In the present work, the kinetics of oleic acid esterification with methanol has been studied by using an acid ion-exchange polymeric resin (Relite CFS) as the heterogeneous catalyst. The kinetics of ...the reaction has been studied by performing batch runs at different temperatures and in the presence of a certain amount of triglyceride for simulating an oil with a high content of free fatty acids, which is of great potential interest as a raw material in the biodiesel production process. The experimental data have been interpreted with a second-order, pseudo-homogeneous kinetic model, and a good agreement between the experimental data and the model has been obtained.
In the last few years, an intense R &D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of ...already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.
In the present work, the kinetics, mass transfer and heat transfer of soybean oil epoxidation with H₂O₂ have been studied in a fed and pulse-fed-batch reactor. The reaction has been performed with ...peroxyformic acid (PFA), generated in situ, by reacting concentrated hydrogen peroxide (60wt.%) with formic acid (FA), in the presence of sulphuric or phosphoric acid as catalysts. The kinetic study also considers two important aspects occurring simultaneously with the epoxidation reaction, namely: the degradation resulting from the opening of the oxirane rings, and the hydrogen peroxide decomposition. Epoxidation is a highly exothermic reaction and the evolution of the temperature in the reactor over a period of time is strongly dependent on the amounts and way in which a mixture of H₂O₂ and formic acid is added to the mixture of oil and catalyst. In this paper, a biphasic kinetic model has been developed considering all of the occurring reactions in each phase, the partition of reagents and products between the phases and the evolution of any involved chemical specie along the time. Different kinetic runs have been successfully simulated after the evaluation, by mathematical regression analysis or by independent means, of all the kinetic and thermodynamic parameters of the model. The heat transfer properties of the used reactor have been determined following different approaches. In addition, the evolution of the temperature of the reacting mixture during the time has also been simulated with the developed mathematical model.
•Dynamic intraparticle model for fluid–solid adsorption kinetics.•Mass balances for both bulk and particle pore phases.•All the possible mass transfer phenomena have been considered.•The PDEs set has ...been solved with centered finite difference method of lines.•Cu(II) and Pb(II) adsorption on silica based sorbents as case study.
The fluid–solid adsorption batch kinetics is surely one of the most popular topic in the chemical engineering science. The water purification from pollutant components, such as metals and organic compounds, can be considered one of the main application of this field. Even if the topic is of a great scientific and industrial interest, the modeling of the mentioned systems is by now far to be reliable. As a matter of fact, most of the models reported in the literature are based on semi empirical approaches that describe the adsorption experimental data on the basis of equilibria and the kinetic terms. In this paper, a new modeling approach is proposed for adsorption kinetics investigation performed in batch reactors with a fluid–solid system. In particular, the mass balances have been developed by taking into account for both the external and internal mass transfer diffusion limitations, solving the dynamic partial differential equations (PDEs) system along the radius of the sorbent particles, considering both the fluid and solid phases that constitute the sorbent particle. From a numerical point of view, the solution of this type of problem is very challenging because it involves the simultaneous solution of many PDEs, ODEs and AEs. Here, physical parameters have to be evaluated either from existing correlations or by direct measurements. This fact makes the model predictable. In order to test the model, some Cu(II) and Pb(II) adsorption tests, taken from literature, using different kind of silica have been interpreted. The presented model can be considered of great interest, as it is the starting point for designing continuous adsorption columns for water purification.
Nowadays, most biodiesel (fatty acids methyl esters, FAME) is produced by the transesterification of triglycerides (TG) of refined/edible type oils using methanol and an homogeneous alkaline ...catalyst. However, production costs are still rather high compared with the ones of petroleum-based diesel fuel. To lower costs and make biodiesel competitive less-expensive feedstocks such as waste fats or non-edible type oils could be used. The use of homogeneous alkaline catalysts in the transesterification of such types of fats and oils poses great difficulties due to the presence of large amounts of free fatty acids (FFA). This paper studies the use of carboxylic salts as a possible alternative, because these catalysts are active also in the presence of high FFA concentrations.
The most active catalyst (Cd, Mn, Pb, Zn carboxylic salts) have been individuated and a correlation of the activities with the cation acidity has been found.
The use of classical alkaline catalysts in the transesterification of waste fats and oils to obtain fatty methyl esters (FAME) poses great difficulties due to the presence of large amounts of free fatty acids (FFA). This paper studies as a possible alternative, the use of different bivalent metals. The most active catalysts have been individuated and a correlation of the activities with the cation acidity has been found.
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Biodiesel, a renewable fuel of vegetal origin, has been an object of a rapidly growing interest, in the latest years, both as a pure fuel and as blending component to reduce exhaust pollutants of ...traditional diesel fuel. Biodiesel is conventionally produced through a well-established technology that involves the use of alkaline catalysts and is, therefore, not compatible with the presence of free fatty acids (FFAs) in the feedstock due to the formation of soaps. Also the presence of FFA in small amounts is detrimental, because, formed soaps strongly affect the successive glycerol separation giving place to a long settling time. Normally, highly refined vegetable oils are used as raw materials for biodiesel production. A preliminary stage of acidity reduction is necessary, when the starting material is characterized by a high free acidity (higher than 0.5% by weight). This pre-treatment can be pursued, as example, by means of an esterification reaction of the FFAs with methanol, catalyzed by sulphonic ionic exchange resins. In the present work, a batch reactor has been used for the study of the above-mentioned reaction and different acid ionic exchange resins have been tested as heterogeneous catalysts. Two kinds of substrates have been submitted for esterification with methanol: a model mixture of soybean oil artificially acidified with oleic acid and a commercial high-acidity mixture of waste fatty acids (oleins). A detailed kinetic model has been developed and tested in which the following key phenomena, characterizing the system, have been introduced: (i) the physical phase equilibrium (partitioning equilibrium) of the components between the resin-absorbed phase and the external liquid phase; (ii) the ionic exchange equilibria; (iii) an Eley–Rideal surface reaction mechanism. The developed kinetic model was able to correctly interpret all the experimental data collected, both as a function of the temperature and of the catalyst concentration.
Results obtained by the RPC ECOgas@GIF++ Collaboration, using Resistive Plate Chambers operated with new, eco-friendly gas mixtures, based on tetrafluoropropene and carbon dioxide, are shown and ...discussed in this paper. Tests aimed to assess the performance of this kind of detectors in high-irradiation conditions, analogous to the ones foreseen for the coming years at the Large Hadron Collider experiments, were performed, and demonstrate a performance basically similar to the one obtained with the gas mixtures currently in use, based on tetrafluoroethane, which is being progressively phased out for its possible contribution to the greenhouse effect. Long term aging tests are also being carried out, with the goal to demonstrate the possibility of using these eco-friendly gas mixtures during the whole High Luminosity phase of the Large Hadron Collider.
In the synthesis of biodiesel via the transesterification of vegetable oils, 10 wt % of glycerol is obtained as byproduct. This means that, by increasing the biodiesel production, the glycerol ...availability also increases and its cost goes down more and more. In order to consume the large amount of glycerol derived from biodiesel production in a profitable way, only two strategies are possible: (i) use glycerol as raw material to produce fuel additives and (ii) use glycerol as raw material to produce commodities. In the present work, we have briefly considered the first aspect while focusing, in particular, on the second opportunity by reviewing the production of chlorohydrins by glycerol hydrochlorination with HCl. Chlorohydrins are important intermediates in the production of epichlorohydrin used to produce epoxy–resins. The advantages of producing chlorohydrins by starting from glycerol instead of propenethat is, the classical routewill be discussed. The glycerol hydrochlorination reaction is catalyzed by carboxylic acids, and in this work, we describe (i) the reaction conditions normally adopted; (ii) the behavior of different catalysts proposed in the literature (concerning activity and selectivity); (iii) the reaction mechanism; (iv) the kinetic laws, reported by different authors, along with the related parameters; and (v) the role of mass transfer. A brief discussion on the best reactors for performing the reaction and some information about the different processes used to produce epichlorohydrin starting from glycerol will also be reported. Some catalysts, other than carboxylic acids, have also been briefly reviewed, although they have not been used in industrial plants until recently.
The present paper reports and discusses results on the preparation, characterization and catalytic performances of silica-supported titania (TiO2/SiO2) catalysts. Samples were prepared by grafting ...titanium tetraisopropoxide (Ti-OPri)4, dissolved in toluene, onto a silica surface in an N2 atmosphere, followed by steam hydrolysis and calcination. The samples were characterized by chemical analysis, BET surface area measurements, X-ray diffraction (XRD), DR-UV-vis, FTIR and DRIFT spectroscopy analyses, TEM/EDX and NH3-TPD. The results indicated that the grafting preparation method gives rise to very strong Si-O-Ti bonds, that are responsible for high titanium dispersion. In particular, at low Ti loading, titanium species in tetrahedric coordination resulted prevalent on the catalyst surface until the maximum surface monolayer coating reached (2.2Ti atoms/nm2). The degree of polymerization of Ti species increases with further TiO2 load increases, giving rise to a large amount of octahedrical Ti-sites grafted on SiO2. The effects on the catalytic activity of TiO2/SiO2 catalysts with increasing quantities of TiO2 were also investigated. The catalytic results obtained in the epoxidation reaction of cyclooctene with cumene hydroperoxide showed the significant effect of titanium loading on the physicochemical and reactivity/selectivity properties of the silica-supported titania catalysts.
A new class of catalysts promoting the hydrochlorination of glycerol to obtain selectively 1,3-dichlorohydrin has recently been discovered. These catalysts are acyl chlorides and prove to be much ...more active and sometimes more selective than the corresponding carboxylic acids, usually employed to promote this reaction. Many different kinetic runs have been performed to compare the performances of acetyl chloride and acetic acid, propanoyl chloride and propionic acid, adipoyl dichloride and adipic acid, succinyl dichloride and succinic acid, and malonyl dichloride and malonic acid, respectively. In all cases, the activity of the acyl chloride proved to be much higher. This behavior has been discussed and explained on the basis of a possible reaction mechanism. The reaction occurs rapidly even if glycerol is contaminated with NaCl. By adding a stoichiometric amount of an acyl chloride to glycerol, the hydrochlorination occurs in a short time, with a high selectivity, without any external supply of HCl, because acyl chlorides react promptly and quantitatively with glycerol forming HCl in situ. To avoid an excessive increase of the HCl pressure, acyl chlorides must be fed into a reactor containing glycerol with an opportune flow rate. The flow rate employed affects both the activity and the selectivity as has been demonstrated in two kinetic runs performed at two different flow rate levels of acetyl chloride.
