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Transesterification of triolein in excess methanol oversodium-loadedcatalysts prepared from Na-ion exchange with zeolites at a relativelylower reaction temperature, namely, at 60 °C, is studied in thiswork. Two zeolites, i.e., as-synthesized ZeoliteMCM-22 and commercial Zeolite HY (CBV-780), are employed in this study.Althoughboth zeolites show to some extent the capability of catalyzing transesterificationof triolein in methanol to biodiesel, the resulting yields are onlyca. 90% for CBV-780 after a 40-h reaction and 16.3% for MCM-22 aftera90-h reaction. In contrast, the conversion yields are much improvedwith Na-ion exchange to the surface of zeolite catalysts. For example,the yields of triolein to biodiesel have reached 98% and 99% withina 5.5-h reaction, respectively, using the NaOH-treated CBV-780 andMCM-22 catalysts, even if these NaOH-treated catalysts become amorphousand have suffered a loss of the Brunauer–Emmett–Tellersurface area. Furthermore, no saponification was observed using theseNaOH-treated catalysts. [ABSTRACT FROM AUTHOR]

Previous studies have shown that hybrid fermentation–pervaporationsystems can be attractive for ethanol production. Simultaneous removalof the ethanol produced promises to improve yield and to reduce operationtime and the energy required for ethanol purification. This paperexperimentally explores the effect of pH (3–5.7), CO2(at saturated conditions), and high glucose concentrations (50–400g/L) on the flux and selectivity of PDMS (polydimethylsiloxane) pervaporationmembranes at several ethanol concentrations (50–100 g/L) andtemperatures (278–313 K). Membrane performance has been simulatedusing a Henry solution model combined with a Maxwell–Stefandescription of mass transport through the membrane. By adjusting themodel to the water–ethanol experimental data, it was possibleto calculate the relative solubility and diffusion between ethanoland water in the polymeric membrane. Experimental results showed thatthe higher the glucose concentration is, the higher the membrane selectivityto ethanol will be due to a reduction on water flux. However, at aglucose concentration of 400 g/L a strong drop of total flux was measured.CO2permeates through the PDMS membrane, but it does nothave any effect on ethanol or water flux and, consequently, on selectivity.On the contrary, as pH is reduced so does selectivity while the totalflux increases. Low pH values produce a decrease in membrane hydrophobicity,increasing water transport. The results presented in this paper contributeto the design of hybrid fermentation and pervaporation units, especiallythose that can operate at high glucose concentrations. [ABSTRACT FROM AUTHOR]

In this study, kinetics of formic acid-catalyzed xylosedehydrationinto furfural and furfural decomposition was investigated using batchexperiments within a temperature range of 130–200 °C.Initial xylose and furfural concentrations up to 0.2 and 0.08 mol/L,respectively, were used. The room temperature pH of the formic acidcatalyst solution was between 0.9 and 1.7. The kinetic model usedwas based on a specific acid catalysis model and included the prevailinghydrogen ion concentration in reaction conditions. The study showedthat the modeling must account for other reactions for xylose besidesdehydration into furfural. Moreover, the reactions between xyloseintermediate and furfural play only a minor role. The study also showedthat kinetic modeling of xylose and furfural decomposition reactionsmust take the uncatalyzed reaction in water solvent into account. [ABSTRACT FROM AUTHOR]

Thin and narrow conductive patterns of metal (silver)and organicpolymer (polyaniline) were printed on various coated paper samples.A detailed characterization of the physical properties (i.e., shortlength scale roughness, surface energy, and air permeability) of thepaper samples was conducted. These properties were correlated withprint quality (print resolution and edge waviness) and electricalperformance (resistance) of the printed wires. A plastic film wasused as a reference substrate. The print resolution and the magnitudeof the edge waviness were affected by the complex interplay of differentphysical properties of both the substrate and the ink. On the otherhand, the resistance of the printed wires was found to correlate linearlywith the short length scale roughness of the print substrate. Theelectrical performance of the paper substrates showing the highestconductivity for the printed patterns was comparable to that of theplastic film. The paper substrate on which the printed wires showedthe best electrical performance was used as a substrate for fabricationof an organic transistor with low operating voltage. [ABSTRACT FROM AUTHOR]

Generalized least-squares and maximum likelihood approaches for parameter estimation in multivariate response models have been prevalent in the chemical kinetics literature to date. In contrast, robust alternatives have received considerably less attention. These methods safeguard against possible deviations from the assumptions, such as the presence of outliers or non-normality of the random errors. We compare, through Monte Carlo simulation, the performance of the classical Box–Draper determinant criterion (ML) to those of two robust estimators: the multivariate Huber’s M-estimator and the multivariate least-trimmed squares estimator (MLTS). Although the results are not entirely conclusive, overall, we find no compelling evidence for preferring any one of the two robust methods over the conventional ML estimates. At the same time, it was unexpected to find that ML is still reasonable under mild outlier contamination and mild deviations from normality. This notwithstanding, one loses nothing by comparing ML together with MLTS to cross-check each other as a safety measure. [ABSTRACT FROM AUTHOR]

A simulation study of a C4 oxosynthesis plant (gas recycle technology) was performed by using the software package Hysys. The process thermodynamics was described by UNIQUAC property model. An important drawback of this technology is a significant loss of propylene by the purge gas stream. Computer simulations were carried out to evaluate the technical performance and the investment cost of a proposed revamping scheme, allowing an advanced propylene recovery from purge gases. The cost evaluations performed with Aspen Economic Evaluation are indicating that the revamping investment cost is equivalent to the propylene savings during a three years plant running period. [ABSTRACT FROM AUTHOR]

Lavandin (Lavandula hybrida) essential oil contains components with biocide and antiviral properties that can be used as substitutes for synthetic drugs in livestock. This application requires an appropriate formulation of the essential oil. Liposomes are promising drug carriers, because they can enhance the skin penetration of drugs, deliver the entrapped drugs across cell membranes, and improve essential oil stability and bioavailability. In this work, the incorporation of lavandin essential oil in liposomes produced with commercially available lecithins and cholesterol has been studied. Two different liposome production methods have been tested: a modification of the Bangham thin-film method and the particles from gas-saturated solutions (PGSS) drying process. Liposomes obtained with the thin-film method were multivesicular or unilamellar/multilamellar with a mean diameter of 0.4−1.3 μm and an efficiency of incorporation of essential oil of up to 66%. The liposomes were stable for at least 1 month. On the other hand, by application of the PGSS process, dry and fine but aggregated soy lecithin particles were produced, with a particle size in the range 1.4−24.8 μm and a poor efficiency of incorporation of essential oil ranging from 3% to 14.5%. These particles could be dispersed in water, producing liposomes whose size ranged between 0.5 and 1.5 μm [ABSTRACT FROM AUTHOR]

Microparticles of ampicillin have been precipitated by a supercritical antisolvent process (SAS) using carbon dioxide and N-methylpyrrolidone as the antisolvent and solvent, respectively. The mean particle size (PS) and particle size distribution (PSD) of the processed antibiotic were chosen as responses to evaluate the process performance. The levels for a screening design of experiments were chosen to allow the process to take place in a single supercritical phase. Under these conditions, all of the experiments led to the successful precipitation of ampicillin. Concentration was a key factor as this had the most marked effect on both PS and PSD. [ABSTRACT FROM AUTHOR]

A combined exhaust gas aftertreatment system, consisting of a diesel oxidation catalyst (DOC), an NOxstorage and reduction catalyst (NSRC, which also is called lean NOxtrap, LNT), and a catalyst for selective catalytic reduction of NOxby NH3(NH3-SCR) is studied experimentally. The catalyst samples are placed in series in an almost isothermal laboratory minireactor. Dynamic behavior of the system is examined under periodic lean/rich operation in temperature range of 200−400 °C with varying composition of the rich mixture, containing CO, H2and C3H6. Concentrations of gas components are measured at the inlet, outlet, and between the individual catalysts. The individual DOC, NSRC, SCR, NSRC−SCR, and DOC−NSRC subsystems are also examined. The DOC is used as the first element in the exhaust aftertreatment line. It is responsible for the oxidation of CO and unburned hydrocarbons (HC), and it also supports the oxidation of NO to NO2. NSRC and SCR converters are employed for the abatement of nitrogen oxides. A significant amount of NH3can be formed in the NSRC as a byproduct of the NOxreduction, depending on the regeneration phase length, temperature, and gas composition. The generated ammonia is adsorbed in the SCR and used for additional NOxreduction. The dynamics of the combined system is investigated, and the conversions, selectivities, and reaction mechanisms in each converter, as well as mutual synergic and competitive effects, are discussed. [ABSTRACT FROM AUTHOR]

The aim of this work was the removal of diacetin, monoacetin,andglycerol from biodiesel–triacetin mixtures using liquid–liquidextraction with water. Liquid–liquid equilibrium was predictedusing UNIFAC based models for the activity coefficient calculations.These data have been corroborated with experimental information fromall possible binary, ternary (water, triacetin, and biodiesel), andoverall (diacetin, monoacetin, glycerol, water, triacetin, and biodiesel)mixtures. The experimental determination of the diacetin, monoacetin,and glycerol distribution factor and their selectivity with respectto triacetin allows the operating temperature set at 27.5 °C.After that, it was determined that three washing steps, with a waterto feed mixture mass ratio of 0.05 (per stage), were necessary forthe effective elimination of these compounds. The final compositionof the raffinate phase was 94.6 wt % biodiesel and 5.1 wt % triacetin.The extract phase consisted of a mixture of 59.2 wt % acetins andglycerol and 40.7 wt % water. [ABSTRACT FROM AUTHOR]

Chemical interesterification of triglycerides with methylacetateyields biodiesel and triacetin. This reaction is highly reversible,which implies the presence of intermediate compounds such as diacetinmonoglycerides.In addition, the use of methanolic potassium methoxide as the catalystcauses the appearance of diacetin, monoacetin, and glycerol. Vacuumdistillation becomes an interesting alternative for the separationof biodiesel and triacetin. Vapor–liquid equilibrium (VLE)determination requires information related to the vapor pressuresof the different compounds and the nonideality of the liquid phase(activity coefficients). The lack of literature information for somecompounds was supplemented with experimental data and predictive modelsfor vapor pressure and activity coefficients (UNIFAC and UNIFAC Dortmund).The suitability of using vacuum distillation was evaluated using theFenske equation and experimental results from a structured packeddistillation column. According to the results, removal of diacetinmonoglyceridescan be easily accomplished, unlike the elimination of diacetin, monoacetin,and glycerol, which form azeotropes with triacetin. [ABSTRACT FROM AUTHOR]

The pyrolysis of a chromium-tanned waste (bovine splitleather)under inert atmosphere has been carried out in a vertical lab scalereactor. The influence of process conditions, such as temperature,residence time, and heating rate on the pyrolytic product distributionhas been studied, in order to optimize the liquid fraction obtained.Flash pyrolysis at three different temperatures (450, 500, and 550°C) and slow pyrolysis up to 750 °C have been performed.Results indicate that, in the range of low temperatures, the productdistribution is slightly dependent on temperature. In general, a reductionof the heating rate or residence time favors the presence of heavygases (i.e., more than four carbon atoms hydrocarbons). The analysisof the pyrolytic liquid shows a wide spectrum of products (mainlynitrogenated and oxygenated compounds and phenols) which can be usefulas a source of chemicals. A comparison between the results reachedin the pyrolysis of tanned leather and a commercial collagen allowsus to study the effect of the tanning process. According to the resultobtained, the tanned leather produces more nitrogenated compoundsand phenols and less ketones and linear hydrocarbons than pure collagen.A very good agreement between the evolution of pyrolytic gases producedin a slow pyrolysis and the weight loss of the solid measured by thermogravimetricanalysis has been observed. [ABSTRACT FROM AUTHOR]

A novel method for the degradation of tributyl phosphate was investigated through the use of nanopowders of iron and iron–nickel. A combination of magnetic field and sonication was used to induce degradation. Using a tributyl phosphate concentration of 300 ppm at pH 4, the Fenton reaction was initiated in the presence of sonication and a reduction in organic carbon content of up to 50% could be created under an induced magnetic field of 0.7 T. The magnetic properties of powders after sonication treatment, in the presence and absence of a magnetic field, were observed to be different. Different degradation mechanisms were proposed under the influence of varying induced magnetic field for iron and iron–nickel. [ABSTRACT FROM AUTHOR]

In this study, the phase behavior of an asymmetric system consisting of the refrigerant, trifluoromethane, and 1-phenyltetradecane, a lubricant from the family of alkylbenzenes, is investigated. Equilibrium data were obtained using a synthetic method in the temperature range 253.34−370 K and pressures up to12 MPa. The investigated system exhibits type III phase behavior, according to the classification of van Konynenburg and Scott. The new experimental data were modeled with two cubic equations-of-state, Soave−Redlich−Kwong (SRK) and Peng−Robinson (PR), and were coupled with classical van der Waals mixing rules. A single set of binary parameters was used to predict the global phase behavior of the system for a large range of pressure and temperature. Although the model is simple, it is able to represent correctly the complex phase equilibria of the system studied in this work. [ABSTRACT FROM AUTHOR]

In this work, the removal of a β-blocker, atenolol,and a pesticide, isoproturon, from aqueous solutions by adsorptionon granular activated carbon fixed-bed columns has been studied. Theeffect of important operation parameters on breakthrough curves ascolumn length (Z= 1.0–3.0 cm), initial concentrationof atenolol or isoproturon (C0= 50.0–500.0μg·L–1), and volumetric flow rate (Q= 1.5 mL·min–1) was studied. Breakthroughtime of the bed was found to increase with an increase in the valueof the column length, and with a decrease in the value of initialconcentration or flow rate. Mathematical models, as Bohart–Adams,Thomas, Yoon–Nelson, and Clark were applied to the experimentaldata for the prediction of the breakthrough curves, and to determinethe characteristic parameters of the bed. [ABSTRACT FROM AUTHOR]

A copper C2-symmetric bis(oxazoline), CuBox, was introduced in two forms of commercial Y zeolite: a sodium form (NaY) and an ultrastable form (NaUSY). CuBox was introduced by first partially exchanging the sodium cations of both zeolites for copper and then by refluxing the obtained materials with a solution of bis(oxazoline) (Box). Two different loadings were prepared for each form of zeolite. The materials were characterized by copper ICP-AES, elemental analysis, XPS, FTIR, TG, and nitrogen adsorption isotherms at −196 °C. Evidence for Box ligand location in the supercages of NaY and NaUSY zeolites and its coordination to the exchanged copper(II) was obtained by the several techniques used. The materials were all active in the cyclopropanation of styrene with ethyldiazoacetate at room temperature and diastereoselective toward transcyclopropanes. Although the materials containing Box showed low enantioselectivities, their catalytic activities were higher than the parent copper exchanged zeolites, and did not decrease with reuse, at least during three consecutive cycles. [ABSTRACT FROM AUTHOR]

The objective of this work is to study, for the first time, the photodegradation of 4-chlorophenol (4CP) catalyzed by a calcined Mg–Zn–Al layered double hydroxides (MgAlZn LDHs) in a co-current downflow bubble column (CDBC) photoreactor at pilot scale. The effect of initial organic compound concentration (C4CP0), temperature (T), and mass catalyst over reaction rate (−r4CP) was elucidated. An intrinsic kinetic regime was established, and a single-site Langmuir–Hinshelwood mechanism was determined to occur during the organic compound oxidation. The catalyst was characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), and ultraviolet–visible light (UV/vis) spectrophotometry. The reaction progress was verified by UV/vis spectrophotometry and total organic carbon (TOC) content. Degradation and mineralization rate were found to be dependent on Tand 4CP concentration. In the range of studied operating conditions, a maximum of 94% 4CP was degraded, while 70% total organic carbon removal was achieved. [ABSTRACT FROM AUTHOR]

Ethanol may be used in diesel−ethanol mixtures in order to decrease soot emissions. Therefore, it is important to evaluate the contribution of ethanol to soot formation. The influence of the temperature on the pyrolysis of ethanol under sooting conditions has been studied. Pyrolysis experiments were carried out in a quartz reactor in the 700−1200 °C temperature range, for an inlet C2H5OH concentration of 50 000 ppm and a gas residence time in seconds of 1706/(T/K) . The concentrations of the gases analyzed in the experiments are shown in this work together with simulations carried out with a literature kinetic model. Theoretical and experimental results present, generally, a good agreement in spite of the model not taking into account the soot formation. Under the studied conditions, soot formation has been observed above 1050 °C. With the soot samples obtained, a study of their reactivity toward O2and NO has been carried out, and several characterization techniques, such as elemental analysis, Brunauer−Emmett−Teller (BET) surface area, transmission electron microscopy, and X-ray diffraction have been used to study the structural properties of the collected soot samples and relate them to their reactivity. It has been observed that the soot samples formed at higher temperatures exhibit a lower reactivity toward O2and NO, and the characterization analyses support these results. [ABSTRACT FROM AUTHOR]

Biosorption of lead(II) ions from aqueous solutions by untreated, HCl-treated, H2SO4-treated, HNO3-treated, and H3PO4-treated olive stone was studied in a continuous-upflow packed-bed column. The effect of acid treatment on the lead biosorption capacity of olive stone was determined by evaluating the breakthrough curves obtained at different inlet concentrations of lead, changing from 10 to 150 mg/L. Results indicated that the treatment of olive stone with inorganic acids improves significantly its capacity to removal lead ions from aqueous solution. Finally, the Adams−Bohart, Thomas, Yoon and Nelson, and dose−response models were used to analyze the experimental data to determine the characteristic parameters of the column useful for process design. In particular, the dose−response model was able to simulate breakthrough curves at lower and higher time periods with high correlation coefficients. The maximum column biosorption capacity predicted by this model at an inlet lead concentration of 150 mg/L was 1.31 mg/g for unmodified olive stone and 14.03 mg/g for olive stone treated by H2SO4. Also, the pH variations during the sorption process have been reported. [ABSTRACT FROM AUTHOR]

A useful encapsulation methodology has been developed to fabricate α-tocopheryl acetate-zeolite Y microcapsules. These new microcapsules have been applied to obtain special textile polyamide fibers. The presence of α-tocopheryl acetate in both microcapsules and special fibers has been qualitatively and quantitatively determined using various techniques such as thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC). Two different techniques to extract the α-tocopheryl acetate encapsulated in both microcapsules and special fibers have been compared: liquid−liquid extraction, that gives the best results under the studied conditions, and supercritical CO2extraction, which is useful when there are mass transfer limitations as in the case of the special fibers. Mechanical properties of the fiber do not significantly change when they are fabricated with zeolite Y microcapsules. Finally, fabrics knitted with yarns of α-tocopheryl acetate-zeolite Y microcapsules state a significant presence of the additive after 100 washing machine cycles (30 °C, neutral soap). [ABSTRACT FROM AUTHOR]