Loop reactor modeling for lubricants synthesis Vitiello, R.; Tesser, R.; Russo, V. ...
Chemical engineering journal (Lausanne, Switzerland : 1996),
12/2017, Letnik:
329
Journal Article
Recenzirano
•Biolubricants synthesis from renewable chemicals.•H2WO4/SiO2 shows good catalytic performances at high temperature.•Catalysts are stable for 3-4 reuse cycles.•Scale-up attempt testing the catalysts ...in loop reactor.•A lumped kinetic model was developed to interpret both batch and loop tests.
In this work biolubricant synthesis, obtained by esterification reaction between fatty acids and several polyols using H2WO4/SiO2 as acid catalysts has been reported. Biolubricants in the last few years have generated a great interest in the scientific community and represent an alternative to the petrochemical lubricants. Their properties are similar to those of petrochemical lubricants but at the same time they are more degradable, less toxic and so less polluting with respect to mineral lubricants. The purpose of this work is to verify the catalytic activity and the catalyst stability in the esterification reaction by performing experiments in both batch and loop packed bed reactors. The results obtained for the synthesis of lubricants are very encouraging: high yields and a good stability of the catalyst. The collected data have been interpreted with a lumped kinetic model, obtaining satisfactory results for both the investigated systems.
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► Grafted VOx on TiO2/SiO2 catalysts for selective photocatalytic oxidation of ethanol to acetaldehyde. ► Ethanol conversion decreased by increasing TiO2 loading. ► Further ...enhancement of acetaldehyde yield by the highly active V species. ► In presence of phosphors, photoactivity increased with the increase of ethanol inlet concentration.
In this work gas phase photocatalytic selective oxidation of ethanol to acetaldehyde was studied with directly fluidizable photocatalysts made of grafted VOx on titania/silica in presence of phosphors as light carriers to test their performances in the photocatalytic system. The presence of VOx species anchored on TiO2/SiO2 enhanced ethanol conversion up to 66%, with acetaldehyde selectivity higher than 99%. The performances of V-based sample at 11wt% of TiO2 supported on fluidizable support were higher than those evaluated when nano-TiO2 powder is used as support. Moreover, the photocatalytic conversion of ethanol was further increased in presence of phosphors as light carriers. From the obtained results, it is concluded that by preparing VOx based catalyst through grafting method allows a dramatic enhance in the productivity of acetaldehyde, even when the concentration level of alcohol at photoreactor inlet is increased.
Microreactors are especially well-suited for laboratory-scale studies of rapid exothermic reactions, because they have excellent mass and heat transfer characteristics. Two novel reactor models were ...used for plate microreactors, one for a washcoated reactor and the other one for a silver plate microreactor. The aim of this modeling study was to precisely explain both the concentration and the temperature dependencies of the reaction rates of ethylene oxide (EO) synthesis over a wide range of operating conditions (p, T, flows) by using all the extensive data generated with our microreactors. Microreactors are especially well suited for producing accurate kinetic data because of the uniformity of reaction conditions in the reactor system.
Modeling took into account the reaction and mass transfer effects. The axial and radial concentration profiles and for the washcoated case also the concentration profiles along the coating direction were solved numerically. The models were based on dynamic mass balances for the gas phase, with convection, axial and radial dispersion terms included. From the modeling viewpoint, an interesting phenomenon, the interaction between intrinsic kinetics and diffusion in the porous catalyst layer, was tackled with the aid of mathematical modeling for the washcoated reactor case. The reactor models were solved numerically by using gPROMS software. Ethylene oxidation on silver catalyst was the selected example reaction system, because the main product, ethylene oxide, is a key compound and an important intermediate for chemical industry. The reactor and kinetic models were able to describe all the experimental data with a very satisfactory agreement. The microreactor models developed are generic and applicable to various kinds of heterogeneously catalyzed gas-phase reaction systems.
The industrial breakthrough of flow chemistry and catalyzed single phase microreactor technology is expected to take place first in the production of fine and specialty chemicals. For some bulk products (e.g EO), flow chemistry has already arisen interest. The benefits that microreactors can offer are the exact control of process conditions, the compact reactor size and the ease of scalability by simply “numbering up”. For a new product, ease of scalability shortens the time to market, whereas for a bulk product like EO, millireactors (structurally similar to microreactors, just having larger flow channels) may be more potential candidates for on-site production applications.
•Ethylene oxide kinetics was studied.•A kinetic model was developed.•A good description of data was obtained.
Biodiesel is a fuel derived from a renewable vegetable origin and is object of growing interest in recent years both as a pure fuel and as blending component to reduce exhaust pollutants of ...traditional diesel fuel. The conventional biodiesel production technology involves the use of alkaline catalysts and is therefore not compatible with large amounts of free fatty acids (FFAs) and moisture in the feedstock due to the formation of soaps that strongly affect the feasibility of glycerol separation by liquid–liquid splitting. A preliminary stage of acidity reduction is therefore necessary, for this process, if the starting material is characterized by a free acidity higher than 0.5% by weight often contained in cheaper feedstock which lowers the production costs. This can be pursued, for example, by means of an esterification reaction of the FFAs with methanol, catalyzed by ionic-exchange sulphonic acid resins. In the present work, the above-mentioned reaction has been studied in different reactor configurations on a model mixture composed by artificially acidified soybean oil with oleic acid using an acid exchange resin as catalyst. This work has been developed in two parts: (i) a kinetic study in batch conditions with the purpose of developing a suitable kinetic expression and determining the related parameters and (ii) a study of the FFAs esterification in a packed bed tubular reactor operated inside a circulation loop. The kinetic model that is developed on the basis of several batch runs is able to simulate also the behavior of dynamic tubular loop reactor, providing that the external mass transfer resistance is properly accounted for. The mass transfer coefficient is satisfactorily modeled using correlations available on literature.
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► In this paper a tubular reactor packed with different types of fillings has been studied. ► The soybean oil transesterification with methanol (KOH as catalyst) is the tested ...reaction. ► The performances of a tubular reactor filled with stainless steel wool have been determined. ► A simplified kinetic model has been used to interpret the experimental data.
Biodiesel is normally obtained by transesterification of triglycerides with methanol in the presence of an alkaline catalyst. The reaction, performed in stirred tank reactors, requires 1–2h of reaction time. As the reactants are immiscible, the reaction rate can be affected by mass transfer limitation. We have recently shown, that all methods favoring local micromixing can give place to high performances. At this purpose, we have recently developed a very simple laboratory device for testing the behavior of the mentioned reaction in microchannels of different sizes. This device is simply 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 300–1000μm. However, in these reactors the void portion of the reactor is low and the productivity per volume is low, too. 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 this paper, the performances obtained with this type of reactor are reported together with a discussion on the reaction mechanism in view of the future development of a kinetic biphasic model.
The use of nuclear emulsions in very large physics experiments is now possible thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated ...microscopes. In this paper the hardware performances of the
European Scanning System (ESS) are described. The ESS is a very fast automatic system developed for the mass scanning of the emulsions of the OPERA experiment, which requires microscopes with scanning speeds of
∼
20
cm
2
/
h
in an emulsion volume of
44
μ
m
thickness.
Biodiesel is a very attractive biofuel because of its environmental benefits. However, despite its status as a safe substance, the production process can be hazardous because methanol or other ...flammable reactants, such as sodium methylate, can leave plants vulnerable to fire and explosion if not properly engineered and operated. However, further issues are emerging for the increasing capacity of plants, which have driven up on-site volumes of highly hazardous chemicals. Furthermore, some catastrophic accidents have occurred in very recent years in the glycerine neutralization phase. In this paper, insights of risks within this fairly new industry are presented. Heterogeneous catalysis seems to be the promising step for safer biodiesel productions.
The technique of nuclear emulsions for high-energy physics experiments is being revived, thanks to the remarkable progress in measurement automation achieved in the past years. The present paper ...describes the features and performances of the
European Scanning System, a last-generation automatic microscope working at a scanning speed of
20
cm
2
/
h
. The system has been developed in the framework of the OPERA experiment, designed to unambigously detect
ν
μ
→
ν
τ
oscillations in nuclear emulsions.
The kinetics of the steam reforming of methanol have been studied in experimental conditions similar to those used in industrial applications, i.e., by using a commercial catalyst in cylindrical ...pellets. The catalyst used is based on a mixture of Cu–Zn–Al oxides and is normally employed in industry for the low-temperature CO water gas shift reaction. Two kinetic laws have been tested on kinetic runs, performed in a CSTR gradientless Berty reactor and reported in our previous work, by comparing in particular the detrimental effect on the reaction rates of water and/or hydrogen, by comparing in this way the results reported by different authors on this subject. These kinetic laws, together with others reported in the literature, based on different reaction mechanisms, have then been tested for the simulation of runs performed in a tubular pilot-scale packed bed reactor, taking into account for both mass and heat balance along the reactor and inside the catalyst particles. Effectiveness factors were determined through both a rigorous calculation method and experimentally.
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