Synthesis of Supported Catalysts by Dry Impregnation in Fluidized Bed

The synthesis of catalytic or not composite materials by dry impregnation in fluidized bed is described. This process can be carried out under mild conditions from solutions of organometallic precursors or colloidal solutions of preformed nanoparticles giving rise to reproducible metallic nanoparticles containing composite materials with a high reproducibility. The adequate choice of the reaction conditions makes possible to deposit uniformly the metal precursor within the porous matrix or on the support surface. When the ratio between the drying time and the capillary penetration time (tsec/tcap) is higher than 10, the impregnation under soft drying conditions leads to a homogeneous deposit inside the pores of the particles of support. The efficiency of the metal deposition is close to 100%, and the size of the formed metal nanoparticles is controlled by the pores diameter. Finally, some of the presented composite materials have been tested as catalysts: iron-based materials were used in carbon-nanotubes synthesis, while Pd and Rh composite materials have been investigated in hydrogenation reactions

Metallic salt deposition on porous particles by dry impregnation in fluidized bed: Effect of drying conditions on metallic nanoparticles distribution

In this paper, the fluidized bed dry impregnation of coarse alumina porous particles by a metallic salt, manganese nitrate, is investigated. In this technique the penetration of each drop of metallic solution in the porous solid particle and solvent evaporation takes place at the same time, then liquid diffusion phenomenon is negligible. So, the metal loading is directly related to the operating time and liquid flow rate and concentration. It is found that the competition between two phenomena, drying and capillary flow, controls the deposit location. In order to determine the importance of the solvent evaporation process compared to the solution penetration by capillarity, an impregnation module, IM, was defined as the ratio between the drying characteristic time and a capillary penetration time. The adequate choice of the operating conditions (bed temperature, liquid and fluidization gas flow rate) allows a uniform deposition of the metallic precursor inside the porous matrix or on the support surface. The impregnation under slow drying conditions (IM ≥ 10 and solvent content in the bed atmosphere τs ≥ 0.2) leads to a homogeneous deposition inside the pores. Under fast drying conditions (IM < 5 and τs < 0.2), the deposit is located at the particle external surface.In the case of slow drying, the impregnation kinetics can be represented by a “shrinking core” model. The critical impregnation rate is controlled by the competition between dissolution and recrystallization at the elementary grain scale. The size of the metal crystallites depends on the pore mean size and size distribution and on the drying rate

Automatic fault detection on BIPV systems without solar irradiation data

BIPV systems are small PV generation units spread out over the territory, and whose characteristics are very diverse. This makes difficult a cost-effective procedure for monitoring, fault detection, performance analyses, operation and maintenance. As a result, many problems affecting BIPV systems go undetected. In order to carry out effective automatic fault detection procedures, we need a performance indicator that is reliable and that can be applied on many PV systems at a very low cost. The existing approaches for analyzing the performance of PV systems are often based on the Performance Ratio (PR), whose accuracy depends on good solar irradiation data, which in turn can be very difficult to obtain or cost-prohibitive for the BIPV owner. We present an alternative fault detection procedure based on a performance indicator that can be constructed on the sole basis of the energy production data measured at the BIPV systems. This procedure does not require the input of operating conditions data, such as solar irradiation, air temperature, or wind speed. The performance indicator, called Performance to Peers (P2P), is constructed from spatial and temporal correlations between the energy output of neighboring and similar PV systems. This method was developed from the analysis of the energy production data of approximately 10,000 BIPV systems located in Europe. The results of our procedure are illustrated on the hourly, daily and monthly data monitored during one year at one BIPV system located in the South of Belgium. Our results confirm that it is possible to carry out automatic fault detection procedures without solar irradiation data. P2P proves to be more stable than PR most of the time, and thus constitutes a more reliable performance indicator for fault detection procedures.Comment: 7 pages, 8 figures, conference proceedings, 29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam, 201

Tacit Tribes and Soft Allegiances in American Life

No abstract available

Dry impregnation in fluidized bed: Drying and calcination effect on nanoparticles dispersion and location in a porous support

The synthesis of metal nanoparticles dispersed inside the grains of a porous inorganic support was carried out by ‘‘dry impregnation’’ in a fluidized bed. The principle of this technique consists in the spraying of a solution containing a metal source into a hot fluidized bed of porous particles. The metal source can be of different nature such as metal salts, organometallic precursors or colloidal solutions. The experimental results obtained from iron oxide deposition on a porous silica gel as support, constitute the core of this article but others results concerning the deposition of rhodium from a colloidal suspension containing preformed rhodium nanoparticles are also described. More precisely, this study aims to understand the effect of the bed temperature during the impregnation step, the initial particle porosity and the calcination operating protocol on the metallic nanoparticles dispersion and location in the silica porous particles. The so-obtained products were characterized by various techniques in order to determine their morphology, their surface properties and the dispersion of the nanoparticles inside the support. The results showed that, under the chosen operating conditions, the deposit efficiency is close to 100% and the competition between the drying rate, depending on the process-related variables, and the capillary penetration rate, depending on the physicochemical-related variables, controls the deposit location. A quasi uniform deposit inside the support particles is observed for soft drying. The metal nanoparticles size is controlled by the pore mean diameter of the support as well as the calcination operating protocol

Depoliticising disaster response in a politically saturated context: the case of the 2016–19 droughts in Zimbabwe

Responding to disasters triggered by natural hazards is a deeply political process, but it is usually presented by practitioners as an apolitical endeavour. This is striking when disasters occur in authoritarian and politically highly polarised conflict-affected settings. Although the literature provides leads as to why and how humanitarians depoliticise aid, there has been little empirical research on the implications of depoliticisation, especially at the community level. Based on qualitative fieldwork that focused on the drought responses that overlapped with the 2016–19 sociopolitical crises in Zimbabwe, this paper details the practices, motivations, and implications of humanitarian depoliticisation. It differentiates between strategic, coerced, and routine managerial depoliticisation, and argues that, in an authoritarian conflict-affected setting, depoliticisation strategically allows state and non-state actors to defuse sensitive issues and actor relations and to remain safe. However, depoliticisation can also have implications for information management, monitoring, accountability, and protection, and thus ultimately for upholding humanitarian principles

Disaster cultures and the Indonesia Tsunami Early Warning System: (mis)alignments revealed by the 2018 non-tectonic tsunami in Labuan

This study examined the (mis)alignments between multiple disaster cultures, the Indonesia Tsunami Early Warning System (InaTEWS) and local risk profiles as revealed by the 2018 non-tectonic tsunami triggered by the Anak Krakatau Volcanic eruption in Labuan. The research assessed to what extent the tsunami warning system was adapted to local needs and characteristics. Based on qualitative data collection, this study showed that before the 2018 tsunami (and notwithstanding memories of the 1883 Krakatau tsunami) different local groups shared a strikingly homogeneous understanding of tsunamis as exclusively triggered by earthquakes. After the 2018 tsunami, study participants reported increased awareness of different tsunami types and earthquake risks. However, this rarely translated into practical actions and changes at the local level as structural and cultural factors significantly hampered the work of local government and emergency management agencies. This research identified steps to improve alignment, for example by involving community members in warning technology maintenance, tailoring awareness-raising materials to local hazard profiles and connecting awareness-raising with local cultural traditions. However, a reform of the InaTEWS is necessary, including overcoming sectoral silos and incorporating local knowledge and experiences into policymaking. By addressing these (mis)alignments, authorities can better support communities to understand tsunami risks and respond to future event, ultimately enhancing preparedness

Annual Survey of Virginia Law: Criminal Law and Procedure

This article discusses holdings and trends in the published cases of the Virginia Court of Appeals and the Supreme Court of Virginia from August 1996 to July 1997. Although the form of this article generally follows the same form used by prior authors, several subject headings have been renamed to reflect the current focus of the courts. For example, during this period the court of appeals grappled with the community caretaker doctrine, bifurcated sentencing proceedings in felony cases, jury selection, and various hearsay exceptions. The supreme court addressed an indigent defendant\u27s right to expert assistance, administrative license suspensions, and speedy trial issues