High loading Fe-based catalysts for Fischer Tropsch Synthesis : optimization of synthesis procedure

Fischer-Tropsch synthesis (FT) is one of the great processes of the industrial chemistry. Starting from syngas (CO + H2), it is possible to produce a wide range of hydrocarbons, from 1 to 100 carbon atoms, using mainly cobalt or iron-based (promoted by potassium and copper) catalysts. Iron-based catalysts are widely investigated for FT due to their low costs and their good performance. Iron-based catalysts are industrially used without any support. Notwithstanding the major inconveniences, related to the employment of massive catalysts, are their fast physical degradation and their low superficial area. Instead several advantages derive from the use of supported iron catalysts, such as improved catalytic stability and lower deactivation rate, catalysts containing a support usually display a lower activity than the unsupported ones. In this work supported iron catalysts on silica for FT with high amount of metal have been prepared, characterized and tested. The iron loading has been changed between 10 and 50%wt in the presence or non-presence of promoters K and Cu. The quantity of promoters has been changed too in order to optimize the catalysts performance. An optimized catalysts, containing 30% of Fe, 2% of K and 3.75% of Cu has been identified and then prepared using different preparation methods, i.e. traditional impregnation or using ultrasound (US) and microwave (MW) in different conditions. To correlate the modification of the catalysts features (caused by the preparation method) with their performances in reaction, characterizations by BET, SEM, TEM, TPR, XRD and micro-Raman techniques have been also performed. Aim of this work is to assist the traditional impregnation method using ultrasound (US) or microwave (MW) to optimize the iron deposition. The main advantages of catalysts prepared by US derived from acoustic cavitation: bubbles formed by ultrasonic waves tend to collapse preferentially near the solid surfaces (i.e. silica surface) and collapsing bubbles generate localized hot spot. The effect of acoustic cavitation is favoured by the presence of noble gases dissolved like argon. Microwave treatment is a promising technique for catalyst preparation because of its dielectric heating characteristic, due to the possibility to generate an electric field able to polarize charges in a material. This effect is enhanced if the irradiated material presents a strong dipolar nature, as SiO2, an oxide with many surface polar OH groups. FT synthesis were carried out in a fixed bed reactor under reaction condition of 210-310 \ub0C, 20 bar and H2/CO ratio of 0.5, 1, 2, 3 for 60 h. The catalysts performance is strictly correlated with their activation, depending both by the gas and by the temperature of this step, and the treatment in syngas at T= 350\ub0C at P=3 bar for t=4 h gives the best results. A complete characterization of catalysts after different activation procedures has been performed

Perspectives for the detection and measurement of Supersymmetry in the focus point region of mSUGRA models with the ATLAS detector at LHC

This paper discusses the ATLAS potential to study Supersymmetry for the "Focus-Point" region of the parameter space of mSUGRA models. The potential to discovery a deviation from Standard Model expectations with the first few ${fb}^{-1}$ of LHC data was studied using the parametrized simulation of the ATLAS detector. Several signatures were considered, involving hard jets, large missing energy, and either $b$-tagged jets, opposite-sign isolated electron or muon pairs, or top quarks reconstructed exploiting their fully hadronic decays. With only 1 ${fb}^{-1}$ of data each of these signatures may allow to observe an excess of events over Standard Model expectation with a statistical significance exceeding 5 standard deviations. An analytical expression was derived for the shape of the distribution of the dilepton invariant mass arising from the three-body leptonic decay of the neutralinos under the hypothesis of heavy scalars, which is appropriate for the focus-point scenario. The resulting function was used to fit the distribution of the dilepton invariant mass obtained with simulated LHC data, and to extract the value of two kinematic endpoints measuring the $\tilde \chi^0_2 - \tilde \chi^0_1$ and the $\tilde \chi^0_3 - \tilde \chi^0_1$ mass differences. This information was used to constrain the MSSM parameter space compatible with the data

Post-harvest quality of fresh-marketed tomatoes as a function of harvest periods

Losses on tomato business chain start at harvest, a two-months period. At the beginning of the harvest, fruits concentrate at the basal part of the plant, then in the middle, and finally at the top, and undergo changes in diameter and maturity indexes as harvest progresses. The aim of this work was to evaluate the impact of handling at three different periods: (I) 15 days, (II) 30 days, and (III) 45 days after the beginning of harvest. Tomatoes were ordinarily grown and harvested in to bamboo baskets, and transferred to plastics boxes. Fruits were classified according to ripening stage and diameter, and evaluated for mechanical damage and external defects caused by harvesting procedures. The time required for the harvest operation was measured; damage to fruits (%) and weight loss (%), caused either in the field and/or during the harvesting process, were taken into consideration and related to the final quality of fruit after storage for 21 days. The same methodology was used all through the production and harvest cycle. The highest % fruit damage occurred during period II, a longer harvest time than the other two periods. Fruits not submitted to handling showed lower weight loss than handled fruits. Fruits harvested in period II and stored for 21 days showed higher losses due to mechanical injury

Constraining Dark Matter in the MSSM at the LHC

In the event that R-Parity conserving supersymmetry (SUSY) is discovered at the LHC, a key issue which will need to be addressed will be the consistency of that signal with astrophysical and non-accelerator constraints on SUSY Dark Matter. This issue is studied for the SPA benchmark model based on measurements of end-points and thresholds in the invariant mass spectra of various combinations of leptons and jets. These measurements are used to constrain the soft SUSY breaking parameters at the electroweak scale in a general MSSM model. Based on these constraints, we assess the accuracy with which the Dark Matter relic density can be measured.Comment: 21 pages, 12 figure