Deactivation Pattern of a "Model" Ni/MgO Catalyst in the Pre-Reforming of n-Hexane †

The deactivation pattern of a "model" Ni/MgO catalyst in the pre-reforming of n-hexane with steam (T, 450 °C; P, 5–15 bar) is reviewed. The influence of the steam-to-carbon ratio (S/C, 1.5–3.5) on the rate of catalyst fouling by coking is ascertained. Catalyst fouling leads to an exponential decay in activity, denoting 1st-order dependence of the coking process on active sites availability. Hydrogen hinders the coking process, though slight activity decay is due to sintering of the active Ni phase. Deactivation by thiophene causes a sharp, almost linear, drop to nearly zero activity within only 6 h; this deactivation is likely due to dissociative adsorption of thiophene with subsequent strong, irreversible chemical adsorption of S-atoms on active Ni sites, i.e., irreversible poisoning. Modeling of activity decay curves (α, at/a0) by proper kinetic equations allows assessing the effects of temperature, pressure, S/C, H2 and thiophene feed on the deactivation pattern of the model Ni/MgO catalyst by coking, sintering, and poisoning phenomena

Long-Term Statistics and Extreme Waves of Sea Storms

AbstractA stochastic model of sea storms for describing long-term statistics of extreme wave events is presented. The formulation generalizes Boccotti's equivalent triangular storm model by describing an actual storm history in the form of a generic power law. The latter permits the derivation of analytical solutions for the return periods of extreme wave events and associated statistical properties. Lastly, the relative validity of the new model and its predictions is assessed by analyzing wave measurements retrieved from two NOAA National Oceanographic Data Center (NODC) buoys in the Atlantic and Pacific Oceans

The role of activated carbon size in the catalytic cracking of naphthalene

Activated carbons are efficient catalysts for tar cracking, suitable for hot cleaning of the syngas produced during biomass- and waste-to-energy gasification processes. This study investigates the conversion of naphthalene, utilised as reference for tar compounds, when catalysed by a coal-derived activated carbon. The attention focuses on the influence of the operating temperature, in the range 750-900°C, and the size of selected activated carbon, which has been used under form of pellets, granules and powders. The conversion efficiency improves when the temperature raised from 750°C to 900°C (from 79% to 99%, for the pellets), and when the catalyst size reduced from pellets to powders (from 79% to 97%, at 750°C). The diffusional resistance in the catalyst particles has been then quantified in terms of Thiele modulus and internal effectiveness factor. A gradual reduction of catalyst surface area has been also observed for longer tests, due to the progressive deposition of soot from naphthalene decomposition over and inside the porous structure of the activated carbon. The carbon content of these deposits has been quantified, showing larger percentages on the surface of granules and powders.Activated carbons are efficient catalysts for tar cracking, suitable for hot cleaning of the syngas produced during biomass- and waste-to-energy gasification processes. This study investigates the conversion of naphthalene, utilised as reference for tar compounds, when catalysed by a coal-derived activated carbon. The attention focuses on the influence of the operating temperature, in the range 750–900 °C, and the size of selected activated carbon, which has been used under form of pellets, granules and powders. The conversion efficiency improves when the temperature raised from 750 °C to 900 °C (from 79% to 99%, for the pellets), and when the catalyst size reduced from pellets to powders (from 79% to 97%, at 750 °C). The diffusional resistance in the catalyst particles has been then quantified in terms of Thiele modulus and internal effectiveness factor. A gradual reduction of catalyst surface area has been also observed for longer tests, due to the progressive deposition of soot from naphthalene decomposition over and inside the porous structure of the activated carbon. The carbon content of these deposits has been quantified, showing larger percentages on the surface of granules and powders

“Peace, peace, but there is no peace”: prophetic conflicts in Jeremiah, Ezekiel and Micah

This work looks at a peculiar blaming of the religious class (especially, the prophets) as it appears in the books of Jeremiah, Ezekiel and Micah. In these three books, the prophets (coupled with the priests on two occasions but only in the book of Jeremiah) are said to have promised peace ( שלום ) to the nation. Such promises are exposed as blatant falsehood ( ,(שקר and the prophets who uttered them are dismissed as liars who lead the people astray from YHWH. This accusation appears with minor variations in several excerpts throughout these books (Jer 5:30–31; 6:13–15; 8:10b–12; 14:13–16; 23:13–32; 27–29; 37:19; Ezek 13:1–16; Mic 3:5–8). Moreover, especially in the book of Jeremiah, the reader comes across a connection between “falsehood” and the idea of “promising peace”. In the books of Jeremiah, Ezekiel and Micah, the dynamics of “prophet of the book vs. other prophets” often turn up and seem to be intertwined with the motif of having promised a false peace. Hence, this study aims to explain the reasons behind such peculiar allegations, which are presented as prophetic conflicts. The terms often used to express these conflicts, in the tradition and in scholarship, are “true” prophets vs. “false” prophets. These labels are however ambiguous, since an analysis of all the passages mentioned above does not appear to delineate the so-called “false” prophets as a homogenous group, who is antagonistic towards the “true” prophets of the tradition. It seems that the books of Jeremiah, Ezekiel and Micah originally presented an anti-prophetic attitude, thus accusing all the prophets, and only later new readings (supported by redactional interventions) emphasized the prophetic role bestowed upon their main characters (the prophets Jeremiah, Ezekiel and Micah), thereby generating an interpretation that favours the division of the prophetic class into legitimate and illegitimate members. Consequently, as this work argues, prophetic conflicts are literary creations of some later redactors of the books and are always aimed at backing up their ideological stances. In addition, while analysing the false promises of peace, the present thesis also covers the literary growth and transmission of this theme in the books of Jeremiah (where it seems to originate from), Ezekiel and Micah (where it appears to be secondary and modelled on Jeremiah). Although prophetic conflicts are expression of the ideology of the redactors, such ideology is the product of a cultural and historical environment that at some point during the history of Israel produced this strand of thought within the biblical prophetic tradition. Hence, this research acknowledges that the biblical texts, although not providing any reliable historical reconstruction (because the redactors were not historians by any means), still allow the biblical scholar to attempt to recreate the historical moment and context that may have given birth to the ideology which lay behind prophetic conflicts (and the theme of the “false” prophets), and to trace its historical and literary development in the books of Jeremiah, Ezekiel and Micah

About the Environmental Sustainability of the European Management of WEEE Plastics

A huge increase of waste of electrical and electronic equipment (WEEE) is observing everywhere in the world. Plastic component in this waste is more than 20% of the total and allows important environmental advantages if well treated and recycled. The resource recovery from WEEE plastics is characterised by technical difficulties and environmental concerns, mainly related to the waste composition (several engineering polymers, most of which containing heavy metals, additives and brominated flame retardants) and the common utilisation of sub-standard treatments for exported waste. An attributional Life Cycle Assessment quantifies the environmental performances of available management processes for WEEE plastics, those in compliance with the European Directives and the so-called substandard treatments. The results highlight the awful negative contributions of waste exportation and associated improper treatments, and the poor sustainability of the current management scheme. The ideal scenario of complete compliance with European Directives is the only one with an almost negligible effect on the environment, but it is far away from the reality. The analysed real scenarios have strongly negative effects, which become dramatic when exportation outside Europe is included in the waste management scheme. The largely adopted options of uncontrolled open burning and illegal open dumping produce huge impacts in terms of carcinogens (3.5·10+7 and 3.6·10+4 person·year, respectively) and non-carcinogens (1.7·10+8 and 2.0·10+6 person·year) potentials, which overwhelm all the other potential impacts. The study quantifies the necessity of strong reductions of WEEE plastics exportation and accurate monitoring of the quality of extra-Europe infrastructures that receive the waste

Can plastics from end-of-life vehicles be managed in a sustainable way?

Plastic from end-of-life vehicles (ELVP) are currently managed in European Union without any attention to polymer recovery. The study analyses novel treatments of sorting, dissolution/precipitation, extrusion, catalytic pyrolysis, and plastic upgrading, which could contribute to define a sustainable ELVP management scheme. The environmental performances of each of these treatments have been quantified by an attributional Life Cycle Assessment, allowing to compare a possible innovative recycling scheme with that of the European currently adopted options. The new scheme greatly enhances ELVP management performances, by hugely increasing annual amounts of polymers sent to recycling (from 26 kt/y up to 509 kt/y), drastically decreasing residues to be sent to combustion or landfill (from 984 kt/y down to 232 kt/y), and improving the impact of main environmental categories. Carcinogens, Non-Carcinogens, Global Warming and Non-Renewable Energy reduce of 138%, 100%, 42% and 114%, with reference to the current scenario. These promising results are mainly related to the utilisation of a dissolution/precipitation process (Crea-Solv®), whose introduction could allow recovering large part of target polymers (PE and PP). The recovery of PE in fuel tanks by a supercritical extrusion process (Extruclean) and the treatment of residues and non-target polymers by a catalytic pyrolysis process also contribute to improve the environmental performances. A sensitivity analysis quantifies the role of some key parameters, indicating that the results could be affected by energy consumption of dissolution/precipitation process, oil yield of catalytic pyrolysis treatment, but also by the substitutability factor utilised to quantify the avoided burdens associated to the recycled polymers

Novel Control Flow Checking Implementations for Automotive Software

Safety-critical applications shall be implemented on highly dependable systems, and a part of their reliability is based on checking if the software is executed correctly. Various techniques are available for this purpose, like Control Flow Checking (CFC). Many CFC algorithms can be found in the literature, but their detection performances are assessed in theoretical scenarios, when implemented in Assembly language. The international standard on functional safety for automotive applications is ISO26262. It mandates to develop using high-level programming languages and the computation of the Diagnostic Coverage (DC). The DC measures the effectiveness of the chosen hardening method, in order to detect various Failure Modes (FMs). This paper discusses two alternative solutions, one software-only, and the other involving customized hardware, for these concerns: (i) address the FMs affecting the computation units described by Table 30 of part 11 of the ISO26262 (ii) guarantee the Freedom From Interference between the hardening method and the monitored entity

DFT insights into the oxygen-assisted selective oxidation of benzyl alcohol on manganese dioxide catalysts

The reactivity pattern of the MnO2 catalyst in the selective aerobic oxidation of benzyl alcohol is assessed by density functional theory (DFT) analysis of adsorption energies and activation barriers on a model Mn4O8 cluster. DFT calculations predict high reactivity of defective Mn(IV) sites ruling a surface redox mechanism, L-H type, involving gas-phase oxygen. Bare and promoted (i.e., CeOx and FeOx) MnOx materials with high surface exposure of Mn(IV) sites were synthesized to assess kinetic and mechanistic issues of the selective aerobic oxidation of benzyl alcohol on real catalysts (T, 333- 363K). According to DFT predictions, the experimental study shows: i) comparable activity of bare and promoted catalysts due to surface Mn(IV) sites; ii) the catalytic role of oxygen-atoms in the neighboring of active Mn(IV) sites; and iii) a 0th-order dependence on alcohol concentration, diagnostic of remarkable influence of adsorption phenomena on the reactivity pattern. Evidences of catalyst deactivation due to the over-oxidation of benzyl alcohol to benzoic acid, acting as poison of the active sites, are discussed