Implementing the flipped classroom methodology to the subject 'applied computing' of two engineering degrees at the University of Barcelona

This work is focused on the implementation, development, documentation, analysis, and assessment of the flipped classroom methodology, by means of the just-in-time teaching strategy, for a pilot group (1 out of 6) in the subject 'Applied Computing' of both the Chemical and Materials Engineering Undergraduate Degrees of the University of Barcelona. Results show that this technique promotes self-learning, autonomy, time management as well as an increase in the effectiveness of classroom hours

Kinetics of the simultaneous syntheses of ethyl tert-butyl ether (ETBE) and butyl tert-butyl ether (BTBE) over AmberlystTM 35

The kinetics of the simultaneous syntheses of ethyl tert-butyl ether (ETBE) and butyl tert-butyl ether (BTBE) over Amberlyst¿ 35 (A35) has been studied at 315-353 K in the liquid phase. Different kinetic modeling approaches¿namely, empirical power-law modeling, mechanistic modeling based on Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER) formalisms, and information-based modeling¿have been compared. Empirical kinetic equations yield optimal quality of the fit, whereas mechanistic equations can explain the mechanisms of the studied reactions. The best mechanistic equation for both reactions corresponds to an ER-type mechanism in which an alcohol molecule (ethanol or 1-butanol) is adsorbed on one active site and reacts with isobutene from solution to produce the corresponding adsorbed ether molecule (ETBE or BTBE), which desorbs. A model built based on previous data has been used to check the validity of the inferred mechanism, while significantly reducing the number of adjustable parameters in the model

Systematic kinetic modeling of the propyl tert-butyl ether synthesis reaction

The kinetics of the liquid-phase addition of 1-propanol to isobutene to produce propyl tert-butyl ether (PTBE) has been studied using the ion-exchange resin Amberlyst¿ 35 as the catalyst. Reaction rates free from mass transfer limitations have been experimentally determined in the temperature range 303-352 K, for different initial proportions of alcohol and isobutene, and using two different reactor types (i.e., a batch stirred tank reactor, to obtain most of the experimental data, and a tubular reactor, to validate those results). To find out the best kinetic model, a systematic approach has been adopted. The overall etherification reaction has been decomposed as the result of elementary steps based on Langmuir-Hinshelwood-Hougen-Watson or Eley-Rideal mechanisms. Candidate kinetic equations have been originated from all possible combinations of adsorbed and non-adsorbed compounds, and rate-determining step. The possible effect of the interaction between the reaction medium and the resin on reaction rates has been also examined. Since all experimental data have been used at once in the fit of the kinetic equations, all combinations of significant or non-significant temperature dependence of model parameters have been also considered. As a result, 1404 candidate kinetic equations have been fitted separately to experimental data. Discrimination among models is based on mathematical and physico-chemical criteria. The final choice of the best kinetic model involves multimodel inference. It corresponds to an Eley-Rideal mechanism where one 1-propanol molecule adsorbed on the catalyst reacts with one isobutene molecule from the liquid phase to form one adsorbed PTBE molecule, the surface reaction being the rate-determining step

Liquid-phase synthesis of butyl tert-butyl ether catalysed by ion-exchange resins: kinetic modelling through in-depth model discrimination

The kinetics of the butyl tert-butyl ether (BTBE) synthesis reaction over Amberlyst¿ 35 as the catalyst has been studied at 303-356 K in the liquid phase in two different reactor systems: batch and fixed-bed. Internal mass transfer effects were detected at temperatures above 333 K for catalyst particles larger than 0.25 mm. Particles smaller than 0.08 mm did not show mass transfer limitations under the whole assayed temperature range. The best kinetic model has been searched among a large number of kinetic equations resulting from the systematic combination of all possible elementary reactions, adsorbed species, and rate-determining step based, according to the Langmuir-Hinshelwood-Hougen-Watson and the Eley-Rideal formalisms. The significance of the temperature effect on the kinetic parameters and of the effect of the interaction between the catalyst and the reaction medium on the reaction rate has been checked. All proposed kinetic equations have been fitted to experimental rate data free from mass transfer limitations. The model discrimination procedure has been based on mathematical and physicochemical criteria. The resulting kinetic model is consistent with an Eley-Rideal type mechanism where one 1-butanol molecule adsorbs on one active site of the catalyst, it reacts with one isobutene molecule from the liquid phase to give one adsorbed BTBE molecule, which finally desorbs. The rate-determining step is the surface reaction. The catalyst activity is affected by the resin-medium interaction. 1-Butanol adsorption on the catalyst is more exothermic than BTBE adsorption, and isobutene adsorption is negligible

Implementación del aula invertida en la asignatura "informática aplicada" del grado de ingeniería química de la Universidad de Barcelona

Este trabajo se centra en la implementación, desarrollo, documentación, análisis y evaluación de la metodología de aula invertida, mediante la estrategia de enseñanza a tiempo, en un grupo piloto (1 de 6) de la asignatura "Informática Aplicada" del grado de Ingeniería Química de la Universidad de Barcelona. Los resultados muestran las bondades de esta técnica en cuanto a la promoción del autoaprendizaje, autonomía, gestión del tiempo así como el mayor aprovechamiento de las horas presenciales

Optimization and Green metrics analysis of the liquid-phase synthesis of sec-butyl levulinate by esterification of levulinic acid with 1-butene over ion-exchange resins

Liquid-phase esterification of levulinic acid (LA) with 1-butene (1B) over ion-exchange resins was studied following an experimental design approach aimed at identifying the optimal conditions to synthesize sec-butyl levulinate (SBL) through the proposed reaction pathway. Experiments were performed in a temperature range of 313-383 K with initial molar ratios of LA to 1B (R°LA/1B) from 0.4 to 3. The optimal experimental conditions determined at 373 K and R°LA/1B = 0.5 render 1B and LA yields to SBL of 48.1% and 76.8%, respectively. Empirical equations relating conditions and yields were obtained, and response surface methodology analysis with subsequent multiobjective optimization allowed identification of optimal conditions to maximize simultaneously the yield of both reactants to SBL¿that is high 1B initial concentration and temperature ranging 360-370 K. According to screening experiments, dense polymer network favors SBL formation. Amberlyst¿15 was the most promising catalyst among the tested ones, since it yields the highest conversion with very low side reactions extension. A green metrics analysis was performed to ascertain the sustainability of the proposed chemical route and to compare it with previously reported studies for the SBL synthesis. Among the scenarios assessed, the proposed chemical pathway represents the greenest alternative

Determination of thermodynamic properties for the esterification of levulinic acid with 1-butene

The thermodynamic equilibrium of the liquid phase esterification of levulinic acid (LA) with 1-butene (1B) to obtain sec-butyl levulinate (SBL) was studied. Equilibrium experiments were performed in a batch reactor at 2.5 MPa in the temperature range of 363-393 K using Amberlyst-15 as the catalyst. The thermodynamic equilibrium for the side reactions (i.e., isomerization of 1B to trans-2-butene, isomerization of trans-2-butene to cis-2-butene, and esterification of LA with these isomers) was also studied. The thermodynamic properties of the reaction were determined experimentally and compared to theoretical estimations and reported literature values. The enthalpy and entropy changes of the esterification reaction with 1B at 298.15 K were estimated to be −(32.9 ± 1.6) kJ/mol and −(70 ± 4) J/(mol·K), respectively. As for the SBL thermodynamic properties, it was found that the liquid phase enthalpy change of formation and entropy at 298.15 K were −(737.1 ± 0.3) kJ/mol and (423 ± 3) J/(mol·K), respectively

Thermodynamic analysis of the experimental equilibria for the liquid-phase etherification of isobutene with C1 to C4 linear primary alcohols

The chemical equilibrium of the liquid-phase syntheses of 2-methoxy-2-methylpropane (MTBE), 2-ethoxy-2-methylpropane (ETBE), 2-methyl-2-propoxypropane (PTBE), and 1-tert-butoxybutane (BTBE) by reaction of isobutene with methanol, ethanol, 1-propanol, and 1-butanol, respectively, has been studied. Four different ion exchange resins as the catalysts, and two different reactor systems, namely, a batch reactor and a setup of tubular reactors, were used. Temperature and pressure were in the range 313-383 K and 1.5-2.0 MPa, respectively. MTBE and ETBE synthesis reactions experiments were carried out mainly to validate the reliability of the reaction systems. Experiments in PTBE and BTBE etherifications allowed estimating thermodynamic properties for those reactions and involved species, namely, molar standard enthalpy and entropy changes of reaction and molar enthalpy change of formation of the four ethers. A comparison of estimated reaction thermodynamic values among the homologous series of linear alcohols, and with results quoted in the literature, when available, has been made

Simultaneous etherification of isobutene with ethanol and 1-butanol over ion-exchange resins

The simultaneous liquid-phase etherification of isobutene with ethanol and 1-butanol to give ethyl tert-butyl ether (ETBE) and butyl tert-butyl ether (BTBE) has been studied, at temperatures in the range of 315-353 K and at 2.5 MPa, over six commercial acidic macroreticular ion-exchange resins as catalysts. The initial alcohol to isobutene molar ratio was varied in the range of 0.5-5.5 and the initial ethanol to 1-butanol molar ratio in the range of 0.5-2.0. Strongly acidic catalysts with a rigid polymer backbone structure enhance reaction rate. This fact, along with the reduced side reactions extent, makes Amberlyst¿ 35 the most promising catalyst, among the tested ones, for the studied simultaneous etherification process. Irrespectively of the used catalyst, initial ETBE synthesis reaction rate is hardly sensitive to the variation of the ethanol to 1‐butanol molar ratio, whereas initial BTBE synthesis reaction rate strongly diminishes at high ethanol concentration. Preferential adsorption of ethanol over 1‐butanol on the catalysts active sites has been detected. As expected, both etherification reaction rates increase at increasing isobutene concentration. At 353 K, the highest temperature, both etherification rates are affected by internal mass transfer resistances due to diffusion limitations even when small catalyst beads are used. The simultaneous process has been compared to the individual syntheses of ETBE and BTBE and it has been found that the isobutene selectivity towards ethers is enhanced in the simultaneous system

Catalytic activity and accessibility of acidic ion-exchange resins in liquid-phase etherification reactions

Although macroreticular acidic ion-exchange resins have been widely used as catalysts in the industrial world for decades, their catalytic behavior is still far from being completely understood at a molecular level. Several characterization techniques coexist, which provide information about their properties. Only few of these techniques give an actual picture of their working-state features when swollen in anhydrous polar reactive media such as in etherification processes, where they are extensively used. The inverse steric exclusion chromatography technique, based on modeling the micropores structure, or gel phase, as a set of discrete volume fractions with a characteristic polymer chain density, constitutes an appropriate procedure to assess the morphology of ion-exchangers in the swollen state. Present work proposes an empirical model to correlate the properties of the volume fractions with their catalytic activity in the etherification reaction rates of isobutene by addition of C1 to C4 linear primary alcohols. Sixteen different macroreticular acidic ion-exchange catalysts, both commercial and lab-made, have been used, which differ in acid capacity, sulfonation type, cross linking degree and swollen-phase volume fractions distribution. Experimental reaction rates have been expressed as a sum of contributions of each individual volume fraction. The contribution of each polymer volume fraction corresponds to the product of the catalyst acidity, the characteristic volume fraction within the gel phase of the catalyst, and a specific turnover frequency (TOF) of that fraction. Accessibility of the reacting alcohol, expressed in terms of the Ogston coefficient, has been also included in the empirical dependency equation presented in this work