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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 (D-S) 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. (C) 2015 Elsevier B.V. All rights reserved.

Cardoon seeds oil (Cynara Cardunculus CCO) has been attracting an increasing interest in Italy for the bio-plastic industry. Cardoon is a wild robust perennial plant, native from the Mediterranean basin. The aim of this work is the preparation of biodegradable and non-toxic plasticizers by epoxidation reaction (ECO) of CCO and the study of their potential plasticizing effect in environmentally friendly polymers like poly(lactic acid) (PLA), whose drawbacks are its brittleness and lower impact resistance. The morphological analysis evidenced a well embedding of epoxidized oil inside the polymeric matrix, thus suggesting a good compatibility; the bulk analysis of the systems, by means of DSC and TGA highlighted the decrease of Tg, due to the physical interactions between the polar residues of the polymer and oils in the amorphous region of PLA and higher thermal stability of the polymer in presence of the oils; finally mechanical properties evidenced the enhancement of polymer ductility, particularly in PLA_ECO system.

In this study the physicochemical evolution of soot particles in a laminar premixed flame has been investigated. The evolution of the particle size distribution as function of the different heights above the burner has been explored in conjunction with changes of particle chemical/physical properties retrieved by Raman and Electron Paramagnetic Resonance spectroscopy. In addition, the results obtained by Raman spectroscopy on flame formed soot particles were compared to those obtained by analyzing some standard carbon-based materials such as commercial carbon black, activated carbon, disordered graphite and highly oriented pyrolytic graphite.

The invention relates to bases for paints whose formulation is: - a resin belonging either to the family of MODIFIED ROSIN ESTER RESINS or to the family of MALEIC RESINS; - a solvent consisting of a C9 fatty acid (pelargonic acid) with a purity of 75-95%, esterified with C1 -C10 linear and branched alcohols; - an antioxidant (BHT).

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.

Levulinic acid (LA) has been recognized by the U.S. Department of Energy as one of the top biomass-derived platform molecules, due to its reactivity and because it can be produced at relatively low cost from lignocellulose waste. Levulinic acid esters may find an application as alternative green solvent, polymer plasticizers and fragrances [1]. LA esterification with alcohols is typically acid-catalyzed by homogeneous catalysts (i.e. sulfuric acid, phosphoric acid). Although this approach remains the most frequently utilized, a variety of heterogeneous acid catalysts have been used since recent times (i.e. zeolites, sulfated metal oxides, silica) [2]. Among the catalyst mentioned, Amberlyst-15 showed a remarkable high yield of ethyl levulinate. This behavior is due to the acidity provided by SO3H functional groups. In the present work, the kinetics of the levulinic acid esterification with ethanol in the presence of Amberlyst-15 was investigated. Experiments were performed by varying different operative conditions, i.e. stirring rate, temperature, catalyst loading and reactants ratio. As an example, the effect of temperature is displayed in Figure 1. Figure 1 – Temperature effect on the levulinic acid conversion. Experiments performed at 600 rpm, levulinic acid/ethanol 5:1 mol/mol, 5bar N2, 2.5wt.% Amberlyst-15. The collected experimental data were interpreted with reliable models taking into account both the chemical and mass transfer phenomena involved in the reaction network, such as external and internal mass-transfer limitations. The mixed PDE/DAE systems given by the mass balance equations, Eq. 1 were solved with advanced numerical techniques. (1) The results can be considered as good starting point for the optimization of continuous reactors.

Synthetic associative acrylic monomers functionalized by oxo alcohol based hydrophobic group have been synthetized and then used in “Hydrophobic Alkali Swellable Emulsion (HASE)”. One of the features of use these associative acrylic monomers resides in that once added into the aqueous phase containing a latex and possessing an alkaline nature, they lead to a phenomenon of increased viscosity over a wide range of shearing gradients without adding a neutralization agent. This constitutes a major asset compared to the conventional HASE polymers, which thickened a medium after adding a neutralization agent to it; such an addition has not possible in the emulsion as it has, as it might increase its viscosity to a level that would make it unworkable [1]. Higher thickening efficiency is achieved by the self-associating properties of the attached hydrophobic groups to the polymer backbone. The importance of HASE polymers is due to the great market demand since they are used in a wide range of industrial applications such as viscosizers, paint formulations, cosmetics, cleaning products and coatings paper [2]. The synthesis of the associative monomers has been carried out by an esterification reaction. The reagents used are methacrylic acid, an ethoxylated alcohol and sulfuric acid to catalyze the reaction. Because the properties of the HASE polymers are certainly related to the structure and composition, several associative acrylic monomers can be synthetized changing the ethoxylated alcohol structure (i.e. number of ethoxy groups, length of alkyl chain, linear or branched chain). The characterization of associative monomers has been performed by acid-base titration and IR spectroscopy for structural information. Another aim of the present work, as mentioned above, is to use these associative monomers synthetized in HASE polymers formulation. An example of the polymeric structure is reported in Figure 1. Figure 1 – Molecular structure of a hydrophobically modified alkali-soluble emulsion polymer. x, y, z are structural parameters. n is the number of poly(ethylene oxide). HASE polymers have been synthetized by emulsion polymerization. In particular, have been synthetize HASE with higher molecular weight, low residual solid and with a correct value of polydispersity index. To characterize the HASE polymers have been performed rheological tests to analyze the increasing of viscosity.

Several bio-based polyhydroxyls are successfully synthesized by using succinic acid, obtained via Arundo donax fermentation and characterized by 1H NMR, GPC, and FT-IR analyses. Furthermore, the bio-based polyhydroxyls, consisting of a wide spectrum of compounds in terms of chemical structure and molecular weight, are used as substitute of conventional polyol in the formulations of Polyurethane and random Urethane-Amide Copolymer bio-based foams. The influence of both amount and typology of bio-based polyhydroxyls on bio-based foam properties is investigated through kinetic analysis, thermo-mechanical characterization, and morphological analysis. The results highlight that the replacement of conventional polyol with the bio-based polyester polyhydroxyls affects the foaming process and consequently the final properties of the free-foamed materials. In particular, the compressive modulus increases by about 140% for a bio-based polyhydroxyl content of 50 wt% together with an increase in foam density. A further increase of these adducts results in a decrease of the glass transition temperature and the mechanical performances. However, the experimental results demonstrate the potentiality of these bio-based foams as commodity in several applications.

The activity and stability of niobia supported on silica catalyst have been tested in continuous micro-pilot reactors, for biodiesel production starting from acid vegetable oils. A catalyst was prepared by the impregnation of silica pellets with a loading of 12% of Nb and was extensively characterized. The activity of this catalyst in both esterification and transesterification was tested in a continuous micro-pilot laboratory plant in which acid oil was fed (FFA 10% w/w) at a temperature of 220°C and at a pressure of 60 bar. The niobia based catalyst resulted in a very active catalyst in both esterification (FFA conversion = 95-90%) and transesterification reactions (FAME yield = 80-90%), and the activity remained quite constant for more than 100 h on stream. Notwithstanding this stability, a non-negligible leaching phenomena has been detected, in the case of long-time continuous runs, as the Nb concentration on the spent catalyst resulted lower than that on the fresh one. The obtained result confirms that the leaching of the active specie is one of the most strong problem in heterogeneous catalysis for biodiesel production.

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.

In the present work, a new laboratory device specifically developed to obtain microchannels to test the process intensification effects on a suitable test reaction will be described. Ideally, this device represents a connection between a traditional tubular packed-bed reactor and the recently appeared microreactors that are very efficient, as it is well-known, in mass- and energy-transfer operations. To test the performance of this microreactor, the decomposition of hydrogen peroxide (H2O2) has been chosen as a test reaction. This reaction is of great industrial interest, because many processes use H2O2 as an oxidizing agent and the decomposition of the excess is normally performed under batch conditions by creating an alkaline medium. We observed that the H2O2 decomposition can also be promoted by stainless steel acting as a catalyst. Therefore, the decomposition of H2O2 is particularly enhanced in our device that is characterized by a relatively high surface area of stainless steel per unit of packing volume. Consequently, its result is particularly efficient in the chosen reaction. Experimental runs for H2O2 decomposition have been performed preliminarily under batch conditions, both in the homogeneous phase and in the presence of a known amount of metallic surface area as a catalyst, in the temperature range of 65−85 °C, to collect kinetic data. Successively, continuous runs at different temperatures (50−65 °C) and pH have been performed in the microchannel device, obtaining good performances and maintaining safety conditions. The obtained results have been interpreted and successfully simulated in a simplified way.

The molecular structure characterization of butyl and bromobutyl rubber (BIIR) requires the definition of three main parameters: (I) the unsaturation degree of the rubbers, (II) the total bromine content of the BIIRs, and (III) the functional bromine content of the BIIRs. The analytical methods for the determination of the previously mentioned parameters have been described and critically examined in this review.

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.

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 propene—that is, the classical route—will 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.

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 11 wt% 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.

A kinetic study of the ethanol dehydrogenation to ethyl acetate on a copper/copper-chromite catalyst has been performed. The used catalyst, in cylindrical pellets, contained also alumina as a support and barium chromate as a promoter. Support and promoter have the effect of increasing the activity, the selectivity and the stability of the catalyst, as shown in a previous work. The kinetic runs were carried out in a packed bed tubular reactor, alternatively filled with 2 or 50 g of catalyst, approximately isothermal, by feeding pure ethanol together with a mixture of nitrogen and hydrogen as carrier gas. Kinetic runs have been made by changing the temperature, in the range of 200–260 °C, the pressure between 10 and 30 bar and the space time from 1 to 100 g h mol −1 . We have verified, at first, that inter-phase and intra-phase mass transfer limitations were negligible in the adopted conditions. Then, a Langmuir–Hinshelwood–Hougen–Watson kinetic model has been used for interpreting all the experimental data collected. This model corresponds to a mechanism in which the first step is the dissociative adsorption of ethanol on the surface, giving an adsorbed ethoxy group. Then, two other consecutive steps give place to respectively acetaldehyde as intermediate and ethyl acetate. This kinetic model allows a satisfactory fitting of all the performed experimental runs with a standard error below 15% for the runs performed with 2 g of catalyst and less than 12% for the runs made with 50 g of catalyst.

Propene oxide is a very important chemical whose production technology has changed a lot during the last 30 years. Nowadays, the most promising technology is the HPPO process in which the propene oxide is produced by oxidizing propene with hydrogen peroxide, via titanium silicalite-1 (TS-1) catalysis. Even if this technology has been patented in the early 1980s and some chemical plants are already in production, only few papers have been published until now dealing with the catalytic and kinetic aspects of the process. In this paper, the state of the art of the scientific knowledge and technical aspects related to propene oxide synthesis in the presence of TS-1 catalyst have been reviewed.

In the last decades, bio-derived natural materials, such as vegetable oils, polysaccharides and biomass represent a rich source of hydroxyl precursors for the synthesis of polyols which can be potentially used to synthesize "greener" polyurethane foams. Herein a bio-based precursor (obtained from succinic acid) was used as a partial replacement of conventional polyol to synthesize PU foams. A mixture of conventional and bio-based polyol in presence of catalysts, silicone surfactant and diphenylmethane di-isocyanate (MDI) was expanded in a mold and cured for two hours at room temperature. Experimental results highlighted the suitability of this bio-precursor to be used in the production of flexible PU foams. Furthermore the chemo-physical characterization of the resulting foams show an interesting improvement in thermal stability and elastic modulus with respect to the PU foams produced with conventional polyol.

Scale-up processes are a central feature of chemical engineering science and technology. In this field, researchers’ efforts focus on the development of mathematical models that could be able to interpret physical and chemical phenomena on several dimension scales. Adsorption systems are typical operation units that fall in the mentioned category. In fact, moving from the particle to the fixed bed scale, a further dimension represented by the column axial coordinate is added to the system (and, for larger columns, also the column radial coordinate). In a previous work, an Adsorption Dynamic Intraparticle Model (ADIM) has been proposed and validated by the authors for adsorption batch systems. In the present paper, an attempt to implement the model equations for continuous systems has been made. For validation purposes, an adequate experimental investigation has been obtained by carrying out adsorption experiments both on batch and in continuous devices by using a model system that is represented by aqueous methylene blue over silica. Starting from batch experiments, where some fundamental mass transfer parameters, such as the surface diffusivity (DS), the tortuosity factor (τ) and the mass transfer coefficient (km), have been determined, the ADIM model has been extended to the prediction of the breakthrough curves obtained in continuous system, obtaining good agreements with the collected experimental data. In this way, it has been demonstrated that the ADIM model is a powerful, flexible tool for adsorption modeling over increasing dimension scales.

Biodiesel is a fuel safe, renewable, non-toxic, biodegradable and much less contaminant for the environment than conventional diesel. Moreover, it represents a strategic source of energy especially for the countries that have not oilfields. For these reasons, even if the cost of biodiesel is still greater than diesel from petroleum, many governments sustain this production. The cost of biodiesel is mainly affected by the cost of the feedstock but also an improvement of the adopted technology can contribute in reducing the costs. Therefore, it is imperative: to employ less expensive feedstock, that is, unrefined or waste oils; to use not edible oil coming from alternative sources as, for example, algae or Jathropa Curcas; to improve the actual technology based on the use of homogeneous alkaline catalysts through a better understanding of the reaction mechanism, to develop new biphasic kinetic models; to adopt techniques of process intensification; to introduce the use of heterogeneous catalysts, possibly finding a catalyst promoting in one step both esterification of free fatty acids and transesterification of tri-glycerides; to find new remunerative uses for the by-product glycerol. In this paper, all the mentioned aspects will be considered by reporting some of the most relevant results obtained in the last years.

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 ...

Epoxidized soybean oil (ESBO) is produced in industry by reacting soybean oil, at 60-70 degrees C, with hydrogen peroxide in the presence of formic or acetic acid. A small amount of sulphuric or phosphoric acid is necessary to catalyze the oxidation of the carboxylic acid to the corresponding per-carboxylic acid. Per-carboxylic acid, formed in situ, migrates from the aqueous phase to the oil phase where it spontaneously reacts with the double bonds to give an oxirane ring. This reaction is extremely exothermic (Delta H = -55 kcal/mol) and must be kept under thermal control. Two undesired side reactions can occur: the oxirane ring-opening and the hydrogen peroxide decomposition. In a previous work, a biphasic kinetic model for describing the epoxidation of soybean oil in fed or pulse-fed-batch reactors has been developed and the parameters of the model have been determined by mathematical regression analysis. In the present paper, the model has been adapted to simulate also kinetic runs performed in two continuous tubular reactors of different sizes, filled with spheres of stainless steel (AISI 316) used as static mixer. The agreement found, in simulating the continuous runs, validates the developed biphasic kinetic model. This model constitutes a valid base for the design of a continuous process and for promoting the process intensification.

In this paper, we have studied the KOH catalyzed transesterification reaction of vegetable oil with methanol in a tubular reactor filled with small spheres of stainless steel of different sizes. Three different packed bed configurations have been tested corresponding to different fluid dynamic situations. The first configuration corresponds to the tubular reactor filled with spheres of 2.5 mm of diameters; in the second configuration an opportune amount of spheres of 1 mm has been added to the mentioned spheres of 2.5 mm for filling the void volume of the octahedral cavities between the bigger spheres; in the third configuration an opportune amount of spheres of 0.39 mm has been added to spheres of 2.5 mm for filling the void volume of the tetrahedral cavities between the bigger spheres. The three mentioned configurations give place to the formation of micro-channels with an approximated size of respectively 1000 μm, 500 μm and 300 μm. These systems, subjected to fluid dynamic characterization, have shown a very high local turbulence (static mixer), in particular, when a packed bed reactor with dual size packing is used. Then, kinetic transesterification runs have been made by using the three mentioned packed bed reactors and a very high productivity has been obtained as a consequence of the induced local micro-mixing. A simplified kinetic model has been developed, which is able to describe many runs in batch conditions reported by the literature. This model resulted unsuitable to simulate the continuous runs performed in the described packed bed reactors. Our conclusion is that monophasic models, often proposed in the literature, are not able to describe the kinetic behavior of KOH catalysed transesterification in microchannels devices. At last, the described microchannels device represents, as it will be discussed, an ideal connection between a traditional tubular packed bed reactor and the recently appeared microreactors that are very efficient in mass and energy transfer operations for process intensification.

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. © 2010 American Chemical Society.

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.

The strong growth of biodiesel production occurring in the last years has determined the availability of a great amount of the byproduct glycerol. Many researches in the world are therefore oriented to find new possible uses for glycerol also with the aim of reducing the cost of biodiesel. In this paper the chlorination of glycerol with gaseous hydrochloric acid to obtain 1,3-dichlorohydrin and then epichlorohydrin will be described. All the advantages of this process will be examined and discussed. The behavior of the different proposed catalysts (normally compounds containing carboxylic acid groups), the reaction kinetics, the effect of the catalyst concentration, the effect of HCl pressure, the vapor−liquid phase equilibria of the reaction products in the reaction environment, and the most convenient operative conditions have been studied, concluding with useful suggestions for the design of the industrial plants.

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.

A corrugated plates heat exchanger reactor showing very high productivity in the transesterification of soybean oil with methanol, in the presence of a homogeneous alkaline catalyst (KOH, sodium methoxide), has recently been tested. The reactor is a small size corrugated plates heat exchanger having a low distance between the plates of 1.5-2mm.Asurprising behavior has been observed according towhich the conversion to biodiesel increases by increasing the overall flow rates. This can be explained by examining the fluid dynamic behavior of the systemwith a step test, at different flowrates,made on single-phase liquid fluid. The observed experimental data for the higher flow rates can roughly be approximated to a plug flow behavior despite the very low Reynolds numbers. This is due to the intervention of a very active micromixing. In this reactor the local turbulence favors the mixing of two immiscible liquid reactants approaching, in the case of biodiesel production, the chemical regime. In this work we have shown that by using corrugated plates heat exchanger reactors (CP-HEX reactors) of opportune geometry we can largely intensify the process of biodiesel production. The micromixing intensity in these reactors is very high, favoring the contact between immiscible reagents such as methanol and oil. Therefore, the reactor could generally also be used for other liquid-liquid reactions and more advantageously for very exothermic or endothermic reactions for the great efficiency of the plates exchangers in removing or supplying heat to the reaction interspace.

The aim of the present contribution was to develop a detailed kinetic analysis of the oxidative dehydrogenation (ODH) reaction of methanol to formaldehyde on a nano-structured supported vanadium oxide catalyst, selected in a preliminary screening. The chosen vanadium catalyst, supported on TiO 2 /SiO 2 , has been prepared by grafting vanadyl alkoxide, dissolved in dioxane, and characterized by BET, XRD, Raman, XPS and SEM. An exhaustive set of experimental runs has been conducted in an isothermal packed bed tubular reactor by investigating several operative conditions, such as: temperature, contact time, methanol/oxygen feed molar ratio and water feed concentration. Depending on the operative conditions adopted, the main products observed were formaldehyde and dimethoxymethane while lower amounts of methyl formate and CO 2 were also found. At low contact time, the main reaction product was dimethoxymethane which was then converted into formaldehyde through the reverse equilibrium reaction with water. As a confirmation of this observation, a peculiar behaviour was detected consisting in an increase of selectivity to formaldehyde by increasing methanol conversion. The obtained experimental data of methanol conversion and selectivity towards products were modelled by means of an integral reactor model and the related kinetic parameters were determined by non-linear regression analysis. The adopted reaction rate expressions were of the Mars van Krevelen–Langmuir Hinshelwood type and a good agreement was found between the model theoretical prediction and the experimental data. A reaction mechanism and a detailed reaction scheme ( rake-type ) were proposed for methanol ODH on a nano-structured catalyst that were able to interpret correctly the collected experimental observations.

The growing availability of glycerol, as a consequence of the increase in biodiesel production (for which glycerol is a byproduct), is rapidly saturating the market, and consequently, a great interest is now addressed to the development of new process routes for alternative uses of glycerol. Among the various possibilities, our attention has been focused on the glycerol chlorination reaction, with the aim to produce dichlorohydrin. This compound can then subsequently be converted into epichlorohydrin, which is an important intermediate in the production of epoxy resins. dicholorhydrin, together with R,â-dichlorohydrin, is currently synthesized starting from propylene via allyl chloride. In the present paper, the kinetics of glycerol chlorination with gaseous hydrochloric acid, for the production of dichlorohydrin, has been investigated by means of a jacketed glass reactor operated in batch conditions for the substrate (glycerol) and continuously for the hydrochloric acid. Different organic acids have been tested as catalysts with good performances in terms of both activity and, in particular, selectivity toward the desired 1,3-dichlorinated product. A reaction mechanism has been proposed and a consequent kinetic model has been developed in order to quantitatively describe the experimental data collected at various temperatures (80-120 °C), and the kinetic parameters have been evaluated. A generally good agreement between the experimental data and the theoretical model has been found.

Waste oils used in biodiesel production contain high concentrations of free fatty acids. We studied the esterification of oleic acid, dissolved in soybean oil, with methanol in order to simulate its behavior. We used sulfonic exchange acid resin as the catalyst in two different reactors: a well-stirred slurry reactor (WSSR) and a spray tower loop reactor (STLR) both working at atmospheric pressure. Methanol was fed continuously to both the reactors with very low feed rates in order to minimize the amount of methanol emerging from the reactor outlet. This methanol removed the water produced in the reaction thereby favoring esterification. The WSSR and STLR had very similar performance in that were both better than that of a plug flow reactor (PFR) working in the same conditions of atmospheric pressure and low methanol feed rate. Both the WSSR and STLR showed liquid-solid phase mass transfer limitations. All the kinetic runs have been interpreted with a mathematical model adopting the kinetics previously developed by the authors using a well-stirred batch reactor. For both the reactors, the feasibility of a pseudocontinuous operation has also been successfully tested.

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.

Catalysts that are very active and selective in the oxidative dehydrogenation of ethanol to acetaldehyde have been prepared by grafting vanadyl triisopropoxide onto a silica support whose surface was coated with TiO2. Together with acetaldehyde, small amounts of byproducts were obtained, including acetic acid, acetals, and CO2. The kinetic behaviors of the catalysts were studied in the temperature range 100−180 °C, by changing the ethanol residence time, the molar ratio between the reagents, and the vanadium load. A four-step mechanism was adopted, consisting of the following steps: (i) dissociative adsorption of ethanol onto vanadium, (ii) α-hydrogen withdrawal by the metal to form acetaldehyde and a hydride group, (iii) oxidation of the formed hydride, and (iv) dehydration of the vanadium site to restore the original active site. This mechanism can be simplified, and the resulting kinetic expression is similar to a Mars and van Krevelen kinetic expression. The reaction is well-described by this kinetic...

Polymeric foams are widely used both as structural and as thermal insulating material. Few detailed data about the process of foam growth are reported in the literature, especially for recently developed polyurethane formulations that involve the use of a volatile organic compound instead of the banned chlorofluorocarbons (CFCs). In this work, a dedicated device was realized that allows experimental data collection for polymeric foams growth in terms of temperature and density profiles. For modeling and simulation purposes, a model reported in the literature was modified by improving, in particular, the description of the vapor–liquid phase equilibrium for the system blowing agent/polymer mixture. Simulation of the collected experimental data was performed by this model after the determination of the kinetic parameters for the occurring reaction between polyol and isocyanate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1875–1886, 2004

Following four different procedures many vanadium-based catalysts have been prepared by using the grafting technique and have been tested on the oxidative dehydrogenation of isobutane. The best results of selectivity have been obtained with catalysts prepared by grafting bimetallic vanadium–titanium alkoxides directly on silica. The alkoxide precursors have been obtained by partially hydrolysing titanium alkoxide, dissolved in isopropanol, with a stoichiometric amount of water and reacting then with vanadyl tri-isopropoxide, or alternatively by mixing the two mentioned alkoxides in isopropanol and submitting both to controlled partial hydrolysis. The bimetallic alkoxide grafted on silica show a prevalence of isolated VOTi bonds with respect to polyvanadylic VOV bonds that are prevalent, on the contrary, when vanadyl tri-isopropoxide dissolved in n-hexane is grafted on a TiO2SiO2 support. Catalysts characterised by the prevalence of VOTi bonds are slightly less active but two times more selective than catalysts in which VOV bonds prevail. The preparation of vanadium-based catalysts with a favourable TiO2 environment has been largely simplified by avoiding the use of a TiO2SiO2 support obtaining, in the meantime, a remarkable improvement in the selectivity.

In the present work, vapour–liquid equilibria of four binary systems refrigerant–lubricant oil have been investigated, CF3CHF2 (R125), CF3CH2F (R134a), CF3CH3 (R143a) and CH2F2 (R32) as refrigerants and a commercial perfluoropolyether (PFPE), Fluorolink D10H, as lubricant. Vapour–liquid equilibrium data, consisting of isothermal measurement of equilibrium pressure at a fixed composition, have been correlated with an extended Flory–Huggins equation and the corresponding parameters have been determined. Good agreement has been found between experimental data and the model predictions.

In the present work the partial oxidation of methanol to formaldehyde has been studied as an example of strongly exothermic reaction affected by internal diffusion in order to deep the topic of mass and heat transfer in packed-bed catalytic reactors both at particle level, introducing the calculation of the effectiveness factor for complex reactions network, and at reactor level, for what concerns long range gradients of composition and temperature. The aim of the work is to stress the impact of the use of rigorous numerical methods, today possible for the high performances reached by the computers, in the solution of a simultaneous set of many differential equations that are necessary to describe completely the mentioned system. A complete mathematical model of the particle and the reactor is presented and a solution strategy is reported for the chosen reaction by considering a reliable kinetic law and evaluating related parameters from experimental data reported by the literature. Calculation results are reported for both particle internal profiles and reactor simulation. The described approach can easily be extended to many other devices and reactors geometry such as, e.g., the ones used in the field of environmental catalysis.

A structured unsegregated cybernetic model, able to simulate the growth of baker’s yeast in any possible condition in multistage industrial production has been developed. The model has first been proven in the simulation of the behavior of a laboratory batch bioreactor, describing the evolution with time of the biomass growth rate, the glucose and oxygen consumption as well as the production of ethanol and carbon dioxide. The same model with the same parameters has then been used to simulate both laboratory and industrial size fed-batch bioreactors achieving satisfactory results. The effect of the oxygen mass transfer limitation in fed-batch bioreactors has also been described and discussed. The model developed allows to find and keep the optimal conditions of biomass growth in industrial fed-batch bioreactors.

The hydrogenation of 1,5-cyclo-octadiene has been studied on well-defined Pd catalysts. The reaction is affected by internal diffusion of hydrogen into the catalyst particles. Despite this limitation, the reaction orders of the reactants have been determined. All the performed kinetic runs have been simulated and the kinetic and mass-transfer parameters giving the best fit of experimental data have been evaluated. The reaction occurs in two steps, in the first, a conjugate diene (1,3-cyclo-octene) is formed via isomerization, then, hydrogenation occurs quickly forming the monoene. The hydrogenation of the obtained cyclo-octene is relatively slow and strongly inhibited by the presence of the cyclo-octadiene. This last reaction has, therefore, been used for comparing the activities of different palladium catalysts showing an exponential behaviour of the reaction rate with the metal dispersion.

In the present work, the extended Flory–Huggins equation is applied to describe the vapor–liquid equilibrium in binary mixtures usually used in refrigerating cycle machines and constituted by a fluorinated refrigerant (CFC) and a lubricating oil. With the purpose of testing the model, some isothermal measurements of equilibrium pressure have been carried out for mixtures with different CFC compositions in oil related to the refrigerants R134a, R143a and R236fa mixed with a commercial lubricating oil (Icematic SW32). Furthermore, the model has been applied to experimental data retrieved from the literature, and the adjustable correlation parameters have been determined both for these, and for experimental isotherms.

The kinetic and catalytic aspects involved in the hydrogen peroxide production via anthraquinone (method all-tetra) have been examined considering three of the four main production steps, i.e., hydrogenation of 2-ethyltetrahydroanthraquinone catalyzed by palladium-supported catalysts, oxidation of the product obtained in the first step, and reconversion of the deteriorated molecules for the regeneration of active quinones. For each reaction considered, a mechanism and a kinetic law are suggested with the numerical values of the related parameters.

Some catalysts have been prepared by grafting different amounts of titanium isopropoxide dissolved in toluene on a silica support and by steaming and calcinating the products obtained. A catalyst has been prepared also by first treating with pure sulphuric acid titanium isopropoxide, grafting the titanium alkoxide sulphate on silica and again by steaming and calcinating the product obtained. All the catalysts prepared have been characterized using different techniques such as: electrochemical potentiometric titrations to evaluate the PZC (point of zero charge), the hydroxyl densities and the surface dissociation equilibrium constants; TGA (thermal gravimetric analyses) to evaluate the hydroxyl densities; TPD (thermal programmed desorption) of organic bases such as pyridine and lutidine; and XPS (X-ray photoemission spectroscopy). All catalysts have also been tested by determining the performances in three different reactions: dehydration of methanol, epoxidation of cyclooctene with cumene hydroperoxide and isomerization of 1-butene to 2-butene. The behaviour of the catalysts prepared shows that grafting titanium on silica strongly modifies the original surface and the catalysts obtained with the mentioned grafting techniques are different from those obtained by impregnation and coprecipitation. © 1999 Elsevier Science B.V. All rights reserved.

Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been studied in this work using model molecules such as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB), and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), synthesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. We have observed that a second-order kinetic law is suitable for both condensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst concentration in a different way for each type of catalyst. Bivalent metals activity is affected by the presence of a substituent in the aromatic ring, unlike tri- and tetravalent metals. Suggestions on the reaction mechanisms conclude the work. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2423–2433, 1998

Kinetic and catalytic aspects of DMT transesterification reaction, key step in the industrial production of polyethylenterephtalate (PET), have been deepened also through the use of model molecules such as CH 3 COO–Ph–X. These molecules give the same reactions with ethylene glycol occurring in the DMT transesterification too. The use of model molecules in the study of this reaction seems therefore to be promising in perspective. As we observed, however, the nature of the para-substituent X has a very strong influence on the reaction rate, when salts of bivalent metals such as Zn, Cd, Co, Mg, Mn, are used as catalysts, while this influence is much smaller when a tetravalent metal, as Ti, is used. This fact suggests that the transesterification mechanism operating in the two cases is different and this suggestion has been confirmed by applying Hammett's approach to the available kinetic data. Experimental kinetic runs were all performed at 193°C, by withdrawing small samples of the reaction mixture at different reaction times. These samples were gaschromatographically analyzed. We found volcano shaped curves of the reaction rates as a function of the metal ion acidities and we obtained different trends with a maximum of activity shifted from a metal to another for different substrates. A comparison of the kinetic results obtained, respectively, with the model molecules and DMT will be reported too.