that, without these policies, none of these attain economic self-sustainability due to high overall manufacturing costs. The estimated minimum support cost (MSCs) were 108, 62 and 109 €/MWh for the HPC, BioCH4 and CHP processes, respectively. The model could explain currently practised government subsidies in Italy and Germany. It was seen that the newly proposed HPC process is economically comparable to the traditional CHP process. Therefore, the HPC process is a possible alternative to biogas usage. A support policy was proposed: 50, 66, 158 and 148 €/MWh for available heat, methane, electricity and methanol (respectively); the proposed energy policy results in a 10% OpEx rate of return for any of the processes, thus avoiding a disparity in the production of different products.

Abstract Bare and ceria-promoted MnOx catalysts (0 ≤ χMn≤1) were prepared by redox-precipitation reactions of Mn(VII), Mn(II) and Ce(III) or Ce(IV) precursors in slightly acidic (pH, 4.5) or basic (pH, 8.0) environment to assess genesis, nature, and functionality of surface active sites. Both synthesis protocols yield nanostructured materials with large surface area and exposure of Mn sites, featuring high activity in the CO oxidation and the phenol wet-air-oxidation (CWAO) model reactions (T, 423 K). High oxide dispersion prompts an extensive incorporation of Mn(II) ions into ceria substitutional solid-solution structures, forming oxygen-vacancies with stronger oxidation activity than surface Mn(IV) sites. Basic structure-activity relationships indicate that the superior CO oxidation performance of the pristine α-MnO2 system relies on large exposure of very reducible Mn(IV) active sites, while O2-adsorption onto Mn(II)/O-vacancy active centres generates very reactive surface oxygen-species boosting the efficiency of composite MnCeOx catalysts in the CWAO of phenol.

The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide content (rGO, 30 or 50 wt %) of the α-Fe2O3@rGO nanocomposites on their microstructural properties and electrochemical performance was investigated. Nanostructured composites were synthesized by a simple one-step solvothermal method and evaluated as anode materials for sodium ion batteries. The doping does not influence the crystalline phase and morphology of the iron oxide nanoparticles, but remarkably increases stability and Coulombic efficiency with respect to the anode based on the composite α-Fe2O3@rGO. For fixed rGO content, Ti-doping improves the rate capability at lower rates, whereas Mn-doping enhances the electrode stability at higher rates, retaining a specific capacity of 56 mAhg−1 at a rate of 2C. Nanocomposites with higher rGO content exhibit better electrochemical performance.

Abstract Current prospective in the liquid fuels synthesis is prefiguring a greater integration of eco-friendly technologies based on the use of “non-fossil” hydrogen and CO2. Therefore, a series of MOx@CeO2 catalysts (i.e. M = Cu, Fe and Zn), at different MO-to-CeO2 ratio (ca. 0.2–1.5 wt./wt.), were prepared and performed in the in the CO2 hydrogenation reactions at 20 bar and 200–300 °C, (GHSV; 4,400NL∙kg∙cat−1 h−1). Depending on catalyst composition, the CO2 conversion proceeds according to a “volcano shaped” profiles, resulting more effective at an optimal value of interfacial area (i.e. θ = 0.25). This also substantiate that the occurrence of structural-electronic synergistic effects plays a key role in the catalytic properties. The different catalytic pathway of CuZnO@CeO2 and CuFeZnO@CeO2 catalysts prove “dual-sites” and “triple-sites” mechanisms in the CO2 hydrogenation reactions, respectively.

Transition metal sulfide catalysts are actually the most performing catalytic materials in crude oil hydrotreating (HDT), for energetic purposes. However, these systems suffer from several drawbacks that limit their exploitation. Aiming to meet the even more stringent environmental requirement, through a remarkable improvement of HDT performance in the presence of refractory feedstock (i.e., in terms of activity, selectivity, and stability), a deeper knowledge of the structure–activity relationship of catalysts must be achieved. Therefore, in this study, CoMo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts were characterized and tested in the o-xylene hydrogenation model reaction, assessing the influence of both support acidity and catalyst acid strength on reaction pathway by employing γ-Al2O3 and Y-Type zeolite as acid reference materials. A clear relationship between concentration and strength of acid sites and the performance of the catalytic materials was established. Cobalt based catalyst ...

Abstract Direct photoconversion of CO2 from exhaust emissions into fuels and chemicals is one of the most ambitious challenges to a greater and more effective use of the solar source. Through an extensive and systematic evaluation of CO2 photoreduction process, both in aqueous media and in gas-vapour stream for over 120 h, this work addresses the role of the photoreactor configuration on the CO2 reduction efficiency, leading the study from laboratory to industrial environment, probably for the very first time. Therefore, the performance of a continuously stirred “semi-batch” (SB) photoreactor, a packed-bed (PB) photoreactor and a multi-tubular (MT) photoreactor has been compared in term of efficiency, products distribution and available energy. The results of the photocatalytic tests demonstrate a strong influence of process conditions on the photocatalyst performance and on the reaction path. The packed-bed (PB) configuration reports a maximum “apparent quantum efficiency” of about 6.0% and a net thermal energy of 0.3 kW h/m2 generated in 120 h.

The polluting level, the composition and the chemical structure of toxic heavy metals in spent zeolite from the fluid catalytic cracking (FCC) process of refinery, chosen as a model system of exhausted catalysts, have been evaluated through a novel characterization procedure, which combines different X-ray analysis techniques. The developed protocol of analysis has provided an effective tool for the definitive assessment of the level of toxicity and hazardousness of exhausted automotive catalysts, allowing their classification as reusable materials.

Abstract Pt/C and PtCu/C electrocatalysts with nominal Pt:Cu atomic ratios of 75:25, 50:50, and 25:75 were prepared using N2H4 as reducing agent and carbon black Vulcan XC-72R as support. The obtained materials were physically characterized by X-ray diffraction, Energy-Dispersive X-ray analysis, Transmission Electron Microscopy images, X-ray Photoelectron Spectroscopy (XPS), and Temperature-Programmed Reduction analysis. Cyclic voltammetry, linear sweep voltammetry, and chronoamperometry (TPR) measurements were carried out in a three-electrode glass cell to evaluate the electrochemical activity towards hydrazine electrooxidation in alkaline medium along with single-cell direct hydrazine fuel cell (DHFC) tests. The actual composition of the electrocatalysts evidenced a slightly lower Cu fraction compared to the nominal one. The X-ray diffractograms of the electrocatalysts showed the typical face-centered cubic structure of Pt alloys, with the highest fraction of Cu alloyed to Pt being achieved with the almost equiatomic catalyst. An important fraction of the remaining non-alloyed Cu is in the form of a copper oxide, as evidenced by XPS and TPR measurements. The electrochemical tests evidenced that the coexistence of part of the Cu alloyed with Pt and copper oxide achieved in the PtCu/C electrocatalysts enhances the performance compared to Pt/C. In particular, the optimum formulation is attained by the Pt53Cu47/C electrocatalyst, allowing maximization of the electrocatalytic activity towards hydrazine electrooxidation and the single-cell performance at 60 and 80 °C.

Abstract The effects of cerium addition on the physico-chemical properties and CO oxidation activity of nanostructured MnCeO x catalysts (0 ≤ c Ce  ≤ 1) have been assessed. Irrespective of the loading, cerium hinders any significant long-range crystalline order promoting surface exposure, oxide dispersion, and reducibility of composite catalysts. Noticeable structural effects and strong oxide interaction lead to different arrangement of the active MnO x phase, explaining the peculiar reactivity scale of the studied catalysts in the CO oxidation reaction. High activity, good stability, CO 2 productivity values depending on the MnO x loading, and similar activation energy values in the range of 353–533K (37–47 kJ/mol) uncover an unchanging reaction mechanism, irrespective of composition and temperature. Although some chemical effects at high Ce loading (χ Ce  ≥ 0.5), structure-activity relationships indicate that surface Mn IV centers are the active sites of bulk MnO x and composite MnCeO x catalysts.

Abstract The electrocatalytic reduction of CO 2 to alcohols was investigated in a co-electrolysis cell based on a solid polymer electrolyte. PtRu/C and Ru/C catalysts were used in gas diffusion cathodes for the reduction of humidified CO 2 . An IrRuO x catalyst was used for the oxygen evolution from liquid water at the anode. This electrochemical reactor employed a perfluorosulfonic acid membrane electrolyte separator (Nafion ® ) and it was operated in a temperature range from 30 °C to 95 °C. The cathode catalysts were characterized by well-dispersed metal nanoparticles (2 nm mean particle size) on a carbon black support. Electrochemical polarization tests were carried out in the presence of CO 2 or with humidified inert gas for comparison. The results evidenced that direct CO 2 reaction on the catalysts surface was essentially occurring at low cell voltages ( 2 conversion.

Abstract Crude pyrolysis bio-oil can be used as energy vector, but further upgrading is required before its utilization as transportation fuel and alternative hydrogen source. Therefore, the catalytic hydrogenation process of several model compounds (i.e. ether, alcohol, acid, olefin and guaiacol) and of crude bio-oil obtained by fast pyrolysis of nuts waste biomass has been investigated using CoMo/Al 2 O 3 catalysts, pre -sulfided in flowing H 2 S at 400 °C, with different textural properties under simulated industrial conditions (T, 250–300 °C; P, 10–20 bar). Depending on the chemical structure of the various compounds, a complex reaction network, involving mostly hydro-deoxygenation (HDO), hydrogenation (HYD) and hydrocracking (HCR) processes, occurs. The simultaneous proceeding of all these reactions during the hydrotreating (HDT) of the crude bio-oil implies the formation of a wide range of hydrocarbon compounds documenting the feasibility of the upgrading process to obtain liquid transportation fuels and hydrogen-source compounds. A scale of reactivity based on the effectiveness of hydrogenation of compounds and functional groups has been proposed, also providing evidence of the effects of the texture and physico-chemical properties on the activity and selectivity of the CoMo sulfided catalysts in the HDT processes.