Vanadium phosphate (VOP) catalysts resulted very active in the transesterification reaction of triglycerides with methanol. A slow deactivation of the catalysts has been observed but the catalyst can ...easily be regenerated by calcination in air. The characterization results showed that the deactivation is due to a progressive reduction of vanadium species from V
5+ to V
4+ and V
3+ by methanol. VOP catalysts could already be used industrially for biodiesel production but their performances can probably be greatly improved in perspective.
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The possibility of using vanadyl phosphate (VOP)-based catalysts in biodiesel production has been investigated. Vanadium phosphate catalysts resulted very active in the transesterification reaction of triglycerides with methanol, despite their low specific surface area. A slow deactivation of the catalysts has been experimentally detected under the reaction conditions, but the catalyst can easily be regenerated by calcinations in air. The influence of the calcination treatment on the surface structure and, consequently, on its catalytic performances was deeply investigated. Both fresh and used catalysts were characterized by using several techniques, such as BET, X-ray diffraction (XRD), UV–vis diffuse reflectance (DRUV) and laser-Raman (LRS). The characterization results showed that the deactivation is due to a progressive reduction of vanadium (V) species from V
5+ to V
4+ and V
3+ by methanol. By comparing the obtained performances of VOP catalysts with the ones of other heterogeneous catalysts reported by the literature, it is possible to conclude that VOP catalysts can already be used industrially for biodiesel production but their performances can probably be greatly improved in perspective.
The reuse of olive mill wastewater (OMW) by spreading on agricultural land is subject to a long-time debate since they supply to agricultural land both substances of undoubted positive influence on ...fertility and compounds that may adversely alter its chemical, physical and microbiological characteristics and/or cause negative effects on crops. In this study different amounts of OMW from 3-phases centrifugal decanter were spread in February on soil cultivated with grapevine in a research-farm located in central Italy for 11 consecutive years, with the aim to verify the long term effect on grape production, physico-chemical and microbiological characteristics of soil. In particular, the effect of the OMW spread in the largest amount (50 L m
−2
) was an increase of the weight of the grape-brunches and total grapes production and, in addition, an improvement of the soil characteristics due to the increase of the content of the organic reducing substances with humic-like properties. Moreover, it was also ascertained that in the short-medium period (2–8 months) the respiratory activity of the micro-organisms of the soil parcels, treated with different amount of OMW, was higher than that of the soil control parcels. The results obtained demonstrated that the controlled spreading of OMW helps to increase both the grapes crop and the fertility of the soil, recycling the organic matter and mineral nutrients, in this way allowing to reduce, or avoid, the use of chemical fertilisers.
A continuous hydrogen peroxide propene oxide (HPPO) lab-scale pilot plant was designed and tested for the production of propene oxide via HPPO process. The plant was equipped with a continuous ...stirred tank reactor, able to work under nitrogen pressure with liquid propene. Attention was paid to the feed system and the plant control, the lab-scale pilot plant being completely automated. Hydraulic tests were performed to check the performance of the plant; a fluid-dynamic characterization was conducted to evaluate the residence time distribution. Propene oxide synthesis experiments were performed to evaluate both hydrogen peroxide conversion and propene oxide selectivity. The collected data were interpreted with a recently published kinetics, validating the developed model, obtaining satisfactory results, also in simulating the start-up transient state of the reactor. The model can be considered of high utility in designing and optimizing HPPO process, to achieve high reactant conversions and propene oxide yields.
The electron-positron collider DA Phi NE, the Italian Phi factory, has been recently upgraded in order to implement an innovative collision scheme based on large crossing angle, small beam sizes at ...the crossing point, and compensation of beam-beam interaction by means of sextupole pairs creating a "crab-waist" configuration in the interaction region. Experimental tests of the novel scheme exhibited an increase by a factor of 3 in the peak luminosity of the collider with respect to the performances reached before the upgrade. In this Letter we present the new collision scheme, discuss its advantages, describe the hardware modifications realized for the upgrade, and report the results of the experimental tests carried out during commissioning of the machine in the new configuration and standard operation for the users.
Resistive Plate Chamber detectors are largely used in current High Energy Physics experiments, typically operated in avalanche mode with large fractions of Tetrafluoroethane (C2H2F4), a gas recently ...banned by the European Union due to its high Global Warming Potential (GWP). An intense R&D activity is ongoing to improve RPC technology in view of future HEP applications. In the last few years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to investigate the performance of present and future RPC generations with eco-friendly gas mixtures. Detectors with different layout and electronics have been operated with ecological gas mixtures, with and without irradiation at the CERN Gamma Irradiation Facility (GIF++). Results of these performance studies together with plans for an aging test campaign are discussed in this article.
Olive mill wastewater (OMW) is the liquid by-product obtained from olive processing to extract virgin olive oil by mechanical means. The acid pH and the high amounts of organic matter and phenols ...make it very difficult to further purify this material. The question is then what to do with it? A solution would be to spread it on the soil. The objective of this study was to explore the effects of different OMW amounts on the chemical characteristics and on microbial community of the soil cultivated with olive trees (
Olea europaea L.). The increase of the organic matter and phenols, due to the treatment with OMW, was found in the soil as well as the microbial biomass, as estimated by direct cell counting and by measuring soil-induced respiration. It was observed that the OMW spreading in high amounts increased the soil-denitrifying community while nitrifying populations decreased slightly, probably owing to the reductive effect of phenols. In the present paper we investigated the effects of OMW spreading on the chemical characteristics and on different groups of bacteria and fungi within microbial community, in soil cultivated with olive trees, at different depth of 10–20
cm and 20–40
cm.
•Acid catalyzed hydrolysis of galactoglucomannan and inulin was studied.•A specially constructed isothermal continuous reactor setup was employed.•A dynamic mass balance-based reactor model was ...developed and successfully implemented.•Mechanistically based self-accelerating kinetics was utilized.•Numerical simulations were further used to demonstrate the laminar flow behaviour.
Hydrolysis of hemicelluloses with acid catalysts yield different sugar monomers and oligomers, depending on the substrate as well as the process design. The hydrolysis kinetics are typically rather slow, which leads to requirements of long residence times, i.e. slow flow rates, in order to achieve adequate conversion. Hydrolysis experiments of two different polysaccharides – o-acetylgalactoglucomannan (GGM) and inulin - were conducted in an isothermal tubular continuous reactor in laboratory scale, working in the laminar flow regime. A dynamic mass balance-based reactor model was developed, including convection and molecular diffusion in axial and radial directions, as well as the self-accelerating kinetics of the reaction. The model gave a very satisfactory description of the experimental data. The behavior of the laminar flow reactor in the hemicellulose hydrolysis was further illustrated by numerical simulations.
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•Transient intraparticle model for fluid–solid adsorption kinetics.•The PDEs system solved with method of lines.•Literature datasets tested with the proposed model obtaining good ...results.•Physical parameters fitted on the experimental data.•The model is a starting point to design adsorption columns.
Recently, a diffusive intraparticle dynamic model has been published by the authors and applied for describing few systems in order to check its validity. The aim of the present paper is to improve its validity in describing different kind of systems. At this purpose, adsorption data have been taken from literature, in which different adsorbate/adsorbent systems have been considered. In every case, the surface diffusivity of the pollutant (DS) has been fitted on the experimental data. The obtained parameters fall within reasonable ranges and a good fitting has been obtained for each case, demonstrating the generality of the adopted model.
Samples were prepared by grafting different amounts of titanium isopropoxide (Ti(OPri)4) onto silica surface in N2 atmosphere, followed by steam hydrolysis and calcination. Either dioxane or toluene ...was used as a solvent. The surface properties of TiO2/SiO2 catalysts were studied by means of FTIR spectroscopy of adsorbed probe molecules, CO, and ammonia. Adsorption of CO at nominal 77 K exhibited different surface sites: (i) two families of Ti4+ cations, namely associated and isolated sites, with bands in the 2183-2194 and 2173-2177 cm-1 ranges respectively, shifting with coverage; (ii) surface SiOH groups; and (iii) at titanium loadings >8 wt% TiO2, corresponding to the alkoxide monolayer coverage of silica, TiOH species exhibiting an acidity higher than expected (observed shift delta v=200 cm-1), probably due to interaction with the support. With increasing the titanium loading, the band at 2176 cm-1 disappears, indicating that associated Ti4+ sites form at the expense of isolated ones. Adsorption of ammonia at room temperature confirms the data obtained with CO. The use of apolar solvents seems to cause anchoring of the Ti alkoxide on the dehydrated portions of the silica surface, with consequences for the final state of the catalyst. In agreement with this observation, activity was lower for catalysts prepared in toluene than in those prepared using dioxane. Prepared catalysts were rather effective in the transesterification of refined oils with methanol. PUBLICATION ABSTRACT
Biodiesel is usually produced by reacting triglycerides, contained in vegetable oils, with methanol in the presence of KOH, NaOH, or related alkoxides as catalysts. In industry, the reaction is ...performed in stirred tank reactors and requires 1–2 h of reaction time being the reaction rate strongly affected by mass transfer limitation. We have recently shown, by using a Corrugated Plates Heat Exchanger Reactor, that a very high productivity (about 2 tons/day L) can be obtained by working at 60–100 °C thanks to the presence of an intense local “micromixing”. Moreover, we have recently tested the performances obtained in a tubular reactor filled with stainless steel spheres of different diameters. By opportunely changing the spheres diameters it is possible to obtain microchannels in a range of 300–1000 μm with an intense local micromixing. Again, thanks to micromixing we obtained very high productivities. However, in these last reactors the void portion of the reactor is low and the productivity per overall reactor volume is relatively low. It is possible to obtain better results, in terms of productivity, by filling the tubular reactor with stainless steel wool, being in this case the void fraction about 0.9. In the present work, some of the mentioned systems will be compared for their performances by using different amounts of KOH as catalyst (1 or 2% b.w. of oil). A dramatic change in biodiesel yield has been observed in all cases passing from 1 to 2% of catalyst independently of the reactants flow rate. These behaviors cannot be interpreted with the pseudomonophasic kinetic models, normally reported in the literature. At this purpose, for interpreting all the observed kinetic behaviors a new biphasic kinetic model, based on a reliable catalytic mechanism, has been developed. This model has been applied, first of all, to data reported in the literature related to runs performed in batch conditions with the scope of estimating the kinetic parameters, and then it has been applied to all the runs performed in continuous reactors with a satisfactory agreement.
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