Potential of Ceria-Zirconia-Based Materials in Carbon Soot Oxidation for Gasoline Particulate Filters

ZrO(2)and Ce(0.8)Zr(0.2)O(2)mixed oxides were prepared and tested in the oxidation of carbon soot at different oxygen partial pressures and degrees of catalyst/soot contact to investigate their activity under typical gasoline direct injection (GDI) operating conditions. Under reductive atmospheres, generation of oxygen vacancies occurs in Ce0.8Zr0.2O2, while no reduction is observed on ZrO2. Both materials can oxidize carbon under high oxygen partial pressures; however, at low oxygen partial pressures, the presence of carbon can contribute to the reduction of the catalyst and formation of oxygen vacancies, which can then be used for soot oxidation, increasing the overall performance. This mechanism is more efficient in Ce(0.8)Zr(0.2)O(2)than ZrO2, and depends heavily on the interaction and the degree of contact between soot and catalyst. Thus, the ability to form oxygen vacancies at lower temperatures is particularly helpful to oxidize soot at low oxygen partial pressures, and with higher CO(2)selectivity under conditions typically found in GDI engine exhaust gases

Pincer and Carbonyl Ruthenium Complexes for Transfer Hydrogenation Reactions

The transfer hydrogenation (TH) catalyzed by ruthenium complexes is a cost-effective and environmentally benign way for the reduction of carbonyl compounds. On account of the reversibility of the TH process, ruthenium catalysts have attracted a great deal of interest for a number of C-H activation organic transformations. To improve the catalytic activity and to retard decomposition, the design of suitable chelating and non-innocent ligands appears crucial. We report here the preparation of pincer, carbonyl and acetate ruthenium complexes, displaying high productivity for the TH of carbonyl compounds, including flavanones and biomass-derived molecules (5-HMF, ethyl levulinate). The alkylation of amines with alcohols and the preliminary results on the photochemical TH of carbonyl compounds are also presented

Sustainable solvent-free selective oxidation of benzyl alcohol using Ru(0) supported on alumina

The selective oxidation of primary alcohols into their corresponding carbonyl compounds is challenging because of the easy over oxidization to acids and esters. The traditional reaction requires large amounts of solvent and oxidant, causing serious environmental issues. Recently, several efforts have been made to transform the reaction into a more sustainable process. Here, we investigated the solvent-free oxidation of benzyl alcohol using air as a green oxidant in the presence of ruthenium supported on alumina and zirconia, thereby meeting atom economy and environmental requirements. The materials were extensively characterized and, in addition to their activity, selectivity, and reusability, the environmental sustainability of the process was assessed according to green chemistry metrics. XRD, TEM, and XPS analyses suggest that the formation of metallic Ru on the support plays a key role in the catalytic activity. Ru supported on alumina, after a reduction treatment, achieves good activity (62% conversion) and a complete selectivity in a very sustainable process (without a solvent and with air as oxidant), as indicated by the very low E-factor value. The formulation is very stable and maintains high activity after recycling.Peer ReviewedPostprint (published version

Insights on the Interfacial Processes Involved in the Mechanical and Redox Stability of the BaCe0.65Zr0.20Y0.15O3−δ–Ce0.85Gd0.15O2−δ Composite

Ceramic fuel cells and H2 permeation membranes are key technologies to accelerate the transition from a carbon economy based on fossil fuels to a H2 economy based on the use of renewable resources. The competitiveness of these technologies in the market depends on the identification and optimization of stable and effective low-cost materials. Perovskite-fluorite ceria-based composites show suitable properties, and studies on the mechanism that rules their mechanical, thermal, and redox stability are crucial for further technological advances. This study focuses on the redox behavior of BaCe0.65Zr0.20Y0.15O3-?-Ce0.85Gd0.15O2-? (BCZY-GDC) dual-phase ceramic. Temperature-programmed reduction, thermogravimetry, temperature-dependent X-ray diffraction, and Raman analyses are used to understand the dynamics of the interaction between the ceramic oxide components. It is shown how the simultaneous occurrence of structural changes in BCZY and GDC reduction helps in decreasing the mechanical stresses induced by temperature and by the reducing atmosphere. The interfacial processes between the single GDC and BCZY oxides contribute to limit reduction of GDC in the composite, which allows complete reversibility of the redox process investigated in this study. Thus, it is suggested that the redox behavior of this class of materials may be a descriptor of their mechanical and thermal stability

Abatement of the ecotoxicological risk of landfill leachate by heterogeneous Fenton-like oxidation

Landfill leachates are highly contaminated liquid waste, and their treatment and detoxification are a challenging task. The current system of ecotoxicological risk assessment is complex and time-consuming. It is of fundamental importance to develop simpler and faster tools for the evaluation of the treated liquid waste and for an easier preliminary screening of the most active catalytic formulation/reaction conditions of the Fenton-like process. Here, several analytical techniques have been used for the assessment of the reduction of toxicity of the landfill leachate after Fenton process over copper-zirconia catalyst (ZrCu). Ultraviolet-visible (UV-vis) spectroscopy and absorbable organic halogens (AOX) analysis have been coupled to achieve further insight into the degradation of contaminants. In addition, for the first time, the qualitative abatement of organic compounds is monitored through proton nuclear magnetic resonance (H-1 NMR) analysis, providing a new method for evaluating the effectiveness of the treatment. Spectroscopic techniques reveal that the Fenton process induces a significant abatement of the aromatic and halogen compounds (51%) in the landfill leachate with a reduction of the toxicity that has been confirmed by ecotoxicological test with algae. These results validate the investigated tool for a simple rapid preliminary evaluation of the detoxification efficacy

Silver-based catalytic materials for the simultaneous removal of soot and NOx

The potential of silver-based catalysts in the simultaneous removal of particulate matter (soot) and NOxis investigated in this work and compared with that of a model Pt-Ba/Al2O3catalyst. The Ag (5 wt%) - Ba (10 wt%)/MO (MO = CeO2, ZrO2, Al2O3) and Ag (5 wt%) - Sr (10 wt%)/CeO2catalysts have been prepared by incipient wetness impregnation and characterized by BET, XRD, HRTEM, XPS and temperature-programmed reduction (TPR) experiments. The behavior of the catalyst in the soot combustion (under loose conditions) and NOxremoval has been separately analyzed by means of temperature programmed oxidation (TPO) and isothermal concentration step change (ICSC) experiments, respectively. The results show that all the catalysts are active in soot combustion with a significant decrease of oxidation onset temperature compared to uncatalyzed soot oxidation. The removal of NOxin the absence and in the presence of soot was investigated under cycling conditions, i.e. alternating lean-rich phases according to the LNT strategy. It has been found that the Ag-based samples are able to simultaneously remove soot and NOx. In particular, comparing the behavior of the prepared catalysts, the Ba-containing systems showed higher NOxstorage capacity than Sr-catalyst; also, the nitrogen selectivity increased even if resulted lower than the traditional LNT Pt-based catalyst. A detrimental effect of soot on the NOxstorage activity has been also observed.Postprint (author's final draft

Monitoring of heavy metals, EOX and LAS in sewage sludge for agriculturale use: A case study

Subsequent to the increasing diffusion of wastewater treatment, particularly in high- and middle-income countries, the sewage sludge generated should be treated and valorised in an ecological and economic way, thus contributing to the circular economy. In this study, the monitoring of Heavy Metals (HM), Extractable Organic Halogens (EOX) and Linear Alkylbenzene Sulphonate (LAS) in sewage sludge from 10 different wastewater treatment plants located in Friuli Venezia Giulia (Italy) was reported, and their macronutrient content provided. The obtained results showed, for all tested samples, that HM content in sewage sludge was below the maximum permitted limits provided for by Italian and European regulations for agricultural reuse. Comparison with a similar monitoring campaign carried out in 2006 revealed how, while wastewater treatment plants efficiently resolved water pollution, they accumulated heavy metals and other persistent toxic compounds in sludge, thus restricting their potential reuse. Consequently, consistent and regular sludge monitoring should be undertaken to prevent soil and groundwater contamination. These outcomes could be of particular relevance for the future perspective of agricultural reuse of sewage sludge in waste management practices

Sintering behaviour of waste olivine and olivine/alumina blends

The sintering behaviour of several green compacts made with olivine or olivine/alumina powder blends has been examined. To this aim, powders were attrition milled, uniaxially pressed into specimens and air sintered at temperatures ranging from 1100 to 1300 \ub0C. The resulting samples were characterized by water absorption, shrinkage, phase composition and density. Compositions containing 5, 10 and 20% Al2O3 have a sintering behaviour similar to that of olivine alone, reaching low residual porosity when fired at 1300 \ub0C. Conversely, the composition containing 40% Al2O3 displays an almost flat shrinkage profile and maintains high residual porosity in the examined temperature range

Effects of milling on coprecipitated 3Y-PSZ powders

The present research compares properties and behaviour of co-precipitated 3Y-PSZ powders submitted, after co-precipitation, to different milling treatments. The characteristics of the different products were evaluated by measurement of particle size distribution, thermogravimetric analysis, X-ray diffraction, specific surface area and scanning electron microscopy analysis. It has been demonstrated that 1 h of attrition milling enables the production of powders containing soft agglomerates of nanometric particles: the dispersing liquid used on milling has little influence. Crystallisation into a cryptocrystalline structure of the amorphous powder is achieved after 1 h of high energetic milling, avoiding thermal treatments